Parallel Object Programming C++ User and Standard
Contents
1. Casting operator const char const operator std string const Extracts a substring void substring int start int end POPString amp sub Get length of POPString int Length const Returns a pointer to the char data char GetString Fig 3 5 The POPString class 3 4 2 Synchronization POP C provides the concurrent semantic for method invocations see section 2 4 As a consequence we can have several methods which are concurrently executed inside the same object If these methods try to access the same data attribute of the object this can lead to race conditions ans can require a way to synchronize the access to the share data This is a standard problem in concurrent system an POP C provide a standard solution to this problem thanks to the POPSynchronizer class Figure 3 6 shows the declaration of the POPSynchronizer class class POPSynchronizer public POPSynchronizer lock unlock raise wait Fig 3 6 The POPSynchronizer class The synchronizer is an object used for general synchronization of concurrent execution inside a parallel object Every synchronizer can handle a lock and a event Locks and events can be used independently of each other or not Calls to lock close the lock and calls to unlock open the lock A call to lock returns immediately if the lock is not closed by any other method Otherwise it will pause 20 User Manua the execution of th2. Bibliography Bibliography 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 W Allcock J Bester J Bresnahan A Chervenak L Liming S Meder and S Tuecke GridFTP Protocol Specification GGF GridFTP Working Group Document September 2002 http www globus org research papers htm K Czajkowski I Foster N Karonis C Kesselman S Martin W Smith and S Tuecke A resource management architecture for metacomputing systems In Proc IPPS SPDP 98 Workshop on Job Scheduling Strategies for Parallel Processing pages 62 82 1998 Foster and N Karonis A grid enabled mpi Message passing in heterogeneous distributed computing systems In Proc 1998 SC Conference November 1998 I Foster and C Kesselman Globus A metacomputing infrastructure toolkit Intl J Supercomputer Applications 11 2 115 128 1997 I Foster C Kesselman J Nick and S Tuecke Grid services for distributed system integration Computer 35 6 2002 Andrew Grimshaw Adam Ferrari Fritz Knabe and Marty Humphrey Legion An operating system for wide area computing IEEE Computer 32 5 29 37 May 1999 N Karonis B Toonen and I Foster MPICH G2 A grid enabled implementation of the message passing interface Journal of Parallel and Distributed Computing 2003 Kuonen P Nguyen T A Programming the grid with pop c Future Generation Computer Systems FGCS 23 1 23 30 January
3. tree vertorintl vectorint2 vectorx will launch the specific test runtests short launches all tests and only prints a reduced amount of messssages to show how the individual test passes You cannot give any parameter to this command 5 5 Start Stop POP C The installation tree provides a shell setup script It sets paths to the POP C binaries and library directories The most straightforward solution is to include a reference to setup script in the users login shell setup file like profile bashrc or cshrc The setup scripts respectively for C shells and Bourne shells are lt install dir gt etc popc user env csh and lt install dir gt etc popc user env sh Before executing any POP C application the runtime system job manager needs to be started It must be launched on every node of the POP Community by entering the command POPC_LOCATION sbin SXXpopc start and to stop the runtime system POPC_LOCATION sbin SXXpopc stop Command Line Syntax 41 Appendix Command Line Syntax L P P Compiling an application popce cxxmain object type cpp lt C preprocessor gt cxx lt compiler gt popcld linker popcdir lt path gt popcpp lt POP C parser gt verbose noclean other C options sources cxxmain Use standard C main ignore POP C initialization popc static Link with standard POP C libraries statically popc nolib Avoid standard POP C librarie
4. 5 1 4 Secure Mode 5 3 2 Compiling POP C tool 5 1 5 Virtual Mode 5 3 3 POP C Setup 5 1 6 Virtual Secure Mode 5 3 4 Files modified by the setup 5 2 Before Installing 5 4 Start Stop POP C 5 2 1 Prerequisites 5 5 Testing Installation 5 1 Introduction POP C can be used in two different ways e Standalone e POP Community both installations can run in several modes e Standard mode which is actually the most common mode e Secure mode where all communications are done using SSH tunneling e Virtual mode will be available in a future release e Combining mode Virtual Secure will be available in a future release Information concerning Virtual and Virtual Secure modes are not detailed in this document These modes will be available in the next releases of POP C and will be explained in details the User s Guide of these releases 5 1 1 Standalone To get started with POP C the easiest way it to install 1t on a single computer which is not connected to any other POP C nodes This way to use POP C is called Standalone It is useful to make some experiments to see how POP C can be used and how it runs But of course using POP C in this way does not allow you to increase the computing power of your machine 5 1 2 POP Community In the POP Community mode your computer can cooperate with other computers on which POP C is also installed This is the usual way to use POP C as it allows you to access the computing pow
5. POP C services POP C services Customized service for Globus for other toolkit implementation Globus Toolkit other toolkit toolkits Computational environment Fig 1 1 POP C system architecture The POP C runtime system consists of three layers the service layer the service abstractions layer and the programming layer The service layer is built to interface with lower level toolkits e g Globus and the operating system The essential service abstraction layer provides an abstract interface for the programming layer On top of the architecture is the programming layer which provides necessary support for developing distributed object oriented applications More details of the POP C runtime layers are given in a separate document 9 1 4 Structure of this Manual This manual has five chapters including this introduction The second chapter explains the POP C s programming model The third chapter describes the POP C programming syntax The fourth chapter explains how to compile and run POP C applications The fifth chapter shows how to compile and install the POP C tool Programmers interested in using POP C should read first chapters 2 3 and 4 System managers should read first chapter 5 and eventually chapters 2 and 4 Introduction and Background 1 5 Additional Informations More information can be found on the POP C web site which contains A quick tutorial to get started with POP C Sol
6. described in the document Advanced programming POP C User Manual 3 2 7 Usage of this in POP C In C the identifier this provides a pointer to the current object It can be use to access a method of the current object Example class toto public void aMethod void anotherMethod void toto anotherMethod this gt aMethod call aMethod on the current object 16 User Manua In this example the instruction this gt aMethod is strictly equivalent to the instruction aMethod In both cases aMethod is called on the current object Another usage of this is to pass a pointer on the current object to another method usually a method of another object Example class titi class toto public void setTiti titi t private BILLAR class titi public void aMethod void toto setTiti titi t void titi aMethod EGtO Es E setTiti this pass a pointer to the current object In POP C the usage of this is a little bit more tricky We have to consider two cases this is a pointer to an instance of a sequential class not a parallel class In this case the behavior is the same than in standard C e this is a pointer to an instance of a parallel class a parclass In this case the instructions this gt aMethod and aMethod User Manual 17 are not anymore strictly equivalent Indeed the inst
7. example In this example as parameters transferred to and from the remote object are of basic C types in this case int the POP C run time is able to marshall and demarshall them without any intervention of the programmer 3 2 6 Marshalling Sequential Objects When parameter are not of basic C type the programmer must indicate to the POP C run time how to marshal and demarshal them This is the case when parameters are instances of sequential classes This is why sequential classes these parameter are instances of must derived from the POPBase sequential class provided by the POP C environment The interface of the POPBase class is the following class POPBase public virtual void Serialize POPBuffer amp buf bool pack Programmer must implement in the derived sequential class the Serialize method which will be used by the POP C run time to marshal and demarshal parameters which are instances of this class 14 User Manua The method Serialize requires two arguments the buf argument that stores the marshaled data object and the flag pack which specifies if the method Serialize is called to marshal or to demarshal the data into or from the buffer buf The POPBuffer class available in the POP C environment provides a set of Pack UnPack methods for all basic C types type char bool int float Pack is used to marshal the data into buf and UnPack is used to demarshal the data from buf Below is the decl
8. execution in MB default 1024 If you are allowed to launch POP C applications in an other account than yours you can give the username as answer to the following question Which local user you want to use for running POP C jobs Note Each POP C job is in fact a process Under Unix Linux each process is owned from one specific user You can give the user under which the POP C jobs must run by giving here the name of the user Of course you must have the rights to run processes under the name you give here By pressing just lt return gt the user you are actually logged in will be used It is possible to launch a script which submit the job on the local machine The name of the 38 Installation Instructions script can be given as answer to the question Enter the script to submit jobs to the local system If a particular protocol is required you can give it by entering the communication pattern Communication pattern Note Communication pattern is a text string defining the protocol priority on binding the interface to the object server It can contain matching non or all and matching any wildcards For example given communication pattern socket 160 98 http If the remote object access point is socket 128 178 87 180 32427 http 128 178 87 180 8080 My0b3 the protocol to be used will be http If the remote object access point is socket 160 98 20 54 33478 http 16
9. method on the remote object is terminated This corresponds to the traditional method invocation e Asynchronous invocation the invocation returns immediately after sending the request to the remote object Asynchronous invocation is important to exploit the parallelism However as the caller does not wait the end of the execution of the called method no computing result is available This excludes asynchronous invocations from producing results Results can be actively returned to the caller object using a callback the caller To do so the called object must have a reference to the caller object This reference can be passed as an argument to the called method see figure 2 2 To learn how to pass this reference see to section 3 4 o Fig 2 2 Callback method returning value from an asynchronous call Object side semantics the semantics that affect the order of the execution of methods in the called parallel object o A mutex call is executed after completion of all calls previously arrived on the object gt A sequential call is executed after completion of all sequential and mutex calls previously arrived o gt A concurrent call can be executed concurrently time sharing with other concurrent or sequential calls except if mutex calls are pending or executing In the later case he is executed after completion of all mutex calls previously arrived In a nutshell different object side invocation semantics can be expressed
10. of a tar file with the following naming convention popc lt version subversion gt tgz You can download the tar file either From sourceforge http sourceforge net projects popcpp or e Directly from the website of the GridGroup who develops and maintains the tool POP C http gridgroup hefr ch popc doku php download Installation Instructions 35 From freash meat http freshmeat net projects pop c 5 3 Standard Installation This section describe how to install the standard POP C without any special option It s also possible to customize the installation Customized installation is explained in more detail in the document Advanced POP C User Manual 5 3 1 Preparing compilation After downloading the tar file you must decompress it tar C lt source dir gt zxf popc lt version subversion gt tgz Note You must check that you have R W access to the lt source dir gt Then go to lt source dir gt cd lt source dir gt If you want have a POP C with all default options you can now configure the compilation files by entering the following command on a Linux operating system configure and the following command on a MacOS operating system configure CPPFLAGS DARCH_MAC Default options are e lt install dir gt will be usr local popc even you defined another directory in POPC_LOCATION e POP C will run in Standard Mode By installing POP C in Standard mode either in Standalone o
11. the command popcc to compile POP C source code To compile the main program we use the following command popcc o main integer ph integer cc main cc It has to be noticed that we have to explicitly compile the declaration of the parallel class the file integer ph when in C we usually do not compile the declaration files h files This is a specificity of the POP C compiling process 4 2 2 Compiling the object code Use popcc with option object to generate the object code popcc object o integer obj integer ph integer cc Again we have to to explicitly compile the declaration of the parallel class One also can generate relocatable code files o files that can be linked using a C compiler As in the normal C compiling process this is done using the c option compile only along with the popcc command It has to be noted that all options available with the used C compiler are also available with the popcc compiler as these options are directly transmitted to the C compiler which will generate the final executable files see section 4 1 4 2 3 Running To execute a POP C application we need to generate the object map file which contains the list of all compiled parallel classes used by the application For each parallel class we have to indicate for which architecture the compilation has been done and the location of the executable file obj file With POP C it is possible to get this information by execut
12. 0 98 20 54 8080 My0b3 the protocol to be used will be socket If special runtime environment variables are required you can give them now Give the name of the variable then the system will ask the value After giving the value the system will again ask for a variable name until you press lt return gt without giving a name If no special environment variable are required by the POP C application just enter lt return gt to the question Enter variable name In other case give the name and the procedure will ask the value Enter variable value The procedure ask for a new variable as long as you define any If you do not need to define more variable just press lt return gt Note On MAC system the default network interface is not automatically detected It is necessary to enter the variable name POPC_IFACE and as value either the interface name or the IP address Because POP C uses the network it will use a communication port The default port is 2711 If for some reason you want to change it you can do it here Note that in case a firewall is installed between the nodes the port must be open on this firewall Enter the service port 2711 The domain name is also asked by POP C Thus this is not mandatory Enter the domain name Installation Instructions 39 POP C uses lt temp dir gt to store informations during execution Default directory is tmp but you are can change it here Note You must
13. 2007 Tuan Anh Nguyen An Object oriented model for adaptive high performance computing on the computational Grid PhD thesis Swiss Federal Institute of Technology Lausanne 2004 Object Management Group Framingham Massachusetts The Common Object Request Broker Architecture and Specification Version 2 6 December 2001 A Roy I Foster W Gropp N Karonis V Sander and B Toonen MPICH GQ Qualityof service for message passing programs In Proc of the IEEE ACM SC2000 Conference November 2000 H Stockinger A Samar B Allcock I Foster K Holtman and B Tierney File and object replication in data grids In 10th IEEE Symposium on High Performance and Distributed Computing HPDC2001 2001 San Francisco California Weiqin Tong Jingbo Ding and Lizhi Cai A parallel programming environment on grid In International Conference on Computational Science 2003 pages 225 234 2003 V Welch F Siebenlist I Foster J Bresnahan K Czajkowski J Gawor C Kesselman S Meder L Pearlman and S Tuecke Security for grid services In IEEE Press editor Twelfth International Symposium on High Performance Distributed Computing HPDC 12 2003 Tiffani L Williams and Rebecca J Parsons The heterogeneous bulk synchronous parallel model Lecture Notes in Computer Science 1800 2000
14. actually reactivated The typical use of locks is to implement critical sections when several methods can modify at the same time a shared attribute The typical use of events is to synchronize a producer consumer situation Figure 3 8 presents an example of usage of event with the POPSynchronizer class User Manual 21 parclass Example2 private int cakeCount boolean proceed Synchronizer syn public void producer int count cakeCount count syn lock proceed true syn raise syn unlock void consumer syn lock if proceed wait syn unlock can use cakeCount from now on time eee 7 fe SE e da A ES O Fig 3 9 Example with one producer and two consumers using the parallel class of figure 3 8 3 4 3 Exceptions Exceptions are a powerful way provided by C to handle errors Exceptions allow the programmer to filter errors trough several calling stacks When an error is detected inside a method an exception can be thrown and can be caught somewhere else in the calling stack 22 User Manual EE E LL Y try Example method E o2 method 7 int x catch int x throw x handle exception wists Fig 3 10 Exception handling example The implementation of exceptions in non distributed applications where all components run within the same memory address space is rather straightforward The compiler just need to pa
15. also contains the compiled files during the installation This directory should hold roughly 250 MB all sources and compiled files It can be erased after the installation We call this directory lt source dir gt in the present document There is no default value for the name of this directory e In which directory the POP C runtime will be installed It should hold less than 100 MB This directory is necessary on every computer where POP C is installed The default name is usr local popc We call this directory lt install dir gt in the present document e In which directory will be stored temporary files This directory contains the temporary files produced by POP C when running The default name for this directory is tmp This directory will be asked during the installation process By convention we call this directory lt temp dir gt in the present document In which mode will POP C be installed Standard mode this is the default Secure mode Virtual mode Virtual Secure mode Recommendation To ease the installation and the usage of POP C it is highly recommended to define an environment variable named POPC_LOCATION which contains the name of lt install dir gt Because this variable will be constantly uses by POP C the best way is to define it in your bashrc file or its equivalent distribution dependent 5 2 3 Downloading the POP C Distribution POP C is distributed in form
16. amming model by adding the minimum necessary functionality to allow for an easy development of coarse grain distributed high performance applications When the object oriented paradigm has unified the concept of module and type to create the new concept of class the POP model unifies the concept of class with the concept of task or process This is realized by adding to traditional sequential classes a new type of class the parallel class By instantiating parallel classes we are able to create a new category of objects we will call parallel objects in the rest of this document Parallel objects are objects that can be remotely executed They coexist and cooperate with 2 Introduction and Background traditional sequential objects during the application execution Parallel objects keep advantages of object orientation such as data encapsulation inheritance and polymorphism and adds new properties to objects such as Distributed shareable objects Dynamic and transparent object allocation Various method invocation semantics 1 3 System Overview Although the POP C programming system focuses on an object oriented programming model it also includes a runtime system which provides the necessary services to run POP C applications over distributed environments An overview of the POP C system architecture is illustrated in figure 1 1 POP C programming programming model language and compiler POP C essential service abstractions
17. aration of the POPBuf fer class class POPBuffer public Type is any basic C type void Pack const Type data int n void UnPack Type data int n e class POPMemSpool public void Alloc int size For the method Pack the parameter data contains the address of the data to marshal into buf when is the case of the UnPack method the same parameter data contains the address of the data into which the data received in buf must be demarshaled Pack Unpack methods offer the possibility to marshal demrashal several data of type Type in one call The n parameter contains the number of data of type Type to marshall demarshall This feature is especially useful when passing arrays of objects Figure 3 3 shows an example of marshalling demarshalling of the Speed sequential class User Manual 15 class Speed public POPBase public Speed virtual void Serialize POPBuffer amp buf bool pack float val int count void Speed Serialize POPBuffer amp buf bool pack if pack buf Pack amp count 1 buf Pack val count else if val NULL delete val buf UnPack amp count 1 if count gt 0 val new float count buf UnPack val count else val NULL parclass Engine void accelerate const Speed data Fig 3 3 Marshalling demarshalling of the Speed class POP C also offers other more sophisticated ways to transfer data to remote objects which are
18. atic features result in a dynamic usage of computational resources and gives to the applications the ability to adapt to changes in both the environment and the user behavior The creation of POP C parallel objects is driven by high level requirements on the resources where the object should lie see section 2 6 If the programmer specifies these requirements they are taken into account by the runtime system for the transparent object allocation The allocation process consists of three phases first the system finds a suitable resource where the object will lie then the object code is transmitted and launched on that resource and finally the corresponding local interface is created to be connected to the remote object All this process is fully transparent to the programmer 2 6 Requirement driven Parallel Objects Parallel processing is increasingly being done using distributed systems with a strong tendency towards web and global computing Efficient extraction of high performance from highly heterogeneous and dynamic distributed environments is a challenging task POP C was conceived under the belief that for such environments high performance can only be obtained if the two following conditions are satisfied 8 Parallel Object Model e The application should be able to adapt to the environment e The programming environment should somehow enables objects to describe their resource requirements POP C allows the programmer to inte
19. cating a resource satisfying the object description resource discovery transmitting and executing the object code establishing the communication transmitting the constructor arguments and finally invoking the corresponding object constructor Failures on the object creation will raise an exception to the caller See section 3 4 3 to learn about the POP C exception mechanism User Manual 11 As a parallel object can be accessible concurrently from multiple distributed locations shared object destroying a parallel object should be carried out only if there is no more reference to this object POP C manages parallel objects life time by an internal reference counter A null counter value will cause the object to be physically destroyed Syntactically the creation and the destruction of a parallel object are identical to those of C A parallel object can be implicitly created by declaring a variable of this parallel class or by using the standard C new operator 3 2 3 Parallel Class Method Invocations Like sequential classes parallel classes contain methods and attributes Method can be public or private while attribute must be either protected or private For each method the programmer can define the invocation semantics by placing appropriated keywords before methods declaration These semantics described in section 2 4 are specified for each side of the call Caller side e syne Synchronous invocation This is the defa
20. ction 3 4 3 3 2 5 Data Marshalling When calling remote methods the arguments or parameters of the call must be transferred to the object being called the same happens for returned values In order to operate with different memory spaces and different architectures data must be marshaled or serialized into a standard format prior to be send to remote objects All data passed are marshaled at the caller side and demarshaled or deserialized at the callee side Only input arguments are transferred from the caller to the callee object and in case of a synchronous method invocation only output arguments are transferred back to the caller User Manual 13 In the current implementation of POP C the following rules are applied e If the method is asynchronous arguments must be input only If the method is synchronous e Constant and passing by value arguments are input only gt Other arguments are considered as both input and output gt The value returned by the method is an output only parameter POP C transparently marshals demarshals all arguments of basic C types int float char Figure 3 2 shows an example of the declaration of a parallel class Toto containing the methods void set int i andint get parclass Toto void set int i int get main program int main int argc char argv Toto x x set 10 printf Tote value is d n x get Fig 3 2 Simple parallel class
21. d environments such as GRID P2P or Cloud infrastructures is a challenging task This statement remains true even if we consider researches that have focused on enabling these types of infrastructures for scientific computing such as resource management and discovery 4 6 2 service architecture 5 security 14 and data management 1 12 Efforts to port traditional programming tools such as MPI 3 11 7 or BSP 13 15 also had some success These tools allow programmers to run their existing parallel applications on large heterogenous distributed environments However efficient exploitation of performance regarding the heterogeneity still needs to be manually controlled and tuned by programmers POP C is an implementation as an extension of the C programming language 8 of the POP Parallel Object Programing model first introduced by Dr Tuan Anh Nguyen in his PhD thesis 9 The POP model is based on the very simple idea that objects are suitable structures to distribute data and executable codes over heterogeneous distributed hardware and to make them interact between each other Inspired by CORBA 10 and C the POP C programming language extends C by adding a new type of parallel object allowing to run C objects in distributed environments With POP C programming efficents distributed applications is as simple as writing a C programs 1 2 The POP Model The POP model extends the traditional object oriented progr
22. der To compile any class in the chain we needs the parallel classe which is directly after the one we are compiling in the chain of dependency When compiling a parallel class without generating the executable code option c the POP C compiler generates a relocatable object file called className stub o In addition the POP C compiler has an option called parclass nobroker which allows to generate relocatable code without internal POP C classes The way to compile a POP C application with the dependencies illustrated on figure 4 2 is shown in figure 4 3 popce object o myobj4 obj myobj4 myobj4 cc popce c parclass nobroker myob34 ph popce object o myob33 ob3 myobj3 ph myobj3 cc myobj4 stub o popce c parclass nobroker myob33 ph popce object o myob32 ob3 myobj2 ph myobj2 cc myob33 stub o popce c parclass nobroker myobj2 ph popce object o myob31 ob3 myobjl ph myobjl cc myobj2 stub o popce o main main cc myob31 ph myobjl cc myobj2 stub o Fig 4 3 How to compile applications with dependencies The source code of an example can be found in the examples directory of the POP C distribution and on the POP C web site http gridgroup hefr ch popc Installation Instructions 31 CHAPTER Installation Instructions 5 1 Introduction 5 2 2 Location of the Files 5 1 1 Standalone 5 2 3 Download the Distribution 5 1 2 POP Community 5 3 Standard Installation 5 1 3 Standard Mode 5 3 1 Preparing compilation
23. duction and ACW Or Oia aiii 1 1 1 TOTO TOIRT a EAA E II E A 1 1 2 A eae enh eae E us et aces nein EE R A EEE nies ee EE EAEri 1 1 3 A a E ro E R EE ET EA E 2 1 4 Structure of this Manual air DRA 2 1 5 Additional IMA ri 3 2 Parallel Object Mod 4 2 1 OOOO e AAA AAA 4 2 2 Parallel Obrero Slebentniaaiusn einai saiantetedSacaniebanursebnace 4 2 3 Shareable Parallel Cells ia 5 2 4 Methods Invocation Semantics ri 5 2 5 Parallel Object FING CAU OM ia 7 2 6 Requirement driven Parallel Objects ccisssiscccasssssscassstdexnsiadncadnssadccandasuccenissaedtainsedavsdsatevandions 7 Se Mi 9 3 1 Tatr od ctio D ssie e E RE E TN 9 3 2 Patallel ODJ CtS snno nona i a EA en ec ee 10 3 2 1 Parallel Clas SES riences ere E A R TE 10 3 2 2 Creation and Destruction jesacerarvsudaxeunatanncantecieenceterencantaxeonacueiearcacracuuntdeenenteeuceuomncumucnneons 10 3 2 3 Parallel Class Method Invocations ri in 11 324 A A 12 3 2 5 Data Ma II d 12 3 2 6 Marshalling Sequential Obie sii da 14 2 Usage of this POE rirni amram ee 15 3 3 Object La VOD errire ka ees is 17 3 3 1 The Ea MIN ais 17 3 3 2 Clasy Unique Inti ii 18 3 4 POP C F Standard LiIDTATY on 18 34 1 The POPSErINg A A 18 A E E E EAEN AEE A EAA EEE 19 34 3 Exceptions ssia E O ceo eae 21 3 5 Programming Explicit 23 o E EE EE A TEE E A A 23 3 5 2 O 24 3 MA ai 2 3 6 A E E EE E cers AR E A E 26 A Compiling and RUNIDO sissies aa E E E EERE 28 4 1 Compras 28 4 2 Example compiling the In
24. e calling method until anther method releases the lock Calls to unlock will reactivate one and just one paused call to lock The reactivated method will then succeed closing the lock and the call to lock will eventually return When creating a synchronizer by default the lock is open A special constructor is provided to create it with the lock already closed Figure 3 7 shows an example of usage of locks with the POPSynchronizer class parclass Examplel private POPSynchronizer syn int counter public int getNext syn lock int r counter syn unlock return r Fig 3 7 Using locks with the POPSynchronizer Class Event can be waited and raised Calls to wait cause the calling thread to pause its execution until another method triggers the event by calling raise If the waiting method possess the lock it will automatically release the lock before waiting for the event When the even occurs is raised the waiting method will try to re acquire the lock that it has previously released before returning control to the caller Many methods can wait for the same event When a method calls raise all waiting for event methods are reactivated at once If the lock was closed when the wait was called the reactivated methods will close the lock again before returning from the wait call If other methods calls wait with the lock closed all will wait the lock to be re open before they are
25. ement specifier the keyword corresponding to resNum or resString The lbound term is only used in non strict object descriptions to specify the lower bound of the acceptable resource requirements In the resource string the different options must be separate with one blank The priority of the parameter is position dependant the first parameter having the highest priority and the last one having the lowest The current implementation allows indicating resources requirement in terms of Computing power in Mflops keyword power Memory size in MB keyword memory Bandwidth in Mb s keyword network Location host name or IP address keyword url Protocol socket or http keyword protocol Data encoding raw xdr raw zlib or xdr zlib keyword encoding An example of parallel class declaration is given in the figure 3 1 In this example the constructor for the parallel object Bird requires a computing power of P Mflops a desired memory space of 100MB having 60MB is acceptable and the communication protocol is socket or HTTP socket having higher priority parclass Bird public Bird float P od power P od memory 100 60 od protocol socket http Fig 3 1 Object descriptor example Object descriptors are used by the POP C runtime system to find a suitable resource for the parallel object If no suitable resource is found to execute the objet then an exception is raised see se
26. ent implementation of POP C Some of these restrictions are expected to disappear in the future while others are simply due to the nature of parallel programming and the impossibility for parallel objects to share a common memory For the current version 2 0 the limitations are A parallel class cannot contain public attributes A parallel class cannot contain a class attribute static A parallel class cannot be template A parallel class cannot contain programmer defined operators An asynchronous method cannot return a value and cannot have output parameters Global variables exist only in the scope of parallel objects pack scope User Manual 27 A parallel object method cannot return a memory address Sequential classes used as parameter must be derived from POPBase and the programmer must implement the Serialize method Effective parameters of methods of parallel classes which are instances of sequential classes must have exactly the same dynamic type as in the method declaration an object of a derived class cannot be used as effective argument Only scalar parallel object and POPException exception type are propagated as is All other exceptions are converted to POPException with the unknown code Exceptions raised in an asynchronous method are not propagated to caller They abort cleanly the application 28 Compiling and Running CHAPTER 4 Compiling and Running SEDA PQP 4 1 Compilation 4 2 3 Runnin
27. er of all the machines of the POP Community 32 Installation Instructions To be able to cooperate with other computers your computer must know at least one computer which is already part of a POP Community you want to be integrated in A computer that is known by your machine is called a direct neighbor or more simply a neighbor Several computers can be neighbor of your computer It is not necessary that all computers are neighbors of all other computers present in the POP Community Indeed the POP C run time has mechanisms enabling usage of computer which are not a direct neighbor but connected to other machines which are part of the same community Figure 5 1 shows an example of a POP Community The mains restriction is that the community must be a connected graph a POP Community example your neighbour computer 1 your computer other computers inside POP Community your neighbour computer 3 your neighbour computer 2 Fig 5 1 Example of a POP Community One can also create a POP Community by being the first computer in the community If another computer wants to cooperate with yours POP C must be configured on this computer so that it see your computer as a neighbor Nothing special must be done on your computer to cooperate with the new coming computer It is in charge of the computer that wants to cooperate with you to declare you as a neighbor It has to be noted taht we use the expression POP Community and n
28. g 4 2 Example compiling the Integer 4 3 Compiling a POP C program program containing several parallel 4 2 1 Compiling classes with dependencies 4 2 2 Compile the Object Code 4 1 Compilation The POP C compiling process generates a main executable file and several object executables files The main executable file provides a starting point for launching the application and object executables files are loaded and started by the POP C runtime system whenever a parallel object is created The compilation process is illustrated in figure 4 1 PopC parser PopC compiler main and object binaries C compiler PopC service libraries Fig 4 1 POP C compilation process The POP C compiler contains a parser which translates the POP C source code files into pure ANSI C source code files Service libraries provide APIs that manages communication resource discovery object allocation etc At the end of the compiling an ANSI C compiler generates binary executables files 4 2 Example compiling the Integer program In this section we illustrate the POP C compiling process by describing how to compile the simple program Integer presented in section 3 5 4 2 1 Compiling We have to generate two executables the main program main and the parallel classes Compiling and Running 29 executable files integer ob3 By convention these executable files have the extension ob POP C provides
29. grate resource requirements into parallel objects under the form of high level resource descriptions Each parallel object can be associated with an object description that describe the characteristics of the resources needed to execute this object Many different resources requirement can be expressed such as e Resource host name low level description mainly used to develop system services e The maximum computing power that the object needs expressed in Mflops The maximum amount of memory that the parallel object consumes e The expected communication bandwidth and latency An object description can contain several items Each item corresponds to a type of characteristics of the desired resource The item is classified into two types strict item and non strict item A strict item means that the designated requirement must be fully satisfied If no satisfying resource is available the allocation of parallel object fails Non strict items on the other hand give the system more freedom in selecting a resource Resource that partially match the requirements are acceptable although a full qualification resource is preferable For example a certain object has a preferred performance 150MFlops although 100MFlops is acceptable non strict item but it need memory storage of at least 128MB strict item The evaluation of object descriptions is done during the parallel object creation The programmer can provide an object description w
30. have read write access to this directory Enter the temporary directory for intermediate results Once this is given the configuration process will inform you which parameters you must have to add in your session script Just copy the three lines in your bashrc or equivalent 5 3 4 Files modified by the setup The setup process changes the content of the following files S POPC_LOCATION etc jobmgr conf POPC_LOCATION etc popc runtime env sh POPC_LOCATION etc service map SPOPC_LOCATION sbin SXXpopc 5 4 Testing Installation Several test applications which permit to test the most important features of POP C are delivered with the distribution These applications are located in the POPC_LOCATION test directory Two scripts are available to launch the tests runtests and runtests_short With runtests you can launch all tests at once or each test individually This command will display the compilation messages of the test before it runs the tests A little help is displayed if you launch runtests without parameter runtests usage runtests lt parameter gt with parameter h or help displays this help message all launches all tests at once one of the following test name barrier callback classparam constparam exception heritage heritageparaml heritageparam2 jobManager matrixNB method param passparam serialize vect 40 Installation Instructions structparam templateparam
31. ically assigning suitable resources to objects POP C also offers various mechanisms to specify different ways to do method invocations Parallel objects have all the properties of traditional objects plus the following ones e Parallel objects are shareable References to parallel objects can be passed to any other parallel object This property is described in section 2 3 e Syntactically method invocations on parallel objects are identical to method invocations on traditional sequential objects However parallel objects support various method invocation semantics synchronous asynchronous sequential mutex and concurrent These semantics are explained in section 2 4 e Parallel objects can be located on remote resources in separate address spaces Parallel objects allocations are transparent to the programmer The object allocation is Parallel Object Model 5 presented in section 2 5 e Each parallel object has the ability to dynamically describe its resource requirement when created This feature is discussed in detail in section 2 6 As for traditional objects parallel objects are active only when they execute a method non active distributed object semantic Communication between parallel objects are realized only through remote methods invocations 2 3 Shareable Parallel Objects Parallel objects are shareable This means that the reference of a parallel object can be shared by several other parallel objects Sharing references
32. ime environment variables P P The following environment variables affect or change the default behaviors of the POP C runtime To ensure that the environment of all running objects these variables should all be set during the installation make install or in the environment setup script popc runtime env POPC_LOCATION Location of installed POP C directory POPC _PLUGIN_LOCATION Location where additional communication and data encoding lugins can be found POPC_JOBSERVICE The access point of the POP C job manager service If the POP C job manager does not run on the local machine where the user start the application the user must explicitly specify this information Default value socket localhost 2711 POPC_HOST Full qualified host name of local node This host name will be interpreted POPC_IP IP of local node Only used if POPC_HOST is not defined POPC_IFACE If POPC_HOST and POPC_IP are not set use this interface to determine the node IP If not set the default gateway interface is used POPC_PLATFORM The platform name of the local host By default the following format is used lt cpu 1d gt lt os vendor gt lt os name gt POPC_MPIRUN The mpirun command to start POP C MPI objects not documented in this manual POPC_JOB_EXEC Script used by the job manager to submit a job to local system POPC_DEBUG Print all debug information 44
33. in terms of atomicity and execution order The mutex invocation semantics guarantees the global order and the atomicity of all method calls The sequential invocation semantics guarantees only the execution order of sequential methods Concurrent invocation semantics guarantees neither the order nor the atomicity Figure 2 3 illustrates different method invocation semantics Sequential invocation Seq1 is Parallel Object Model 7 served immediately running concurrently with Conc1 Although the sequential invocation Seq2 arrives before the concurrent invocation Conc2 it is delayed due to the current execution of Seql no order between concurrent and sequential invocations When the mutex invocation Mutex1 arrives it has to wait for other running methods to finish During this waiting it also blocks other invocation requests arriving afterward Conc3 until the mutex invocation request completes its execution atomicity and barrier time EXT CIZE Fig 2 3 Example of different invocation requests 2 5 Parallel Object Allocation The first step to allocate a new object is the selection of an adequate placeholder The second step is the object creation itself Similarly when an object is no longer in use it must be destroyed in order to release the resources it is occupying in its placeholder The POP C runtime system provides automatic placeholder selection object allocation and object destruction This autom
34. ing parallel classes The declaration of a parallel class begins with the keyword parclass stands for parallel class followed by the class name and the optional list of derived parallel classes separated by commas parclass ExampleClass methods and attributes or parclass ExampleClass BaseClassl BaseClass2 methods and attributes As in the C language multiple inheritance and polymorphism are supported in POP C A parallel class can be a stand alone class or it can be derived from other parallel classes Some methods of a parallel class can be declared as overridable virtual methods Parallel classes are very similar to standard C classes Nevertheless same restrictions applied to parallel classes e All data attributes must be protected or private e The objects do not access any global variable e Programmer defined operators are not allowed e There are no methods that return memory address references e A parallel class can only derived from other parallel classes These restrictions are not a major issue in object oriented programming and in some cases they can improve the legibility and the clearness of programs These restrictions can be mostly worked around using accessors get and set methods and by encapsulating global data and shared memory address variables into other parallel objects 3 2 2 Creation and Destruction The object creation process consists of several steps lo
35. ing the object executable file with the option 1istlong Example for the Integer parallel class integer obj listlong This will display the following information Integer i686 pc Linux home myuser popc test integer integer obj To generate the object map file we simply redirect the output to the object map file integer obj listlong gt obj map The object map file must contain all mappings between object names platforms and the executable files locations We can now run the program using the command popcrun 30 Compiling and Running popcrun obj map main 4 3 Compiling a POP C program containing several parallel classes with dependencies The compilation is a little bit more difficult for more complex applications using several different parallel classes This is the case for example when the main program calls methods from objects of different parallel classes or when there is a chain of dependencies between the main program and several parallel classes as illustrated on figure 4 2 main myobj1 myobj2 myobj3 myobj4 Fig 4 2 Parallel classes with dependencies Since each class contains some internal POP C classes such as the interface or the broker classes the compilation must avoid to create multiple definitions of these classes An easy way to avoid this is to begin the compilation with the last class of the chain the class myob 4 on figure 4 2 and then to compile each parallel class in reverse or
36. ing when an exception derived from std exception C class has been defined by the programmer and a message has been associated with this exception As the exception cannot be catch by the caller and as the exception is transformed to POPException type this message is lost and will never be displayed To overcome this problem the POP C runt time behaves in such a way when a exception derived from std exception is thrown in a remote method in both cases asynchronous and synchronous methods Before giving back the control to the remote caller or the POP C run time the following User Manual 23 message is displayed on stdout POP C Warning Exception TexteOfException raised in method NameOfMethod of class NameOfClass Besides the exceptions defined by programmers POP C uses exceptions of type POPException to notify the user about the following system failure e Parallel object creation fails It can happen due to the unavailability of suitable resources an internal error on POP C services or the failures on executing the corresponding object code e Parallel object method invocation fails This can be due to the network failure the remote resource down or any other causes The interface of POPException is presented below class POPException public const POPString Extra const int Code const void Print const F The Code method returns the corresponding error code of the exception the Extra me
37. ith each object constructor The object descriptions can be parametrized by the arguments of the constructor Object descriptions are used by the runtime system to select an appropriate resource for the object The syntax of object descriptions is presented on section 3 2 4 User Manual 9 CHAPTER User Manual POP 3 1 Introduction 3 3 2 Class Unique Identifier 3 2 Parallel Objects 3 4 The POP C standard Library 3 2 1 Parallel Classes 3 4 1 The POPString class 3 2 2 Creation and Destruction 3 4 2 Synchronization 3 2 3 Parallel Class Method Invocations 3 4 3 Exceptions 3 2 4 Object Description 3 5 Programming example 3 2 5 Data Marshalling 3 5 1 Integer ph 3 2 6 Marshalling Sequential Objects 3 5 2 Integer cc 3 2 7 Usage of this in POP C 3 5 3 main cc 3 3 Object Layout 3 6 Limitations 3 3 1 The pack directive 3 1 Introduction The POP model see chapter 2 is a suitable programming model for large heterogenous distributed environments but it should also remain as close as possible to traditional object oriented programming Parallel objects of the POP model generalize sequential objects keeping the good properties of object oriented programming data encapsulation inheritance polymorphism and add new properties The POP C language is an extension of C programming language implementing the POP model Its syntax remains as close as possible to standard C so that C programmers can easily learn it and exis
38. ject o1 Lines 12 15 illustrate how to handle exceptions in POP C using the keyword pair try and catch Although o1 and o2 are distributed objects the way to handle the remote exceptions is similar to C see section 3 4 for details Figure 3 14 shows the execution of Integer Add method on line 4 in figure 4 3 of the example The system consists of three running processes the main object ol and object 02 The main is started by the user Objects ol and 02 are created by main Object 02 and the main program run on the same machine although they are in two separate memory address spaces object ol runs on a remote machine The main invokes the o1 Add with the interface 02 as an argument Object ol will then connect to 02 automatically and invoke the method 02 Get to get the value and to add this value to its local attribute data POP C system manages all object interactions in a transparent manner to the user 26 User Manua include integer ph int main int argc char argv try Integer o1 100 80 o2 localhost ol Set 1 o2 Set 2 ol Add 02 printf Value Sd n ol Get catch POPException e printf Object creation failure n e gt Print return 1 return 0 0 J0 OFRWNE Oo Fig 3 13 The file main cc CS sas user workstation Fig 3 14 Illustration of the execution of the Interger example 3 6 Limitations There are several limitations to the curr
39. lementation of the parallel class Integer is shown in figure 3 12 This implementation does not contain the invocation semantics and looks similar to a pure C code except at line 18 where a pack directive is provided indicating to the POP C compiler to store the executable code of the Integer parallel class in a separate file see section 3 3 for the pack directive User Manual 25 include integer ph Integer Integer int wanted int minp Integer Integer POPString machine void Integer Set int val data val 2 00 N ao Ui a GQ NP int Integer Get return data void Integer Add Integer amp other data other Get 10 11 12 L3 14 LO 16 L 18 pack Integer Fig 3 12 The file integer cc 3 5 3 main cc The main POP C program shown in figure 3 13 looks exactly as a pure C program Two parallel objects of type Integer o1 and o2 are created line 6 The object o1 asks for a resource with a desired performance of 100MFlops although the minimum acceptable performance is 80MFlops The object o2 explicitly specifies the resource to use to run o2 In this case the localhost computer After the object creations the invocations to methods Set and Add are performed line 7 9 The invocation of Add method shows an interesting property of POP C the object 02 is passed from the main program to the remote method Add of the parallel ob
40. llation Manual which will be released soon 5 1 6 Virtual Secure mode The most secure mode is made by combining the Secure Mode and the Virtual Mode More information about the virtual secure mode are given in the manual POP C Virtual Secure User and Installation Manual which will be released soon 5 2 Before installing POP C has is built on top of several widely known software packages and therefore has some prerequisites which are described in the next sub sections 5 2 1 Prerequisites Before trying to install and run POP C some mandatory packages must be installed The mandatory packages are e A standard C compiler g e the zlib devel package Optional packages are e the GNU Bison the Globus Toolkit 1 The name of the package is distribution dependent For example the zlib devel package is named on Fedora red hat based zlib devel on Ubuntu debian based zlib1g dev 2 This package is only necessary for those who wants to modify the POP C tool 3 This package is only necessary if you want to install POP C over Globus This installation is not described in the present document 34 Installation Instructions 5 2 2 Location of the Files Before installing POP C you have to decide about files locations e In which directory the source files will be downloaded This directory will be the root of the directory tree where you will download all the source files of POP C It will
41. n Parallel Object Programming C User and Standard Installation Manual Y SA QP Nu The POP C Team Grid amp Cloud Computing Group http gridgroup hefr ch Software Version 2 0 Manual Version 2 0 a i A University of Applied Sciences of Western Switzerland Fribourg Parallel Object Programming C User and Installation Manual Manual version 2 0a Copyright c 2005 2011 Grid and Cloud Computing Group University of Applied Science of Western Switzerland Fribourg Boulevard de P rolles 80 CP 32 CH 1705 Fribourg Switzerland http gridgroup hefr ch Permission is granted to copy distribute or modify this document under the terms of the GNU Free Documentation License published by the Free Software Foundation POP C is free software it can be redistributed or modified under the terms of the GNU Lesser General Public License LGPL as published by the Free Software Foundation It is distributed in the hope that it will be useful but without any warranty See the GNU General Public License for more details LGPLv3 This work was partially funded by the CoreGRID Network of Excellence in the European Commission s 6th Framework Program and by the University of Applied Sciences of Western Switzerland of Fribourg The POP C Team Pierre Kuonen Tuan Anh Nguyen Jean Fran ois Roche Valentin Cl ment David Zanella Marcelo Pasin Laurent Winkler Nicolas Brasey Content 1 Intro
42. n in Standalone or POP Community mode The first question you will have to answer is DO YOU WANT TO MAKE A SIMPLE INSTALLATION y n By answering y your POP C installation will be automatically installed in Standalone mode No more question will be asked and all default values will be used This is the simplest way to install POP C for the first time to do some tests If you need to change the parameter values you can later launch again make install and answer n to this question Note instead launching make install again you can also launch the script pope_setup This will be explained later in this document By answering n you can parameter POP C in a more fine way You also give the necessary informations to be part of an existing POP Community Note if you answer to all the other questions with a lt return gt the effect will be exactly the same as making a simple installation We have now to configure POP C services and generate POP C startup scripts The questions asked to do this are explained below POP C runtime environment assumes the resource topology is a graph Each node can join the environment by register itself to other nodes its neighbour hosts If you want to deploy POP C services at your site you can select one or several machines to be your Installation Instructions 37 neighbor nodes Enter the full qualified neighbour host name or IP address You can give here an IP address or a name
43. n of one or several parallel classes Programmers must indicate to the POP C compiler which parallel classes to store in which executable files This is done by inserting the pack directive in the source file of the implementation of the parallel classes cc file Figure 3 4 shows an fragment of the implementation of a Stack parallel class At the end of this file we have inserted a pack directive which indicates to the compiler that he must store the executable code of classes Stack Queue and List in the same executable file Stack Stack Stack pushile A Stack pop pack Stack Queue List Fig 3 4 Packing objects into an executable file This does not prevent the programmer to put if desired the source code of the parallel 18 User Manua classes Stack Queue and List in separated source code files The only rule to follow is For a given parallel class among the source files passed to the POP C compiler exactly one source file must contain the pack directive for this parallel class Usually one put each parallel class in a separate executable files As a consequence the source file of a parallel class is usually terminated by the pack ParClassName directive 3 3 2 Class Unique Identifier For a given program the C compiler assigns a unique class identifier to each class of the program As the POP C compiler generates several C programs from a unique POP C prog
44. of a machine which is running POP C neighbor machine Then your machine will enter in an existing POP Community and cooperate with all machines of the same POP Community If you give neither an IP address nor a name of a machine running POP C your machine will be considered as the first in a POP Community This question will appear as long as you give an IP address or a name of a neighbour machine Note do not define your computer as neighbour POP C will hang if you do this The script will inform you about this but will allow you to do it POP C needs to know how many processor are available on your system Enter number of processors available default 1 If you intend to run POP C service on a front end of a cluster this can be the number of nodes inside that cluster A core in a multi core processor is not considered as a single processor The system ask you now the number of jobs tha can be submitted to your local machine Enter the maximum number of POP C jobs that can run concurrently default 100 Note this is POP C application dependent Take care that each parallel object is a real Unix Linux process each parallel object is a POP C job So this value has to been big enough for all parallel objects which will run on this local machine You may not want to give all memory available for POP C applications so you can give the amount of memory you will give in MB Enter the available RAM for job
45. of parallel objects are useful in many cases For example figure 2 1 illustrates a scenario of using shared parallel objects input and output parallel objects are shareable among worker objects A worker gets work units from input which is located on the data server performs the computation and stores the results in the output located at the user workstation The results from different worker objects can be automatically synthesized and visualized inside output object To share the reference of a parallel object POP C allows parallel objects to be arbitrarily passed from one place to another as arguments of method invocations input Zo input data flow D J worker CEJ user workstation data server worker Fig 2 1 A scenario using shared parellel objects 2 4 Methods Invocation Semantics Syntactically method invocations on parallel objects are identical to those on traditional sequential objects However to each method of a parallel object one can associate different invocation semantics Invocation semantics are specified by programmers when declaring methods of parallel objects These semantics define different behaviours for the execution of the method as described below see section 3 2 3 for syntax details Interface semantics the semantics that affect the caller of the method 6 Parallel Object Model Synchronous invocation the caller waits until the execution of the called
46. ot POP C Community The reason is that even if the POP Model has been first implemented in the C OO programming language POP C this model can be implemented in any other OO languages such as Java POP Java Because all languages in which the POP Model is implemented must be able to work together interoperate we build a community based on the POP Model and not on a specific language A prototype of the POP Java language is available at the GRID amp Cloud computing group We hope to release this prototype soon 5 1 3 Standard mode This is the most used mode It s the best choice to use POP C inside a trusted environment for example inside a department an enterprise or on a cluster Installation Instructions 33 5 1 4 Secure mode In this mode all communication between the parallel objects are encapsulated in secure tunnels SSH More information about the secure mode can be found in the manual POP C over SSH Tunnel 5 1 5 Virtual mode If you intend to execute a parallel object on a system you cannot trust you want to be sure that this system will not badly interact with your objects In addition the owner of the remote system wants to be sure that the execution of your object cannot harm his system in any manner To fulfill these requirements POP C can be installed to have remote objects running in virtual machines More informations about this mode is available in the manual POP C Virtual User and Insta
47. r POP Community way you will most of time use the parameter prefix lt install dir gt to install POP C in a directory where you are allowed to write configure prefix lt install dir gt or if the variable POPC_ LOCATION has been defined configure prefix POPC_LOCATION Note For MacOS system do not forget the DARCH MAC flag A lot of other parameters can be added to the configure command but there are usually not used with the standard mode More details about the available options can be found in 36 Installation Instructions the document Advanced POP C User Manual or by typing the command configure help 5 3 2 Compiling POP C tool When configured you can compile POP C tool by entering the command make This command can take several minutes If the compilation completes successfully you can install POP C runtime files in the lt insta11 dir gt by entering the command make install Note you must have read write access to the lt install dir gt 5 3 3 POP C Setup Shortly before the installation finished the system will automatically launch the pope setup script This script can be re launched at any time after the installation of to modify the parameters of POP C The setup is divided in two parts the first one configures your POP C installation and the second one create the startup scripts which are used to launch POP C At this time you will be able to choice if you will ru
48. ram see section 3 3 there is a little risk that the same identifier is assigned to several different classes residing in different C executables This will cause a program crash To avoid this problem POP C provides to programmers the possibility to manually assign unique class identifiers to parallel classes This is done using the classuid function as shown below parclass ExampleClass public classuid 1001 We recommend to use values for classuid greater that 1000 3 4 POP C standard library Alongside with the compiler POP C supplies a standard library This library offers classes and functions which can be useful or even necessary to write complex POP C programs This library are described in this section 3 4 1 The POPString class The class string is an often used class in C programs Used as is the string class cannot be marshaled demarshaled because it does not derived from POPBase To overcome this difficulty the POP C library provides the POPString class This class can be used to pass string argument to methods of parallel classes It is designed to ease as much as possible conversion from string or char to POPString and the reverse Methods of the POPString class are shown in the figure 3 5 User Manual 19 Constructors POPString POPString const char x POPString const char x int n POPString std string x POPString const POPString amp x Destructor POPString
49. ruction using the this the first one above calls the method aMethod taking into account the semantic of the method sync async seq In such a case you must take care because you can easily cause deadlocks It is the case for example if the method which make the call and the called method have both the seq semantic If we call aMethod without the this the second one above the semantic is not taken into account i e that aMethod is considered as a normal C internal method of the object Important notice the description below corresponds to the normal behavior of POP C Unfortunately in the version V2 0 there is still a bug which makes sometime calls using this to block even when there is no reason to block no deadlock This bug should be fixed in future versions When this is used to pass a reference to the current parallel object the behavior is the same that for standard C object Nevertheless this cannot be passed as is as parameter to methods of parallel object because it is a pointer pointer parameters are not allowed for methods of parallel classes In such a case only this can be passed 3 3 Object Layout 3 3 1 The pack directive A POP C application is build using several executable files One of them is the main program file used to start the application Other executable files contain the implementations of the parallel classes for a specific platform An executable file can store the implementatio
50. s from linking parclass nointerface Do not generate POP C interface codes for parallel objects parclass nobroker Do not generate POP C broker codes for parallel objects object type Generate parallel object executable linking only type std default or mpi popcpp POP C parser cpp lt preprocessor gt C preprocessor command cxx lt compiler gt C compiler popcld lt linker gt C linker default same as C compiler popcdir POP C installed directory noclean Do not clean temporary files verbose Print out additional information nopipe Do not use pipe during compilation phases create _paroc2_ files version Display the installed POP C version Environment variables change the default values used by POP C POPC_LOCATION Directory where POP C has been installed POPC CXX The C compiler used to generate object code POPC CPP The C preprocessor POPC _LD The C linker used to generate binary code POPC PP The POP C parser 42 Command Line Syntax Running an application popcrun objects config drun runlocal prog main args drun Print launching command only runlocal Force to create all objects locally do not use JobMgr debug Give some debugging informations log lt filename gt put all message in the lt filename gt fil version Display the installed POP C version Runtime environment variables Appendix 43 B Runt
51. ss a pointer to the exception from the place where it was thrown to the place where it will be caught In distributed environments where each component is executed in a separate memory address space and data could be represented differently due to heterogeneity the propagation of exceptions back to a remote caller is much more complex In addition as POP C supports asynchronous calls when a exception is thrown in an asynchronous method the caller can be out of the context where it can catch this exception For all these reasons exceptions handling in POP C is slightly different than in pure C programs POP C supports transparent exceptions propagation Exceptions thrown in a parallel object will be automatically propagated back to the remote caller only when the exception is thrown in a synchronous method In addition the current POP C version allows the following types of exceptions e Scalar data int float etc e Parallel objects e Objects of class POPException provided by the standard POP C library All other C exception types struct class will be converted to POPException with the UNKNOWN exception code If the exception is thrown in an asynchronous method the exception is not transferred to the caller but directly to the POP C run time which will cleanly abort the program The drawback of this approach is that the programmer cannot catch exceptions thrown in asynchronous methods This is especially penaliz
52. t int minp od power want minp Integer POPString machine od url machine async seq void Set int val sync conc int Get async mutex void Add Integer amp other classuid 1001 private int data hi Fig 3 11 The file integer ph As shown in figure 3 11 the declaration of a parallel class is introduced by the keyword parclass instead of class line 1 The two constructors lines 3 and 4 of the Integer parallel class are both associated with objects descriptors which are placed directly after the argument declaration before the terminator The first object descriptor line 3 specifies a resource requirement i e computing power The second object descriptor line 4 specifies the name of the computer the object must be executed on Depending on the constructor which will be used to create the object one or the other of these two requirements will be satisfied for the created parallel object The method invocation semantics are defined in the parallel class declaration by placing corresponding keywords sync async mutex seg conc in front of the method declaration In this example the Set method line 5 is sequential asynchronous the Get method line 6 is synchronous concurrent and the Add method line 7 is asynchronous mutual exclusive If one or both of the semantic keyword is are omitted the default values are sync and seq 3 5 2 Integer cc The imp
53. teger Pro erronea ninia acne 28 4 2 OOO A AT LASA RR 28 4 2 2 Compiling the object codec add lid 29 42 3 RUNNIN t 29 4 3 Compiling a POP C program containing several parallel classes with dependencies 30 5 Installation InstrUctions A AA A a Gas A aa Aaa cee Cass 31 5 1 O 31 O incl ais aaa tt aS 31 512 POP COmm nit yo ON 31 51 3 Stand ard Mode aye west ii ly oui E RR e E OS 32 SLA Secure MOTO a a A ia 33 RR EA E E AT he Siaros E 33 5 1 6 Virt a Secure MOE AA a ees a a A RA AAA 33 5 2 A O e R a a E atari EN 33 5 2 1 Prereguisites soccricnieteniairnian iie a a aa r a a e a aut 33 5 2 2 Lo tion of the Mlese en e a a E RAA EERE E E 34 5 2 3 Downloading the POP C Distribution 1d 34 5 3 Standard Installation ii A a 35 5 3 1 Preparing compilation A E a aed 35 5 3 2 Compiling POB CA AL A A an a ae ed 36 5 3 3 POP CHF Setup nn ak ds abet pat heans ore aaetaveteneaeicmuaaieataees 36 5 3 4 Files modified by the setup ds 39 5 4 Testing Installation E sens EEE EE RE 39 5 3 Start Stop POP CHF sak tates focus o arc a a ealys 40 As Command Line A OS 41 Compiling an applicatio A A aang a a 42 B Runtime environment variables a A A A 43 Bibl banda E EEE A EE E E ES 44 Introduction and Background 1 CHAPTER 1 Introduction and Background POP 1 1 Introduction 1 4 Structure of this Manual 1 2 The POP Model 1 5 Additional Information 1 3 System Overview 1 1 Introduction Programming large heterogenous distribute
54. thod returns a POPString associated with the exception Print method prints a text describing the exception All exceptions that are instance of parallel objects are propagated by reference Other exceptions are transmitted to the caller by value 3 5 Programming example In this section we present a example of a simple POP C program using only one parallel class This example implements a parallel class called Integer 3 5 1 Integer ph As already mentioned POP C source code is very close to pure C code The main difference is in the declaration of parallel classes This is why we strongly recommend when writing programs in POP C to strictly put declarations and implementations of classes in separated files In C the convention is to use the h extension for source files containing classes declarations and the cc extension for source files containing implementations of classes With POP C a new type of source files is introduced e Source files containing declarations of parallel classes We use the standard ph extension for these source files Figure 3 11 shows the declaration of the parallel class Integer As mentioned from the syntactic point of view this part contains the major differences between POP C and C 24 User Manua Nevertheless a parallel class declaration remains rather similar to a pure C class declaration with the addition of some new keywords parclass Integer public 3 i Integer int wan
55. ting C libraries can be parallelized without much effort Changing a sequential C application into a POP C distributed parallel application is rather straightforward on a syntactic point of view Parallel objects are created using parallel classes Any object that instantiates a parallel class is a parallel object and can be executed remotely To help the POP C runtime to choose a remote machine to execute the remote object programmers can add object description information to each constructor of the parallel object see sections 2 6 and 3 2 4 In order to create parallel execution POP C offers new semantics for method invocations These new semantics are indicated thanks to five new keywords see sections 2 4 and 3 2 3 Synchronizations between concurrent methods are sometimes necessary as well as event handling The standard POP C library supplies some tools for that purpose see section 3 4 This chapter describes the syntax of the POP C programming language and presents main tools available in the POP C standard library 10 User Manual 3 2 Parallel Objects POP C parallel objects are a generalization of sequential objects Parallel objects are instances of parallel classes see 3 2 1 Unless the term sequential object is explicitly specified a parallel object is simply referred to as an object in the rest of this chapter 3 2 1 Parallel Classes Developing POP C programs mainly consists of designing and implement
56. ult value o async Asynchronous invocation Callee side o seq Sequential invocation This is the default value o mutex Mutex invocation o conc Concurrent invocation The combination of the caller and the callee side semantics defines the overall semantics of a method six different combinations For instance the following declaration defines an synchronous concurrent method that returns an integer number sync conc int myMethod 3 2 4 Object Description Object descriptions are used to describe the resource requirements for the execution of the object Object descriptions are declared along with parallel object constructor statements Each constructor of a parallel object can be associated with an object description that resides directly after the argument declaration before the instruction terminator operator The syntax of an object descriptor teh following expressions An object description contains a set of resource requirement expressions All resource requirement expressions are separated by semicolons and can be any of the following od resNum exact od resNum exact lbound od resString resource resNum power memory network resString protocol encoding url 12 User Manual Both exact and lbound terms are numeric expressions and resource is a null terminated string expression of type POPSt ring see section 3 4 1 The semantics of those expressions depend on the resource requir
57. utions to commonly found problems Programming examples Latest sources http gridgroup hefr ch popc 4 Parallel Object Model CHAPTER Parallel Object Model POP 2 1 Introduction 2 4 Methode Invocation Semantics 2 2 Parallel Object Model 2 5 Parallel Object Allocation 2 3 Shareable Parallel Objects 2 6 Requirement driven Parallel Objects 2 1 Introduction Object oriented programming provides high level abstractions for software engineering In addition the nature of objects makes them ideal structures to distribute data and executable codes over heterogeneous distributed hardware and to make them interact between each other Nevertheless two questions remain Question 1 which objects should run remotely Question 2 where does each remote object lives The answers of course depend on what these objects do and how they interact with each other and with the outside world In other words we need to know the communication and the computation requirements of objects The parallel object model presented in this chapter provides an object oriented approach for requirement driven high performance applications in a distributed heterogeneous environment 2 2 Parallel Object Model POP stands for Parallel Object Programming and POP parallel objects are generalizations of traditional sequential objects POP C is an extension of C that implements the POP model POP C instantiates parallel objects transparently and dynam
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