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Parallel Object Programming in C++ User and Installation Manual

1. A parallel object method cannot return a memory address exception see fig 3 4 Sequential classes used as parameter must derived from POPBase and the programmer must implement the Serialize method Only scalar parallel object and POPException exception types 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 The specific POP C end of line delimiter popcend1 must be used with the cout operator instead of the standard end1 delimiter It is currently not possible to launch simultaneously the same POP C program same executable in the same directory because of conflicts between temporary files generated by the POP C run time Compiling and Running 31 CHAPTER 4 Compiling and Running lf PQP 4 1 The POP C compilation 4 2 3 Running POP C programs process 4 3 Compiling a complex POP C 4 2 Compiling a simple POP C program program 4 2 1 Compiling 4 2 2Compiling the parallel classes 4 1 The POP C compilation process 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
2. The POP C runtime system provides automatic placeholder selection object allocation and object destruction This automatic 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 using a resource discovery algorithm 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 The POP model has been conceived under the belief that for such environments high performance can only be obtained if the two following conditions are satisfied e The application should be able to adapt to the environm
3. 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 46 Appendix A Command Line Syntax A 2 Running an application To run aPOP C application type the following command where pope options is one or several of the options described below popcrun objects config popc options 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 Appendix B Runtime environment variables 47 Appendix Environment variables Pop d The following environment variables affect the default behaviors of the POP C runtime To ensure proper execution of parallel objects these variables are set during the installation process make install Manipulation of these variables can lead to an unstable POP C environment and should be done only if your are an expert of the inside of the POP C tool These variables can be manipulated directly or using the scripts popc runtime env located in the directory lt install dir gt etc If you expect problems with the values of these variables re run the installation process see section 5 3 POPC LOCATION Location of installed
4. FO A l Compiling an UNE 45 Acd Running an application soseer ii ni iii 46 Appendix B Environment variables ooonoonocooonnconnncconanononnnonnancconacononaconcncccocaconoaa f 7 Overview 1 CHAPTER 4 Overview SI 1 1 Introduction 1 4 Structure of this Manual 1 2 The POP Model 1 5 Additional Information 1 3 System Overview 1 Introduction Programming large heterogenous distributed computing environments such as GRID P2P Cloud or even large supercomputers is a challenging task POP C is an implementation as an extension of the C programming language of the POP Parallel Object Programing model first introduced by Dr Tuan Anh Nguyen in his PhD thesis 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 to create parallel applications based on the MPMD Multiple Programs Multiple Data paradigm The POP C programming language extends C by adding a new type of objects we call parallel object POP C has been designed to ease as much as possible the development of efficient distributed applications using the powerful object oriented programming paradigm and to allow existing C C programs to be easily transformed in efficient parallel applications 1 2 The POP Model The POP model extends the traditional object oriented programming paradigm by adding the minimum necessary functionality to allow for a
5. caught somewhere else in the calling stack The implementation of exceptions in non distributed applications where all components run within the same memory address space is rather straightforward 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 a Ery E method 02 method int x catch co AA throw handle exception rene Deg Figure 3 10 Exception handling example 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 User Programming Manual 29 with the UNKNOWN exception code If the e
6. communication protocol is socket or HTTP socket having higher priority There is an implicit and operator between the different od parclass Bird public Bird float P od power P od memory 100 60 od protocol socket http Figure 3 1 Object descriptor example Object descriptors are used by the POP C runtime system to find a suitable resource for the parallel object with the exception of the od url object descriptor which directly specifies the name of the resource to use If no suitable resource is found to execute the objet then an exception is raised see section 3 4 3 If no object description is indicated the POP C run time will use an unspecified internal procedure to decide where to instantiate this object 3 3 Object Layout 3 3 1 The pack directive The POP C compilation process generates several executable files see section 4 1 One of them is the main program file which is used to start the application Other executable User Programming Manual 23 files contain the implementations of the parallel classes for a specific platform A given executable file can store the implementation of one or several parallel classes Programmers must indicate to the POP C compiler which parallel classes to store in which executable file This is done by inserting the pack directive in the source file of the implementation of the parallel classes the cc file Stack Stack A Stack
7. in will be used Which local user you want to use for running POP C jobs The last questions are very advanced features of POP C They allow to configure POP C for very specific situations of for testing purposes If you are note a great specialist of POP C just type lt return gt to keep default values You can specify the name of the script which will submit jobs parallel objects on the local machine The name of the script can be given by answering 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 2 matching any wildcards For example given communication pattern socket 160 98 http e 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 Installation Instructions 41 Ifthe remote object access point is socket 160 98 20 54 33478 http 160 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 v
8. push Stack iPOD ierk T pack Stack Queue List Figure 3 4 Packing objects into an executable file Figure 3 4 shows a 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 it must store the executable code of classes Stack Queue and List in the same executable file This does not prevent the programmer to put if desired the source code of the parallel classes Stack Queue and List in separated source code files The rule to apply 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 file As a consequence the source file of the implementation the cc file of a parallel class is usually terminated by the pack ParClassName directive There are some specific cases where it is required to put several parallel classes in the same executable files For example when a parallel class inherits from other parallel classes In such a situation mother and child classes must be put in the same executable file Failing to do so will lead to the following error at execution time Out of resource errno 10001 which indicates that the POP C run time is not able to find the needed resources namely the executable code of the parallel classes u
9. the remote resource down or any other causes The interface of POPException is the following class POPException public const POPString Extra const int Code const void Print const The Code method returns the corresponding error code of the exception The Extra method returns a POPString associated with the exception Finally the Print method prints a text describing the exception All exceptions that are instances of parallel objects are propagated by reference Other exceptions are transmitted to the caller by value 3 5 Limitations There are several limitations to the current 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 30 User Programming Manual memory Some of these limitations have already been presented but a summary of these limitations for the current version v2 5 is listed below A parallel class cannot contain public attributes A parallel class cannot contain class attributes or methods 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 reference or output parameters Parallel objects can only be passed by reference Global variables exist only in the scope of parallel objects pack scope
10. until another method triggers the event by calling raise If the waiting method possesses 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 3 E E EE Figure 3 9 Example with one producer and two consumers using the parallel class of figure 3 8 28 User Programming Manual 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 actually reactivated The typical use of locks is to implement critical sections when several methods can modify at the same time a shared attribute One of the most typical usage of events is to synchronize the producer consumer situation Figure 3 8 presents an example of usage of event with the POPSynchronizer class and figure 3 9 shows an example of usage of this example 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
11. Do not forget that you need to have write access to the current directory This command can take several minutes 5 3 3 POP C Setup If the compilation completes successfully you can install POP C in the lt install dir gt by entering the command make install Note you must have read write access to the lt install dir gt Shortly before the installation finished the system will automatically launch the popc setup script This script can be re launched at any time after the installation to modify the POP C set up The set up is divided in two parts the first one configures your POP C installation and the second one creates startup scripts which are used by POP C applications Standalone installation At this time you will be able to choice if you want to do Standalone installation or POP Community installation The following question is displayed DO YOU WANT TO MAKE A SIMPLE INSTALLATION y n By answering y you make an standalone installation of POP C 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 If you need to change the set up you can at any time launch the POP C set up again by typing make install and by answering n to this question Note instead of re launching make install you can also launch the script popc_setup This will be explained later in this document When the installation is terminated the following m
12. OP EE tidad iii csi ite ee 19 3 2 8 Standard output in POP C ooo cececssssssecserestecenecescsesesenesesscnteensececcsenssenesensentecensces 21 3 2 9 Object Description Sensis EENS EeE eene 21 3 3 Object Lay ut a ii 22 33l The pack directive meridiano REA ROR E RER ERE 22 3 3 2 Class Unique Identifier piniienn a E NEEN NENE ENSE 24 3 4 POP C standard library siii 25 3 4 1 The POP String TE 25 3 4 2 Synchronization and locks ooooccnoconocononononononcnononnnocononancnnnonancon nono no non onn rra rnnnrcan crac 25 EE AE e E 28 AA nn A NE E 29 4 Compiling RE E A 4 1 The POP C compilation EE 31 4 2 Compiling a simple POP C program 31 Se 32 4 2 2 Compiling the parallel classes 32 4 2 3 Running POP C programs siscsnineiennrneniininseie iinis nenies 32 4 3 Compiling a complex POP C Pro ie 33 2 Content 5 Installation Instructions cccccscccccssssccccsssscccccsscccccccsscccccescccecesccscsssessscsssesses JD DL POAC TT EE 35 5 2 BETOTE TOSTADAS IA EA AAA RAEE AAA AAA 35 EN DE UE 35 SET E EE UE 36 5 2 3 Downloading the POP C Distribution ooooocciocononoconcooncnononancon nono nononononcnnnonancon ccoo nono 36 SE installa a id ooo 37 53 Prepating compilation cer a a E a IE li a e 37 5 3 2 Compiling POP C tools ennen iia a aeia 38 AO PACA odio 38 5 4 Testing Installation 42 5 5 TM ee 42 Appendix A Command Line Syntax ccccoconncncononnccononacnnnnacoconncncncnnocanaconacanccnoncccccoc
13. OPString public Constructors POPString POPString const char x POPString const char x int n POPString std string x POPString const POPString amp x Destructor POPString 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 Figure 3 5 The POPString class 3 4 2 Synchronization and locks POP C provides the concurrent semantic conc for method invocations see section 2 4 As a consequence we can have several methods which are concurrently executed inside the same parallel object If these methods try to access the same data attribute of the object 26 User Programming Manual this can lead to race conditions and can require a way to synchronize the access to the share data This is a standard problem in concurrent systems POP C provides a standard solution to this problem thanks to the POPSynchroni zer class Figure 3 6 shows the declaration ofthe POPSynchroni zer class class POPSynchronizer public POPSynchronizer lock unlock raise wait Figure 3 6 The POPSynchronizer class A synchronizer is an object used for general synchronization of concurrent execution inside a parallel object Every synchronizer can handle a lock and an event Locks and ev
14. 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
15. Parallel Object Programming in C User and Installation Manual Hes so Haute Ecole Sp cialis e de Suisse occidentale Fachhochschule Westschweiz University of Applied Sciences estern Switzerland 0009090 Y SEA QP www The POP C Team Grid amp Cloud Computing Group http gridgroup hefr ch popcinfo hefr ch Software Version 2 5 Manual Version 2 5 a Parallel Object Programming in C User and Installation Manual Manual version 2 5 a October 2012 Copyright c 2005 2012 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 V
16. alentin Cl ment David Zanella Marcelo Pasin Laurent Winkler Nicolas Brasey Problems or questions concerning POP C can be submitted on the POP C web site or be sent by e mail to popcinfo hefr ch Table of content Table of content nn UN Riet ve A PP cand ERAEN ARSS 1 1 2 The ge 1 O alo PM A io O Eie ERREN e TE E i ERSE EEE 2 LA CR EE 2 l 5Additional Informations o 3 2 The Parallel Object Model eooessooessseesssoocessoessssocsesoosessoeesssocessoosessseesesocseesossss D PAA EKOT AD Tn EE 5 2 2 The Parallel Object Mod 5 2 3 Shareable Parallel a EEN 6 2 4 Methods Invocation Semantics a 6 A II NEG 8 2 6 Requirement driven Parallel ODjECtS c lt caccccscescnssessscnascessendsecsnncesecesunsseceseevsaesseunssavonnedandenunsves 8 3 User Programming Manual sicsssscsssssscsssccsssssesentesostecssvssreinsesosavsssescasssccentsssseeessss LA A EE 11 SEET 12 3 21 Parallel Classes incidir iii se ccethsencetsabadentanavhestse eceilaenaelashatysapatareanandeds 12 3 2 2 Creation and Destructiom xscoccccceseccascecsctsnssssdceetessccentaesscvunconsevcesccdesvaasdcondcoctsonscebtccaseese 12 3 2 3 Parallel Class Method Invocation ccccccecsessseeesecesceeeeeeneeesecseecsaececneeeseneseaeeaeeaeens 13 3 24 WEE e CN 14 3 2 5 Marshalling complex argument ceccesccscesceeseeeceececeeseesececeaecaeeeeteeseaecaaeeaeeaeeaeenaes 16 3 2 6 Inheritance in POP CA occasion ronaldo andado beds 19 3 27 Usage of Chi S In P
17. allel class 2 the argument is NOT a parallel class These two situations are presented separately in the next two paragraphs The argument is not a parallel class In such case the argument can be any basic or structured type of C or a sequential class It has to be noted that input arguments are only transferred from the caller object to the callee object when in case of a synchronous method invocation output arguments are only transferred back to the caller Input output arguments are of course transferred in both direction Because the caller and the callee do not use the same memory address space some rules applied for arguments of methods of parallel classes e if the method is asynchronous arguments must be input only arguments cannot be pointers or passed by reference the returned type of the method must be void e if the method is synchronous constant and passing by value arguments are input only arguments passed by reference 4 are considered as both input and output the returned value return is output only pointer arguments are normally not authorized see section 3 2 5 for exception Programmers can optionally modify these rules to help the POP C compiler to generate more efficient code by specifying which arguments have to be transferred and returned This is done by using specific POP C directives in the argument information block The directives in for input out for output or both in
18. amp s F3 main program int main int argc Chart argv struct data a Toto x x set 1 int res x get a printf Value are d d f n res a i a f Figure 3 2 Simple arguments The argument is a parallel class Only references using the amp modifier to parallel classes can be passed as parameter to any methods method of parallel or sequential classes This restriction directly derived from the semantic of parallel classes Indeed passing a parallel object by value means to create a copy of this parallel object We want to avoid such a copy because on one hand it is usually not what the programmer wants and on another hand we should find a new 16 User Programming Manual computing resource for this new parallel object Passing parallel objects by reference allows several objects parallel or not to share the reference of the passed parallel object This is the way POP C implements the concept of shareable parallel objects 3 2 5 Marshalling complex arguments When an argument of a method of a parallel class is not a simple argument see section 3 2 4 and is not a parallel object it must be marshaled or serialized at the sender side and demarshaled or deserialized at the receiver side The programmer must indicate to the POP C run time how to marshal and demarshal it This must be done in two cases e the argument is an instance of a sequential class e the argument is a pointer this i
19. are not anymore strictly equivalent Indeed the instruction this gt aMethod calls the method aMethod taking into account the semantic of aMethod sync async seq etc In such a case you must take care because you can easily cause deadlocks It is the case for example if the method which makes the call and the called method have both the seq semantic The instruction aMethod without the this does not take into account the semantic User Programming Manual 21 of the method because the call is considered as an internal call to the method and is handled as a normal C method call Note Usage of this in parallel classes is complex because the detection of possible deadlocks can be very difficult It is a good programming practice to limit as much as possible usage of this in parallel classes When pointing toward a parallel class this can be use as effective parameter for a method call Nevertheless the POP C limitation which imposes that pointers arguments are not authorized applies In addition as parallel object can only be passed by reference see section 3 2 4 only amp this can be really passed as an effective argument 3 2 8 Standard output in POP C To write on the standard output stdout POP C programs can use the standard C function printf and the standard C cout operator The printf function behaves exactly as in traditional C programs In particular if a printf is executed in a remotely ex
20. ariable 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 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 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 have read write access to this directory Enter the temporary directory for intermediate results As for standalone installations when the installation is terminated the following message is displayed IMPORTANT Do not forget to add these lines to your bashrc file or equivalent POPC_LOCATION lt install dir gt export POPC _LOCATION lt install dir gt PATH PATH POPC_LOCATION bin POPC_LOCATION sbin Add these lines in the corresponding files to allow POP C to access neede
21. bjects 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 behaviors for the execution of the method as described below The Parallel Object Model 7 Interface semantics the semantics that affect the caller of the method gt Synchronous invocation the caller waits until the execution of the called 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 to 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 24 o 03 Figure 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 com
22. cult 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 gt myobj2 gt myobj3 myobj4 Figure 4 2 Parallel classes with dependencies Since each class contains some internal POP C classes which are transparent to the programmer 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 myob34 on the example of the figure 4 2 and then to compile each parallel class in reverse order To compile any class in the chain we needs the parallel class which is directly after the one we are compiling in the chain of dependency To do so we need to 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 When compiling a parallel class without generating the executable code using the gcc 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 reloca
23. d tools or refer to section 5 5 to learn about an easy alternative to do it 5 4 Testing Installation Several test programs allowing to test your installation are provided with POP C distributions These programs are located at 42 Installation Instructions lt source dir gt test This directory is copied in the lt instal dir gt during installation thus it is also available at lt install dir gt test Be aware that to run test programs you need to have execute X permission on the directory you are using to run test By default it is not the case for the lt install dir gt Before running tests you have to start the POP C deamon we call the Job Manager The Job Manager is used by POP C to find and allocate computing resources during executions of POP C programs Refer to section 5 5 to learn how to launch the Job Manager Then run the tests by typing runtests all You also can run each test individually Type runtests help for more information 5 5 The Job Manager As mentioned at the end of section 5 3 3 it is required that you define paths by adding lines to your login file files like profile bashrc cshrc etc To ease this task the POP C installation provides you a script which makes this work for you You just have to call this script at the end of your login file This script is provided for C shells and Bourne shell in the following corresponding files lt install dir gt e
24. dicate if the argument is input only output only or both respectively The optional argument information block should appear User Programming Manual 15 between braces and right before each argument declaration see figure 3 2 When the caller and the callee run on different processor s architectures data must be encoded to a standard format before being transferred and decoded at reception The programmer can inform the compiler of the standard format to use for the encoding see od encoding in section 3 2 9 By default data are not encoded i e raw values are transferred Simple arguments are single arguments of basic C type such as int float double bool etc or structures that only contain basic types no pointer no array no class Simple arguments can be transferred without other precaution than a possible encoding Figure 3 2 shows an example of methods having only simple arguments In this example the out directive is used to indicate to the compiler that the second argument of the method get does not need to be sent to the method but only returned Argument of complex types such as arrays pointers or sequential class argument must be serialized or marshaled prior to be sent or returned to from remote objects How to marshal demarshal complex argument is presented in the section 3 2 5 parclass Toto struct data int i float f async seq void set int i sync seq int get out struct data
25. e programmers have to explicitly supply the number of elements pointed by that data pointer using the special POP C directive size in the argument information block Programmers can also indicate which specific function must be used for marshalling demarshalling the argument using the proc directive The size and proc directives must be inserted in the argument information block together with the in or out directives if any Be aware that void pointers void cannot be used as arguments of parallel object methods 18 User Programming Manual parclass Table void sort in out size n int data int n bi main program Table sales int amount 10 sales sort amount 10 Figure 3 4 Marshalling demarshalling of an array argument Figure 3 4 contains an example of a method sort that has two arguments an array of integer data for input and output and its size the n parameter struct Speed float val int count ka void marsh POPBuffer amp buffer Speed amp data int count int flag POPMemSpool tmpmem if flag FLAG MARSHAL buffer Pack amp data count 1 buffer Pack data val data count else buffer UnPack amp data count 1 performing temporary allocation before calling UnPack data val float tmpmem gt Alloc data count sizeof float buffer UnPack data val data count parclass Engine async seq void accelerate proc mars
26. ecuted parallel object the POP C run time routes the text to print on the computing resource which run the main program i e the local computer Please notes that the text is effectually routed to the local computer only when the end of line delimiter n is printed Usage of the C cout operator is also possible with POP C Nevertheless due to the fact that the text has to be routed to the local computer that one which run the main one must use a specific POP C end of line delimiter instead of the standard C endl operator Failing to do so will prevent the message to be printed The specific delimiter to use is popcendl Below is an example of usage of the cout operator in POP C cout lt lt A message to print by a parallel object lt lt popcendl 3 2 9 Object Descriptions Object descriptions have been introduced in section 2 6 and are used to describe the resource requirements for the execution of a given 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 and before the instruction terminator operator The syntax of an object descriptor the 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 fol
27. ent e The programming environment should somehow enables objects to describe their The Parallel Object Model 9 resource requirements The POP allows the programmer to integrate 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 name we specify the exact name of the resource we want to use to run the object In such a case there is no need to run the resource discovery algorithm The minimum required computing power needed to run the object e The minimum amount of memory needed to run the object e The expected minimum communication bandwidth and maximum latency An object description can contain several items Each item corresponds to a type of characteristics of the desired resource Items are classified into two types strict item and non strict items A strict item means that requirements must be fully satisfied If no satisfying resource is available the allocation of parallel object fails Non strict items give the system more flexibility for selecting a computing resource Resource that partially match the requirements are acceptable although a full qualification resource is preferable In such a case to values are provided in the resource requirement statement the desi
28. ents 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 the execution of the calling method until another 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 1ock will eventually return When creating a synchronizer by default the lock is open A special constructor is provided to create synchronizer with the lock already closed Figure 3 7 shows an example of usage of locks with the POPSynchroni zer class parclass Examplel private POPSynchronizer syn int counter public syne conc int getNext syn lock int r counter syn unlock return r Figure 3 7 Using locks with the POPSynchroni zer class User Programming Manual 27 parclass Example2 private int cakeCount boolean proceed Synchronizer syn public void produce int count cakeCount count syn lock proceed true syn raise syn unlock void consume syn lock if proceed syn wait syn unlock can use cakeCount from now on Figure 3 8 Using event with the POPSynchroni zer Class Events can be waited and raised Calls to wait cause the calling thread to pause its execution
29. erate the object map file which contains the list of all compiled parallel classes used by the application Indeed as POP C allows to run distributed application in heterogenous environments we have to compile parallel class for each potential computing unit architectures where we want instances of this parallel class be able to run Therefore the object map file contains for each parallel class for which architecture the compilation has been done and the location of the corresponding Compiling and Running 33 executable file obj file With POP C it is possible to get this information by executing the object executable file with the option 1istlong Example for the myClass parallel class if we type myclass obj listlong the following message will be displayed myClass i686 pc Linux home myloging popc test myclass obj which indicates that the file myclass obj contains the executable code of the parallel class myClass compiled for 1686 pc 1inux architecture and that the name and path of the file is home myloging popc test myclass obj To generate the object map file we simply redirect the output to the object map file myclass 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 poperun popcrun obj map main 4 3 Compiling a complex POP C program The compilation is a little bit more diffi
30. essage is displayed IMPORTANT Do not forget to add these lines to your bashrc file or equivalent POPC_LOCATION lt install dir gt export POPC _LOCATION lt install dir gt PATH PATH POPC_LOCATION bin POPC_LOCATION sbin Add these lines in the corresponding files to allow POP C to access needed tools or refer to section 5 5 to learn about an easy alternative to do it POP Community installation By answering n you can make a POP Community installation POP C allows for different ways to create a POP Community In this document we will only present the most basic and most used way A typical POP Community is a set of computers sharing disks space and users accounts using for example NFS Network File system In addition each Installation Instructions 39 node of the community can start an SSH session on any others node of the POP Community but each node does not need to know the addresses of all others nodes of the POP Community The only constraint to fulfill is that the graph created by linking node A to node B if A knows the address of B is a bidirectional connected graph At any time a new node can join the POP community by contacting a node already belonging to the POP Community and by exchanging public SSH keys and IP addresses Figure 5 1 shows an example of POP Community a POP Community example your neighbour computer 1 your computer other computers inside POP Community your neighbour compute
31. figure 4 1 Ss POP C parser ANSI C compiler POP C Services Libraries POP C Tool Figure 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 Compiling a simple POP C program In this section we illustrate the POP C compiling process by describing how to compile a simple POP C program We assume that our simple POP C program is constituted of three source files e main cc contains the main program 32 Compiling and Running e myclass ph contains the declaration the header of the parallel class myClass e myclass cc contains the body the implementation of the parallel class myClass It has to be noted that by convention header files of parallel classes have the ph extension instead of h as for usual classes in C 4 2 1 Compiling We have to generate several executables one for the main program main and one for each parallel class declared in the program which by convention have the extension ob POP C provides the command popcc to compile POP C source code To compile the main program we use the following command popcc o main myclass ph myclass cc main cc Note tha
32. guage and compiler POP C essential service abstractions POP C services POP C services Customized service for Globus for other toolkit implementation Globus Toolkit other toolkit toolkits Computational environment Figure 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 1 4 Structure of this Manual This manual has five chapters including this introduction The second chapter explains the POP programming model The third chapter is the reference programming manual of POP C It is the most important chapter It describes the POP C programming syntax and semantic 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 Beginners can also consult the Getting started manual which is available on the POP C website and show how
33. h const Speed amp data ie Figure 3 5 Marshalling demarshalling of complex struct argument User Programming Manual 19 Figure 3 5 illustrates a more complex example of usage of the proc directive In this example the programmer needs to allocate temporary memory space before serving the invocation request This memory space will be automatically freed by the system after the invocation finished if the method Alloc provided by the class POPMemSpool of the POP C environment is used to do this temporary memory allocation The declaration of the Alloc method of the POPMemSpoo1 class is given below class POPMemSpool public void Alloc int size 3 2 6 Inheritance in POP C Inheritance is fully supported in POP C Nevertheless it is a little more tricky than in standard C because there are two different types of classes the parallel and the sequential C standard classes The following general rule applies in POP C Parallel classes can only inherit from parallel classes and sequential class can only inherit from sequential classes Inheritance between sequential classes is strictly identical to inheritance in pure C On a syntactic point of view inheritance between parallel classes is identical to inheritance between sequential classes Nevertheless due to the way parallel classes behave some specific knowledge is required to correctly use inheritance between parallel classes This knowledge mainly conce
34. h the data received in buf must be demarshaled Pack Unpack methods offer the possibility to marshal demarshal several data in one call The n parameter User Programming Manual 17 contains the number of data of type Type to marshal demarshal This feature is especially useful when passing arrays of objects Figure 3 3 shows an example of marshalling demarshalling of the Speed sequential class class Speed public POPBase public Speed virtual void Serialize POPBuffer amp buf bool pack float val int count F7 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 amp data Figure 3 3 Marshalling demarshalling of sequential class argument The best way to transfer complex information to a method of a parallel class is to use sequential classes This is the most object oriented approach Nevertheless in some cases for reasons of simplicity arrays arguments which are pointers are used In such a case it is not possible to use the Serialize method as explained in the previous section because the parameter does derive from the POPBase class Data pointers in C are ambiguous pointer to data or starting address of an array Therefor
35. ine Syntax 45 Appendix Command Line Syntax L P P N A 1 Compiling an application In this appendix only options specific to POP C are presented However all options of the C compiler your are using by default g are also available popce cxxmain object typell 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 pope static Link with standard POP C libraries statically popc nolib Avoid standard POP C libraries 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 popedir 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
36. ined 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 popcpp lt version subversion gt tar gz 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 only for POP C version older that 2 5 configure CPPFLAGS DARCH_MAC Default options are install dir gt usr local popc assuming you did note defined another directory in POPC_LOCATION Remember that you must have write access to this directory If you want to install POP C in another directory use use the parameter prefix lt install dir gt configure prefix lt install dir gt or if the variable POPC_LOCATION has been defined configure prefix POPC_LOCATION Several other parameters are available with the configure command but they are usually only useful for complex POP C installation More details about the available options can be found by typing the command configure help 5 3 2 Compiling POP C tools When configured you can compile POP C tool by entering the command 38 Installation Instructions make Note
37. lowing od resNum exact od resNum desired lbound od resString resource resNum power memory network resString protocol encoding url 22 User Programming Manual exact desired and lbound terms are numeric expressions and resource is a null terminated string expression of type POPString see section 3 4 1 The semantics of those expressions depend on the resource requirement specifier the keyword corresponding to resNum Or resString The 1bound term is only used in non strict object descriptions to specify the strict lower bound of the acceptable resource requirements when desired correspond to desired value In the resource string the different options must be separate with one blank The priority of options is position dependent the first option 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 z1ib 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
38. mers 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 Note Even is the problem mentioned above can theoretically occur the POP C team never reported it However it is a good programming practice to indicate classuid The POP C compiler shows a warning message when no classuid is specified for a parallel class User Programming Manual 25 3 4 POP C standard library The POP C standard library offers classes and functions which can be useful or even necessary to write complex POP C programs This library in automatically include therefore no include directive is required 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 As for basic C types instances of POPString class are automatically marshaled demarshaled by POP C 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 POPSt ring class are shown in the figure 3 5 class P
39. n 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 to create the new concept of parallel class By instantiating parallel classes we are able to create a new category of objects we will call parallel objects in this document Parallel objects are objects that can be remotely executed They coexist and cooperate with traditional sequential objects during the execution of the application Parallel objects keep advantages of the object orientation programming paradigm such as data encapsulation inheritance and polymorphism and adds new properties to objects such as Distributed shareable objects 1 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 2 Overview Dynamic and transparent object allocation Various method invocation semantics 1 3 System Overview Although the POP C programming environment focuses on an object oriented programming model it also includes a runtime system which provides the necessary services to allow 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 lan
40. ncludes the case of arrays When the argument is an instance of sequential classes this arguments must be an instance of a class which derive from the POPBase sequential class provided by the standard POP C library 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 effective parameters which are instances of this class As shown above the method Serialize requires two arguments e the buf argument that stores the marshaled data object e 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 standard library provides a set of Pack UnPack methods for all basic C types 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 declaration of the POPBuf fer class class POPBuffer public Below Type refers to any basic C type void Pack const Type data int n void UnPack Type data int n be For the method Pack the parameter data contains the address of the data to marshal into buf when in the case of the UnPack method the same parameter data contains the address of the data into whic
41. nning The default name for this directory is tmp This directory will be asked during the installation process e We call this directory lt temp dir gt in the present document 5 2 3 Downloading the POP C Distribution POP C is distributed in form of a tar file with the following naming convention popcpp lt version subversion gt tar gz You can download the tar file either e Directly from the website recommended of the GridGroup who develops and maintains the tool POP C http gridgroup hefr ch popc doku php download e From freash meat http freshmeat net projects pop c 2 The name of the package is distribution dependent For example the zlib devel package is named on Fedora red hat based z1ib devel on Ubuntu debian based 1ib1g dev 3 This package is only necessary for those who wants to modify the POP C tool itself 4 This package is only necessary if you want to install POP C over Globus This installation is not described in the present document and is not supported since version 2 5 of POP C Installation Instructions 37 POP C is available for Linux and MacOS Download the version corresponding to the OS which run on the computer you want to install POP C POP C is currently not available for Windows 5 3 Installation This section describe how to install POP C without any special option It s also possible to customize the installation Customized installation is expla
42. nted 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 programming language is an extension of the 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 existing C C programs and libraries can be parallelized without too much effort Changing a sequential C C application into a POP C distributed 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 computing unit to execute the remote object programmers can add object description information to each constructor of a parallel class see sections 2 6 and 3 2 9 As presented in chapter 2 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 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 prese
43. nts main tools available in the POP C standard library A complete example of a POP C program can be found in the POP C Getting Started Manual available on the POP C website 12 User Programming Manual 3 2 Parallel 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 As in C developing POP C programs mainly consists of designing and implementing classes The declaration of a parallel class in POP C is very similar to the declaration of standard sequential class in C but the declaration is introduced by the keyword parclass instead of the keyword class Example parclass ExampleClass methods and attributes F 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 derived from other parallel classes see section 3 2 6 and methods of a parallel class can be declared as overridable virtual methods Parallel classes are very similar to standard C classes Nevertheless some restrictions applied e All data attributes must be protected or private public is not authorized e Parallel objects must not access any global variable e Programmer defined operators are not all
44. of POP C see section 5 3 3 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 installing and running POP C the following packages must be installed e A standard C compiler g 36 Installation Instructions e the zlib devel package Optional packages are e the GNU Bison e the Globus Toolkit 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 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 e 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 ru
45. owed e There are no methods that return memory address references see section 3 2 5 e A parallel class can only derived from other parallel classes e Class static attributes or methods are not allowed These restrictions are not major issues in the object oriented programming paradigm In some cases they can even 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 locating a resource satisfying the object description resource discovery transmitting and executing the object code establishing the communication transmitting the constructor arguments and finally invoking User Programming Manual 13 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 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 Nevertheless the programmer does not have to deal with this complex mechanism because the POP C run time automatically manages parallel objects life time using an internal reference counte
46. pletion 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 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 Figure 2 3 illustrates the different method invocation semantics Sequential invocation Segl is served immediately running concurrently with Conc1 Although the sequential invocation Seq2 arrives before the concurrent invocation Conc2 it is delayed due to the on going execution of Seqi no order between concurrent and sequential invocations When the mutex invocation Mutex1 arrives it has to wait for 8 The Parallel Object Model previously called and running methods to finish During this waiting it also blocks other invocation requests arriving afterward such as Conc3 until the mutex invocation request completes its execution atomicity and barrier ETIE f CAE Figure 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
47. r A null counter value will provoke the object to be actually destroyed Syntactically the creation and the destruction of a parallel object are identical to sequential object in C A parallel object can be implicitly created by declaring a variable of this parallel class or by using the standard C new operator As for sequential objects in C parallel objects created using the new operator must be explicitly destroyed using the delete operator when implicitly created parallel objects are automatically destroyed at the end of the block where the variable has been declared Below is a example of declaration and creation of parallel objects parclass ExampleClass ExampleClass default constructor ExampleClass x create the parallel object x ExampleClass y 5 create 5 parallel objects ExampleClass p declare a pointer on a parallel object p new ExampleClass create the parallel object p 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 Public attributes are not allowed because it leads to share memory which is in contradiction with the distributed computing paradigm where memory is distributed different memory address space For each method the programmer can define the invocation semantics by placing appropriated keywords before me
48. r 2 Figure 5 1 Example of a POP Community To allow POP C to create the POP Community you will have to answer during the installation to several questions which are detailed below Note if you answer by typing the lt return gt key to all questions the effect will be exactly the same as making a standalone installation As mentioned above in a POP Community the computing resource topology is a connected graph and any computing resource can join the environment by register itself to other node s in the community its neighbor nodes s To make your local computer joining a community you have to select one or several nodes belong to this community and to make them your neighbors You must at least enter one neighbor node by answer to the following question Enter the full qualified neighbour host name or IP address You can give the IP address or the name the of machines which are in the POP community you want to join If you are installing POP C on the first machine of a POP Community you still can enter addresses of machines where you intend to install POP C and that will be part of the same POP Community You can also leave neighbor list empty but in such a case you will have to re run the POP C set up later in order to make your machine joining the POP Community When you have entered all the names of your neighbor nodes just type lt return gt to 40 Installation Instructions terminate the process Note do no
49. re 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 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 See section 3 2 4 for more details on passing arguments worker input data flow y worker input EA user data server workstation worker Figure 2 1 A scenario using shared parallel objects 2 4 Methods Invocation Semantics Syntactically method invocations on parallel objects are identical to those on traditional sequential o
50. red one and the strictly minimum one For example a certain object has a preferred performance 150MFlops desired although 100MFlops strict minimum is acceptable non strict item but it needs memory storage of at least 128MB strict item The evaluation of object descriptions are done at run time during the parallel object creation The programmer can provide an object description with 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 9 10 The Parallel Object Model User Programming Manual 11 CHAPTER User Programming Manual POP 3 1 Introduction 3 2 8Object Description 3 2 Parallel Objects 3 3 Object Layout 3 2 1 Parallel Classes 3 3 1The pack directive 3 2 2Creation and Destruction 3 3 2Class Unique Identifier 3 2 3 Parallel Class Method Invocations 3 4 POP C standard library 3 2 4Passing arguments 3 4 1The POPString class 3 2 5Marshalling complex arguments 3 4 2 Synchronization and locks 3 2 6 Inheritance in POP C 3 4 3Exceptions 3 2 7 Usage of this in POP C 3 5 Limitations 3 1 Introduction The POP programming model presented in the chapter 2 is a suitable programming model for large heterogenous distributed environments but it should also remain as close as possible to traditional object orie
51. resented in this chapter provides an object oriented approach for requirement driven high performance applications in a distributed heterogeneous environment 2 2 The Parallel Object Model POP stands for Parallel Object Programming and POP parallel objects are generalizations of traditional sequential objects POP C is an implementation of this model as an extension of C POP C can instantiate parallel objects transparently and dynamically 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 6 The Parallel Object Model 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 presented in section 2 5 e Each parallel object has the ability to dynamically describe its resource requirement when created This featu
52. rns the usage of the pack directive see section 3 3 1 and the way the compilation of parallel classes with inheritance must be done see section 4 3 3 2 7 Usage of this in POP C In C the identifier this provides a pointer to the current object It can be used 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 In this example the instruction this gt aMethod 20 User Programming Manual 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 Gita Xx class titi public void aMethod void toto setTiti titi t void titi aMethod toto t t 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 In this case the behavior is exactly the same than in standard C this is a pointer to an instance of a parallel class In this case the instructions this gt aMethod and aMethod
53. sually the mother class to execute the object Below is an example of parallel classes inheritance in POP C In this example we have a parallel class Child which inherits from a parallel class Mother The file mother ph mother cc child ph and child cc contain respectively the declaration and the implementation of the parallel class Mother the declaration and the implementation of the parallel class Child 24 User Programming Manual File mother ph fragment parclass Mother public Mother File child ph fragment parclass Child public Mother Inherits from Mother public Child be File child cc fragment Child Child pack Child Mother Classes Mother and Child will be in the same executable file The file mother cc must not contain a pack directive as a pack directive already exists for this class in the file child cc 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 program there is a little risk that the same identifier is assigned to several different classes residing in different C executables but belonging to the same POP C program This will cause a program crash because the POP C run time use class unique identifiers to identify classes in side a program To avoid this problem POP C provides to program
54. t define your computer as your neighbor node 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 This is mainly used when installing POP C on the front end of a cluster In such a case indicate the number of computing node can the front end will manage Be aware that a multi core processor is considered as a single processor The next question is the number of parallel objects that can simultaneously run on the local machine Enter the maximum number of POP C jobs that can run concurrently default 100 Note The default value is 100 because in standalone mode all parallel objects run on the same machine Be aware that each parallel object is a full Unix Linux process The next question concern the amount of memory you want to allocate to POP C jobs You may not want to give all memory available So indicate in MB the maximum amount of memory you agree to allocate to POP C jobs Enter the available RAM for job execution in MB default 1024 As already mentioned each POP C object is Unix Linux process Therefore each process is owned by a specific user You can force the user under which the POP C jobs must run Of course you must have the rights to run processes under this username By pressing just lt return gt the user you are actually logged
55. t we have to explicitly compile the declaration of the parallel class the file myclass ph when in C we usually do not compile the header files h files This is a specificity of the POP C compiling process The o option has the same meaning than for standard C compilers introduce the name of the executable file 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 2 Compiling the parallel classes The compilation of the parallel classes are done using object option of the POP C compiler popcc object o myclass obj myclass ph myclass cc Again we have to explicitly compile the declaration of the parallel class This command will generate the myclass obj file which contains the executable code of the parallel class myClass The compiling process is now terminated and we produced two executable files main contains the executable code for the main program This executable will be launched and executed on the local machine when running the program e myclass obj contains the executable code for parallel objects which are instance the parallel class myClass This executable will be remotely launched on the processing unit that will run the parallel object 4 2 3 Running POP C programs To execute a POP C application we need to gen
56. table code without internal 34 Compiling and Running POP C classes The way to compile a POP C application with dependencies as illustrated on figure 4 2 is shown in figure 4 3 popce object o myobj4 0b 3 myob popce c parclass nobroker myob popcce object o myobj3 0b 3 myob ph myobj4 cc ph ph myobj3 cc myobj4 st popcce object o myobj2 obj myob32 ph myobj2 cc myobj3 s1 popce c parclass nobroker myobj2 ph popce object o myobj1l obj myob31 ph myobjl cc myobj2 s1 popcc o main main cc myobjl ph myobjl cc myobj2 stub o Figure 4 3 How to compile applications with dependencies 4 4 3 popce c parclass nobroker myobj3 ph 2 2 The commands popcc object o myob3X ob creates the complete executable file myobjX obj when the commands popcc c parclass nobroker myob3X ph creates a firl called myobjX stub o containing the relocatable binary code which will be used to be linked with other parallel classes or with the main program The parclass nobroker option of the POP C compiler indicates that the produced relocatable binary code must not contain internal POP C classes Compiler options specific to the POP C compiler are presented in the appendix A of this manual More examples of POP C source files with corresponding Makefile can be found in the test directory of the POP C distribution and on the POP C web site http gridgroup hetr ch pope Installa
57. tc popc user env csh and lt install dir gt etc popc user env sh If you do note use these shells or a shell compatible with these shells you have to add all the necessary lines in your login file refer to section 5 3 3 When this is done launch the Job Manager by typing the following command SXXpopc start Note the SXXpopc script is located at lt install dir gt sbin SXXpopc Again be aware that to launch the Job Manager you need to have execute X permission on the corresponding directory Note You can at any time stop restart or kill the Job manager by using the corresponding keyword After any new installation or configuration of POP C kill the Job Manager and start it again SXXpope Kill Installation Instructions 43 SXXpopc start 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 SXXpopc start Note In some specific cases POP C does not require that the Job Manager is running nevertheless we strongly recommend to always launch the Job Manager to avoid POP C programs execution failures Usually when a POP C program cannot reach the job manager for example because it is not running one of the following errors is displayed Cannot create object via POP C Job Manager or Fail to bind to the remote object broker 44 Installation Instructions Appendix A Command L
58. thods declaration These semantics described in section 2 4 are specified using the following keywords Synchronous Asynchronous interface semantic o sync Synchronous invocation This is the default value o async Asynchronous invocation Sequential Concurrent Mutex object side semantic o seq Sequential invocation This is the default value o mutex Mutex invocation o conc Concurrent invocation 14 User Programming Manual The combination of both 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 and belong to the parallel class ExampleClass parclass ExampleClass ExampleClass default constructor sync conc int myMethod synchronous concurrent method 3 2 4 Passing arguments Note In this document the words argument and parameter have the same meaning To distinguish between arguments or parameters which appear in the definition of the methods and arguments or parameters which are effectively used when calling methods we use the terms formal arguments and effective arguments respectively When calling methods of parallel objects remote methods the effective arguments of the call must be transferred to the object being called the same happens for returned values We have to distinguish between two different situations 1 the argument is a par
59. tion Instructions 35 CHAPTER 5 Installation Instructions POP 5 1 Introduction 5 3 Installation 5 2 Before installing 5 3 1 Preparing compilation 5 2 1 Prerequisites 5 3 2 Compiling POP C tools 5 2 2Location of the Files 5 3 3 POP C Setup 5 2 3 Downloading the POP C 5 4 Testing Installation Distribution 5 5 The Job Manager 5 1 Introduction POP C has been designed to run applications in large heterogenous distributed computing environments Nevertheless when starting using POP C or for testing purposes it is sometime very useful to be able to run POP C programs on a very simple infrastructure This is why POP C can be installed in two different ways e Standalone installation to install POP C on a single machine With this installation each parallel object will run in separated processes on the same computer e POP Community installation to run POP C in a complex distributed infrastructure Standalone installation is the easiest way to install POP C on a single computer It is useful to get familiar with POP C programming or to test POP C programs before running them on a complex hardware infrastructure Of course using POP C in this way does not allow you to increase the computing power you have access to If you are beginner with POP C we strongly recommend you to start with the standalone installation This installation can at any be upgraded to a POP Community installation by re running the set up
60. to do a first simple installation and how to run a first simple POP C program Overview 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 Solutions to commonly found problems Programming examples Latest sources available at https faridgroup heir eh pope Overview The Parallel Object Model 5 CHAPTER 2 The Parallel Object Model PEP Ch Introduction 2 4 Method 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 The POP programming model is an general model which can be applied to many imperative object oriented programming languages such as C Java C Eiffel etc These programming languages provide high level abstractions for software engineering 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 when executing an application Nevertheless two questions remain 1 which objects should run remotely 2 where does each remote object lives The answer of course depends 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 p
61. xception 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 penalizing when an exception derived from the std exception C class has been defined by the programmer and a message has been associated with this exception As the exception cannot be caught 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 when a exception derived from std exception is thrown in a remote method in both cases asynchronous and synchronous methods the POP C run time behaves in the following way Before giving back the control to the remote caller or to the POP C run time the following 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

Parallel Object Programming in C++ User and Installation Manual

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