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1. 290 10 11 12 13 14 15 Do not rely on ASCII and English sorting rules Locale specific collation should be performed with strcoll and strxfm These are table driven functions the tables are supplied as part of locale support See Collating Strings on page 306 for more information Use the localeconv function to find out about general details of numeric formatting Use strfmon to format currency amounts in particular See Specifying Numbers and Money on page 307 for more information Use strftime to format dates and times strftime gives a host of options for displaying locale specific dates and times See Formatting Dates and Times on page 309 for more information Avoid arithmetic on character values Use the macros in ctype h to get information about a given character These macros are table driven and locale sensitive If you prefer you can use the functions that correspond to these macros instead Character Classification and ctype on page 309 provides more detailed information on these macros and functions If you do your own regular expression parsing and matching use the XPG 4 extensions to traditional regular expression syntax for internationalized software See Regular Expressions on page 311 for more information Where possible use the XPG 4 rather than the MNLS interface in order to maximize portability See Strings and Message Catalogs on page 32
2. Program finished Leave group and exit pvm pyvm_lvgroup foo pvm_exit exit 1 Simpl xample passes a token around a ring void dowork int me int nproc int token int src dest int count 1 int stride 1 int msgtag 4 Determine neighbors in the ring src pvm_gettid foo me 1 dest pvm_gettid foo metl if me 0 src pvm_gettid foo NPROC 1 if me NPROC 1 dest pvm_gettid foo 0 if me 0 token dest pvm_initsend PvmDataDefault pyvm_pkint amp token count stride pvm_send dest msgtag printf token ring begun value sent d n token pvm_recv src msgtag pvm_upkint amp token count stride printf token ring done value recvd d n token else pvm_recv src msgtag pvm_upkint amp token count stride pvm_initsend PvmDataDefault pvm_pkint amp token count stride pvm_send dest msgtag Example Programs SPMD Program in MPI Version SPMD example using MPI a illustrating porting from PVM to MPI Ay include lt stdio h gt include lt sys types h gt include lt mpi h gt void dowork int me int nproc main int argc char argv int mytid my task id int ntasks total number of tasks int i Initialize MPI MPI_Init amp argc amp argv Get our task id our rank in the basic group MPI_Comm_rank MPI_COMM_WORLD amp myti
3. When you download a font this way the warning message exitserver permanent state may be changed is sent to the file usr spool lp log on the system to which the printer is attached The permanent state of the printer is not really changed Downloaded fonts disappear when you reset the printer by switching its power off and on If there is not enough memory for additional fonts you receive a message about a Virtual Memory VM error and the font is not downloaded If you again send the program that produces a list of available fonts to your printer you should see the PostScript names of the fonts you downloaded on that list 281 PART SIX Internationalizing Your Application Chapter 14 Internationalizing Your Application Documents how to prepare an application to execute in more than one language environment including the use of character sets and locale specific behaviors Chapter 14 Internationalizing Your Application Internationalization is the process of generalizing an application so that it can easily be customized or localized to run in more than one language environment You can provide internationalized software that will produce output in a user s native language format data such as currency values and dates according to local standards and tailor software to a specific culture This chapter describes how to create such an application It contains the following major s
4. XOpenIM finds the IM appropriate for the current locale If XSupportsLocale has returned good status see Initialization for Xlib Programming and XOpenIM fails something is amiss with the administration of the system XSetLocaleModifiers determines configure locale modifiers The local host X locale modifiers announcer the XMODIFIERS environment variable is appended to the modifier list to provide default values on the locale host The modifier list argument is a null terminated string containing zero or more concatenated expressions of this form category value For example if you want to connect Input Method Server xwnmo set modifiers _XWNMO as follows XSetLocaleModifiers im _XWNMO Or set environment variable XMODIFIERS to the string im _xwWNMo and execute XSetLocaleModifiers Note The library routines are not prepared for the possibility of XSupportsLocale succeeding and XOpenIM failing so it s up to application developers to deal with such an eventuality This circumstance could occur for example if the IM died after XSupportsLocale was called This topic is under some debate in the MIT X consortium If XSetLocaleModifiers is wrong XOpenIM will fail User Input Most of the complexity associated with IM use comes from configuring an input context to work with the IM Input contexts are discussed in Input Contexts ICs on page 352 To close an input method call
5. int lockWholeFile int fd int tries int limit tries tries MAX_TRY int try lseek fd 0L SEEK_SET set start of lock range for try 0 try lt limit try if 0 lockf fd F_TLOCK OL break mission accomplished if errno EAGAIN break mission impossible sginap 1 let lock holder run return errno The following points should be noted about Example 7 3 e The type of lock is not specified because lockf only supports exclusive locks e The operation code F_LTLOCK specifies that the function should return if the lock cannot be placed The F_LLOCK operation would request that the function suspend until the lock could be placed e The start of the record is set implicitly by the current file position That is why Iseek is called to ensure the correct file position before lockf is called Whole File Lock With flock Example 7 4 displays a third example of the lockWholeFile subroutine this one using flock Using Record Locking Example 7 4 Setting a Whole File Lock With flock define _BSD_COMPAT include lt sys file h gt includes fentl h include lt errno h gt for EAGAIN define MAX_TRY 10 int lockWholeFile int fd int tries int limit tries tries MAX_TRY int try for try 0 try lt limit try if 0 flock fd LOCK_EX LOCK_NB break mission accomplished i
6. Function Name Purpose and Operation setitimer 2 Set the expiration and repeat interval of a timer getitimer 2 Return the current value of a timer Each process has three itimers available to it as summarized in Table 5 11 Table 5 11 Types of itimer Kind of itimer Interval Measured Resolution Signal Sent ITIMER_REAL Elapsed clock time 1 millisecond or less SIGALRM ITIMER_VIRTUAL User time process 1 second SIGVTALRM execution time ITIMER_PROF User system time 1 second SIGPROF The ITIMER_VIRTUAL and ITIMER_PROF have a relatively coarse precision Their intervals vary depending on when and how often the process is dispatched The ITIMER_REAL timer is comparable to the POSIX time base CLOCK_SGI_FAST In order to use an itimer you establish a signal handler for the appropriate signal as shown in Table 5 11 then issue the setitimer call The principal argument to this function is a struct itimerval an object containing two incremental time values The it_value field specifies the time until the timer should expire The it_interval field when nonzero gives the time that should be loaded into the timer after it expires Tip One excellent reason not to mix BSD and POSIX timer support in the same program is that the POSIX struct itimerspec used to set a POSIX timer and the BSD struct itermval used to set a BSD itimer have fields with identical names but these fields have different data types and precisions 125
7. The plock function does not lock mapped segments you create with MAP_SHARED You must lock them individually using mpin You need to do this from only one of the processes that shares the segment Locking Mapped Segments It may be better for your program to not lock the entire address space but to lock only a particular mapped segment Immediately after calling mmap you have the address and length of the mapped segment This is a convenient time to call either mpin Q or mlock to lock the mapped segment The mmap flags MAP_AUTOGROW and MAP_AUTORESRV are unique to IRIX and not defined by POSIX However the POSIX mlock function for IRIX does recognize autogrow segments If you lock an autogrow segment with mpin mlock or mlockall with the MCL_FUTURE flag additional pages are locked as they are added to the segment If you lock the segment with mlockall with the MCL_CURRENT flag the segment is locked for its current size only and added pages are not locked Locking Mapped Files If you map a file before you use mlockall MCL_CURRENT or plock to lock the data segment into memory see Mapping a File for I O on page 15 the mapped file is read into the locked pages during the lock operation If you lock the program with mlockall MCL_FUTURE and then map a file into memory the mapped file is read into memory and the pages locked If you map a file after locking the data segment with plock or mlockall MCL_
8. 100 perror semop else perror semget Using the Examples The following commands demonstrate the use of the example programs First a semaphore set is created by semget and its existence verified with ipcs ipcs s IPC status from dev kmem as of Wed Jun 19 11 19 37 1996 eli ID KEY Semaphores semget k Oxfab c x p 0666 s 4 semid 130 owner uid gid 1110 20 creator uid gid ipcs s MODE OWNER IPC status from dev kmem as of Wed Jun 19 11 19 59 1996 T ID KEY MODE OWNER Semaphores s 130 0x00000fab ra ra ra cortesi The effect of the IPC_EXCL flag is tested semget k Oxfab c x semget File exists The permissions are changed using semmod semmod i 130 p 0640 owner uid gid 1110 20 creator uid gid ipcs s IPC status from dev kmem as of Wed Jun 19 11 20 09 1996 L ID KEY MODE OWNER Semaphores s 130 0x00000fab ra r cortesi GROUP 1110 20 GROUP user 1110420 GROUP user mode mode 0100666 nsems 4 0100640 nsems 4 System V Facilities for Mutual Exclusion The present state of the four semaphores in the set is displayed then semop is used to increment the first two semsnap i 130 vals 0 0 0 0 nent e0 0O 0 0 Zents OO 0 0 semop i 130 v 0 v 1 semsnap i 130 vals 1 2 0 0 nent 0O 0O 0 0 Zente 03 0 20 20 One instance of semop is started in the background to
9. Chapter 5 Signalling Events 126 You can use setitimer for any of three operations e With it_value nonzero and it_interval zero initiate a one time interval e With it_value nonzero and it_interval nonzero initiate a repeating timer e With it_value zero disarm the timer preventing it from expiring if it has not expired already Hardware Cycle Counter All current Silicon Graphics systems have a hardware cycle counter a free running binary counter that is incremented at a high regular frequency You can use the cycle counter as a high precision timestamp The precision of the cycle counter is different in different system types for example it is a 24 bit counter in the Indy workstation but a 64 bit counter in Challenge and Onyx systems The rate at which the timer increments is its resolution and this also varies with the hardware type The cycle counter is an addressable hardware device that you can map into the address space of your process see Mapping Physical Memory on page 19 When this is done you can sample the cycle counter as if it were a program variable The code to do this mapping is discussed in the syssgi 2 reference page under SGI_QUERY_CYCLECNTR However the use of the hardware cycle counter has been integrated into the POSIX timer support beginning in IRIX 6 2 and this makes access to the cycle counter much simpler than before e Inorder to sample the cycle counter call clock_gett
10. How Resolution Affects Font Size The images on most output devices such as laser printers and video monitors are created by coloring a rectangular array of small dots or pixels picture elements The number of dots or pixels that can be drawn per unit of length in a horizontal direction is called the horizontal resolution while the number of pixels that can be drawn per unit of length ina vertical direction is called the vertical resolution The most commonly used unit of measure for resolution is the number of dots per inch dpi Resolution is a device dependent unit of measure To display the resolution of your video monitor enter this command xdpyinfo grep resol You should get a response similar to this resolution 93x93 dots per inch The first number is the horizontal resolution the second the vertical resolution If you draw a single character at a given resolution the bounding box of the character is the smallest rectangle that enclose that character If you display all of the characters in a font in the same place without advancing you get a composite image of those characters If you then draw the smallest rectangle that encloses that composite image you have the bounding box for the font The size of a font is usually measured in the vertical direction That size is usually not smaller than the height of the font bounding box but it can be greater than that height It may include additional vertical spacing that
11. if 1 msqid no id given try key msqid msgget key 0 if 1 msqid const time_t tm time NULL char stime 26 void ctime_r amp tm stime format timestamp for msg stime 24 0 drop annoying n 153 Chapter 6 Message Queues 154 for c 1 c lt count c msg gt type type sprintf msg gt text S05d s c stime if 1 msgsnd msqid msg bytes msgf1gq perror msgsnd break else perror msgget Example of msgrcv The program msgrcv in Example 6 8 allows you to receive messages from a specified queue The following arguments are used in more than one program k key Numeric identifier of a message queue for example k 99 i id Message queue ID alternative to specifying the key for example i 80 c count Number of messages to attempt to receive b bytes Maximum size of a message for example b 0x200 n Use the IPC_NOWAIT flag with msgrcv e Use the MSG_NOERROR flag with msgrev to truncate messages longer than bytes q Be quiet do not display the received message Use for performance testing As each message is received it is displayed A sequence number and the message type are always displayed the first 32 bytes of the text are displayed if it begins with ASCII Example 6 8 Program to Demonstrate msgrcv Program to test msgrcv 2 I msgrcv k lt key gt i lt id gt t lt type gt b
12. theSproc gt next sprocList put self on the list sprocList theSproc usunsetlock sprocListLock release sprochist usvsema readySprocs notify master at least 1 on the list uspsema theSproc gt sprocWait sleep until master posts me Body of a general purpose child process The argument which must be declared void to match the sproc prototype is the oneSproc structure that represents this process The contents of that 203 Chapter 10 Process Level Parallelism 204 struct in particular sprocWait are initialized by the parent void childBody void theSprocAsVoid struct oneSproc mySproc struct oneSproc theSprocAsVoid here one could establish signal handlers etc for sprocSleep mySproc wait for work to do mySproc gt calledFunc mySproc gt callArg do the work if mySproc gt sprocDone if a completion sema is given usvsema mySproc gt sprocDone post it Acquire a oneSproc structure from the ready list waiting if necessary Called by the master process as part of dispatching a sproc xf struct oneSproc getSproc struct oneSproc theSproc uspsema readySprocs wait until at least 1 sproc is free usset lock sprocListLock acquire exclusive rights to sprocList theSproc sprochist get address of first free oneSproc sprocList theSproc g
13. Chapter 8 Models of Parallel Computation Parallel Hardware Models 180 Silicon Graphics makes a variety of systems The Indy and Indigo workstations have single CPUs Although they can perform I O operations in parallel with computing they can execute only one stream of instructions at a time and time share the CPU across all active processes The Challenge and Onyx systems and their POWER versions are symmetric multiprocessor SMP computers In these systems at least 2 and as many as 36 identical microprocessors access a single common memory and a common set of peripherals through a high speed bus The POWER CHALLENGEarray comprises 2 or more POWER CHALLENGE systems connected by a high speed local HIPPI network Each node in the array is an SMP with 2 to 36 CPUs Nodes do not share a common memory communication between programs in different nodes passes through sockets However the entire array can be administered and programmed as a single entity Most programs have a single thread of execution that runs as if it were in a uniprocessor employing the facilities of a single CPU The IRIX operating system applies CPUs to different programs in order to maximize system throughput Parallel Hardware Models You can write a program so that it makes use of more than one CPU at a time The software interface that you use for this is the parallel programming model The IRIX operating system gives you a variety of such
14. Example 6 4 Program to Demonstrate mq_receive Program to test mq receive 3 mq_receive c lt count gt n q lt path gt i i c lt count gt number of messages to request default 1 n use O_NONBLOCK flag on open POSIX Message Queues q quiet do not display messages lt path gt path to message queue required The program calls mq_receive lt count gt times or until an error occurs EJ include lt mqueue h gt message queue stuff include lt unistd h gt for getopt include lt errno h gt errno and perror include lt fcntl h gt O_RDONLY include lt stdlib h gt calloc 3 include lt stdio h gt int main int argc char argv char path gt first non option argument int oflags O_RDONLY open flags O_NONBLOCK may be added int quiet 0 q option int count 1 number of messages to request mqd_t mqd queue descriptor from mgq_open char msgptr gt allocated message space unsigned int msg_prio received message priority int c ret struct mq_attr obuf output of mq_getattr mq_msgsize while 1 c getopt argc argv c nq switch c case c count count strtoul optarg NULL 0 break case q quiet quiet 1 break case n nonblock oflags O_NONBLOCK break default unknown or missing argument
15. One difference between MNLS and XPG 4 catalog functions is that the MNLS catalog can be used from commands and hence it can be used to internationalize a shell script The following table summarizes MNLS functions that have both a command line and a function library version gettxt 1 Retrieve a string from the catalog Ifmt 1 Retrieve a format string insert arguments display to stderr and to system log or textport pfmt 1 Retrieve a format string insert arguments display to stderr Strings and Message Catalogs Specifying MNLS Catalogs MNLS message catalogs do not need to be specifically opened The catalog of choice can be set explicitly once or it can be specified every time a string is needed To specify the default message catalog to be used by subsequent calls to MNLS functions that reference catalogs use setcat include lt pfmt h gt char setcat const char catalog catalog is limited to 14 characters and may contain no character equal to zero or to the ASCII codes for slash or colon See the setcat 3 reference page setcat doesn t check to see if the catalog name is valid it just stores the string for future reference For an example of use see the following topic The catalog indicated by the string must be found in the directory usr lib locale localename LC_MESSAGES Getting Strings From MNLS Message Catalogs MNLS message catalogs do not need to be specifically opened The catalog
16. Overview of Locale Specific Behavior This section covers e Local Customs e Regular Expressions e The ANSI X3 159 198X Standard for C Local Customs To meet the requirements of local customs the X Open Native Language System NLS interface provides a set of library functions that allow cultural data appropriate to the user to be determined at run time Regular Expressions Regular expressions provide pattern matching facilities for text A variety of regular expression support libraries are supplied with IRIX Most of them parse regular expressions in terms of machine collating sequences the English language and the ASCII coded character set When a program deals with internationalized input text it is important to extend regular expression facilities to cover internationalized strings and coded character sets It is difficult to write regular expressions that apply to more than one language or to languages with accented multi character collating elements because of limitations in syntax Application programs can use the wsregexp function library documented in the wsregexp 3W reference page to support internationalized regular expression behavior The ANSI X3 159 198X Standard for C The American National Standards Committee X3J11 standard for the C programming language includes a number of library functions that are defined to operate internationally that is they modify their operation in a manner appr
17. Similarly you should also eliminate all calls to pym_addhosts pym_delhosts and pvm_config Finally if the program has a pym_halt call remove it also 245 Chapter 12 Distributed Process Parallelism 246 MPMD Model In an MPMD programming model one or more distinct tasks having different executables are started by hand and these tasks dynamically spawn other possibly distinct tasks The initial setup change required for this model is similar to the one required for the general SPMD model discussed in the previous section that discussion applies here too The main difference here is that the task executables are different programs and this information is encapsulated in the hostfile procgroup file in the MPI paradigm The initial MPI environment setup thus consists of figuring out the number of instances of each distinct executable that constitute the parallel job and using the total as the static initial number for the MPI environment Again you must remove all the pym_spawn pvm_config pym_addhosts pym_delhosts and pym_halt calls in each PVM executable Common Environment Setup Changes For all the three models you must remove from the program being ported all calls that query the library for virtual machine or tasks information such as pym_mstat pvm_pstat and pym_tasks Handle any semantic dependency to these calls in the program other than initial environment setup in the resulting MPI p
18. Table 7 1 Functions for File and Record Locking Function Name Purpose and Operation fentl 2 fentl 5 General function for modifying an open file descriptor can be used to set file and record locks lockf 3C lockf 3F Library function to set and remove file and record locks on open files SVR4 compatible flock 3B Library function to set and remove file and record locks on open files BSD compatible chmod 1 chmod 2 Command and system function that can enable mandatory file locking on a specified file Terminology The discussion of file and record locking depends on the terms defined in this section Record A record is any contiguous sequence of bytes in a file The UNIX operating system does not impose any record structure on files The boundaries of records are defined by the programs that use the files Within a single file a record as defined by one process can overlap partially or completely on a record as defined by some other process Overview of File and Record Locking Read Shared Lock A read lock keeps a record from changing while one or more processes read the data If a process holds a read lock it may assume that no other process can alter that record at the same time A read lock is also a shared lock because more than one process can place a read lock on the same record or on a record that overlaps a read locked record No process however can have a write lock that overlaps a read lock Wri
19. Use the functions sched_get_priority_max and sched_get_priority_min to get the ranges of priority numbers you can use Use sched_setparam to change priorities POSIX dispatching priorities are nondegrading Note that in a program that links with the pthreads library these same function names are library functions that return thread scheduling priority numbers unrelated to process scheduling Tip The POSIX scheduling priority values reported by these functions and declared in sched h are not numerically the same as the bands supported by schedctl and declared in sys schedctl h The POSIX numbers are numerically higher for superior priority However the POSIX range is functionally but not numerically equivalent to the normal range supported by schedctl NDPNORMMAX to NDPNORMMIN POSIX scheduling uses one of two scheduling policies strict FIFO and round robin which are described in detail in the sched_setscheduler 2 reference page The round robin scheduler which rotates processes of equal priority on a time slice basis is the default You can query the time slice interval with sched_get_rr_interval You can change the policy and the priority both using sched_setscheduler Using Multiple Processes Self Dispatching Processes Often each child process has a particular role to play in the application and the function that you name to sproc represents that work The child process stays in that function until it t
20. X11R6 includes text rendering routines that understand multibyte and wide character strings These routines are analogous to the X11R4 text rendering routines XDrawText XDrawString and XDrawImageString The old routines continue to operate but do not take fontsets and don t know how to handle characters longer than one byte e XmbDrawText and XwcDrawText take lists of TextItems each of which contains among other things a string The strings are rendered using fontsets These routines allow complex spacing and fontset shifts between strings e XmbDrawString and XwcDrawString render a string using a fontset These routines render in foreground only and use the raster operation from the current graphics context e XmbDrawImageString and XwcDrawImageString also render a string using a fontset These routines fill the background rectangle of the entire string with the background then render the string in the foreground color ignoring the currently active raster operation Consult the appropriate reference pages for more details on these routines New Text Extents Functions X11R6 provides MB and WC versions of width and extents interrogation routines supplying the maximum amount of space required to draw any character in a given fontset These routines depend on fontsets to interpret strings and use locale specific data The XFontSetExtents structure contains the two kinds of extents a string can have typedef stru
21. if msglen lt 32 msglen 32 break Case tetu Jr count 7 count strtoul optarg NULL 0 if count gt 99999 count 95999 break case n use nonblock oflags O_NONBLOCK break default unknown or missing argument return 1 if optind lt argc path argv optind first non option argument else 139 Chapter 6 Message Queues 140 printf Queue pathname required n return 1 msgptr calloc 1 msglen mqd mq_open path oflags if 1 mqd char stime 26 const time_t tm time NULL current time value void ctime_r amp tm stime formatted time string stime 24 0O drop annoying n for c 1 c lt count c sprintf msgptr 05d s c stime if mq_send mqd msgptr msglen msg_prio perror mq_send break else perror mq_open O_WRONLY Example of mq_receive The mq_receive program in Example 6 4 allows you to receive and display messages from a queue These command line arguments are accepted path The file pathname of the queue must be given following all options c count Number of messages to send The default is 1 q Tells program not to display a line for each message received n Use the O_NONBLOCK flag with mq_open You can use the q option to keep the program from displaying messages Do this when receiving a large number of messages for example to test performance
22. mmap NULL size mprot mflags shm fd off_t 0 if attach mmap worked 49 Chapter 3 Sharing Memory Between Processes printf Attached at 0x lx first word 0x lx n attach pid_t attach if mprot amp PROT_WRITE pidt attach getpid printf Set first word to 0x lx n pid_t attach if wopt wait a while char inp 80 printf Press return to detach gets inp printf First word is now 0x 1lx n pid_t attach if munmap attach size perror munmap else perror mmap else perror shm_open return errno IRIX Shared Memory Arenas 50 The shared memory arena is basic to all IRIX IPC mechanisms IRIX semaphores locks and barriers are all represented as objects within a shared arena Overview of Shared Arenas A shared arena is a segment of memory that can be made part of the address space of more than one process Each shared arena is associated with a disk file that acts as a backing store for the file see Page Validation on page 9 Each process that wants to share access to the arena does so by specifying the file pathname of the file The file pathname acts as the public name of the memory segment The file access permissions determine which user IDs and group IDs can share the file IRIX Shared Memory Arenas The functions you use to manage a shared arena are discussed in the following topic
23. return 1 if optind lt argc path argv optind first non option argument else printf Queue pathname required n return 1 mqd mq_open path oflags if 1 mqd 141 Chapter 6 Message Queues 142 if mq_getattr mqd amp obuf get max message size msgptr calloc 1 obuf mq_msgsize for c 1 c lt count c ret mq_receive mqd msgptr obuf mq_msgsize amp msg_prio if ret gt 0 got a message if quiet if isascii msgptr printf Sd priority ld len d text 32 32s n c msg_prio ret msgptr else printf d priority ld len d nonascii n c msg_prio ret else an error on receive stop perror mq_receive break for c lt count if getattr else perror mq_getattr return 1 if open else perror mq_open O_WRONLY System V Message Queues System V Message Queues IRIX contains an implementation of message queues compatible with UNIX System V Release 4 SVR4 These message queue functions are demonstrated in example programs in this section Managing SVR4 Message Queues The functions used to create and control SVR4 message queues are summarized in Table 6 4 Table 6 4 SVR4 Functions for Managing Message Queues Function Name Purpose and Operation msgget 2 Create a message queue if it does not exist and gain access to it msgc
24. similar interfaces The examples below arbitrarily use XmbLookupString but apply to both versions There are two new situations to deal with 1 The string returned may be long 2 There may be an interesting keysym returned an interesting set of characters returned both or neither Dealing with the former is a matter of maintaining an arena as in Example 14 13 To tell the application what to pay attention to for a given event XmbLookupString returns a status value in a passed parameter equal to one of the following XLookupKeysym Indicates that the keysym should be checked XLookupChars Indicates that a string has been typed or composed XLookupBoth Means both of the above XLookupNone Means neither is ready for processing XBufferOverflow Means the supplied buffer is too small call XmbLookupString again with a bigger buffer XmbLookupString also returns the length of the string in question Note that XmbLookupString returns the length of the string in bytes while XwcLookupString returns the length of the string in characters The example below should help show how these functions work Most event processors perform a switch on the event type assume you have done that and have received a KeyPress event 357 Chapter 14 Internationalizing Your Application Example 14 1 case eysym tatus tatic K S ait s static i if buflength first if We switch cas
25. using ls l You can dump its contents with a command such as od X You can remove it with rm Shared Object Open Flags The flags you pass to shm_open control its actions as follows O_RDONLY Access can be used only for reading O_RDWR Access can be read write however you can enforce read only access when calling mmap O_CREAT If the object does not exist create it O_TRUNC If the object does exist and O_RDWR is specified truncate it to zero length O_EXCL If the object does exist and O_CREAT is specified return the EEXIST error code The flags have the same meaning when opening a disk file with open However a number of other flags allowed by open are not relevant to shared memory objects You can use the combination O_CREAT O_EXCL to ensure that only one process initializes a shared object Shared Object Access Mode The access mode that you specify when creating an object governs the users and groups that can open the object later exactly as with a disk file Using the Shared Object File Descriptor The value returned by shm_open is a file descriptor and you can use it as such for example you can apply the dup function to make a copy of it You can also use it as an argument to fentl but most of the features of fentl are irrelevant to a shared memory object See the dup 2 and fentl 2 reference pages POSIX Shared Memory Operations Using a Shared Object In order to use a shared object
26. 1 switch c case k key key key_t break case i l i msgid in break case p p perms str break case b b bytes str break case Tu u uid break strtoul op d t strtoul op ermissions toul optarg ytes toul optarg id targ targ ceived msg queue id for any of these l c getopt argc argv K i b p u g NULL 0 NULL 0 strtoul optarg NULL 0 System V Message Queues case g gid gid strtoul optarg NULL 0 break default unknown or missing argument return 1 if 1 msqid no id given try key msqid msgget key 0 if 1 msqid if 1 msgctl msqid IPC_STAT amp buf if perms 1L bytes 1L uid 11L gid 1L put new values in buf fields as requested if perms 1L buf msg_perm mode mode_t perms if uid 1L buf msg_perm uid uid_t uid if gid 1L buf msg_perm gid gid_t gid if bytes 1L buf msg_qbytes ulong_t bytes if 1 msgct1 msqid IPC_SET amp buf perror nmsgct1 IPC_SET printf owner d d perms 040 max bytes d n buf msg_perm uid buf msg_perm gid buf msg_perm mode buf msg_qbytes printf Sd msgs d bytes on queue n buf msg_qnum buf msg_cbytes else perror nmsg
27. 134 The sigevent_t structure allows you to specify either a signal or a callback function However only the signal notification SIGEV_SIGNAL request is supported by the POSIX message queue implementation Example Programs The following programs demonstrate the use of POSIX message queues e Example 6 1 on page 135 demonstrates the use of mq_getattr to query the attributes of a queue e Example 6 2 on page 136 demonstrates the use of mq_open to create or access a message queue e Example 6 3 on page 138 demonstrates the use of mq_send to put messages onto a message queue e Example 6 4 on page 140 demonstrates the use of mq_receive to take messages from a message queue The four example programs have a consistent design and use consistent command line arguments Each accepts optional arguments that allow you to exercise most features of each function including most error return codes The following is a simple example of use First a queue is created mq_open p 0664 b 128 m 32 c x var tmp Q32x128 flags 0x0 maxmsg 32 msgsize 128 curmsgs 0 An attempt is made to send a message that is larger than the queue maximum size mq_send b 129 var tmp Q32x128 mq_send Inappropriate message buffer length A message of appropriate size is sent Its presence on the queue is verified using mq_getattr mq_send b 128 p 7 var tmp Q32x128 mgq_attr var tmp Q32x128 flags 0x0 maxmsg 32 msgsize 128
28. 51 Table 3 4 IRIX Shared Memory Arena Allocation Functions 54 Table 3 5 IRIX Shared Memory First Datum Functions 55 Table 3 6 SVR4 Shared Memory Functions 60 Table 3 7 SVR4 Shared Segment Management Operations 61 Table 4 1 POSIX Functions to Manage Unnamed Semaphores 73 Table 4 2 POSIX Functions to Manage Named Semaphores 74 Table 4 3 POSIX Functions to Operate on Semaphores 76 Table 4 4 IRIX Functions to Manage Nonpolled Semaphores 77 Table 4 5 IRIX IPC Functions for Managing Polled Semaphores 78 Table 4 6 IRIX IPC Functions for Semaphore Operations 79 Table 4 7 IRIX IPC Functions for Managing Locks 80 Table 4 8 IRIX IPC Functions for Using Locks 81 Table 4 9 IRIX IPC Functions for Barriers 82 Table 4 10 Compiler Intrinsics for Atomic Operations 85 Table 4 11 SVR4 Semaphore Management Functions 87 Table 4 12 SVR4 Semaphore Set Management Operations 88 Table 4 13 SVR4 Semaphore Management Operations 89 XXV List of Tables xxvi Table 5 1 Table 5 2 Table 5 3 Table 5 4 Table 5 5 Table 5 6 Table 5 7 Table 5 8 Table 5 9 Table 5 10 Table 5 11 Table 6 1 Table 6 2 Table 6 3 Table 6 4 Table 6 5 Table 7 1 Table 8 1 Table 9 1 Table 9 2 Table 10 1 Table 10 2 Table 10 3 Table 10 4 Table 11 1 Table 11 2 Table 11 3 Table 11 4 Table 11 5 Table 11 6 Table 11 7 Table 11 8 Table 11 9 Signal Numbers and Default Actions 105 Signal Handling Interfaces 107 Functions for POSIX Signal Handling 111 Functions for SVR4 Si
29. ASCII and ISO 8859 and MB characters use less space than do wide characters However manipulating individual characters within a multibyte string is difficult Note Traditional strings are merely a special case of multibyte strings where every character happens to be one byte long and there is only one codeset All MB code including conversion to and from wchars works for traditional ASCII or ISO 8859 strings e Applications that do heavy string manipulation typically use WC strings for such activity because manipulating individual WC characters in a string is much simpler than doing the same thing with MB characters So wide characters are used as necessary to provide programming ease or runtime speed however they take up more space than MB characters Note WC is system dependent applications should not use it for I O strings or communication Multibyte Characters A multibyte character is a series of bytes The character itself contains information on how many bytes long it is Multibyte characters are referenced as strings and are therefore of type char before parsing a string is indistinguishable from a multibyte character The zero byte is still used as a string and MB character terminator A string of MB characters can be considered a null terminated array of bytes exactly like a traditional string A multibyte string may contain characters from multiple codesets Usually this is done by incorporating special byte
30. IPC objects are often created and never removed In these cases they persist until the system is rebooted or until they are removed manually Using System V IPC You can list all the components of the IPC name space using the ipcs command You can remove an object with the ipcrm command If you remove an object that is in use unpredictable results will follow Access Permissions IPC objects are not part of any filesystem but access to IPC objects is controlled by rules like the rules that govern file access For example if the access permissions of a shared memory segment are set to 640 the segment can be read write for processes that have the same UID as the segment owner but the segment is read only to processes that have only the GID of the owner and is not accessible to other processes Choosing and Communicating Key Values The name of an IPC object is an integer Two small problems are how a program can select a unique key to use when making an IPC object and how to communicate the key to all the processes that need access to the object The ftok library function can be used to create a predictable key based on a file pathname For example unrelated but cooperating programs can agree to use ftok with a designated project file and project code so that each program will arrive at the same key Using ID Numbers When an IPC object is created it has the key it is given by the creating process but it is also assign
31. RI lek i_start lck 1l_len if lck l_len 0 break this lock goes to end of file stop lck l_start lck l_len fentl with the F_GETLK command always returns correctly that is it will not sleep or fail if the values passed to it as arguments are valid 170 Using Record Locking The lockf function with the F_TEST command can also be used to test if there is a process blocking a lock This function does not however return the information about where the lock actually is and which process owns the lock Example 7 8 shows a code fragment that uses lockf to test for a lock on a file Example 7 8 Testing for Contending Lock Using lockf find a blocked record seek to beginning of file void lseek fd 0 OL set the size of the test region to zero to test until the end of the file address space if lockf fd F_TEST OL lt 0 switch errno case EACCES case EAGAIN void printf file is locked by another process n break case EBADF bad argument passed to lockf perror lockf break default void printf lockf unknown error lt d gt n errno break When a process forks the child receives a copy of the file descriptors that the parent has opened The parent and child also share a common file pointer for each file If the parent seeks to a point in the file the child s file pointer is also set to that location Similarly whe
32. There are at least 32 priority values and the lowest is greater than or equal to 0 You can use these functions to set up a system of relative priorities as suggested by the code in Example 11 4 Example 11 4 Establishing Relative Priority Levels include lt sched h gt int higherP mediumP lowerP void setRelativePriorities int maxP minP maxP sched_get_priority_max j minP sched_get_priority_min mediumP minP maxP minP 2 higherP mediumP 1 lowerP mediumP 1 When all threads use one of the three priorities higherP mediumP or lowerP threads that run at higherP will always run in preference to threads at the other two priorities Scheduling Pthreads Note There are system functions named sched_get_priority_max and sched_get_priority_min they are documented in Controlling Scheduling With POSIX Functions on page 202 and the sched_get_priority_max 2 reference page However when you link with libpthread these names are defined in the pthread library and access the pthread priority values A thread can set another s priority or scheduling policy or both using pthread_setschedparam A simple function to set a specified priority on the current thread returning the previous value is shown in Example 11 5 Example 11 5 Function to Set Own Priority include lt sched h gt struct sched_param int setMyPriority int newP pthread_t myTid pthread_self int ret
33. c lt count gt n lt path gt p lt priority gt priority code to use default 0 b lt bytes gt size of the message default 64 min 32 c lt count gt number of messages to send default 1 max 9999 9 lt n use O_NONBLOCK flag in open lt path gt path to queue required The program sends lt count gt messages of lt bytes gt each at lt priority gt POSIX Message Queues Each message is an ASCII string containing the time and date and a serial number 1 lt count gt The minimum message is 32 bytes Kf include lt mqueue h gt message queue stuff include lt unistd h gt for getopt include lt errno h gt errno and perror include lt time h gt time 2 and ctime_r 3 include lt fcntl h gt O_WRONLY include lt stdlib h gt calloc 3 include lt stdio h gt int main int argc char argv char path gt first non option argument int oflags O_WRONLY open flags O_NONBLOCK may be added mqd_t mqd queue descriptor from mq_open unsigned int msg_prio 0 message priority to use size_t msglen 64 message size int count 1 number of messages to send char msgptr gt allocated message space Ine y whil gt 1 c getopt argc argv p b c n switch c case p priority msg_prio strtoul optarg NULL 0 break case b bytes msglen strtoul optarg NULL 0
34. id msqid int strtoul optarg NULL 0 break case t typ can be negative type strtol optarg NULL 0 break case b bytes no minimum bytes strtoul optarg NULL 0 break case c count no maximum count strtoul optarg NULL 0 break case n nowait msgflg IPC_NOWAIT 155 Chapter 6 Message Queues break case e noerror allow truncation of msgs msgflg MSG_NOERROR break case q quiet quiet 1 break default unknown or missing argument return 1 if 1 msqid no id given try key msqid msgget key 0 msg struct msgspace calloc 1 sizeof long bytes if 1 msqid for c 1 c lt count c int ret msgrcv msqid msg bytes type msgflg if ret gt 0 got a message if quiet if isascii msg gt text 0 printf Sd type ld len d text 32 32s n ome msg gt type ret msg gt text else printf Sd type ld len d nonascii n Cy msg gt type ret else an error end loop perror msgrcv break for c lt count good msgget else perror msgget 156 Chapter 7 File and Record Locking IRIX supports the ability to place a lock upon an entire file or upon a range of bytes within a file Programs must cooperate in respecting record locks A file lock can be made mandatory but only at a cost in performance
35. receive synchronously sigwaitinfo 2 sigtimedwait 2 Itis important to not mix these signal facilities Your program should use functions from only one column of Table 5 2 otherwise unexpected results can occur Signal Blocking and Signal Masks Certain ideas are basic to the use of signals One basic idea is that a program can block the delivery of any signal When a signal that is sent to a program is blocked the signal is queued and remains pending until the program unblocks the signal or terminates Certain urgent signals SIGKILL SIGSTOP SIGCONT cannot be blocked 107 Chapter 5 Signalling Events 108 You specify which signals are blocked using a signal mask a set of bits in which each bit corresponds to one signal number When a bit in the mask is set on the signal is blocked if it is a signal that can be blocked Each process has a signal mask inherited from its parent process All three interfaces provide ways to set and clear bits in the current signal mask The BSD interface however only lets you mask the first 32 signal numbers listed in Table 5 1 Each POSIX thread has a signal mask also A multithreaded program defined as a program that is linked with libpthread so it uses the pthreads version of the standard library must use the POSIX interface for signal handling Multiple Signals In most cases if a signal of a certain number is pending for a process and another signal of the same number arr
36. see the Programmer s Guide for the language for system functions for this purpose Managing Statement Parallel Execution Choosing the Loop Schedule Type Most parallel sections are loops The benefit of parallelization is that some iterations of the loop are executed in one CPU concurrent with other iterations of the same loop in other CPUs But how are the different iterations distributed across processes The languages support four possible methods of scheduling loop iterations as summarized in Table 9 2 Table 9 2 Loop Scheduling Types Schedule Purpose SIMPLE Each process executes LN P iterations starting at Q LN P First process to finish takes the remainder chunk if any DYNAMIC Each process executes C iterations of the loop starting with the next undone chunk unit returning for another chunk until none are left undone INTERLEAVE Each process executes C iterations at C Q C 2Q C 3Q GSS Each process executes chunks of decreasing size N 2P N 4P The variables used in Table 9 2 are as follows N Number of iterations in the loop determined from the source or at run time P Number of available processes set by default or by environment variable see Controlling the Degree of Parallelism on page 192 Q Number of a process from 0 to N 1 C Chunk size set by directive or by environment variable 193 Chapter 9 Statement Level Parallelism 194 The effects of the sched
37. unsigned long imEventMask XGetWindowAttributes dpy win amp winAtts XGetICValues ic XNFilterEvents amp imEventMask NULL imEventMask winAtts your_event_mask XSelectInput dpy window imEventMask XSetICFocus ic At this point the window is ready to be used Events Under IM Control Processing events under input method control is almost the same in X11R6 as it was under R4 and before There are two essential differences the XFilterEvent and X LookupString routines Using XFilterEvent Every event received by your application should be fed to the IM via XFilterEvent which returns a value telling you whether or not to disregard the event IMs asks you to disregard the event if they have extracted the data and plan on giving it to you later possibly in some other form All events not just KeyPress and KeyRelease events go to XFilterEvent If you compacted the event processing into a single routine a typical event loop would look something like the code in Example 14 12 Example 14 12 Event Loop Xevent event while TRUE XNextEvent dpy amp event if XFilterEvent amp event None continue DealWithEvent amp event User Input Using XLookupString XwcLookupString and XmbLookupString When using an input method you should replace calls to XLookupString with calls to XwcLookupString or XmbLookupString The MB and WC versions have very
38. uscasinfo 3 Change the shared pointer field using a compare and swap Note The precision of the usgetinfo field in an arena 32 or 64 bits depends on the execution model of the program that creates the arena This is one reason that processes compiled to different models cannot share one arena Often the parent process creates and initializes the arena before it creates any of the child processes that will share the arena In this case you expect no race conditions The parent can set the shared pointer using usputinfo because no other process is using the arena at that time Each child process can fetch the value with usgetinfo 55 Chapter 3 Sharing Memory Between Processes 56 The purpose of uscasinfo is to change the contents of the field in an atomic fashion avoiding any race condition between concurrent processes in a multiprocessor All three functions are discussed in detail in the usputinfo 3P reference page Tip The data type of the shared pointer field is void a 64 bit value when the program is compiled to the 64 bit model If you need to cast the value to an integer use the type __psint_t a pointer sized integer in any model In the less common case when an arena is shared by unrelated processes each process that calls usinit might be the first one to create the arena or might not If the calling process is the first it should initialize the basic contents and set the shared pointer If it is not
39. 11 of the Xlib Programming Manual Volume One Looking carefully at that code may be easier than starting from scratch GL Input The old GL function qdevice has a hard coded view of a keyboard see usr include gl device h for details Some flexibility particularly for Europe is available if you queue KEYBD instead of individual keys but the GL has no general solution to non ASCII input There is no supported way to input Chinese for instance to the old GL OpenGL does not contain input code but leaves that to the operating environment which in IRIX means X In short support for internationalized input means a departure from qread Under IRIX that means using mixed model input all the more reason to use a toolkit About X Keyboard Support This section provides some background that may help make the following sections easier to understand User Input Keys Keycodes and Keysyms When a client connects to the X server the server announces its range of keycodes and exports a table of keysyms Each key event the client receives has a single byte keycode which directly represents a physical key and a single byte state which represents currently engaged modifier keys such as Shift or Alt Note The mapping of state bits to modifiers is done by another table acquired from the server Keysyms are well defined and there has been an attempt to have a keysym for every engraving one might possibly find on any keyboard an
40. 39 Argentina country code 367 ASCII strings See internationalization codesets ASCII Australia country code 367 Austria country code 367 backing store 6 9 12 30 barriers allocating 82 Belgium country code 367 Brazil country code 367 brk 6 7 BSD and IPC 36 Cc cache address mapping in Challenge Onyx 28 effect of miss 27 management 27 29 multiprocessor conflicts 28 cache line 27 calloc 9 catalogs See message catalogs 371 Index Challenge Onyx architecture cache address mapping 28 cache management in 27 PIO error latency 20 character sets See internationalization character sets Chile country code 367 China country code 367 chkconfig command 8 chmod command 18 C local value 296 codes country 367 codesets See internationalization codesets Colombia country code 367 conventions syntax xxxi country codes 367 370 Courier font 265 ctype character classification 309 D data segment locking 24 deadlocks 172 Denmark country code 368 dev mem 19 dev mmem 20 dev ome 20 dev zero and mmap 15 19 DSO text segment for 4 372 E editres 361 Egypt country code 368 empty strings 294 encodings See internationalization encodings EUC encoding Chinese 339 German 339 Japanese 338 F file mapping into memory 15 25 file access permissions and mmap 17 file and record locking 176 across systems 174 deadlocks 172 e
41. 567 89 Kr10 234 567 89 Switzerland SFr10 234 567 89 SFr10 234 567 89C Using printf printf function detailed in the printf 3S reference page examines LC_NUMERIC and chooses the appropriate decimal radix If none is available it tries to use ASCII period No further locale specific formatting is done directly by printf However see Variably Ordered Referencing of printf Arguments for a way to handle locale specific ordering of syntactic elements in messages Using localeconv The localeconv function detailed in the localeconv 3C reference page can be called to find out about numeric formatting data including the decimal radix inappropriately called decimal_point the grouping separator inappropriately called thousands_sep the grouping rules and a great deal of monetary formatting information The localeconv function leaves actual use of formatting information other than the decimal radix to the application Cultural Items Using strfmon The strfmon function detailed in the strfmon 3S reference page is new with IRIX version 6 2 Like sprintf strfmon takes an output area a format string that contains conversion specifications and one or more argument values to be converted It creates an output string containing fixed data and converted values Only two conversion types are supported i to convert a double value to international currency representation and n to convert a double valu
42. Barriers Function Name Purpose and Operation new_barrier 3P Allocate and initialize a barrier in a specified arena free_barrier 3P Release the storage associated with a barrier barrier 3P Wait at a barrier until a specified number of processes have gathered init_barrier 3P Reinitialize a barrier does not release any processes waiting The main process uses new_barrier to allocate a barrier in some arena To use the barrier each process calls barrier passing the number of processes that are supposed to meet before proceeding Note The barrier function assumes that it is used on a multiprocessor It always passes time by spinning in an empty loop When used on a uniprocessor or when used on a multiprocessor with fewer available CPUs than barrier processes a call to barrier n can be quite inefficient The waiting functions spin until each in turn uses up its time slice In general it is not a good idea to use barrier except in a multiprocessor with a number of CPUs approximately equal to the number of coordinating processes Using Test and Set Functions The C library includes a family of functions that apply the MIPS instructions Load Linked and Store Conditional to modify memory words in a reliable way in a multiprocessor These functions are detailed in the test_and_set 3 and uscas 3 reference pages In addition the MIPSpro C and C compilers version 7 0 and after contain built in support for these operatio
43. Contending Lock Using lockf 171 Setting Mandatory Locking Permission Bits 173 Partial Code to Manage a Pool of Processes 203 Debugger Display of Pthread Program 211 One Time Initialization 216 Initializing Thread Unique Data 220 Establishing Relative Priority Levels 224 Function to Set Own Priority 225 Use of Condition Variables 232 Find Number of Bytes in an MB Character 303 Counting MB Characters Without Conversion 304 Reading an XPG 4 Catalog 325 Internationalized Code 334 Initializing Xlib for a Locale 337 Creating a Fontset 339 Opening an IM 348 Finding What a Client Can Do 352 Setting the Desired IM Style 353 Creating an Input Context With XCreateIC 355 Using the IC 356 Event Loop 356 KeyPress Event 358 List of Figures Figure 1 1 Segments With a Fixed Offset Relationship 21 Figure 13 1 X Window System Font Name Example 266 Figure 13 2 Sample Display From xfd 269 Figure 14 1 Root Window Input 349 Figure 14 2 Off the Spot Input 350 xxiii List of Tables Table i Books for Further Reading in IRIX Development xxx Table ii Typographical Conventions xxxi Table 1 1 Memory System Calls 10 Table 1 2 Functions for Locking Memory 23 Table 1 3 Functions for Unlocking Memory 26 Table 2 1 Types of IPC and Compatibility 36 Table 2 2 SVR4 IPC Name Space Management 40 Table 3 1 POSIX Shared Memory Functions 45 Table 3 2 IRIX Shared Arena Management Functions 51 Table 3 3 Arena Features Set Using usconfig
44. Degree of Parallelism You can specify the number of lightweight processes that are started by a program In IRIS POWER C you can use pragma numthreads to specify the exact number of processes to start but it is not a good idea to embed this number in a source program In all implementations the run time library by default starts enough processes so there is one for each CPU in the system That default is often too high since typically not all CPUs are available for one program The run time library checks an environment variable MPC_SET _NUM_THREADS for the number of processes to start You can use this environment variable to choose the number of processes used by a particular run of the program thereby tuning the program s requirements to the system load You can even force a parallelized program to execute on a single CPU when necessary MIPSpro Fortran 77 and MIPSpro Fortran 90 also recognize additional environment variables that specify a range of process numbers and use more or fewer processes within this range as system load varies See the Programmer s Guide for the language for details At certain points the multiple processes must wait for one another before continuing They do this by waiting in a busy loop for a certain length of time then by blocking until they are signaled You can specify the amount of time that a process should spend spinning before it blocks using either source directives or an environment variable
45. Documentation for Statement Level Parallel Products Document Manual Number Contents MIPSpro Fortran 90 007 2761 nnn General use of Fortran 90 including parallelizing Programmer s Guide assertions and directives MIPSpro Power Fortran 90 007 2760 nnn Use of the Power Fortran 90 source analyzer to place Programmer s Guide directives automatically Products from Other Vendors In addition to these products from Silicon Graphics the High Performance Fortran HPF compiler from the Portland Group is a compiler for Fortran 90 augmented to the HPF standard It supports automatic parallelization Refer to http www pgroup com for more information The FORGE products from Applied Parallel Research APRI contain a Fortran 77 source analyzer that can insert parallelizing directives although not the directives supported by MIPSpro Fortran 77 Refer to http www infomall org apri for more information Creating Parallel Programs 190 In each of the three languages the language compiler supports explicit statements that command parallel execution pragma lines for C directives and assertions for Fortran However placing these statements is a demanding error prone task It is easy to create a suboptimal program or worse a program that is incorrect in subtle ways Furthermore small changes in program logic can invalidate parallel directives in ways that are hard to foresee so it is difficult to modify a program that has been man
46. Example Programs 249 Example 1 SPMD Program 249 SPMD Program in PVM Version 249 SPMD Program in MPI Version 251 Example 2 MPMD Example 252 MPMD in PVM Version Master Task 252 MPMD in PVM Version Slave Task 254 MPMD in MPI Version Master Task 255 MPMD in MPI Version Slave Task 256 xiv Contents 13 Working With Fonts 261 Font Basics 262 Terminology 262 Typography 262 Character 263 Font 263 Font Family or Typeface 263 How Resolution Affects Font Size 264 Font Names 265 Writing Programs That Need to Use Fonts 266 Using Fonts With the X Window System 267 Listing and Viewing Fonts 267 Getting a List of Font Names and Font Aliases 267 Viewing Fonts 268 Getting the Current X Font Path 270 Changing the X Font Path 270 Installing and Adding Font and Font Metric Files 271 Locations of Font and Font Metric Files 271 Conventions for Bitmap Font File Names 272 Creating Font Aliases 273 Adding Font and Font Metric Files 273 Adding a Bitmap Font 274 Adding an Outline Font 276 Adding a Font Metric File 279 Downloading a Type 1 Font to a PostScript Printer 280 14 Internationalizing Your Application 285 Overview 286 Some Definitions 287 Locale 287 Internationalization i118n 287 Localization 110n 287 Nationalized Software 288 Multilingual Software 288 XV Contents Areas of Concern in Internationalizing Software 288 Standards 289 Internationalizing Your Application The Basic Steps 289 Additional Reading on Inter
47. For these reasons file and record locking should normally be seen as a synchronization mechanism not a security mechanism The chapter includes these topics e Overview of File and Record Locking presents an introduction to locking mechanisms e Controlling File Access With File Permissions discusses the relationship of file permissions to exclusive file access e Using Record Locking discusses the use of file and record locks to get exclusive data access e Enforcing Mandatory Locking describes how file locks can be made mandatory on programs that do not use locking e Record Locking Across Multiple Systems discusses how file locking can be extended to NFS mounted files 157 Chapter 7 File and Record Locking Overview of File and Record Locking 158 Simultaneous access to file data is characteristic of many multiprocess multithreaded or real time applications The purpose of the file and record locking facility is to provide a way for programs to synchronize their use of common file data Advisory file and record locking can be used to coordinate independent unrelated processes In mandatory locking on the other hand the standard I O subroutines and I O system calls enforce the locking protocol Mandatory locking keeps unrelated programs from accessing data out of sequence at some cost of access speed The system functions used in file and record locking are summarized in Table 7 1
48. IRIS Inventor and IRIS Performer Using Fonts With the X Window System This section describes how to use fonts with the X Window System The X Window System has several font utilities This section covers a few of the most useful utilities and includes e Listing and Viewing Fonts explains using the x sfonts command e Viewing Fonts describes the xfd command e Getting the Current X Font Path covers the xset command e Changing the X Font Path explains the xset fp command For a complete description of the utilities refer to your X Window System documentation Listing and Viewing Fonts Getting a List of Font Names and Font Aliases To find out which font names and font aliases are known to the X Window System use the command xlsfonts For more information about that command see the reference page xlsfonts 1 If you enter the command xlsfonts more the resulting display contains entries such as adobe courier bold o normal 0 0 0 0 m 0 is08859 1 adobe courier bold o normal 14 100 100 100 m 90 iso8859 1 sgi screen medium r normal 14 140 72 72 m 70 1is08859 1 screenl4 267 Chapter 13 Working With Fonts 268 The first entry is an example of a 14 part X name for an outline scalable font Numeric parts of font names are set to zero for outline fonts because those fonts can be scaled to various sizes The second and third entries are examples of 14 part X font names
49. One to Two mappings collate certain characters as if they were two For example the German collates as if it were ss e Many to One mappings collate a string of characters as if they were one For example Spanish sorts ch as one character following c and preceding d In Spanish the following list is in correct alphabetical order calle creo chocolate decir e Don t Care Character rules collate certain characters as if they were not present For example if were a don t care character co op and coop would sort identically e First Vowel rules sort words based first on the first vowel of the word then by consonants which may precede or follow the vowel in question Cultural Items e Primary Secondary sorts consider some characters as equals until there is a tie For example in French a 4 a and 4 all sort to the same primary location If two strings such as tache and tache collate to the same primary order then the secondary sort distinguishes them e Special case sorts exist for some Asian languages For example Japanese kanji has no strict sorting rules Kanji strings can be sorted by the strokes that make up the characters by the kana phonetic spellings of the characters or by other agreed upon rules It should be clear that a programmer cannot hope to collate strings by simple arithmetic or by traditional methods The Solution Locale specific col
50. Reuse Sample Code 344 GL Input 344 About X Keyboard Support 344 Keys Keycodes and Keysyms 345 Composed Characters 345 Supported Keyboards 346 Input Methods IMs 347 Opening an Input Method 347 IM Styles 349 Root Window 349 Off the Spot 350 Over the Spot 350 On the Spot 351 Setting IM Styles 351 Using Styles 351 Input Contexts ICs 352 Find an IM Style 352 IC Values 353 Pre Edit and Status Attributes 354 Creating an Input Context 355 Using the IC 355 Events Under IM Control 356 Using XFilterEvent 356 Using XLookupString XwcLookupString and XmbLookupString 357 GUI Concerns 359 X Resources for Strings 359 xix Contents Layout 360 Dynamic Layout 360 Constant Layout 360 Localized Layout 361 IRIS IM Localization With editres 361 Icons 361 Popular Encodings 361 The ISO 8859 Family 362 Asian Languages 363 Some Standards 364 EUC 364 ISO 10646 and Unicode 365 A ISO 3166 Country Names and Abbreviations 367 Index 371 XX List of Examples Example 1 1 Using systune to Check Address Space Limits 7 Example 1 2 Function to Lock Maximum Stack Size 24 Example 3 1 POSIX Program to Demonstrate shm_open 48 Example 3 2 Initializing a Shared Memory Arena 53 Example 3 3 Setting Up an Arena With uscasinfo 56 Example 3 4 Resigning From an Arena 59 Example 3 5 shmget System Call Example 62 Example 3 6 shmat System Call Example 64 Example 4 1 Dynamic Allocation of POSIX Unnamed Semaphore 74 Ex
51. X programs Display Postscript DPS programs and IRIS GL and IRIS GL X programs Terminology Before discussing how to use fonts consider these terms Typography Typography is the art and technique of working with type In traditional typography the term type refers to a piece of wood or metal with a raised image of a character or characters on its upper face Such pieces of wood or metal are assembled into lines and pages which are printed by a letterpress process What typographers do with type is called typesetting or composition Type can also refer to the images produced by using such pieces of wood or metal Font Basics Traditional typesetting is seldom used today In modern typography type usually refers to the images produced on typesetting or composition systems which do not use wooden or metal type such as photo and digital composition systems The typography on a digital system such as a digital computer is called digital typography Digital typography is based on a hierarchy of objects called characters fonts and font families or typefaces Numeric values or measurements related to those objects can be divided into character metrics font metrics and typeface metrics Sometimes all information about a font family or typeface is stored in a set of font files but sometimes metric information for a set of font files is stored in a separate file called the font metric file Character A character is a gr
52. XCloseIM IM Styles If the application requests it an input method can often supply status information about itself For example a Japanese IM may be able to indicate whether it is in Japanese input mode or romaji input mode An input method can also supply pre edit information partial feedback about characters in the process of being composed The way an IM deals with status and pre edit information is referred to as an IM style This section describes styles and their naming Root Window The Root Window style has a pre edit area and a status area in a window owned by the IM as a descendant of the root The application does not manage the pre edit data the pre edit area the status data or the status area Everything is left to the input method to do in its own window as illustrated in Figure 14 1 Main body of window text input occurs here Application window root window Status Pre edit information IM window Figure 14 1 Root Window Input 349 Chapter 14 Internationalizing Your Application 350 Off the Spot The Off the Spot style places a pre edit area and a status area in the window being used usually in reserved space away from the place where input appears The application manages the pre edit area and status area but allows the IM to update the data there The application provides information regarding foreground and background colors fonts and so on A window using Off the Spot input style might
53. address space Threads within a process always share the single address space belonging to their process Processes are scheduled by the IRIX kernel A change of process requires two context changes one to enter the kernel domain and one to return to the user domain of the next process The change from the context of one process to the context of another can entail many instructions In contrast threads are scheduled by code that operates largely in the user address space without kernel assistance Thread scheduling can be faster than process scheduling The POSIX standard for multithreaded programs is supported by IRIX 6 2 with patches 1361 1367 and 1389 installed and in all subsequent releases of IRIX In addition the Silicon Graphics implementation of the Ada95 language includes support for multitasking Ada programs using what are essentially threads although not implemented using the POSIX library For a complete discussion of the Ada 95 task facility refer to the Ada 95 Reference Manual which installs with the Ada 95 compiler GNAT product Parallel Execution Models Statement Level Parallelism The finest level of granularity is to run individual statements in parallel This is provided using any of three language products e MIPSpro Fortran 77 supports compiler directives that command parallel execution of the bodies of DO loops The MIPSpro POWER Fortran 77 product is a preprocessor that automates the insertion
54. address spaces see the IRIX Device Driver Programmer s Guide and the MIPS architecture documents listed on page xxx Although the address space includes a vast quantity of potential numbers usually only a small fraction of the addresses are valid Chapter 1 Process Address Space A segment of the address space is any range of contiguous addresses Certain segments are created or reserved for certain uses The address space is called virtual because the address numbers are not directly related to physical RAM addresses where the data resides The mapping from a virtual address to the corresponding real memory location is kept in a table created by the IRIX kernel and used by the CPU Address Space Boundaries A process has at least three segments of usable addresses e A text segment contains the executable image of the program Another text segment is created for each dynamic shared object DSO with which a process is linked Text segments are always read only e A data segment contains the heap of dynamically allocated data space A process can create additional data segments in various ways described later e A stack segment contains the function call stack The segment is extended automatically as needed Although the address space begins at location 0 by convention the lowest segment is allocated at 0x0040 0000 4 MB Addresses less than this are left undefined so that an attempt to reference them for example
55. amp nproc 1 1 pyvm_pkint tids nproc 1 pyvm_pkint amp n 1 1 pyvm_pkfloat data n 1 pvm mcast tids nproc 0 Wait for results from slaves msgtype 5 for i 0 i lt nproc i pvm_recv 1 msgtype pvm_upkint amp who 1 1 pvm_upkfloat amp result who 1 1 printf I got Sf from d n result who who 253 Chapter 12 Distributed Process Parallelism Program Finished pyvm_exit Exit PVM before stopping MPMD in PVM Version Slave Task include lt stdio h gt include pvm3 h float work int me main int mytid int tids 32 int n me i nproc float data 100 float work enroll in pvm mytid pvm_mytid int n float data int tids int nproc my task id task ids master result xy msgtype Receive data from master msgtype 0 pyvm_recv l pvm_upkint amp nproc pvm upkint tids pvm_upkint n 1 pvm_upkfloat data Determine which slave I am i for i 0 i lt nproc msgtype 1 Nproc 1 n 1 1 1 0 nproc 1 if mytid tids i me i break Do calculations with data result work me n data tids nproc Send result to master pvm_initsend PvmDataDefault pyvm_pkint amp me 1 pvm_pkfloat result msgtype 5 master pvm_send master Program finished pvm_exit float work int me Simple
56. an application intends to both maintain and edit large numbers of strings then the developer needs to make size and complexity trade off decisions Cultural Items Cultural Items Support Routines for Wide Characters Analogs to the routines defined in string h and stdio h are supplied in libw a and defined in widec h This includes routines such as getwchar putwchar putws wscpy wslen and wsrchr see the wcstring 3 reference page Conversion to MB Characters Wide characters and strings are convertible to MB strings via wctomb and wcstombs respectively Reading Input Data Input can be divided into two categories user events and other data This section deals with nonuser originated data which is assumed to come from file descriptors or streams User events are discussed in User Input on page 343 It is generally fair to assume that unless otherwise specified data read by an application is encoded suitably for the current locale Text strings typically are in MB format Streams can be read in WC format by using routines defined in widec h This section discusses several aspects of a locale that may differ between locales It includes these topics e Collating Strings describes string collation e Specifying Numbers and Money explains some monetary formats and the printf and localeconv functions e Formatting Dates and Times covers using strftime to format of dates and
57. and Removing a Named Semaphore 76 Using Semaphores 76 Using Mutexes and Condition Variables 77 IRIX Facilities for Mutual Exclusion 77 Using IRIX Semaphores 77 Creating Normal Semaphores 77 Creating Polled Semaphores 78 Operating on Semaphores 79 Using Locks 80 Creating and Managing Locks 80 Claiming and Releasing Locks 81 Using Barriers 82 viii Contents Using Test and Set Functions 82 Using Test and Set 83 Using Compare and Swap 83 Using Compiler Intrinsics for Test and Set 85 System V Facilities for Mutual Exclusion 87 Creating or Finding a Semaphore Set 88 Managing Semaphore Sets 88 Using Semaphore Sets 90 Example Programs 91 Example Uses of semget 91 Example Uses of semctl for Management 93 Example Uses of semctl for Query 96 Example Uses of semop 97 Using the Examples 100 Signalling Events 103 Signals 104 Signal Numbers 104 Signal Implementations 107 Signal Blocking and Signal Masks 107 Multiple Signals 108 Signal Handling Policies 108 Default Handling 108 Ignoring Signals 109 Catching Signals 109 Synchronous Signal Handling 109 Signal Latency 110 Signals Under X Windows 110 POSIX Signal Facility 111 Signal Masking 112 Using Synchronous Handling 112 Using Asynchronous Handling 113 System V Signal Facility 115 BSD Signal Facility 116 Contents Timer Facilities 117 Timed Pauses and Schedule Cession 117 Time Data Structures 118 Time Signal Latency 118 How Timers Are Managed 119 POSIX Timers
58. assembly MIPSpro Assembly Language Programmer s 007 2418 nnn language Guide C language C Language Reference Manual 007 0701 nnn C language C Language System Overview 007 1621 nnn Fortran language MIPSpro Fortran 77 Programmer s Guide 007 2361 nnn MIPSpro Fortran 90 Programmer s Guide 007 2761 nnn Writing real time applications REACT Real Time Programmer s Guide 007 2499 nnn Controlling devices directly IRIX Device Driver Programmer s Guide 007 0911 nnn Details of the MIPS processor MIPS R4000 Microprocessor User s Manual MIPS hardware Technologies XXX About This Manual You can find additional information about internationalization from X Open Company Limited X Open Portability Guide Volume 1 XSI Commands and Utilities Volume 2 XSI System Interface and Volume 3 XSI Supplementary Definitions Berkshire United Kingdom Prentice Hall Inc Obtaining Manuals Silicon Graphics manuals are usually read online using IRIS InSight This manual and many of the books in Table i are installed as part of the IRIS Developer s Option IDO feature When the books are installed or mounted on your workstation use the command iiv or double click the InSight icon When the manuals are not accessible to your workstation you can examine or order any Silicon Graphics manual on the World Wide Web using the following URL http www sgi com Technology TechPubs If you do not have Web access you can order a printed manual from
59. class as defined by category LC_CTYPE in the program s locale for example see isalpha For class substitute one of the following alpha a letter upper an upper case letter lower a lower case letter digit a decimal digit xdigit a hexadecimal digit alnum an alphanumeric letter or digit space a character that produces white space in displayed text punct a punctuation character print a printing character graph a character with a visible representation cntrl a control character An equivalence class Any collation element defined as having the same relative order in the current collation sequence as c As an example if A and a belong to the same equivalence class then both A b and a b are equivalent to Aab Locale Specific Behavior Table 14 7 continued Character Expressions in Internationalized Regular Expressions Expression Description cc A collating symbol Multi character collating elements must be represented as collating symbols to distinguish them from single character collating elements As an example if the string ch is a valid collating element then ch is treated as an element matching the same string of characters while ch is treated as a simple list of c and h If the string is not a valid collating element in the current collating sequence definition the symbol is treated as an invalid expression c c Any collation element in the character expression ra
60. contents of the shared segment in memory 43 Chapter 3 Sharing Memory Between Processes 44 Shared Memory Based on mmap The basic IRIX system operation for shared memory is the mmap function with which a process makes the contents of a file part of its address space The fundamental uses of mmap are covered under Mapping Segments of Memory on page 11 see also the mmap 2 reference page When two or more processes map the same file into memory with the MAP_SHARED option that single segment is part of both address spaces and the processes can update its contents concurrently The POSIX shared memory facility is a simple formal interface to the use of mmap to share segments The IRIX support for shared arenas is an extension of mmap to make it simpler to create a shared allocation arena and coordinate its use The SVR4 facilities do not directly use mmap but have similar results Sharing Memory Between 32 Bit and 64 Bit Processes Larger Silicon Graphics Inc systems support both 32 bit and 64 bit programs at the same time It is possible for a memory segment to be mapped by programs using 32 bit addresses and simultaneously mapped by programs that use 64 bit addresses There is nothing to prevent such sharing However such sharing can work satisfactorily only when the contents of the shared segment include no addresses at all Pointer values stored by a 64 bit program can t be used by a 32 bit program and v
61. conventional term in computer science This book uses the simpler word lock when discussing locks in general and IRIX locks in particular and uses mutex when discussing POSIX mutexes You can use IRIX locks to coordinate between unrelated processes or lightweight processes through an IRIX shared memory arena You can use POSIX mutexes to coordinate between POSIX threads in a threaded program only not IRIX processes You define the meaning of a lock in terms that are relevant to your program s design You decide what resources can be used freely at any time and you decide what resources must be used serially by one process at a time You create and initialize a lock for each serial resource It is also your job to ensure that locks are used consistently in all parts of the program Two errors are easy to make You can forget to claim a lock so that some part of the program uses a resource freely instead of serializing Or you can forget to release a lock so that other processes trying to claim the lock hang or wait forever Both of these errors can be hard to find because the symptoms can be intermittent Most of the time there is no contention for the use of a shared variable For example if one process sometimes fails to claim a lock before updating memory the program can seem to run correctly for hours or months before it suffers precisely the right combination of coincidences that cause two processes to update the
62. conventions Xxxi systune command 7 T Taiwan country code 370 text rendering routines 340 text segment 4 loaded from program file 9 locking 24 read only 10 Type 1 font See fonts typographical conventions xxxi typography See fonts 379 Index U Uganda country code 370 Utopia fonts 280 Vv validity fault 9 video resolution 264 virtual address space See address space virtual memory font loading 281 loading pages 9 synchronizing backing store 30 See also memory virtual page number 5 virtual size 6 virtual swap 7 9 SIGKILL from 8 See also address space VME PIO 20 VPN See virtual page number Ww warning messages Ip log file 281 wide characters See internationalization wide characters 380 X xfd command 268 XFilterEvent 356 XFontSetExtents 340 XLFD font names See internationalization X Window System fontsets Xlib changes 336 XLookupString lt Default Para Fon gt 357 XmbLookupString 357 XSetLocaleModifiers 348 XwcLookupString 357 X Window System fonts See fonts installing fonts See fonts installing internationalization changes 335 limitations 335 You 8 Z Zambia country code 370 Tell Us About This Manual As a user of Silicon Graphics products you can help us to better understand your needs and to improve the quality of our documentation Any information that you provide will be useful Here is a list of suggested top
63. d d creator uid gid d d mode 0 0 nsems d n ds sem_perm uid ds sem_perm gid ds sem_perm cuid ds sem_perm cgid ds sem_perm mode ds sem_nsems else perror semctl IPC_STAT else perror semget 95 Chapter 4 Mutual Exclusion 96 Example Uses of semctl for Query The program in Example 4 5 semsnap displays a snapshot of the current values of all semaphores in a set you specify The value of each semaphore is displayed in the first row GETVAL followed by the count of processes waiting in a P operation GETNCNT and the count of processes waiting for zero GETZCNT The arguments are as follows k key Numeric key to identify the semaphore set for example k 99 i id Semaphore ID number alternative to specifying the key Example 4 5 Program to Demonstrate semctl for Sampling semsnap program to test semctl 2 for semaphore status commands semsnap k lt key gt i lt semid gt k lt key gt the key to use or i lt semid gt the semid to use XJ include lt unistd h gt for getopt include lt sys sem h gt for shmget etc include lt errno h gt errno and perror include lt stdio h gt int main int argc char argv key_t key key int semid 1 object ID int nsems j setsize and loop variable ushort_t semvals 25 snapshot of values ushort_t semns 25 snapshot of P waiting ushort_
64. data might persist across a reboot or might not depending on whether the data was written to disk before the system came down You should not depend on the state of the message queue after a reboot Once created a queue is a persistent object that survives until removed If you want the program to create a queue use it and then remove it during termination you can call mq_unlink to remove the queue 131 Chapter 6 Message Queues 132 Opening an Existing Queue It is more common to open an existing queue When the program expects the queue to exist it passes only the path and oflag arguments to mq_open and omits the O_CREAT flag bit If the queue does not exist or if the effective user ID or group ID of the program does not have access to the queue an error is returned The program can specify the O_RDONLY O_WRONLY or O_RDWR flag depending on its intended use of the queue Access is controlled by the access permissions of the queue just as for a file An important flag when opening a queue is the O_ NONBLOCK flag When it omits O_NONBLOCK from oflag the program specifies that it is willing to be suspended when sending a message to a full queue or when receiving a message from an empty queue When O_NONBLOCK is specified the program wants an immediate return with an error code EAGAIN in these situations The O_NONBLOCK flag applies to all operations using the queue descriptor returned by mq_open The same queu
65. discusses typography and font use on Silicon Graphics computers and describes the Font Manager library Part V Internationalizing Your Application explains how to create an application that can be adapted for use in different countries Appendix A ISO 3166 Country Names and Abbreviations lists country codes for use with internationalization and localization Xxix About This Manual What You Should Know Before Reading This Manual This manual assumes you are writing an application that executes under IRIX version 6 2 or later and that you are familiar with the programming conventions of UNIX in general and IRIX in particular All examples are in the C language although the descriptions are valid for C or any other language that provides access to IRIX kernel functions such as Silicon Graphics Ada95 or MIPSpro Fortran 90 Other Useful References In addition to this manual which covers specific IRIX features you will need to refer to Silicon Graphics manuals that describe compilers and programming languages Some of the most useful are listed in Table i Table i Books for Further Reading in IRIX Development Topic Document Title Number Overview of the IRIX library of Programming on Silicon Graphics Systems An 007 2476 nnn manuals for developers Overview Compiling linking and tuning MIPSpro Compiling and Performance Tuning 007 2360 nnn programs in C C or Fortran Guide Writing modules in
66. events begins For details consult the lockd 1M reference page First the kernel in the client system receives the lock request and determines that the file resides on a filesystem mounted using NFS The kernel sends the lock request to a daemon called rpe lockd This daemon is responsible for communicating lock requests to other systems Record Locking Across Multiple Systems The rpc lockd process sends the lock request to the rpc lockd daemon running on the NFS server where the target file is physically mounted On the server that rpc lockd issues the lock request locally The server rpc lockd sends the result success or failure back to the server rpc lockd The result is passed back to the calling process When the lock succeeds on the server side rpc lockd on the client system requests another daemon rpc statd to monitor the NFS server that implements the lock If the server fails and then recovers rpc statd will be informed It then tries to reestablish all active locks If the NFS server fails and recovers and rpc lockd is unable to reestablish a lock it sends a signal SIGUSR1 to the process that requested the lock When a process writes to a write locked record the data is sent directly to the NFS server bypassing the local NFS buffer cache This can have a significant impact on file performance Configuring NFS Locking When rpc lockd is not running in the NFS client system or in the NFS server system a cross sys
67. exec call define the address space by specifying which VPNs are defined These tables are consulted by the hardware Recently used table entries are cached for instant lookup in the processor chip in an array called the Translation Lookaside Buffer TLB Address Definition Most of the possible addresses in an address space are undefined that is not defined in the page tables not related to contents of any kind and not available for use A reference to an undefined address causes a SIGSEGV error Addresses are defined that is made available for potential use in one of four ways Fork When a process is created using fork the new process is given a duplicate copy of the parent process s page table so that any addresses that were defined in the parent s address space are defined in the address space of the new process Stack The call stack is created and extended automatically When a function is entered and more stack space is needed IRIX makes the stack segment larger defining new addresses if required Chapter 1 Process Address Space Mapping A process can ask IRIX to map associate byte for byte a segment of address space to one of a number of special objects for example the contents of a file This is covered further under Mapping Segments of Memory on page 11 Allocation The brk function extends the heap the segment devoted to data toa specific virtual address The malloc function allocates mem
68. file or POSIX object determine the access permitted to other processes e Map the file or POSIX object into memory with mmap initialize the segment contents by writing into it Mapping Segments of Memory e Inanother process get a file descriptor using open or the POSIX function shm_open specifying the same pathname e In that other process use mmap specifying the file descriptor of the file After this procedure both processes are using the identical segment of memory pages Data stored by one is immediately visible to the other This is the most basic method of sharing a memory segment More elaborate methods with additional services are discussed in Chapter 3 Sharing Memory Between Processes Mapping a Segment of Zeros You can use mmap to create a segment of zero filled memory Create a file descriptor by applying open to the special device file dev zero Map this descriptor with addr of 0 off of 0 and len set to the segment size you want A segment created this way cannot be shared between unrelated processes However it can be shared among any processes that share access to the original file descriptor that is processes created with sproc using the PR_SFDS flag see the sproc 2 reference page For more information about dev zero see the zero 7 reference page The difference between using mmap of dev zero and calloc is that calloc defines all pages of the segment immediately When you
69. font metric file Locations of Font and Font Metric Files By default font and font metrid files are installed in the directories listed in Table 13 1 Table 13 1 Font and Font Metric Directories Directory Path Conventional Contents usr lib DPS outline base Outline font files in the Adobe Type 1 format usr lib X11 fonts Typel Symbolic links to font files in usr lib DPS outline base usr lib DPS AFM Adobe Font Metric AFM files usr lib X11 fonts 100dpi Bitmap fonts designed for the screen resolution of 100 dpi usr lib X11 fonts 75dpi Bitmap fonts designed for the screen resolution of 75 dpi usr lib X11 fonts misc Miscellaneous other bitmap fonts usr lib X11 fonts Speedo Outline font files in the Bitstream Speedo format usr lib X11 fonts CID AFM CCM CFM CIDFont and CMap files for large outline fonts in the Adobe CID keyed format 271 Chapter 13 Working With Fonts The X Window System Display PostScript IRIS GL Font Manager Impressario and other software components use the directories listed in Table 13 1 by default The locations of font files are made known to the X Window System in two ways e Within each directory specified in the X font path a file named fonts dir contains a directory of filenames with their corresponding 14 part font names For example to see the font names available in usr lib X11 fonts 100dpi use the command more usr lib X11 fonts 100dpi fonts dir This file is created by mkfont
70. for bitmap fonts while the last entry is an alias for the third entry An X or DPS program can get a list of available fonts by calling XListFonts or the function XListFontsWithInfo Viewing Fonts To see what a particular font looks like use the command xfd and specify a font name or font alias known to the X Window System by using the option fn For example to display the 14 point Adobe Courier Bold font enter xfd fn adobe courier bold r normal 14 140 75 75 m 90 is08859 1 To request a Utopia Regular font scaled to the size of 28 points enter xfd fn adobe utopia medium r normal 0 280 0 0 p 0 is08859 1 You can use an asterisk to indicate that any value is acceptable for a part of an X font name However asterisks in a command must be protected from the shell with quotes For example enter xfd fn itc bookman demi i normal 11 80 100 100 p 63 is08859 1 to indicate that xfd can use an ITC Bookman Demi Italic font from any foundry The xfd command displays all characters in a specified font as shown in Figure 13 2 Using Fonts With the X Window System Adobe Courier Bold R Normal 14 140 75 75 M 90 1S8083859 1 Salat a character range 0x0000 0 0 thru Ox00ff 0 255 upper left 0x0000 0 0 ee ee ee ee Figure 13 2 Sample Display From xfd 269 Chapter 13 Working With Fonts 270 To open a shell window that uses a certain font enter xwsh fn font nam
71. for getopt include lt sys sem h gt for shmget etc include lt errno h gt errno and perror include lt stdio h gt int main int argc char argv key_t key key int semid 1 object ID int nsops 0 setsize and loop variable short flg 0 flag to use on all ops System V Facilities for Mutual Exclusion struct semid_ds ds int Gh SF struct sembuf sops 25 while 1 c getopt argc argv k i p v z nu switch c if if case k key key key_t strtoul optarg NULL 0 break case i semid semid int strtoul optarg NULL 0 break case n use nowait flg IPC_NOWAIT break case u use undo flg SEM_UNDO break case p do the P sops nsops sem_num ushort_t strtoul optarg NULL 0 sops nsops sem_op 1 sops nsops sem_flg flg break case v do the V sops nsops sem_num ushort_t strtoul optarg NULL 0 sops nsops sem_op 1 sops nsopst sem_flg flg break case z do the wait for zero sops nsops sem_num ushort_t strtoul optarg NULL 0 sops nsops sem_op 0 sops nsopst sem_flg flg break default unknown or missing argument return 1 1 semid i not given must have k semid semget key 0 0 1 semid if 0 semop semid sops nsops 99 Chapter 4 Mutual Exclusion
72. for keyboard input before exiting allowing you to run other copies of the program while this one has the segment mapped To create a segment named var tmp test seg use a command such as shm_open c x p 0644 s 0x80000 var tmp test seg 47 Chapter 3 Sharing Memory Between Processes To attach that segment read only and then wait use the command shm_open r w var tmp test seg From a different terminal window enter the command shm_open var tmp test seg In the original window press lt Enter gt and observe that the value of the first word of the shared segment changed during the wait Example 3 1 POSIX Program to Demonstrate shm_open Program to test shm open 3 shm_open p lt perms gt s lt bytes gt c x r t w lt path gt p lt perms gt access mode to use when creating default 0600 s lt bytes gt size of segment to map default 64K E use O CREAT use O_EXCL a ai use O_RDONLY default is O_RDWR E use O_TRUNC Ww wait for keyboard input before exiting lt path gt the pathname of the queue required include lt sys mman h gt shared memory and mmap include lt unistd h gt for getopt include lt errno h gt errno and perror include lt fcntl h gt O flags include lt stdio h gt int main int argc char argv int perms 0600 permissions size_t size 65536 segment size int oflags 0 op
73. having to reflect the system configuration in the source code The programming models are e Message Passing Interface MPI e Portable Virtual Memory PVM 187 Chapter 8 Models of Parallel Computation 188 Message Passing Interface MPI Model MPI is a standard programming interface for the construction of a portable parallel application in Fortran 77 or in C especially when the application can be decomposed into a fixed number of processes operating in a fixed topology for example a pipeline grid or tree A highly tuned efficient implementation of MPI is included with the Array 2 0 software support for Array systems such as the POWER CHALLENGEarray MPI is the recommended parallel model for use with Array products MPI is discussed in more detail under Chapter 12 Distributed Process Parallelism Portable Virtual Machine PVM Model PVM is an integrated set of software tools and libraries that emulates a general purpose flexible heterogeneous concurrent computing framework on interconnected computers of varied architecture Using PVM you can create a parallel application that executes as a set of concurrent processes on a set of computers that can include uniprocessors multiprocessors and nodes of Array systems An implementation of PVM is included with the Array 2 0 software for Silicon Graphics Array systems PVM has a better ability to deal with a heterogenous computer network than MPI does In every o
74. internationalization The X protocol and Xlib specification together with ANSI C and POSIX restrictions have led to certain choices being made in X11R6 These are described in the following paragraphs 335 Chapter 14 Internationalizing Your Application 336 Vertical Text There is no built in support for vertical text Applications may draw strings vertically only by laying out the text manually Character Sets In previous releases of X there was no general support for character sets other than Latin 1 X11R6 however does allow other character sets X11R6 includes the definition of the X Portable Character Set which is required to exist in all locales supported by Xlib There is no encoding defined for this set it is only a character set The set which is similar to printable ASCII plus the newline and tab consists of these characters abcdefghijklmnogrstuvwxyz ABCDEFGHIJKLMNOPORS TUVWXYZ 0123456789 INHESSE 4 27 lt gt I _ 1 lt space gt lt tab gt lt newline gt The Host Portable Character Encoding is the encoding of the X Portable Character Set on the Xlib host This encoding is part of X and is thus independent of locale the coding remains the same for all locales supported by the host Strings used or returned by Xlib routines are either in the Host Portable Character Encoding or a locale specific encoding The Xlib reference pages specify which encodings are used where Some stri
75. is essentially the same as the current MPI one where no tasks are dynamically spawned For this scenario the initial parallel environment setup consists of specifying the hosts to run the n tasks on You can accomplish this setup using the mechanism provided on top of the MPI library For example the setup can use a host file for mpirun or the procgroup file for the MPICH implementation General SPMD Model In this model n instances of the same program are executed as n tasks of the parallel job However one or more tasks are started by hand at the beginning and these dynamically spawn the remaining tasks in turn Here the change involves figuring out how many PVM tasks are spawned in total including those started by hand and those dynamically spawned and on what machines these tasks are run These two pieces of information can be directly translated into information number of MPI tasks and the hosts on which these are to be run that the hostfile procgroup file of the MPI setup requires You must remove all instances of the pym_spawn call from the program Most of the options of this call can be dealt by a translation into the MPI initial setup The option PomTaskDebug has no counterpart in MPI so the corresponding MPI task cannot be started in debug mode The option PumTaskTrace and its subsequent use with a tool such as XPVM can be translated to whatever profiling interface and tools are available in the given MPI implementation
76. look like that shown in Figure 14 2 Application window Main body of window text input occurs here Status Pre edit information root window Figure 14 2 Off the Spot Input Over the Spot The Over the Spot style involves the IM creating a small pre edit window over the point of insertion The window is owned and managed by the IM as a descendant of the root but it gives the user the impression that input is being entered in the right place in fact the pre edit window often has no borders and is invisible to the user giving the appearance of On the Spot input The application manages the status area as in Off the Spot but specifies the location of the editing so that the IM can place pre edit data over that spot User Input On the Spot On the Spot input is by far the most complex for the application developer The IM delivers all pre edit data via callbacks to the application which must perform in place editing complete with insertion and deletion and so on This approach usually involves a great deal of string and text rendering support at the input generation level above and beyond the effort required for completed input Since this may mean a lot of updating of surrounding data or other display management everything is left to the application There is little chance an IM could ever know enough about the application to be able to help it provide user feedback The IM therefore provides status and edit information
77. lt bytes gt c lt count gt I n e q 1 k lt key gt the key to use or i lt id gt the mq id I t lt type gt the type of message default 0 any msg System V Message Queues max siz number of messages to receive d fault 64 to receive default 1 b lt bytes gt th c lt count gt th n use e use q quiet IPC_NOWAIT flag MSG_NOERROR flag truncate long msg do not display received messag The program calls msgrcv lt count gt times or until an error occurs each time requesting a message of type lt type gt and max size lt bytes gt h types h MSG_NOERROR aes include lt sys msg h gt msg queue stuff ipc include lt unistd h gt for getopt include lt errno h gt errno and perror include lt ctype h gt isascii include lt stdio h gt int main int argc char argv key_t key key for msgget int msqid 1 specified or received msg queue id int msgflg 0 flag 0 IPC_NOWAIT long type 0 message type size_t bytes 64 message size limit int count 1 number to receive int quiet 0 quiet flag Pinte Gy struct msgspace long type char text 32 msg whil 1 1 getopt argc argv k i t b c enq switch c case k key key key_t strtoul optarg NULL 0 break case i
78. message with a user specified tag that the application can check A PVM call is also provided through which a task can kill another PVM task These functions are not available in MPI A task can leave unenroll from a PVM session as many times as it wants whereas an MPI task must initialize finalize exactly once A PVM task need not explicitly enroll the first PVM call enrolls the calling task into a PVM session An MPI task must call MPI_Init before calling any other MPI routine and it must call this routine only once A PVM task can be registered by another task as responsible for adding new PVM hosts or as a PVM resource manager or as responsible for starting new PVM tasks These features are not available in MPI 239 Chapter 12 Distributed Process Parallelism e A PVM task can multicast data to a set of tasks As opposed to a broadcast this multicast does not require the participating tasks to be members of a group MPI does not have a routine to do multicasts e PVM tasks can be started in debug mode that is under the control of a debugger of the user s choice This capability is not specified in the MPI standard although it can be provided on top of MPI in some cases e In PVM a user can use the pym_catchout routine to specify collection of task outputs in various ways The MPI standard does not specify any means to do this e PVM includes a receive routine with a timeout capability which allows the user to b
79. microseconds Locality of Reference The key to good cache performance is to maintain strong locality of reference This can be restated as a rule of thumb Keep things that are used together close together Or Extract the greatest possible use from any 128 byte cache line before touching another You must decide how to apply these principles in the context of your program design Some possible techniques e When designing a large data structure group small fields together at one end of the structure Do not mix small and large fields e Consolidate frequently tested switches flags and pointers into a single record so they tend to stay in cache e Avoid searching linked lists of structures Each time a process visits a link merely to find the address of the next link it is likely to incur a cache miss Worse a search over a long list fills the cache with unneeded links driving out useful data e Avoid striding through a large array of structures such as an array of graphics library objects visiting only one or two fields in each structure Whenever possible arrange the data so that any sequential scan visits and uses every byte before moving on 27 Chapter 1 Process Address Space 28 e Use inline function definitions for functions that are called within innermost loops Do not use inline definitions indiscriminately however because they increase the total size of the binary potentially causing more cache
80. must plan a failure strategy for the case in which you cannot obtain all the required locks It is because of contention for these records that you have decided to use record locking in the first place Different programs might e wait a certain amount of time and try again e end the procedure and warn the user e let the process sleep until signaled that the lock has been freed e acombination of the above Look now at the example of inserting an entry into a doubly linked list All the following examples assume that a record is declared as follows struct record data portion of record long prev index to previous record in the list long next index to next record in the list For the example assume that the record after which the new record is to be inserted has a read lock on it already The lock on this record must be promoted to a write lock so that the record may be edited Example 7 5 shows a function that can be used for this Example 7 5 Record Locking With Promotion Using fentl This function is called with a file descriptor and the offsets to three records in it this here and next The caller is assumed to hold read locks on both here and next This function promotes these locks to write locks If write locks on here and next are obtained Set a write lock on this Return index to this record If any write lock is not obtained Restore read locks on here and next Remove all
81. of a character The maximum number of bytes in a multibyte character is MB_LEN_MAX which is defined in limits h The maximum number of bytes in a character under the current locale is given by the macro MB_CUR_MAX defined in stdlib h How Many Bytes in an MB String Since strlen simply counts bytes before the first NULL it tells you how many bytes are in an MB string How Many Characters in an MB String When mbstowcs converts MB strings to WC strings it returns the number of characters converted This is the simplest way to count characters in an MB string Note Many code segments that deal with individual characters within a string are better served by wide character strings Since counting often involves conversion such segments are often better served by working with a WC string then converting back Getting the length without performing the conversion is straightforward but not as simple mbtowc converts one character and returns the number of bytes used but returns the same information without conversion if a NULL is passed as the address of the WC destination Thus len mblen pStr n is equivalent to len mbtowc wchar_t NULL pStr n 303 Chapter 14 Internationalizing Your Application 304 In fact mblen calls mbtowc to perform its count Therefore counting characters in an MB string without converting would look like the code in Example 14 2 Example 14 2 Counting MB Characters Wit
82. other locks Using Record Locking 1 Return 1 long set3Locks int struct flock 1 lck l_type F lck l whence lck l_len si Promote the lck 1l_start if fcentl fd return 1 Lock this bekit start LE Lontl id Failed lck 1l_type lck l_star void fcn return L Promote loc lck l_start if fenti tfd Failed sb type lck l_ustar void fcn Ar ais GANG Lek I type k LEK LC K K lc fen 1 void re turn return this l_start fd long this long here long next ck _WRLCK setting a write lock 0 offsets are absolute zeof struct record lock on here to write lock here F_SETLKW amp lck lt 0 with write lock this F_SETLKW amp lck lt 0 to lock this return here to read lock F_RDLCK t here tl fd F_SETLKW amp lck k on next to write lock next F_SETLKW amp lck lt 0 to promote next return here to read lock F_RDLCK t here tl fd F_SETLK amp 1lck remove lock on this F_UNLCK t this tl fd F_SETLK amp lck Example 7 5 uses the F_SETLKW command to fentl with the result that the calling process will sleep if there are conflicting locks at any of the three points If the F_SETLK command was used instead the fentl system calls would fail if blocked The program would
83. page from then on The backing store for unmodified pages is the file while the backing store for modified pages is the system swap space When MAP_AUTOGROW is specified also a store beyond the end of the segment lengthens only the private copy of the segment the file is unchanged The difference between MAP_SHARED and MAP_PRIVATE is important only when the segment can be modified When the prot argument does not include PROT_WRITE there is no question of modifying or extending the segment so the backing store is always the mapped object However the choice of MAP_SHARED or MAP_PRIVATE does affect how you lock the mapped segment into memory if you do see Locking Program Text and Data on page 24 Processes created with sproc normally share a single address space including mapped segments see the sproc 2 reference page However if flags contains MAP_LOCAL each new process created with sproc receives a private copy of the mapped segment on a copy on write basis Mapping Segments of Memory When the segment is based on a file or on dev zero see Mapping a Segment of Zeros on page 19 mmap normally defines all the pages in the segment This includes allocating swap space for the pages of a segment based on dev zero However if flags contains MAP_AUTOGROW the pages are not defined until they are accessed see Delayed and Immediate Space Definition on page 7 Note The MAP_LOCAL and MAP_AUTOGROW flag ele
84. passing messages IRIX with the Array 2 0 software package supports two libraries on which you can build a distributed message passing application Message Passing Interface MPI and Portable Virtual Machine PVM High level overviews of these are given under Distributed Computation Models on page 187 235 Chapter 12 Distributed Process Parallelism Choosing Between MPI and PVM 236 Silicon Graphics has adopted the MPI interface as the primary and preferred model for distributed applications on Array processors There are occasions when you may elect to use PVM instead but in general MPI is recommended for new applications and for applications that are being ported to a Silicon Graphics Array system In many ways MPI and PVM are similar e Each is designed specified and implemented by third parties that have no direct interest in selling hardware e Support for each is available over the Internet at low or no cost e Each defines portable high level functions that are used by a group of processes to make contact and exchange data without having to be aware of the communication medium e Each supports C and Fortran 77 e Each provides for automatic conversion between different representations of the same kind of data so that processes can be distributed over a heterogeneous computer network The primary reason MPI is preferred for Array systems is performance The design of MPI is such that a highly optimized
85. result a segment of memory that can be accessed or updated asynchronously by more than one process You have to design protocols that prevent one process from changing shared data while another process is using the same data see Chapter 4 Mutual Exclusion This chapter covers three major topics e POSIX Shared Memory Operations on page 45 describes the POSIX functions for sharing memory e IRIX Shared Memory Arenas on page 50 describes IRIX shared memory arenas e System V Shared Memory Functions on page 60 describes the SVR4 functions Overview of Memory Sharing The address space is the range of memory locations that a process can use without an error The concept of the address space is covered in detail in Chapter 1 Process Address Space In a pthreads program all threads use the same address space and share its contents In a program that starts multiple lightweight processes with sproc all processes share the same address space and its contents In these programs the entire address space is shared automatically Normally distinct processes created by the fork or exec system calls have distinct address spaces with no writable contents in common The facilities described in this chapter allow you to define a segment of memory that can be part of the address space of more than one process Then processes or threads running in different address spaces can share data simply by referring to the
86. server specific object so a server connection is not necessary Example 14 5 Initializing Xlib for a Locale if setlocale LC_ALL NULL exit_with_error if XSupportsLocale exit_with_other_error if XSetLocaleModifiers NULL give_warning XSetLocaleModifiers is required only for input Just as passing an empty string to setlocale honors the user s environment so does passing an empty string to XSetLocaleModifiers 337 Chapter 14 Internationalizing Your Application 338 Fontsets In X11R5 and X11R6 unlike previous releases of X a string may contain characters from more than one codeset There are several methods for determining which codeset a given character is in which method is appropriate depends on the locale and the encoding used For information on installing and using fontsets with an application refer to Chapter 13 Working With Fonts Such multiple codeset strings usually cannot be rendered using a single font A fontset is a collection of fonts suitable for rendering all codesets represented in a locale s encoding A fontset includes information to indicate which locale it was created in Applications create fontsets for their own use when a program creates a fontset it is told which of the requested fonts are unavailable Example EUC in Japanese To render strings encoded in EUC in Japanese an application would need fonts encoded in 8859 1 JIS X 20
87. significant ways e A lightweight process still has a full set of UNIX state values Some of these for example the table of open file descriptors can be shared with the parent process but in general a lightweight process carries most of the state information of a process e Dispatch of lightweight processes is done in the kernel and has the same overhead as dispatching any process The library support for statement level parallelism is based on the use of lightweight processes see Statement Level Parallelism on page 187 Thread Level Parallelism A thread is an independent execution state within the context of a larger program The concept of a thread is well known but the most common formal definition of threads and their operation is provided by POSIX standard 1003 1c System Application Program Interface Amendment 2 Threads Extension 185 Chapter 8 Models of Parallel Computation 186 There are three key differences between a thread and a process A UNIX process has its own set of UNIX state information for example its own effective user ID and set of open file descriptors Threads exist within a process and do not have distinct copies of these UNIX state values Threads share the single state belonging to their process Normally each UNIX process has a unique address space of memory segments that are accessible only to that process lightweight processes created with sproc share all or part of an
88. some extensions to traditional regular expression syntax for internationalized software Few application developers do their own regular expression parsing and matching however so we do not include full details here Briefly the extensions provide the ability to specify matches based on e character class such as alpha digit punct or space e equivalence class for instance a a a A A A and A may be equivalent e collating symbols allowing you to match the Spanish ch as one element because it is a single collating token e generalization of range specifications of the form c7 c2 to include the above If you are processing expressions see the description of internationalized regular expression grammar in Using Regular Expressions Locale Specific Behavior You can internationalize an application so it can span a range of language and cultural environments This section covers some locale specific topics you should consider when internationalizing an application Topics include e Overview of Locale Specific Behavior e Native Language Support and the NLS Database e Using Regular Expressions e Cultural Data Much of the information in this section is from the X Open Portability Guide For additional information on locale specific behavior refer to the X Open Portability Guide Volume 3 XSI Supplementary Definitions 311 Chapter 14 Internationalizing Your Application 312
89. specified file doesn t exist usinit creates it and gives it the access permissions specified to usinit with CONF_CHMOD If a shared arena already exists based on that name usinit joins that shared arena If the file exists but is not yet a shared arena usinit overwrites it In any case usinit is subject to normal filesystem permission tests and it returns an error if the process doesn t have read and write permission on the file if it already exists or permission to create the file if it doesn t exist IRIX Shared Memory Arenas Code to prepare an arena is shown in Example 3 2 Example 3 2 Initializing a Shared Memory Arena usptr_t makeArena size_t initSize int nProcs int ret char tmpname var tmp arenaXXXXXX if ret usconfig CONF_INITUSERS nProcs perror usconfig users return 0 if ret usconfig CONF_INITSIZE initSize perror usconfig size return 0 return usinit mktemp tmpname Joining an Arena Only one process creates a shared arena Other processes join or attach the arena There are three ways of doing this When the arena is not restricted to a single process family either by file permissions or by CONF_ARENATYPE setting any process that calls usinit and passes the same pathname string gains access to the same arena at the same virtual base address This process need not be related in any way to the process that creat
90. specify MAP_AUTOGROW mmap does not actually define a page of the segment until the page is accessed You can create a very large segment and yet consume swap space in proportion to the pages actually used Note This feature is unique to IRIX The file dev zero may not exist in other versions of UNIX Since the feature is nonportable you should not use the POSIX function shm_open with dev zero or any device special file Mapping Physical Memory You can use mmap to create a segment that is a window on physical memory To do so you create a file descriptor by opening the special file dev mem For more information see the mem 7 reference page 19 Chapter 1 Process Address Space 20 Obviously the use of such a segment is nonportable hardware dependent and dependent on the OS release Mapping Kernel Virtual Memory You can use mmap to create a segment that is a window on the kernel s virtual address space To do so you create a file descriptor by opening the special file dev mmem note the double m For more information see the mem 7 single m reference page The acceptable off and Jen values you can use when mapping dev mmem are defined by the contents of var sysgen master d mem Normally this file restricts possible mappings to specific hardware registers such as the high precision clock For an example of mapping dev mmem see the example code in the syssgi 2 reference page under the SGI_QUE
91. take action at regular times Intervals are presented to the program as signals These two issues are covered in the following topics e Signals on page 104 describes signal facilities in general and details the differences between the POSIX SVR4 and BSD interfaces e Timer Facilities on page 117 describes POSIX and IRIX methods of defining timestamps and intervals 103 Chapter 5 Signalling Events Signals 104 A signal is a notification of an event sent asynchronously to a process Some signals originate from the kernel in response to hardware traps for example the SIGFPE signal that notifies of an arithmetic overflow or the SIGALRM that notifies of the expiration of a timer interval Other signals are issued by software For a detailed formal discussion of signals read the signal 5 reference page A process can block all signals or selected signals ignore some signals or request a default system handling for some signals When a signal that has been sent to a process is blocked by the process the signal remains pending When a signal is not blocked the process receives the signal In a multithreaded process signals can be blocked or received by individual threads When receiving a signal a process or thread can handle the signal by an asynchronous call into a signal handling function Alternatively using the POSIX interface a process or thread can handle signals synchronously as a stream of event o
92. that this is an implementation choice not a standardized behavior Other implementations of POSIX IPC may implement a separate name space for IPC objects and the IRIX implementation is free to change its implementation in the future For best portability do not assume that IPC objects are always files If you plan to share an object between processes that could be started from different working directories you should always open the object using the full pathname starting with a slash That ensures that unrelated processes always refer to the same object If the shared object is temporary you can use the tempnam library function to generate a temporary pathname see the tempnam 3 reference page Other POSIX IPC objects nameless semaphores mutexes and condition variables are not persistent but exist only in memory and are identified only by their addresses They disappear when the programs that use them terminate Using IRIX IPC Using IRIX IPC Using System V IPC The IRIX IPC facilities are designed to meet the demands of parallel programming in multiprocessor systems They offer advantages for this use but they are IRIX specific so code using them is not portable to other systems In order to use any IRIX IPC functions you need to include the correct header files and link libraries when compiling The header files required for each function are listed in the reference pages for the functions IRIX IPC func
93. the first it should use the initialized contents that another process has already prepared This problem is resolved with uscasinfo as sketched by the code in Example 3 3 Example 3 3 Setting Up an Arena With uscasinfo typedef struct arenaStuff ulock_t updateLock exclusive use of this structure short joinedProcs number of processes joined pointers to other things allocated by setUpArena arenaStuff_t The following function performs the one time setup of the arenaStuff contents It assumes that updateLock is held xj extern void setUpArena usptr_t arena arenaStuff_t stuff The following function joins a specified arena creating it and initializing it if necessary It could be extended with values to pass to usconfig 3 before the arena is created ES usptr_t joinArena char arenaPath usptr_t arena arenaStuff_t stuff int ret Join the arena creating it if necessary Exit on error if arena usinit arenaPath IRIX Shared Memory Arenas perror usinit return arena Do the following as many times as necessary until the arena has been initialized for ret 0 ret LE stuff arenaStuff_t usgetinfo arena Another process has created the arena and either has initialized it or is initializing it right now Acquire the lock which will block us u
94. the same principle applies Multiprocessor Cache Conflicts In a multiprocessor system such as a Challenge system when one CPU modifies cached data it broadcasts the fact on the bus Any other CPU holding that same cache line marks it invalid If another CPU then needs to refer to the so called dirty cache line it has to fetch the modified version from the first CPU This takes even longer than reloading the cache line from main memory Additional Memory Features These conflicts can cause cache delays when the processes in two or more CPUs are working on the same data concurrently There is no conflict so long as all CPUs are reading the data Each works from its own cache copy in that case But whenever one CPU modifies the data all other CPUs suffer a cache miss on the next access to the same data In general the only way to avoid such conflicts is to separate the readers and writers in time Arrange the program so that data is updated occasionally in a burst then used for a longer period Detecting Cache Problems There are relatively few tools for detecting or fixing cache problems in code You can combine the two IRIX profiling tools pixie and prof see the pixie 1 and prof 1 reference pages to arrive at a tentative diagnosis The pixie tool modifies the executable of a program so that every basic block is counted during execution Its output ranks functions by the absolute count of instructions they executed Th
95. to handle signals asynchronously in a program that uses X intrinsics you must take special steps Before establishing a signal handler with the operating system you establish one or more signal callback procedures using XtAppAddSignal Then in the asynchronous signal handling function you call XtNoticeSignal This function ensures that the established signal callback will be invoked like other callback functions when it is safe to do so This process is documented in the XtAppAddSignal 3Xt reference page The only X windows function that can safely be called from a signal handler is XtNoticeSignal Signals POSIX Signal Facility The POSIX interface to signals is the most functionally complete and robust of the three It is the recommended interface for all new programs The functions used in POSIX style signal handling are summarized in Table 5 3 Table 5 3 Functions for POSIX Signal Handling Function kill 2 sigqueue 3 pthread_kill 3P sigprocmask 2 pthread_sigmask 3P sigaction 2 sigaltstack 2 sigpending 2 sigsetops 3 sigsuspend 2 sigwait 3 sigtimedwait 3 sigwaitinfo 3 Purpose Send a signal to a process or process group Discards multiple signals of the same number Queue a signal to a specified process including a sigval for added information about the signal Queues multiple signals of the same number Send a signal to a specified thread Examine or change the mask of si
96. valid only for processes that are locking files or records on a single system Deadlocks can potentially occur only when the system is about to put a record locking system call to sleep A search is made for constraint loops of processes that would cause the system call to sleep indefinitely If such a situation is found the locking system call fails and sets errno to the deadlock error number If a process wishes to avoid using the system s deadlock detection it should set its locks using F_GETLK instead of F_GETLKW Enforcing Mandatory Locking 172 File locking is usually an in memory service of the IRIX kernel The kernel keeps a table of locks that have been placed Processes anywhere in the system update the table by calling fentl or lockf to request locks When all processes that use a file do this and respect the results file integrity can be maintained It is possible to extend file locking by making it mandatory on all processes whether or not they were designed to be part of the cooperating group Mandatory locking is enforced by the file I O function calls As a result an independent process that calls write to update a locked record is blocked or receives an error code The write and other system functions test for a contending lock on a file that has mandatory locking applied The test is made for every operation on that file When the caller is a process that is cooperating in the lock and has already set an a
97. variable at the same time 69 Chapter 4 Mutual Exclusion 70 Semaphores A semaphore is an integer count that is accessed atomically using two operations that are conventionally called P and V e The P operation mnemonic deplete decrements the count If the result is not negative the operation succeeds and returns If the result is negative the P operation suspends the calling process until the count has been made nonnegative by another process doing a V operation e The V operation mnemonic revive increments the count If this changes the value from negative to nonnegative one process that is waiting in a P operation is unblocked You can use a semaphore in place of a lock to enforce serial use of resource You initialize the semaphore to a value of 1 The P operation claims the semaphore leaving it at 0 so that the next process to do P will be suspended The V operation releases the semaphore You can also use a semaphore to control access to a pool that contains a countable number for resources For example say that a buffer pool contains n buffers A process can proceed if there is at least 1 buffer available in the pool but if there are no buffers the process should sleep until at least 1 buffer is returned A semaphore initialized to n represents the population of the buffer pool The pool itself might be implemented as a LIFO queue The right to update the queue anchor either to remove a buffer or to return o
98. variety of IPC mechanisms IRIX conforms to the POSIX standards for real time extensions IEEE standard 1003 1b and threads IEEE 1003 1c Other IPC features are compatible with the two major schools of UNIX programming BSD UNIX and AT amp T System V Release 4 SVR4 UNIX Table 2 1 summarizes the types of IPC that IRIX supports and lists the systems with which IRIX is compatible Table 2 1 Types of IPC and Compatibility Type of IPC Purpose Compatibility Signals A means of receiving notice of a software or POSIX SVR4 BSD hardware event asynchronously Shared memory A way to create a segment of memory that is mapped POSIX IRIX SVR4 into the address space of two or more processes each of which can access and alter the memory contents Semaphores Software objects used to coordinate access to POSIX IRIX SVR4 countable resources Locks Mutexes Software objects used to ensure exclusive use of POSIX IRIX and Condition single resources or code sequences Variables Barriers Software objects used to ensure that all processes ina IRIX group are ready before any of them proceed Message Queues Software objects used to exchange an ordered POSIX SVR4 sequence of messages File Locks A means of gaining exclusive use of all or partofa SVR4 BSD file Sockets Virtual data connections between processes that may BSD be in different systems 36 Types of Interprocess Communication Available The different impleme
99. via callbacks Done well this style can be the most intuitive one for a user Setting IM Styles A style describes how an IM presents its pre edit and status information to the user An IM supplies information detailing its presentation capabilities The information comes in the form of flags combined with OR The flags to use with each style are as follows Root Window XIMPreeditNothing XIMStatusNothing Off the Spot XIMPreeditArea XIMStatusArea Over the Spot XIMPreeditPosition XIMStatusArea On the Spot XIMPreeditCallbacks XIMStatusCallbacks For example if you wanted a style variable to match an Over the Spot IM style you could write XIMStyle over XIMPreeditPosition XIMStatusArea If an IM returns XIMStatusNone not to be confused with XIMStatusNothing it means the IM will not supply status information Using Styles An input method supports one or more styles It s up to the application to find a style that is supported by both the IM and the application If several exist the application must choose If none exist the application is in trouble 351 Chapter 14 Internationalizing Your Application 352 Input Contexts ICs An input method may be serving multiple clients or one client with multiple windows or one client with multiple input styles on one window The specification of style and client IM communication is done via input contexts An input context is simply a collection of parameter
100. will use any specific keyboard Keyboards change from country to country and language to language internationalized software should never assume that a certain position on the keyboard is bound to a certain character or that a given character will be available as a single keystroke on all keyboards No useful physical keyboard not even one specifically designed for multilingual work could possibly contain a key for every character we would ever wish to type Certainly there are characters commonly used in other areas of the world that are not present on most USA keyboards So methods have been invented that provide for input of almost any known character on even the most naive keyboards These schemes are referred to as input methods IMs 343 Chapter 14 Internationalizing Your Application 344 Input methods vary significantly in design use and behavior but there is a single API that developers use to access them The object is for the application simply to ask for an IM and let the system check the locale and choose the appropriate IM Some IMs are complex others are very simple The API is designed to be a low level interface like Xlib Usually only toolkit text object authors must deal with the IM interfaces However some applications developers are unable to use toolkit objects so the concepts are described here Reuse Sample Code Asample program demonstrating some of the concepts in this section is given in Chapter
101. you can consult for additional information about internationalization Overview Some Definitions This section defines some of the terms used in this chapter Locale Locale refers to a set of local customs that determine many aspects of software input and output formatting including natural language culture character sets and encodings and formatting and sorting rules The locale of a program is the set of such parameters that are currently selected For information on the method for selecting locales see Additional Reading on Internationalization below Internationalization i18n Internationalization is the process of making a program capable of running in multiple locales without recompiling To put it another way an internationalized program is one that can be easily localized without changing the program itself See Localization 110n below for an explanation of the term localization Note The word internationalization consists of an i followed by 18 letters followed by an n It is thus often abbreviated i18n in informal writing On similar principles localization is often abbreviated 110n A program written for a specific locale may be difficult to run in a different environment Rewriting such a program to operate in each desired environment would be tedious and costly Your goal as a developer should thus be to write locale independent programs programs that make no a
102. your program first opens it with shm_open then maps it into memory with mmap The arguments to mmap include e the file descriptor for the shared object e the size of the memory segment e access protection flags The returned value is the base address of the segment in memory You can then use it like any block of memory For example you could create an allocation arena in the segment using the acreate function see the amalloc 3 reference page For more on the use of mmap read The Segment Mapping Function mmap on page 12 and Mapping a File for Shared Memory on page 18 Example Program The program in Example 3 1 allows you to experiment with shm_open and mmap from the command line The program accepts the following command line arguments path The pathname of a shared memory segment file that exists or that is to be created p perms The access permissions to apply to a newly created segment for example p 0664 s bytes The initial size at which to map the segment for example s 0x80000 c Use the O_CREAT flag with open creating the segment if it doesn t exist X Use the O_EXCL flag with open requiring the segment to not exist t Use the O_TRUNC flag with open truncating the file to zero length r Use the O_RDONLY flag with open and PROT_READ with mmap If this option is not used the program uses O_RDWR with open and PROT_READ PROT_WRITE PROT_AUTOGROW with mmap w Wait
103. your system and possilby to your printer in order to use it Adobe Systems donated bitmap outline and font metric files for the Utopia font family to the X Consortium This section shows how the font and font metric files for Utopia Regular were added to the IRIX operating system Other font and font metric files can be added in a similar way You need superuser privilege to make changes to X font directories Before you make any changes to any IRIX directory make a copy of its contents so that you can restore that directory if anything goes wrong For example your font files may not be in the right format and they may interfere with the access of Silicon Graphics font files Keep a log of the changes you make and mention those changes when you report a problem with font files to Silicon Graphics otherwise it may be very difficult or impossible for other people to reproduce any problems that you might report 273 Chapter 13 Working With Fonts Adding a Bitmap Font The procedure in this section shows how to add Utopia Regular bitmap fonts to IRIX Other fonts can be added in a similar way To add the Utopia bitmap fonts to the X Window System Display PostScript and IRIS GL Font Manager follow these steps 1 Log in as root 2 Choose names for the installed bitmap files Refer to the naming conventions for existing bitmap font files see Conventions for Bitmap Font File Names on page 272 and use names with a consisten
104. 0 0 p 0 iso08859 1 Utopia Italic adobe utopia medium i normal 0 0 0 0 p 0 iso8859 1 Utopia Regular adobe utopia medium r normal 0 0 0 0 p 0 is08859 1 The first field is the PostScript font name as specified in the outline font file see Adding an Outline Font on page 276 The second field is the X 14 part font name with 0 for all specific dimension values When you add your own bitmap or outline fonts put their entries in a file called usr lib X11 fonts ps2xlfd_map local That way your entries do not disappear when you upgrade your system software Make sure that there is no overlap between your entries and the entries in other ps2xlfd_map files 6 If you want to establish alias names for any of the new fonts create or edit fonts alias files in the appropriate directories see Creating Font Aliases on page 273 275 Chapter 13 Working With Fonts 276 7 Invoke the mkfontdir command to rebuild the fonts dir database in each directory where you added bitmap files Enter the command mkfontdir usr 1ibX11 fonts dpi to create a new fonts dir fonts directory file in the 100dpi and 75dpi directories 8 Use the xset command to notify the window system to rebuild its list of fonts xset fp rehash 9 To check whether the fonts you added are known to the X Window System enter xlsfonts gt tmp fontlist The names of the fonts you added should appear on the list of font names an
105. 1 shmctl 61 shmdt 61 shmeget example 62 SVR4 60 65 shmat 61 shmctl 61 shmdt 61 SVR4 style 36 types 37 Iran country code 368 Ireland country code 368 IRIX and IPC 36 ISO 3166 Country Codes 367 370 Israel country code 368 Italy country code 368 J Japan country code 368 375 Index K Kenya country code 368 kernel address space limits in 6 kernel address space 3 Korea country code 368 L 110n See localization languages ISO See internationalization encodings languages Latin See internationalization encodings Laos country code 369 LC_ALL 293 LC_COLLATE 293 LC_CTYPE 293 LC_MESSAGES 293 LC_MONETARY 293 LC_NUMERIC 293 LC_TIME 293 LEGEND 332 lightweight process and mapped segments 14 limits command 6 linked lists and cache management 27 locale Motif 342 locales 292 298 categories 293 C locale value 296 collation 307 cultural data 320 data location 295 date formats 309 320 defined 287 empty strings 294 376 encoding 296 languages 295 location of data 295 modifiers 296 monetary formats 307 naming conventions 295 nonempty strings 295 numerical formats 307 setlocale 292 setting current 292 sorting rules 306 territories 295 time formats 309 locale specific behavior date 320 time 320 Locality of Reference 27 localization defined 287 empty strings 294 nonempty strings 295 lockf to protect mapped file 18 l
106. 1 4 continued Functions for Managing Thread Execution Function Purpose pthread_setcanceltype 3P Specify deferred or asynchronous cancellation pthread_testcancel 3P Permit cancellation to take place if it is pending Getting the Thread ID Call pthread_self to get the thread ID of the calling thread A thread can use this thread ID when changing its own scheduling priority for example see Scheduling Pthreads on page 223 Initializing Static Data Your program may use static data that should be initialized but only once The code can be entered by multiple threads and might be entered concurrently How can you ensure that only one thread will perform the initialization The answer is to create a variable of type pthread_once_t statically initialized to the value PTHREAD_ONCE_INIT In the module code call pthread_once passing the addresses of the variable and of an initialization function The pthreads library ensures that the initialization function is called only once and that any other threads calling pthread_once for this variable wait until the first thread completes the call An example is shown in Example 11 2 Example 11 2 One Time Initialization pthread_once_t first_time_flag PTHREAD_ONCE_INIT elaborate_struct_t uninitialized thing to initialize void elaborate_initializer void function to do it int subroutine pthread_once amp first_time_flag elabora
107. 120 Getting Program Execution Time 121 Creating Timestamps 121 Using Interval Timers 123 BSD Timers 125 Hardware Cycle Counter 126 6 Message Queues 127 Overview of Message Queues 128 Implementation Differences 128 Uses of Message Queues 129 POSIX Message Queues 130 Managing Message Queues 131 Creating a Message Queue 131 Opening an Existing Queue 132 Using Message Queues 132 Sending a Message 133 Receiving a Message 133 Using Asynchronous Notification 133 Example Programs 134 Example of mq_getattr 135 Example of mq_open 136 Example of mq_send 138 Example of mq_receive 140 System V Message Queues 143 Contents Managing SVR4 Message Queues 143 Creating a Message Queue 143 Accessing an Existing Queue 144 Modifying a Message Queue 144 Removing a Message Queue 144 Using SVR4 Message Queues 145 Sending a Message 145 Receiving a Message 145 Example Programs 146 Example of msgget 147 Example of msgctl 149 Example of msgsnd 152 Example of msgrcv 154 File and Record Locking 157 Overview of File and Record Locking 158 Terminology 158 Record 158 Read Shared Lock 159 Write Exclusive Lock 159 Advisory Locking 159 Mandatory Locking 159 Lock Promotion and Demotion 160 Controlling File Access With File Permissions 160 Using Record Locking 161 Opening a File for Record Locking 161 Setting a File Lock 162 Whole File Lock With fentl 162 Whole File Lock With lockf 163 Whole File Lock With flock 164 Setting and
108. 4 for more information Provide a catalog for your locale See SVR4 MNLS Message Catalogs on page 328 for more information The File Typing Rule FTR strings that are used to customize the Indigo Magic desktop can be Internationalized See Internationalizing File Typing Rule Strings With MNLS on page 332 for more information Use message catalogs for printf format strings that take linguistic parameters and allow localizers to localize the format strings as well as text strings See Variably Ordered Referencing of printf Arguments on page 333 for more information If you re using Xlib initialize Xlib s internationalization state after calling setlocale See Initialization for Xlib Programming on page 337 for more information Specify a default fontset suitable for the default locale Make sure that the application accepts localized fontset specifications via resources or message catalogs or command line options See Fontsets on page 338 for more information Overview 16 17 18 19 20 21 Use X11R5 and X11R6 text rendering routines that understand multibyte and wide character strings not the X11R4 text rendering routines XDrawText XDrawString and XDrawImageString See Text Rendering Routines on page 340 for more information Use X11R5 and X11R6 MB and WC versions of width and extents interrogation routines See New Text Extents Functions on page 340 fo
109. 73 covers the POSIX functions for semaphores and mutexes e IRIX Facilities for Mutual Exclusion on page 77 covers IRIX locks barriers and semaphores and the test and set facility e System V Facilities for Mutual Exclusion on page 87 covers System V semaphores 67 Chapter 4 Mutual Exclusion Overview of Mutual Exclusion 68 IRIX offers five kinds of mutual exclusion each kind with its limits and advantages e Test and set instructions use special instructions in the MIPS CPU to update a memory location in a predictable way e The lock or mutex enables processes to enforce serial use of data or code e The condition variable lets a thread give up a lock and sleep until an event happens then reclaim the lock and continue all in a single operation e The semaphore lets independent processes manage a countable resource in an orderly way e The barrier lets processes coordinate their initialization There is a hierarchy of complexity Test and set instructions are a primitive facility that could be used to implement the others The lock is a simple object that could be used to implement semaphores and barriers The semaphore is the most flexible and general facility Test and Set Instructions The MIPS instruction architecture includes two instructions designed to let programs update memory from independent processes running concurrently in a multiprocessor e The Load Linked LL instruction loads
110. 8 and JIS X 201 The application doesn t need to know which characters in a string go with which font since it doesn t deal with locale specifics So it creates a fontset that is made from a list of user specified fonts under the assumption that the localizer has provided an appropriate list Rendering is then done using that fontset The locale aware rendering system chooses the appropriate fonts for each character being rendered from the supplied list You can find additional information about EUC in Asian Languages Specifying a Fontset A fontset specification is just a string enumerating XLFD names of fonts See X Logical Font Description Conventions an MIT X Consortium standard as well as Font Names on page 265 This string can include wild card characters For example a specification of 16 point fixed fonts might be as follows char fontSetSpecString fixed medium r normal 150 Based on the fonts available a particular server might expand this to a string such as jis fixed medium r normal 16 150 75 75 c 160 jisx0208 1983 0 sony fixed medium r normal 16 150 75 75 c 80 1s08859 1 sony fixed medium r normal 16 150 75 75 c 80 jisx0201 1976 0 Internationalization Support in X11R6 Specifying the fontset by simply enumerating the fonts is perfectly acceptable char fontSetSpecString jJis fixed medium r normal 150 75 75 jisx0208 1983 0 sony fixed medium
111. CREAT x include lt sys msg h gt msg queue stuff ipc h types h include lt unistd h gt for getopt include lt errno h gt errno and perror include lt stdio h gt int main int argc char argv key_t key IPC_PRIVATE key int perms 0600 permissions int msgflg 0 flags CREAT EXCL int msqid returned msg queue id struct msqid_ds buf buffer for stat info Int CF whil kl c getopt argc argv K p xc switch c case k key key key_t strtoul optarg NULL 0 break case p permissions perms int strtoul optarg NULL 0 break case c msgflg IPC_CREAT break case x msgflg IPC_EXCL break default unknown or missing argument return 1 System V Message Queues msgid msgget key msgflg perms if 1 msqid printf msqid 0x 04x msqid j if 1 msgctl msqid IPC_STAT amp buf printf owner d d perms 040 max bytes d n buf msg_perm uid buf msg_perm gid buf msg_perm mode buf msg_qbytes printf Sd msgs d bytes on queue n buf msg_qnum buf msg_cbytes else else perror nmsgctl perror msgget Example of msgctl The program msgctl in Example 6 6 allows you to display the state of a queue or to change the permissions owner ID group ID or maximum size of a queu
112. CURRENT the new mapped segment is not locked Pages of file data are read on demand as the program accesses them 25 Chapter 1 Process Address Space 26 From these facts you can conclude the following e You should map small files before locking memory thus getting fast access to their contents without paging delays e Conversely if you map a file after locking memory your program could be delayed for input on any access to the mapped segment e However if you map a large file and then try to lock memory the attempt to lock could fail because there is not enough physical memory to hold the entire address space including the mapped file One alternative is to map an entire file perhaps hundreds of megabytes into the address space but to lock only the portion or portions that are of interest at any moment For example a visual simulator could lock the parts of a scenery file that the simulated vehicle is approaching When the vehicle moves away from a segment of scenery the simulator could unlock those parts of the file and possibly use madvise to release them see Releasing Unneeded Pages on page 31 Unlocking Memory The function summarized in Table 1 3 are used to unlock memory Table 1 3 Functions for Unlocking Memory Function Name Compatibility Purpose and Operation munlock 3C POSIX Unlock a specified range of locked addresses mlockall 3C POSIX Unlock the entire address space of the calling pr
113. C_CREAT break case x shmflg IPC_EXCL break default unknown or missing argument return 1 shmid shmget key size shmflg perms if 1 shmid printf shmid d 0x x n shmid shmid if 1 shmctl shmid IPC_STAT amp ds printf owner uid gid d d n ds shm_perm uid ds shm_perm gid printf creator uid gid d d n ds shm_perm cuid ds shm_perm cgid else perror shmctl IPC_STAT else perror shmget return errno Example of Attaching a Shared Segment The program in Example 3 6 illustrates the process of actually attaching to and using a shared memory segment The segment must exist and is specified by its ID or by its key You can use the program in Example 3 5 to create a segment for this program to use 63 Chapter 3 Sharing Memory Between Processes 64 The attachment is either read write or read only depending on the presence of the r command parameter When the program attaches the segment read write it stores its own PID in the first word of the segment Run the program several times each time it reports the previous PID value and sets anew PID value This illustrates that the contents of the segment persist between uses of the segment You can use the w parameter to have the program wait after attaching This allows you to start more copies of the program so that multiple processes have attached the segment Example 3 6 shma
114. C_TIME January MON_2 LC_TIME February Locale Specific Behavior Table 14 9 continued Cultural Data Names Categories and Settings Item Category Setting for the C Locale MON_3 LC_TIME March MON_4 LC_TIME April MON_5 LC_TIME May MON_6 LC_TIME June MON_7 LC_TIME July MON_8 LC_TIME August MON_9 LC_TIME September MON_10 LC_TIME October MON_11 LC_TIME November MON_12 LC_TIME December ABMON_1 LC_TIME Jan ABMON_2 LC_TIME Feb ABMON_3 LC_TIME Mar ABMON_4 LC_TIME Apr ABMON_5 LC_TIME May ABMON_6 LC_TIME Jun ABMON_7 LC_TIME Jul ABMON_8 LC_TIME Aug ABMON_9 LC_TIME Sep ABMON_10 LC_TIME Oct ABMON_11 LC_TIME Nov ABMON_12 LC_TIME Dec RADIXCHAR LC_NUMERIC THOUSEP LC_NUMERIC a 321 Chapter 14 Internationalizing Your Application 322 Table 14 9 continued Cultural Data Names Categories and Settings Item Category Setting for the C Locale YESSTR LC_ALL yes NOSTR LC_ALL no CRNCYSTR LC_MONENTARY NLS Interfaces The NLS interfaces listed here are utilities and library functions NLS Utilities The list below identifies the minimum set of utilities that provide 8 bit transparency on all X Open compliant systems The definitions of these commands in terms of their syntax and parameters are not changed by the operation of NLS ar awk cancel cat cc cd cherp chmod chown cmp cp cpio date diff echo ed eg
115. Chapter 12 Distributed Process Parallelism 242 Table 12 1 continued Corresponding PVM and MPI Routines PVM Routine C Fortran MPI Routine C Fortran pom_halt pomfhalt pom_hostsync pumfhostsync pom_initsend pomfinitsend pom_joingrup pumfjoingroup pom_kill pomfkill pom_lvgroup pomflogroup pom_mcast pomfmcast pom_mkbuf pumfmkbuf pom_mstat pumfmstat pom_mytid pumfmytid pom_notify pumfnotify pom_nrecv pomfnrecv pom_pk pomfpack pom_parent pumfparent pom_perror pumfperror pom_precv pumfprecu pom_probe pumfprobe pom_psend pomfpsend pom_pstat pumfpstat pum_recv pomfreco pom_recuf no Fortran counterpart pom_reduce pumfreduce pom_reg_hoster no Fortran counterpart MPI_Wtime MPI_WTIME MPI_Send_init MPISEND_INIT MPI_Comm_group MPI_COMM_GROUP PVM routine is nonportable MPI_Group_free MPI_GROUP_FREE MPI_Buffer_attach MPI_BUFFER_ATTACH MPI_Init MPI_INIT followed by MPI_Comm_rank MPI_COMM_RANK PVM routine is nonportable MPI_Irecv MPI_IRECV MPI_Pack MPI_PACK MPI_Error_string MPI_ERROR_STRING MPI_Recv MPI_LRECV MPI_Iprobe MPI_IPROBE MPI_Bsend MPI_BSEND MPI_Recv MPI_LRECV PVM routine is nonportable MPI_Reduce MPI_REDUCE PVM routine is nonportable Comparing Library Routines Table 12 1 continued Corresponding PVM and MPI Routines PVM Routine C Fortran MPI Routine C Fortran pom_reg_rm no Fortran counterpart PVM routine is nonportable pom_reg_tas
116. Configuring the IPC Name Space 40 Listing and Removing Persistent Objects 40 Access Permissions 41 Choosing and Communicating Key Values 41 Using ID Numbers 41 Private Key Values 42 Using 4 2 BSD IPC 42 Sharing Memory Between Processes 43 Overview of Memory Sharing 43 Shared Memory Based on mmap 44 Sharing Memory Between 32 Bit and 64 Bit Processes 44 POSIX Shared Memory Operations 45 Creating a Shared Object 45 Shared Object Pathname 45 Shared Object Open Flags 46 Shared Object Access Mode 46 Using the Shared Object File Descriptor 46 Using a Shared Object 47 Example Program 47 IRIX Shared Memory Arenas 50 Overview of Shared Arenas 50 Initializing Arena Attributes 51 Creating an Arena 52 Joining an Arena 53 Restricting Access to an Arena 53 Arena Access From Processes in a Share Group 53 vii Contents Allocating in an Arena 54 Exchanging the First Datum 55 System V Shared Memory Functions 60 Creating or Finding a Shared Memory Segment 60 Attaching a Shared Segment 61 Managing a Shared Segment 61 Information About Shared Memory 62 Shared Memory Examples 62 Example of Creating a Shared Segment 62 Example of Attaching a Shared Segment 63 4 Mutual Exclusion 67 Overview of Mutual Exclusion 68 Test and Set Instructions 68 Locks 69 Semaphores 70 Condition Variables 71 Barriers 72 POSIX Facilities for Mutual Exclusion 73 Managing Unnamed Semaphores 73 Managing Named Semaphores 74 Creating a Named Semaphore 75 Closing
117. Font metric files are primarily used by text processing and desktop publishing programs to for example generate PostScript code for a specified document 272 Installing and Adding Font and Font Metric Files Creating Font Aliases If you do not want to use long X font names you can specify shorter aliases for those names Silicon Graphics uses a file called fonts alias to specify short aliases for fonts There can be a fonts alias file in an X font directory For example see the file fonts alias in the directory usr lib X11 fonts 100dpi A typical font alias looks like this fixed misc fixed medium r semicondensed 13 120 75 75 c 60 1s08859 1 This associates the short alias fixed to the longer name that follows it The alias file can also be used to specify alternate conventions for the component parts of a 14 part font name For example the following entry creates an alias that uses regular instead of medium for the weight component adobe utopia regular i normal 14 100 100 100 p 74 is08859 1 adobe utopia medium i normal 14 100 100 100 p 74 is08859 1 To specify your own font aliases in a font directory store them in a file called fonts alias local in that directory That way your entries do not disappear when you upgrade your system software Adding Font and Font Metric Files When you purchase a font or obtain a font that is in the public domain you need to add that font to
118. GETMUSTRUN_PID of a specified process MP_RUNANYWHERE Allow the calling process or a specified process to run MP_RUNANYWHERE_PID on any CPU The runon command see Process Creation on page 196 and runon 1 initiates the parent process of a program running on a specific CPU Any child processes also runs on that CPU unless the parent reassigns them to run anywhere or to run on a different CPU using sysmp The use of restricted CPUs and assigned CPUs to get predictable real time performance is discussed at length in the REACT Pro Real Time Programmer s Guide The syssgi function has a number of interesting uses but only one of interest for managing processes syssgi SGI_PROCSZ returns the virtual and resident memory occupancy of the calling process Using Multiple Processes Process Reaping A parent process should not terminate while its child processes continue to run When it does so the parent process of each child becomes 1 the init process This causes problems if a child process should loop or hang The functions you use to collect the technical term is to reap the status of child processes are summarized in Table 10 2 Table 10 2 Functions for Child Process Management Function Name Purpose and Operation wait 2 Function to block until a child stops or terminates and to receive the cause of its change of status waitpid 2 POSIX extension of wait which allows more selectivity and ret
119. Insight IRIS POWER C IRIS Showcase IRIS Performer TRIS 4D IRIX POWER CHALLENGE POWER CHALLENGEarray Power Fortran POWER Series REACT RealityEngine and WorkShop are trademarks of Silicon Graphics Inc MIPS MIPSpro R5000 and R10000 are trademarks and R4000 R4400 and R8000 are registered trademarks of MIPS Technologies Inc AT amp T is a trademark of AT amp T Inc POSIX is a registered trademark of the Institute of Electrical and Electronic Engineers Inc IEEE UNIX is a registered trademark in the United States and other countries licensed exclusively through X Open Company Ltd OSF Motif is a trademark of Open Software Foundation Inc The X Window System is a trademark of the Massachusetts Institute of Technology Ada is a registered trademark of Ada Joint Program Office U S Government Post It is a registered trademark of Minnesota Mining and Manufacturing PostScript and Display Postscript are registered trademarks of Adobe Systems Inc NFS is a registered trademark of Sun Microsystems Inc Speedo is a trademark of Bitstream Inc Topics in IRIX Programming Document Number 007 2478 004 Contents List of Examples xxi List of Figures xxiii List of Tables xxv About This Manual xxix What This Manual Contains xxix What You Should Know Before Reading This Manual Other Useful References xxx Obtaining Manuals xxxi Conventions Used in This Manual xxxi Process Address Space 3 Defining the Address Space 3 Ad
120. PC object or return the ID of one shmctl 2 Get the status of a shared memory segment change permissions or user IDs or lock or unlock a segment in memory shmat 2 Attach a shared memory segment to the address space shmdt 2 Detach a shared memory segment from the address space Creating or Finding a Shared Memory Segment A process creates a shared memory segment or locates an existing segment using the shmget system function When it creates a segment the arguments to this function establish e The numeric key of the segment e The size of the segment e The user ID and group ID of the segment creator and owner e The access permissions to the segment When the function locates an existing segment access to the segment is controlled by the access permissions and by the user ID and group ID of the calling process System V Shared Memory Functions Unlike an IRIX shared arena a shared segment does not grow automatically as it is used The size specified when it is created is fixed The shared segment is initialized to binary zero As implemented in IRIX the pages of the segment are created as they are first referenced see Mapping a Segment of Zeros on page 19 The value returned by shmget is the ID number of the segment It is used to identify the segment to other functions Attaching a Shared Segment The shmget function creates the segment or verifies that it exists but does not actually make it
121. PI Routines 241 Font and Font Metric Directories 271 Locale Categories 293 Category Environment Variables 294 Some Monetary Formats 308 ANSI Compatible Functions 313 X Open Additional Functions 314 Regular Expression Libraries in IRIX 317 Character Expressions in Internationalized Regular Expressions 318 Examples of Internationalized Regular Expressions 319 Cultural Data Names Categories and Settings 320 ISO 8859 Character Sets 362 Character Sets for Asian Languages 364 ISO 3166 Country Codes 367 xxvii About This Manual This manual discusses several topics of interest to programmers writing applications for the IRIX operating system on Silicon Graphics computers including memory management interprocess communication models of parallel computation file and record locking font access and internationalization What This Manual Contains This manual contains the following major parts Part I The Process Address Space tells how the virtual address space of a process is created and how objects are mapped into it Part II Interprocess Communication covers all the facilities for communicating and coordinating among processes such as semaphores shared memory signals message queues and file and record locks Part III Models of Parallel Computation gives an overview of the different ways you can specify parallel execution in Silicon Graphics systems Part IV Working With Fonts
122. Parallelism Creating Pthreads 212 The performance measurement tools of the Developer Magic package do not produce reliable results with a threaded program You create a pthread by calling pthread_create One argument to this function is a thread attribute object of type pthread_attr_t You pass a null address to request a thread having default attributes or you prepare an attribute object to reflect the features you want the thread to have You can use one attribute object to create many pthreads Functions related to attribute objects and pthread creation are summarized in Table 11 3 and described in the following text Table 11 3 Functions for Creating Pthreads Function Purpose pthread_attr_init 3P Initialize a pthread_attr_t object to default settings pthread_attr_setdetachstate 3P Set the automatic detach attribute in a pthread_attr_t object pthread_attr_setinheritsched 3P Specify whether scheduling attributes come from the attribute object or are inherited from the creating thread pthread_attr_setschedparam 3P Set the starting thread priority in a pthread_attr_t object pthread_attr_setschedpolicy 3P Set the scheduling policy in a pthread_attr_t object pthread_attr_setstacksize 3P Set the stack size attribute in a pthread_attr_t object pthread_attr_setstackaddr 3P Set the address of memory to use as a stack ina pthread_attr_t object when you allocate the stack for the new thread pthread_attr_destro
123. RY_CYCLECNTR argument Mapping a VME Device You can use mmap to create a segment that is a window on the bus address space of a particular VME bus adapter This allows you to do programmed I O PIO to VME devices To do PIO you create a file descriptor by opening one of the special devices in dev ume These files correspond to VME devices For details on the naming of these files see the usrvme 7 reference page The name of the device that you open and pass as the file descriptor determines the bus address space A16 A24 or A32 The values you specify in off and len must agree with accessible locations in that VME bus space A read or write to a location in the mapped segment causes a call to the read or write entry of the kernel device driver for VME PIO An attempt to read or write an invalid location in the bus address space causes a SIGBUS exception to all processes that have mapped the device Note On the CHALLENGE and Onyx hardware PIO reads and writes are asynchronous Following an invalid read or write as much as 10 milliseconds can elapse before the SIGBUS signal is raised For a detailed discussion of VME PIO see the IRIX Device Driver Programmer s Guide Mapping Segments of Memory Note Mapping of devices through mmap is an IRIX feature that is not defined by POSIX standard Do not use the POSIX shm_open function with device special files Choosing a Segment Address Normally there is no need to map
124. Removing Record Locks 165 Getting Lock Information 169 Deadlock Handling 172 Enforcing Mandatory Locking 172 xi Contents 10 xii Record Locking Across Multiple Systems 174 NFS File Locking 174 Configuring NFS Locking 175 Performance Impact 175 Models of Parallel Computation 179 Parallel Hardware Models 180 Parallel Programs on Uniprocessors 181 Types of Memory Systems 181 Single Memory Systems 181 Multiple Memory Systems 183 183 Parallel Execution Models 183 Process Level Parallelism 184 Thread Level Parallelism 185 Statement Level Parallelism 187 Distributed Computation Models 187 Message Passing Interface MPI Model 188 Portable Virtual Machine PVM Model 188 Statement Level Parallelism 189 Products for Statement Level Parallelism 189 Silicon Graphics Support 189 Products from Other Vendors 190 Creating Parallel Programs 190 Managing Statement Parallel Execution 191 Controlling the Degree of Parallelism 192 Choosing the Loop Schedule Type 193 Process Level Parallelism 195 Using Multiple Processes 195 Process Creation and Share Groups 196 Process Creation 196 Process Management 197 Process Reaping 199 Contents 11 Process Scheduling 199 Controlling Scheduling With IRIX and BSD Compatible Facilities 200 Controlling Scheduling With POSIX Functions 202 Self Dispatching Processes 203 Parallelism in Real Time Applications 205 Thread Level Parallelism 207 Overview of POSIX Threads 208 Compili
125. Silicon Graphics by telephone Inside the U S and Canada call 1 800 627 9307 In other countries call the U S telephone number 415 960 1980 and ask for extension 5 5007 Conventions Used in This Manual This manual uses the conventions and symbols shown in Table ii Table ii Typographical Conventions Type of Information Example of Typography Filenames and pathnames This structure is declared in usr include sys time h IRIX command names and options used in Update these variables with systune then build a normal text new kernel with autoconfig vf Names of program variables structures Global variable mainSema points to an IRIX and data types semaphore which has type usema_t Names of IRIX kernel functions library Use mmap to map an object into the address functions and functions in example code space and munmap to remove it xxxi About This Manual When complete lines of example code or commands are set off from normal text they are displayed as follows ipcrm s semid Parts of the code or command that need to be typed exactly as shown are displayed in a monospaced font Operands that need to be supplied by you are italicized xxxii PART ONE The Process Address Space Chapter 1 Tells how the virtual address space of a process is created under IRIX Lists the parts of the address space and their sources discusses memory mapping gives tips on cache management Chapter 1 Proce
126. Swedish Albanian Czech English German Hungarian Polish Rumanian Serbo Croatian Slovak Slovene Afrikaans Catalan Dutch English Esperanto German Italian Maltese Spanish Turkish Danish English Estonian Finnish German Greenlandic Lapp Latvian Lithuanian Norwegian Swedish Bulgarian Byelorussian English Macedonian Russian Serbo Croatian Ukrainian Arabic English see ISO 8859 6 specification English Greek see ISO 8859 7 specification English Hebrew see ISO 8859 8 specification Danish Dutch English Finnish French German Irish Italian Norwegian Portuguese Spanish Swedish Turkish Popular Encodings IRIX contains over 500 Latin 1 fonts as well as a few fonts for each of the other 8859 encoded character sets except 8859 6 and 8859 8 Currently IRIX contains no fonts for use with the 8859 6 or 8859 8 character sets To get the list of ISO 8859 fonts enter the following xlsfonts Or you can restrict the amount of output for example by typing xlsfonts 8859 2 To see the encoding use the xfd command For example xfd fn sgi screen medium r normal 9 90 72 72 m 60 is08859 1 For more information on xlsfonts and xfd and installing and using fonts refer to Chapter 13 Working With Fonts Asian Languages Asian languages are commonly ideographic and employ large numbers of characters for their representation For example Japanese and Korean ca
127. Topics in IRIX Programming Document Number 007 2478 004 CONTRIBUTORS Written by David Cortesi Arthur Evans Wendy Ferguson and Jed Hartman Edited by Christina Cary Production by Linda Rae Sande Engineering contributions by in alphabetical order Ivan Bach Greg Boyd Joe CaraDonna Srinivas Lingutla Bill Mannell Paul Mielke Huy Nguyen James Pitcairne Hill Paul Roy and Jonathan Thompson St Peter s Basilica image courtesy of ENEL SpA and InfoByte SpA Disk Thrower image courtesy of Xavier Berenguer Animatica 1996 Silicon Graphics Inc All Rights Reserved The contents of this document may not be copied or duplicated in any form in whole or in part without the prior written permission of Silicon Graphics Inc RESTRICTED RIGHTS LEGEND Use duplication or disclosure of the technical data contained in this document by the Government is subject to restrictions as set forth in subdivision c 1 ii of the Rights in Technical Data and Computer Software clause at DFARS 52 227 7013 and or in similar or successor clauses in the FAR or in the DOD or NASA FAR Supplement Unpublished rights reserved under the Copyright Laws of the United States Contractor manufacturer is Silicon Graphics Inc 2011 N Shoreline Blvd Mountain View CA 94043 1389 Silicon Graphics Indigo IRIS CHALLENGE Onyx Indy and OpenGL are registered trademarks and CASEVision Impressario Indigo Magic Inventor IRIS GL IRIS IM IRIS
128. _INT sbuff 1000 amp position MP I_COMM_ WORLD MPI_Pack data 100 MPI_FLOAT sbuff 1000 amp position MPI_COMM_ WORLD Send initial data to slave tasks msgtype 0 for i 0 i lt ntasks itt if i mytid MPI_Send sbuff position MPI_PACKED i msgtype MP I_COMM WORLD Wait for results from slaves msgtype 5 for i 0 i lt nproc it PI_Recv rbuff 1000 MPI_PACKED MPI_ANY SOURCE msgtype MPI_COMM_WORLD amp status position 0 PI_Unpack rbuff 1000 amp position amp who 1 MPI_INT MP I_COMM WORLD PI_Unpack rbuff 1000 amp position amp result who 1 MPI_FLOAT MPI_COMM WORLD printf I got Sf from d n result who who Program Finished Exit MPI before stopping MPI_Finalize MPMD in MPI Version Slave Task Note the use of the buffered sends in the slave task MPI version Using standard sends instead would lead to deadlock in MPI implementations that do not use buffering for standard sends include lt stdio h gt include lt mpi h gt float work int mytid int me int n float data int ntasks int master main int argc char argv int mytid my task id int me logical ordering among slaves int n i ntasks master msgtype float data 100 result Example Programs float work char rbuff 1000 sbuff 1000 int position PI_ Status stat
129. a 32 or 64 bit word from memory and also tags that cache line so that the hardware can recognize any change to memory from any CPU in a multiprocessor e The Store Conditional SC instruction stores a 32 or 64 bit word into memory provided that the destination cache line has not been modified If the cache line has been altered since the LL instruction was used SC does not update memory and sets a branch condition The combination of LL and SC can be used to guarantee that a change to a memory location is effective even when multiple concurrent CPUs are trying to update the same location You can use LL and SC only from an assembly language module However the IRIX kernel contains a family of services that are implemented using LL SC and you can call them from C or C These calls are discussed under Using Test and Set Functions on page 82 Overview of Mutual Exclusion Locks A lock is a small software object that stands for the exclusive right to use some resource The resource could be the right to execute a section of code or the right to modify a variable in memory or the right to read or write in a file or any other software operation that must by performed serially by one process at a time Before using a serial resource the program claims the lock and releases the lock when it is done with the resource The POSIX standard refers to an object of this kind as a mutex a contraction of mutual exclusion that is a
130. a character to upper case could be done by subtracting the difference between the code for a and the code for A Numeric characters could be identified by inspection if they fell between 0 and 9 they were numeric otherwise they weren t You could tell if a character was for instance printable a letter or a symbol by comparing to known encoding values Macros for such activity have long been available in ctype h but lots of programs did character arithmetic anyway Since character encoding and linguistic semantics are completely independent such arithmetic in an internationalized program leads to unpleasant results Furthermore characters exist outside of ASCII that break some non arithmetic assumptions Consider the German character which is a lowercase alphabetic character letter yet has no uppercase Consider also French as written in France where the uppercase of is E not Clearly the programmer of an internationalized application has no way of directly computing all the character associations that were available in English under ASCII The Solution Strict avoidance of arithmetic on character values should remove any trouble in this area The macros in ctype h are table driven and are therefore locale sensitive If you think of characters as abstract characters rather than as the numbers used to represent them you can avoid pitfalls in this area Locale Specific Behavior Regular Expressions XPG 4 specifies
131. a lock passed to fentl using the F_GETLK command is not blocked by another lock the _type field is changed to FLUNLCK and the remaining fields in the structure are unaffected Example 7 7 shows how to use this capability to print all the records locked by other processes Note that if several read locks occur over the same record only one of these is found 169 Chapter 7 File and Record Locking Example 7 7 This function takes a file descriptor all locks currently set on that file l_start field of the flock structure for the first lock that would block a of the file l_len 0 Detecting Contending Locks Using fcntl and prints a report showing The loop variable The function asks lock from l_start When no lock would block such a is the fcentl to the end lock the returned l_type contains F_UNLCK and the loop ends Otherwise the contending lock is displayed l_start is set to the end point of that lock and the loop repeats By A void printAllLocksOn int fd struct flock Lek Find and print write lock blocked segments of file void printf sysid pid type start length n lck l_whence 0 lck l_start OL lck l_len OL for lck 1l_type 0 lck l_type F_UNLCK lck l_type F_WRLCK void fentl fd F_GETLK amp lck if lck l_type F_UNLCK void printf 5d 5d c 8d S8d n lck l_sysid ilck 1l_pid lck 1l_type F_WRLCK W
132. a or makes too many nested function calls it will attempt to modify memory outside the stack space This might cause a segmentation fault if that memory is not allocated or it might modify memory used for other purposes Tip When you preallocate stack space you can create red zones around the allocated stacks as follows e Allocate the stack memory in multiples of the system page size aligned on page boundaries see the getpagesize 2 and memalign 3C reference pages e Allocate an extra page of memory above and below each stack area e Use the mprotect function to set the protection of the extra pages to PROT_NONE see the mprotect 2 reference page This procedure creates untouchable pages at each end of the stack area If the thread misuses its stack it will usually terminate at once with a segmentation fault It is still possible for a thread to call a function that allocates more than a page of automatic variables and so skips over the red zone to modify memory beyond it Executing and Terminating Pthreads Caveats Regarding Stack Space Because thread stack space is taken from dynamic memory the allocation is charged against the process virtual memory limit not the process stack size limit as you might expect see the getrlimit 2 reference page for information on resource limits The stack segment of a process is extended automatically up to a large system limit as necessary The stack segment of a pth
133. a part of the process address space That remains to be done with a call to shmat attach passing the identifier returned by shmget You can pass a desired base address to shmat or you can pass NULL to have the system select the base address It is best to let the system choose the base this ensures that all processes have the same base address for the segment A process can detach a segment from its address space by calling shmdt Managing a Shared Segment The shmctl function gives you the ability to get information about a segment or to modify its attributes These operations are summarized in Table 3 7 Table 3 7 SVR4 Shared Segment Management Operations Keyword Operation Can Be Used By IPC_STAT Get information about the segment Any process having read access IPC_SET Set owner UID owner GID or access Creator UID owner UID or permissions superuser IPC_RMID Remove the segment from the IPC Creator UID owner UID or name space superuser SHM_LOCK Lock the segment pages in memory Superuser process only SHM_UNLOCK Unlock a locked segment Superuser process only 61 Chapter 3 Sharing Memory Between Processes Information About Shared Memory The information structure returned by shmctl IPC_STAT is declared in the sys shm h header file The first field shm_perm is an ipc_perm structure This structure is declared in the sys ipc h header file Shared Memory Examples The example pr
134. a queue creating itifit mq_open 3 msgget 2 does not exist Query attributes of a queue and mq_getattr 3 msgctl 2 number of pending messages Change attributes of a queue mq_setattr 3 msgctl 2 Give up access to a queue mq_close 3 n a Remove a queue from the system mq_unlink 3 rm 1 msgctl 2 iperm 1 128 Overview of Message Queues Table 6 1 continued Abstract Operations on a Message Queue Operation POSIX Function SVR4 Function Send a message to a queue mq_send 3 msgsnd 2 Receive a message from a queue mq_receive 3 msegrcv 2 Request asynchronous notification ofa maq_notify 3 n a message arriving at a queue Both implementations can be used to communicate between POSIX threads and between IRIX processes in any combination Besides obvious features of syntax the principal differences between the two implementations are as follows e POSIX functions are implemented as library functions in the libc library and operate primarily in the user process address space SVR4 functions are implemented in the kernel and every operation requires a context switch e The identity of either a POSIX or an SVR4 queue is retained over a reboot The contents of a POSIX queue might or might not survive a reboot but you cannot depend on either type of queue to retain its state after the last program closes it e POSIX allows you to set a limit on the number of messages and the size of one message SVR4 allows y
135. a segment to any particular virtual address You specify addr as 0 and IRIX picks an unused virtual address This is the usual method and the recommended one You can specify a nonzero value in addr to request a particular base address for the new segment You specify MAP_FIXED in flags to say that addr is an absolute requirement and that the segment must begin at addr or not be created If you omit MAP_FIXED mmap takes a nonzero addr as a suggestion only Segments at Fixed Offsets In rare cases you may need to create two or more mapped segments with a fixed relationship between their base addresses This would be the case when there are offset values in one segment that refer to the other segment as diagrammed in Figure 1 1 Offset A v Offset S Figure 1 1 Segments With a Fixed Offset Relationship In Figure 1 1 a word in one segment contains an offset value A giving the distance in bytes to an object in a different mapped segment Offset A is accurate only when the two segments are separated by a known distance offset S 21 Chapter 1 Process Address Space 22 You can create segments in such a relationship using the following procedure 1 Map a single segment large enough to encompass the lengths of all segments that need fixed offsets Use 0 for addr allowing IRIX to pick the base address Let this base address be B 2 Map the smaller segments over the larger one For the fir
136. ables 316 Language Information 316 Using Regular Expressions 317 Internationalized Regular Expressions 318 Cultural Data 320 NLS Interfaces 322 NLS Utilities 322 NLS Library Functions 323 XSI Curses Interface 323 Strings and Message Catalogs 324 xvii Contents XPG 4 Message Catalogs 324 Opening and Closing XPG 4 Catalogs 324 Using an XPG 4 Catalog 325 XPG 4 Catalog Location 326 Creating XPG 4 Message Catalogs 326 Compiling XPG 4 Message Catalogs 327 SVR4 MNLS Message Catalogs 328 Putting MNLS Strings Into a Catalog 328 Using MNLS in Shell Scripts 328 Specifying MNLS Catalogs 329 Getting Strings From MNLS Message Catalogs 329 Using pfmt 330 Labels Severity and Flags 330 Format Strings for pfmt 331 Using fmtmsg 331 Internationalizing File Typing Rule Strings With MNLS 332 Variably Ordered Referencing of printf Arguments 333 Internationalization Support in X11R6 335 Limitations of X11R6 in Supporting Internationalization 335 Vertical Text 336 Character Sets 336 Xlib Interface Change 336 Resource Names 337 Getting X Internationalization Started 337 Initialization for Toolkit Programming 337 Initialization for Xlib Programming 337 Fontsets 338 Example EUC in Japanese 338 Specifying a Fontset 338 Creating a Fontset 339 Using a Fontset 339 Text Rendering Routines 340 New Text Extents Functions 340 xviii Contents Internationalization Support in Motif 342 User Input 343 About User Input and Input Methods 343
137. ad_mutex_lock amp amp lp gt mutList lock list to prevent races ep gt busyFlag 0 pthread_cond_signal amp ep gt notBusy pthread_mutex_unlock amp lp gt mutList Public function to delete a list element returned by getFromList Ef void deleteInList listHead_t lp element_t ep element_t epp assert ep gt busyFlag pthread_mutex_lock amp lp gt mutList for epp amp lp gt head ep epp epp amp epp gt next finding anchor of ep in list xepp ep gt next remove ep from list ep gt busyFlag 0 pthread_cond_broadcast amp ep gt notBusy pthread_mutex_unlock amp lp gt mutList pthread_cond_destroy amp ep gt notBusy free ep The functions in Example 11 6 implement part of a simple library for managing lists In a list head mutList is a mutex object that represents the right to modify any part of the list The elements of a list can be busy that is in use by some thread An element that is busy has a nonzero busyFlag field The getFromList function looks up an element in a specified list makes that element busy and returns it The function begins by acquiring the list mutex This ensures that the list cannot change while the function is searching the list and makes it legitimate for the function to change the busy flag in an element 233 Chapter 11 Thread Level Parallelism 234 When it finds the element the f
138. ains the following main topics e Overview of POSIX Threads on page 208 summarizes the similarities and differences of pthreads and processes e Compiling and Debugging a Pthread Application on page 209 covers compiling and debugging tools e Creating Pthreads on page 212 covers the process of creating a pthread with the desired attributes e Executing and Terminating Pthreads on page 215 discusses how threads initialize themselves and how you synchronize on thread termination e Using Thread Unique Data on page 219 tells how to define variables that have a unique value in each thread e Pthreads and Signals on page 221 discusses the pthread specific details of signal handling see Signals on page 104 for the general information e Scheduling Pthreads on page 223 covers scheduling priorities and policies e Synchronizing Pthreads on page 226 details the use of mutexes and condition variables 207 Chapter 11 Thread Level Parallelism Overview of POSIX Threads 208 A thread is an independent execution state that is a set of machine registers a call stack and the ability to execute code When IRIX creates a process it also creates one thread to execute that process However you can write a program that creates many more threads to execute in the same address space For a comparison of pthreads to processes see Thread Level Parallelism on page 185 POSIX
139. alization includes these standards compliant features among others ANSI C and POSIX ISO 9945 1 Locale X OPEN Portability Guide Issue 4 XPG 4 XPG 4 message catalogs interpretation of locale strings UNIX System V Release 4 Multi National Language Support MNLS message catalogs X11R5 and X11R 6 Input methods text rendering resource files Internationalizing Your Application The Basic Steps To internationalize your icon follow these steps 1 2 3 4 Call setlocale as soon as possible to put the process into the desired locale See Setting the Current Locale on page 292 for instructions Make your application 8 bit clean An application is 8 bit clean if it does not use the high bit of any data byte to convey special information See Eight Bit Cleanliness on page 299 for instructions If you re writing a multilingual application you must do one of two things e fork and then call setlocale differently in each process e call setlocale repeatedly as necessary to change from language to language See Multilingual Support on page 297 for more information Use wide character WC or multibyte MB characters and strings to allow for more than one byte per character this is needed for Asian languages which often require two or even four bytes per character See Character Representation on page 300 for more information 289 Chapter 14 Internationalizing Your Application
140. am requires maintenance you make the necessary logic changes and simultaneously remove any assertions about the changed code unless you are certain that the assertions are still true of the modified logic Then repeat the preceding procedure from step 2 Managing Statement Parallel Execution The run time library for each of the languages uses IRIX lightweight processes to implement parallel execution see Chapter 10 Process Level Parallelism When a parallel program starts the run time support creates a pool of lightweight processes using the sproc function Initially the extra processes are blocked while one process executes the opening passage of the program When execution reaches a parallel section the run time library code unblocks as many processes as necessary Each process begins to execute the same block of statements The processes share global variables while each allocates its own copy of variables that are local to one iteration of a loop such as a loop index 191 Chapter 9 Statement Level Parallelism 192 When a process completes its portion of the work of that parallel section it returns to the run time library code where it picks up another portion of work if any work remains or suspends until the next time it is needed At the end of the parallel section all extra processes are suspended and the original process continues to execute the serial code following the parallel section Controlling the
141. ames and abbreviations see Appendix A ISO 3166 Country Names and Abbreviations You can find detailed information about fonts in Chapter 13 Working With Fonts Also you can find additional information about internationalizing an application in the Indigo Magic Desktop Integration Guide Internationalized software can be made to produce output in a user s native language to format data such as dates and currency values according to the user s local customs and to otherwise make the software easier to use for users from a culture other than that of the original software developer As computers become more widely used in non American cultures it becomes increasingly important that developers stop relying on the conventions of American programming and the English language in their programs This chapter provides information on how to make your applications more widely accessible This section presents the following topics e Some Definitions covers locales internationalization localization nationalized software and multilingual software e Areas of Concern in Internationalizing Software points out a few concerns to watch for when internationalizing your software e Standards covers standard compliant features e TInternationalizing Your Application The Basic Steps lists the procedures to use when internationalizing an icon e Additional Reading on Internationalization provides references
142. ames of data files containing pictographs or in whatever manner the developer thinks best so long as the developer provides a way for the localizer to produce and deliver localized pictographs This section discusses three encodings that are commonly used e The ISO 8859 Family explains the ISO 8859 family of encodings e Asian Languages describes Asian language encodings e TSO 10646 and Unicode covers the ISO 10646 and Unicode 361 Chapter 14 Internationalizing Your Application 362 The ISO 8859 Family American English is easily representable in 7 bit ASCII Most other languages are not For example the character is not in ASCII Most Western European languages are representable in 8 bit ISO 8859 1 which is commonly known as Latin 1 Latin 1 is a superset of ASCII that includes characters used by several Western European languages such as 6 2 ISO 8859 comes in nine parts many of which overlap all are supersets of ASCII The ISO 8859 Character Sets are shown in Table 14 10 Table 14 10 ISO 8859 Character Sets Character Set 8859 1 8859 2 8859 3 8859 4 8859 5 8859 6 8859 7 8859 8 8859 9 Common Name Latin 1 Latin 2 Latin 3 Latin 4 Latin Cyrillic Latin Arabic Latin Greek Latin Hebrew Latin 5 Languages Supported Danish Dutch English Faeroese Finnish French German Icelandic Irish Italian Norwegian Portuguese Spanish
143. amic Allocation of POSIX Unnamed Semaphore sem_t allocUnnSem unsigned initVal sem t psem sem_t malloc sizeof sem_t if semt malloc worked if sem_init psem 0 initVal free psem psem NULL return psem The function in Example 4 1 passes the second argument of sem_init pshared as 0 meaning the semaphore can only be used within the current process A semaphore of this kind can be used to coordinate pthreads in a threaded program If you want to use a semaphore to coordinate between IRIX processes with separate address spaces you must create the semaphore with a nonzero pshared and place the semaphore in a memory segment that is shared among all processes This feature is fully supported However you should specify pshared as 0 when possible because nonshared semaphores have higher performance Managing Named Semaphores A named semaphore is named in the filesystem so it can be opened by any process subject to access permissions even when the process does not share address space with the creator of the semaphore The functions used to create and manage named semaphores are summarized in Table 4 2 Table 4 2 POSIX Functions to Manage Named Semaphores Function Name Purpose and Operation sem_open 3 Create or access a named semaphore returning an address sem_close 3 Give up access to a named semaphore releasing a file descriptor sem_unlink 3 Permanently remove a named
144. ample 4 2 Using Compare and Swap on a LIFO Queue 84 Example 4 3 Program to Demonstrate semget 92 Example 4 4 Program to Demonstrate semctl for Management 94 Example 4 5 Program to Demonstrate semctl for Sampling 96 Example 4 6 Program to Demonstrate semop 98 Example 5 1 Example of POSIX Time Functions 121 Example 6 1 Program to Demonstrate mq_getattr and mq_setattr 135 Example 6 2 Program to Demonstrate mq_open 136 Example 6 3 Program to Demonstrate mq_send 138 Example 6 4 Program to Demonstrate mq_receive 140 Example 6 5 Program to Demonstrate msgget 148 Example 6 6 Program to Demonstrate msgctl 150 Example 6 7 Program to Demonstrate msgsnd 152 Example 6 8 Program to Demonstrate msgrcv 154 Example 7 1 Opening a File for Locked Use 161 Example 7 2 Setting a Whole File Lock With fentl 163 Example 7 3 Setting a Whole File Lock With lockf 164 Example 7 4 Setting a Whole File Lock With flock 165 xxi List of Examples xxii Example 7 5 Example 7 6 Example 7 7 Example 7 8 Example 7 9 Example 10 1 Example 11 1 Example 11 2 Example 11 3 Example 11 4 Example 11 5 Example 11 6 Example 14 1 Example 14 2 Example 14 3 Example 14 4 Example 14 5 Example 14 6 Example 14 7 Example 14 8 Example 14 9 Example 14 10 Example 14 11 Example 14 12 Example 14 13 Record Locking With Promotion Using fcntl 166 Record Locking Using lockf 168 Detecting Contending Locks Using fentl 170 Testing for
145. an create a new process for each unit of work that your program could do in parallel The processes can share the address space of the original program or each can have its own address space You design the processes so that they coordinate work and share data using any and all of the interprocess communication IPC features discussed in Part II Interprocess Communication Software products from Silicon Graphics use process level parallelism For example the IRIS Performer graphics library normally creates a separate lightweight process to manage the graphics pipe in parallel with rendering work The run time library for statement level parallelism creates a pool of lightweight processes and dispatches them to execute parts of loop code in parallel see Managing Statement Parallel Execution on page 191 195 Chapter 10 Process Level Parallelism 196 Process Creation and Share Groups The most important system functions you use to create and manage processes are summarized in Table 10 1 Table 10 1 Commands and System Functions for Process Management Function Name Purpose and Operation npri 1 Command to run a process at a specified nondegrading priority runon 1 Command to run a process on a specific CPU fork 2 Create a new process with a private address space pcreate 3C Create a new process with a private address space running a designated program with specified arguments sproc 2 Create a new proc
146. any IRIX shared memory arena The arena address u is not actually used by the functions However the functions cannot work until usinit has been called at least once Passing an arena address ensures that this has happened 83 Chapter 4 Mutual Exclusion 84 Use a compare and swap function in a loop like the following 1 Copy the current value of the target memory field 2 Calculate a new value based on the current value 3 Use compare and swap to install the new value provided that the current value has not changed during step 2 4 If the compare failed so the swap was not done uscas returns 0 another process has changed the target return to step 1 and repeat The code in Example 4 2 illustrates how this type of loop can be used to manage a simple LIFO queue Example 4 2 Using Compare and Swap on a LIFO Queue include lt ulocks h gt typedef struct item_s struct item_s next other fields s s item_t void push_item item_t lifo item_t new usptr_t u item t old do new gt next old lifo while 0 uscas lifo ptrdiff_t old ptrdiff_t new u item t pull_item item_t lifo usptr_t u item_t old new do old lifo if old break new old gt next while O uscas lifo ptrdiff_t old ptrdiff_t new u return old include lt stdio h gt main usptr_t arena usinit var tmp cas arena item_t lifo NULL item_t
147. aphical or mathematical representation of a glyph Letters digits punctuation marks mathematical symbols and cursors are examples of glyphs Font A font is a set of characters that is a set of representations of characters In a bitmap font the shape of each character is represented by a rectangular array of bit values 1 or 0 forming a bitmap of the shape In an outline font the shape of a character is represented by a mathematical description of its outline A distinction exists between a base and composite font A base font is a set of characters of the same size and style Characters in a base font usually match one another in size style weight and slant because their shape size position and spacing have been carefully designed by a skilled font designer A composite font is composed of base fonts with various attributes for example roman and italic or book weight and semibold Font Family or Typeface A professional font designer usually creates an entire font family or typeface composed of a variety of base fonts with related forms rather than a single font A base font family or typeface is a set of base fonts with the same style or design A composite font family or composite typeface is composed of base font families A base font family can consist of bitmap fonts in certain sizes a scalable font that can be used to produce bitmap fonts in different sizes or both 263 Chapter 13 Working With Fonts 264
148. aphics hardware cycle counter always increases at a steady rate However the cycle counter has a limited precision that depends on the hardware You can use the syssgi system function to find out the precision of the cycle counter see syssgi 2 and look for the SGI_CYCLECNTR_SIZE option Using Interval Timers You create an interval timer object by calling timer_create To this function you pass codes that specify the time base to use and the signal to send upon timer expiration It returns an ID value to identify the timer to other functions The time base for a timer is either CLOCK_REALTIME or CLOCK_SGI_FAST the latter is anonportable request Typically CLOCK_SGI_FAST has finer resolution but you can verify that using the clock_getres function as shown in Example 5 1 123 Chapter 5 Signalling Events 124 You also pass a sigevent_t object to timer_create In it you would normally set the following values sigev_notify SIGEV_SIGNAL to have the timer generate a signal on expiration sigev_signo The signal number you want sent possibly selected from the POSIX real time range for example SIGRTMIN 1 sigev_value sival_int An extra value to be passed to the signal handling function or sigev_value sival_ptr to sigwait when the signal is delivered You can pass a NULL instead of the address of a sigevent_t In that case the timer signals with a SIGALRM Initially a timer is disarmed inactive You start a ti
149. are created Using plock you specify whether to lock text data or both When you specify the text option the function locks all executable text as loaded for the program including shared objects DSOs It does not lock segments created with mmap even when you specify PROT_EXEC to mmap Use mlock or mpin to lock executable mapped segments When you specify the data option plock locks the default data heap and stack segments and any mapped segments made with MAP_PRIVATE as they are defined at the time of the call If you extend these segments after locking them the newly defined pages are also locked as they are defined Although new pages are locked when they are defined you still should extend these segments to their maximum size while initializing the program The reason is that it takes time to extend a segment the kernel must process a page fault and create a new page frame possibly writing other pages to backing store to make space One way to ensure that the full stack is created before it is locked is to call plock from a function like the function in Example 1 2 Example 1 2 Function to Lock Maximum Stack Size define MAX_STACK_DEPTH 100000 your best guess int call_plock char dummy MAX_STACK_DEPTH return plock PROCLOCK Locking and Unlocking Pages in Memory The large local variable forces the call stack to what you expect will be its maximum size before plock is entered
150. arg free arg One time initializing function called through pthread_once to create the perThreadKey xf void createPerThreadKey void pthread_key_create amp perThreadKey deletePerThread Return the address of this thread s instance of perThread_t Create the struct if necessary Create the key if necessary Ay struct perThreadInfo getPerThread void perThread_t ppt int ret pthread_once amp makePerThreadKey createPerThreadKey Pthreads and Signals ppt pthread_getspecific perThreadKey if NULL ppt ppt perThread_t malloc sizeof perThread_t initialize fields of ppt gt new per thread struct ret pthread_setspecific perThreadKey void ppt if ret perror pthread_setspecific return ppt The code in Example 11 3 includes the following functions and global variables perThreadKey The key that represents the class of perThread_t structures makePerThreadKey A pthread_once_t variable used to ensure that pthread_key_create is called only once deletePerThread Destructor function passed to pthread_key_create called when any thread terminates leaving a non NULL value under the perThreadKey key createPerThreadKey Function called via pthread_once to create perThreadKey getPerThread Function that can be called from any thread to retrieve that thread s value of p
151. as the LEGEND LEGEND 7 Archive 8mm Tape Drive This entry uses line 7 from the uxsgidesktop catalog if available Otherwise Archive 8mm Tape Drive is used The next example MENUCMD mycatalog 9 Eject Tape usr sbin eject dev tap displays line 9 from mycatalog if available Otherwise Eject Tape is displayed on the menu that pops up when you click an icon that uses this FTR You can internationalize strings in the command part of MENUCMD and CMD rules by using gettxt or any other convenient policy detailed in this section For example CMD OPEN xconfirm t Tape tool not available can be internationalized to CMD OPEN xconfirm t gettxt mycatalog 376 Tape tool not available Strings and Message Catalogs In this example gettxt is invoked to access line 376 from the catalog mycatalog and the string returned by gettxt is passed to xconfirm for display If line 376 from mycatalog is not accessible then gettxt returns the string Tape tool not available For more information about FTRs see the Indigo Magic Desktop Integration Guide Variably Ordered Referencing of printf Arguments printf and its variants can now refer to arguments in any specified order Consider the following scenario an application has chosen house from a list of objects and white from a list of colors The application wishes to display this choice The code might look l
152. at is groups whose membership can change dynamically at any time during a computation MPI does not support dynamic process groups MPI does not provide a mechanism to build a group from scratch but only from other groups that have been defined previously Closely related to groups in MPI are communicators which specify the communication context for a communication operation and an ordered process group that shares this communication context The chief difference between PVM groups and MPI communicators is that any PVM task can join leave a group independently whereas in MPI all communicator operations are collective A PVM task can add or delete a host from the virtual machine thereby dynamically changing the number of machines a program runs on This is not available in MPI A PVM program or any of its tasks can request various kinds of information from the PVM library about the collection of hosts on which it is running the tasks that make up the program and a task s parent The MPI library does not provide such calls Some of the collective communication calls in PVM for instance pym_reduce are nonblocking The MPI collective communication routines are not required to return as soon as their participation in the collective communication is complete PVM provides two methods of signaling other PVM tasks sending a UNIX signal to another task and notifying a task about an event from a set of predefined events by sending it a
153. at the time the signal was delivered The ucontext_t is detailed in the ucontext 5 reference page Alternatively your signal handler can have this prototype void name int sig int code struct sigcontext sc The second argument gives some added information about the signal see signal 5 fora list of codes The third argument a pointer to a sigcontext_t object gives the machine state at the time the signal was delivered in slightly different form from the ucontext_t When you use sigaction to set up a signal handler you pass an argument structure containing option flags that affect the treatment of the signal SA_SIGINFO SA_ONSTACK SA_RESETHAND SA_NODEFER SA_RESTART When set you are specifying asynchronous handling and your handler uses the POSIX prototype Its address is passed in the sa_sigaction structure field When not set a handler uses the older prototype and its address is passed in sa_handler When set your handler is called using alternate stack memory you have previously assigned with sigaltstack Otherwise the handler uses the stack of the process or thread stack executing at the time of the signal When set the policy for this signal is reset to the default when your handler is called Your handler is expected to reestablish the action if that is desired When not set the signal is automatically blocked while your handler executes and unblocked when your handler returns When set the same
154. atopen ispunct sscanf vsprintf fprint isspace streoll fscanf isupper strerror gcvt nl_langinfo strftime isalnum perror strtod isalpha printf strxfrm iscntrl regexp tolower Also all functions defined in the X Open Portability Guide Volume 2 XSI System Interfaces and Headers and X Open Portability Guide Volume 3 XSI Curses Interface provide 8 bit transparency on X Open compliant systems XSI Curses Interface The XSI curses interface is internationalized For more information see the X Open Portability Guide Volume 3 XSI Curses Interface 323 Chapter 14 Internationalizing Your Application Strings and Message Catalogs 324 Message catalogs are compiled databases of strings While a major role of message catalogs is to provide communications text in locale specific natural language the strings can be used for any purpose The idea is that an application uses only strings from a catalog thus allowing localizers to supply catalogs suitable for a given locale Two different and incompatible interfaces to message catalogs exist in IRIX MNLS and XPG 4 Developers working on SVR4 or other AT amp T code or related base system utilities probably use MNLS Developers working on independent projects probably use XPG 4 Neither is a solid standard but XPG 4 is closer to being a standard than MNLS Thus applications developers who have to choose between the two interfaces are encou
155. b m cx permissions nt strtoul optarg NULL 0 message size size int strtoul optarg NUI max messages msg int strtoul optarg NULI use O_CREAT O_ CREAT use O_EXCL O_EXCL nknown or missing argument c first non option argument return 1 137 Chapter 6 Message Queues 138 mqd mq_open path oflags perms amp buf if 1 mqd if mq_getattr mqd amp buf printf flags 0x x maxmsg d msgsize d curmsgs d n buf mq_flags buf mq_maxmsg buf mq_msgsize buf mq_curmsgs else perror mq_getattr else perror mq_open Example of mq_send The mq_send program in Example 6 3 allows you to send from 1 to 9999 messages to a queue from the command line The following command line arguments are accepted path The file pathname of the queue must be given following all options b bytes Size of each message for example b 0x200 c count Number of messages to send The default is 1 p priority Numeric priority of message to send Numbers from 0 to 32 are allowed by mq_send n Use the O_NONBLOCK flag with mq_open The count argument is limited to 99 999 so that the message text will not exceed 32 bytes the arbitrary minimum message size the program defines Example 6 3 Program to Demonstrate mq_send Program to test mq send 3 mq_send p lt priority gt b lt bytes gt
156. begin execution Barriers are part of IRIX IPC and require the use of a shared arena Barriers cannot be used to coordinate POSIX threads POSIX Facilities for Mutual Exclusion POSIX Facilities for Mutual Exclusion The POSIX real time extensions detailed in IEEE standard 1003 1b include named and unnamed semaphores The POSIX threads library detailed in IEEE standard 1003 1c introduces mutexes and condition variables Managing Unnamed Semaphores An unnamed semaphore is a semaphore object that exists in memory only An unnamed semaphore can be identified only by its memory address so it can be shared only by processes or threads that share that memory location The functions for creating and freeing unnamed semaphores are summarized in Table 4 1 Table 4 1 POSIX Functions to Manage Unnamed Semaphores Function Name Purpose and Operation sem_init 3 Initialize a semaphore object setting its value and preparing it for use sem_destroy 3 Make a semaphore unusable The type of a POSIX semaphore is sem_t which is declared in the header file semaphore h You create an unnamed semaphore by allocating memory for a sem_t variable either dynamically or statically and initializing it with sem_init The function in Example 4 1 allocates and initializes an unnamed semaphore and returns its address It returns NULL if there is a failure of either malloc or sem_init 73 Chapter 4 Mutual Exclusion Example 4 1 Dyn
157. bjects Signal Numbers IRIX supports the following 64 signal numbers 1 31 Same meanings as SVR4 and BSD see Table 5 1 32 Reserved by IRIX kernel 33 48 Reserved by the POSIX standard for system use 49 64 Reserved by POSIX for real time programming Signals with smaller numbers have priority for delivery The low numbered BSD compatible signals which include all kernel produced signals are delivered ahead of real time signals and signal 49 takes precedence over signal 64 Signals Table 5 1 is reproduced from the signal 5 reference page for convenience Table 5 1 Signal Numbers and Default Actions Symbolic Numeric Name Value Default Action Normal Meaning SIGHUP 1 Terminate Controlling terminal disconnect see termio 7 SIGINT 2 Terminate Interrupt key signal from controlling terminal see termio 7 SIGQUIT 3 Terminate and dump Quit key signal from controlling terminal see termio 7 SIGILL 4 Terminate and dump Attempt to execute illegal instruction SIGTRAP 5 Terminate and dump Trace breakpoint reached see proc 4 SIGABRT 6 Terminate and dump Abort SIGEMT 7 Terminate and dump Emulation trap SIGFPE 8 Terminate and dump Arithmetic exception see math 3M sigfpe 3C and matherr 3M SIGKILL 9 Terminate Kill request from software or user SIGBUS 10 Terminate and dump Bus error hardware exception SIGSEGV 11 Terminate and dump Segmentation fault illegal address SIGSYS 12 Terminate and dump Invali
158. braries owing for example to the concept of dynamic groups in PVM Hence the process of converting a PVM program into an MPI program can be straightforward or complicated depending on the particular PVM calls in the program and how they are used For many PVM programs conversion is straightforward In addition to a message passing library PVM also provides the concept of a parallel virtual machine session A user starts this session before invoking any PVM programs in other words PVM provides the means to establish a parallel environment from which a user invokes a parallel program Additionally PVM includes a console which is useful for monitoring and controlling the states of the machines in the virtual machine and the state of execution of a PVM job Most PVM console commands have corresponding library calls The MPI standard does not provide mechanisms for specifying the initial allocation of processes to an MPI computation and their binding to physical processors Mechanisms to do so at load time or run time are left to individual vendor implementations However this difference between the two paradigms is not by itself significant for most programs and should not affect the port from PVM to MPI Differences Between PVM and MPI The chief differences between the current versions of PVM and MPI libraries are as follows PVM supports dynamic spawning of tasks whereas MPI does not PVM supports dynamic process groups th
159. ce page You can display semaphore sets from the command line using ipcs and remove them with ipcrm see the ipcs 1 and ipcr 1 reference pages 87 Chapter 4 Mutual Exclusion 88 Creating or Finding a Semaphore Set A process creates a semaphore set or locates an existing set using the semget system function The function creates a set only if the specified key is IPC_PRIVATE or no set with that key exists and the IPC_CREAT flag is used When it creates a set the arguments to the function establish e the numeric key of the set e the number of semaphores in the set from 1 to 25 e the access permissions to the set In addition the effective user ID and group ID of the calling process become the creator and owner identification of the new semaphore set See Example Uses of semget on page 91 for example code When semget locates an existing set access is controlled by the access permissions of the set and by the user ID and group ID of the calling process The value returned by semget is the ID number of the semaphore set It is used to identify the segment to other functions Managing Semaphore Sets The semctl function gives you the ability to get information about a semaphore set or to modify its attributes These operations are summarized in Table 4 12 Table 4 12 SVR4 Semaphore Set Management Operations Keyword Operation Can Be Used By IPC_STAT Get information about the set Any process ha
160. cess which is associated with only one locale at any given time However the application can switch back and forth between locales as it switches between users so the four users may each use a different locale e Ina sophisticated editing system with a complex user interface a user may wish to operate the interface in one language while entering or editing text in another For instance a user whose first language is German may wish to compose a Japanese document using Japanese input and text manipulation but with the user interface operating in German There is no standard interface for such behavior In writing a multilingual application the first task is identifying the locales for the program to run in and when they apply There is no standard method for performing this task Once the application has chosen the desired locales it must do one of the following e fork and then call setlocale differently in each process e call setlocale repeatedly as necessary to change from language to language Misuse of Locales The LANG environment variable and the locale variables provide the freedom to configure a locale but they do not protect the user from creating a nonsensical combination of settings For example you are allowed to set LANG to fr French and LC_COLLATE to ja_JP EUC Japanese In such a case string routines would assume text encoded in 8859 1 except for the sorting routines which might assume French text and Ja
161. char argv mqd_t mqd queue descriptor struct mq_attr obuf output attr struct for getattr if argc lt 2 printf A pathname of a message queue is required n return 1 mgqd mq_open argv 1 O_RDONLY 135 Chapter 6 Message Queues if 1 mqd if mq getattr mqd amp obuf printf flags 0x x maxmsg d msgsize d curmsgs d n obuf mq_flags obuf mq maxmsg obuf mq_msgsize obuf mq_curmsgs else perror mq_getattr else perror mq_open Example of mq_open The program mg_open in Example 6 2 allows you to create a message queue from the command line The following command line arguments are supported path The file pathname of the queue must be given following all options p perms Access permissions to set for example p 0664 b bytes The maximum message size this queue allows for example b 256 m msgs The maximum number of messages that can be pending on this queue for example m 64 c Use the O_CREAT flag to create the queue if it doesn t exist x Use the O_EXCL flag to require that the queue not exist Example 6 2 Program to Demonstrate mq_open Program to test mq_open 3 mq_open p lt perms gt b lt bytes gt m lt msgs gt c x lt path gt p lt perms gt access mode to use when creating default 0600 b lt bytes gt maximum message size to set default MQ_DEF_MSGSIZE m lt msgs gt maximum
162. cify the desired length as len and the starting offset as off You can remap a file to a different segment by calling mmap again In this way you can use the off parameter of mmap as the logical equivalent of Ilseek That is to map a different segment of the file specify e the same file descriptor e the new offset in off e the current segment base address as addr e MAP_FIXED in flags to force the use of addr as the base address otherwise map the new portion of the file as a different additional memory segment Mapping Segments of Memory The old segment is replaced with a new segment at the same address now containing data from a different offset in the file Each time you replace a segment with mmap the previous segment is discarded The new segment is not locked in memory even if the old segment was locked File Permissions Access to a file for mapping is controlled by the same file permissions that control I O to the file The protection in prot must agree with the file permissions For example if the file is read only to the process mmap does not allow prot to specify write or execute access Note When a program runs with superuser privilege for other reasons file permissions are not a protection against accidental updates NFS Considerations The file that is mapped can be local to the machine or can be mounted by NFS In either case be aware that changes to the file are buffered and are not immediate
163. ck is released by another process Creating and Managing Locks The functions for creating and controlling locks are summarized in Table 4 7 Table 4 7 IRIX IPC Functions for Managing Locks Function Name Purpose and Operation usnewlock 3P Allocate a lock in a specified arena usfreelock 3P Release lock memory does not release any process waiting on the lock usinitlock 3P Reset a lock and its metering information does not release any process waiting on the lock usctllock 3P Fetch and reset semaphore metering information or debugging information usdumplock 3P Dump lock metering information to a file You decide whether the locks in an arena will have metering information or not You specify this before creating the arena to usconfig see Initializing Arena Attributes on page 51 When lock metering is enabled you can retrieve the information about a lock at any time to find out whether a lock is a bottleneck in a program IRIX Facilities for Mutual Exclusion Claiming and Releasing Locks The functions for using locks are summarized in Table 4 8 Table 4 8 IRIX IPC Functions for Using Locks Function Name Purpose and Operation ussetlock 3P Seize a lock suspending the caller if necessary until the lock is available usunsetlock 3P Release a lock making it available for other processes uscsetlock 3P Seize a lock if it is available otherwise return a 1 uswsetlock 3P Seize a lock susp
164. cond messages are received msgrcv k 9 1 type 17 len 64 text 00001 Thu Jun 20 09 32 55 1996 msgrcev i 50 1 type 18 len 64 text 00001 Thu Jun 20 09 33 18 1996 Another message receipt is attempted first with IPC_NOWAIT msgrcev i 50 n msgrcv No message of desired typ Another message is attempted without IPC_NOWAIT While msgrcv is suspended the message queue is removed using ipcrm in a different shell window msgrcv k 9 amp 12477 iperm q 50 msgrcv Identifier removed Example of msgget The program msgget in Example 6 5 allows you to create a message queue from the command line The following command line arguments are supported k key Numeric identifier of a message queue for example k 99 p perms Access permissions to set for example p 0664 X Use the IPC_EXCL flag with msgget c Use the IPC_CREAT flag with msgget 147 Chapter 6 Message Queues 148 If the k argument is omitted the program uses a private key and thus creates a message queue that can be used from this program only This is not useful since the program does nothing with the queue before it terminates Example 6 5 Program to Demonstrate msgget Program to test msgget 2 msgget k lt key gt p lt perms gt x c k lt key gt the key to use default 0 IPC_PRIVATE p lt perms gt permissions to use default 600 x use IPC_EXCL use IPC_
165. ct XRectangle max_ink_extent XRectangle max_logical_extent XFontSetExtents Internationalization Support in X11R6 max_ink_extent gives the maximum boundaries needed to render the drawable characters of a fontset It considers only the parts of glyphs that would be drawn and gives distances relative to a constant origin max_logical_extent gives the maximum extent of the occupied space of drawable characters of a fontset The occupied space of a character is a rectangle specifying the minimum distance from other graphical features other graphics generated by a client should not intersect this rectangle max_logical_extent is used to compute interline spacing and the minimum amount of space needed for a given number of characters Here are descriptions of a few of the new extents related functions consult the appropriate reference pages for details e XExtentsOfFontSet returns an XFontSetExtents structure for a fontset e XmbTextEscapement and XwcTextEscapement take a string and return the distance in pixels in the current drawing direction to the origin of the next character after the string if the string were drawn Escapement is always positive regardless of direction e XmbTextExtents and XwcTextExtents take a string and return information detailing the overall rectangle bounding the string s image and the space the string occupies for spacing purposes e XmbTextPerCharExtents and XwcTextPerCharExte
166. ct1 IPC_STAT else perror msgget 151 Chapter 6 Message Queues 152 Example of msgsnd The msgsnd program in Example 6 7 allows you to send one or more messages of specified length and type to a message queue The following command line arguments are supported k key Numeric identifier of a message queue for example k 99 i id Message queue ID alternative to specifying the key for example i 80 c count Number of messages to send The default is 1 t type Numeric type of message to send Types less than 1 are rejected by msgsnd b bytes Size of each message for example b 0x200 n Use the IPC_NOWAIT flag with msgsnd The program sends as many messages as you specify each with the specified type and size The first 32 bytes of each message is a printable string containing a sequence number and the date and time The message is padded out to the specified size with binary 0 Example 6 7 Program to Demonstrate msgsnd Program to test msgsnd 2 msgsnd k lt key gt i lt id gt t lt type gt b lt bytes gt c lt count gt n k lt key gt the key to use or i lt id gt the mq id t lt type gt the type of each message default 1 b lt bytes gt the size of each message default 64 min 32 c lt count gt the number of messages to send default 1 max 99999 n use IPC_NOWAIT flag The program sends lt count gt messages of lt type gt lt bytes g
167. curmsgs 1 An attempt is made to send a message with an illegal priority 32 is the highest allowed mq_send p 99 var tmp Q32x128 mgq_send Invalid argument POSIX Message Queues A message is sent with a valid priority mq send p 19 var tmp Q32x128 mq_attr var tmp Q32x128 flags 0x0 maxmsg 32 msgsize 128 curmsgs 2 The two messages are received The one with higher priority is received first mq_receive c 2 var tmp Q32x128 1 priority 19 len 63 text 00001 Fri Jun 14 09 19 12 1996 2 priority 7 len 128 text 00001 Fri Jun 14 09 17 15 1996 Another message is requested Since the O_NONBLOCK flag is used the absence of any message is reported as an error code rather than suspending the process mq_receive n var tmp Q32x128 mq_receive Resource temporarily unavailable Example of mq_getattr The program mq_attr in Example 6 1 uses mq_getattr to get and display the queue attributes Only one command line argument is accepted path The file pathname of the queue must be given following all options Example 6 1 Program to Demonstrate mq_getattr and mq_setattr j Program to test mq getattr 3 displaying queue information mq_attr lt path gt lt path gt pathname of the queue which must exist ET include lt mqueue h gt message queue stuff include lt errno h gt errno and perror include lt fcntl h gt O RDONLY include lt stdio h gt int main int argc
168. d Get the number of MPI tasks MPI_Comm_size MPI_COMM_WORLD amp ntasks if mytid 0 printf mytid d ntasks d n mytid ntasks Wait for everyone to startup before proceeding MPI_Barrier MPI_COMM_WORLD Le f dowork mytid ntasks MPI_Finalize exit 0 Simpl xample passes a token around a ring void dowork int me int nproc int token int src dest MPI Status status int count 1 int msgtag 4 Determine neighbors in the ring src me l1 dest metl if me 0 src nproc l1 if m nproc l dest 0 if me 0 251 Chapter 12 Distributed Process Parallelism 252 token dest MPI_Send amp token count MPI_INI1 printf token ring begun MPI_Recv amp token count MPI_IN1 MPI_COMM_ WORLD amp status printf token ring don T dest msgtag MPI_COMM_ WORLD value sent d n token Sicr msgqtag revd d n token else MPI _Recv amp token count MPI_INI1 MPI_COMM_ WORLD amp status MPI_Send amp token count MPI_IN1 Example 2 MPMD Example Src msgtag T dest msgtag MP I_COMM_WORLD In this example in the PVM version the slaves are sent all the slave TIDs by the master and they use these to determine their logical ordering among each other The MPI slaves determine their logical ordering by the information available to them about their
169. d aliases produced by xlsfonts Bitmap fonts should now be added to the X Window System and the IRIS GL Font Manager Since DPS needs both outline and bitmap fonts for each supported typeface it first checks which outline fonts are stored in the directory usr lib DPS outline base Then it looks for the corresponding bitmap fonts in other X font directories It ignores all other bitmap fonts Therefore DPS ignores the bitmap fonts you added until you add the corresponding outline fonts Adding an Outline Font To add the Utopia Regular outline font to the X Window System Display PostScript and the IRIS GL Font Manager follow these steps You can install only Adobe text ASCII Type 1 font files or compatibles not binary Type 1 font files and not Type 3 font files Display PostScript can handle Type 3 font files but the X Window System and IRIS GL Font Manager cannot 1 Log in as root 2 Convert the file to Printer Font ASCII PFA format if necessary Printer Font Binary PFB files are not supported To convert pfb files to pfa files use the pfb2pfa command shipped with IRIX version 5 3 and higher see the pfb2pfa 1 reference page For example to convert the Adobe file UTRG____ pfb enter pfb2pfa UTRG____ pfb UTRG____ pfa Installing and Adding Font and Font Metric Files 3 Look at the names of existing outline font files in the directory usr lib DPS outline base Display PostScript requires that the name of each outli
170. d system call SIGPIPE 13 Terminate Read or write to broken pipe see pipe 2 read 2 write 2 SIGALRM 14 Terminate Interval timer elapsed see Timer Facilities on page 117 SIGTERM 15 Terminate Process terminated SIGUSR1 16 Terminate Programmer defined see also text below SIGUSR2 17 Terminate Programmer defined SIGCHLD or 18 Terminate Child process status change see wait 2 and SIGCLD Process Reaping on page 199 SIGPWR 19 Ignore Power fail restart 105 Chapter 5 Signalling Events 106 Table 5 1 continued Signal Numbers and Default Actions Symbolic Name SIGWINCH SIGURG SIGPOLL SIGIO SIGSTOP SIGTSTP SIGCONT SIGTTIN SIGTTOU SIGVTALRM SIGPROF SIGXCPU SIGXFSZ no symbol SIGRTMIN SIGRTMAX Numeric Value 20 21 22 22 23 24 25 26 27 28 29 30 31 32 48 49 64 Default Action Ignore Ignore Terminate Terminate Suspend Suspend Ignore Suspend Suspend Terminate Terminate Terminate and dump Terminate and dump Terminate Terminate Normal Meaning Change in size of window see xterm 1 Urgent socket condition see socket 2 Pollable event from a STREAMS device see streamio 7 Input output possible Stopped Stop key signal from controlling terminal see termio 7 Continued Attempt to read terminal from background process see termio 7 Attempt to write terminal from background process se
171. def int listKey_t edef struct element_s list element listKey_t key struct element_s next int busyFlag pthread_cond_t notBusy event of no longer in use lement_t edef struct listHead_s list head and mutex pthread_mutex_t mutList right to modify the list element_t head istHead_t Internal function to find an element in a list returning NULL if the key is not in the list A returned element could be in use by another thread busy The caller is assumed to hold the list mutex otherwise the returned value could be made invalid at any time tic element_t scanList listHead_t lp listKey_t key element_t ep for ep lp gt head ep ep ep gt next if ep gt key key break return ep Public function to find a key in a list wait until the element is no longer busy mark it busy and return it ment_t getFromList listHead_t lp listKey_t key element_t ep pthread_mutex_lock amp amp lp gt mutList lock list against changes while ep scanList lp key amp amp ep gt busyFlag pthread_cond_wait amp ep gt notBusy amp lp gt mutList A if ep ep gt busyFlag 1 pthread_mutex_unlock amp lp gt mutList Synchronizing Pthreads return ep Public function to release an element returned by getFromList A void freeInList listHead_t lp element_t ep assert ep gt busyFlag pthre
172. des e Courier e Courier Bold e Courier Bold Oblique e Courier Oblique When the PostScript page description software language was developed by Adobe Systems the spaces embedded in font names were replaced with dashes PostScript font names look like this Courier Courier Bold Courier BoldoOblique HeiseiMin W3 Adobe Japanl 2 The size of a font is usually not part of the name of a scalable font because it can be scaled to any size Bitmap fonts are usually designed in specific sizes They are referred to by names such as 12 point Courier or 10 pixel Courier Bold The X Consortium specified 14 part font names for the X Window System Each name is in effect a complete description of the font 265 Chapter 13 Working With Fonts 266 Figure 13 1 shows an example 14 part name for a bitmap font with each part labeled Point sizes in X font names are specified in decipoints tenths of a point Point Vertical Average Foundry Weight Set width size resolution width Encoding adobe courier medium o normal 20 140 100 100 m 110 is08859 1 Font family Slant Pixel Honzonta Spacing Registry size resolution Figure 13 1 X Window System Font Name Example Writing Programs That Need to Use Fonts You can write different types of programs for Silicon Graphics computers for example X Display PostScript DPS IRIS GL OpenGL and mixed model programs Some of your programs need fonts How a program access
173. descriptor can describe a disk file or a device or a special pseudo device such as dev kmem Thus mmap can make a variety of objects part of the address space POSIX adds one more type of mappable object a persistent shared segment you create using the shm_open function Creating a Shared Object The shm_open function is very similar to the open function and takes the same arguments compare the shm_open 2 and open 2 reference pages The arguments are as follows path Name of object a character string in the form of a file pathname oflag Option flags detailed in the reference page and discussed in following text mode Access mode for the opened object In order to declare shm_open and its arguments you need to include both sys mman h and fcntl h header files Shared Object Pathname The POSIX standard says that a shared object name has the form of a file pathname but the standard leaves it implementation defined whether the object is actually a file or 45 Chapter 3 Sharing Memory Between Processes 46 not In the IRIX implementation a shared memory object is also a file The pathname you specify for a shared memory object is interpreted exactly like the pathname of a disk file that you pass to open When you create a new object you also create a disk file of the same name See POSIX IPC Name Space on page 38 You can display the size ownership and permissions of an existing shared segment
174. dified while the thread is running The functions used in scheduling are summarized in Table 11 6 Table 11 6 Functions for Schedule Management Function Purpose pthread_getschedparam 3P Get a thread s policy and priority pthread_setschedparam 3P Set a thread s policy and priority sched_get_priority_max 3C Return the maximum priority value sched_get_priority_min 3C Return the minimum priority value sched_yield 2 Relinquish the processor 223 Chapter 11 Thread Level Parallelism 224 Scheduling Policy There are two scheduling policies in this implementation first in first out SCHED_FIFO and round robin GSCHED_RR The default SCHED_OTHER behaves the same as SCHED_RR SCHED_FIFO and SCHED_RR are similar The round robin scheduler ensures that when a thread has used a certain maximum amount of time without blocking it is moved to the end of the queue of threads of the same priority and can be preempted by other threads The details of scheduling are discussed in the pthread_attr_setschedpolicy 3 reference page Scheduling Priority The queues of runnable threads are ordered by thread priority numbers with a small number representing a low priority and a larger number representing a higher priority Threads with higher priorities are chosen to execute before threads with lower priorities The sched_get_priority_max and sched_get_priority_min functions return the highest and lowest priority numbers
175. dir see the mkfontdir 1 reference page e The files usr lib X11 fonts ps2xlfd_map are used by the X Window System and the IRIS Font Manager to map PostScript names or short font names to 14 part X font names and vice versa The IRIS Font Manager does not use any bitmap fonts that do not have an entry in those files Conventions for Bitmap Font File Names The names of bitmap font files are specified according to the following conventions e Filenames begin with three or four letters unique to the font family such as cour for the Courier family or 8x13 for a utility bitmap family e When a family has different style variants such as Roman and Italic the next character of the filename is an uppercase letter to indicate the style for example courO for Courier Oblique or 8x13B for a utility bold font e The last two characters of the filename are two digits giving the nominal size of the font in points as in courO18 e Most bitmap files are of the Portable Compiled Format PCF type and have the file suffix pcf as in courO18 pcef or 8x13B pcf e Files are compressed using the compress command see the compress 1 reference page and therefore have the terminal suffix Z as in courO18 pcf Z In usr lib DPS AFM there is one font metric file per typeface When you install a font module such as the Japanese Font Module metric files for CID keyed fonts are stored in the directory usr lib X11 fonts CID character collection AFM
176. dress Space Boundaries 4 Page Numbers and Offsets 5 Address Definition 5 Address Space Limits 6 Delayed and Immediate Space Definition 7 Page Validation 9 Read Only Pages 10 Copy on Write Pages 10 Interrogating the Memory System 10 Mapping Segments of Memory 11 The Segment Mapping Function mmap 12 Describing the Mapped Object 12 Describing the New Segment 13 XXX Contents Mapping a File forI O 15 Mapped File Sizes 16 Apparent Process Size 16 Mapping Portions of a File 16 File Permissions 17 NFS Considerations 17 File Integrity 17 Mapping a File for Shared Memory 18 Mapping a Segment of Zeros 19 Mapping Physical Memory 19 Mapping Kernel Virtual Memory 20 Mapping a VME Device 20 Choosing a Segment Address 21 Segments at Fixed Offsets 21 Segments at a Fixed Address 22 Locking and Unlocking Pages in Memory 23 Memory Locking Functions 23 Locking Program Text and Data 24 Locking Mapped Segments 25 Locking Mapped Files 25 Unlocking Memory 26 Reducing Cache Misses 27 Locality of Reference 27 Cache Mapping in Challenge and Onyx Systems 28 Multiprocessor Cache Conflicts 28 Detecting Cache Problems 29 Additional Memory Features 29 Changing Memory Protection 30 Synchronizing the Backing Store 30 Releasing Unneeded Pages 31 vi Contents Interprocess Communication 35 Types of Interprocess Communication Available 36 Using POSIX IPC 38 POSIX IPC Name Space 38 Using IRIX IPC 39 Using System VIPC 39 SVR4 IPC Name Space 40
177. e Getting the Current X Font Path The X system locates font files along a path similar to the execution path used to find executable files To display the current X font path enter this command xset q In addition to other information the xset utility displays font path information that may look like this Font Path usr lib X11 fonts 100dpi usr lib X11 fonts 75dpi usr lib X11 fonts misc usr lib X11 fonts Typel usr lib X11 fonts Speedo usr lib X11 fonts CID The X Window System checks the resolution of your video monitor If that resolution is closer to 75 dpi than 100 dpi it puts the directory 75dpi ahead of the directory 100dpi in the X font path Changing the X Font Path You can change the default X font path by using the option fp on an xset command line For example enter xset fp newpath This command changes the X font path to the new font path newpath Installing and Adding Font and Font Metric Files Installing and Adding Font and Font Metric Files This section explains where the various types of font and font metric files are installed by default and how you can add one of your font or font metric files to the IRIX operating system This section describes the following topics e Locations of Font and Font Metric Files covers the conventional directories and names for font files e Adding Font and Font Metric Files details adding a bitmap and outline font and adding a
178. e The following command line arguments are supported k key i id p perms b bytes u uid g gid Numeric identifier of a message queue for example k 99 Message queue ID alternative to specifying the key for example i 80 Access permissions to set for example p 0664 Maximum size of the message queue for example b 0x1000 Numeric user ID to set as owner Numeric group ID to set as owner 149 Chapter 6 Message Queues 150 Example 6 6 xy include include include include lt key gt lt id gt lt bytes gt Program to test msgct1 2 msgctl k lt key gt i lt id gt b lt bytes gt Program to Demonstrate msgctl p lt perms gt u lt uid gt g lt gid gt the key to use or the mq id new max number of bytes to set in msg_qbytes lt perms gt lt uid gt lt gid gt lt sys msg h gt lt unistd h gt lt errno h gt lt stdio h gt int main int argc char key_t key int msqid 1 long perms 1L long bytes 1L long uid 11 Ly long gid 11 Ly new permissions to assign in msg_perm mode new user id msg queue stuff numeric new group id numeric for msg_perm uid for msg_perm gid ipe h types h for getopt errno and perror kargv key for msgget af specified or r 1L is not valid struct msqid_ds buf int c while
179. e opened under a different descriptor might have different blocking behavior The blocking behavior can be changed by applying mq_setattr to the queue descriptor If the program normally wants to allow suspension but in a particular situation wants to avoid suspension it can apply mq_setattr to change the blocking state and then set it back again Using Message Queues The POSIX functions for using an open queue are summarized in Table 6 3 Table 6 3 POSIX Functions for Using Message Queues Function Name Purpose and Operation mq_send 3 Send a message to a queue mq_receive 3 Receive a message from a queue mq_notify 3 Request asynchronous notification of a message on a queue POSIX Message Queues Sending a Message To send a message to a queue call mq_send specifying the queue the address and length of the message data and an integer specifying the priority class of the message Messages on the queue are retained in arrival sequence within priority classes The message is copied out of the caller s buffer so the buffer can be reused immediately after a successful send The mq_send function blocks if the queue is full unless the O_NONBLOCK attribute is in effect for the queue Receiving a Message To receive a message call mq_receive specifying the queue the address and size of a buffer and the address of an integer to receive the message s priority The size of the buffer must be at least as
180. e reloaded from backing store if they are referenced again Releasing Unneeded Pages Using the madvise function see the madvise 2 reference page you can tell IRIX that a range of pages is not needed by your process The pages remain defined in the address space so this is not a means of reducing the need for swap space However IRIX puts the pages at the top of its list of pages to be reclaimed when another process or the calling process suffers a page fault The madvise function is rarely needed by real time programs which are usually more concerned with keeping pages in memory than with letting them leave memory However there could be a use for it in special cases 31 PART TWO Interprocess Communication Chapter 2 Interprocess Communication Provides an overview of the different communication mechanisms and describes the POSIX System V and BSD compatibility features Chapter 3 Sharing Memory Between Processes Describes the different ways of sharing segments of memory between different processes Chapter 4 Mutual Exclusion Describes semaphores locks and other means of synchronization and exclusion between processes and threads Chapter 5 Signalling Events Describes the different interfaces to UNIX signals and the interval timer facilities Chapter 6 Message Queues Describes two different facilities for creating and using message queues Chapter 7 File and Reco
181. e res int c while 1 c getopt argc argv arRcCF switch c case a opta 1 break case r optr 1 opta 0 break case R optR 1 opta 0 break case c optc 1 opta 0 break case C optC 1 opta 0 break case F optF 1 opta 0 break default return 1 i if opta optr if clock_gettime CLOCK_REALTIME amp sample showtime sample CLOCK_REALTIME value else perror clock_gettime CLOCK_REALTIME if opta optR if clock_getres CLOCK_REALTIME amp res showtime res CLOCK_REALTIME units else perror clock_getres CLOCK_REALTIME if opta optc if clock_gettime CLOCK_SGI_CYCL GI amp sample 122 Timer Facilities showtime sample CLOCK_SGI_CYCLE value else perror clock_gettime CLOCK_SGI_CYCLE if opta optC if clock_getres CLOCK_SGI_CYCLE amp res showtime res CLOCK_SGI_CYCLE units else perror clock_getres CLOCK_SGI_CYCLE yg if opta optF if clock_getres CLOCK_SGI_FAST amp res showtime res CLOCK_SGI_FAST units else perror clock_getres CLOCK_SGI_FAST The real time clock CLOCK_REALTIME can shift backward or jump forward under the influence of adjustments to the system time by a time daemon The Silicon Gr
182. e XI DealWi break case XI DealWi case XI DealWi buf NULL buf status XBufferOverflow buf buflength have a valid status 3 KeyPress Event KeyPress keysym status nt buflength int bufsize char buf L s NULL malloc bufsize buf lt 0 StopSequence XmbLookupString ic amp event buf amp keysym amp status check to see if that worked realloc buf bufsize buflength XmbLookupString ic amp event buf amp keysym amp status Check that status LookupKeysym thKeysym keysym LookupBoth thKeysym keysym FALL INTO charcter case LookupChars thString buf buflength case XI LookupNone break ee a end switch status nd cas Bos break 358 we are in a switch event type KeyPress segment statement bufsize GUI Concerns GUI Concerns It shouldn t be significantly more difficult to internationalize an application with a graphical user interface than an application without such an interface but there are a few further issues that must be addressed e X Resources for Strings covers labeling objects using X resources e Layout describes creating layouts that are usable after localization e Icons explains some concerns for localizing icons X Resources for Strings Resource lookup mechanisms in Xlib as well as in toolkits monit
183. e current value of a semaphore sem_post 3 Perform the P operation incrementing a semaphore and possibly unblocking a waiting process sem_trywait 3 Perform the V operation only if the value of the semaphore is 1 or more sem_wait 3 Perform the V operation decrementing a semaphore and blocking if it becomes negative The abstract operation P is implemented as the sem_wait function Use this to decrement a semaphore s value and if the result is negative to suspend the calling function until the value is restored The V operation is sem_post You can sample a semaphore s value using sem_getvalue The sem_trywait operation is useful when a process or thread cannot tolerate being suspended IRIX Facilities for Mutual Exclusion Using Mutexes and Condition Variables Two additional types of mutual exclusion are available only within a threaded program to coordinate the actions of POSIX threads The mutex is comparable to a lock or to a semaphore initialized to a count of 1 The condition variable provides a convenient way for a thread to give up ownership of a mutex wait for something to happen and then reclaim the mutex Both of these facilities are covered in detail in Chapter 11 Thread Level Parallelism See the headings Mutexes on page 226 and Condition Variables on page 229 IRIX Facilities for Mutual Exclusion IRIX supports a wide selection of mutual exclusion facilities all tuned for use b
184. e next two sections Category Applications need not perform every aspect of their work in the same locale Although this approach is not recommended an application could for example perform most of its activities in the English locale but use French sorting rules You can use locale categories to do this kind of locale mixing Mixing locale categories is not the same as multilingual support see Multilingual Support The category argument is a symbolic constant that tells setlocale which items in a locale to change Table 14 1 lists the available category choices Table 14 1 Locale Categories Category Affects LC_ALL All categories below LC_COLLATE Regular expressions strcoll and strxfrm LC_CTYPE Regular expressions and ctype routines such as islower LC_MESSAGES gettxt pfmt and nl_langinfo LC_MONETARY __localeconv and strfomon LC_NUMERIC Decimal point character for formatted I O and nonmonetary formatting information returned by localeconv LC_TIME ascftime cftime getdate and strftime a LC_LMESSAGES is supported by SVR4 but isn t required by XPG 4 Categories correspond to databases that contain relevant information for each defined locale The locations of these databases are given in the Location of Locale Specific Data on page 295 293 Chapter 14 Internationalizing Your Application 294 Locale The setlocale function attempts to set the locale o
185. e prof tool samples the instruction counter of the program while the program is executing Its output ranks functions by the amount of time that the CPU spent in their code Normally the output of these tools should agree on the location of the hot spots in a program However if prof shows that a function is taking more time than is justified by its pixie execution count that function may be running slowly due to cache miss problems Additional Memory Features Your program can work with the IRIX memory manager to change the handling of the address space 29 Chapter 1 Process Address Space 30 Changing Memory Protection You can change the memory protection of specified pages using mprotect see the mprotect 2 reference page For a segment that contains a whole number of pages you can specify protection of these types Read only By making pages read only you cause a SIGSEGV signal to be generated in any process that tries to modify them You could do this as a debugging measure to trap an intermittent program error You can change read only pages back to read write Read write You can put read write protection on pages of program text but this is bad idea except in unusual cases For example a debugging tool makes text pages read write in order to set breakpoints Executable Normal data pages cannot be executed This is a protection against program errors wild branches into data are trapped quickly If your pro
186. e somewhat confusing similarities between them Features of these structures are summarized in Table 5 7 Table 5 7 Time Data Structures and Usage Data Type Declared In Contains Some Functions Using This Type time_t time h long int with time in seconds since time 2 ctime 3C 00 00 00 UTC January 1 1970 cftime 3C difftime 3C timeval sys time h structure of time_t giving seconds adjtime 2 getitimer 2 and a long int giving microseconds getrusage 3C gettimeofday 3C select 2 utimes 3B itimerval sys time h structure of two timeval fields for getitimer 2 and setitimer 2 first interval and repeat interval timespec_t time h structure of time_t giving seconds _clock_gettime 2 and a long int giving nanoseconds nanosleep 2 aio_suspend 3 sigtimedwait 3C itimerspec __ time h structure of two timespec fields for timer_settime 3C first interval and repeat interval timer_gettime 3C tm time h structure of int fields for seconds localtime 2 gmtime 2 minutes hours day month etc strftime 3C Time Signal Latency It takes time for the kernel to deliver the SIGALRM that notifies your program at the end of an interval The issue of signal latency in general is discussed under Signal Latency on page 110 The signal latency is less for SIGALRM than for other signals since the kernel initiates a scheduling cycle immediately after the timer interrupt without waiting for the end of a fixed time slice When
187. e termio 7 Virtual timer expired see getitimer 2 Profiling timer expired see getitimer 2 CPU time limit exceeded see getrlimit 2 File size limit exceeded see getrlimit 2 and write 2 Unassigned do not use POSIX real time signal range Although SIGUSR1 and SIGUSR2 are nominally defined by the you for your program s purposes they are also used by different application packages for special signals For example if you set a file lock on an NFS mounted file the NFS lock daemon may send SIGUSR1 see NFS File Locking on page 174 Signals Signal Implementations There are three UNIX traditions for signals and IRIX supports all three They differ in the library calls used in the range of signals allowed and in the details of signal delivery The basic signal operations and the implementing functions are summarized in Table 5 2 Table 5 2 Signal Handling Interfaces Function POSIX Functions SVR4 Functions BSD 4 2 Functions Set and query signal sigaction 2 sigset 2 sigvec 3 handler sigsetops 3 signal 2 signal 3 sigaltstack 2 Send a signal sigqueue 2 sigsend 2 kill 3 kill 2 kill 2 killpg 3 pthread_kill 3P Temporarily block sigprocmask 2 sighold 2 sigblock 3 specified signals pthread_sigmask 3P sigrelse 2 sigsetmask 3 Query pending signals sigpending 2 n a n a Wait for a signal handler sigsuspend 2 sigpause 2 sigpause 3 to be invoked Wait for a signal and sigwait 2 n a n a
188. e to national currency representation You can use strfmon to format currency values as strings and then use printf or other functions to write the formatted strings Formatting Dates and Times All of these dates can mean the same thing to different people 92 1 4 4 1 92 1 4 92 All of these can mean the same time to different people 2 30 PM 14 30 14h30 Dates and times can be easily formatted by using strftime which gives a host of options for displaying locale specific dates and times The ascftime and cftime functions give further options but should be avoided because they do not conform to ANSI and XPG 4 specifications The old asctime and ctime functions are now obsolete use strftime instead For more information see the strftime 3C reference page Character Classification and ctype The ctype h header file is described in the ctype 3C reference page and defines macros to determine various kinds of information about a given character isalpha isupper islower isdigit isxdigit isalnum isspace ispunct isprint isgraphQ iscntrl and isascii 309 Chapter 14 Internationalizing Your Application 310 The Issue When programmers knew that a character set was ASCII some convenient assumptions could be made about characters and letters It was common for programmers to do arithmetic with the ASCII code values in order to perform some simple operations For example raising
189. eating the thread including after it has terminated Using Thread Unique Data If your program continues for a long time creating threads and letting them terminate but does not arrange for detaching the completed threads eventually an error will occur because resources have been used up Using Thread Unique Data In some designs especially modules of library code you need to store data that is both e unique to the calling thread e persistent from one function call to another Normally the only data that is unique to a thread is the contents of its local variables on the stack and these do not persist between calls However the pthreads library provides a way to create persistent thread unique data The functions for this are summarized in Table 11 5 Table 11 5 Functions for Thread Unique Data Function Purpose pthread_key_create 3P Create a key class of thread data pthread_key_delete 3P Delete a key pthread_getspecific 3P Retrieve this thread s value for a key pthread_setspecific 3P Set this thread s value for a key Your program calls pthread_key_create to define a new storage key A storage key represents one kind or class of data Each thread has a unique instance of this class of data with an initial value of NULL The returned key value of type pthread_key_t is used by all threads to store and retrieve data of this class Any thread can use pthread_getspecific to retrieve that thread s
190. ections e Overview presents an introduction to internationalization and defines some common terms e Locales explains how to set the current locale and limitations of the locale system e Character Sets Codesets and Encodings describes various ways of encoding characters the traditional ASCII being just one of these e Cultural Items discusses the ways in which different cultures affect the way a string can be viewed for example in outputting or collating e Locale Specific Behavior covers native language support NLS and the NLS database regular expressions and cultural data e Strings and Message Catalogs describes how to create and use catalogs of messages to send diagnostic information to users in various locales e Internationalization Support in X11R6 describes internationalization support provided by X11 Release 6 including features from X11R5 e TInternationalization Support in Motif points to information describing how to internationalize a Motif application e User Input discusses the translation of keyboard events into programmatic character strings for a variety of keyboards 285 Chapter 14 Internationalizing Your Application Overview 286 e GUI Concerns discusses internationalizing applications that use graphical user interfaces GUIs e Popular Encodings presents some common non ASCII encodings For a list of ISO 3166 country n
191. ed a second integer the ID The key number is chosen by the application and is predictable If the application creates the object each time the application starts up the key is always the same The ID number is arbitrary and a new ID is arbitrary each time an object is created A process can gain access to an object based on either number the key or the ID For example an SVR4 shared memory segment has a key and an ID The shmget function takes a key and returns the corresponding ID The ID is used to attach the segment However if a process knows the ID it can simply use it without first calling shmget to obtain it 41 Chapter 2 Interprocess Communication Using 4 2 BSD IPC 42 Private Key Values When creating an IPC object you can specify a key of KEY_PRIVATE 0 This causes an object to be created and recorded in the IPC name space with a key of 0 The created object cannot be accessed from another process by key because if another process uses KEY_PRIVATE it creates its own object However another process can access a key private object using the object s ID number You can use the KEY_PRIVATE feature when you want to create an IPC object for use within a single process or share group lightweight processes that share one address space The IPC object can be passed between processes by its address or by ID number The 4 2 BSD functions for signals and file locking are available To use them you must include
192. ed by only one thread at a time other threads trying to acquire it wait Preparing Mutex Objects When a thread wants to modify a variable that it shares with other threads or execute a critical section the thread claims the associated mutex This can cause the thread to wait until it can acquire the mutex When the thread has finished using the shared variable or critical code it releases the mutex If two or more threads claim the mutex at once one acquires the mutex and continues while the others are blocked until the mutex is released Synchronizing Pthreads A mutex has attributes that control its behavior The pthreads library contains several functions used to prepare a mutex for use These functions are summarized in Table 11 7 Table 11 7 Functions for Preparing Mutex Objects Function Purpose pthread_mutex_init 3P pthread_mutex_destroy 3P pthread_mutexattr_init 3P pthread_mutexattr_destroy 3P pthread_mutexattr_getprotocol 3P pthread_mutexattr_setprotocol 3P pthread_mutexattr_getprioceiling 3P pthread_mutexattr_setprioceiling 3P Initialize a mutex object based on a pthread_mutexattr_t Uninitialize a mutex object Initialize a pthread_mutexattr_t with default attributes Uninitialize a pthread_mutexattr_t Query the priority protocol in a pthread_mutexattr_t Set the priority protocol choice ina pthread_mutexattr_t Query the minimum priority in a pthread_mutexattr_t Set the
193. ed on POSIX threads should use POSIX synchronization mechanisms because they are optimized for pthreads use Use System V IPC functions for code that must comply with the MIPS ABI or code that you are porting from another System V operating system 37 Chapter 2 Interprocess Communication Using POSIX IPC 38 In order to use the POSIX IPC functions described in this part of the book you must include the correct header files and link libraries when compiling The header files required for each function are listed in the reference pages for the functions POSIX IPC functions are defined in the standard libc library That library is included automatically in any link by the cc command POSIX IPC Name Space POSIX shared memory segments named semaphores and message queues are persistent objects that survive the termination of the program that creates them unless the program explicitly removes them The POSIX standard specifies that these persistent names can be implemented in the filesystem and the current IRIX implementation does use filenames in the filesystem to represent IPC objects In order to access a named semaphore or message queue a program opens the object using a pathname similar to the way a program opens a disk file Because these persistent objects are currently implemented as files you can display and access them using IRIX commands for files such as ls rm chmod and chown However you should keep in mind
194. ed the arena Restricting Access to an Arena You can restrict arena access to a single process and the children it creates with sproc a share group by calling usconfig to set CONF_ARENATYPE to US_SHAREDONLY before creating the arena When this is done the file is unlinked immediately after the arena is created Then a call to usinit with the same pathname from a different process creates a different arena one that is not shared with the first one This has several side effects that are detailed in usconfig 3 Arena Access From Processes in a Share Group An arena is a segment in the address space of a process When that process creates a new process using sproc the child process usually shares the same address space see the sproc 2 reference page and Chapter 10 Process Level Parallelism The child process has access to the arena segment on the same basis as the parent process However the child process needs to join the arena formally 53 Chapter 3 Sharing Memory Between Processes 54 The child process should join the arena by calling usadd passing the address of the arena The child should test the return code of this function since it can reflect an error in either of two cases e The arena has not been created or an incorrect arena address was passed e The arena was not configured to allow enough using processes and no more users can be allowed A child process can join an arena automatically s
195. em that when the function resignArena in Example 3 4 finds that it has reduced the joinedProcs count to 0 it could deinitialize the arena for example unlinking the file on which the arena is based This is not a good idea because of the remote chance of the following sequence of events 1 Process A executes joinArena initializing the arena 2 Unrelated process B executes joinArena through the usinit call but is suspended for a higher priority process before executing usgetinfo 3 Process A detects some error unrelated to arena use and as part of termination calls resignArena 4 Process B resumes execution with the call to usgetinfo If the resignArena function did something irrevocable such as unlinking or truncating the arena file it would leave process B in an unexpected state 59 Chapter 3 Sharing Memory Between Processes System V Shared Memory Functions 60 The System V shared memory functions allow two or more processes to share memory Unlike the IRIX method in which the external name of a shared arena is also the name of a file the external name of an SVR4 shared segment is an integer held in an IPC name table see SVR4 IPC Name Space on page 40 The functions and commands used with SVR4 shared memory are discussed in the following topics and summarized in Table 3 6 Table 3 6 SVR4 Shared Memory Functions Function Name Purpose and Operation shmeget 2 Create a shared memory I
196. emaphore by more than 1 in an operation The wait for zero operation allows one process or thread to monitor the state of a semaphore independent of the P and V operations performed on the semaphore by other processes or threads You can also perform a sequence of operations a sequence of P or V or zero wait operations or a mix of operation types on multiple semaphores in a single call To do this you specify an array containing more than one operation structure The semop function performs each operation in sequence System V Facilities for Mutual Exclusion You can use this feature for example to claim multiple resources each represented by a different semaphore Your array would specify the P operation on each of the semaphores in sequence When semop returns successfully you own all the resources A similar multiple V operation returns all the resources at once The IPC_NOWAIT and SEM_UNDO flags are important when claiming multiple resources at once Specify SEM_UNDO on all operations and specify IPC_NOWAIT on all but the first one If the second or later resource is unavailable semop restores all preceding claims and returns an error code As long as all processes or threads operate on semaphores in the same order this logic prevents deadlocks and it avoids long fruitless suspensions Example Programs The programs in this section allow you to experiment with semaphore sets from the command line e Example 4 3 o
197. emaphore object itself and you refer to a semaphore by its address This is different from locks which are discussed later in this chapter Creating Polled Semaphores A polled semaphore differs from a normal semaphore in the P operation When decrementing the semaphore value produces a negative number the calling process is not blocked Instead it receives a return code The process then has to include the address of the semaphore in the list of events passed to poll see the poll 2 reference page The V operation applied to a polled semaphore does not release a block process but rather causes a poll operation to end You can use polled semaphores to integrate semaphore handling with other events for which you wait with poll such as file operations You cannot combine the use of normal semaphores with the use of polled devices since a single process cannot wait in a poll call and in a uspsema call at the same time The functions for creating and controlling polled semaphores are summarized in Table 4 5 Table 4 5 IRIX IPC Functions for Managing Polled Semaphores Function Name Purpose and Operation usnewpollsema 3P Allocate a polled semaphore in an arena and give it an initial value usopenpollsema 3P Assign a file descriptor to a polled semaphore The file descriptor can be passed to poll or select This must be done before the semaphore can be used usclosepollsema 3P Release a file descriptor assigned with uso
198. ements within a font set with a semicolon e End the string with a colon An example of specifying a Japanese fontList is as follows fontList 7x14 mincho 14 14 User Input User Input This section explains the translation of physical user events into programmatic character strings or special keyboard data such as backspace This kind of work should be done by toolkits If you can use a toolkit to manage event processing for you do so and blissfully ignore this section If you are writing a toolkit text object or are writing a truly extraordinary application then this section is for you This section on user input covers these topics e About User Input and Input Methods presents an overview of user input and input methods e About X Keyboard Support covers X keyboard support including keys keycodes keysyms and composed characters e Input Methods IMs describes how input methods are opened and closed e IM Styles discusses the use and naming of IM styles e Input Contexts ICs explains an IM styles IC values pre edit and status attributes and creating and using ICs e Events Under IM Control describes differences in processing events under IM control including XFilterEvent and LookupString routines About User Input and Input Methods Just as internationalized programs cannot assume that data is in ASCII they cannot assume that user input
199. en flags receives c x t int ropt 0 r option seen int wopt 0 w option seen int shm_fd file descriptor int mprot PROT_READ protection flags to mmap int mflags MAP_SHARED mmap flags void attach assigned memory adddress char path gt first non option argument int c while 1 c getopt argc argv p s cxrtw switch c 48 POSIX Shared Memory Operations case p permissions perms int strtoul optarg NULL 0 break case s segment size size size_t strtoul optarg NULL 0 break case c use O_CREAT oflags O_CREAT break case x use O_EXCL oflags O EXCL break case t use O_TRUNC oflags O_TRUNC break case r use O_RDONLY ropt 1 break case w wait after attaching wopt 1 break default unknown or missing argument return 1 switch while if optind lt argc path argv optind first non option argument else printf Segment pathname required n return 1 if 0 ropt read write access reflect in mprot and mflags oflags O_RDWR mprot PROT_WRITE mflags MAP_AUTOGROW MAP AUTORESRV else read only access mprot and mflags defaults ok oflags O_RDONLY shm fd shm open path oflags perms if 1 shm fd attach
200. ending the caller if necessary takes a specified number of spins as an argument ustestlock 3P Test a lock returning 0 if it is instantaneously available and 1 if it is not available Tip When reading the reference pages cited above notice that usnewlock returns a ulock_t object which is simply a pointer All the functions that operate on locks take a ulock_t object not a pointer to a ulock_t That is the ulock_t type represents a handle or reference to a lock not a lock itself This differs from the treatment of semaphores which is described under Creating Normal Semaphores on page 77 On uniprocessors none of the functions us c w setlock spin if the lock is available they return immediately and if it is not they suspend the calling process and give up the CPU On multiprocessors ussettlock spins for a default number of times before it suspends the process The function uswsetlock is the same but you can specify the number of spins to take before suspending A process can call usunsetlock on a lock that is either not locked or locked by another process In either case the lock is unlocked Double tripping calling a set lock function twice with the same lock is also permissible The caller blocks until another process unsets the lock 81 Chapter 4 Mutual Exclusion 82 Using Barriers The functions to manage and use barriers are summarized in Table 4 9 Table 4 9 IRIX IPC Functions for
201. er depends on the hardware architecture and determines the optimal programming model Single Memory Systems The CHALLENGE Onyx system architecture uses a high speed system bus to connect all components of the system 181 Chapter 8 Models of Parallel Computation 182 One component is the physical memory system which plugs into the bus and is equally available to all other components Other units that plug into the system bus are I O adapters such as the VME bus adapter CPU modules containing MIPS R4000 R8000 or R10000 CPUs are also plugged into the system bus In the CHALLENGE Onyx architecture the single common memory has these features e There is a single address map that is the same word of memory has the same address in every CPU e There is no time penalty for communication between processes because every memory word is accessible in the same amount of time from any CPU e All peripherals are equally accessible from any process The effect of a single common memory is that processes running in different CPUs can share memory and can update the identical memory locations concurrently For example suppose there are four CPUs available to a Fortran program that processes a large array of data You can divide a single DO loop so that it executes concurrently on the four CPUs each CPU working in one fourth of the array in memory As another example IRIX allows processes to map a single segment of memory into t
202. erThreadKey If the key itself has not been defined the function defines it calling createPerThreadKey by way of pthread_once If this thread s value of the key is NULL the function creates and initializes a value and stores it using pthread_setspecific Pthreads and Signals Signals are an integral part of UNIX programming For a general overview of signal concepts and numbers see Signals on page 104 and the signal 5 reference page IRIX supports three different partly compatible signal facilities BSD signals SVR4 signals and POSIX signals When you are writing a pthreads program you must be sure to use only the POSIX signal facilities see POSIX Signal Facility on page 111 Do not mix use of other signal functions in a pthreads program or unpredictable results can follow 221 Chapter 11 Thread Level Parallelism 222 Setting Signal Masks A thread specifies which signals it is willing to receive see Signal Blocking and Signal Masks on page 107 Ina program that is linked with the pthreads library this must be done using pthread_sigmask Each thread inherits the signal mask of the thread that calls pthread_create Typically you set an initial mask in the first thread so that it can be inherited by all other threads When a signal is directed to a specific thread that blocks the signal the signal remains pending until the thread unblocks the signal When a signal is directed to the process
203. erhead Once you know what the application can handle look through the IM styles for a match as shown in Example 14 9 Example 14 9 Setting the Desired IM Style for i 0 i lt IMcando gt count_styles i XIMStyle tmpStyle tmpStyle IMcando gt support_styles i if tmpStyle amp clientCanDo tmpStyle styleWeWillUse tmpStyle if styleWeWillUse NULL exit_with_error XFree IMcando styleWeWillUse is set which is what we were after IC Values There are several pieces of information an input method may require depending on the input context and style chosen by the application The input method can acquire any such information it needs from the input context ignoring any information that does not affect the style or IM A full description of every item of information available to the IM is supplied in X Window System Third Edition The following is a brief list XNClientWindow Specifies to the IM which client window it can display data in or create child windows in Set once and cannot be changed XNFilter Events An additional event mask for event selection on the client window XNFocusWindow The window to receive processed composed Key events XNGeometryCallback A geometry handler that is called if the client allows an IM to change the geometry of the window XNiInputStyle Specifies the style for this IC 353 Chapter 14 Internationalizing Your Application 354 XNResou
204. erminates Another design is possible In some applications you may have to manage a flow of many relatively short activities that should be done in parallel However the sproc function has considerable overhead It is inefficient to continually create and destroy child processes You do not want to create a new child process for each small activity and destroy it afterward Instead you can create a pool containing a small number of processes When a piece of work needs to be done you can dispatch one process to do it The fragmentary code in Example 10 1 shows the general approach Example 10 1 Partial Code to Manage a Pool of Processes typedef void workFunc void arg struct oneSproc struct oneSproc next gt next oneSproc ready to run workFunc calledFunc gt function the sproc is to call void callArg argument to pass to the called func usema_t sprocDone optional sema to post on completion usema_t sprocWait sproc waits for work here sprocList NUMSPROCS usema_t readySprocs count represents sprocs ready to work uslock_t sprocListLock mutex control of sprocList head struct oneSproc sprocList gt first ready oneSproc Put a oneSproc structure on the ready list and sleep on it Called by a child process when its work is done xf void sprocSleep struct oneSproc theSproc ussetlock sprocListLock acquire exclusive rights to sprocList
205. errupt handler in the IRIX kernel chooses a page of physical RAM to hold the page In order to acquire this space the kernel might have to invalidate some other page belonging to your process or to another process The contents of the needed page are read from the appropriate backing store into memory and the process continues to execute Page validation takes from 10 to 50 milliseconds Most applications are not impeded by page fault processing but a real time program cannot tolerate these delays The total size of all the valid pages in an address space is displayed by the ps command under the heading SZ The aggregate size of the pages that are actually in memory is the resident set size displayed by ps under the heading RSS Chapter 1 Process Address Space Read Only Pages A page of memory can be marked as valid for reading but invalid for writing Program text is marked this way because program text is read only it is never changed If a process attempts to modify a read only page a hardware interrupt occurs When the page is truly read only the kernel turns this into a SIGSEGV signal to the program Unless the program is handling this signal the result is to terminate the program with a segmentation fault Copy on Write Pages When fork is executed the new process shares the pages of the parent process under a rule of copy on write The pages in the new address space are marked read only When the new process attempts to mod
206. es Silicon Graphics will then generate CCM and CFM files from those files 278 Installing and Adding Font and Font Metric Files Adding a Font Metric File Adobe Font Metric AFM files are primarily used by application programs for example to generate PostScript code for a specified document Follow these steps to add a font metric file for an outline font in the Type 1 format 1 Log in as root 2 Put Adobe Font Metric files in the directory usr lib DPS AFM The name of an AFM file must match the PostScript font name as given in the file usr lib X11 fonts ps2xlfd_map see Locations of Font and Font Metric Files on page 271 For example Adobe provided the Utopia Regular font metric file UTRG____ AFM When this font was added to IRIX the name was changed to Utopia Regular to correspond to the line Utopia Regular adobe utopia medium r normal 0 0 0 0 p 0 1is08859 1 in usr lib X11 fonts ps2xlfd_map The file was put in the directory usr lib DPS AFM Font metric files for a large outline font in the CID keyed format should be put in the directory usr lib X11 fonts CID character collection AFM There is one AFM file for each CIDFont file and one AFM file for each CID keyed font 279 Chapter 13 Working With Fonts Downloading a Type 1 Font to a PostScript Printer 280 Some outline fonts are usually built into a PostScript printer You can find out which fonts are known to the PostScript
207. es font files depends on the program type e X programs access fonts by calling X font functions such as XListFonts and XLoadFont e DPS programs access fonts by calling X and DPS functions or by using PostScript e IRIS GL and IRIS GL X mixed model programs usually access fonts by calling font management fm functions from the IRIS GL Font Manager library fmenumerate and fmfindfont for example Most fonts are installed when you install the X Window System X11 Execution Environment Some fonts are installed with other software components such as DPS and IRIS Showcase Some bitmap fonts are installed when you install a language module such as the Japanese Language Module JLM Some outline fonts are installed when you install a font module such as the Japanese Font Module JFM However most fonts are shared by the X Window System DPS which is an extension of the X Window System IRIS GL Font Manager Impressario and other software components Using Fonts With the X Window System To maintain compatibility and portability it is best not to access font files directly from an application program because font formats font names font contents and the location of font directories may change Your program should use the Application Programming Interfaces APIs specified for the X Window System DPS and IRIS GL Font Manager or call even higher level functions for the 2D and 3D text available from toolkits such as
208. ess in the caller s address space using a private stack sprocsp 2 Create a new process in the caller s address space using a preallocated stack area pretl 2 Query and set assorted process attributes sysmp 2 Query multiprocessor status and assign processes to CPUs syssgi 2 Query process virtual and real memory use and other operations You can initiate a program at a specified nondegrading priority explained under Process Scheduling on page 199 using npri You can initiate a program running on a specific CPU of a multiprocessor using runon Both attributes the assigned priority and the assigned CPU are inherited by any child processes that the program creates Process Creation The process that creates another is called the parent process The processes it creates are child processes or siblings The parent and its children together are a share group IRIX provides special services to share groups For example you can send a signal to all processes in a share group Using Multiple Processes The fork function is the traditional UNIX way of creating a process The new process is a duplicate of the parent process running in a duplicate of the parent s address space Both execute the identical program text that is both processes return from the fork call and you distinguish them by the return code which is 0 in the child process and the new process ID in the parent The sproc and sprocsp func
209. estern Europe Latin 1 uses only one byte per character unlike some other codesets so 8 bit clean ASCII software should work without modification using the Latin 1 codeset Ensuring that code is 8 bit clean is the single most important aspect of internationalizing software Another caveat about 8 bit characters applies only to a particular set of circumstances If you are not using a multibyte character type see the next section you should not declare characters as type signed char The default in IRIX C is for char to imply unsigned char If you try to cast a signed char to an int as you must do to use the ctype functions and the character s high bit is set as it may be in an 8 bit character set the high bit is interpreted as a sign bit and extends into the full width of the int Character Representation Western languages usually require only one byte for each character Asian languages however often require two or even four bytes per character and some Asian encodings allow a variable number of bytes per character The two kinds of encodings that allow more than one byte per character are e multibyte MB characters are of variable size e wide characters WC or wchar characters are a fixed number of bytes long Character Sets Codesets and Encodings The application developer must decide where to use WC and MB characters and strings e Multibyte strings are almost the default string I O uses MB MB code works for
210. etpriority 2 Set the priority of a process or process group nice 1 Run a program at a positive or negative increment from normal priority renice 1 Alter the priority of a running process by a positive or negative increment For BSD compatibility use the nice and renice commands to alter priorities and within a program use getpriority and setpriority to query and set priorities These commands and functions use priority numbers ranging from 20 through 0 to 20 with lower arithmetic values having superior access to the CPU Only the IRIX schedctl function gives you complete access to a variety of operations related to process scheduling Some of the key operations are as follows NDPRI Set a nondegrading priority for the calling process see text GETNDPRI Query the nondegrading priority of the calling process SETMASTER Set the master process of a share group By default the parent process is the master process but it can transfer that honor SCHEDMODE SGS_SINGLE Cause all processes in the share group to be suspended except the master process set with SETMASTER SCHEDMODE SGS_GANG Cause all processes in the share group to be scheduled as a gang with all running concurrently SCHEDMODE SGS_FREE Schedule the share group in the default fashion Using Multiple Processes A program started interactively inherits a scheduling discipline based on degrading priorities That is the longer the process executes w
211. etween processes that run concurrently in a multiprocessor Using IRIX Semaphores Two kinds of semaphores are supported in IRIX IPC normal and polled Both are allocated in a shared memory arena see IRIX Shared Memory Arenas on page 50 Creating Normal Semaphores The functions for managing normal semaphores are summarized in Table 4 4 Table 4 4 IRIX Functions to Manage Nonpolled Semaphores Function Name Purpose and Operation usnewsema 3P Allocate a semaphore in an arena and give it an initial value usfreesema 3P Release arena memory used by a semaphore does not release any process waiting on the semaphore usinitsema 3P Reset a semaphore value and its metering information does not release any process waiting on the semaphore usctlsema 3P Set and reset semaphore metering information and other attributes usdumpsema 3P Dump semaphore metering information to a file 77 Chapter 4 Mutual Exclusion 78 To allocate anew shared arena semaphore and set its initial value call usnewsema Use usctlsema to enable recursive use of the semaphore and to enable the collection of metering information You can use the metering information to find out whether a semaphore is a bottleneck or not Tip When reading the reference pages cited above notice that usnewsema returns the address of a usema_t object and all the other functions take the address of a usema_t That is usema_t represents the type of the s
212. eue e Example 6 7 on page 152 demonstrates the use of msgsnd to put messages onto a queue e Example 6 8 on page 154 demonstrates the use of msgrcv to take messages from a queue The four example programs have a consistent design and use consistent command line argument letters Each accepts optional arguments that allow you to exercise all the features of one function including most error return codes The following is a simple example of use First a queue is created with key 9 ipes q IPC status from dev kmem as of Wed Jun 12 10 36 38 1996 ID KEY MODE OWNER GROUP Message Queues msgget k 9 c msqid 0x0032 owner 1110 20 perms 100600 max bytes 32768 0 msgs 0 bytes on queue ipcs q IPC status from dev kmem as of Thu Jun 20 09 32 25 1996 E ID KEY MODE OWNER GROUP Message Queues q 50 0x00000009 rw cortesi user The use of the IPC_EXCL flag is tested msgget k 9 c x msgget File exists A message is sent to the queue msgsnd i 50 t 17 msgctl i 50 owner 1110 20 perms 100600 max bytes 32768 1 msgs 64 bytes on queue System V Message Queues The maximum queue size is changed msgctl k 9 b 1024 owner 1110 20 perms 100600 max bytes 1024 1 msgs 64 bytes on queue A second message is sent msgsnd i 50 t 18 msgctl i 50 owner 1110 20 perms 100600 max bytes 2 msgs 128 bytes on queue 1024 The first and se
213. ex int n 254 1 float data slaves exchange data with left neighbor 1 1 pvm_parent msgtype Exit PVM before stopping int tids int nproc Example Programs int i dest float psum 0 0 float sum 0 0 for i 0O i lt n itt sum me data il illustrate node to node communication pvm_initsend PvmDataDefault pyvm_pkfloat amp sum 1 1 dest metl if dest nproc dest 0 pvm_send tids dest 22 pvm_recv 1 22 pvm_upkfloat amp psum 1 1 return sumtpsum MPMD in MPI Version Master Task include lt stdio h gt include lt mpi h gt main int argc char argv int mytid my task id int n nproc ntasks i who msgtype float data 100 result 32 char sbuff 1000 rbuff 1000 int position MPI_Status status Initialize MPI MPI_Init amp argc amp argv Get our task id our rank in the basic group MPI_Comm_rank MPI_COMM_WORLD amp mytid Get the number of MPI tasks and slaves MPI_Comm_size MPI_COMM_WORLD amp ntasks nproc ntasks 1 if mytid 0 printf mytid d ntasks d n mytid ntasks Begin User Program n 100 initialize _data data n for i 0 ixn i data i 1 Pack initial data to be sent to slave tasks 255 Chapter 12 Distributed Process Parallelism 256 position 0 MPTI_Pack amp n 1 MPI
214. ex Then it can safely modify the list pointers It scans up the list looking for the pointer that points to the target element It removes the target element from the list by copying its next field to replace the pointer to the target element With the element removed from the list deleteInList calls pthread_cond_broadcast to wake up all threads not just the first thread that might be waiting for the element to become nonbusy Each of these threads resumes execution at point A by attempting to re acquire the list mutex However deleteInList is still holding the list mutex The mutex is released then the other threads can resume execution following point A but this time when they search the list the desired key is no longer found Meanwhile deleteInList uses pthread_cond_destroy to release any memory that the pthreads library might have associated with the condition variable before releasing the list element object itself Chapter 12 Distributed Process Parallelism Processes and threads allow you to execute in parallel within a single system memory When the system memory is distributed among multiple independent machines your program must be built around a message passing model In a message passing model your application consists of multiple independent processes each with its own address space running in possibly many different computers Each process shares data and coordinates with the others by
215. f errno EWOULDBLOCK break mission impossible sginap 1 let lock holder run return errno The following points should be noted about Example 7 4 e The compiler variable _BSD_COMPAT is defined in order to get BSD compatible definitions from standard header files e The only use of flock is to lock an entire file so there is no attempt to specify the start or length of a record e The LOCK_NB flag requests the function to return if the lock cannot be placed Without this flag the function suspends until the lock can be placed Setting and Removing Record Locks Locking a record is done the same way as locking a file except that the record does not encompass the entire file contents This section examines an example problem of dealing with two records which may be either in the same file or in different files that must be updated simultaneously so that other processes get a consistent view of the information they contain This type of problem occurs for example when updating the inter record pointers in a doubly linked list 165 Chapter 7 File and Record Locking 166 To deal with multiple locks consider the following questions e What do you want to lock e For multiple locks in what order do you want to lock and unlock the records e What do you do if you succeed in getting all the required locks e What do you do if you fail to get one or more locks In managing record locks you
216. f lock on the record Cooperating processes should still request an appropriate record lock before an I O operation but an additional check is made by IRIX before each I O operation to ensure the record locking protocol is being honored Mandatory locking offers security against unplanned file use by unrelated programs but it imposes additional system overhead on access to the controlled files 159 Chapter 7 File and Record Locking Lock Promotion and Demotion A read lock can be promoted to write lock status if no other process is holding a read lock in the same record If processes with pending write locks are waiting for the same record the lock promotion succeeds and the other sleeping processes wait Demoting a write lock to a read lock can be done at any time Because the lockf function does not support read locks lock promotion is not applicable to locks set with that call Controlling File Access With File Permissions 160 The access permissions for each UNIX file control which users can read write or execute the file These access permissions may be set only by the owner of the file or by the superuser The permissions of the directory in which the file resides can also affect the access permissions for a file Note that if the permissions for a directory allow anyone to write in the directory and the sticky bit is not included in the permissions files within that directory can be removed even by a user who doe
217. f the specified category to the specified locale You should almost always pass the empty string as the locale parameter to conform to user preferences On success setlocale returns the new value of the category If setlocale couldn t set the category to the value requested it returns NULL and does not change locale The Empty String An empty string passed as the locale parameter is special It specifies that the locale should be chosen based on environment variables This is the way a user specifies a preferred locale and that preference should almost always be honored The variables are checked hierarchically depending on category as shown in Table 14 2 for instance if the category is LC_COLLATE an empty string locale parameter indicates that the locale should be chosen based on the value of the environment variable LC_COLLATE or if that value is undefined the value of the environment variable LANG which should contain the name of the locale that the user wishes to work in Table 14 2 Category Environment Variables Category First Environment Variable Second Environment Variable LC_COLLATE LC_COLLATE LANG LC_CTYPE LC_CTYPE LANG LC_MESSAGES LC_MESSAGES LANG LC_MONETARY LC_MONETARY LANG LC_NUMERIC LC_NUMERIC LANG LC_TIME LC_TIME LANG Specifying the category LC_ALL attempts to set each category individually to the value of the appropriate environment variable If no non null environment variable is available
218. ff is an address in that memory off must be an integral multiple of the memory page size see Interrogating the Memory System on page 10 len The number of bytes of data from fd to be mapped The initial size of the segment is len rounded up to a multiple of whole pages Describing the New Segment Three parameters of mmap describe the segment to be created addr Normally 0 to indicate that IRIX should pick a convenient base address addr can specify a virtual address to be the base of the segment See Choosing a Segment Address on page 21 prot Access control on the new segment You use constants to specify a combination of read write and execute permission The access control can be changed later see Changing Memory Protection on page 30 flags Options on how the new segment is to be managed The elements of flags determine the way the segment behaves and are as follows MAP_FIXED Take addr literally MAP_PRIVATE Changes to the mapped data are visible only to this process MAP_SHARED Changes to the mapped data are visible to all processes that map the same object MAP_AUTOGROW Extend the object when the process stores beyond its end not POSIX MAP_LOCAL Map is not visible to other processes in share group not POSIX MAP_AUTORESRV Delay reserving swap space until a store is done not POSIX The MAP_FIXED element of flags modifies the meaning of addr Discussion of this is under Choosing a Seg
219. ffers in a pool of buffers Each resource unit is represented by a message In order to obtain a unit you receive one message from the queue To release a unit for other processes to use you send the unit message back to the queue The latter scheme can be used to compensate for a performance problem The speed of communication through a queue is restricted by the fact that every message is copied twice When a message is sent it is copied from the sender s buffer to some reserved memory space When the message is received it is copied into the buffer supplied by the receiving process or thread So long as messages are small copying is not a problem When messages are large copying can be avoided as follows Allocate a pool of message buffers Set up a queue of small messages each message representing a ticket to use a particular buffer In order to obtain a buffer a process receives a message from this queue The process fills the buffer then it sends the buffer without copying by sending only the ticket on another queue The process that receives the ticket uses the data in the buffer without needing to copy it and returns the buffer by sending the ticket to the original queue POSIX Message Queues 130 The POSIX real time extensions detailed in IEEE standard 1003 1b include support for messages queues These functions are discussed in the following topics and demonstrated in example programs POSIX Messa
220. fficiency comparative 174 F_GETLK 169 F_SETLK 167 F_TEST 171 F_ULOCK 169 F_UNLCK 169 failure 166 forking 172 lock information 169 locking a file 162 mandatory 174 assuring 173 multiple read locks 169 opening files 161 order of lock removal 169 removing locks 165 setting locks 165 Index file descriptor with mmap 12 file typing rules 332 LEGEND 332 MENUCMD 332 Finland country code 368 fonts 261 281 accessing 266 adding 271 279 bitmap font 274 276 font files 273 font metric file 279 outline font 276 279 Utopia Regular font files 273 aliases 267 character defined 263 display characters 268 downloading 280 images 264 installing 271 279 missing fonts 280 names 265 267 opening a shell window 270 path 270 pixels 264 point size 264 PostScript printers 280 programming access 266 resolution and size 264 scaling 268 Speedo format 271 Type 1 font 271 280 281 typeface defined 263 using APIs 266 Utopia fonts 280 viewing 268 virtual memory 281 xfd command 268 X Window System 265 267 279 fontsets 338 339 creating 339 specifying 338 using 339 fork defines address space 5 new address space copy on write 10 forking 172 France country code 368 ftruncate on memory mapped file 17 G Germany country code 368 getpagesize 5 getrlimit 6 H heap segment 4 6 Hong Kong country code 368 i18n See internationalizati
221. g buffer pointers A LIFO queue can be managed without a lock see Using Compare and Swap on page 83 Semaphores created using POSIX functions and semaphores created by the SVR4 IPC facility can be used to coordinate IRIX processes or POSIX threads Semaphores supported by the IRIX IPC facility can be used to coordinate IRIX processes only Condition Variables A condition variable is a software object that represents the occurrence of an event Typically the event is a software action such as other thread has supplied needed data Condition variable support is included in the POSIX pthreads library and can be used only to coordinate among POSIX threads not between IRIX processes See Chapter 11 Thread Level Parallelism for information on the pthread library A thread that wants to wait for an event claims the condition variable which causes the thread to wait The thread that recognizes the event signals the condition variable releasing one or all threads that are waiting for the event 71 Chapter 4 Mutual Exclusion 72 In the expected mode of use there is a shared resource that can be depleted Access to the resource is represented by a mutex A thread claims the mutex but then finds that the shared resource is depleted or unready This thread needs to do three things 1 Give up the mutex so that some other thread can renew the shared resource 2 Wait for the event that resource is now ready for
222. ge 96 89 Chapter 4 Mutual Exclusion 90 Using Semaphore Sets You perform operations on the semaphores in a set by calling semop This function takes a semaphore set ID and an array of one or more semaphore operation structures Each of the operation structures specifies the following e The index of a semaphore in the set numbering the semaphores from 0 e Anumber specifying one of three operations Zero meaning to test the semaphore for equality to 0 A positive number such as 1 meaning to increment the semaphore value possibly releasing waiting processes or threads the V operation A negative number such as 1 meaning to decrement the semaphore value when that can be done without making it negative the P operation e A flag word that can specify these flags IPC_NOWAIT do not suspend but return an error if the Zero test fails or the P operation cannot be done SEM_UNDO undo this operation if it succeeds but an operation later in the array should fail In the simplest case you pass an array containing just one operation to increment or decrement one semaphore by 1 the traditional V or P operation Used this way a semaphore in a set is functionally the same as an IRIX or POSIX semaphore SVR4 semaphores permit additional operations not available with IRIX or POSIX semaphores The negative or positive value in the operation structure is not required to be 1 so you can increment or decrement a s
223. ge Queues Managing Message Queues The POSIX functions for creating controlling closing and removing message queues are summarized in Table 6 2 Table 6 2 POSIX Functions for Managing Message Queues Function Name Purpose and Operation mq_open 3 Create a queue if it does not exist and gain access to it mq_getattr 3 Get information about an open message queue mq_setattr 3 Change the blocking nonblocking attribute of an open message queue mq_close 3 Give up access to a queue mq_unlink 3 Remove a message queue from the system when the last process to have it open closes it Creating a Message Queue The mq_open function has two purposes It is used to gain access to a queue that exists and it can create a queue that does not exist To create a new queue call mq_open with four arguments as follows using the names given in the reference page mg_name The pathname that the queue will have oflag A set of flags that includes O_CREAT and may include O_EXCL mode The access permissions the queue will have mqg_attr Either NULL or the address of an mq_attr structure specifying the queue attributes of maximum message size and maximum messages The name of a queue has the same form as a disk filename and in fact a queue is implemented as a file The file retains the queued messages when the queue is not open so that the queued data persists beyond the termination of the programs that use the queue The queued
224. ges following the set statement belong to set n until either a delset or another set is reached You can skip set numbers for example you can have a set 3 without having a set 2 but the set numbers that you use must be listed in ascending numerical order and every set must have anumber Any string following the set identifier on the same line is considered a comment delset n deletes the set n from a message catalog quote c specifies a quote character c which can be used to surround message text so that trailing spaces or null empty messages are visible in a message source line By default there is no quote character and messages are separated by newlines To continue a message onto a second line add a backslash to the end of the first line Sset 1 1 Hello world 2 here is a long string n 3 Hello again n message text n Message 2 in set 1 is here is a long string n Compiling XPG 4 Message Catalogs After creating the message catalog sources you need to compile them into binary form using gencat which has the following syntax gencat catfile msgfile msgfile where catfile is the target message catalog and msgfile is the message source file see the gencat 1 reference page If an old catfile exists gencat attempts to merge new entries with the old gencat resolves set and message number conflicts with new information replacing the old The catfile then needs to be placed in a location
225. ges its cancellation state The initial state of a thread is PTHREAD_CANCEL_ENABLE and PTHREAD_CANCEL_DEFERRED In this state a cancellation request is blocked until the thread calls a function that is a defined cancellation point The functions that are cancellation points are listed in the pthread_setcanceltype 3P reference page A thread can explicitly permit cancellation by calling pthread_testcancel Joining and Detaching Sometimes you do not care when threads terminate your program starts a set of threads and they continue until the entire program terminates In other cases threads are created and terminated as the program runs One thread can find out when another has terminated by calling pthread_join specifying the thread ID The function does not return until the specified thread terminates The value the specified thread passed to pthread_exit is returned At this time your program can release any resources that you associate with the thread for example stack space see Thread Stack Allocation on page 213 The pthread_join function detaches the terminated thread If your program does not use pthread_join and does continue execution after threads have terminated you must arrange for terminated threads to be detached in some other way One way is by specifying automatic detachment when the threads are created see Initial Detach State on page 213 Another is to call pthread_detach at any time after cr
226. gh Ox3ffc 0000 are reserved for user defined segment base addresses You may specify values in this range as addr with MAP_FIXED in flags When you map two or more segments into this region no two segments can occupy the same 256 KB unit This rule ensures that segments always start in different pages even when the maximum possible page size is in use For example if you want to create two segments each of 4096 bytes you can place one at 0x30000000 through 0x3000 Offf and the other at 0x3004 0000 through 0x3004 Offf 256 KB is 0x0004 0000 Locking and Unlocking Pages in Memory Note If two programs in the same system attempt to map different objects to the same absolute address the second attempt fails Locking and Unlocking Pages in Memory A page fault interrupts a process for many milliseconds Not only are page faults lengthy their occurrence and frequency are unpredictable A real time application cannot tolerate such interruptions The solution is to lock some or all of the pages of the address space into memory A page fault cannot occur on a locked page Memory Locking Functions You can use any of the functions summarized in Table 1 2 to lock memory Table 1 2 Functions for Locking Memory Function Name Compatibility Purpose and Operation mlock 3C POSIX Lock a specified range of addresses mlockall3C POSIX Lock the entire address space of the calling process mpin 3C IRIX Lock a specified range of addresses pl
227. gnal Handling 115 Functions for BSD Signal Handling 116 Functions for Timed Suspensions 117 Time Data Structures and Usage 118 POSIX Time Management Functions 120 POSIX Time Management Functions 120 BSD Functions for Interval Timers 125 Types of itimer 125 Abstract Operations on a Message Queue 128 POSIX Functions for Managing Message Queues 131 POSIX Functions for Using Message Queues 132 SVR4 Functions for Managing Message Queues 143 SVR4 Functions for Using Message Queues 145 Functions for File and Record Locking 158 Comparing Parallel Models 184 Documentation for Statement Level Parallel Products 189 Loop Scheduling Types 193 Commands and System Functions for Process Management 196 Functions for Child Process Management 199 Commands and Functions for Scheduling Control 200 POSIX Functions for Scheduling 202 Comparison of Pthreads and Processes 208 Header Files Related to Pthreads 209 Functions for Creating Pthreads 212 Functions for Managing Thread Execution 215 Functions for Thread Unique Data 219 Functions for Schedule Management 223 Functions for Preparing Mutex Objects 227 Functions for Using Mutexes 229 Functions for Preparing Condition Variables 230 List of Tables Table 11 10 Table 12 1 Table 13 1 Table 14 1 Table 14 2 Table 14 3 Table 14 4 Table 14 5 Table 14 6 Table 14 7 Table 14 8 Table 14 9 Table 14 10 Table 14 11 Table A 1 Functions for Using Condition Variables 231 Corresponding PVM and M
228. gnals allowed and blocked You must use pthread_sigmask in a program that is linked with libpthread Specify or query the signal handling policy for a specified signal Specify or query an alternate stack area to be used by a signal handler Return the set of signals pending for the calling process or thread Manipulate signal mask objects in memory Unblock selected signals for the calling process or thread and wait for a signal to be received asynchronously Wait for and receive specified signals in a synchronous manner 111 Chapter 5 Signalling Events 112 In addition to the reference pages listed in Table 5 3 the following have important information about signal handling signal 5 Detailed overview of signals and signal handling siginfo 5 Description of the information structure passed to a POSIX signal handler ucontext 5 Description of machine context structure passed to a POSIX signal handler Signal Masking Each process and thread has an active signal mask A single thread program sets or queries its signal mask using sigprocmask A multithreaded program any program that linked libpthread which provides the pthread version of the standard library must use pthread_sigmask Besides the active signal mask you may have other signal mask objects type sigset_t in memory The sigsetops 3 reference page documents a number of utility functions for setting clearing and testing the bits in a signal mas
229. gram could be in a different thread each time it stops The thread ID is displayed at the stop as in the display in Example 11 1 Example 11 1 Debugger Display of Pthread Program dbx showthread all Thread Start State Pid Location 0x10000 COND WAIT _SGIPT_sched_block xp c 966 0x10001 work_thread RUNNING 1512 FLOCAL_ALIGN workfn c 864 0x10002 work_thread RUNNING 1520 FLOCAL_ALIGN workfn c 850 0x10003 work_thread RUNNING 1563 FLOCAL_ALIGN workfn c 866 0x10004 gt work_thread RUNNING 1425 thr_tst workfn c 391 You can single step a threaded program as long as you know that only one thread is executing the code through which you are stepping When you single step through code that is executed by more than one thread confusing results can occur To single step dbx sets a breakpoint where the program should stop next However breakpoints are global When you give the next command in one thread the stop can occur in a different thread Debugging With the Workshop Debugger The Workshop Debugger is part of the Developer Magic package In version 2 6 2 of this package the debugger is aware of pthreads The command line view in the debugger main window can be used to set breakpoints and to produce a display similar to the one in Example 11 1 Breakpoints set with the Workshop Debugger are global to the program and are taken by the next thread to reach them as with dbx 211 Chapter 11 Thread Level
230. gram constructs executable code or reads it from a file the protection must be changed to executable before the code can be executed No access You can make pages inaccessible while retaining them as part of the address space Note The mprotect function changes the access rights only to the memory image of a mapped file You can apply it to the pages of a mapped file in order to control access to the file image in memory However mprotect does not affect the access rights to the file itself nor does it prevent other processes from opening and using the file as a file Synchronizing the Backing Store IRIX writes modified pages to the backing store as infrequently as possible in order to save time When pages are locked they are never written to backing store This does not matter when the pages are ordinary data When the pages represent a file mapped into memory you may want to force IRIX to write any modifications into the file This creates a checkpoint a known good file state from which the program could resume Additional Memory Features The msync function see the msync 2 reference page asks IRIX to write a specified segment to backing store The segment must be a whole multiple of pages You can optionally request e synchronous writes so the call does not return until the disk I O is complete ensuring that the data has been written e page invalidation so that the memory pages are released and will have to b
231. grams work on suitable terminals including internationalized terminal emulators Suitable means that the terminal supports any necessary fonts and understands the encoding of the application output Graphics programs simply do as they have always done Applications using existing interfaces to operate in non English or non ASCII environments should continue to compile and run under an internationalized operating system Multilingual Software A multilingual program is one that uses several different locales at the same time Examples are described in Multilingual Support on page 297 Areas of Concern in Internationalizing Software Few developers will have to pay attention to more than a few items described in this section Most will need to catalog their strings Some will need to use library routines for character sorting or locale dependent date time or number formatting A few whose applications use the eighth bit of 8 bit characters inappropriately will need to stop doing so The few applications that do arithmetic to manipulate characters will need to be cleaned up Some GUI designers will have to spend just a little more time thinking But for the large majority of developers there isn t much to do Overview The information presented in the following sections addresses internationalization issues pertinent to a developer some sections however may not be relevant to your applications Standards IRIX internation
232. h previous versions of libraries Multiple message buffers and their functionality in PVM can be emulated by communicators in MPI Utility Functions Most utility functions in PVM have corresponding setup options in the parallel setup facility that comes with a particular MPI implementation Some of these utility functions may not be available note however that these functions do not directly affect the basic characteristics of the application Instead they are provided as a convenience to programmers Such functions include pvm_catchout pym_getopt pym_setopt and pvm_tidtohost A PVM task has a parent task whose task ID is returned by the pym_parent call Since MPI tasks are not spawned by other MPI tasks this concept of a parent task does not exist in MPI Hence you must remove all instances of pym_parent and handle their logical consequences in the program For instance one of the most common reasons for finding out the parent s task ID is to send computation result messages back to it this functionality can be easily replicated in an MPI program or even a PVM program by a task declaring itself to be the logical parent to whom all the computation result messages should be sent Example Programs Example Programs The two examples in this section illustrate some of the porting concepts presented in this chapter The first one is a SPMD program where all the tasks are instances of the same executable here the firs
233. he virtual address spaces of two or more concurrent processes see Chapter 3 Sharing Memory Between Processes Two processes can transfer data at memory speeds one putting the data into a mapped segment and the other process taking the data out They can coordinate their access to the data using semaphores located in the shared segment see Chapter 4 Mutual Exclusion Multiple Memory Systems Inan Array system such as a POWER CHALLENGEarray each node is a computer built on the CHALLENGE Onyx architecture However the only connection between nodes is the high speed HIPPI bus between nodes The system does not offer a single system memory instead there is a separate memory subsystem in each node The effect is that e There is not a single address map A word of memory in one node cannot be addressed at all from another node e There is a time penalty for some interprocess communication When data passes between programs in different nodes it passes over the HIPPI network which takes longer than a memory to memory transfer e Peripherals are accessible only in the node to which they are physically attached Nevertheless it is possible to design an application that executes concurrently in multiple nodes of an Array The message passing interface MPI is designed specifically for this Parallel Execution Models You can compare the available models for parallel programming on two features granularity The relat
234. he semantics of SVR3 compatible signal established with signal are not desirable for most programs When control enters a signal handler you established using signal the handling of that same signal is set to default and that signal remains unblocked Your signal handler can use signal to reestablish itself as the handler or it can use sighold to block the signal However even if these actions are the first statements of the handler function there is a period of time at the beginning of the handler during which a second signal of the same type could be received If this occurs the second signal receives default handling and is not seen by your handler 115 Chapter 5 Signalling Events 116 You can avoid this problem by using the SVR4 function sigset instead of signal to establish a handler Before a handler established by sigset is called that signal is blocked until the handler returns and the signal disposition is not reset to default BSD Signal Facility The BSD signal facility is compatible with code ported from the BSD 4 2 distribution Table 5 5 summarizes the functions you use to manage signals with this interface Note In order to use any of the functions in Table 5 5 you must define one of the compiler variables _BSD_SIGNALS or _BSD_COMPAT prior to the inclusion of the header file signal h You can do this directly in the source file with define More commonly you will include D_BSD_COMPAT as one of the com
235. he value of a semaphore is not preserved over a reboot the POSIX standard says it is not valid to depend on the value of a semaphore over a reboot A named semaphore is opened as a file and takes up one entry in the file descriptor table for the process There is no way to convert between the address of the sem_t and the file descriptor number or vice versa As a result you cannot directly pass the semaphore to a function such as fentl or chmod 75 Chapter 4 Mutual Exclusion 76 Closing and Removing a Named Semaphore When a process stops using a named semaphore it can close the semaphore releasing the associated file descriptor slot This is done with sem_close The semaphore name persists in the filesystem and as long as the system is up the current semaphore value persists in a table in memory To permanently remove a semaphore use sem_unlink Using Semaphores POSIX named and unnamed semaphores can be used to coordinate the actions of IRIX processes and POSIX threads They are the only mutual exclusion objects that can be freely used to coordinate between threaded and unthreaded programs alike Message queues can be used between threaded and unthreaded programs also see Chapter 6 Message Queues The functions that operate on semaphores are summarized in Table 4 3 Table 4 3 POSIX Functions to Operate on Semaphores Function Name Purpose and Operation sem_getvalue 3 Return a snapshot of th
236. hich message from which catalog to look for Flag details are discussed in the following section The format is discussed in the Format Strings for pfmt on page 331 Labels Severity and Flags pfmt flags are composed of several groups specify no more than one from each group Specify multiple flags by using OR The groups are as follows output format control MM_NOSTD MM_STD catalog access control MM_NOGET MM_GET severity MM_HALT MM_ERROR MM_WARNING MM_INFO action message specification MM_ACTION pfmt prints messages in the form label severity text Severity is specified in the flags The text comes from a message catalog or a default as specified in the format and the label is specified earlier by the application In the example above if no label has been set we get only the output ERROR Permission denied Strings and Message Catalogs Typically an application sets the label once early in its life subsequent error messages have the label prepended For example setlabel UX myprog pfmt stderr MM_ERROR MQ 64 Permission denied would produce by default UX myprog ERROR Permission denied For details consult the pfmt 3 and setlabel 3 reference pages Format Strings for pfmt pfmt format strings are of this form catalog messagenum defaultstring The catalog field is in the format described in Specifying MNLS Catalogs on page 329 messagenum is
237. hm is in conflict with the stringent needs of a real time program which needs to dedicate predictable amounts of hardware capacity to its processes without regard to fairness The Frame Scheduler seizes one or more CPUs of a multiprocessor isolates them and executes a specified set of processes on each CPU in strict rotation The Frame Scheduler has much lower overhead than the normal IRIX scheduler and it has features designed for real time work including detection of overrun when a scheduled process does not complete its work in the necessary time and underrun when a scheduled process fails to execute in its turn At this writing there are no real time applications that use multiple nodes of an Array system 205 Chapter 11 Thread Level Parallelism IRIX supports IEEE standard 1003 1c 1995 System Application Program Interface Amendment 2 Threads Extension that is it supports POSIX threads or pthreads Pthreads are supported by IRIX 6 2 after the following patches are applied 1361 1367 and 1429 In addition the Silicon Graphics implementation of the Ada 95 language includes support for multitasking Ada programs The current implementation of Ada uses an early version of the pthreads library The next release of Ada will use the POSIX library For a complete discussion of the Ada 95 task facility refer to the Ada 95 Reference Manual which installs with the Ada 95 compiler GNAT product This chapter cont
238. hout Conversion int cLen char tStr pStr numChars 0 cLen mbtowc wchar_t NULL tStr MB_CUR_MAX while cLen gt 0 tStr cLen numCharstt cLen mbtowc wchar_t NULL tStr MB_CUR_MAX if cLen 1 numChars cLen invalid MB character Wide Characters A wide character WC or wehar is a data object of type wehar_t which is guaranteed to be able to hold the system s largest numerical code for a character wchar_t is defined in stdlib h Under IRIX 4 0 x sizeof wchar_t was 1 In IRIX 5 1 and above it is 4 All wchars on a system are the same size independent of locale encoding or any other factors Uses for wchar Strings The single advantage of WC strings is that all characters are the same size Thus a string can be treated as an array and a program can simply index into the array in order to modify its contents Most applications char manipulation routines work with little modification other than a type change to wchar_t with appropriate attention to byte count and sizeof So when applications have significant string editing to perform they typically keep the strings in WC format while doing that editing Those WC strings may or may not be converted to or from MB strings at other points in the application Wide characters are often large and are not as space efficient as multibyte strings Applications that do not need to perform string editing probably shouldn t use wehars If
239. ice versa Also the two programs will disagree about the size and offset of structure fields when structures contain addresses For example if you initialize an allocation arena with acreate from a 64 bit program a 32 bit program calling amalloc on that same arena will almost certainly crash or corrupt the arena pointers You can use POSIX shared memory SVR4 shared memory or basic mmap to share a segment between a 32 bit and a 64 bit program provided you take extreme pains to ensure that both programs view the data contents as having the same binary structure and that no addresses are shared You cannot use an IRIX shared memory arena between 32 bit and 64 bit programs at all because the arena support stores addresses in the arena POSIX Shared Memory Operations POSIX Shared Memory Operations Shared memory support specified by POSIX is based on the functions summarized in Table 3 1 Table 3 1 POSIX Shared Memory Functions Function Name Purpose and Operation mmap 2 Map a file or shared memory object into the address space shm_open 2 Create or gain access to a shared memory object shm_unlink 2 Destroy a shared memory object when no references to it remain open The use of mmap is described at length under Mapping Segments of Memory on page 11 In essence mmap takes a file descriptor and makes the contents of the described object accessible as a segment of memory in the address space In IRIX a file
240. ics General impression of the document Omission of material that you expected to find Technical errors Relevance of the material to the job you had to do Quality of the printing and binding Please send the title and part number of the document with your comments The part number for this document is 007 2478 004 Thank you Three Ways to Reach Us To send your comments by electronic mail use either of these addresses On the Internet techpubs sgi com For UUCP mail through any backbone site your_site sgi techpubs To fax your comments or annotated copies of manual pages use this fax number 415 965 0964 To send your comments by traditional mail use this address Technical Publications Silicon Graphics Inc 2011 North Shoreline Boulevard M S 535 Mountain View California 94043 1389
241. ify a page a hardware interrupt occurs The kernel makes a copy of that page and changes the new address space to point to the copied page Then the process continues to execute modifying the page of which it now has a unique copy You can apply the copy on write discipline to the pages of an arena shared with other processes see Mapping a File for Shared Memory on page 18 Interrogating the Memory System 10 You can get information about the state of the memory system with the system calls shown in Table 1 1 Table 1 1 Memory System Calls Memory Information System Call Invocation Size of a page uiPageSize getpagesize ulPageSize sysconf _SC_PAGESIZE Virtual and resident sizes of a process syssgi SGI_PROCSZ pid amp uiSZ amp uiRSS Maximum stack size of a process uiStackSize prctl PR_GETSTACKSIZE Free swap space in 512 byte units swapctl SC_GETFREESWAP amp uiBlocks Mapping Segments of Memory Table 1 1 continued Memory System Calls Memory Information System Call Invocation Total physical swap space in 512 byte swapctl SC_GETSWAPTOT amp uiBlocks units Total real memory sysmp MP_KERNADDR MPSA_RMINFO amp rmstruct Free real memory sysmp MP_KERNADDR MPSA_RMINFO amp rmstruct Total real memory swap space sysmp MP_KERNADDR MPSA_RMINFO amp rmstruct The structure used with the sysmp call shown above has this form a more detailed layout is in sys sysmp h str
242. ifying the key Apply IPC_NOWAIT to all following operations Apply SEM_UNDO to all following operations Apply the P decrement by 1 operation to sem for example p 1 97 Chapter 4 Mutual Exclusion 98 v sem Apply the V increment by 1 operation to sem for example v 1 Z sem Wait for sem to contain 0 for example z 4 You can give a sequence of operations For example consider the following sequence 1 Wait for zero in semaphore 4 2 Increment semaphore 0 with undo if a following operation fails 3 Decrement semaphore 2 not waiting and with undo 4 Decrement semaphore 3 not waiting and with undo The sequence above can be specified as follows semop k 0x101 z 4 u v 0 n p 2 p 3 The program does not support incrementing or decrementing by other than 1 and there is no way to turn off IPC_NOWAIT or SEM_UNDO once it is on Example 4 6 Program to Demonstrate semop semop program to test semop 2 for all functions semop k lt key gt i lt semid gt n u p lt n gt v lt n gt z lt n gt k lt key gt the key to use or i lt semid gt the semid to use n use the IPC_NOWAIT flag on following ops u use the SEM_UNDO flag on following ops p lt n gt do the P operation 1 on semaphore lt n gt v lt n gt do the V operation 1 on semaphore lt n gt z lt n gt wait for lt n gt to become zero xy include lt unistd h gt
243. ight end up with networked communications with an input method server and a kanji translation server with circuitous paths for Key events But in a Swiss locale for example it is likely that nothing would occur besides a flag or two being set in Xlib Since operating in non Asian locales ends up bypassing almost all of the things that might make input methods expensive Western users are not noticeably penalized for using Asia ready applications Opening an Input Method XOpenIM opens an input method appropriate for the locale and modifiers in effect when it is called see the XOpenIM 3X11 reference page The locale is bound to that IM and cannot be changed But you could open another IM if you wanted to switch later Strings returned by XmbLookupString and XwcLookupString are encoded in the locale that was current when the IM was opened regardless of current input context 347 Chapter 14 Internationalizing Your Application 348 The syntax is XIM XOpenIM Display dpy XrmDataBase db char res_name char res_class The res_name is the resource name of the application res_class is the resource class and db is the resource database that the input method should use for looking up resources private to itself Any of these can be NULL The fragment in Example 14 7 shows how easy it is to open an input method Example 14 7 Opening an IM XIM im im XOpenIM dpy NULL NULL NULL if im NULL exit_with_error
244. ike this char obj color make choices printf s s n color obj The printf call produces this white house Even once we make sure that obj and color are localized strings we are not quite finished If our locale is Spanish the printf yields blanca casa That is incorrect grammar in Spanish it should be casa blanca The solution to this problem is variably ordered referencing of printf arguments The syntax of printf format strings has been expanded to deal with this The original definition of printf is that each conversion specification T where T represents any of the printf conversion characters is implicitly matched to an argument value by position In order to deal with variably ordered strings printf allows an argument position index D to appear in the conversion specification following the so that where a format string contains T it can now contain D T The value D set off by a currency symbol selects the argument from the argument list to be used This means you can write printf 2nd parameter is 2Ss the lst is 15s pl p2 333 Chapter 14 Internationalizing Your Application 334 The second parameter is printed first with the first parameter printed second For example char store Macy s char obj a cup printf At 1 s I bought 2Ss n store obj printf I bought 2Ss at 1 s n store obj This code displays At Macy s I bo
245. iles related to pthreads functions are summarized in Table 11 2 Table 11 2 Header Files Related to Pthreads Header Primary Contents errno h System error codes returned by pthreads functions pthread h Pthread functions and special pthread data types sched h The sched_param structure and related functions used in setting thread priorities 209 Chapter 11 Thread Level Parallelism 210 Table 11 2 continued Header Files Related to Pthreads Header Primary Contents stdio h Standard stream I O macros including thread safe versions sys types h IRIX and standard data types limits h Some POSIX constants such as _POSIX_THREAD_THREADS_MAX unistd h Constants used when calling sysconf to query POSIX limits see the sysconf 3 reference page Prior to the inclusion of stdio h be sure that the compiler variables _POSIX1C and _NO_ANSIMODE are defined These variables are set by default in most compiles Read the header file usr include standards h which is included by stdio h to see the logic of standard namespace definition You can use pthreads with a program compiled to any of the supported execution models 32 for compatibility with older systems n32 for 64 bit data and 32 bit addressing or 64 for 64 bit addressing The pthreads functions are defined in the library libpthread so Link with this library using the lpthread compiler option which should be the last library on the command line The compile
246. ime passing CLOCK_SGI_CYCLE e Inorder to find out the resolution update frequency of the cycle counter call clock_getres passing CLOCK_SGI_CYCLE e Inorder to find out the precision of the cycle counter call syssgi passing SGI_CYCLECNTR_ SIZE The returned value is the number of bits in the counter The first two operations are illustrated in Example 5 1 on page 121 Chapter 6 Message Queues You use a message queue to pass blocks of data between processes or threads without having to share any memory between the processes One process or thread puts a message into the queue The message is held in the queue until another process or thread asks for the message IRIX supports two implementations of message queues a POSIX implementation as specified by IEEE standard 1003 1b 1993 and an SVR4 implementation compatible with System V Release 4 Both implementations can be used to coordinate POSIX threads or IRIX processes This chapter discusses message queues under these headings e Overview of Message Queues on page 128 describes message queues and the differences between the two implementations e POSIX Message Queues on page 130 documents the use of the POSIX implementation e System V Message Queues on page 143 documents the use of the SVR4 implementation 127 Chapter 6 Message Queues Overview of Message Queues A message queue is a software object maintained by the IRIX kernel logica
247. implementation could be created for the homogenous environment of Silicon Graphics Array systems Under Array 2 0 MPI applications take advantage of a HIPPI bypass connection to exchange data with small latencies and high data rates Specific data rates and latencies are listed with much more about Array systems in the book Getting Started With Array Systems 007 3058 002 The PVM implementation for Array systems is not as highly tuned although still effective for some work Another difference between MPI and PVM is in the support for the topology the interconnect pattern grid torus or tree of the communicating processes In MPI the group size and topology are fixed when the group is created This permits low overhead group operations The lack of run time flexibility is not usually a problem because the topology is normally inherent in the algorithmic design In PVM group composition is dynamic which requires the use of a group server process and causes more overhead in common group related operations Choosing Between MPI and PVM Other reasons can be found in the design details of the two interfaces MPI for example supports asynchronous and multiple message traffic so that a process can wait for any of a list of message receive calls to complete and can initiate concurrent sending and receiving MPI provides for a context qualifier as part of the envelope of each message This permits you to build e
248. imply by using a semaphore lock or barrier that was allocated within that arena These function calls perform an automatic call to usadd However they can also encounter the error that too many processes are already using the arena It is best for the child process to check for this condition with an explicit call to usadd Allocating in an Arena Allocating shared memory from a shared arena is much like the regular process of allocating memory using the malloc and free library routines The functions related to allocation within an arena are summarized in Table 3 4 Table 3 4 IRIX Shared Memory Arena Allocation Functions Function Name Purpose and Operation usmalloc 3 Allocate an object of specified size in an arena uscalloc 3 Allocate an array of zero filled units in an arena usmemalign 3 Allocate an object of specified size on a specified alignment boundary in an arena usrealloc 3 Change the allocated size of an object in an arena usrealloc 3 Change the allocated size of an array created with uscalloc usmallocblksize 3 Query the actual size of an object as allocated usfree 3 Release an object allocated in an arena usmallopt 3 Tune the allocation algorithm using constants described in amallopt 3 usmallinfo 3 Query allocation statistics see amallinfo 3 for structure fields IRIX Shared Memory Arenas The address of an object allocated using usmalloc or a related function is a valid address i
249. in use at any given time Codeset 0 Oxxxxxxx Codeset 1 1XXXXXXX 1XXXXXXX Codeset 2 ssl 1xxxxxxx 1xxxxxxx Codeset 3 ss2 1xxxxxxx 1xXxxxxxx Popular Encodings So if ss appears in a string it means that the next character however many bytes long it is should be interpreted as a character from codeset 2 If there are multiple characters in a row from codeset 2 each one is preceded by ss1 Similarly ss2 indicates that the following character belongs to codeset 3 If any other byte whose high bit is 1 appears in the string without being preceded by s51 or ss2 it is interpreted as all or part of a character from codeset 1 In EUC codeset 1 is always ASCII The other codesets are implementation or user defined This is why EUC cannot support Latin 1 in Asian locales EUC implementations exist but are not standardized for all ideographic Asian languages ISO 10646 and Unicode ISO and the Unicode Consortium have jointly developed a character set designed to cover almost every character normally used by any language in the world The characters have two and four byte representations ISO calls this ISO IS 10646 The Unicode Consortium embraces a subset of 10646 called the Basic Multilingual Plane BMP of 10646 and calls it Unicode The only characters defined in either standard are the characters in the BMP It appears that ISO 10646 will grow significantly in acceptance but widespread use i
250. individual task ID and the master s task ID This is just one of the many schemes by which this can be implemented Also instead of packing and unpacking used in the MPI version MPI derived datatypes could have been used MPMD in PVM Version Master Task include lt stdio h gt include pvm3 h define SLAVENAME slavel main int mytid my task id int tids 32 slave task ids int n nproc numt i who msgtype nhost narch float data 100 result 32 struct pvmhostinfo hostp 32 enroll in pvm mytid pyvm_mytid Set number of slaves to start Example Programs Can not do stdin from spawned task if pvm_parent PvmNoParent puts How many slave programs 1 32 scanf d amp nproc else pvm_config amp nhost amp narch hostp nproc nhost if nproc gt 32 nproc 32 start up slave tasks numt pvm_spawn SLAVENAME char 0 0 nproc tids if numt lt nproc printf Trouble spawning slaves Aborting printf Error codes are n for i numt i lt nproc i printf TID d d n i tids i for i 0O i lt numt itt pvm_kill tids i pvm_exit exit Begin User Program n 100 initialize_data data n for i 0 i lt n i data i 1 Broadcast initial data to slave tasks pvm_initsend PvmDataDefault pyvm_pkint
251. information at run time Individual items of langinfo data are identified by constants in Volume 2 XSI System Interfaces and Headers lt langinfo h gt Information specific to a culture or language includes the following Date and time formats Days of the week and months of the year Abbreviated names of days and months Radix character Separator for thousands Affirmative and negative responses to yes no questions Currency symbol and its position within a currency value Locale Specific Behavior Using Regular Expressions Regular expression are used widely throughout the services and are powerful mechanisms for locating and manipulating patterns in text In order to be compatible with a variety of historic UNIX systems the IRIX Developer s Option includes the unique regular expression library sets listed in Table 14 6 Note that only the last wsregexp supports internationalization Table 14 6 Regular Expression Libraries in IRIX Library Documentation Type of Support Provided regcemp 3G Function regemp compiles a pattern string regex applies the pattern to a target string Syntax is said to be that of ed but syntax and semantics have been changed slightly in unspecified ways regcmp 1 Command applies regemp against a file of pattern strings generating C code for literal strings that can be included in a source program so as to preclude having to compile patterns at run time REGEX 3 Function re_c
252. ing 325 Mexico country code 369 MIPS ABI reserved address space 22 mmap 12 23 and file permissions 17 and NFS mounted files 17 in place of Iseek 16 of dev mem 19 of dev mmem 20 of dev ume 20 of zero segment 19 parameters of 12 18 using specified addresses 22 when swap is allocated 15 MNLS Also see message catalogs message catalogs 328 333 monitor resolution 264 Motif internationalization 342 377 Index MPI converting PVM program to 244 258 differences from PVM 238 240 msync 15 31 multibyte characters See internationalization multibyte characters multilingual support 297 N names country 367 nationalized software 288 New Zealand country code 369 NFS and memory mapped files 17 Nigeria country code 369 NLSPATH 326 0 Off the Spot style 350 On the Spot style 351 open 12 of dev zero 19 Over the Spot style 350 P page copy on write 10 locking 23 read only 10 releasing unneeded 31 page fault prevent by locking memory 23 page size 5 page validation 9 378 parallel programming 39 path fonts 270 performance effects of cache 27 performance tools 29 pixie command 29 plock example of 24 polled semaphore 78 Portugal country code 369 POSIX and IPC 36 PostScript printers 280 printers PostScript 280 printf 333 printf message catalogs 333 process address space 4 prof command 29 programming fonts 266
253. ing and each use of creat open read and write tests for contending locks Some points to remember about mandatory locking e Mandatory locking does not protect against file truncation with the truncate function see the truncate 2 reference page which does not look for locks on the truncated portion of the file e Mandatory locking protects only those portions of a file that are locked Other portions of the file that are not locked may be accessed according to normal UNIX system file permissions e Advisory locking is more efficient because a record lock check does not have to be performed for every I O request Record Locking Across Multiple Systems 174 Record locking is always effective within a single copy of the IRIX kernel Locking is effective within a multiprocessor because processes running in different CPUs of the multiprocessor share a single copy of the IRIX kernel Record locking can be effective on processes that execute in different systems that access a filesystem mounted through NFS However there are these drawbacks e Deadlock detection is not possible between processes in different systems e You must make sure that the NFS locking daemon is running in both the NFS client application and server systems e Using record locking on NFS files has a strong impact on performance NFS File Locking When a process running in an NFS client system requests a file or record lock a complex sequence of
254. ing program can create and modify files in the critical directory but other programs started by an ordinary user cannot Using Record Locking This section covers the following topics e Opening a File for Record Locking e Setting a File Lock e Setting and Removing Record Locks e Getting Lock Information e Deadlock Handling Opening a File for Record Locking The first requirement for locking a file or segment of a file is having a valid open file descriptor If read locks are to be used then the file must be opened with at least read access likewise for write locks and write access Example 7 1 opens a file for both read and write access Example 7 1 Opening a File for Locked Use include lt stdio h gt include lt errno h gt include lt fcntl h gt int fd file descriptor char filename main argc argv int argc char argv extern void exit perror get database file name from command line and open the file for read and write access 161 Chapter 7 File and Record Locking 162 EJ if argc lt 2 void fprintf stderr usage s filename n argv 0 exit 2 filename argv 1 fd open filename O_RDWR if fd lt 0 perror filename exit 2 The file is now open to perform both locking and I O functions The next step is to set a lock Setting a File Lock Several ways exist to set a lock on a file These method
255. int i dest MPI_Status status float psum 0 0 float sum 0 0 char outbuff 100 for i 0 i lt n i sum me datal i illustrate node to node communication dest mytid l if dest ntasks dest 0 if dest master dest t MPI_Buffer_attach outbuff 100 int master MPI_Bsend amp sum 1 MPI_FLOAT dest 22 MPI_COMM_WORLD MPI_Recv amp psum 1 MPI_FLOAT MPI_ANY_SOURCE 22 MPI_COMM_ WORLD amp status return sum psum PART FOUR Working With Fonts Chapter 13 Working With Fonts Describes the use of fonts and font metric files within the X window system and the installation of bit mapped and Type 1 fonts Chapter 13 Working With Fonts This chapter describes how to work with fonts on Silicon Graphics computers It begins with an introduction to fonts and digital typography Then it explains which fonts are available and how to install additional fonts It also covers how to download outline fonts in the Type 1 format to a PostScript printer This chapter contains these sections e Font Basics defines fonts and provides some general background information e Using Fonts With the X Window System discusses some of the most useful font utilities of the X Window System e Installing and Adding Font and Font Metric Files explains how to install and add font files and font metric files for system wide use e Downloadi
256. interfaces Each one is designed around a different set of assumptions about the hardware especially the memory system Each model is implemented using a different library of code linked with your program In some cases you can design a mixed model program but in general this is a recipe for confusion Parallel Programs on Uniprocessors It might seem a contradiction but it is possible to execute some parallel programs in uniprocessors Obviously you would not do this expecting the best performance However it is easier to debug a parallel program by running it in the more predictable environment of a single CPU on a multiprocessor or on a uniprocessor workstation Also you might deliberately restrict a parallel program to one CPU in order to establish a performance baseline Most parallel programming libraries adapt to the available hardware They run concurrently on multiple CPUs when the CPUs are available up to some programmer defined limit They run on a limited number or even just one CPU when necessary For example the Fortran programmer can control the number of CPUs used by a MIPSpro Fortran 77 program by setting environment variables before the program starts see Chapter 9 Statement Level Parallelism Types of Memory Systems The key memory issue for parallel execution is this Can one process access data in memory that belongs to another concurrent process and if so what is the time penalty for doing so The answ
257. interpreter in your printer by sending the following file to that printer oe 1 Produce a list of available fonts 100 string def Times Roman findfont 12 scalefont setfont y 700 def 72 y moveto FontDirectory pop f cvs show 72 y y 13 sub def y moveto forall showpage Utopia fonts are not usually built into PS printers If you try to print a document that requires a Utopia font on a PS printer that does not have that font a warning message about the replacement of a missing font with a Courier font is sent to the file usr spool lp log on the system to which that PS printer is attached You can download a Type 1 font to a PS printer in either of the following two ways e You can insert a Type 1 font file at the beginning of the PostScript file that needs that font You should have a statement that starts with oe Put this statement at the beginning of your PS file If you have two such lines delete the second one When you download a font this way the font is available only while your print job is being processed e You can make a copy of a Type 1 font file and then insert the statement serverdict begin 0 exitserver after the first group of comment statements lines that start with if no password has been specified for your printer otherwise replace 0 in the above statement with the password for your printer Then send the edited file to your printer Downloading a Type 1 Font to a PostScript Printer
258. into the page copy on write This prevents the change from being seen by any other process that uses or maps the same file and it protects the process from detecting any change made to that page by another process However this applies only to pages that have been written into Frequently you cannot use MAP_PRIVATE because it is important to see data changes and to share them with other processes that map the same file However it is also important to prevent an unrelated process from truncating the file and so causing SIGBUS exceptions The one sure way to block changes to the file is to install a mandatory file lock You place a file lock with the lockf function see Chapter 7 File and Record Locking However a file lock is normally advisory that is it is effective only when every process that uses the file also calls lockf before changing it You create a mandatory file lock by changing the protection mode of the file using the chmod function to set the mandatory file lock protection bit see the chmod 2 reference page When this is done a lock placed with lockf is recognized and enforced by open Mapping a File for Shared Memory You can use mmap simply to create a segment of memory that can be shared among unrelated processes e Inone process create a file or a POSIX shared memory object to represent the segment Typically a file is located in var tmp but it can be anywhere The permissions on the
259. is considered part of the font design Typographers use small units of measure called points to specify font size A point is approximately equal to 1 72 of an inch The exact value is 1 72 27 0 013837 of an inch or 0 351 mm A point is a device independent unit of measure Its size does not depend on the resolution of an output device A 12 point font should have approximately the same size on different output devices regardless of the resolution of those devices Font Basics If the resolution of an output device is equal to 72 dots per inch dpi the size of a dot or pixel is approximately equal to the size of a point If the resolution of an output device is greater than 72 dpi the size of a dot or pixel is smaller than the size of a point and vice versa You can use the following formula to calculate a pixel size from a point size pixel siz point size x device resolution 72 27 A bitmap font is usually designed for a particular resolution Such a font has the point size specified by its designer only when it is used on an output device whose resolution matches the resolution for which that font was designed This is because a font designer specifies a fixed bitmap for each character If a pixel is smaller than a point characters will be smaller than intended and vice versa Font Names When a font is designed it is assigned a name such as Courier Oblique This font belongs to a font family called Courier which inclu
260. is why the functions are shown as having a variable number of arguments When you do so the compiler cannot move assignments to the named variables across this point but can move assignments to other variables if the optimizer needs to System V Facilities for Mutual Exclusion System V Facilities for Mutual Exclusion The System V Release 4 SVR4 semaphore facility lets you create persistent semaphores that can be used to coordinate any processes or threads The SVR4 facility differs from POSIX named semaphores in two ways e Each object is a set of from 1 to 25 independent semaphores rather than a single semaphore A process can operate on any selection of semaphores in a set in one system call e You can use SVR4 semaphores in ways that IRIX and POSIX do not support incrementing or decrementing by more than 1 and waiting for a zero value e The name of a set is an integer in a kernel table rather than a pathname in the filesystem see SVR4 IPC Name Space on page 40 The functions used to create and operate on semaphore sets are summarized in Table 4 11 Table 4 11 SVR4 Semaphore Management Functions Function Name Purpose and Operation semget 2 Create a semaphore set or return the ID of a semaphore set semctl 2 Query or change semaphore values query or change semaphore set attributes semop 2 Perform operations on one or more semaphores in a set Semaphores are also discussed in the intro 2 referen
261. ish whether the arena can be attached by general processes or only by members of one program a share group 51 Chapter 3 Sharing Memory Between Processes 52 Table 3 3 continued Arena Features Set Using usconfig usconfig Flag Name Meaning CONF_LOCKTYPE Whether or not lock objects allocated in the arena collect metering statistics as they are used CONF_ATTACHADDR An explicit memory base address for the next arena to be created see Choosing a Segment Address on page 21 CONF_HISTON Start and stop collecting usage history more bulky than metering CONF_HISTOFF information for semaphores in a specified arena CONF_HISTSIZE Set the maximum size of semaphore history records See the usconfig 3 reference page for a complete list of attributes The use of metering and history information for locks and semaphores is covered in Chapter 4 Mutual Exclusion Tip In programs that use an arena and start a varying number of child processes it is a common mistake to find that the eighth child cannot be created simply because usconfig has not been called with CONF_INITUSERS to set a higher number of users before the arena was created Creating an Arena After setting the arena attributes with usconfig the program calls usinit specifying a file pathname string Tip The mktemp library function can be used to create a unique temporary filename see the mktemp 3C reference page If the
262. it is delivered to the first thread that is not blocking that signal If all threads block that signal the signal remains pending until some thread unblocks the signal or the process ends While the process runs a thread can find out which signals are pending by calling sigpending This function returns a mask showing the combination of signals pending for the process as a whole and for the calling thread that is the signals that could be delivered to the calling thread if the signals were not blocked Setting Signal Actions When a signal is not blocked and is delivered some action is taken You specify what that action should be using the sigaction function Specify an action for each signal number separately These actions are set on a process wide basis not individually for each thread Each thread has a private signal mask but signal actions are specified for all threads in the process Choose among the following actions for each signal SIG_DFL Default handling which depends on the specific signal but is either to ignore the signal or to terminate the process with or without a dump SIG_IGN Ignore the signal that is discard it when it is generated Certain signals cannot be ignored function address Signal is delivered by an asynchronous call to the specified function When a signal is delivered to a function you have the option of specifying a function that receives a siginfo_t structure with information about the
263. ithout voluntarily suspending the lower its dispatching priority becomes This strategy keeps a runaway process from monopolizing the hardware However you may have a CPU intensive application that needs a predictable execution rate This is the purpose of nondegrading priorities set with schedctl NDPRI or with the npri command see the npri 1 reference page There are three bands of nondegrading priorities designated by symbolic names declared in sys schedctl h e A real time band from NDPHIMAX to NDPHIMIN System daemons and real time programs run in this band which has higher priority than any interactive process e Anormal band from NDPNORMMAX to NDPNORMMIN These values have the same priority as interactive programs Processes at these priorities compete with interactive processes but their priorities do not degrade with time e Abatch band from NDPLOMAX to NDPLOMIN Processes at these priorities receive available CPU time and are scheduled from a batch queue Tip The IRIX priority numbers are inverted in the sense that numerically smaller values have superior priority For example NDPHIMAX is 30 and NDPHIMIN is 39 However as long as you declare priority values using symbolic expressions the numbers work out correctly For example the statement define NDPHIMIDDLE NDPHIMIN NDPHIMAX NDPHIMIN 2 produces a middle value of 35 as it should When you create a cooperating group of processes it is important tha
264. ive size of the unit of computation that executes in parallel a single statement a function or an entire process communication The basic mechanism by which the independent concurrent units channel of the program exchange data and synchronize their activity 183 Chapter 8 Models of Parallel Computation 184 A summary comparison of the available models is shown in Table 8 1 Table 8 1 Comparing Parallel Models Model Granularity Communication Power Fortran IRIS Looping statement DO or for Shared variables in a single user POWER C statement address space Ada95 tasks Ada Procedure Shared variables in a single user address space POSIX threads C function Shared variables in a single user address space Lightweight UNIX processes C function Arena memory segment in a sproc single user address space General UNIX processes Process Arena segment mapped to fork exec multiple address spaces Portable Virtual Memory Process Memory copy within node PVM HIPPI network between nodes Message Passing MPI Process Memory copy within node special HIPPI Bypass interface between nodes Process Level Parallelism A UNIX process consists of an address space a large set of process state values and one thread of execution The main task of the IRIX kernel is to create processes and to dispatch them to different CPUs so as to maximize the utilization of the system IRIX contains a variety of interpr
265. ives the second signal is discarded In other words at most one signal of a given number can normally be pending for a process In the POSIX interface you can use one particular function sigqueue to send a signal that is queued regardless of how many signals of the same number are already pending Signal Handling Policies You can specify one of three policies for handling an unblocked signal You set the policy for each signal number individually Default Handling Initially all signals receive default handling This means that when a signal arrives and is not blocked it causes the default action listed in Table 5 1 In many cases the default action is to ignore the signal that is to silently discard it In other cases the default action is to terminate the program or to terminate it with a dump Each signal interface gives you a way to specify non default handling or a specified signal or to return a signal to default handling Signals Ignoring Signals You can request that a specified signal be ignored You would do this when the signal is not meaningful to your program and the default action is not what you wish For example in a noninteractive program you might set Ignore handling for SIGHUP the default action is to terminate Catching Signals You can request that a signal be caught and handled asynchronously at the moment it arrives You specify that a signal should be caught by specifying the address of a func
266. ize the MPI environment MPI_Init amp argc amp argv Get task id and the total number of tasks The rank is essentially the task id MPI_Comm_rank MPIT_COMM_WORLD amp taskId MPI_Comm_size MPI_COMM_WORLD amp numTasks Task Environment Cleanup Replace the pym_exit call at the end of each PVM program with the MPI_Finalize call which cleans up all MPI states This call should be the last MPI routine in a program You must ensure that all pending communications involving a process complete before the process calls MPI_Finalize Group Management Functions As far as groups are concerned the main difference between PVM and MPI is that PVM groups can be dynamic whereas MPI groups are static In PVM a task can belong to multiple groups and can join and leave a group an arbitrary number of times so that groups can change dynamically at any time during a computation Additionally arbitrary groups can be formed by tasks In contrast in MPI a group cannot be built from scratch but only from other groups that have been defined previously MPI has two predefined groups MPI_GROUP_EMPTY a group with no members and the group associated with the initial communicator MPI_COMM_WORLD consisting of all processes which forms the base group upon which all other groups are defined If the PVM program uses dynamic groups modify it to use only static groups before it can be ported to an MPI program Note that most app
267. k For example on a keyboard that had a diaeresis and an O but no O you would strike and then o to compose O Implicit composition support usually comes with some specified way to leave characters uncomposed Supported Keyboards IRIX currently supports 12 keyboard layouts American Belgian Danish English French German Italian Norwegian Portuguese Spanish Swedish and Swiss All are representable in Latin 1 the American keyboard needs only ASCII User Input Input Methods IMs Input methods IMs are ways to translate keyboard input events into text strings You would use a different input method for instance to type on a USA keyboard in Chinese than to type on the same keyboard in English Nobody would build a keyboard suitable for direct input of the tens of thousands of distinct Chinese characters IMs come in two flavors front end and back end Both types can use identical application programming interfaces so you lose no generality by using back end methods for our examples here To use an IM follow these steps 1 Open the IM 2 Find out what the IM can do 3 Agree upon capabilities to use 4 Create input contexts with preferences and window s specified see Input Contexts ICs on page 352 5 Set the input context focus 6 Process events Although all applications go through the same setup when establishing input methods the results can vary widely In a Japanese locale you m
268. k object Several POSIX signal functions take a signal mask as an argument For example sigsuspend takes a new signal mask and swaps it for the current signal mask establishing which pending signals will be accepted while the process is suspended Using Synchronous Handling You can design your program so that it treats arriving signals as a stream of event records to be processed in sequence For example you could use one or more signal numbers in the POSIX real time range to signify events that are meaningful to your application Your application or one thread in your application can receive each signal in turn and act upon it Signals To implement this design approachk you would follow these steps 1 Block the expected signal numbers in all processes or threads using sigprocmask or pthread_sigmask 2 Send the signals using sigqueue This function permits you to augment the signal number with a union sigval in effect creating an open ended set of sub signals and also assures that multiple signals will be retained until you process them 3 Inthe signal processing loop wait for the next signal with sigwaitinfo or sigtimedwait When the signal arrives act accordingly and wait again The sigwaitinfo and sigtimedwait functions accept a new signal mask They unblock the specified signal or signals and suspend until one such signal arrives They accept that signal restore the original signal mask and return the
269. ken from the attribute object or whether these things should be inherited from the thread that creates the new thread When you set an attribute object for inheritance the scheduling policy and priority in the attribute object are ignored Thread Stack Allocation Each pthread has an execution stack area in memory By default pthread_create allocates stack space of the specified size from dynamic memory When it does so the stack space is automatically released when the thread is detached 213 Chapter 11 Thread Level Parallelism 214 You use pthread_attr_setstacksize to specify the size of this stack area You cannot specify a stack size less than a minimum You can learn the minimum by calling sysconf with _SC_THREAD_STACK MIN see the sysconf 3C reference page Preallocating Stack Areas You can instead preallocate stack space from any source of dynamic memory such as malloc When you preallocate stack space you must do the following e Specify the address of the space using pthread_attr_setstackaddr This tells pthread_create not to allocate space e Specify the size of the allocated space using pthread_attr_setstacksize This enables pthread_create to initialize the correct starting stack address e Free the stack space when the thread terminates see Joining and Detaching on page 218 There is normally no protection against a thread overrunning the space If a thread allocates too much automatic dat
270. ker no Fortran counterpart PVM routine is nonportable pom_scatter pumfscatter MPL Scatter MPI_SCATTER pom_send pomfsend MPIL_Send MPI_SEND pum_sendsig pumfsendsig PVM routine is nonportable pom_setopt pumfsetopt J pom_setrbuf pumfsetrbuf Communicators pum_setsbuf pomfsetsbuf Communicators pom_spawn pumfspawn pom_tasks pumftasks pvm_tidtohost pvmftidtohost j pvm_trecv pvmftrecv i pvm_upk pvmfunpack MPI_Unpack MPI_UNPACK Nonportable PVM Functions The PVM routines listed in this section cannot be translated directly into MPI routines These same routines are shown in Table 12 1 with the notation PVM routine is nonportable to distinguish them from the PVM routines that while they have no MPI counterpart are easily removed in the MPI environment If the PVM program in question uses any of the following PVM functions or uses dynamic groups it cannot be directly ported to an MPI program e pvm kill e pvm_notify e pvm_recvf e pvm_reg_hoster 243 Chapter 12 Distributed Process Parallelism e pvm_reg_rm e pvm_reg_tasker e pvm_sendsig You must change the PVM program to eliminate the use of these functions before it can be ported to an MPI program In some cases this may not be possible Note that most of these functions are available in the PVM domain only as C routines and are not commonly used Converting a PVM Program to an MPI Program 244 This section discusses the basic steps fo
271. l to find out when it becomes nonnegative To perform the V operation on a semaphore of either type call usvsema The uscpsema function provides a conditional P operation it performs a P operation on the semaphore only if it can do so without making the value negative The ustestsema function returns the current value of the semaphore which of course is immediately out of date The usinitsema function reinitializes the semaphore to a specified value Note that if you reinitialize a semaphore on which processes are waiting the processes continues to wait You should reinitialize a semaphore only in unusual circumstances 79 Chapter 4 Mutual Exclusion 80 You can call usctlsema to enable the keeping of either metering information cumulative counts of usage or a history trace The metering information shows whether a semaphore is a bottleneck in the program s operations The history trace can be used to analyze bugs Using Locks IRIX locks are implemented differently depending on the hardware architecture of the computer using them On a multiprocessor computer locks are busy wait locks so the processor continually tries to acquire the lock until it succeeds This implementation makes sense only on multiprocessor systems where one processor can release the lock while another processor is spinning trying to acquire the lock On a uniprocessor a process waiting to claim a lock is suspended until the lo
272. large as the maximum size allowed by that queue You can learn this size using mq_getattr see Example 6 4 for an example of this The mq_receive function blocks if the queue is empty unless O_NONBLOCK is in effect for the queue The message returned is always the oldest message in the highest priority class Using Asynchronous Notification Some applications are designed so that each process or thread does nothing but process messages In a design of this kind it makes sense for a process or thread to suspend itself when no messages are available on its queue Other applications are designed so that one process or thread performs multiple tasks besides handling messages or handles messages from multiple queues In this kind of program a process cannot suspend itself on a message queue Instead it needs to do other work and only request a message when a message is available One way to do this is to set the O_NONBLOCK flag and to periodically poll for a message by calling mq_receive and testing its return code However this is inefficient The POSIX message facility offers the ability to receive an asynchronous notification in the event that a message is posted to an empty queue and no process or thread is suspended waiting for that message You do this by calling mq_notify passing a queue and a sigevent_t structure The sigevent_t is declared in sys signal h which is included by mqueue h 133 Chapter 6 Message Queues
273. lation should be performed with strcoll and strxfrm These are table driven functions the tables are supplied as part of locale support The value of LC_COLLATE determines which ordering table to use See the strcoll 3 and strxfrm 3 reference pages strcoll has the same interface as stremp and can be directly substituted into code that uses stremp However strcoll can consume more CPU time so where it is used in a time critical loop you may have to redesign Specifying Numbers and Money Format of simple numbers differs from locale to locale Characters used for decimal radix and group separators vary Grouping rules may also vary Even though we assume that decimal numbers are universal there are some eighteen varying aspects of numeric formatting defined by a locale Many of these are details of monetary formatting 307 Chapter 14 Internationalizing Your Application 308 For example Germany uses a comma to denote a decimal radix and a period to denote a group separator English reverses these India groups digits by two except for the last three digits before the decimal radix Many locales have particular formats used for money some of which are shown in Table 14 3 Table 14 3 Some Monetary Formats Country Positive Format Negative Format India Rs1 02 34 567 89 Rs 1 02 34 567 89 Italy L 10 234 567 L 10 234 567 Japan 10 234 567 10 234 567 Netherlands F10 234 567 89 F 10 234 567 89 Norway Kr10 234
274. leconv 308 locale specific behavior 311 locales See locales message catalogs 324 MNLS fmtmsg 331 message catalogs See message catalogs MNLS pfmt 330 monetary formats 307 Motif 342 multibyte characters about converting 302 size of 302 string length 303 using 301 multilingual support 297 Index native language support 314 numerical formats 307 pfmt 330 printf 308 333 regular expressions 311 312 317 regular expressions examples 319 setlocal 294 setting locale 292 shift tables 316 signed chars 300 sorting rules 306 standards 289 strings 324 territories 295 time formats 309 Unicode 365 user input 343 application programming 343 text objects 343 toolkit text object 343 wide characters about 300 converting 305 XFontSetExtents 340 XPG 3 message catalogs See message catalogs regular expressions 311 X Window System about 335 changes 335 character sets 336 EUC encoding 338 fontsets 338 keyboard support 345 346 limitations 335 resource names 337 string resources 359 vertical text 336 XFontSetExtents 340 Xlib changes 336 Inter Process Communication See IPC interrupt validity fault 9 IPC arenas 39 barriers 82 BSD style 36 IRIX arenas 39 IRIX style 36 39 82 locks 80 parallel programming 39 portability 37 POSIX style 36 38 shared memory 43 65 attaching 61 controlling 61 detaching 61 IRIX 50 59 POSIX 45 50 shmat 6
275. lications do not need dynamic groups Once the PVM program to be ported deals only with static groups replace all instances of pym_joingroup with MPI_Comm_group or one of its variants Replace all occurrences of pym_lvgroup with MPI_Group_free 247 Chapter 12 Distributed Process Parallelism 248 Intertask Communication All PVM intertask communication calls have counterparts in MPI except for pvm_mcast and pym_trecv You can easily replace multicasting in the PVM library with multicasting at the application layer with a set of send calls or by defining a group and performing a broadcast in that group Similarly you can replace a timed receive in the PVM library by an equivalent function at the application layer Some PVM collective communication calls namely pym_gather and pym_reduce are nonblocking This characteristic should not lead to any changes in the application code unless the PVM application has explicit synchronization calls for example pvm_barrier after such nonblocking calls In such a case you can remove these synchronization calls from the translated MPI program To send contiguous data of a given type MPI does not require packing and unpacking of data in send buffers as PVM does Additionally for noncontiguous data MPI provides derived data types that avoid explicit packing and unpacking However MPI also provides pack unpack functions for sending noncontiguous data for compatibility wit
276. lly apart from the address space of any process When you create a message queue the queue has a public identifier The identifier is a file pathname for POSIX or an integer for SVR4 A process uses the identifier to open the queue When the queue is open the process can send messages to the queue or receive messages from the queue A message queue has an access mode similar to a file access mode specifying read and write access for its owner its owner s group or all users A process with an effective user ID lacking access cannot open the queue A process with an effective user ID giving only read access can only receive messages from the queue A message queue has a limit on the amount of data that can be queued POSIX limits the number of messages SVR4 limits the total size of queued messages When a process sends a message that would exceed the queue s limit the process can be notified immediately with an error code or it can be suspended until there is room When a process requests a message from a queue and no message is available the process can be notified immediately with an error code or it can be suspended until a message is sent Implementation Differences The abstract operations that a message queue supports are summarized in Table 6 1 with the names of the POSIX and SVR4 functions that implement them Table 6 1 Abstract Operations on a Message Queue Operation POSIX Function SVR4 Function Gain access to
277. lock Lek lck l_type F_WRLCK write exclusive lock lck l_whence 0 0 offset for l_start lck l_start OL lock starts at BOF lck l_len OL extent is entire file for try 0 try lt limit try if 0 fentl fd F_SETLK amp lck break mission accomplished if errno EAGAIN amp amp errno EACCES break mission impossible sginap 1 let lock holder run return errno The following points should be noted in Example 7 2 e Because fentl supports both read and write locks the type of the lock F_WRLCK is specified in the _type e The operation code F_SETLK is used to request that the function return if it cannot place the lock The code F_SETLKW would request that the function suspend until the lock can be placed e The starting location of the record is the sum of two fields _whence and I_start Both must be set to 0 in order to get the starting point to the beginning of the file Whole File Lock With lockf Example 7 3 shows a version of the lockWholeFile function that uses lockf Like fentl lockf treats a record length of 0 as meaning to end of file 163 Chapter 7 File and Record Locking 164 Example 7 3 Setting a Whole File Lock With lockf include lt unistd h gt for F_TLOCK include lt fcntl h gt for O_RDWR include lt errno h gt for EAGAIN define MAX_TRY 10
278. lock on a receive for a user specified amount of time MPI does not have a corresponding call e PVM includes a routine that allows users to define their own receive contexts to be used by subsequent PVM receive routines Communicators in MPI provide this type of functionality to a limited extent On the other hand MPI provides several features that are not available in PVM including a variety of communication modes communicators derived data types additional group management facilities and virtual process topologies as well as a larger set of collective communication calls However the set of MPI functions that are not available in PVM is not discussed here since they are not directly relevant to porting from PVM to MPI Comparing Library Routines 240 Some PVM routines have close counterparts in MPI and others do not Comparable Routines Table 12 1 lists all the PVM routines showing both C and Fortran names and the corresponding MPI routines As can be seen most PVM routines have direct MPI counterparts Of the remaining routines many can simply be removed owing to changes in initial environment setup between PVM and MPI These are marked by an asterisk in the MPI column and also include utility routines and routines that can be easily implemented at the application level for example pym_mcast and pyvm_trecv Comparing Library Routines Routines that have a conceptual counterpart in MPI but are not directly t
279. ly reflected on disk Use msync to force modified pages of a segment to be written to disk see Synchronizing the Backing Store on page 30 If IRIX needs to read a page of a mapped NFS mounted file and an NFS error occurs for example because the file server has gone down the error is reflected to your program as a SIGBUS exception Caution When two or more processes in the same system map an NFS mounted file their image of the file will be consistent But when two or more processes in different systems map the same NFS mounted file there is no way to coordinate their updates and the file can be corrupted File Integrity Any change to a file is immediately visible in the mapped segment This is always true when flags contains MAP_SHARED and initially true when flags contains MAP_PRIVATE A change to the file can be made by another process that has mapped the same file 17 Chapter 1 Process Address Space 18 A mapped file can also be changed by a process that opens the file for output and then applies either write to update the file or ftruncate to shorten it see the write 2 and ftruncate 3 reference pages In particular if any process truncates a mapped file an attempt to access a mapped memory page that corresponds to a now deleted portion of the file causes a bus error signal SIGBUS to be sent When MAP_ PRIVATE is specified a private copy of a page of memory is created whenever the process stores
280. m h gt for shmget etc include lt errno h gt errno and perror include lt stdio h gt int main int argc char argv key_t key key int semid 1 object ID int perms popt 0 perms to set if given int uid uopt 0 uid to set if given int gid gopt 0 gid to set if given int val vopt 0 setall value if given struct semid_ds ds int c while 1 c getopt argc argv k i p u g switch c case k key key key_t strtoul optarg NULL 0 break case i semid semid int strtoul optarg NULL 0 break case p permissions perms int strtoul optarg NULL 0 popt 1 break case u uid System V Facilities for Mutual Exclusion uid int strtoul optarg NULL 0 uopt 1 break case g gid gid int strtoul optarg NULL 0 gopt 1 break default unknown or missing argument return 1 if 1 semid i not given must have k semid semget key 0 0 if 1 semid if 0 semctl semid 0 IPC_STAT amp ds if popt uopt gopt if popt ds sem_perm mode perms if uopt ds sem_perm uid uid if gopt ds sem_perm gid gid if 0 semctl semid 0 IPC_SET amp ds semctl semid 0 IPC_STAT amp ds refresh info else perror semct1 IPC_SET printf owner uid gid
281. mbia GM Territories Germany DE Ghana GH Gibraltar GI Greece GR Greenland GL Grenada GD Guadalupe GP Guam GU Guatemala GT Guinea GN Guinea Bissau GW Guyana GY Haiti HT Heard and HM Honduras HN McDonald Islands Hong Kong HK Hungary HU Iceland IS India IN Indonesia ID Iran IR Iraq IQ Ireland IE Israel IL Italy IT Jamaica JM Japan JP Jordan JO Kampuchea KH Kenya KE Kiribati KI Korea KPor Kuwait KW KR Table A 1 continued ISO 3166 Country Codes Country Name Code Country Name Code Country Name Code Laos LA Lebanon LB Lesotho LS Liberia LR Libya LY Liechtenstein LI Luxembourg LU Macau MO Madagascar MG Malawi MW Malaysia MY Maldives MV Mali ML Malta MT Marshall Islands MH Martinique MQ Mauritania MR Mauritius MU Mexico MX Micronesia FM Monaco MC Mongolia MN Montserrat MS Morocco MA Mozambique MZ Namibia NA Nauru NR Nepal NP Netherlands NL Netherlands AN Antilles Neutral Zone NT New Caledonia NC New Zealand NZ Nicaragua NI Niger NE Nigeria NG Niue NU Norfolk Island NF Northern MP Mariana Islands Norway NO Oman OM Pakistan PK Palau PW Panama PA Pangaea GE Papua New PG Paraguay PY Peru PE Guinea Philippines PH Pitcairn PN Poland PL Portugal PT Puerto Rico PR Qatar QA Quebec QC Reunion RE Romania RO Rwanda RW Saint Kitts and KN Saint Lucia LC Nevis Saint Vincentand VC Samoa WS San Marino SM the Grenadines 369 ISO 3166 Country Names and Abbreviations 370 Table A 1 contin
282. ment Address on page 21 The MAP_AUTOGROW element of flags specifies what should happen when a process stores data past the current end of the segment provided storing is allowed by prot When flags contains MAP_AUTOGROW the segment is extended with zero filled space 13 Chapter 1 Process Address Space 14 Otherwise the initial len value is a permanent limit and an attempt to store more than len bytes from the base address causes a SIGSEGV signal Two elements of flags specify the rules for sharing the segment between two address spaces when the segment is writable e MAP_SHARED specifies that changes made to the common pages are visible to other processes sharing the segment This is the normal setting when a memory arena is shared among multiple processes When a mapped segment is writable any changes to the segment in memory are also written to the file that is mapped The mapped file is the backing store for the segment When MAP_AUTOGROW is specified also a store beyond the end of the segment lengthens the segment and also the file to which it is mapped e MAP_PRIVATE specifies that changes to shared pages are private to the process that makes the changes The pages of a private segment are shared on a copy on write basis there is only one copy as long as they are unmodified When the process that specifies MAP_PRIVATE stores into the segment that page is copied The process has a private copy of the modified
283. ments are IRIX features that are not portable to POSIX or to System V Mapping a File for I O You can use mmap as a simple low overhead way of reading and writing a disk file Open the file using open but instead of passing the file descriptor to read or write use it to map the file Access the file contents as a memory array The memory accesses are translated into direct calls to the device driver as follows e Anattempt to access a mapped page when the page is not resident in memory is translated into a call on the read entry point of the device driver to read that page of data e When the kernel needs to reclaim a page of physical memory occupied by a page of a mapped file and the page has been modified the kernel calls the write entry point of the device driver to write the page It also writes any modified pages when the file mapping is changed by munmap or another mmap call when the program applies msync to the segment or when the program ends When mapping a file for input only when the prot argument of mmap does not contain PROT_WRITE you can use either MAP_SHARED or MAP_PRIVATE When writing is allowed you must use MAP_SHARED or changes will not be reflected in the file Memory mapping provides an excellent way to read a file containing precalculated constant data used by an interactive program Time consuming calculation of the data elements can be done offline by another program the other program als
284. mer by calling timer_settime The principal argument to this function is an itimerspec_t object which contains two times One it_value specifies when the timer next expires The other it_interval is the value to be loaded into the timer when it expires You can call timer_settime to accomplish any of three different operations e With it_value nonzero and it_interval zero arm the timer and initiate a one time interval e With it_value nonzero and it_interval nonzero arm and initiate a repeating timer e With it_value zero disarm the timer preventing it from expiring if it has not expired already You can also use timer_settime to reprogram the intervals in a timer while it runs A timer can be programmed in terms of relative time you pass an it_value that represents increments past the present time or absolute time you pass an it_value that represents actual future times when the timer should expire You can interrogate the time remaining in a timer by calling timer_gettime After a timer has expired for example in the signal handling function you can call timer_getoverrun to find out how many additional intervals it would have signalled but could not signal because the first signal was pending Timer Facilities BSD Timers IRIX supports the BSD UNIX feature of interval timers or itimers Table 5 10 summarizes the functions you use to manage itimers Table 5 10 BSD Functions for Interval Timers
285. messages on the queue default MQ_DEF_MAXMSG f lt flags gt flags to use with mq_open including use O_ CREAT x use O_EXCL lt path gt the pathname of the queue required Numeric arguments can be given in any form supported by strtoul 3 KA 136 POSIX Message Queues include lt mqueue h gt define MQ_DEF_MSGS define MQ_ D include lt unistd h gt include lt errno h gt include lt fcntl h gt include lt stdio h gt int main int argc message queue stuff E 1024 IZI T EF_MAXMSG 16 for getopt errno and perror O_flags char argv int perms 0600 permissions int oflags O_RDWR flags O_CREAT O_EXCL int rd 0 wr 0 r and w options mqd_t mqd returned msg queue descriptor Int char path struct mq_attr b buf mq_msgsize buf mq_maxmsg gt first non option argument buffer for stat info EF_MSGSIZE F_MAXMSG uf MQ MQ_DI D while 1 c switch case c i ipia perms brea case b i buf mq_msg break case m buf mq_max brea case c oflags brea case x oflags break default u return 1 switch while optind lt arg path else Ki tT Ky Ne of Ky Ve Lf printf Queue pathname required n argv optind getopt argc argv p
286. minimum priority in a pthread_mutexattr_t A mutex must be initialized before use You can do this in one of three ways e Static assignment of the constant PTHREAD_MUTEX_INITIALIZER e Calling pthread_mutex_init passing NULL instead of the address of a mutex attribute object e Calling pthread_mutex_init passing a pthread_mutexattr_t object that you have set up with attribute values The first two methods initialize the mutex to default attributes Dynamic initialization should be done only once see Initializing Static Data on page 216 227 Chapter 11 Thread Level Parallelism 228 Two attributes can be set in a pthread_mutexattr_t The priority inheritance protocol is the more important You can set the priority inheritance protocol using pthread_mutexattr_setprotocol to one of three values PTHREAD_PRIO_NONE The mutex has no effect on the thread that acquires it PTHREAD_PRIO_PROTECT The thread holding the mutex runs at a priority at least as high as the highest priority of any mutex that it currently holds PTHREAD_PRIO_INHERIT The thread holding the mutex runs at a priority at least as high as the highest priority of any thread blocked on that mutex When a low priority thread has acquired a mutex and a thread with higher priority claims the mutex and is blocked a priority inversion takes place a higher priority thread is forced to wait for one of lower priority The PTHREAD_PRIO_INHERIT
287. misses in non looping code e Use memalign to allocate important structures on 128 byte boundaries so as to ensure the structures fit in the smallest number of cache lines see the memalign 3 reference page Cache Mapping in Challenge and Onyx Systems The cache design in the Challenge and Onyx line depends on the CPU model in use The basic Challenge system uses the IP19 board which uses a direct mapped cache the address of a byte of data is taken modulo the cache size to generate the cache address This means that two words that are separated in main memory by an exact multiple of the cache size are always loaded to the same cache location Note The cache in later models such as the POWER Challenge system do not use simple modulus mapping these machines use 2 way or 4 way associative caches that are much more resistant to cache conflicts Only one of the words can occupy the cache at a time so if your program alternates between words it will have a cache miss on each reference It is surprisingly easy to create this situation The following code fragment causes bad performance in an R4x00 Challenge system with a 1 MB cache float part1 262144 1 MB float part2 262144 adjacent 1 MB for j 0 3 lt 262144 3 part1l j part2 j In that code fragment the words of each array hash to the identical cache lines so each assignment in the loop incurs two cache misses Some systems have caches of different sizes but
288. mit is established in the kernel tuning parameters For a quick look at the kernel limits use fgrep rlimit var sysgen mtune kernel Defining the Address Space To examine and change the limits use systune see the systune 1 reference page Example 1 1 Using systune to Check Address Space Limits systune i Updates will be made to running system and unix install systune gt rlimit_vmem_max rlimit_vmem_max 536870912 0x20000000 11 systune gt resource group resource statically changeable rlimit_vmem_max 536870912 0x20000000 11 rlimit_vmem_cur 536870912 0x20000000 11 rlimit_stack_max 536870912 0x20000000 11 rlimit_stack_cur 67108864 0x4000000 11 Tip These limits interact in the following way each time your program creates a process with sproc and does not supply a stack area see the sproc 2 reference page an address segment equal to rlimit_stack_max is dedicated to the stack of the new process When rlimit_stack_max is set high a program that creates many processes can quickly run into the rlimit_umem_max boundary Delayed and Immediate Space Definition IRIX supports two radically different ways of defining segments of address space The conventional behavior of UNIX systems and the default behavior of current releases of IRIX is that space created using brk or malloc is immediately defined Page table entries are created to define the addresses and swap space is allocated as a backing sto
289. mple the above cases could be more strictly defined by setting LANG to en_EN or en_US Full rigor might lead to en_EN 88591 for England the locale encoding specification for ISO 8859 1 is 88591 and en_US ascii for the USA ANSI C has defined a special locale value of C The C locale is guaranteed to work on all compliant systems and provides the user with the system s default locale This default is typically American English and ASCII but need not be POSIX has also defined a special locale value POSIX which is identical to the C locale The length of the locale string may not exceed NL_LLANGMAxX characters NL_LANGMAx is defined in usr include limits h However XPG 4 recommends that this string not counting modifiers not exceed 14 characters Locales Limitations of the Locale System This section explains multilingual support misuse of locales and the absence of filesystem information for encoding types Multilingual Support There can be only one locale at a time associated with any given process in an internationalized system Therefore although multilingual applications which give the appearance of using more than one locale at a time can be created internationalization does not provide inherent support for them Here are two examples of multilingual programs e An application creates and maintains windows on four different displays operated by four different users The program has a single controlling pro
290. mple 5 1 demonstrates the use of clock_gettime and clock_getres The following is an example of the output of this program ptime as executed on an Indy workstation ptime CLOCK_REALTIME value sec 835660711 ns 465330000 8 3566le 08 sec CLOCK_REALTIME units sec 0 ns 10000000 0 01 sec CLOCK_SGI_CYCLE value sec 83 ns 449744360 83 4497 sec CLOCK_SGI_CYCLE units sec 0 ns 40 4e 08 sec CLOCK_SGI_FAST units sec 0 ns 1000000 0 001 sec Example 5 1 Example of POSIX Time Functions Program to exercise POSIX clock_gettime and clock_getres functions ptime r c R C r display CLOCK_REALTIME value R display CLOCK_REALTIME resolution G c display CLOCK_SGI_CYCLE value C display CLOCK_SGI_CYCLE resolution F display CLOCK_SGI_FAST resolution cannot get time from this Default is display everything rRcC x include lt time h gt include lt unistd h gt for getopt include lt errno h gt errno and perror include lt stdio h gt void showtime const timespec_t tm const char caption 121 Chapter 5 Signalling Events printf Ss sec ld ns ld g sec n caption tm tv_sec tm tv_nsec double tm tv_sec double tm tv_nsec 1e9 main int argc char argv int opta 1 int optr 0 int optR 0 int optc 0 0 0 int optC int optF 0 timespec_t sampl
291. mum number of CPUs that are available to the calling process and its children This reflects both the system hardware and reservations made on CPUs but does not reflect system load PR_GETNSHARE Query the number of processes in the share group with the calling process PR_GETSTACKSIZE Query the maximum size of the stack segment of the calling process For the parent process this reflects the system limit also available from getrlimit RLIMIT_STACK see getrlimit 2 For a process started by sprocsp the size of the allocated stack 197 Chapter 10 Process Level Parallelism 198 PR_SETSTACKSIZE Setan upper limit on stack growth for the calling process and for child processes it creates in the future PR_RESIDENT Prevent the calling process from being swapped out This has no connection to paging but to swapping out an entire inactive process under heavy system load The sysmp function gives a privileged process information about and control over the use of a multiprocessor Some of the operations it provides are as follows MP_NPROCS Number of CPUs physically in the system MP_NAPROCS Number of CPUs available to the scheduler should be the same as prctl PR_MAXPPROCS MP_MUSTRUN Assign the calling process to run on a specific CPU MP_MUSTRUN_PID Assign a specified other process typically a just created child process to run on a specific CPU MP_GETMUSTRUN Query the must run assignment of the calling process or MP_
292. n NLS interface defines the functional capabilities of a generic database that holds various language dependent entities This section describes those entities e Configuration Data e Collating Sequence Tables e Character Classification Tables e Shift Tables e Language Information Configuration Data Configuration data identify the languages supported on a system in terms of the recognized settings of language territory and codeset Each valid combination of these settings has its own set of collating sequence character classification and shift tables language information data and message catalogs Locale Specific Behavior Collating Sequence Tables Collating sequence tables define the collating sequence for each supported language The binary values of characters in the associated coded character set are used as indices into the table individual entries of which indicate the relative position of that character in the language collating sequence The interface definition supports the following capabilities e one to one character mappings e one to two character mappings where certain characters require treatment as if they were two characters e n to one character mappings where certain character sequences require treatment as if they represented a single character in the collating sequence The maximum value of N is defined separately for each supported language where N is a number in the ra
293. n a share group of processes is created using sproc and the sproc flag PR_SFDS is used to keep the open file table synchronized for all processes see the sproc 2 reference page then there is a single file pointer for each file and it is shared by every process in the share group This feature has important implications when using record locking The current value of the file pointer is used as the reference for the offset of the beginning of the lock in lockf at all times and in fentl when using an _whence value of 1 Since there is no way to perform the sequence Iseek fentl as an atomic operation there is an obvious potential for race conditions a lock might be set using a file pointer that was just changed by another process 171 Chapter 7 File and Record Locking The solution is to have the child process close and reopen the file This creates a distinct file descriptor for the use of that process Another solution is to always use the fentl function for locking with an _whence value of 0 or 2 This makes the locking function independent of the file pointer processes might still contend for the use of the file pointer for other purposes such as direct access input Deadlock Handling A certain level of deadlock detection and avoidance is built into the record locking facility This deadlock handling provides the same level of protection granted by the usr group standard lockf call This deadlock detection is
294. n any process that is attached to the shared arena If the address is passed to a process that has not attached the arena the address is not valid for that process and its use will cause a SIGSEGV The usmalloc family of functions is based on the arena allocation function family described in the amalloc 3 reference page The usmallopt function is the same as the amallopt function and both provide several options for modifying the memory allocation methods in a particular arena In a similar way usmallinfo is the same as amallinfo and both return detailed statistics on usage of memory allocation in one arena Exchanging the First Datum The processes using a shared arena typically need to locate some fundamental data structure that has been allocated within the arena For example the parent process creates a foundation data structure in the arena and initializes it with pointers to other objects within the arena Any process starting to use the arena needs the address of the foundation structure in order to find all the other objects used by the application The shared arena has a special one pointer field for storing such a basic address This area is accessed using the functions summarized in Table 3 5 Table 3 5 IRIX Shared Memory First Datum Functions Function Name Purpose and Operation usputinfo 3 Set the shared pointer field of an arena to a value usgetinfo 3 Retrieve the value of the shared pointer field of an arena
295. n be practically encoded in 16 bits Daily use Chinese can be also but archives and scholars frequently need more so Chinese is often encoded with up to four bytes per character 363 Chapter 14 Internationalizing Your Application 364 Some Standards Various Asian character sets have been developed some of which are considered standard Encodings for these sets are less standardized Asian character sets usually require larger than byte character types like those described in Multibyte Characters Table 14 11 lists some of these standard character sets Note that some of these character sets have multiple associated codesets usually designated by appending the year the codeset was adopted to the character set name For example JIS X 208 1983 is different from JIS X 208 1990 Table 14 11 Character Sets for Asian Languages Language Character Set Standards Support Japanese JIS X 0201 1976 0 Katakana JIS X 0208 1983 0 Kanji kana Latin Greek Cyrillic symbols others JIS X 0212 1990 0 Supplemental kanji others Chinese GB 2312 1980 0 Korean KSC 5601 1987 0 Hangul Taiwan CNS 11643 EUC EUC is Extended UNIX Code an encoding methodology that supports concurrent use of four codesets in one encoding It employs two special shift state bytes ssl 0x8e ss2 0x8f These are used to identify codesets within a string The EUC encoding scheme uses the following patterns to indicate which codeset is
296. n page 92 can be used to experiment with semget creating semaphore sets with different sizes and permissions e Example 4 4 on page 94 can be used to test semctl for displaying and changing owner IDs and permissions e Example 4 5 on page 96 can be used to test semctl for sampling the values of semaphores or to display the state of a semaphore set e Example 4 6 on page 98 can be used to test semop for single or multiple operations Example Uses of semget The program in Example 4 3 semget invokes semget with arguments you specify on the command line k key Numeric key to identify the semaphore set required for example k 99 Default is IPC_PRIVATE p perms Access permissions to apply to a created set for example p 0664 Default is octal 0666 s setsize Number of semaphores in a created set for example s 8 The limit is 25 but feel free to experiment with larger numbers to see the return code 91 Chapter 4 Mutual Exclusion 92 c Use IPC_CREAT No set is created unless this is specified x Use IPC_EXCL Use with c to require that a set not exist Example 4 3 Program to Demonstrate semget semget program to test semget 2 semget k lt key gt k lt key gt p lt perms gt s lt setsize gt ve include lt stdio h gt for creating semaphores c x p lt perms gt s lt setsize gt the key to use default 0 IPC_PRIVATI E
297. nationalization 291 Locales 292 Setting the Current Locale 292 Category 293 Locale 294 The Empty String 294 Nonempty Strings in Calls to setlocale 295 Location of Locale Specific Data 295 Locale Naming Conventions 295 Limitations of the Locale System 297 Multilingual Support 297 Misuse of Locales 297 No Filesystem Information for Encoding Types 298 Character Sets Codesets and Encodings 298 Eight Bit Cleanliness 299 Character Representation 300 Multibyte Characters 301 Use of Multibyte Strings 302 Handling Multibyte Characters 302 Conversion to Constant Size Characters 302 How Many Bytes ina Character 302 How Many Bytes in an MB String 303 How Many Characters in an MB String 303 Wide Characters 304 Uses for wchar Strings 304 Support Routines for Wide Characters 305 Conversion to MB Characters 305 Reading Input Data 305 Cultural Items 305 xvi Contents Collating Strings 306 The Issue 306 The Solution 307 Specifying Numbers and Money 307 Using printf 308 Using localeconv 308 Using strfmon 309 Formatting Dates and Times 309 Character Classification and ctype 309 The Issue 310 The Solution 310 Regular Expressions 311 Locale Specific Behavior 311 Overview of Locale Specific Behavior 312 Local Customs 312 Regular Expressions 312 The ANSI X3 159 198X Standard for C 312 Native Language Support and the NLS Database 314 Configuration Data 314 Collating Sequence Tables 315 Character Classification Tables 315 Shift T
298. ncapsulated libraries that exchange data independently of the data exchanged by the client modules MPI also provides several elegant data exchange functions for use by a program that is emulating an SPMD parallel architecture PVM is possibly more suitable for distributing a program across a heterogenous network that includes both uniprocessors and multiprocessors and includes computers from multiple vendors When the application runs in the environment of a Silicon Graphics Array system MPI is the recommended interface Porting From PVM to MPI Because MPI and PVM address similar problems in ways that are conceptually similar you can consider porting a program from PVM to MPI in order to get better performance onan Array system A detailed discussion of this process with examples appears under Converting a PVM Program to an MPI Program on page 244 PVM and MPI are two popular message passing libraries that are in use across a variety of platform MPI assimilates the most attractive features of a number of existing message passing systems including PVM see Choosing Between MPI and PVM on page 236 Silicon Graphics has adopted MPI as the message passing model for the POWER CHALLENGEarray system and other Array products and provides a low latency high bandwidth implementation of MPI for these systems Programmers are encouraged to write new message passing applications using MPI and to port existing applications to MPI when
299. nd a message to a queue call msgsnd and specify the queue the address and length of the message data and a flag number that can contain IPC_NOWAIT The message buffer contains an integer specifying the type of the message Messages on the queue are retained in arrival sequence within types The message is copied out of the caller s buffer so the buffer can be reused immediately after a successful send If the queue is full the msgsnd function blocks unless the IPC_NOWAIT flag is passed Receiving a Message To receive a message call msgrcv and specify the queue the address and size of a buffer a number for the desired message type and a flag value If the queue is empty the msgrcv function blocks unless the IPC_NOWAIT flag is passed If the message buffer is not as large as the message an error is returned unless the IPC_NOERROR flag is passed Then the message is simply truncated to fit the buffer The type value can be 0 to specify any type or it can be a specific positive type number to select the first number of that type Finally it can be a negative value to specify any type less than or equal 145 Chapter 6 Message Queues 146 Example Programs The following programs demonstrate the use of SVR4 message queues e Example 6 5 on page 148 demonstrates the use of msgget to create or access a queue e Example 6 6 on page 150 demonstrates the use of msgctl to query or modify a qu
300. ne font file match the PostScript font name specified in the FontName entry in the header of that outline font file For example if you enter grep FontName Courier Bold in the directory usr lib DPS outline base you get FontName Courier Bold def The name revealed is used for the filename of the outline font the filename of the metric file and in the usr lib X11 fonts ps2xlfd map file For example Adobe provided the Utopia Regular outline font file UTRG____ pfa which is an outline font file in the Type 1 format To find the PostScript font name for this font enter grep FontName UTRG_ pfa You should get the response FontName Utopia Regular def When this font was added to IRIX the name of the file UTRG to Utopia Regular _ pfa was changed 4 Put the file Utopia Regular in the directory usr lib DPS outline base because that outline font is in the Type 1 format If you have an outline font in the Speedo format put it in the directory usr lib X11 fonts Speedo 5 To add the Utopia Regular font and font metric files to Display PostScript enter usr bin X11 makepsres o usr lib DPS DPSFonts upr usr lib DPS outline base usr lib DPS AFM You should now be able to access the font file you added via Display PostScript 6 For most font families shipped by Silicon Graphics there is one entry per font family in the file usr lib X11 fonts ps2xlfd_map as described in Adding a Bitmap Font The same en
301. ne is a separate resource that is guarded by a lock The procedure for obtaining a buffer from the pool is as follows 1 Perform P on the pool semaphore When the operation completes you are assured there is at least one buffer in the pool and you are also assured that the count representing the buffer you need has been decremented from the semaphore 2 Claim the lock that guards the buffer queue anchor This ensures that there will be no conflict with another process taking or returning a buffer at the same time 3 Remove one buffer from the queue updating the queue anchor Step 1 assures that the queue is not empty 4 Release the lock on the queue anchor Overview of Mutual Exclusion The procedure for returning a buffer to the pool is as follows 1 Claim the lock that guards the buffer queue anchor This ensures that there will be no conflict with another process taking or returning a buffer at the same time 2 Put the returned buffer back on the queue updating the queue anchor The queue could be empty at this time 3 Release the lock on the queue anchor 4 Perform V on the pool semaphore This announces that at least one additional buffer is now free and may unblock some process waiting for a buffer The same two basic procedures work to allocate any collection of objects For example the semaphore could represent the number of open slots in a ring buffer and the lock could stand for the right to update the rin
302. ng a Type 1 Font to a PostScript Printer explains how to download a Type 1 font to a PostScript printer 261 Chapter 13 Working With Fonts Font Basics 262 Fonts are collections of characters A font contains the information about the shape size and position of each character in a character set That information is needed by programs that process characters such as editing word processing desktop publishing multimedia titling and prepress application programs Almost all software components in a computer system use fonts to display messages prompts titles and so forth Binary digits are used to represent all types of information stored in a digital computer including fonts Digital typography deals with the style arrangement and appearance of typeset matter in digital systems If you want to use font and font metric files to correctly typeset text on a digital computer you need to know some basics about digital typography This section contains a brief introduction to fonts and digital typography You may want to read a book on typography for more in depth information This section covers the following topics e Terminology introduces a few basic terms e How Resolution Affects Font Size describes horizontal and vertical resolution pixels and bitmap fonts e Font Names explains the differences between PostScript and X Windows font names e Writing Programs That Need to Use Fonts covers
303. ng and Debugging a Pthread Application 209 Compiling Pthread Source 209 Debugging Pthread Programs 210 Debugging With dbx 211 Debugging With the Workshop Debugger 211 Creating Pthreads 212 Initial Detach State 213 Initial Scheduling Priority and Policy 213 Thread Stack Allocation 213 Preallocating Stack Areas 214 Caveats Regarding Stack Space 215 Executing and Terminating Pthreads 215 Getting the Thread ID 216 Initializing Static Data 216 Setting Event Handlers 217 Terminating and Being Terminated 217 Joining and Detaching 218 Using Thread Unique Data 219 Pthreads and Signals 221 Setting Signal Masks 222 Setting Signal Actions 222 Receiving Signals Synchronously 223 Scheduling Pthreads 223 Scheduling Policy 224 Scheduling Priority 224 Synchronizing Pthreads 226 xiii Contents Mutexes 226 Preparing Mutex Objects 226 Using Mutexes 229 Condition Variables 229 Preparing Condition Variables 230 Using Condition Variables 230 12 Distributed Process Parallelism 235 Choosing Between MPI and PVM 236 Porting From PVM to MPI 237 Differences Between PVM and MPI 238 Comparing Library Routines 240 Comparable Routines 240 Nonportable PVM Functions 243 Converting a PVM Program to an MPI Program 244 Initial Environment Setup 244 Pure SPMD Program 245 General SPMD Model 245 MPMD Model 246 Common Environment Setup Changes 246 Task Environment Cleanup 247 Group Management Functions 247 Intertask Communication 248 Utility Functions 248
304. ng constructs such as TextProperty contain information regarding their own encoding Xlib Interface Change Full use of X11R6 s internationalization features means calling some new routines supplied in the X11R6 Xlib While all old Xlib applications work with the new Xlib developers should change their code in places These are described below Internationalization Support in X11R6 Resource Names Resource names are compiled into programs Because of that their encoding must be known independent of locale Trying to add a level of indirection here results in a problem you re always left with something compiled that can t be localized Resource names therefore use the X Portable Character Set The names may be anything at least they ll mean something to the application author If the names were numbers for example they would be meaningless to everybody Getting X Internationalization Started Xlib s internationalization state like that of libc needs to be initialized Initialization for Toolkit Programming If you re using Xt with a widget set such as IRIS IM Motif or XaW then don t use setlocale Instead use XtSetLanguageProc NULL NULL NULL If you re using a toolkit other than Xt call setlocale as early as possible after execution begins Initialization for Xlib Programming Initialize Xlib s internationalization state after calling setlocale Xlib is being initialized not a server or
305. nge 1 NL_NMAX e don t care characters where certain characters are ignored by the collating sequence These capabilities extend to providing support for the relative ordering of collating elements within an equivalent class for example where two characters are first compared for equality ignoring accents and if equal are then ordered by accent sequence Character Classification Tables These contain the lookup tables for character classification Each character code from the defined coded character set is used as an index into the relevant language lookup table Each entry language lookup table contains a series of flags identifying the truth or falsehood of a particular language assertion such as e upper case alphabetic character e lower case alphabetic character e punctuation character e control character e space character 315 Chapter 14 Internationalizing Your Application 316 Shift Tables Shift tables contain the corresponding upper and lower case combinations for each character defined in a coded character set Thus the upshifted or downshifted value of a character can be determined by accessing the relevant character entry in the shift table Language Information Language information or langinfo contains message text specific to a particular localization The library function nl_langinfo provides a procedural interface to this data allowing applications to discover cultural and language specific
306. nge c c where c can identify a collating symbol or an equivalence class If the hyphen character appears immediately after an opening square bracket or immediately prior to a closing square bracket it has no special meaning Within square brackets a period that is not part of a c sequence a colon that is not part of a class sequence and an equals sign that is not part of a c sequence matches itself Table 14 8 shows examples of simple regular expressions Table 14 8 Examples of Internationalized Regular Expressions Pattern Definition a bcd any form of a followed by bcd ch e any element that collates between ch and e lower any lower case letter 319 Chapter 14 Internationalizing Your Application 320 Cultural Data The items of cultural data listed in Table 14 9 are defined in the C locale Table 14 9 Cultural Data Names Categories and Settings Item Category Setting for the C Locale D_T_FMT LC_TIME a Yob Yod H M S Y D_FMT LC_TIME Yom d oy T_FMT LC_TIME H M S AM_STR LC_TIME AM PM_STR LC_TIME PM DAY_1 LC_TIME Sunday DAY_2 LC_TIME Monday DAY_3 LC_TIME Tuesday DAY_4 LC_TIME Wednesday DAY_5 LC_TIME Thursday DAY_6 LC_TIME Friday DAY_7 LC_TIME Saturday ABDAY_1 LC_TIME Sun ABDAY_2 LC_TIME Mon ABDAY_3 LC_TIME Tue ABDAY_4 LC_TIME Wed ABDAY_5 LC_TIME Thu ABDAY_6 LC_TIME Fri ABDAY_7 LC_TIME Sat MON_1 L
307. ns IRIX Facilities for Mutual Exclusion Using Test and Set All test and set functions solve a similar problem how to update the contents of a memory word reliably from two or more CPUs concurrently Use a test and set function to avoid the traditional race condition For example suppose that two or more processes could execute code to increment a variable as in shared e Process A loads shared into a register and adds 1 to it e Process B loads shared into a register and adds 1 to it e Process A stores the value in memory e Process B stores the value in memory The result is to increment shared by 1 when it should be incremented by 2 However if both processes use test_then_add amp shared 1 instead they are assured that both increments will occur regardless of timing Using Compare and Swap The test and set functions are not adequate to do race free pointer manipulation you need a compare and swap function for that The C library includes the uscas and uscas32 functions for this purpose Use uscas to work with pointer sized values which can be either 32 or 64 bits depending on compile options Use uscas32 to work with words that should always be 32 bits in every program The compare and swap functions take four arguments destp Address of the target memory field you want to update old Expected current value of the memory field new Desired new value based on the expected old value u Address of
308. nt Metric Files 4 Move the bitmap font files to the appropriate directory usr lib X11 fonts 100dpi or usr lib X11 fonts 75dpi You can of course combine this step with the format conversion step as follows bdftopcf UTRG_10 bdf compress c gt usr lib X11 fonts 100dpi utopR10 pcf Z You can tell the resolution for which a font was designed by the name of the directory in which the font designer stored the font files or by the information in the header of a bitmap font file In a BDF 2 1 font file the horizontal and vertical resolution are specified in the X font name They are also specified after the point size as the second and third numeric values in a SIZE entry For example the entry SIZE 8 100 100 within the file indicates an 8 point font that was designed for the horizontal and vertical resolution of 100 dpi 5 For Type 1 PostScript font families there is one entry per font family in the file usr lib X11 fonts ps2xlfd_map For each Japanese font family shipped by Silicon Graphics there is an entry in the file usr lib X11 fonts ps2xlfd_map japanese When adding a new Type 1 font insert an entry in the appropriate file for each style variation in the font family It is not necessary to have an entry for each bitmap size For example the entries in ps2xlfd_map for the Utopia fonts are Utopia Bold adobe utopia bold r normal 0 0 0 0 p 0 is08859 1 Utopia BoldItalic adobe utopia bold i normal 0 0
309. ntations of these IPC features can be summarized as follows POSIX compliant library calls are provided for signal handling shared memory semaphores mutexes condition variables and message queues The implementation is highly tuned and has low system overhead POSIX facilities are usable from POSIX threads see Chapter 11 Thread Level Parallelism IRIX unique library calls are provided for shared memory semaphores locks and barriers The implementation has slightly more overhead than POSIX operations but often takes better advantage of concurrent hardware in multiprocessors and has a number of special features such as the ability to apply poll to semaphores System function calls compatible with AT amp T System V Release 4 are provided for signal handling shared memory semaphores message queues and file locking The implementation is provided for ease of porting software but is not particularly efficient Library functions compatible with BSD UNIX are provided for signal handling file locking and socket support Select your IPC mechanisms based on these guidelines Never mix the implementations of a given mechanism in a single program For example if a single program mixes POSIX and System V signal handling functions or mixes both BSD and System V file locking calls unpredictable results can follow The POSIX libraries are the newest implementations and in many cases they are the most efficient A program bas
310. ntil initializing is done ussetlock stuff gt updateLock here do anything needing exclusive use of arena t stuff gt joinedProcs another process has joined usunsetlock stuff gt updateLock release arena ret 1 end the loop else This process appears to be first to call usinit Allocate an arenaStuff structure with its updateLock already held and 1 process joined and try to swap it into place as the active one W xpect no errors in setting up arenaStuff If one occurs the arena is simply unusable and we return a NULL to the caller L hx stuff usmalloc sizeof arenaStuff_t arena return stuff should never occur if stuff gt updateLock usnewlock arena return usptr_t 0 should never occur if uscsetlock stuff gt updateLock 1 return usptr_t 0 should never occur stuff gt joinedProcs 1 if ret uscasinfo arena 0 stuff a Our arenaStuff is now installed Initialize it We hold the lock in arenaStuff as setUpArena expects The loop ends because ret is now nonzero 57 Chapter 3 Sharing Memory Between Processes 58 awh setUpArena arena stuff usunsetlock stuff gt updateLock else uscasinfo either did not find a current value of 0 indicates a race with another process executing this code or it failed for some other rea
311. nts take a string and return ink and logical extents for each character in the string Use this for redrawing portions of strings or for word justification If the fontset might include context dependent drawing the client cannot assume that it can redraw individual characters and get the same rendering e XContextDependentDrawing returns a Boolean telling whether a fontset might include context dependent drawing 341 Chapter 14 Internationalizing Your Application Internationalization Support in Motif 342 Your applications can use Motif s internationalization capabilities Refer to the chapter titled Internationalization in the OSF Motif Programmer s Guide for information about the following topics e issues in internationalized applications e compound strings fonts and text display e localizing applications e advanced topics in internationalization There are some important points to remember when you internationalize and localize your application e At the top of your main program issue the call XtSetLanguageProc NULL NULL NULL e Translate your app defaults and install it in usr lib X11 LANG app defaults e Motif uses font sets and font lists to display text Specify a font list in your application defaults file using the following format fontList font list string Be sure to separate elements in the font list string as follows e Separate single fonts with a comma e Separate el
312. nversion specifications and escape sequences In the second statement the string from the catalog is treated as data and not interpreted for conversion specifications For further discussion of issues relating to this important distinction see Variably Ordered Referencing of printf Arguments XPG 4 Catalog Location XPG 4 message catalogs are located using the environment variable NLSPATH The default NLSPATH is nlslib L N where L is filled in by the LANG environment variable and N is filled in by the name argument to catopen NLSPATH can specify multiple pathnames in ordered precedence much like the PATH variable The following is asample NLSPATH assignment NLSPATH usr lib locale L N usr local lib locale L N usr defaults N Creating XPG 4 Message Catalogs Message catalogs are of this general form these forms are detailed in the gencat 1 reference page Sset n comment a message a n b message b n c message c n Squote d message d Sthis is a comment Each message is identified by a message number and a set Sets are often used to separate messages into more easily usable groups such as error messages help messages directives and so on Alternatively you could use a different set for each source file containing all of that source file s messages Strings and Message Catalogs set n specifies the beginning of set n where n is a set identifier in the range from 1 to NL_SETMAX All messa
313. o ask for timer intervals with fine granularity sub millisecond precision Only processes that executed under real time scheduling priority could ask for precise timer intervals Starting with IRIX 6 2 in systems with hardware support for timers any process can request a timer interval with any precision If this support is misused it is possible to cause performance problems For example a process can set up a repeating timer at an interval so short that one CPU is monopolized by setting and handling that timer 119 Chapter 5 Signalling Events 120 POSIX Timers IRIX supports the time and timer facilities specified by IEEE standard 1003 1b 1993 commonly called POSIX timers This timer interface is the most complete robust and portable and is recommended for all new applications The functions it includes for time measurement are summarized in Table 5 8 Table 5 8 POSIX Time Management Functions Function Name Purpose and Operation time 2 Return a time_t value containing the count of seconds elapsed since 00 00 00 UTC January 1 1970 times 2 Return user and system execution time consumption for the calling process and its terminated child processes clock_gettime 2 Return the instantaneous reading of one of two clocks the system time CLOCK_REALTIME or the hardware cycle counter CLOCK_SGI_CYCLE clock_getres 2 Return the precision of the system time CLOCK_REALTIME the hardware cycle counter in this sys
314. o maps the file in order to fill it with data You can lock a mapped file into memory This is discussed further under Locking and Unlocking Pages in Memory on page 23 15 Chapter 1 Process Address Space 16 Mapped File Sizes Since the potential 32 bit address space is more than 2000 megabytes and the 64 bit address space vastly greater you can in theory map very large files into memory To map an entire file follow these steps 1 Open the file to get a file descriptor 2 Use lseek fd 0 SEEK_END to discover the size of the file see the Iseek 2 reference page 3 Map the file with an off of 0 and len of the file size Apparent Process Size When you map a large file into memory the space is counted as part of the virtual size of the process This can lead to very large apparent sizes For example under IRIX 5 3 and 6 2 the Object Server maps a large database into memory with the result that a typical result of ps l looks like this 70 S 0 566 10 26 20 33481 225 80272230 0 45 objectser The total virtual size of 33481 certainly gets your attention However note the more modest real storage size of 225 Most of the mapped pages are not in physical memory Also realize that the backing store for pages of a mapped file is the file itself no swap space is used Mapping Portions of a File You do not have to map the entire file you can map any portion of it from one page to the file size Simply spe
315. ocates an arenaStuff structure and also allocates the essential lock and puts it ina locked state Then it calls uscasinfo to swap the arenaStuff address for the expected value of 0 When the swap succeeds the process completes initializing the arena and releases the lock IRIX Shared Memory Arenas The call to uscasinfo could fail if between the time the process receives a 0 from usgetinfo and the time it calls uscasinfo another process executes this same code and installs its own arenaStuff The process handles this unusual event by releasing the items it allocated and repeating the whole process When unrelated processes join an arena with code like that shown in Example 3 3 they should terminate their use of the arena with code similar to Example 3 4 Example 3 4 Resigning From an Arena The following function reverses the operation of joinArena Even if the calling process is the last one to hold the arena nothing drastic is done This is because it is impossible to perform usinit usgetinfo ussetlock as an atomic sequence Once an arena comes into being it must remain usable until the entire application shuts down Unlinking the arena file can be the last thing that main does AY void resignArena usptr_t arena arenaStuff_t stuff arenaStuff_t usgetinfo arena ussetlock stuff gt updateLock stuff gt joinedProcs usunsetlock stuff gt updateLock It might se
316. ocess munpin 3C IRIX Unlock a specified range of addresses punlock SVR4 Unlock addresses locked by plock You should avoid mixing function families for example if you lock memory with the POSIX function mlock do not unlock the memory using munpin The mpin function maintains a counter for each locked page showing how many times it has been locked You must call munpin the same number of times before the page is unlocked This feature is not available through the POSIX and SVR 4 interfaces Reducing Cache Misses Locked pages of an address space are unlocked when the last process using the address space terminates Locked pages of a mapped segment are unlocked when the last process that mapped the segment unmaps it or terminates Reducing Cache Misses When performance requirements are high you become concerned not with the loss of milliseconds to a page fault but with the loss of microseconds to a cache miss When your program accesses instructions or data that are not in cache memory the CPU requests a load of a cache line an aligned block of bytes from main memory The size of a cache line differs from one hardware model and another but is usually 128 bytes Possibly hundreds of CPU clock cycles pass while the cache line is loaded Due to the pipeline architecture of the CPU it can often continue to work during this delay However multiple successive cache misses can bring effective work to a halt for tens of
317. ocess communication IPC mechanisms which are discussed in Chapter 2 Interprocess Communication These mechanisms can be used to exchange data and to coordinate the activities of multiple asynchronous processes within a single memory system Processes running in different nodes of an Array must use one of the distributed models see Distributed Computation Models on page 187 Parallel Execution Models In traditional UNIX practice one process creates another with the system call fork which makes a duplicate of the calling process after which the two copies execute in parallel Typically the new process immediately uses the exec function to load a new program The fork 2 reference page contains a complete list of the state values that are duplicated when a process is created The exec 2 reference page details the process of creating a new program image for execution IRIX also supports the system function sproc which creates a lightweight process A process created with sproc shares some of its process state values with its parent process the sproc 2 reference page details how this sharing is specified In particular a process made with sproc does not have its own address space It continues to execute in the address space of the original process In this respect a lightweight process is like a thread see Thread Level Parallelism on page 185 However a lightweight process differs from a thread in two
318. ock 3C SVR4 Lock all program text or all data or the entire address space Locking memory causes all pages of the specified segments to be defined before they are locked When virtual swap is in use it is possible to receive a SIGKILL exception while locking because there was not enough swap space to define all pages see Delayed and Immediate Space Definition on page 7 Locking pages in memory of course reduces the memory that is available for all other programs in the system Locking a large program increases the rate of page faults for other programs 23 Chapter 1 Process Address Space 24 Locking Program Text and Data Using mpin and mlock you have to calculate the starting address and the length of the segment to be locked It is relatively easy to calculate the starting address and length of global data or of a mapped segment but it can be awkward to learn the starting address and length of program text or of stack space Using mlockall you lock all of the program text and data as it exists at the time of the call You specify a flag either MCL_CURRENT or MCL_FUTURE to give the scope in time One possible way to lock only program text is to call mlockall with MCL_CURRENT early in the initialization of a program The program s text and static data are locked but not any dynamic or mapped pages that may be created subsequently Specific ranges of dynamic or mapped data can be locked with mlock as they
319. ock removal order 169 locks allocate 80 and shared arenas 80 operations on 81 log file warning messages 281 Ip log file warning messages 281 Iseek for file size 16 Macau country code 369 madvise 31 Index malloc 6 7 use 8 used to find limit of swap 7 MAP_AUTOGROW flag 13 15 19 MAP_FIXED flag 16 21 22 MAP_LOCAL flag 14 15 MAP_PRIVATE flag 14 17 MAP_SHARED flag 14 17 memalign 28 memory 3 31 address ranges of 3 backing store for 6 interrogating size of 10 locking pages in 23 27 page 5 protection 30 segment 4 See also memory mapping virtual memory 11 memory shared See IPC memory mapping 6 11 23 and file access permissions 17 at fixed addresses 22 choosing segment address for 21 conflicts with normal file access 17 for I O 15 18 locking mapped file 25 mandatory file locks with 18 of kernel memory 20 of NFS mounted filemsync 17 of physical memory 19 of segment of zeros 19 of VME device 20 private copy of file 18 replacing a mapped segment 17 to create shared segments 18 when pages are defined 15 MENUCMD 332 message catalogs 324 334 closing 325 file typing rules 332 incompatibilities 324 locating 326 MNLS fimtmsg 331 pfmt 330 pfmt flags 330 pfmt format strings 331 strings 328 using 328 NLSPATH 326 opening 325 reading 325 specifying MNLS 329 XPG 3 about 324 compiling 327 creating 326 us
320. of choice can be set explicitly once or it can be specified in each reference call Strings are read from a catalog via gettxt see the gettxt 3 reference page include lt unistd h gt char gettxt const char msgid const char defaultStr msgid is a string containing two fields separated by a colon msgfilename msgnumber The msgfilename is a catalog name as described previously in the Specifying MNLS Catalogs on page 329 For example to get message 10 from the MQ catalog you could use either char str gettxt MQ 10 Hello world n or setcat MQ str gettxt 10 Hello world n 329 Chapter 14 Internationalizing Your Application 330 Using pfmt pfmt is one of the most important routines dealing with MNLS catalogs because it is used to produce most system diagnostic messages pfmt formats like printf and produces standard error message formats see the pfmt 3 reference page for the function or pfmt 1 for shell use It can usually be used in place of perror For example pfmt stderr MM_ERROR MQ 64 Permission denied would produce by default such as when the Mozambique locale is unavailable ERROR Permission denied The syntax of pfmt is include lt pfmt h gt int pfmt FILE stream long flags char format The flags are used to indicate severity type or control details to pfmt The format string includes information specifying w
321. of these directives in a serial program e MIPSpro Fortran 90 supports parallelizing directives similar to MIPSpro Fortran 77 and the MIPSpro POWER Fortran 90 product automates their placement e MIPSpro POWER C supports compiler pragmas that command parallel execution of segments of code The IRIS POWER C analyzer automates the insertion of these pragmas in a serial program In all three languages the run time library which provides the execution environment for the compiled program contains support for parallel execution The compiler generates library calls The library functions create lightweight processes using sproc and distribute loop iterations among them The run time support can adapt itself dynamically to the number of available CPUs Alternatively you can control it either using program source statements or using environment variables at execution time to use a certain number of CPUs Statement level parallel support is based on using common variables in memory and so it can be used only within the bounds of a single memory system a CHALLENGE system or a single node in a POWER CHALLENGEarray system Distributed Computation Models You can distribute a computation by putting parts of the work on different computers Two models of distributed execution are supported by Silicon Graphics systems Each is a formal abstract model for distributing a computation across the nodes of a multiple memory system without
322. ograms in this section illustrate the use of some of the SVR4 shared memory system functions Example of Creating a Shared Segment The program in Example 3 5 illustrates the use of shmget You can specify command parameters to exercise any combination of shmget function arguments Example 3 5 shmget System Call Example Program to test shmget 2 for creating a segment shmget k lt key gt s lt size gt p lt perms gt c x k lt key gt the key to use default 0 IPC_PRIVATE s lt size gt size of segment default is 64KB p lt perms gt permissions to use default is 0600 x use IPC_EXCL Q use IPC_CREAT xy include lt unistd h gt for getopt include lt sys shm h gt for shmget etc include lt errno h gt errno and perror include lt stdio h gt int main int argc char argv key_t key IPC_PRIVATE key size_t size 65536 size int perms 0600 permissions int shmflg 0 flag values struct shmid_ds ds info struct int c shmid whil eta getopt argc argv k s p cx switch c 62 System V Shared Memory Functions case k key key key_t strtoul optarg NULL 0 break case s size size size_t strtoul optarg NULL 0 break case p permissions perms int strtoul optarg NULL 0 break case c shmflg IP
323. oldP policy struct sched_param sp void pthread_getschedparam myTID amp policy amp sp oldP sp sched_priority sp sched_priority newP ret pthread_setschedparam myTID policy amp sp if ret perror pthread_setschedparam return oldP 225 Chapter 11 Thread Level Parallelism Synchronizing Pthreads 226 Asynchronous threads using a common address space must cooperate and coordinate their use of shared variables Independent processes coordinate using the mechanisms described in previous chapters IRIX semaphores and locks and SVR4 semaphores Threads cannot use these IPC mechanisms Threads can coordinate using these mechanisms e POSIX unnamed semaphores for general coordination and resource management see Managing Unnamed Semaphores on page 73 e POSIX or SVR4 message queues see Chapter 6 Message Queues e Mutex objects which allow threads to gain exclusive use of a shared variable see Mutexes on page 226 e Condition variables which allow a thread to wait when a controlling predicate is false see Condition Variables on page 229 You cannot use IRIX semaphores locks and barriers to coordinate between multiple threads within a single program Nor can you use SVR4 semaphores for this purpose Mutexes A mutex is a software object that stands for the right to modify some shared variable or the right to execute a critical section of code A mutex can be own
324. omp compiles a pattern string re_exec applies the last compiled pattern against a target string No means of storing compiled patterns No documentation of supported syntax but cross references ed 1 with which it may or may not be compatible regexp 5 Function compile compiles a pattern string step or advance applies a stored pattern against a target string Unusual interface compiles these functions directly into your source module using macro functions you must define Pattern syntax clearly documented wsregexp 3W Function wsrecompile compiles a pattern string wsrestep or wsrematch applies a pattern against a target Both pattern and target strings are wide characters Expression syntax is that of regexp augmented with internationalization expressions 317 Chapter 14 Internationalizing Your Application 318 Internationalized Regular Expressions A few utilities distributed with IRIX in particular grep see the grep 1 reference page support internationalized regular expressions which provide additional syntax for matching character classes sequences or ranges The internationalized regular expressions supported by the wsregexp library are as shown in Table 14 7 Table 14 7 Character Expressions in Internationalized Regular Expressions Expression Description c class The single character c where c is not a special character A character class expression Any character of type
325. on inline functions and cache management 28 input methods See internationalization input methods internationalization 285 365 ANSI compatible functions 313 character classification 309 character classification tables 315 character expressions 318 character sets and X 336 defined 298 373 Index codesets ASCII 299 301 defined 298 collating sequence tables 315 composing characters 345 configuration data 314 ctype 309 cultural data 320 customs 312 date formats 309 defined 287 eight bit cleanliness 299 encodings about 296 and filesystem 298 Asian languages 363 defined 298 EUC 364 European languages 362 ISO 10646 365 ISO 8859 362 Latin 1 362 multibyte 300 Unicode 365 wehar 300 304 file I O 305 file typing rules 332 fmtmsg 331 GL input 344 GUIs 359 361 composition 360 editres 361 icons 361 layout 360 localized layout 361 object labels 359 text labels 359 icons 361 initializing Xlib 337 input contexts 352 356 creating 355 374 styles 352 using 355 values 353 input methods 347 358 about 343 event handling 356 Off the Spot style 350 On the Spot style 351 opening 347 Over the Spot style 350 root window style 349 setting styles 351 status 349 strings 357 using styles 351 XFilterEvent 356 XLookupString 357 language information 316 languages Asian 363 364 in locale strings 295 Japanese 363 Latin library functions 312 loca
326. on the there that ought to be enough approach is chancy at best Popular Encodings Popular Encodings Localized Layout Some toolkits provide for layout control by run time reading of strings or other data files Applications that use such toolkits can easily finesse the layout issue by providing the capability for localization of the layout as well as localization of the contents of the layout This provides each localizer maximum freedom in presenting the application to the local users The application developer is responsible for providing localizers with instructions and the mechanisms necessary to produce layout data IRIS IM Localization With editres IRIX provides an interactive method of laying out widgets for IRIS IM and Xaw the Athena Widget Set a utility called editres With editres you can construct and edit resources and see how your widgets will look on the screen the program even generates a usable app defaults file for you But note that if you hard code any resources into your IRIS IM code you won t be able to edit them using this method Icons Icons attempt to be fairly generic representations of their antecedents Unfortunately it is very difficult for a designer to know what is generic or recognizable in other cultures Therefore it is important that any pictographic representations used by an application be localizable Graphic representations can be stored as strings representing X bitmaps as n
327. opriate to the user s native language and cultural environment Locale Specific Behavior The X Open definition includes the international functions in Table 14 4 as defined in Draft ANSI X3 159 Programming Language C ANSI functions that are enhanced by the X Open definition are marked with an asterisk Table 14 4 ANSI Compatible Functions Function Function continued atof scanf fprintf setlocale fscanf sprintf isalnum sscanf isalpha strcoll isgraph sterror islower strftime isprint strtod ispunct strxfrm isspace tolower isupper toupper printf Draft ANSI X3 159 Programming Language C also defines a number of multi byte functions and an additional function for manipulating monetary values At this stage the X Open definition is only guaranteed to work correctly for single byte 8 bit characters and thus does not include the multi byte functions 313 Chapter 14 Internationalizing Your Application 314 In addition X Open defines internationalized regular expression compile and match functions native language message handling functions and native language versions of the error handling functions see Table 14 5 Table 14 5 X Open Additional Functions Function Function continued catclose regexp catgets vfprintf catopen vprintf nl_langinfo vsprintf perror Native Language Support and the NLS Database The X Ope
328. or locale environment variables when locating resource files For string constants that are used within toolkit objects resources provide a simpler solution than do message catalogs These are some common objects that should definitely get their text from resources e Labels e Buttons e Menu items e Dialog notices and questions Any object that employs some sort of text label should be labeled via resources Since the localizer wants to provide strings for the local version of the application the app defaults file for the application should specify every reasonable string resource Reference pages should identify all localizable string resources Localizers of an application provide a separate resource file for each locale that the application runs in 359 Chapter 14 Internationalizing Your Application 360 Layout Layout management is of special interest when you cannot predict how large a button or other label might be The nature of the problem of layout composition and management does not change but one must construct the layout management without full knowledge of the final appearance It s worth noting that localization efforts can be assumed to be reasonable in some sense For example X resources have always allowed a user to specify an extremely large font for buttons but applications correctly choose to let such users live with the results But it s not always that clear what is reasonable and what isn
329. ord return 1 Lock next void lseek fd next 0 if lockf fd F_LOCK sizeof struct record lt 0 Failed to lock next release here void lseek fd here 0 void lockf fd F_ULOCK sizeof struct record and remove lock on this void lseek fd this 0 Using Record Locking void lockf fd F_ULOCK sizeof struct record return 1 return this Locks are removed in the same manner as they are set only the lock type is different F_UNLCK or F_ULOCK An unlock cannot be blocked by another process An unlock can affect only locks that were placed by the unlocking process Getting Lock Information You can determine which processes if any are blocking a lock from being set This can be used as a simple test or as a means to find locks on a file To find this information set up a lock as in the previous examples and use the F GETLK command in the fentl call If the lock passed to fentl would be blocked the first blocking lock is returned to the process through the structure passed to fentl That is the lock data passed to fentl is overwritten by blocking lock information The returned information includes two pieces of data _pidf and l_sysid that are used only with F_LGETLK These fields uniquely identify the process holding the lock For systems that do not support a distributed architecture the value in _sysid can be ignored If
330. ory for use calling brk as required See the brk 2 malloc 3 and malloc 3x reference pages An address is defined by entry in the page tables A defined address is always related to a backing store a source from which its contents can be retrieved A page in the data or stack segment is related to a page in a swap partition on disk The total size of the defined pages in an address space is its virtual size displayed by the ps command under the heading SZ see the ps 1 reference page Once addresses have been defined in the address space by allocation there is no way to undefine them except to terminate the process To free allocated memory makes the freed memory available for reuse within the process but the pages are still defined in the page tables and the swap space is still allocated Address Space Limits The segments of the address space have maximum sizes that are set as resource limits on the process Hard limits are set by these variables rlimit_umem_max Total size of the address space of a process rlimit_data_max Size of the portion of the address space used for data rlimit_stack_max Size of the portion of the address space used for stack The limits active during a login session can be displayed and changed using the C shell command limits The limits can be queried with getrlimit and changed with setrlimit see the getrlimit 2 reference page The initial default value and the possible range of a resource li
331. ot 8 bit clean Internationalized programs must be 8 bit clean because they cannot expect data to be in the form of ASCII bytes non ASCII character sets usually use all eight bits of each byte to specify the character But a program must go out of its way to manipulate bytes based on the value of the high bit and since changing data without cause is seldom desirable most programs are already 8 bit clean The old csh before this problem was fixed in the IRIX 5 0 release was a good example of a program that was not 8 bit clean it used the high bit in input strings to distinguish aliases from unaliased commands An effect of this misuse was that csh stripped the eighth bit from all characters For example the user command echo I know an architect named Mafnosa Produced the response I know an architect named Maqosa Another example is the specification of Internet messages which calls for 7 bit data Thus if sendmail fails to strip the 8th bit from a character prior to sending it it violates a protocol if it does strip the bit it could garble a non ASCII message this protocol problem is being addressed 299 Chapter 14 Internationalizing Your Application 300 One of the simplest things to do to remove the American bias from a program is to replace the ASCII assumption with the assumption that the Latin 1 codeset will be used This approach is not true internationalization but it can make the application usable in most of W
332. ou to set a limit on the aggregate size of queued messages but not on their number or their individual sizes e With a POSIX queue the choice of whether or not operations should block on a full or empty queue is an attribute of the queue descriptor With SVR4 you specify blocking or nonblocking operation on each send or receive operation e POSIX supports asynchronous notification of a message arrival SVR4 does not e SVR4 allows a receiver to request a message from a particular priority class in effect creating sub queues within the queue POSIX always returns the first message of the highest priority class Uses of Message Queues You can use message queues in a variety of ways For example you can use a message queue to implement the producer consumer model of cooperating processes or threads The producer sends its output to the queue the consumer receives the data from the queue When one process gets ahead of the other it is automatically suspended on the queue until the other process catches up 129 Chapter 6 Message Queues Another design model common in real time programming is to use message queues to dispatch units of work to waiting processes or threads A process or thread dedicated to one function waits on a message queue Whenever a unit of work is ready to execute it is sent to that queue as a message Another use of a message queue is to regulate the use of a scarce resource such as the bu
333. pace Note The function calloc touches all allocated pages in the course of filling them with zeros Hence memory allocated by calloc is defined as soon as it is allocated However you should not rely on this behavior It is possible to implement calloc in such a way that it like malloc does not define allocated pages until they are used This might be done in a future version of IRIX Page Validation Although an address is defined the corresponding page is not necessarily loaded in physical memory The sum of the defined address spaces of all processes is normally far larger than available real memory IRIX keeps selected pages in real memory A page that is not present in real memory is marked as invalid in the page tables The contents of invalid pages can be supplied in one of the following ways Text Pages of program text executable code of programs and dynamically linked libraries can be retrieved on demand from the program file or library files on disk Data Pages of data from the heap and stack can be retrieved from the swap partition or file on disk Mapped When a segment is created by mmap the backing store file is specified at creation time see Mapping Segments of Memory on page 11 Never used Pages that have been defined but never used can be created as pages of binary zero when they are needed When a process refers to a VPN that is defined but invalid a hardware interrupt occurs The int
334. panese sorting rules This would likely result in arbitrary seeming behavior 297 Chapter 14 Internationalizing Your Application No Filesystem Information for Encoding Types The IRIX filesystem does not contain information about what encoding should be associated with any given data Thus applications must assume that data presented to an application in some locale is properly encoded for that locale In other words a file is interpreted differently depending on locale there is no way to ask the file what it thinks its encoding is For example you may have created a file while in a Japanese locale using EUC Later you might try printing it while in a French locale The results will likely resemble a random collection of Latin 1 characters This problem applies to almost all stored strings Most strings are uninterpreted sequences of nonzero bytes This includes for example filenames You can if you want to name your files using Chinese characters in a Chinese locale but the names will look odd to anyone who runs bin Is on the same filesystem using a non Chinese locale Character Sets Codesets and Encodings 298 One major difference between nationalized and internationalized software is the availability in internationalized software of a wide variety of methods for encoding characters Developers of internationalized software no longer have the convenience of always being able to assume ASCII Three terms that describe gro
335. parallel 39 ps command 6 pscommand 9 PVM converting program to MPI program 244 258 differences from MPI 238 240 nonportable functions 243 R resident set size 9 rlimit kernel parameter 6 Index S Saudi Arabia country code 370 segment 4 heap 4 locking 24 lowest address 4 stack 4 text 4 segment address 21 segments at fixed offsets 21 semaphores operations on 79 polled 78 setlocal 294 setlocale 292 setrlimit 6 limit 8 shared arenas 39 82 barriers 82 initializing 51 locks 80 shared memory See IPC shared memory segment 18 shmat 61 shmctl 61 shmdt 61 SIGALRM from interval timer 125 SIGBUS on access to truncated mapped file 18 on NFS error in mapped file 17 on PIO access to invalid bus address 20 on reference past end of mapped segment 12 on reference to undefined page 5 SIGKILL on reaching limit of virtual swap 8 possible when locking pages 23 signal 104 SIGALRM 125 SIGBUS 5 12 17 18 20 SIGKILL 8 23 signal numbers 104 SIGSEGV 10 14 30 SIGSEGV on access to read only page 30 on attempt to change read only page 10 on store past end of mapped segment 14 South Africa country code 370 Spain country code 370 Speedo format fonts 271 sproc and mapped segments 14 stack segment 4 5 locking 24 structures and cache management 27 SVR4 and IPC 36 swap 6 9 Sweden country code 370 Switzerland country code 370 syntax
336. penpollsema usfreepollsema 3P Release arena memory used by a polled semaphore and invalidate any file descriptors assigned to it IRIX Facilities for Mutual Exclusion Operating on Semaphores The functions for semaphore operations are summarized in Table 4 6 Table 4 6 IRIX IPC Functions for Semaphore Operations Function Name Purpose and Operation uspsema 3P Perform the P operation on either type of semaphore usvsema 3P Perform the V operation on either type of semaphore ustestsema 3P Return the current instantaneous value of a semaphore uscpsema 3P Perform the P operation only if the resulting count will be nonnegative usinitsema 3P Reset a semaphore value and its metering information does not release any process waiting on the semaphore usctlsema 3P Set and reset semaphore metering information and other attributes usdumpsema 3P Dump semaphore metering information to a file To perform the P operation on a semaphore of either type use uspsema When the decremented semaphore value is nonnegative the function returns 1 The action when the decremented count would be negative differs between the polled and normal semaphores e When anormal semaphore count remains or becomes negative the calling process is blocked the function does not return until the count is nonnegative e When a polled semaphore count remains or becomes negative the function returns 0 and the calling process must use pol
337. permissions to use size to use use IPC_CREAT use IPC_EXCL key_t key IPC_PRIVATE int nsems 1 Le int perms 0600 eg int semflg 0 pr struct semid_ds ds int c semid include lt unistd h gt for getopt include lt sys sem h gt for shmget etc include lt errno h gt errno and perror int main int argc char argv key setsize permissions flag values info struct while 1 c getopt argc argv k switch c case k key key key_t strtoul optarg NULL break case s setsize nsems int strtoul optarg NULL break case p permissions perms int strtoul optarg NUL break case c semflg IPC_CREAT break case x semflg IPC_EXCL os default is 0600 default is 1 s xc System V Facilities for Mutual Exclusion break default unknown or missing argument return 1 semid semget key nsems semflg perms if 1 semid printf semid d n semid if 1 semctl1 semid 0 IPC_STAT amp ds printf owner uid gid d d creator uid gid d d mode 0 o nsems d n ds sem_perm uid ds sem_perm gid ds sem_perm cuid ds sem_perm cgid ds sem_perm mode ds sem_nsems else perror semctl IPC_STAT else perror semget return errno Example Uses of semctl for Management The
338. piler flags you define in your Makefile Table 5 5 Functions for BSD Signal Handling Function Name Purpose and Operation kill 3B Send a signal to a specified process or broadcast a signal to a process group or to all processes with the same effective user ID A duplicate of a pending signal is discarded killpg 3B Send a signal to all members of a process group A duplicate of a pending signal is discarded sigvec 3 Establish a policy of default ignore or catch for a specified signal signal 3B Simplified interface to sigvec sigstack 2B Establish an alternate stack for the use of signal handling functions sigsetmask 3 Set the active signal mask sigblock 3 Add blocked signals to the active signal mask sigpause 3B Wait for specified signals to arrive Only asynchronous signal handling is supported by the BSD interface It is possible to set and interrogate the signal mask in a single operation however the signal mask type is the integer so only signal numbers 1 32 can be blocked The BSD interface does not recognize higher numbered signals Timer Facilities Timer Facilities You use timer facilities for a number of purposes to get information about program performance to make a program pause for a certain time to program an interval of time and to create a timestamp value to store with other data Timed Pauses and Schedule Cession In many instances a program or a process within a multiprocess
339. plication running in an internationalized system must indicate how it wants the system to behave IRIX uses the concept of a locale to convey that information A process can have only one locale at a time Most internationalization interfaces rely on the locale of the current process being set properly the locale governs the behavior of certain library routines This section covers the following topics e Setting the Current Locale explains categories locales strings location of locale specific data and locale naming conventions e Limitations of the Locale System describes multilingual support misuses of locales and encoding You can find additional information in Locale Specific Behavior on page 311 which describes native language support regular expressions and cultural data Setting the Current Locale Applications begin in the C locale C is the name used to indicate the system default locale it usually corresponds to American English Applications should therefore call setlocale as soon as possible to put the process into the desired locale The syntax for setlocale is include lt locale h gt char setlocale int category const char locale The call almost always looks either like this if setlocale LC_ALL NULL exit_with_error Locales or like this if setlocale LC_ALL NULL setlocale LC_ALL C Details of the two parameters are given in th
340. ppropriate lock the mandatory test is unnecessary overhead Enforcing Mandatory Locking Mandatory locking is enforced on a file by file basis triggered by a bit in the file inode that is set by chmod see the chmod 1 and chmod 2 reference pages In order to enforce mandatory locking on a particular file turn on the set group ID bit along with a nonexecutable group permission as in these examples which are equivalent chmod 2644 target file chmod 1 target file The bit must be set before the file is opened a change has no effect on a file that is already open Example 7 9 shows a fragment of code that sets mandatory lock mode on a given filename Example 7 9 Setting Mandatory Locking Permission Bits include lt sys types h gt include lt sys stat h gt int setMandatoryLocking char filename int mode struct stat buf if stat filename amp buf lt 0 perror stat 2 return error mode buf st_mode ensure group execute permission 0010 bit is off mode amp S_IEXEC gt gt 3 turn on set group id bit in mode mode S_ISGID if chmod filename mode lt 0 perror chmod 2 return error return 0 When IRIX opens a file it checks to see whether both of two conditions are true e Set group ID bit is 1 e Group execute permission is 0 173 Chapter 7 File and Record Locking When both are true the file is marked for mandatory lock
341. program needs to suspend execution for a period of time IRIX contains a variety of functions that provide this capability The functions differ in their precision and in their portability Table 5 6 contains a summary Table 5 6 Functions for Timed Suspensions Reference Page Precision Compatibility Operation sched_yield 2 n a POSIX Defer to any processes eligible to run sginap 2 dispatching IRIX Defer to other processes for the specified interval 10ms number of dispatching cycles sleep 3C second POSIX Suspend for a number of seconds or until a signal arrives usleep 3C microsecond IRIX Suspend for a number of microseconds or until a signal arrives nanosleep 2 nanosecond POSIX Suspend for a number of seconds and nanoseconds or until a signal arrives Sometimes you do not want to suspend for any particular amount of time but simply want to make the current process defer to other processes so that any waiting processes receive a chance to run You can achieve this in two ways The IRIX unique function sginap accepts an argument of 0 meaning to defer for the minimum amount of time However sched_yield is a POSIX compliant function for this purpose 117 Chapter 5 Signalling Events 118 Time Data Structures The include files time h and sys time h define several data types and data structures related to time Some of these are used in POSIX time functions and others in BSD based functions and there ar
342. program in Example 4 4 semmod allows you to call semctl from the command line to display the size permissions and owner and creator IDs of a semaphore set and to change the permissions and owner It takes the following arguments on the command line k key Numeric key to identify the semaphore set for example k 99 iid Semaphore ID number alternative to specifying the key p perms Access permissions to apply to the selected set for example p 0664 u uid New user ID for the semaphore owner g gid New group ID for the semaphore owner 93 Chapter 4 Mutual Exclusion 94 If only the key or ID is given the program only displays the state of the set When you specify permissions owner or group the program first queries the current information to initialize an information structure Then it inserts the new items you specified and calls semctl with IPC_SET to change the information Example 4 4 Program to Demonstrate semctl for Management semmod program to test semctl 2 for status ownership and permissions semmod k lt key gt i lt semid gt p lt perms gt u lt user gt g lt group gt k lt key gt the key to use or i lt semid gt the semid to use p lt perms gt permissions to set with IPC_SET u lt uid gt uid to set as owner with IPC_SET g lt gid gt gid to set as owner with IPC_SET a include lt unistd h gt for getopt include lt sys se
343. protocol prevents this when a thread of higher priority blocks the thread holding the mutex has its priority boosted during the time it holds the mutex When round robin scheduling is used and a mutex represents a critical section of code a second problem can arise If a thread acquires the mutex enters the critical section and then is suspended because its time slice is up other threads can be blocked needlessly waiting for the mutex The PTHREAD_PRIO_PROTECT protocol prevents this Using pthread_mutexattr_setprioceiling you set a priority higher than normal for the mutex A thread that acquires the mutex runs at this higher priority while it holds the mutex This keeps it at the front of the round robin queue until it exits the critical section and releases the mutex Tip PTHREAD_PRIO_NONE uses a faster code path than the other two priority options for mutexes Synchronizing Pthreads Using Mutexes The functions for claiming releasing and using mutexes are summarized in Table 11 8 Table 11 8 Functions for Using Mutexes Function Purpose pthread_mutex_lock 3P Claim a mutex blocking until it is available pthread_mutex_trylock 3P Test a mutex and acquire it if it is available else return an error pthread_mutex_unlock 3P Release a mutex pthread_mutex_getprioceiling 3P Query the minimum priority of a mutex pthread_mutex_setprioceiling 3P Set the minimum priority of a mutex To determine where mutexes
344. r chooses the correct library based on the execution model usr lib libpthread so usr lib32 libpthread so and usr lib64 libpthread so However you must be sure that the needed version of the library is installed the n32 and 64 libraries do not install by default Note The definition of a threaded program or pthread program is a program that links with libpthread Do not link with libpthread unless you intend to use the pthread interface since libpthread replaces many standard library functions Tip Many names in libpthread override names defined in libc The linker displays warning messages about these overrides You can silence the warnings with the WI woff 85 compile option Debugging Pthread Programs The debugging and performance tuning tools distributed with IRIX and the IRIX developer s option can sometimes be used with a threaded program Compiling and Debugging a Pthread Application Debugging With dbx The dbx debugger is distributed with the IRIX Developer s Option Version 7 0 of dbx is required to work properly with pthreads When debugging a pthreads program you must set the following dbx variables e Set promptonfork to 2 e Set mp_program to 1 When you set a breakpoint with dbx it is global to all threads The first thread to reach the breakpoint trips the breakpoint This stops execution of the entire process all threads If you set the breakpoint in code used by more than one thread the pro
345. r converting a PVM program to an MPI program Initial Environment Setup PVM supports three different models of programming and the initial environment setup varies depending on the model in question The initial environment setup consists of determining the total number of PVM tasks to be used in the PVM job including those started by hand at a shell prompt and those started via a pym_spawn and using that as the initial static number for MPI If the program being ported relies on dynamic addition and deletion of hosts you must change the program to use a static number of hosts and tasks It is acommon practice in PVM programs to start a task by hand and then determine the machine configuration inside this task via the pym_config call so as to dynamically spawn tasks on the machines in the current configuration You must replace this practice with a static determination of the hosts and tasks that form an MPI parallel program The rest of this section discusses the three programming models supported by PVM and how to perform initial environment setup for each case Converting a PVM Program to an MPI Program Pure SPMD Program In the pure SPMD program model n instances of the same program are started as the n tasks of the parallel job using the spawn command of the PVM console or by hand at each of the n hosts simultaneously No tasks are dynamically spawned in the tasks that is the tasks do not use pym_spawn This scenario
346. r more information If you are writing a toolkit text object or if you can t use a toolkit to manage event processing for you then you have to deal with input methods Follow the instructions in User Input on page 343 Use resources to label any object that employs some sort of text label Your application s app defaults file should specify every reasonable string resource See X Resources for Strings on page 359 for more information Use dynamic layout objects that calculate layout depending on the natural localized size of the objects involved Some IRIS IM widgets providing these services are XmForm XmPaned Window and XmRowColumn See Dynamic Layout on page 360 for more information If you can t use dynamic layout objects refer to Layout on page 360 for instructions Make sure that all icons and other pictographic representations used by your application are localizable See Icons on page 361 for more information Additional Reading on Internationalization For more information on internationalization refer to O Reilly Volume 1 Xlib Programming Manual X Window System by Robert Scheifler and Jim Gettys X Open Portability Guide OSF Motif Style Guide 291 Chapter 14 Internationalizing Your Application Locales 292 An internationalized system is capable of presenting and receiving data understandably in a number of different formats cultures languages and character sets An ap
347. r normal 150 75 75 iso8859 1 sony fixed medium r normal 150 75 75 jisx0201 1976 0 A German locale would work with only the ISO font a Japanese locale might use all three a Chinese locale would have trouble with this fontset The developer should specify a default fontset suitable for the default locale Furthermore developers should ensure that the application accepts localized fontset specifications via resources or message catalogs or command line options Localizers are responsible for providing default fontset specifications suitable for their locales Creating a Fontset Creating fontsets in X is simply a matter of providing a string that names the fonts as described above Example 14 6 Creating a Fontset XFontSet fontset char base_name should get from resource char missingCharsetList int missingCharsetCount char defaultStringForMissingCharsets base_name fixed medium r 150 use resources fontset XCreateFontSet display base_name missingCharsetList missingCharsetCount amp defaultStringForMissingCharsets The locale in effect at create time is bound to the fontset Fontsets are freed with XFreeFontSet Using a Fontset Fontsets are used when rendering text with X11R6 Xmb or Xwe text rendering routines These routines are described in Text Rendering Routines 339 Chapter 14 Internationalizing Your Application 340 Text Rendering Routines
348. r read write access depending on the access permissions of the queue just as with a file Modifying a Message Queue You can use msgctl to modify four attributes of a queue after creating or accessing it e the user ID and group ID that owns the queue e the access permissions e the limit on the total size of all queued messages The size limit on a new queue is set to the system limit 32 768 bytes as of IRIX release 6 2 This determines how many messages can be waiting unreceived on the queue That in turn determines how far the message sending process can get ahead of the message reading process You can lower the limit to the sending process or thread more closely to the speed of the receiving process or thread Removing a Message Queue You can remove a message queue using the ipcrm command see the ipcrm 1 reference page or by calling msgctl and passing the IPC_RMID command code In many cases a message queue is meant for use within the scope of one program only and you do not want the queue to persist after the termination of that program Call msgctl to remove the queue as part of termination System V Message Queues Using SVR4 Message Queues The SVR4 functions for using message queues are summarized in Table 6 5 Table 6 5 SVR4 Functions for Using Message Queues Function Name Purpose and Operation msgsnd 2 Send a message to a queue msercv 2 Receive a message from a queue Sending a Message To se
349. raged to use XPG 4 to maximize their portability XPG 4 seems to be popular in Europe This section covers the following topics e XPG 4 Message Catalogs e SVR4 MNLS Message Catalogs e Variably Ordered Referencing of printf Arguments XPG 4 Message Catalogs The XPG 4 message catalog interface requires that a catalog be opened before it is read and requires that catalog references specify a catalog descriptor Since catalog references include a default to be used in case of failure applications will work normally without a catalog when in the default locale This means catalog generation is exclusively the task of localizers But in order to inform the localizer as to what strings to translate and how they should comprise a catalog the application developer should provide a catalog for the developer s locale Opening and Closing XPG 4 Catalogs catopen locates and opens a message catalog file include lt nl_types h gt nl_catd catopen char name int unused Strings and Message Catalogs The argument name is used to locate the catalog Usually this is a simple relative pathname that is combined with environment variables to indicate the path to the catalog see XPG 4 Catalog Location for details However the catalog assumes names that begin with are absolute pathnames Use of a hard coded pathname like this is strongly discouraged it doesn t allow the user to specify the catalog
350. ranslatable to a single MPI call are listed with a phrase such as communicators Finally nonportable routines are noted in the MPI column Most of these nonportable PVM routines do not have a Fortran counterpart which is also noted in the PVM column Note that this table does not exhaustively cover all aspects of PVM routines For instance it does not mention the various options of PVM calls Also there are some PVM routines that do have MPI counterparts but are needed only in special cases such as pvm_initsend and MPI_Send_init Some routines such as pym_bufinfo and MPI_Get_count have more than one corresponding call in MPI only one is listed in the table Table 12 1 Corresponding PVM and MPI Routines PVM Routine C Fortran MPI Routine C Fortran pom_addhosts pumfaddhost pom_barrier pomfbarrier pom_bcast pomfbcast pom_bufinfo pumfbufinfo pom_catchout pumfcatchout pom_config pomfconfig pom_delhosts pumfdelhost pom_exit pumfexit pom_freebuf pumffreebuf pom_gather pomfgather pom_getinst pomfgetinst pom_getopt pumfgetopt pom_getrbuf pumfgetrbuf pom_getsbuf pumfgetsbuf pom_gettid pomfgettid pom_gsize pumfgsize MPI_Barrier MPI_BARRIER MPI_Bcast MPI_BCAST MPI_Get_count MPI_GET_COUNT MPI _Finalize MPI_FINALIZE MPI_Buffer_detach MPI_BUFFER_DETACH MPI_Gather MPI_GATHER MPI_Group_rank MPI_GROUP_RANK Communicators Communicators MPI_Group_size MPI_GROUP_SIZE 241
351. rceClass XNResourceName XNStatusAttributes XNPreeditAttributes The resource class and name to use when the IM looks up resources that vary by IC The attributes to be used for any status and pre edit areas nested variable length lists Pre Edit and Status Attributes When an IM is going to provide state it needs some simple X information with which to do its work For example if an IM is going to draw status information ina client window in an Off the Spot style it needs to know where the area is what color and font to render text in and so on The application gives this data to the IC for use by the IM As with the IC Values section full details are available in X Window System Third Edition XNArea XNAreaNeeded XNBackgroundPixmap XNColormap XNCursor XNFontSet XNForeground XNBackground XNLineSpacing XNSpotLocation XNStdColormap A rectangle to be used as a status or pre edit area The rectangle desired by the attribute writer Either the application or the IM may provide this information depending on circumstances A pixmap to be used for the background of windows the IM creates The colormap to use The cursor to use The fontset to use for rendering text The colors to use for rendering The line spacing to be used in the pre edit window if more than one line is used Specifies where the next insertion point is for use by XIMPreeditPosition styles Specifies that the IM should
352. rd Locking Describes the different ways of locking files or records within files for exclusive use between processes and systems Chapter 2 Interprocess Communication The term interprocess communication IPC describes any method of coordinating the actions of multiple processes or sending data from one process to another IPC is commonly used to allow processes to coordinate the use of shared data objects for instance to let two programs update the same data in memory without interfering with each other or to make data acquired by one process available to others This chapter provides an overview of the IPC implementations available including Types of Interprocess Communication Available on page 36 Using POSIX IPC on page 38 Using IRIX IPC on page 39 Using System V IPC on page 39 Using 4 2 BSD IPC on page 42 The following chapters in this Part provide details as follows Chapter 3 Sharing Memory Between Processes covers shared memory Chapter 4 Mutual Exclusion covers semaphores locks and similar facilities Chapter 5 Signalling Events covers the different signal facilities Chapter 6 Message Queues describes two varieties of message queue Chapter 7 File and Record Locking describes the file locking facilities 35 Chapter 2 Interprocess Communication Types of Interprocess Communication Available IRIX is compatible with a broad
353. re Three results follow from the conventional method e A program can detect immediately when swap space is exhausted A call to malloc returns NULL when memory cannot be allocated A program can find the limits of swap space by making repeated calls to malloc e A large memory allocation by one program can fill swap causing other programs to see out of memory errors whether the program ever uses its allocated memory or not e A fork or exec call fails unless there is free space in swap equal to the data and stack sizes of the new process Chapter 1 Process Address Space By default in IRIX 5 2 and optionally in later releases IRIX uses a different method sometimes called virtual swap In this method the definition of new segments is delayed until the space is actually used Functions like brk and malloc merely test the new size of the data segment against the resource limits They do not actually define the new addresses and they do not cause swap disk space to be allocated Addresses are reserved with brk or malloc but they are only defined and allocated in swap when your program references them When IRIX uses delayed definition virtual swap it has the following effects e A program cannot find the limits of swap space using malloc which never returns NULL until the program exceeds its resource limit Instead when a program finally accesses a new page of allocated space and there is at tha
354. read is fixed in size The first pthread in a threaded program is no different from any other pthread in this regard Every pthread has a fixed size stack The first pthread has a stack of default size If your first or main pthread needs more than the default stack size the actual first started pthread must set the desired stack size and create a thread to be main and then terminate Executing and Terminating Pthreads The functions you use to manage the progress of a thread are summarized in Table 11 4 and described in the following topics Table 11 4 Functions for Managing Thread Execution Function Purpose pthread_atfork 3P pthread_cancel 3P pthread_cleanup_push 3P pthread_cleanup_pop 3P pthread_detach 3P pthread_exit 3P pthread_join 3P pthread_once 3P pthread_self 3P pthread_equal 3P pthread_setcancelstate 3P Register functions to handle the event of a fork Request cancellation of a specified thread Register function to handle the event of thread termination Unregister and optionally call termination handler Detach a terminated thread Explicitly terminate the calling thread Wait for a thread to terminate and receive its return value Execute initialization function once only Return the calling thread s ID Compare two thread IDs for equality Permit or block cancellation of the calling thread 215 Chapter 11 Thread Level Parallelism 216 Table 1
355. read_atfork see the exec 2 and fork 2 reference pages However if the new process continues to execute with the inherited address space including perhaps calls to library code that uses pthreads it may be necessary for the library code to reinitialize data in the address space of the child process You can do this in the fork event handlers Terminating and Being Terminated A thread begins execution in the function that is named in the pthread_create call When it returns from that function the thread terminates A thread can terminate earlier by calling pthread_exit In either case the thread returns a value of type void 217 Chapter 11 Thread Level Parallelism 218 One thread can request early termination of another by calling pthread_cancel passing the thread ID of the target thread A thread can protect itself against cancellation using two built in status switches e The pthread_setcancelstate function lets you prevent cancellation entirely PTHREAD_CANCEL_DISABLE or permit cancellation PTHREAD_CANCEL_ENABLE e The pthread_setcanceltype function lets you decide when cancellation will take place if it is allowed at all Cancellation can happen whenever it is requested PTHREAD_CANCEL_ASYNCHRONOUS or only at defined points PTHREAD_CANCEL_DEFERRED When you prevent cancellation by setting PTHREAD_CANCEL_DISABLE a cancellation request is blocked but remains pending until the thread terminates or chan
356. rep expr false Sgrep find gencat srep iconv kill lex In lp Ipstat Is mail mailx mkdir mv pack peat PS pr ps pwd red rm rmdir sed sh sleep sort stty tail tar tee test tr true tty umask uname uniq unpack uucp uulog uuname uupick uustat uuto uux wait we who Locale Specific Behavior The cc yacc and lex commands provide 8 bit transparency for characters contained in character strings character constants and comment strings An 8 bit character string enables a programmer to define default messages in languages other than English The support of 8 bit characters in identifier names is implementation defined The 8 bit operation of commands that communicate with other systems cannot be guaranteed in all circumstances For example intersystem mail may be restricted to 7 bit data by the underlying network 8 bit data and filenames may not be portable to noninternationalized systems and so forth Under these circumstances it is recommended that you use only characters defined in the ASCII 7 bit range of characters for data transfer between machines and you use only characters defined in the Portable Filename Character Set for naming remote files NLS Library Functions The list below shows library functions usable by internationalized application programs atof isgraph scanf toupper catclose islower setlocale vfprintf catgets isprint sprintf vprintf c
357. rogram Since tasks cannot enroll in and leave from an MPI run time environment more than once you must change all PVM tasks to reflect this requirement Typically a PVM task enrolls via the pym_mytid call in the absence of this call the first PVM call enrolls the calling task Additionally a task can call pym_mytid several times in a program with or without interleaved pvm_exit calls If it is not interleaved with pvm_exit calls the calling task simply gets its task ID back from the PVM library on the second and subsequent pym_mytid calls You can easily eliminate these subsequent pym_mytid calls from the program by saving the value of the task ID and passing it around Replace the first pym_mytid call ina PVM program with the MPI_Init routine which must precede all other MPI routines and must be called exactly once Since an MPI implementation can add its own command line arguments to be processed by MPI _Init you must place all the user s command line processing anything that accesses argc and argv after MPI_Init This requirement is in contrast to PVM programs since PVM does not add its own arguments to those of the tasks being started Converting a PVM Program to an MPI Program To find out the number of tasks in the parallel job and its own task ID an MPI task must call the functions MPI_Comm_size and MPI_Comm_rank Thus the initial portion of a typical MPI program looks like the following Initial
358. s and are summarized in Table 3 2 Table 3 2 IRIX Shared Arena Management Functions Function Name Purpose and Operation usconfig 3 Establish the default size of an arena the number of concurrent processes that can use it and the features of IPC objects in it usinit 3 Create an arena or join an existing arena usadd 3 Join an existing arena Initializing Arena Attributes A program creates a shared memory arena with the usinit function However many attributes of a new arena are set by preceding calls to usconfig The normal sequence of operations is to make several calls to usconfig to establish arena attributes then to make one call to usinit to create the arena You call usconfig to establish the features summarized in Table 3 3 Table 3 3 Arena Features Set Using usconfig usconfig Flag Name Meaning CONF_INITSIZE The initial size of the arena segment The default is 64 KB Often you know that more is needed CONF_AUTOGROW Whether or not the arena can grow automatically as more IPC objects or data objects are allocated default yes CONF_INITUSERS The largest number of concurrent processes that can use the arena The default is 8 if more processes than this will use IPC the limit must be set higher CONF_CHMOD The effective file permissions on arena access The default is 600 allowing only processes with the effective UID of the creating process to attach the arena CONF_ARENATYPE Establ
359. s depend upon how the lock interacts with the rest of the program Issues of portability and performance need to be considered Three methods for setting a lock are given here using the fentl system call using the usr group standards compatible lockf library function and using the BSD compatible flock library function Locking an entire file is just a special case of record locking one record is locked which has the size of the entire file The file is locked starting at a byte offset of zero and size of the maximum file size This size is beyond any real end of file so that no other lock can be placed on the file You have a choice of three functions for this operation the basic fentl the library function lockf and the BSD compatible library function flock All three functions can interoperate That is a lock placed by one is respected by the other two Whole File Lock With fentl The fentl function treats a lock length of 0 as meaning size of file The function lockWholeFile in Example 7 2 attempts a specified number of times to obtain a whole file lock using fentl When the lock is placed it returns 0 otherwise it returns the error code for the failure Using Record Locking Example 7 2 Setting a Whole File Lock With fentl include lt fcntl h gt include lt errno h gt define MAX _TRY 10 int lockWholeFile int fd int tries int limit tries tries MAX_TRY int try struct f
360. s has a mask and its own handlers Compiling and Debugging a Pthread Application Table 11 1 continued Comparison of Pthreads and Processes Attribute POSIX Threads Lightweight Processes UNIX Processes Resource limits Single process limits Single process limits Limits apply to each process separately Process ID One PID applies to all PID per process plus PID per process threads share group PID Effective user and Inherited and Inherited can be Inherited can be group IDs unchangeable changed changed It takes relatively little time to create or destroy a pthread as compared to creating a lightweight process On the other hand threads share all resources and attributes of a single process except for the signal mask see Pthreads and Signals on page 221 If you want each executing entity to have its own set of file descriptors or if you want to make sure that one entity cannot modify data shared with another entity you must use lightweight processes or normal processes Compiling and Debugging a Pthread Application A pthread application is a C program that uses some of the POSIX pthreads functions In order to use these functions and in order to access the thread safe versions of the standard I O macros you must include the proper header files and link with the pthreads library You can debug and analyze the compiled program using some of the tools available for IRIX Compiling Pthread Source The header f
361. s locale through environment variables When an application is finished using a message catalog it should close the catalog and free the descriptor using catclose int catclose nl_catd Using an XPG 4 Catalog Catalogs contain sets of numbered messages The application developer must know the contents of the catalog in order to specify the set and number of a message to be obtained catgets is used to retrieve strings from a message catalog see the catopen 3 and catgets 3 reference pages Example 14 3 shows a program that reads the first message from the first message set in the appropriate catalog and displays the result Example 14 3 Reading an XPG 4 Catalog include lt stdio h gt include lt locale h gt include lt nl_types h gt define SET1 1 define WRLD_MSG 1 int main nl_catd msgd char message setlocale LC_ALL msgd catopen hw 0 message catgets msgd SET1 WRLD_MSG Hello world n printf message catclose msgd 325 Chapter 14 Internationalizing Your Application 326 The previous example uses printf instead of puts in order to make a point the format string of printf came from a catalog Note the crucial difference between these two statements printf catgets msgd set num defaultStr printf s catgets msgd set num defaultStr In the first statement the catalog provides the printf formatting string possibly containing co
362. s not have read write or execute permission for those files If your application warrants the use of record locking make sure that the permissions on your files and directories are also set properly A record lock even a mandatory record lock protects only the records that are locked while they are locked Unlocked parts of the files can be corrupted if proper precautions are not taken Only a known set of programs or users should be able to read or write a database This can be enforced through file permissions as follows 1 Using the chown facility see the chown 1 and chown 2 reference pages set the ownership of the critical directories and files to reflect the authorized group ID 2 Using the chmod facility see also the chmod 1 and chmod 2 reference pages set the file permissions of the critical directories and files so that only members of the authorized group have write access 775 permissions 3 Using the chown facility set the accessing program executable files to be owned by the authorized group 4 Using the chmod facility set the set GID bit for each accessing program executable file and to permit execution by anyone 2755 permissions Using Record Locking Users who are not members of the authorized group cannot modify the critical directories and files However when an ordinary user executes one of the accessing programs the program automatically adopts the group ID of its owner The access
363. s still some years away 365 Appendix A ISO 3166 Country Names and Abbreviations Table A 1 lists the ISO 3166 country codes alphabetized by country name the table reads from left to right and top to bottom Table A 1 ISO 3166 Country Codes Country Name Code Country Name Code Country Name Code Afghanistan AF Albania AL Algeria DZ American Samoa AS Andorra AD Angola AO Anguilla Al Antarctica AQ Antigua and AG Barbuda Argentina AR Aruba AW Australia AU Austria AT Bahamas BS Bahrain BH Bangladesh BD Barbados BB Belgium BE Belize BZ Benin BJ Bermuda BM Bhutan BT Bolivia BO Botswana BW Bouvet Island BV Brazil BR British Indian IO Ocean Territory Brunei BN Bulgaria BG Burkina Faso BF Darussalam Burma BU Burundi BI Byelorussia BY Cameroon CM Canada CA Cape Verde CV Cayman Islands KY Central African CF Chad TD Republic Chile CL China CN Christmas Island CX Cocos Islands CC Colombia CO Comoros KM 367 ISO 3166 Country Names and Abbreviations 368 Table A 1 continued ISO 3166 Country Codes Country Name Code Country Name Code Country Name Code Congo CG Cook Islands CK Costa Rica CR Cote D Ivoire CI Cuba CU Cyprus CY Czech Republic CS Denmark DK Djibouti DJ Dominica DM Dominican DO Fast Timor TP Republic Ecuador EC Egypt EG El Salvador SV Equatorial GQ Ethiopia ET Falkland Islands FK Guinea Faroe Islands FO Fiji FJ Finland FI France FR French Guiana GF French Polynesia PF French Southern TF Gabon GA Ga
364. s that indicate that the next character and only the next character will be in a different codeset Very little application code should ever need to be aware of that though you should use the available library routines to find out information about multibyte strings rather than look at the underlying byte structure because that structure varies from one encoding to another For one example of an encoding that allows characters from multiple codesets see EUC on page 364 301 Chapter 14 Internationalizing Your Application 302 Use of Multibyte Strings Multibyte strings are very easy to pass around They efficiently use space both data and disk space since extra bytes are used only for characters that require them MB strings can be read and written without regard to their contents as long as the strings remain intact Displaying MB strings on a terminal is done with the usual routines printf puts and so on Many programs such as cat need never concern themselves with the multibyte nature of MB strings since they operate on bytes rather than on characters so MB strings are often used for string I O Manipulation of individual characters in an MB string can be difficult since finding a particular character or position in a string is nontrivial see Handling Multibyte Characters below Therefore it is common to convert to WC strings for that kind of work Handling Multibyte Characters Usually mul
365. s that together describe how to go about receiving and examining input under a given set of circumstances To set up and use an input context Decide what styles your application can support Query the IM to find out what styles it supports Find a match Create the IC 1 2 3 4 Determine information that the IC needs in order to work with your application 5 6 Employ the IC Find an IM Style The IM may be able to support multiple styles for example both Off the Spot and Root Window The application may be able to do in order of preference Over the Spot Off the Spot and Root Window The application should determine that the best match in this case is Off the Spot First discover what the IM can do then set up a variable describing what the application can do as shown in Example 14 8 Example 14 8 Finding What a Client Can Do XIMStyles IMcando XIMStyle clientCanDo note type difference XIMStyl styleWeWillUse NULL XGetImValues im XNQueryInputStyle amp IMcando NULL clientCanDo none XIMPreeditNone XIMStatusNone over XIMPreeditPosition XIMStatusArea off XIMPreeditArea XIMStatusArea root XIMPreeditNothing XIMStatusNothing User Input A client should always be able to handle the case of XIMPreeditNone XIMStatusNone which is likely in a Western locale To the application this is not very different from a RootWindow style but it comes with less ov
366. sed by all processes that have it open PART THREE Models of Parallel Computation Chapter 8 Models of Parallel Computation Provides an overview of the different models around which you can design a parallel or distributed application in Silicon Graphics systems Chapter 9 Statement Level Parallelism Gives an overview of the use of Power Fortran and Power C to execute do loops across multiple CPUs Chapter 10 Process Level Parallelism Describes the use of IRIX processes to execute in parallel within one address space or in multiple address spaces Chapter 11 Thread Level Parallelism Describes the use of POSIX threads IEEE 1003 1c for parallel execution within a single address space Chapter 12 Distributed Process Parallelism Describes two different facilities for distributing an application across multiple host computers PVM and MPI Chapter 8 Models of Parallel Computation You design a program to perform computations in parallel in order to get higher performance by bringing more hardware to bear on the problem concurrently In order to succeed you need to understand the hardware architecture of the target system and also the software interfaces that are available The purpose of this chapter is to give a high level overview of parallel programming models and of the hardware that they use The parallel models are discussed in more detail in following chapters 179
367. semaphore 74 POSIX Facilities for Mutual Exclusion The sem_open function takes the following arguments name Name of the semaphore in the form of a file pathname oflag Either zero or O_CREAT or O_CREAT O_EXCL mode The access permissions to apply if the semaphore is created value Initial value of the semaphore Creating a Named Semaphore The POSIX standard leaves it to the implementation whether or not a named semaphore is represented by a disk file The IRIX implementation does create a file to stand for each named semaphore see POSIX IPC Name Space on page 38 The file that stands for a semaphore takes up no disk space other than the file node in a directory The oflag is used to handle the following cases e Specify 0 to receive an error if the semaphore does not exist that is to require that the semaphore must exist e Specify O_CREAT O_EXCL to receive an error if the semaphore does exist that is to require that the semaphore not exist e Specify O_CREAT to have the semaphore created if necessary When sem_open creates a semaphore it sets the file permissions specified by mode These permissions control access to a semaphore by UID and GID just as for a file See the open 2 and chmod 2 reference pages When sem_open creates a semaphore it sets the initial value to value or to 0 if value is not specified Otherwise the value depends on the history of the semaphore since it was created T
368. setlocale returns the name of the current locale Locales Nonempty Strings in Calls to setlocale Here are the possibilities for specifying the locale parameter NULL Specifying a null pointer argument not the same as the empty string causes setlocale to return the name of the current locale C Specifying a locale value of the single character string C requests whatever locale the system uses as a default Note that this is a string and not just a character Other strings Request a particular locale by specifying its name This overrides any user preferences and should only be done with good reason Location of Locale Specific Data Except for XPG 4 message catalogs locale specific data that is the compiled files containing the collation information monetary information and so on are located in usr lib locale lt locale gt lt category gt where lt locale gt and lt category gt are the names of the locale and category respectively For example the database for the LC_COLLATE category of the French locale fr would be in usr lib locale fr LC_COLLATE There will probably be multiple locales symbolically linked to each other usually in cases where a specific locale name points to the more general case For example usr libflocale En_US ascii might point to usr libflocale C Locale Naming Conventions A locale string is of the form language _territory encoding modifier
369. should be used examine the memory variables and other objects such as files that can be accessed from multiple threads Create a mutex for each set of shared objects that are used together Ensure that the code acquires the proper mutex before it modifies the shared objects You acquire a mutex by calling pthread_mutex_lock and release it with pthread_mutex_unlock When a thread must not be blocked it can use pthread_mutex_trylock to test the mutex and lock it only if it is available Condition Variables A condition variable provides a way in which a thread can temporarily give up ownership of a mutex wait for a condition to be true and then reclaim ownership of the mutex all in a single operation 229 Chapter 11 Thread Level Parallelism 230 Preparing Condition Variables Like mutexes and threads themselves condition variables are supplied with a mechanism of attribute objects pthread_condattr_t objects and static and dynamic initializers However a condition variable has no useful attributes to initialize in this implementation The functions for initializing one are summarized in Table 11 9 Table 11 9 Functions for Preparing Condition Variables Function Purpose pthread_cond_init 3P Initialize a condition variable based on an attribute object pthread_condattr_init 3P Initialize a pthread_condattr_t to default attributes pthread_condattr_destroy 3P Uninitialize a pthread_condattr_t A condition
370. signal These and other options are spelled out under Signal Handling Policies on page 108 Scheduling Pthreads Receiving Signals Synchronously You can design a program to receive signals in a synchronous manner instead of asynchronously To do this set a mask that blocks all the signals that are to be received synchronously Then call one of the following three functions sigwait 3 Suspend until one of a specified set of signals is generated then return the signal number sigwaitinfo 3 Like sigwait but returns additional information about the signal sigtimedwait 3 Like sigwaitinfo but also returns after a specified time has elapsed if no signal is received Using these functions you can write a thread that treats arriving signals as a stream of events to be processed This is generally the safest program model much easier to work with than the asynchronous model of signal delivery Scheduling Pthreads By default the pthreads library schedules the threads of a process in a round robin fashion Much of the scheduling machinery is done in the library within the context of the user process without assistance from the IRIX kernel On a multiprocessor threads can run concurrently The scheduling algorithm is controlled by two parameters a policy and a priority for each thread These variables are set initially when the thread is created see Initial Scheduling Priority and Policy on page 213 and can be mo
371. signal could be taken while your handler executes resulting in multiple entries to the handler When not set if this signal interrupts a blocked system function the system function returns EINTR When set the system function is restarted Signals System V Signal Facility The System V signal interface is compatible with code ported from UNIX System V It includes compatibility for release 3 SVR3 and release 4 SVR4 Table 5 4 summarizes the functions you use to manage signals through this interface Table 5 4 Functions for SVR4 Signal Handling Function Purpose kill 2 Send a signal to a process or process group A duplicate of a pending signal is discarded sigsend 2 Send a signal to a set of processes or process groups specified in a variety of ways for example by user ID signal 2 SVR3 call to establish handling policy of default ignore or catch for a specified signal sigset 2 SVR amp 4 call to establish handling policy of default ignore or catch for a specified signal sighold 2 Hold block a specified signal sigignore 2 Set the handling for a specified signal to Ignore sigrelse 2 Release unblock a specified signal sigpause 2 Suspend the calling process until a specified signal arrives Only asynchronous signal handling is supported by the System V interface Also you must block and unblock signals individually there is no support for setting the entire signal mask in one operation T
372. signal information You could construct a very similar work handling application using a message queue see Chapter 6 Message Queues However this design approach allows you to integrate the handling of unplanned signals such as SIGPIPE and interval timer signals such as SIGALRM into the same scheme as planned application events Using Asynchronous Handling Using sigaction you specify a function to be called when a particular signal is received You have a choice of function prototypes In each case the signal handler is passed the signal number additional information about the signal and information about the machine context at the time the signal was delivered Your signal handler can have the POSIX prototype as follows void name int sig siginfo_t sip ucontext_t up The second argument a POSIX information structure siginfo_t contains these fields si_signo The signal number again si_errno Either 0 or an error code from errno h si_code An indication of the source of the signal si_value When si_code is SI_QUEUE the union sigval passed to sigqueue si_pid When si_code is SI_LUSER the process ID that called kill 113 Chapter 5 Signalling Events 114 When the signal is an error reported by the kernel or hardware si_code is an explanatory number These values are spelled out in detail in the siginfo 5 reference page The third argument a pointer to a ucontext_t object gives the machine state
373. son In any case release allocated stuff and repeat the loop ret 0 Erf usfreelock stuff gt updatelock arena usfree stuff arena usgetinfo returned 0 while uscasinfo swap fails arena gt initialized arena updateLock not held return arena Example 3 3 assumes that everything allocated in the arena is accessed through a collection of pointers arenaStuff The two problems to be solved are these e Which asynchronous process is the first to call usinit and therefore should allocate arenaStuff and initialize it with pointers to other objects e How can the second and subsequent processes know when the initialization of arenaStuff which might take some time is complete and the arena is completely ready for use The solution in Example 3 3 is based on the discussion in the uscasinfo 3P reference page Each process calls function joinArena If a call to usgetinfo returns nonzero it is the address of an arenaStuff_t that has been allocated by some other process Possibly that process is concurrently executing initializing the arena The current process waits until the lock in the arenaStuff_t is released On return from the ussetlock call the process has exclusive use of arenaStuff until it releases the lock It uses this exclusive control to increment the count of processes using the arena When usgetinfo returns 0 the calling process is probably the first to create the arena so it all
374. ss Address Space When planning a complex program you must understand how IRIX creates the virtual address space of a process and how you can modify the normal behavior of the address space The major topics covered here are as follows e Defining the Address Space on page 3 tells what the address space is and how it is created e Interrogating the Memory System on page 10 summarizes the ways your program can get information about the address space e Mapping Segments of Memory on page 11 documents the different ways that you can create new memory segments with predefined contents e Locking and Unlocking Pages in Memory on page 23 discusses when and how to lock pages of virtual memory to avoid page faults e Additional Memory Features on page 29 summarizes functions for address space management Defining the Address Space Each user level process has a virtual address space This term means nothing more than the set of memory addresses that the process can use without error When 32 bit addressing is in use addresses can range from 0 to Ox7fffffff that is 2 31 possible numbers for a total theoretical size of 2 gigabytes Numbers greater than 2431 are in the IRIX kernel s address space When 64 bit addressing is used a process s address space can encompass 240 numbers The numbers greater than 240 are reserved for kernel address spaces For more details on the structure of physical and virtual
375. ssumptions about languages local customs or coded character sets Such internationalized applications can run in a user s native environment following native conventions with native messages without recompiling or relinking A single copy of an internationalized program can be used by a world of different users Localization I10n Localization is the act of providing an internationalized application with the environment and data it needs to operate in a particular locale For example adding German system messages to IRIX is a part of localizing IRIX for the German locale 287 Chapter 14 Internationalizing Your Application 288 Nationalized Software Nationalized programs run in only one language and are governed by one set of customs in other words in a nationalized program the locale is built into the application Even if the application doesn t use ASCII or English as long as it is a single language program it is nationalized not internationalized Most older UNIX programs can be thought of as being nationalized for the United States Consider two applications hello and bonjour The application hello always produces the output Hello world and bonjour always produces Bonjour tout le monde Neither hello nor bonjour are internationalized they are both nationalized There are no special requirements for writing or porting nationalized applications whether they are text or graphics programs Terminal based pro
376. st the one at the lowest relative position specify B for addr and MAP_FIXED in flags 3 For the remaining segments specify B S for addr and MAP_FIXED in flags The initial large segment establishes a known base address and reserves enough address space to hold the other segments The later mappings replace the first one which cannot be used for its own sake Segments at a Fixed Address You can specify any value for addr IRIX creates the mapping if there is no conflict with an existing segment or returns an error if the mapping is impossible However you cannot normally tell what virtual addresses will be available for mapping in any particular installation or version of the operating system There are three exceptions First after IRIX has chosen an address for you you can always map anew segment of the same or shorter length at the same address This allows you to map different parts of a file into the same segment at different times see Mapping Portions of a File on page 16 Second the low 4 MB of the address space are unused see Address Space Boundaries on page 4 It is a very bad idea to map anything into the 0 page since that makes it hard to trap the use of uninitialized pointers But you can use other parts of the initial 4 MB for mapping Third the MIPS Application Binaly Interface ABI specification an extension of the System V ABI published by AT amp T states that addresses from 0x3000 0000 throu
377. struction sync to synchronize Full the cache with memory 85 Chapter 4 Mutual Exclusion 86 Each of the compiler intrinsics except __synchronize causes the compiler to generate inline code using Load Linked and Store Conditional to update memory predictably In this respect they are similar to the library functions documented in the test_and_set 3 and uscas 3 reference pages For example the statement __add_and_fetch amp shared 1 is functionally equivalent to the library call test_then_add amp shared 1 The compiler intrinsic ___compare_and_swap is simpler to use than uscas since you do not have to create a shared memory arena first The compiler intrinsics are different from the library functions and different from an assembly language subroutine you might write in one important way The optimizer phases of the compiler recognize these intrinsics as barriers to code motion The Barrier column in Table 4 10 shows this effect For example the compiler cannot move code in either direction across s use of __compare_and_swap However it can move code backward but not forward across __lock_test_and_set You can make the code motion barrier explicit or general If you invoke __compare_and_swap passing only the pointer and two value arguments the compiler can move no code across that source line Alternatively you can list specific variables as additional arguments to __compare_and_swap this
378. t System Call Example Program to test shmat shmat k lt key gt i lt id gt a lt addr gt r w k lt key gt the key to use to get an ID i lt id gt or the ID to use a lt addr gt address to attach default 0 s attach read only default read write w wait on keyboard input before detaching Ey include lt unistd h gt for getopt include lt sys shm h gt for shmget etc include lt errno h gt errno and perror include lt stdio h gt int main int argc char argv key_t key 1 key int shmid 1 or ID void addr 0 address to request void attach address gotten int rwflag 0 read or r w int wait 0 wait before detach int c ret whil 1 1 te getopt argc argv k i a rw switch c case k key key key_t strtoul optarg NULL 0 break case i id shmid int strtoul optarg NULL 0 break case a addr System V Shared Memory Functions addr void strtoul optarg NULL 0 break case r read write rwflag SHM_RDONLY break case w wait wait 1 break default return 1 1 shmid key must be given shmid shmget key 0 0 1 shmid we have an ID attach shmat shmid addr rwflag if attach void 1 printf Attached at Ox lx first word 0x l1x n attach pid_
379. t attach if rwflag SHM_RDONLY pid_t attach getpid printf Set first word to 0x 1lx n pid_t attach if wait char inp 80 printf Press return to detach gets inp printf First word is now 0x 1x n pid_t attach if shmdt attach perror shmdt else perror shmat else perror shmget return errno 65 Chapter 4 Mutual Exclusion You use mutual exclusion facilities whenever data is shared by multiple independent processes or threads Using such objects as locks also called mutexes and semaphores you can e ensure that only one process or thread uses a particular data structure at any time e coordinate the use of a shared collection such as a ring buffer or queue e synchronize activities so that processes or threads can wait for the completion of events or actions by other processes or threads In order to share data between processes you share memory between them Memory sharing is covered in Chapter 3 Sharing Memory Between Processes When independent processes share access to data in disk files they can ensure mutual exclusion using file locks which are covered in Chapter 7 File and Record Locking This chapter covers the following major topics e Overview of Mutual Exclusion on page 68 defines such terms as lock mutex semaphore and barrier e POSIX Facilities for Mutual Exclusion on page
380. t each on the queue Each message is an ASCII string containing the time and date and a serial number 1 lt count gt minimum message is 32 bytes Ky include lt sys msg h gt msg queue stuff ipc h types h include lt unistd h gt for getopt include lt errno h gt errno and perror include lt time h gt time 2 and ctime_r 3 include lt stdio h gt int main int argc char argv System V Message Queues key_t key key for msgget int msgid 1 specified or received msg queue id int msgflg 0 flag 0 or IPC_NOWAIT long type 1 message type 0 is not valid to msgsnd size_t bytes 64 message text size int count 1 number to send int c struct msgspace long type char text 32 msg while 1 c getopt argc argv k i t b c n switch c case k key key key_t strtoul optarg NULL 0 break case i id msqid int strtoul optarg NULL 0 break case t type type strtoul optarg NULL 0 break case b bytes bytes strtoul optarg NULL 0 if bytes lt 32 bytes 32 break case c count count strtoul optarg NULL 0 if count gt 99999 count 99999 break case n nowait msgflg IPC_NOWAIT break default unknown or missing argument return 1 msg struct msgspace calloc 1 sizeof long tbytes
381. t you don t always know what will be difficult to translate succinctly in some locale So while you need not provide for all combinations of resource specifications you must make the application localizable Three main approaches to the layout problem are described below dynamic layout constant layout and localized layout Dynamic Layout Most toolkits provide form pane rowcolumn or other layout objects that calculate layout depending on the natural localized size of the objects involved Most use some hints provided by the developer that can regulate this layout For example some IRIS IM widgets providing these services are XmForm XmPanedWindow and XmRowColumn Dynamic layout is probably the simplest way to prevent localization difficulties Note The IRIS IM product is the Silicon Graphics port of the OSF Motif product and should not be confused with IM the abbreviation for Input Methods Constant Layout Under certain circumstances an application may insist on having a predefined layout When this is so the application must provide objects that are constructed to allow localization A Quit button that just barely allows room for the Latin 1 string Quit is not likely to suffice when localizers attempt to fit their translations into that small space In order to enforce constant layout the developer incurs the heavy responsibility of making sure the objects are localizable This means a lot of investigati
382. t format when you create new font names For example Adobe provided Utopia Regular bitmap font files designed for the resolutions of 100 and 75 dpi The original names of these files were UTRG_10 bdf through UTRG_24 bdf Filenames closer to IRIX conventions are utopR10 through utopR24 followed by the appropriate file suffixes 3 Convert files in Bitmap Distribution Format BDF to Portable Compiled Format PCF font files BDF font files are text ASCII files You can think of them as source font files You can put BDF font files into an X font directory but noormal practice is to use only binary font formats such as the PCF pcf or compressed PCF format pcf Z for performance reasons Use the bdftopcf command to convert a BDF font file to a PCF font file see the bdftopcf 1 reference page For example Adobe provided two sets of Utopia Regular bitmap font files that were designed for the resolutions of 100 and 75 dpi These files were in the extended Bitmap BDF 2 1 format The original names of the bitmap files were UTRG_10 bdf through UTRG_24 bdf One of them could be converted with the following command bdftopcf o utopR10 pcf UTRG_10 bdf However you normally want to compress the PCF file as well You can compress a PCF file by entering a command such as compress utopR10 pcf But you could combine both steps simply as follows bdftopcf UTRG_10 bdf compress c gt utopR10 pcf Z 274 Installing and Adding Font and Fo
383. t next make next in list the head of list usunsetlock sprocListLock release sprochist return theSproc Start a function going asynchronously Called by master process xy void execFunc workFunc toCall void callWith usema_t done struct oneSproc theSproc getSproc theSproc gt calledFunc toCall set address of func to exec theSproc gt callArg callWith set argument to pass theSproc gt sprocDone done set sema to post on completion usvsema theSproc gt sprocWait wake up sleeping process Parallelism in Real Time Applications Parallelism in Real Time Applications In real time programs such as aircraft or vehicle simulators separate processes are used to divide the work of the simulation and distribute it onto multiple CPUs In these demanding applications the programmer frequently uses IRIX facilities to e reserve one or more CPUs of a multiprocessor for exclusive use by the application e isolate the reserved CPUs from all interrupts e assign specific processes to execute on specific reserved CPUs These facilities are described in detail in the REACT Real Time Programmer s Guide 007 2499 nnn Also covered in that book is the use of the Frame Scheduler an alternate process scheduler The normal process scheduling algorithm of the IRIX kernel attempts to keep all CPUs busy and to keep all processes advancing in a fair manner This algorit
384. t semzs 25 snapshot of zero waiting struct semid_ds ds int g whil Ce st e getopt argc argv k i switch c case k key key key_t strtoul optarg NULL 0 break case i semid semid int strtoul optarg NULL 0 break default unknown or missing argument return 1 System V Facilities for Mutual Exclusion if 1 semid i not given must have k semid semget key 0 0 if 1 semid if 0 semctl semid 0 IPC_STAT amp ds nsems ds sem_nsems semctl semid 0 GETALL semvals for j 0 j lt nsems j semns j semct1 semid j GETNCNT NULL semzs j semct1 semid j GETZCNT NULL printf vals for j 0 j lt nsems j printf 2d semvals j princit nnent for j 0 j lt nsems j printf 2d semns j printf nzcent for j3 0 j lt nsems j printf 2d semzs j putc n stdout else perror semctl IPC_STAT else perror semget Example Uses of semop The program in Example 4 6 semop performs one or more semaphore operations on a set you specify You can use it to specify any sequence of operations including nonsensical sequences from the command line The command arguments are k key i id Numeric key to identify the semaphore set for example k 99 Semaphore ID number alternative to spec
385. t such as a shared memory segment or message queue is named by a numeric key and has the following attributes which are defined in the header file sys ipc h e the UID and GID of the creating process e the UID and GID of the owning process which can be different from the creator e access permissions in the same format as used with files The commands and functions used to manage the IPC name space are listed in Table 2 2 Table 2 2 SVR4 IPC Name Space Management Function Name Purpose and Operation ipcs 1 List existing shared memory segments and other IPC objects in the system name space with their status iperm 1 Remove a shared memory segment or other IPC object from the system name space ftok 3 Create a semi unique numeric key based on a file pathname Configuring the IPC Name Space SVR4 IPC objects are stored in kernel tables of limited fixed size You configure the size of these tables by changing kernel tunable parameters These parameters are documented in detail in the book IRIX Admin System Configuration and Operation 007 2859 nnn See Appendix A IRIX Kernel Tunable Parameters Listing and Removing Persistent Objects Objects in the IPC name space are created by programs and can be removed by programs However IPC objects by definition are used by multiple processes and it is sometimes a problem to determine which process should remove an object and when it is safe to do so For this reason
386. t task spawns the remaining ones in the PVM version The second example is a general MPMD program based on the master slave paradigm with one master task and multiple slave tasks Both these examples are taken from the example set provided with the public domain PVM software Please note that several different translations are possible for each example and the ones given here may not be the most efficient ones Example 1 SPMD Program Note The group functions in the PVM version of the program are not necessary in the MPI counterpart since the basic group corresponding to MPI_COMM_WORLD containing all the tasks already exists in MPI SPMD Program in PVM Version a SPMD example using PVM 3 a also illustrating group functions Au define NPROC 4 include lt stdio h gt include lt sys types h gt include pvm3 h void dowork int me int nproc main int mytid my task id int tids NPROC array of task id int me my process number int i enroll in pvm mytid pvm_mytid Join a group and if I am the first instance i e me 0 spawn more copies of myself me pvm_joingroup foo printf me d mytid d n me mytid if me 0 249 Chapter 12 Distributed Process Parallelism 250 pvm_spawn spmd char 0 0 NPROC 1 amp tids 1 j Wait for everyone to startup before proceeding pvm_barrier foo NPROC ees dowork me NPROC
387. t they all execute at the same time provided there are enough CPUs to handle all the members of the group that are ready to run This minimizes the time that members of the share group spend waiting for each other to release locks or semaphores Use schedctl to initiate gang scheduling for the share group IRIX attempts to schedule all processes to execute at the same time when possible Note Through IRIX 6 2 schedctl also supported a scheduling mode called deadline scheduling This scheduling mode is being removed and will not be supported in the future Do not design a program based on the use of deadline scheduling 201 Chapter 10 Process Level Parallelism 202 Controlling Scheduling With POSIX Functions The POSIX compliant functions to control process scheduling are summarized in Table 10 4 Table 10 4 POSIX Functions for Scheduling Function Name Purpose and Operation sched_getparam 2 Query and change the POSIX scheduling priority of a process sched_setparam 2 sched_getscheduler 2 Query and change the POSIX scheduling policy and priority of a sched_setscheduler 2 process sched_get_priority_max 2 Query the maximum most use of CPU and minimum least use sched_get_priority_min 2 priority numbers for use with sched_getparam sched_get_rr_interval 2 Query the timeslice interval of the round robin scheduling policy sched_yield 2 Let other processes of the same priority execute
388. t time no room in the swap partition the program receives a SIGKILL signal e A large memory allocation by one program cannot monopolize the swap disk until the program actually uses the allocated memory if it ever does e Much less swap space is required for a successful fork call You can test whether the system uses virtual swap with the chkconfig command as described in the chkconfig 1 reference page chkconfig vswap echo S status 0 As you write a new program assume that virtual swap may be used Do not allocate memory merely to find out if you can Allocate no more memory than your program needs and use the memory immediately after allocating it If you are porting a program written for a conventional UNIX system you might discover that it tests the limits of allocatable memory by calling malloc Q until malloc Q returns a NULL and then does not use the memory In this case you have several choices e Recode this part of the program to derive the maximum memory size in some more reasonable and portable way for instance from an environment variable or the size of an input file e Using setrlimit set a lower maximum for rlimit_data_max so that malloc returns NULL at a reasonable allocation size see the getrlimit 2 reference page e Restore the conventional UNIX behavior for the whole system Use chkconfig to turn off the variable vswap and reboot see the chkconfig 1 reference page Defining the Address S
389. te Exclusive Lock A write lock is used to gain complete control over a record A write lock is an exclusive lock because when a write lock is in place on a record no other process may read or write lock that record or any data that overlaps it If a process holds a write lock it can assume that no other process will read or write that record at the same time Advisory Locking An advisory lock is visible only when a program explicitly tries to place a conflicting lock An advisory lock is not visible to the file I O system functions such as read and write A process that does not test for an advisory lock can violate the terms of the lock for example by writing into a locked record Advisory locks are useful when all processes make an appropriate record lock request before performing any I O operation When all processes use advisory locking access to the locked data is controlled by the advisory lock requests The success of advisory locking depends on the cooperation of all processes in enforcing the locking protocol it is not enforced by the file I O subsystem Mandatory Locking Mandatory record locking is enforced by the file I O system functions and so is effective on unrelated processes that are not part of a cooperating group Respect for locked records is enforced by the creat open read and write system calls When a record is locked access to that record by any other process is restricted according to the type o
390. te_initializer Executing and Terminating Pthreads Setting Event Handlers A thread can establish functions that are called when threads terminate and when the process forks Call pthread_cleanup_push to register a function that is to be called in the event that the current thread terminates either by exiting or by cancellation Call pthread_cleanup_pop to retract this registration and optionally to call the handler These functions are often used in library code with the push operation done on entry to the library and the pop done upon exit from the library The push and pop operations are in fact implemented partly as macro code For this reason calls to them must be strictly balanced a pop for each push and each push pop pair must appear in a single C lexical scope A nonstructured jump such as a longjmp see the setjmp 3 reference page or goto can cause unexpected results Call pthread_atfork to register three handlers related to a UNIX fork call The first handler executes just before the fork takes place the second executes just after the fork in the parent process the third executes just after the fork in the child process The fork operation creates a new process with a copy of the calling process s address space including any locked mutexes or semaphores Typically the new process immediately calls exec to replace the address space with a new program When this is the case there is no need for pth
391. tem CLOCK_SGI_CYCLE or the high resolution timer base CLOCK_SGI_FAST The POSIX functions for interval timers are summarized in Table 5 9 Table 5 9 POSIX Time Management Functions Function Name Purpose and Operation alarm 2 Cause a SIGALRM signal after a specified number of whole seconds timer_create 3C Create a POSIX timer and specify its time base CLOCK_REALTIME or CLOCK_SGI_FAST and the signal number it can generate timer_delete 3C Remove a timer created with timer_create timer_settime 3C Set expiration and reload times of a timer or disarm it timer_gettime 3C Query the time remaining in a timer timer_getoverrun 3C Query the number of overrun events generated by a timer Timer Facilities Getting Program Execution Time The times function returns counts of accumulated user process and system execution time These counts have a resolution of the system dispatching interval 10 milliseconds Creating Timestamps The time function returns a timestamp with a resolution of 1 second A timestamp with a resolution this coarse can be used only for infrequent events You can use the clock_gettime function to sample the system time with a resolution of 0 01 second or you can use it to read the hardware cycle counter a free running binary counter with an update frequency near the machine clock rate The clock_getres function returns the resolution of either of these clocks The program in Exa
392. tem lock cannot be established In this case locks are effective within the local system but are not effective against contending file access from other systems To discover whether rpc lockd is running use the chkconfig command o etc chkconfig grep lockd If the returned value is off rpc lockd is not running and locks have local scope only To use rpc lockd the administrator must configure it on as follows etc chkconfig lockd on Then the system must be rebooted This must be done on both the NFS file server and on all NFS clients where locks are requested Performance Impact Normally the NFS software uses a data cache to speed access to files Data read or written to NFS mounted files is held in a memory cache for some time and access requests to cached data is satisfied from memory instead of being read from the server Data caching has a major effect on the speed of NFS file access 175 Chapter 7 File and Record Locking 176 As soon as any process places a file or record lock on an NFS mounted file the file is marked as uncachable All I O requests for that file bypass the local memory cache and are sent to the NFS server This ensures consistent results and data integrity However it means that every read or write to the file at any offset and from any process incurs a network delay The file remains uncachable even when the lock is released The file cannot use the cache again until it has been clo
393. that is feasible Many existing message passing applications use the PVM library owing to its widespread use for the last five years In order to support this application base Silicon Graphics also supports PVM for Array systems However the design of the MPI interface is such that the performance of the MPI implementation on these systems is always better than the performance of PVM To obtain best performance porting parallel programs from PVM to MPI is recommended 237 Chapter 12 Distributed Process Parallelism This appendix covers the following main topics e Differences Between PVM and MPI on page 238 gives an overview of the differences that are likely to cause difficulty in porting e Comparing Library Routines on page 240 lists the PVM routines and their MPI counterparts when a counterpart exists e Converting a PVM Program to an MPI Program on page 244 covers the tasks involved in porting e Example Programs on page 249 shows example conversions Differences Between PVM and MPI 238 This section discusses the main differences between PVM and MPI from the user s perspective focusing mainly on PVM functions that are not available in MPI Although to a large extent the library calls of MPI and PVM provide similar functionality some PVM calls do not have a counterpart in MPI and vice versa Additionally the semantics of some of the equivalent calls are inherently different for the two li
394. the correct header files and link libraries when compiling The header files required for each function are listed in the reference pages for the functions One header file signal h declares both SVR4 and BSD signal handling functions Some of the BSD and SVR4 functions have the same names but different types of arguments or different results when called In order to declare the BSD family of signal functions in your program you must be sure to define the compiler variable _BSD_SIGNALS or _BSD_COMPAT to the compiler You could do this directly in the source code More often you will manage compilation with make and you will include D_BSD_SIGNALS as one of the compiler options in the Makefile The BSD compatible function for file locking flock is defined in the standard libc library That library is included automatically in any link by the cc command However when you are using C not C the function name flock conflicts with a structure name declared in sys fcntl h In order to define the flock function and not the structure define the compiler variable _BSD_COMPAT A BSD compatible kernel function for managing the termination of child processes wait3 is discussed under Process Reaping on page 199 Chapter 3 Sharing Memory Between Processes There are three families of functions that let you create a segment of memory and share it among the address spaces of multiple processes All produce the same
395. the message number in the catalog to use as the format defaultstring specifies the string to use if the catalog lookup fails for any reason An important feature of pfmt is its ability to refer to format arguments in format specified order just as printf does See Variably Ordered Referencing of printf Arguments for details Using fmtmsg fmtmsg is a comprehensive formatter using the MNLS catalogs and standard formats You probably won t need to use it most applications should get by with pfmt gettxt and printf Consult the fmtmsg 3 reference page for details 331 Chapter 14 Internationalizing Your Application 332 Internationalizing File Typing Rule Strings With MNLS You can internationalize the strings defined in the LEGEND and MENUCMD rules in the File Typing Rule FTR file To internationalize these rules precede the string with the following catalogname msgnumber catalogname is optional and should be a valid MNLS catalog msgnumber is the line number in catalogname If you omit catalogname the uxsgidesktop catalog is used by default You can use these rules to create your own FTR catalog For example an entry looks like this LEGEND mycatalog 7 Archive 8mm Tape Drive This entry uses line 7 from the catalog mycatalog as the LEGEND for this FTR If mycatalog is not available or line 7 is not accessible from mycatalog Archive 8mm Tape Drive is used
396. the receiving process or thread is running or ready to run the latency is fairly short and consistent from one signal to the next Even so it is not advisable to use a repeating itimer as the time base for a real time program Under less favorable conditions signal latency can be variable and sometimes lengthy tens of milliseconds relative to a fast timer frequency Timer Facilities How Timers Are Managed The IRIX kernel can be asked to implement itimers for many processes at once each interval having a different length and starting at a different time The kernel s method differs depending on the hardware architecture this issue is discussed at length in the timers 5 reference page e A few Silicon Graphics systems have no hardware support for interval timers so the kernel has to rely on frequent periodic interrupts as a time base In these systems the precision of timer interrupts is controlled by a kernel tuning variable fasthz which determines the rate at which the kernel is interrupted to poll for an expired timer e Innewer architectures each CPU has a clock comparator that the kernel can program to cause an interrupt after a specific interval has elapsed In these systems timer interrupts have sub microsecond precision and do not impose overhead for timer polling interrupts In earlier versions of IRIX in order to minimize the overhead of polling for elapsed timers the kernel did not allow normal processes t
397. then have to be changed to handle the blocked condition in each of the error return sections as in Example 7 2 167 Chapter 7 File and Record Locking 168 It is possible to unlock or change the type of lock on a subsection of a previously set lock this may cause an additional lock two locks for one system call to be used by the operating system This occurs if the subsection is from the middle of the previously set lock Example 7 6 shows a similar example using the lockf function Since it does not support read locks all write locks are referenced generically as locks Example 7 6 Record Locking Using lockf This function is called with a file descriptor and the offsets to three records in it this here and next The caller is assumed to hold no locks on any of the records This function tries to lock here and next using lockf If locks on here and next are obtained Set a lock on this Return index to this record If any lock is not obtained Remove all other locks Return 1 rf long set3Locks int fd long this long here long next Set a lock on here void lseek fd here 0 if lockf fd F_LOCK sizeof struct record lt 0 return 1 Lock this void lseek fd this 0 if lockf fd F_LOCK sizeof struct record lt 0 Failed to lock this clear here lock void lseek fd here 0 void lockf fd F_ULOCK sizeof struct rec
398. ther way MPI is preferable When the application runs in the context of a single Array system an MPI design has better performance PVM is discussed in more detail under Chapter 12 Distributed Process Parallelism Chapter 9 Statement Level Parallelism You can use statement level parallelism in three language packages Fortran 77 Fortran 90 and C This parallel model is unique in that you begin with a normal serial program and you can always return the program to serial execution by recompiling Every other parallel model requires you to plan and write a parallel program from the start Products for Statement Level Parallelism Software support for statement level parallelism is available from Silicon Graphics and from independent vendors Silicon Graphics Support The parallel features of the three languages from Silicon Graphics are documented in detail in the manuals listed in Table 9 1 Table 9 1 Documentation for Statement Level Parallel Products Document Manual Number Contents IRIS POWER C User s 007 0702 nnn Use of the IRIS POWER C Analyzer including all Guide pragmas MIPSpro Fortran 77 007 2361 nnn General use of Fortran 77 including parallelizing Programmer s Guide assertions and directives MIPSpro Power Fortran 77 007 2363 nnn Use of the Power Fortran source analyzer to place Programmer s Guide directives automatically 189 Chapter 9 Statement Level Parallelism Table 9 1 continued
399. threads are similar in some ways to IRIX lightweight processes made with sproc You use pthreads in preference to lightweight processes for two main reasons portability and performance A program based on pthreads is normally easier to port from another vendor s equipment than a program that depends on a unique facility such as sproc Table 11 1 summarizes some of the differences between pthreads and lightweight processes Table 11 1 Comparison of Pthreads and Processes Attribute POSIX Threads Lightweight Processes UNIX Processes Source portability Standard interface sproc is unique to fork is a UNIX portable between IRIX standard Creation overhead Relatively small Moderately large Quite large Block Unblock Dispatch Overhead Address space Memory mapped files and arenas Mutual exclusion objects Files pipes and I O streams Signal masks and signal handlers Few microseconds Mutexes and condition variables POSIX semaphores message Shared single process Each thread has a mask but handlers are shared Many microseconds Shared or copy on write or separate Shared or copy on write or separate IRIX semaphores and locks POSIX semaphores message queues Shared or separate file table Each process has a mask and its own handlers Many microseconds Separate Explicit sharing only IRIX semaphores and locks POSIX semaphores message queues Separate file table Each proces
400. through an uninitialized pointer variable causes a hardware exception Typically the text segments are at smaller virtual addresses and stack and data segments at larger ones although you should not write code that depends on this Tip The boundaries of all distributed DSOs are declared in the file usr lib so_locations When IRIX loads a DSO that is not declared in this file it seeks a segment of the address space that does not overlap any declared DSO and that will not interfere with growth of the stack segment Defining the Address Space Page Numbers and Offsets IRIX manages memory in units of a page The size of a page can differ from one system to another The size when 32 bit addressing is used is typically but not necessarily 4 096 bytes In each 32 bit virtual address e the least significant 12 bits specify an offset from 0 to OxOfff within a page e the most significant 20 bits specify a virtual page number VPN The page size when 64 bit addressing is used is greater than 4 096 bytes The page size in any case can differ between versions of IRIX but the bits of the virtual address are used in the same way the least significant bits of an address specify an offset within a page while the most significant bits specify the VPN You can learn the actual size of a page in the present system with getpagesize as noted under Interrogating the Memory System on page 10 Page tables built by IRIX during a fork or
401. tibyte characters are handled just like char strings Editing such strings however requires some care You cannot tell how many bytes are in a particular character until you look at the character You cannot look at the nth character in a string without looking at all the previous n 1 characters because you cannot tell where a character starts without knowing where the previous character ends Given a byte you don t know its position within a character Thus we say the string has state or is context sensitive that is the interpretation we assign to any given byte depends on where we are in a character This analysis of characters is locale dependent and therefore must be done by routines that understand locale Conversion to Constant Size Characters Multibyte characters and strings are convertible to wchars using mbtowc for individual characters and mbstowcs for strings see the mbtowc 3 and mbstowcs reference pages How Many Bytes in a Character To find out how many bytes make up a given single MB character use mblen as shown in Example 14 1 see also the mblen 3 reference page Character Sets Codesets and Encodings Example 14 1 Find Number of Bytes in an MB Character include lt stdlib h gt size_t n int len char pStr len mblen pStr n examine no more than n bytes It is the application s responsibility to ensure that pStr points to the beginning of a character not to the middle
402. til a signal handler begins to execute is the signal latency Signal latency can be long as real time programs measure time and signal latency has a high variability The IRIX kernel normally delivers a pending unblocked signal the next time the process returns to user code from the kernel domain In most cases this occurs e when the process is dispatched after a wait or preemption e upon return from a system function e upon return from the kernel s usual 10 millisecond tick dispatch interrupt SIGALRM which signals the expiration of a real time timer see Timer Facilities on page 117 is given special treatment It is delivered as soon as the kernel is ready to return to a user process after the timer interrupt in order to preserve timer accuracy When a process is ready to run and is not preempted by a process of higher priority and is executing in user code not calling a system function the latency for other than SIGALRM can be as much as 10 milliseconds However when the process is suspended for example waiting on a semaphore or when there are competing processes having higher priorities the delivery of a signal is delayed until the next time the receiving process is scheduled This can be many milliseconds In general you should use signals to deliver infrequent messages of high priority You should not use the exchange of signals as the basis for real time scheduling Signals Under X Windows If you plan
403. times e Character Classification and ctype discusses associations between character codes and using macros and functions from usr lib ctype h e Regular Expressions presents information for developers who do their own regular expression parsing and matching 305 Chapter 14 Internationalizing Your Application 306 Also see Cultural Data for additional information Collating Strings Different locales can have different rules governing collation of strings even within identical encodings The Issue In English sorting rules are extremely simple each character sorts to exactly one unique place Under ASCII the characters are even in numeric order However neither of those statements is necessarily true for other languages and other codesets Furthermore e Sorting order for a language may be completely unrelated to the numerical order of the characters in a given encoding e Even with a correctly sorted list of the characters in a character set you may not be able to sort words properly e Locales using identically encoded character sets may use very different sorting rules Programs using ASCII can do simple arithmetic on characters and directly calculate sorting relationships such programs frequently rely on truisms such as the fact that ral lt h in ASCII But internationalized programs cannot rely on ASCII and English sorting rules Consider some non English collation rule types e
404. tion to be called when the signal is received The signal handling function is entered asynchronously without regard for what the process was doing at the time the signal was delivered You cannot be sure what code was executing when the signal handler is called it could have been any function in your own code or it could have been code in the C library or in any layer of the X Windows or Motif support libraries All three interfaces provide for passing the signal number as the first argument of the signal handling function Other arguments to the handler function depend on the interface used and the options you specify when establishing the handler You can create an alternate memory area to be used as a stack when executing the signal handler Typically a signal handler does not require a great deal of stack space On the other hand each POSIX thread has limited stack space and when you provide an alternate signal handling stack you do not have to allow for possible signals in allocating thread stack space Synchronous Signal Handling Using the POSIX signal interface you can process signals in a synchronous way as a stream of input items to your program This allows you to design your program so that signals are received when the process is in a known state without the uncertainties of asynchronous delivery 109 Chapter 5 Signalling Events 110 Signal Latency The time that elapses from the momenta signal is generated un
405. tionalization support is provided on the X client side that is the application must take care of such support instead of relying on the X server No server changes are necessary and the protocol is unchanged Full backward compatibility is preserved so a new internationalized application can run on an old server Note X11R6 internationalization refers to features in X11R5 and X11R6 X uses existing internationalization standards to do its internationalization support there are no X specific interfaces to set and change locale Internationalized X applications receive no help from X when attempting multilingual support No locales or special process states are peculiar to X This section covers the following topics e Limitations of X11R6 in Supporting Internationalization discusses vertical text character sets and Xlib interface changes e Resource Names covers encoding of resource names e Getting X Internationalization Started describes initialization of Xlib and toolkit programming e Fontsets explains specifying creating and using fontsets e Text Rendering Routines discusses the XmbDrawText XmbDrawString and XmbDrawlmageString functions e New Text Extents Functions describes a few new extents related functions including XFontSetExtents Limitations of X11R6 in Supporting Internationalization Since X is locale independent there are some limitations on its ability to support
406. tions are defined in the standard libc library it is included automatically in any link by the cc command and in the libmpc library which you include with Impc IRIX IPC functions all require the use of a shared arena a segment of memory that can be mapped into the address spaces of multiple processes The first step in preparing to use any IRIX IPC object is to create a shared arena as documented under Initializing Arena Attributes on page 51 A shared arena is identified with a file that acts as the backing store for the arena memory Communicating processes gain access to the arena by specifying its filename All processes using the same arena have access to the same set of IPC objects This makes it relatively easy for unrelated processes to communicate using IRIX IPC they only have to know the filename of the arena to gain access IRIX supports SVR4 functions for signals shared memory semaphores message queues and file locking To use them you need to include the correct header files when compiling The header files required for each function are listed in the reference pages for the functions System V functions are primarily kernel functions No special library linkage is required to access them There is general discussion of SVR4 IPC operations in the intro 2 reference page 39 Chapter 2 Interprocess Communication 40 SVR4 IPC Name Space All SVR4 IPC objects are named in a special IPC name space An objec
407. tions create a lightweight process The difference between the calls is that sproc allocates a new memory segment to serve as the stack for the new process You use sprocsp to specify a stack segment that you have already allocated for example a block of memory that you allocate and lock against paging using mpin The sproc calls take as an argument the address of the function that the new process should execute The new process begins execution in that function and when that function returns the process is terminated Read the sproc 2 reference page for details on the flags that specify which process attributes a child process shares with its parent and for other comparisons between fork and sproc Note The sproc and sprocsp functions are blocked to your use in a threaded program see Chapter 11 Thread Level Parallelism The pthreads library uses lightweight processes to implement threading and has to control the creation of processes Also when your program uses the MPI library see Chapter 12 Distributed Process Parallelism the use of sproc and sprocsp can cause problems Process Management Certain system functions give you some control over the processes you create The prctl function offers a variety of operations These are some of the most useful PR_MAXPROCS Query the system limit on processes per user also available from sysconf _SC_CHILD_MA see sysconf 2 PR_MAXPPROCS Query the maxi
408. tl t2 item_t pl p2 IRIX Facilities for Mutual Exclusion push_item amp lifo amp tl push_item amp lifo amp t2 p2 pull_item amp lifo pl pull_item amp lifo printf Sx S3 P n ty printf x x n arena arena arena amp t1 amp t2 arena p1 p2 In Example 4 2 the push_item function pushes an item_t onto a LIFO queue and pull_item removes and returns the first item_t from a queue Both use uscas to update the queue anchor The main function contains a unit test of the functions first pushing two items then pulling them off finally displaying the addresses to verify that what was pushed could be pulled Using Compiler Intrinsics for Test and Set The MIPSpro C and C compilers version 7 0 introduce the intrinsic functions summarized in Table 4 10 Table 4 10 Compiler Intrinsics for Atomic Operations Intrinsic Prototype _ _op_and_fetch p v _ _fetch_and_op p v _ _lock_test_and_set p v _ _lock_release p ___compare_and_swap p w v _ _synchronize Purpose Barrier Atomically execute p op v p The op canbe Full add sub or and xor and nand Atomically execute t p p op v t The op can Full be add sub or and xor and nand Atomically execute t p p v tj Backward Atomically execute p 0 Forward Atomically execute w p p v 1 0 Full Issue the MIPS 3 in
409. tl 2 Query the status of a queue change its owner ID or access permissions or remove it from the system Unlike a POSIX message queue whose name is also a filename the external name of an SVR4 message queue is an integer held in an IPC name table see SVR4 IPC Name Space on page 40 You specify this key when creating the message queue and again whenever you access it for use Creating a Message Queue The msgget function has two purposes It is used to gain access to a queue that exists and it can create a queue that does not exist To create a new queue call msgget with the following arguments key An integer key that is not defined at this time msgflag A set of flags that includes IPC_CREAT and may include IPC_EXCL This value also contains the access permission bits For example a call to create a queue might be written as follows ret msgget PROJ_KEY IPC_CREAT IPC_EXCL 0660 This example relies on a constant PROJ_KEY to supply the key another option is to use the ftok library function see the ftok 3C reference page 143 Chapter 6 Message Queues 144 Accessing an Existing Queue When the program expects the queue to exist it calls msgget passing the expected key value and omitting the IPC_CREAT flag If the queue does not exist or if the effective user and group ID of the process are not allowed access to the queue an error is returned The program receives read only o
410. try is used for both bitmap and outline fonts 277 Chapter 13 Working With Fonts If you add your own local bitmap or outline fonts put an entry for each font family in the file called usr lib X11 fonts ps2xlfd_map local You can use entries in the file ps2xlfd_map as templates for entries in the file ps2xlfd_map local If the file ps2xlfd_map local does not exist log in as root and create it You can now access the font you added via the IRIS GL Font Manager Display PostScript is an extension of the X Window System To add an outline font in the Type 1 format to the rest of the X Window System in any directory enter the commands typelxfonts xset fp rehash This re creates symbolic links in the directory usr lib X11 fonts Typel that point to outline font files in the directory usr lib DPS outline base and instructs the X Window System to check which fonts are available To check whether the outline fonts you added are known to the X Window System enter xlsfonts grep family name The entries for the outline fonts you added should appear on the list of font names and aliases produced by xlsfonts Adding of large outline fonts in the CID keyed format is so complicated that you should contact Silicon Graphics if you want to add a font in that format You will need to provide CIDFont and AFM files for a CID keyed font If existing CMap files are not sufficient you will need to also provide one or more CMap fil
411. ually made parallel For each language there is a source level program analyzer that is sold as a separate product IRIS POWER C MIPSpro Power Fortran 77 MIPSpro Power Fortran 90 The analyzer identifies sections of the program that can safely be executed in parallel and automatically inserts the parallelizing directives After any logic change you can run the analysis again so that maintenance is easier Managing Statement Parallel Execution The source analyzer makes conservative assumptions about the way the program uses data As a result it often is unable to find all the potential parallelism However the analyzer produces a detailed listing of the program source showing each segment that could or could not be parallelized and why Directed by this listing you insert source assertions that give the analyzer more information about the program The method of creating an optimized parallel program is as follows 1 Write a complete application that runs on a single processor 2 Completely debug and verify the correctness of the program in serial execution 3 Apply the source analyzer and study the listing it produces 4 Add assertions to the source program These are not explicit commands to parallelize but high level statements that describe the program s use of data 5 Repeat steps 3 and 4 until the analyzer finds as much parallelism as possible 6 Run the program on a single memory multiprocessor When the progr
412. uct rminfo long freemem pages of free memory long availsmem total real swap memory space long availrmem available real memory space long bufmem not useful long physmem total real memory space A sample program that applies swapctl and sysmp to display these numbers is shipped in the 4DGifts example directory See 4Dgifts examples unix irix freeumen c Mapping Segments of Memory Your process can create new segments within the address space Such a mapped segment can represent the contents of a file a portion of VME A24 or A32 bus address space when a VME bus exists on the system a segment initialized to binary zero a POSIX shared memory object a view of the kernel s private address space or of physical memory 11 Chapter 1 Process Address Space 12 A mapped segment can be private to one address space or it can be shared between address spaces When shared it can be e read only to all processes e read write to the creating process and read only to others e read write to all sharing processes e copy on write so that any sharing process that modifies a page is given its own unique copy of that page Note Some of the memory mapping capabilities described in this section are unique to IRIX and nonportable Some of the capabilities are compatible with System V Release 4 SVR4 IRIX also supports the POSIX 1003 1b shared memory functions Compatibility issues
413. ued ISO 3166 Country Codes Country Name Code Country Name Code Country Name Code Sao Tome and ST Saudi Arabia SA Senegal SN Principe Seychelles SC Sierra Leone SL Singapore SG Solomon Islands SB Somalia SO South Africa ZA Spain ES Sri Lanka LK St Helena SH St Pierre and PM Sudan SD Suriname SR Miquelon Svalbard and Jan SJ Swaziland SZ Sweden SE Mayen Islands Switzerland CH Syrian Arab SY Taiwan TW Republic Tanzania TZ Thailand TH Togo TG Tokelau TK Tonga TO Trinidad and TT Tobago Tunisia TN Turkey TR Turks and Caicos TC Islands Tuvalu TV Uganda UG Ukraine UA United Arab AE United Kingdom GB United States UM Emirates Minor Outlying Islands Uruguay UY Vanuatu VU Vatican City State VA Venezuela VE Viet Nam VN Virgin Islands VG British Virgin Islands VI Wallis and WF Western Sahara EH USA Futuna Islands Yemen YEor Yugoslavia YU Zaire ZR YD Former Zambia ZM Zimbabwe ZW Index Numbers 32 bit addressing address size 3 page size 5 64 bit addressing address size 3 page size 5 8 bit clean codesets 299 A address range 3 address space 3 10 cannot undefine 6 copy on write pages 10 defining addresses 5 heap segment 4 interrogating 10 limits of 6 low 4 MB reserved 22 lowest used address 4 protection 30 read only pages 10 resident set size 9 segment 4 segment reserved for user mapping 22 stack segment 4 text segment 4 virtual size of 6 16 arenas IRIX IPC
414. ught a cup I bought a cup at Macy s In English we are able to come up with strings suitable for either word order in some other language we might not be so lucky Nor can we predict which order such languages might prefer So the developer has no way of knowing how to create traditional printf format strings suitable for all languages Developers should therefore use message catalogs for their printf format strings that take linguistic parameters and allow localizers to localize the format strings as well as text strings This means that the localizer has much greater ability to create intelligible text An internationalized version of the above code appears in Example 14 4 Example 14 4 Internationalized Code internationalized XPG 4 version char form catgets msgd set formNum At 1Ss I bought 2 s n char store catgets msgd set storeNum Macy s char obj catgets msgd set objNum a cup printf form store obj The unlocalized default version would produce At Macy s I bought a cup A localized version might produce Compr una tasa en Macy s In practice variably ordered format strings are found only in message catalogs and not in default strings The default string usually simply uses the parameters in the order they re given without the new variable order format strings Internationalization Support in X11R6 Internationalization Support in X11R6 X11R6 interna
415. uling types depend on the nature of the loops being parallelized For example e The SIMPLE method works well when N is relatively small However unless N is evenly divided by P there will be a time at the end of the loop when fewer than P processes are working and possibly only one e The DYNAMIC and INTERLEAVE methods allow you to set the chunk size so as to control the span of an array referenced by each process You can use this to reduce cache effects When N is very large so that not all data fits in memory INTERLEAVE may reduce the amount of paging compared to DYNAMIC e The guided self scheduling GSS method is good for triangular matrices and other algorithms where loop iterations become faster toward the end You can use source directives or pragmas within the program to specify the scheduling type and chunk size for particular loops Where you do not specify the scheduling the run time library uses a default method and chunk size You can establish this default scheduling type and chunk size using environment variables Chapter 10 Process Level Parallelism The process is the traditional unit of UNIX execution The concept of the process and its relationship to the concept of a thread are covered under Process Level Parallelism on page 184 The purpose of this chapter is to review how you can use IRIX processes to perform parallel processing in a single program Using Multiple Processes In general you c
416. unction might discover that the element is already busy In this case it must wait for the event element is no longer busy which is represented by the condition variable notBusy in the element In order to wait for this event getFromList calls pthread_cond_wait passing its list mutex and the condition variable point A in the code This releases the list mutex so that other threads can acquire the list and do their work on other elements When any thread wants to release the use of a list element it calls freeInList After clearing the busy flag in the list element freeInList announces that the event element is no longer busy has occurred by calling pthread_cond_signal This call releases a thread that is waiting at point A If there is more than one thread waiting for the same element the first in priority order is released The released thread re acquires the list mutex and resumes execution The first thing it does is to repeat its search of the list for the desired key and on finding the element again to test it again for busyness This repetition is needed because it is possible to get spurious returns from a condition variable When a thread wants to delete a list element it gets the list element by calling getFromList This ensures that the element is busy so no other thread is using it Then the thread calls deleteInList This function changes the list so it begins by acquiring the list mut
417. unique instance of the value stored under this key A thread can fetch only its own value which is the value stored by this same thread using pthread_setspecific Any thread s stored value is NULL until it stores a new value 219 Chapter 11 Thread Level Parallelism 220 When you create a key you can specify a destructor function that is called automatically when a thread terminates The destructor is called as long as the key is still valid and the key value for the terminating thread is not NULL The destructor receives the thread s value for the key as its argument You create keys by calling pthread_key_create Keys can be created before any threads are created However when you are designing a library module for use from any threaded program you need to create a key upon first entry to your library code This is an ideal application for a pthread_once_t variable see Initializing Static Data on page 216 The code in Example 11 3 suggests how a threaded module would create a key if necessary and initialize its contents for the current thread Example 11 3 Initializing Thread Unique Data typedef struct perThread_s items of data unique to thread perThread_t pthread_key_t perThreadKey key used to find per thread info pthread_once_t makePerThreadKey PTHREAD_ONCE_INIT Destructor function called when any thread exits with a non NULL value of perThreadKey a void deletePerThread void
418. upings of characters are the following character set An abstract collection of characters codeset A character set with exactly one associated numerical encoding for each character The English alphabet is a character set ASCII is a codeset encoding A set of characters and associated numbers however this term is more general than codeset A single encoding may include multiple codesets Extended UNIX Code EUC for instance is an encoding that provides for four codesets in one data stream Character Sets Codesets and Encodings This section describes these topics Fight Bit Cleanliness explains how to make 8 bit clean characters e Character Representation discuses multibyte and wide characters e Multibyte Characters covers using and handling multibyte characters conversions to constant size characters and the number of bytes in a character and string e Wide Characters explains wchar strings support routines and conversion to multibyte characters e Reading Input Data covers nonuser originated data For information on installing and using fonts with an application refer to Chapter 13 Working With Fonts Eight Bit Cleanliness A program is 8 bit clean if it does not use the high bit of any data byte to convey special information ASCII characters are specified by the low seven bits of a byte so some programs use the high bit of a data byte as a flag such programs are n
419. urns more information wait3 2 BSD extension of wait that allows you to poll for terminated children without suspending waitid 2 Function to suspend until one of a selected set of status changes occurs in one or more child processes When the parent process has nothing to do after starting the child processes it can loop on wait until wait reports no more children exist then it can exit Sometimes it is necessary to handle child termination and other work and the parent cannot suspend In this case the parent can treat the termination of a child process as an asynchronous event and trap it in a signal handler for SIGCLD see Catching Signals on page 109 The wait 2 reference page has extensive discussion of the three methods BSD SVR4 and POSIX for handling this situation with example code for each Process Scheduling There are two different approaches to setting the scheduling priorities of a process one compatible with IRIX and BSD the other POSIX compliant 199 Chapter 10 Process Level Parallelism 200 Controlling Scheduling With IRIX and BSD Compatible Facilities The IRIX compatible and BSD compatible scheduling operations are summarized in Table 10 3 Table 10 3 Commands and Functions for Scheduling Control Function Name Purpose and Operation schedctl 2 Query and set IRIX process scheduling attributes getpriority 2 Return the scheduling priority of a process or share group s
420. us Initialize MPI PI_TInit amp argce amp argv Get our task id our rank in the basic group PI_Comm_rank MPI_COMM_WORLD amp mytid Get the number of MPI tasks PI_Comm_size MPI_COMM_ WORLD amp ntasks Receive initial data from master msgtype 0 PI_Recv rbuff 1000 MPI_PACKED MPI_ANY SOURCE msgtype MPI_COMM WORLD amp status Find out master s task id master status MPI_SOURCE Unpack data position 0 MPTI_Unpack rbuff 1000 amp position amp n 1 MPI_INT MP I_COMM_ WORLD MPI_Unpack rbuff 1000 amp position data n MPI_FLOAT MP I_COMM_ WORLD Determine which slave I am value of me If mytid lt master me mytid Else me mytid 1 if mytid gt master me mytid 1l else me mytid Do calculations with data result work mytid me n data ntasks master Pack result position 0 MPTI_Pack amp me 1 MPI_INT sbuff 1000 amp position MPI_COMM_ WORLD MPTI_Pack amp result 1 MPI_FLOAT sbuff 1000 amp position MP I_COMM WORLD Send result to master msgtype 5 MPI_Send sbuff position MPI_PACKED master msgtype MP I_COMM_ WORLD Program finished Exit from MPI MPI_Finalize float 257 Chapter 12 Distributed Process Parallelism 258 work int mytid int me int n float data int ntasks Simpl xample slaves exchange data with left neighbor wrapping
421. use 3 Re claim the mutex for the shared resource These three actions are combined into one action using a condition variable When a thread claims a condition variable it must pass a mutex that it owns The claim releases the mutex waits and reclaims the mutex in one operation Barriers Barriers provide a convenient way of synchronizing parallel processes on multiprocessor systems To understand barriers think of a time when you planned to go to lunch with other people at your workplace The group agrees to meet in the lobby of the building Some of your coworkers reach the lobby early and others arrive later One comes running in last apologizing When all of you have gathered and you know that everyone is ready you all leave the building in a group A barrier is the software equivalent of the lobby where you waited A group of processes are going to work on a problem None should start until all the data has been initialized However starting each process is part of the initialization and they cannot all be started at the same time Each process must be created each must join an arena and perhaps open a file and you cannot predict when they will all be ready To coordinate them you create a barrier Each process when it is ready to start the main operation calls barrier passing the address of the barrier and the number of processes that will meet When that many processes have called barrier all of them are released to
422. use XGetRGBColormaps with the supplied property passed as an Atom in order to find out which colormap to use User Input Creating an Input Context Creating an input context is a simple matter of calling XCreateIC with a variable length list of parameters specifying IC values Example 14 10 shows a simple example that works for the root window Example 14 10 Creating an Input Context With XCreateIC XVaNestedList arglist XIC ic arglist XVaCreateNestedList 0 XNFontSet fontset XNForeground WhitePixel dpy screen XNBackground BlackPixel dpy screen NULL ic XCreateIC im XNInputStyle styleWeWillUse XNClientWindow window XNFocusWindow window XNStatusAttributes arglist XNPreeditAttributes arglist NULL XFree arglist if ic NULL exit_with_error Using the IC A multi window application may choose to use several input contexts But for simplicity assume that the application just wants to get to the internationalized input using one method in one window Using the IC is a matter of making sure you check events the IC wants and of setting IC focus If you are setting up a window for the first time you know the event mask you want and you can use it directly If you are attaching an IC to a previously configured window you should query the window and add in the new event mask 355 Chapter 14 Internationalizing Your Application 356 Example 14 11 Using the IC
423. variable must be initialized before use You can do this in one of three ways e Static assignment of the constant PTHREAD_COND_INITIALIZER e Calling pthread_cond_init passing NULL instead of the address of an attribute object e Calling pthread_cond_init passing a pthread_condattr_t object that you have set up with attribute values The first two methods initialize the variable to default attributes Dynamic initialization should be done only once see Initializing Static Data on page 216 Using Condition Variables A condition variable is a software object that represents a test of a Boolean condition Typically the condition changes because of a software event such as other thread has supplied needed data A thread that wants to wait for that event claims the condition variable which causes it to wait The thread that recognizes the event signals the condition variable releasing one or all threads that are waiting for the event Synchronizing Pthreads A thread holds a mutex that represents a shared resource While holding the mutex the thread finds that the shared resource is not complete or not ready The thread needs to do three things e Give up the mutex so that some other thread can renew the shared resource e Wait for the event that resource is now ready for use e Re acquire the mutex for the shared resource These three actions are combined into one using a condition variable The functions used
424. ving read access IPC_SET Set owner UID owner GID or access Creator UID owner UID or permissions superuser IPC_RMID Remove the set from the IPC name Creator UID owner UID or space superuser System V Facilities for Mutual Exclusion Table 4 12 continued SVR4 Semaphore Set Management Operations Keyword Operation Can Be Used By GETALL Copy current values of allsemaphores Any process having read access to an array SETALL Set current values of all semaphores Any process having write access from an array of integers Examples of some of these uses can be found under Example Uses of semctl for Management on page 93 In addition semctl allows you to query or set information about individual semaphores within the set as summarized in Table 4 13 Table 4 13 SVR4 Semaphore Management Operations Keyword Operation Can Be Used By GETVAL Return value of one semaphore Any process having read access GETPID Return process ID of the process that Any process having read access last operated on a semaphore GETNCNT Return number of processes waiting Any process having read access for one semaphore to exceed zero GETZCNT Return number of processes waiting Any process having read access for one semaphore to equal zero SETVAL Set current value of one semaphores Any process having write access Examples of some of these uses can be seen under Example Uses of semctl for Query on pa
425. wait on a sequence of operations The semsnap display verifies that one process is waiting on zero in semaphore 0 semop i 130 z 0 p 1 p 2 amp 9956 semsnap i 130 vals 1 1 0 0 nent O 0O 0 0 Zents lt 0 20 20 Semaphore 0 is decremented and semsnap reveals that there is no longer a process waiting for zero in that semaphore but that now a process is waiting for semaphore 2 to be incremented semop i 130 p 0 semsnap i 130 vals 0 1 0 0 nent 0 0 1 0 Zente 0 407m0 20 Semaphore 2 is incremented and now there are no processes waiting semop i 130 v 2 semsnap i 130 vals 0 0 0 0 nent 0O 0O 0 0 zent 0 0 0 0 101 Chapter 4 Mutual Exclusion Another process is put in the background waiting on semaphore 0 Then the semaphore set is removed with ipcrm The waiting instance of semop ends displaying the error code from semop semop i 130 p 0 amp 9962 iperm s 130 semop Identifier removed 102 Chapter 5 Signalling Events Processes can receive signals in order to respond to asynchronous requests from software or to unexpected hardware events There are three different programming interfaces for receiving signals you must select one and use it consistently throughout a program Many programs need access to time data for one of two purposes to produce timestamps so that data can be ordered by its time of origin and to define intervals so the program can
426. where e language is the two letter ISO 639 abbreviation for the language name e territory is the two uppercase letter ISO 3166 abbreviation for the territory name For a list of these abbreviations see the table in Appendix A ISO 3166 Country Names and Abbreviations 295 Chapter 14 Internationalizing Your Application 296 e encoding is the name of the character encoding mapping between numbers and characters For western languages this is typically the codeset such as 8859 1 or ASCII For Asian languages where an encoding may encode multiple codesets the encodings themselves have names such as UJIS or EUC these encodings are described later in this section Character Sets Codesets and Encodings on page 298 discusses codesets and encodings e modifiers are not actually part of the locale name definition they give more specific information about the desired localized behavior of an application For example under X11R5 or X11R6 a user can select an input method with modifiers To use the xwnmo Input Method server provided by Silicon Graphics for example add im _XWNM6O to the locale string No standards exist for this part of a locale string Language data is implementation specific databases for the language en English might contain British cultural data in England and American cultural data in the United States If other than the default settings are required the territory field may be used For exa
427. where catopen can find it see the XPG 4 Catalog Location on page 326 327 Chapter 14 Internationalizing Your Application 328 SVR4 MNLS Message Catalogs There are many ways to use strings from MNLS message catalogs You can get strings directly and then use them or you can use output routines that search catalogs Putting MNLS Strings Into a Catalog An MNLS catalog source file contains a list of strings separated by new lines For an empty string an empty line is used Strings are referenced by line number in the original source file Applications access the catalog by line number so it s very important not to change the line numbers of existing catalog entries This means that when you want to add a new string to an existing catalog source you should always append it to the end of the file if you put it in the middle of the file then you change the line number for subsequent strings The following tools can help you compile MNLS message catalogs exstr 1 Searches a C source file for literal strings and lists them or replaces them with MNLS function calls mkmsgs 1 Creates a message catalog for a particular locale converting source text lines to the form used by exstr srchtxt 1 Displays selected strings from a message catalog When a file of strings is ready to be compiled simply run mkmsgs and put the results in the directory usr libflocale localename LC_MESSAGES Using MNLS in Shell Scripts
428. where input is interpreted as romaji Latin characters and a mode where input is translated to kana 345 Chapter 14 Internationalizing Your Application 346 Furthermore both styles may operate simultaneously While an application is supporting implicit composition of certain characters other characters may be composable via explicit composition Not every keystroke produces a character even if the associated keysym normally implies character text The event to string translation routines figure out what result a given set of keystrokes should produce see Using XLookupString XwcLookupString and XmbLookupString in this section Character composition from the user s aspect is discussed in the compose 5 and composetable 5 reference pages Explicit Composition Explicit composition is requested when the user presses the Compose key and then types a key sequence that corresponds to the desired character For example to compose the character fi under some keymaps you might press the Compose key and then type n Note The xmodmap 1 reference page tells how to map the XK_Multi_key keysym onto whatever key you want to use as Compose Implicit Composition Implicit composition mimics many existing European typewriters that have dead keys keys that type a character but do not advance the carriage When a special dead key is struck the system attempts to compose a character using the next character struc
429. with SVR4 and POSIX are noted in the text of this section The Segment Mapping Function mmap The mmap function see the mmap 2 reference page creates shared or unshared segments of memory The syntax and most basic features of mmap are compatible with SVR4 and with POSIX 1003 1b A few features of mmap are unique to IRIX The mmap function performs many kinds of mappings based on six parameters The function prototype is void mmap void addr size_t len int prot int flags int fd off_t off The function returns the base address of a new segment or else 1 to indicate that no segment was created The size of the new segment is len rounded up to a page An attempt to access data beyond that point causes a SIGBUS signal Describing the Mapped Object Three of the mmap parameters describe the object to be mapped into memory which is the backing store of the new segment fa A file descriptor returned by open or by the POSIX defined function shm_open see the open 2 and shm_open 2 reference pages All mmap calls require a file descriptor to define the backing store for the mapped segment The descriptor can represent a file or it can be based on a pseudo file that represents kernel memory or a special device file Mapping Segments of Memory off The offset into the object represented by fd where the mapped data begins When fd describes a disk file off is an offset into the file When fd describes memory o
430. with condition variables are summarized in Table 11 10 Table 11 10 Functions for Using Condition Variables Function Purpose pthread_cond_wait 3P Wait on a condition variable pthread_cond_timedwait 3P Wait on a condition variable returning with an error after a time limit expires pthread_cond_signal 3P Signal that an awaited event has occurred releasing at least one waiting thread pthread_cond_broadcast 3P Signal that an awaited event has occurred releasing all waiting threads The pthread_cond_wait and pthread_cond_timedwait functions require two arguments a mutex that is owned by the calling thread and a condition variable The mutex is released and the wait begins When the event is signalled or the time limit expires the mutex is reacquired as if by a call to pthread_mutex_lock The POSIX standard explicitly warns that it is possible in some cases for a conditional wait to return early before the event has been signalled For this reason a conditional wait should always be coded in a loop that tests the shared resource for the needed status These principles are suggested in the code in Example 11 6 which is modelled after an example in the POSIX 1003 1c standard 231 Chapter 11 Thread Level Parallelism 232 Exa in in typ typ e typ o1 sta I I KY ele mple 11 6 Use of Condition Variables clude lt assert h gt clude lt pthread h gt e
431. y 3P Uninitialize a pthread_attr_t object pthread_create 3P Create a new thread based on an attribute object or with default attributes Creating Pthreads Initial Detach State After a thread has terminated it can be detached Detaching means that the pthreads library deletes its information about the thread possibly releasing some memory see Joining and Detaching on page 218 There are three ways to detach a thread e automatically when the thread terminates e explicitly by calling pthread_join e explicitly by calling pthread_detach You can use pthread_attr_setdetachstate to specify that a thread should be detached automatically when it terminates Do this when you know that the thread will not be detached by an explicit function call Initial Scheduling Priority and Policy Scheduling priorities and policies are described under Scheduling Pthreads on page 223 You can specify an initial scheduling policy by calling pthread_attr_setschedpolicy passing one of the policy constants SCHED_FIFO SCHED_RR or SCHED_OTHER You can specify an initial thread priority in a struct sched_param object in memory the structure is declared in sched h Set the desired priority in the sched_priority field Pass the structure to pthread_attr_setschedparam The pthread_attr_setinheritsched function is used to specify in the attribute object whether a new thread s scheduling policy and priority should be ta
432. ywhere An engraving is the image imprinted on a physical key These are contained in usr include X11 keysymdef h Keysyms represent the engravings on the actual keys but not their meanings The server s idea of the keysym table can be changed by clients and clients may receive KeyMap events when this remapping happens but such events don t happen often When a client receives a Key event it asks Xlib to use the keycode to index into its keysym table to find a list of keysyms This list is usually very short Most keys have only one or two engravings on them Using the state byte Xlib chooses a keysym from the list to find out what was engraved on the key the user pressed At this point the client can choose to act on the keysym itself if for instance it was a backspace or it can ask for a character string represented by the keysym or both Generating such a string is tricky it is discussed in Input Methods IMs below Details on X keyboard support can be found in X Window System Third Edition from Digital Press Details on input methods are also available in that book as well as in the Xlib Programming Manual Volume One Composed Characters There are two ways to compose characters that do not exist on a keyboard explicit and implicit It is common for an application to be modal and switch between the two For example Japanese input of kana is often done via implicit composition Users switch between a mode

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