JOPI: Java Object-Passing Interface
Contents
1. mp waitIsend int requestID This will check the send operation and only return if the requested send operation has completed An Isend followed immediately by waitIsend will be equivalent to using the send method waitlreceive This is a synchronous blocking method to check for the completion of asynchronous non blocking receive operation waitIreceive will not return until the receive operation is completed and the object is in the receive buffer On return this method will return the received object As in testIreceive it uses requestID to identify the operation to be checked Obj ref class type mp waitIreceive int requested This will block the process until the object reguested is received and will return that object Here also a combination of receive followed immediately by waitIreceive is eguivalent to a synchronous receive method A cast for the object received must be given 4 Support operations a receiveSource This method is used after a successfully completed receive operation to identify the source of the object received This is mainly useful if the receive operation used the JOPI ANY SOURCE attribute This operation can follow the receive Ireceive Bcast at the receiving end successful testIreceive if object returned is not Null and waitIreceive methods This method will return an integer value representing the sending processor number The result returned will correspond to the last successfully compl2. Object Passing Interface User s Guide new listClass toPos fromPost 1 System arraycopy list fromPos t list 0 toPos fromPos 1l return t public int sum int 1 int result 0 for 1 0 1 lt size itt result list i return result Problem Solution method RK KR ee AA AA AAA AA AAA A ee To compile the program javac listl java The contents of lista pj MainClass listl Classes listl class listClass class AutoSchedule 5 NoLocal To run the program pjava lista pj Output Reading the parallel java job file Loading user classes Implementing job schedule Starting Job ID 20351 with 5 threads Running 2 threads at agent agent5 Running 2 threads at agent agent2 Running 1 threads at agent agentl 0 Process load 1200 1 Process sub sum 6426 2 Process 2 sub sum 6664 19 Process 3 sub sum 6672 Process 0 sub sum 6616 6790 List sum 33168 3 O 4 Process 4 sub sum O 0 Time taken 36 A different run of the same program The contents of listb pj MainClass listl Classes listl class listClass class Agent agentl 2 Agent agent2 2 Agent agent5 1 NoLocal To run the program pjava listb pj Output JOPI The Java Object Passing Interface User s Guide Reading the parallel java job file Loading user classes Starting Job ID 87243 with 5 threads Running 2 threads
3. Running 2 threads Running 1 threads at agent agentl at agent agent2 at agent agent5 0 Process load 1200 1 Process 1 sub sum 6657 2 Process 2 sub sum 6630 3 Process 3 sub sum 6735 0 Process 0 sub sum 6553 4 Process 4 sub sum 6654 0 List sum 33229 0 Time taken 40 The first six lines of the output are general information to show the user what is happening and where the program threads are going to execute The rest of the lines are the result of the mp print statements in the program The number between the sguare brackets is added to show which process initiated the print statement 20 JOPI The Java Object Passing Interface User s Guide Acknowledgements This project was partially supported by a National Science Foundation grant Nebraska University Foundation grant and the Priority Initiative in Simulation and Modeling grant This project was supervised by Dr Hong Jiang and Dr David Swanson UNL Please note If you find any errors or typos please send an e mail to jopi cse unl edu Index Bold Page number is most significant mention of keyword JOPI Java Object Passing Interface 3 4 5 6 7 8 9 10 11 13 14 15 16 17 JOPLANY CLA SS uz sos sexsceseussvnsinevosvenses sot bo seven 6 7 8 10 JOPI ANY SOURCE ossessi JOPI ANY TAG JVM Java Virtual Machine Kill O Deitezsiececteieteiitckion LISUT DEAS esensina MainClass eee 21 JOPI Th
4. can also use JOPI ANY SOURCE JOPI ANY CLASS and or JOPIANY TAG in place of pid className and or tag respectively Examples Obj_ref class_ type mp receive J OPI ANY SOURCE JOPI ANY CLASS JOPI ANY TAG This allows the receive method to accept any incoming message from any process of any class type and with any tag value Obj_ref class_type mp receive 4 JOPI ANY CLASS 0 This receives an object of any class type from process number 4 and with tag value 0 greetings Greetings Class mp receive 0 Greetings Class 0 This will receive the object greetings sent by process 0 see the send example 2 Synchronous blocking group operations a Beast This is a group communication method that allows one process to send an object to all other processes When broadcast is used all processes will issue the Bcast command The sender will specify the object to be sent and all other processes will act as receivers to get that object Broadcast is blocking so the sending object will block until the object is successfully sent while each receiving process will wait until the object is received in its buffer before continuing There are two variations of the broadcast method mp Bcast Object obj int group_ no Used by the sending process to broadcast the object obj to the group identified by group no obj is astring and group no is an integer Obj ref class type mp Bcast int group no Used by all other processes to r
5. collective operations external interfaces I O and additional language bindings such as C bindings Object Oriented MPI OOMPI was introduced a few years ago with the main concern to provide C programmers with more abstract message passing methods JOPI provides similar functions using objects as a means of exchanging data and logic This provides users with the ability to encapsulate not just the data but also the logic that uses that data into a single object that can be then sent to other processes to be used there The object oriented paradigm preserved in JOPI allows users to simplify the process of writing parallel programs The programmer here has the flexibility of using the available JOPI methods to exploit the different properties to optimize the programs Compared to the standard MPI JOPI allows the programmer to exchange objects instead of predefined data JOPI The Java Object Passing Interface User s Guide elements This means that the programmer need not worry about the type or size of the message to be sent All that is required is to have all the data encapsulated within an object When using JOPI the programmer needs to identify the problem and write the necessary code to solve it sequentially Then methods can be added to handle problem partitioning for a parallel solution and to reconstruct the solution from the partial solutions computed by the different processes The parallelization process can then be easily done
6. message passing functions 4 Explicit interaction user must resolve all interaction issues such as communication synchronization and aggregation 5 Explicit allocation workload and data must be explicitly allocated to processes by the user 6 logic Exchange Object passing allows processes to exchange codes not just data which provides a flexible scalable and easy way to use the parallel environment The Message Passing Interface MPD is a library of routines provided for users who wish to write parallel and distributed programs MPI 1 was developed for use mainly with FORTRAN and C language It provides a number of library functions to exchange messages between processes It provides functions for point to point communication group communications synchronization and others Using MPI for parallel programming is not trivial It requires the programmer to be aware of almost all of the parallelization issues and details of the messages to be exchanged On the other hand this provides the programmer with high flexibility MPI 1 can be used to exchange messages containing one data type such as integers float or char In addition it allows packing and unpacking of data of different lengths or types It also can allow passing arrays and structures but this requires a lot of coding Later MPI 1 2 and MPI 2 was developed as extensions of MPI 1 additional functionality such as process creation and management one sided communications extended
7. process ID pid the object to be sent and the tag As in standard MPI the tag is used to pair send and receive operations to make sure the receiving process receives the correct object mp send int pid Object obj int tag Where pid and tag are integers Example Assume we have an object called greetings defined from a class Greetings_Class then the following line will send the object greetings to process number 2 with tag value 0 mp send 2 greetings 0 receive This is a method used by a process to receive an object sent by another process The user can specify where the object is coming from pid The class name a string argument that the object belongs to ClassName and the tag tag The user also has the choice to use JOPI ANY TAG JOPI ANY CLASS or JOPI ANY SOURCE to receive an object with any tag value of any class type or from any other process respectively This method blocks the receiving process until the receive operation is complete and the object is in the receiver s buffer It always returns an object the received object A cast for the class type of the object received must be given to get the correct object format Usually if className is given it should be the same as class type Obj_ref class_type mp receive int pid String className int tag JOPI The Java Object Passing Interface User s Guide This will receive an object from process pid with class type className and tag value of tag The user
8. to be sent it was defined using the Java Integer class This way the subSumResult variable becomes an object of the class Integer which is serializable and can be used by JOPI Following is the full program code followed by two versions of the job execution file and the steps of compiling and running the program KKK KR eR A AAA AA AAA X K kk AA AA ee The source code for the example program listl java import java io import java util import java net public class listl Main class public static void main String args int MAX_SIZE 6000 Maximum size of the list int RANGE_FROM 1 Minimum value of an element int RANGE_TO 10 Maximum value of an element int i j load sumValue long startTime 0 endTime 0 diff 0 JOPI mp new JOPI args Instantiating a JOPI object Integer subSumResult Defining an Integer object listClass fullList partList defining a list objects if mp myPID process 0 fullList new listClass MAX SIZE RANGE FROM RANGE TO load MAX SIZE mp nprocs Size of sublists mp print Process load load startTime System currentTimeMillis 17 JOPI The Java Object Passing Interface User s Guide for j 1 j lt mp nprocs j Repeat for all processes Make a sublist of the original list partList fullList subList j load j load load 1 Send the sublist to process j mp send j partList 0 Process
9. using the available methods and the JOPI methods To support JOPI s library functions we included the following features in the agent based run time infrastructure 1 Providing mechanisms to load user programs onto the remote JVMs of the cluster nodes and the machines used 2 Managing cluster resources and scheduling user jobs 3 Providing security measures to protect the user programs and the machines used 4 Providing job and thread naming to facilitate simultaneous multi user and multi job executions and proper process identification 5 Providing user commands and control operations that facilitate job submission monitoring and control JOPI The Java Object Passing Interface User s Guide 3 JOPI API This part contains all the functions that provide the user with the Java parallel programming object passing interface Using the functions in this class the user can send receive and broadcast objects Please keep in mind that Java is case sensitive thus JOPI is also case sensitive Therefore make sure to follow the proper syntax and letter case for the methods and attributes of JOPI The objects that are used in send and receive must be defined to implement Serializable i e they must be serializable for the system to be able to move them to remote processors Example class List_ Class implements Serializable In addition other attributes to identify the process ID and number of processes are available Before using t
10. 0 also works on a sublist partList fullList subList 0 load 1 sumValue partList sum mp print Process mp myPID sub sum sumValue for j l j lt mp nprocs j Repeat for all processes Receive sublist sum and add to overall sum sumValue subSumResult Integer mp receive j JOPI ANY_CLASS 1 sumValue subSumResult intValue Register end time and calculate and print total time ndTime System currentTimeMillis diff endTime startTime mp print List sum sumValue mp print Time taken diff else Other processes Receive sublist from process 0 partList listClass mp receive 0 JOPI ANY_CLASS 0 Calculate and send the sum to process 0 int subSum partList sum mp print Process mp myPID sub sum subSum subSumResult new Integer subSum mp send 0 subSumResult 1 mp close Close message passing object class listClass implements Serializable Problem class public int size public int public listCl list ass int tsize size tsize list new int tsize ass int tsize int fromNo int toNo public listCl int 7 size tsize list new int tsizel Random r new Random for i 0 i lt size i list i r nextInt toNo fromNo 1 fromNo public listClass subList int fromPos int toPos Sub Problem method 18 listClass t JOPI The Java
11. University of Nebraska Lincoln Computer Science and Engineering JOPI Java Object Passing Interface User s Guide di AA 2 ada Moning JOPI The Java Object Passing Interface User s Guide Table of Contents Introduction MPI Vs JOPI JOPI API Attributes Methods 1 Synchronous blocking point to point operations 2 Synchronous blocking group operations 3 Asynchronous nomblocking point to point operations 4 Support operations Example 4 Compiling and Running Programs 5 Error Messages 6 Example JOPI Program 17 Summation of numbers in a list 17 Acknowledgements 21 Index 21 U DE ore U NISO S O V aa V NM WD WN JOPI The Java Object Passing Interface User s Guide 1 Introduction Clusters require system and software services that can support the distributed architectures and provide transparent and efficient utilization of the multiple machines available In addition Java is becoming a good option for developing high performance and distributed applications on clusters We introduce an infrastructure for a parallel programming environment in Java The system provides Java programmers with the necessary functionality to write object passing parallel programs in clusters The main features of JOPI are 1 It is suitable for clusters and distributed heterogeneous systems 2 It utilizes the object oriented programming paradigm for parallel programming thus simplifying the development process and 3 It is mo
12. cify the class type and or the tag Notice that it is possible to use broadcast method in this example to distribute the greeting message to the processes To do that all you need to do is replace lines 14 and 15 with the following mp Bcast greeting 1 which will broadcast the string object to all other processes and line 20 by Greeting String mp Bcast 1 10 JOPI The Java Object Passing Interface User s Guide mp barrier int id int No_ procs which will first allow each process to receive the broadcast message and then wait until all processes reach this point making sure all received the message before printing the message and exiting import java io import java util import java net public class Hello_1 Main class public static void main String args int j String greeting JOPI mp new JOPI args Instantiating a message passing object if mp myPID 0 process 0 greeting Hello World for j 1 j lt mp nprocs j mp send j greeting 0 mp print greeting I am process number mp myPID else other processes greeting String mp receive 0 JOPILANY_CLASS JOPLANY_TAG mp print greeting I am process number mp myPID mp close Close message passing object Example A parallel JOPI program to print a greeting message from all processes 11 JOPI The Java Object Passing Interface User s Guide 4 Compiling and Running Progra
13. cked When testIsend is issued the system checks if the request for send identified by the reguestID has completed It will return true if completed and false if not SendFlag mp testIsend int requestID This will check the send operation and return true if the requested send operation has completed and false otherwise SendFlag must be defined as Boolean testIreceive This is an asynchronous nomblocking method to check if an asynchronous receive operation receive has completed It uses the requestID to identify the receive operation to be checked When testIreceive is issued the system checks if the request for receive identified by the requestID has completed It will return the received object if completed and Null if not Obj ref class type mp testIreceive int requestID JOPI The Java Object Passing Interface User s Guide This will check the receive operation and will return the received object in the Obj_ ref if the receive operation has completed and will return Null otherwise Here also a cast needs to be given for the object received The programmer must check the object to know if the receive operation has completed test for Null before trying to use that object waitlsend This is a synchronous blocking method to check for asynchronous non blocking send operation completion waitlsend will not return until the send operation is completed As in testIsend it uses requestID to identify the operation to be checked
14. e Java Object Passing Interface User s Guide ina nA ES AD EO nO VE nO eT S VR AEAEE O O eo me eT ee TTT 6 10 16 17 13 18 19 Serializable Support operations Synchronous blocking group operations testAgents HOSE POCEIVE 3 Sixx 63733 bok o oo bodce PTP testIsend WA IEL TF OCELV e MOTETO EREN EAE oo De oo WalEl SEC 42b k zo ed ked zoo A da oo oo lod o Le fh a Male Sit rr o oo nn 22
15. eceive the broadcast message the group number group no here must match the one specified by the sending process This method will return the received object To receive the correct object it must be cast into the proper class type using class type b barrier This is a synchronization method used to synchronize a group of processes When the barrier method is invoked with a given number of processes any process reaching this method will suspend its execution and wait until the specified number of processes reaches the barrier then they all can resume execution at the same time mp barrier int id int no procs Here the id integer is used to identify the barrier since many barriers may be issued in a program NO procs integer indicates the number of processes that must reach the barrier before all of them can go on JOPI The Java Object Passing Interface User s Guide 3 Asynchronous non blocking point to point operations a Isend This method like send is used by a process to send an object to another process Here it allows the process to issue a send request and go back to its computations without waiting for the send operation to complete Later the process can use the testIsend or waitIsend methods to check if the send operation was completed The method Isend will return a request identification number request D to be used for verifying the send completion When a process issues an Isend operation it should not modify t
16. eted receive operation only The method cannot provide information about other past receive operations Source no mp receiveSource receiveClass This method is used after a successfully completed receive operation to identify the class type of the object received This is mainly useful if the receive operation used the JOPI ANY CLASS attribute This operation can follow the receive Ireceive Bcast at the receiving end successful testIreceive if object returned is not Null and waitIreceive methods This method will return a string which provides the class name the received object belongs to The result returned will JOPI The Java Object Passing Interface User s Guide correspond to the last successfully completed receive operation only The method cannot provide information about other past receive operations Class name mp receiveClass c receiveTag This method is used after a successfully completed receive operation to identify the tag value associated with the received object This is mainly useful if the receive operation used the JOPI ANY TAG attribute This operation can follow the receive Ireceive Bcast at the receiving end successful testIreceive if object returned is not Null and waitIreceive method This method will return an integer value representing the tag value associated with the object The result returned will correspond to the last successfully completed receive operation only The method cannot pro
17. expandability flexibility security and resources management Using the Java Object Passing Interface JOPI provided the programmer will be able to write parallel programs that can run on multiple nodes of a cluster or network where the agents reside In addition the system is written completely in standard Java and can be used on any machine that has a Java virtual machine JVM This document is a user guide for the system It will provide information about how to use the environment and how to write parallel Java programs using the JOPI class Since the interface provided is similar in some ways to standard MPI we decided to include some information about MPI first The third section introduces the different methods and attributes of the JOPI class and how to use them when writing the parallel programs Then the next section talks about the environment and the different commands available to run the parallel Java programs JOPI The Java Object Passing Interface User s Guide 2 MPI Vs JOPI Object passing like message passing is a model of explicit parallel programming with the following characteristics 1 Multithreading a message passing program has multiple processes that have their own control and may execute different code 2 Asynchronous parallelism processes execute asynchronously and require explicit synchronization 3 Separate address space each process has its own address space and exchanges information using special
18. he methods available in JOPI class like with any other Java classes the user must define an instance of the JOPI class for the program JOPI mp new J OPI String args Where args is the array of arguments passed to main and mp is the name of the instance created from JOPI The following gives details of the methods and attributes in the JOPI class which the user can now use to write a parallel Java program We will use the instantiated JOPI object mp defined above in all our following examples for the sake of clarity However users are free to select the names of their objects and the user defined classes and attributes Attributes A number of attributes are defined in the JOPI class that support parallel programming using the object passing model The explicit communication requires the programmer to identify individual processes and other supporting values First the user needs to know the process identification number of each processes used and the total number of processes in the program In addition some general attributes are needed to issue general operations that do not require specific values a mp myPID This field is an integer and contains the current process identification number which can be used in other methods such as send receive Isend Ireceive etc b mp nprocs This field is an integer and contains the number of processes in the user job program This is necessary for workload distribution among participa
19. he object sent before making sure the operation has completed using the testIsend or waitlsend methods Otherwise such changes may affect the results of the execution since the data sent may not be the one intended RequestID mp Isend int pid Object obj int tag Ireceive This method like receive is used to receive an object from another process Here it allows the process to issue a request to receive an object and then continue with its processing Later the process can issue a testIreceive or waitlreceive function to find if the receive request was fulfilled This Ireceive will return a request identification number reguestID that can be used to check the request ReguestID class type mp Ireceive int pid String className int tag This will issue a request to receive an object identified by className from a sender identified by pid with a given tag value As in blocking receive a cast must be given for the object received In addition the static attributes J OPI ANY SOURCE JOPI ANY CLASS and J OPI ANT TAG can be used just like with the send method When Ireceive is used the object will not be available for use by the process until the receive operation is completed Therefore it is necessary to check for its completion before using the object testIsend This is an asynchronous non blocking method to check if an asynchronous send operation Isend has completed It uses the requestID to identify the send operation to be che
20. he user s local machine However the user has the option to override this setting and execute the root process on a remote machine thus limiting its access to system resources The user can specify if root process should or should not run on the bcal machine line 4 in the example NoLocal means that root process should not run on the local machine If it is not included then the root process will run on the local machine When JOPI is first installed the administrator may bypass the security restrictions thus allowing user processes to have full access to all recourses on all the machines used If this is true then the NoLocal option will not have much effect on resource access MainClass Hello_1 Classes Hello_1 class AutoSchedule 4 NoLocal Example hello pj file for the Hello_l java program shown earlier In this case the main class is Hello_1 and it is the only class in the program Automatic scheduling was selected and all processes will run on remote machines When the pj file is ready the user can run the program using the following command pjava filename pj Example pjava hello pj The client services class is the link between the user and the agents It accepts requests from the user encapsulate the job and the necessary information into a request object and passes it to the agent It also handless all the commands issued by the user such as pingAgent and listThreads A number of commands are available for the
21. in running user threads 1 Check your source code in most cases there may be Java run time error some exception messages displayed that can help pinpoint the errors 16 JOPI The Java Object Passing Interface User s Guide 6 Example JOPI Programs Here we provide a full example of parallel Java programs written using JOPI The code can be easily extracted and compiled as a Java program The pj examples given here are specific to the system we are using and may require changes mainly the agent names and number of processors used Summation of numbers in a list Although not a very useful application the following is a complete parallel program that calculates the sum of the elements of a list The class listClass defines the methods and attributes needed to create divide and manipulate the list The main class is responsible for the parallelization process Process 0 is the master process and it uses the methods in listClass to divide the list into sub lists sends the sub lists to other processes calculates its own sub list and then receives and adds the sub sum values received from the other processes and reports the final result Each process including the master process will calculate the sub sum of part of the list print the partial result and send it back to process 0 The program also calculates the time of execution using the system time method JOPI can only send and receive objects therefore when an integer value was
22. mmand pingAgent The integer number following the agent name specifies how many threads should run on that machine This sequence may replace Ine 3 means that two threads will run on the machine that has agent1 and the machine that has agent3 on it and one thread will run on the machine that has agent2 on it The total number of threads processes here is 5 The system allows multiple users to run multiple jobs at the same time To properly manage these jobs each job has multiple levels of identification starting with a unique job ID assigned by the system The user ID and the program name further distinguish different jobs Within each job thread IDs are used to identify the remote threads of the job To protect user applications and the systems executing them two modes of execution are utilized 1 Agent mode which allows a process to access all available resources on local and 12 JOPI The Java Object Passing Interface User s Guide remote machines and 2 user mode which allows access to the CPU and memory for execution only on remote machines With the security modes in place the user processes have full access to resources on their local machine where the user job was initiated In addition user processes have very limited access to all remote machines resources since they are running in user mode To provide users with access to necessary resources for their application the root master process is forced to execute on t
23. ms When the program is complete it should be compiled using javac like any other regular Java program Example if the program name is prog1 java then compile as follows javac Hello 1 java To run the program after successful compilation the user needs to define a parallel job file This file is given a pj extension and should contain the following information see the example below please note that the line numbers are only for illustration purposes and that they are not part of the file 1 The mame of the main class in the program preceded by the keyword MainClass line 1 2 The keyword Classes followed by the names of all classes used in the program including the main class line 2 3 The number of processors needed and how they are scheduled The schedule for the processes can be left to the system using AutoSchedule option in this case the user need only specify the number of processes needed to run the program line 3 Example AutoSchedule 6 This will make the system automatically create a schedule for six processes On the other hand the user can specify his her own schedule by listing the agents and number of threads to run on each agent Example Agent agenti 2 Agent agent2 1 Agent agent3 2 Agent is a keyword and agent1 agent2 and agent3 are the names of the agents on the machines used These names are defined in the system in the agents list file and the user can get a list of these names by using the co
24. ntax of the command indicated PS oman ies p PJ004 Class lt class name gt could not 1 Make sure the class name is included correctly in the pj be loaded file Verify the class name spelling and case in the pj file PJ005 Class file lt file name gt does Make sure the class names listed in the pj file are the not exist same as the ones used in your program Make sure the class names are correct names in pj file match the names in the source code Make sure the class is accessible and in the correct location Check the path settings to your files 15 JOPI The Java Object Passing Interface User s Guide Display Messages Codes SY001 Agents list file lt file name gt 1 Make sure the agents file is available in its designated can not be read location physical file is called agents 2 Make sure the path settings to the agents list file is correct 3 Contact the system administrator if the file is not available SY004 Directory file lt directory file gt 1 Contact admin to verify the existence of this directory and SM dos poteris make sure th avalabile and n tne conme ction Timeout in send operation 1 Thread unable to send a message to destination before timeout 2 Check network connectivity between nodes 3 If persistent report problem to admin to check SY006 Receiving Thread Error 1 Report problem to admin to check However admin ay not be apl to solve is immediately I UP001 Error
25. s to be checked The default option for this command is all This command provides the following information about each thread i Agent the agent on which the thread is running on ii J obID the identification number of the job this thread belongs to iii User the user this job belongs to iv Program The name of the main class program that created this thread v Pid the identification number of the thread vi R Time the amount of time passed since the thread started execution testAgents gt Used to report some performance features about the machines where the agents are running This command activates a small program on all agents and measures the amount of time it takes each agent to complete that program This gives a relative measurement of how much load or how fast the agent can execute programs This is currently used by the scheduler to identify the fastest available agents to schedule the jobs accordingly It is also available for the users for testing purposes kilJob jobID gt This is a command to terminate a given user job like the kill command in UNIX The user needs to specify the jobID can be found using listThreads command with the command When a job is killed all the threads that belong to it will be terminated on all the machines originally executing this job 14 JOPI The Java Object Passing Interface User s Guide 5 Error Messages When compiling a program that uses JOPI the syntax errors and
26. st suitable for large scale applications and applications with low communication to computation ratio The Java object passing interface JOPI provides an MPI like interface that can be used to exchange objects among processes Using objects to exchange information is advantageous because it facilitates passing complex structures and enables the programmer to isolate the problem space from the parallelization problem Software agents were used to provide the necessary functionality on the participating processors Users need not deal with the mechanisms of deploying and loading user classes on the heterogeneous system nor to deal with scheduling controlling monitoring and running user jobs In addition users need not deal with managing the system resources Since this system is written completely in Java it is portable and can allow run programs in parallel across multiple heterogeneous platforms A number of experiments were conducted using this system to measure its performance The results gathered show that it is possible to gain good performance using this system and that future potential for enhancements and optimizations are feasible This system provides an infrastructure for high performance computing in Java parallel Java for clusters or heterogeneous systems Software agents were used to provide the necessary functions that support the JOPI on clusters and distributed environments Some of the benefits of using agents are portability
27. standard Java errors will all be identified by the Java compiler However there are other parts that are checked by the JOPI run time environment and may generate a different set of errors We used unique identifiers for these errors starting with two characters indicating the type of the error followed by a three digit number for the error Short error messages follow the identifier for the user s information The following table lists the error messages and the possible actions that can be done to resolve them The errors are of three types 1 PJxxx are errors concerning the pj file Generally these errors can be resolved by checking the pj file and making some corrections 2 UPxxx are errors related to the user program In most cases the exception messages would help in identifying the source of the error 3 SYxxx are system related errors Many of these errors may require the help of the JOPI administrator to resolve Error Display Messages Action Codes PJ001 Agent lt agent id gt is not 1 Check the agents and their status active inactive using defined in the agents list file pingAgent or inactive 2 Check agent names in your pj file and make sure they are spelled correctly and only active agents are used PJ002 Parallel Java file lt file id gt can 1 Check pj file name not be read 2 Make sure the file is accessible and in the right location verify the path settings PJ003 Unknown command 1 Check spelling and sy
28. ting processes and for group communication and synchronization operations C JOPI The Java Object Passing Interface User s Guide JOPI ANY TAG This is a static attribute that can be used as a wild card with the receive operations such that it will accept an object with any tag value d JOPI ANY CLASS This is a static attribute that can be used as a wild card with the e receive operations such that it will accept an object of any class type JOPI ANY SOURCE This is a static attribute that can be used as a wild card with the receive operations such that it will accept an object from any source The static attributes are useful for receive operations where the tag class type and or source are not statically determined before run time For example if a process needs to accept the first response that arrives from any one of multiple processes then it cannot specify the source As a result it uses the J OPI ANY SOURCE to accept any incoming object Methods The JOPI class provides a number of methods for different operations in parallel and distributed programming Many of these support explicit exchange of objects among the processes in synchronous and asynchronous modes 1 Synchronous blocking point to point operations a send This method sends an object from one process thread to another When it is used it blocks the sending process until the message has reached its destination The user needs to specify the target
29. users through the client services a pjava filename pj gt This command is used to initiate a user job start execution of the parallel program This will deploy the user processes on the requested number of processors and start running When the user runs this command the client services takes the user job along with all the necessary information to start that job and puts it in an object This object is then passed to the agents for deployment and execution As 13 JOPI The Java Object Passing Interface User s Guide shown earlier the schedule used for running the user job can be specified by the user or left to the scheduler to generate For this command to work a user file pj must be created to identify the user program classes and the schedule for running the program pingAgent all agentname gt This is used to list the available agent s and their status Active or Inactive on the system If an agent name is given the status of that agent is checked and displayed The all option will make the command check all the agents and display the full list of agents Not specifying any option will default to all The status of an agent is either Active indicating that it executing and ready to accept user jobs or Inactive indicating that it is down and not available for executing user jobs listThreads all agentname gt This is used to list all active threads on the agent s The user can specify a specific agent or all agent
30. vide information about other past receive operations Tag_no mp receiveTag d print This method is similar to the regular print methods in Java except that the output is directed to the client station where the user job was initiated This allows for all screen output to be available on the user console The format used in this method is exactly the same as in the regular print method in Java mp print String msg e close This method is used at the end of the program to end the JOPI interface Using this method will ensure that the program will correctly exit and all processes related to it will be terminated mp close Example In the figure below we illustrate JOPI s API usage Please note that the line numbers are only for illustration purposes and that they are not part of the program This program simply sends a message Hello World to all processes that will receive and print that message along with the process identification number In line 10 an instance of the JOPI class called mp is instantiated In line 11 mp myPID is used to get the current process ID Line 15 sends the string object to other processes String in Java is a serializable object therefore it can be directly sent using JOPI send method In line 20 the other processes issue a receive to receive the object In this case we used J OPI ANY TAG and JOPI ANY CLASS to accept any object with any tag value In many other cases the user may need to explicitly spe
Download Pdf Manuals
Related Search