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openmp, openmp vs mpi
OpenMP Open Multi-Processing is an application programming interface API that supports multi-platform shared memory multiprocessing programming in C, C++, and Fortran,3 on most platforms, processor architectures and operating systems, including Solaris, AIX, HP-UX, Linux, macOS, and Windows It consists of a set of compiler directives, library routines, and environment variables that influence run-time behavior245

OpenMP is managed by the nonprofit technology consortium OpenMP Architecture Review Board or OpenMP ARB, jointly defined by a group of major computer hardware and software vendors, including AMD, IBM, Intel, Cray, HP, Fujitsu, Nvidia, NEC, Red Hat, Texas Instruments, Oracle Corporation, and more1

OpenMP uses a portable, scalable model that gives programmers a simple and flexible interface for developing parallel applications for platforms ranging from the standard desktop computer to the supercomputer

An application built with the hybrid model of parallel programming can run on a computer cluster using both OpenMP and Message Passing Interface MPI, such that OpenMP is used for parallelism within a multi-core node while MPI is used for parallelism between nodes There have also been efforts to run OpenMP on software distributed shared memory systems,6 to translate OpenMP into MPI78 and to extend OpenMP for non-shared memory systems9


  • 1 Introduction
  • 2 History
  • 3 The core elements
    • 31 Thread creation
    • 32 Work-sharing constructs
    • 33 OpenMP clauses
      • 331 Data sharing attribute clauses
      • 332 Synchronization clauses
      • 333 Scheduling clauses
      • 334 IF control
      • 335 Initialization
      • 336 Data copying
      • 337 Reduction
      • 338 Others
    • 34 User-level runtime routines
    • 35 Environment variables
  • 4 Sample programs
    • 41 Hello World
      • 411 C
      • 412 C++
      • 413 Fortran 77
      • 414 Fortran 90 free-form
    • 42 Clauses in work-sharing constructs in C/C++
  • 5 Implementations
  • 6 Pros and cons
  • 7 Performance expectations
  • 8 Thread affinity
  • 9 Benchmarks
  • 10 Learning resources online
  • 11 See also
  • 12 References
  • 13 Further reading
  • 14 External links


An illustration of multithreading where the master thread forks off a number of threads which execute blocks of code in parallel See also: Fork–join model

OpenMP is an implementation of multithreading, a method of parallelizing whereby a master thread a series of instructions executed consecutively forks a specified number of slave threads and the system divides a task among them The threads then run concurrently, with the runtime environment allocating threads to different processors

The section of code that is meant to run in parallel is marked accordingly, with a compiler directive that will cause the threads to form before the section is executed3 Each thread has an id attached to it which can be obtained using a function called omp_get_thread_num The thread id is an integer, and the master thread has an id of 0 After the execution of the parallelized code, the threads join back into the master thread, which continues onward to the end of the program

By default, each thread executes the parallelized section of code independently Work-sharing constructs can be used to divide a task among the threads so that each thread executes its allocated part of the code Both task parallelism and data parallelism can be achieved using OpenMP in this way

The runtime environment allocates threads to processors depending on usage, machine load and other factors The runtime environment can assign the number of threads based on environment variables, or the code can do so using functions The OpenMP functions are included in a header file labelled omph in C/C++


The OpenMP Architecture Review Board ARB published its first API specifications, OpenMP for Fortran 10, in October 1997 October the following year they released the C/C++ standard 2000 saw version 20 of the Fortran specifications with version 20 of the C/C++ specifications being released in 2002 Version 25 is a combined C/C++/Fortran specification that was released in 2005

Up to version 20, OpenMP primarily specified ways to parallelize highly regular loops, as they occur in matrix-oriented numerical programming, where the number of iterations of the loop is known at entry time This was recognized as a limitation, and various task parallel extensions were added to implementations In 2005, an effort to standardize task parallelism was formed, which published a proposal in 2007, taking inspiration from task parallelism features in Cilk, X10 and Chapel10

Version 30 was released in May 2008 Included in the new features in 30 is the concept of tasks and the task construct,11 significantly broadening the scope of OpenMP beyond the parallel loop constructs that made up most of OpenMP 2012

Version 40 of the specification was released in July 201313 It adds or improves the following features: support for accelerators; atomics; error handling; thread affinity; tasking extensions; user defined reduction; SIMD support; Fortran 2003 support14full citation needed

The current version is 45

Note that not all compilers and OSes support the full set of features for the latest version/s

The core elementsedit

Chart of OpenMP constructs

The core elements of OpenMP are the constructs for thread creation, workload distribution work sharing, data-environment management, thread synchronization, user-level runtime routines and environment variables

In C/C++, OpenMP uses #pragmas The OpenMP specific pragmas are listed below

Thread creationedit

The pragma omp parallel is used to fork additional threads to carry out the work enclosed in the construct in parallel The original thread will be denoted as master thread with thread ID 0

Example C program: Display "Hello, world" using multiple threads

#include <stdioh> int mainvoid

Use flag -fopenmp to compile using GCC:

$ gcc -fopenmp helloc -o hello

Output on a computer with two cores, and thus two threads:

Hello, world Hello, world

However, the output may also be garbled because of the race condition caused from the two threads sharing the standard output

Hello, wHello, woorld rld

Work-sharing constructsedit

Used to specify how to assign independent work to one or all of the threads

  • omp for or omp do: used to split up loop iterations among the threads, also called loop constructs
  • sections: assigning consecutive but independent code blocks to different threads
  • single: specifying a code block that is executed by only one thread, a barrier is implied in the end
  • master: similar to single, but the code block will be executed by the master thread only and no barrier implied in the end

Example: initialize the value of a large array in parallel, using each thread to do part of the work

int mainint argc, char argv return 0;

The loop counter i is declared inside the parallel for loop in C99 style, which gives each thread a unique and private version of the variable15

OpenMP clausesedit

Since OpenMP is a shared memory programming model, most variables in OpenMP code are visible to all threads by default But sometimes private variables are necessary to avoid race conditions and there is a need to pass values between the sequential part and the parallel region the code block executed in parallel, so data environment management is introduced as data sharing attribute clauses by appending them to the OpenMP directive The different types of clauses are

Data sharing attribute clausesedit

  • shared: the data within a parallel region is shared, which means visible and accessible by all threads simultaneously By default, all variables in the work sharing region are shared except the loop iteration counter
  • private: the data within a parallel region is private to each thread, which means each thread will have a local copy and use it as a temporary variable A private variable is not initialized and the value is not maintained for use outside the parallel region By default, the loop iteration counters in the OpenMP loop constructs are private
  • default: allows the programmer to state that the default data scoping within a parallel region will be either shared, or none for C/C++, or shared, firstprivate, private, or none for Fortran The none option forces the programmer to declare each variable in the parallel region using the data sharing attribute clauses
  • firstprivate: like private except initialized to original value
  • lastprivate: like private except original value is updated after construct
  • reduction: a safe way of joining work from all threads after construct

Synchronization clausesedit

  • critical: the enclosed code block will be executed by only one thread at a time, and not simultaneously executed by multiple threads It is often used to protect shared data from race conditions
  • atomic: the memory update write, or read-modify-write in the next instruction will be performed atomically It does not make the entire statement atomic; only the memory update is atomic A compiler might use special hardware instructions for better performance than when using critical
  • ordered: the structured block is executed in the order in which iterations would be executed in a sequential loop
  • barrier: each thread waits until all of the other threads of a team have reached this point A work-sharing construct has an implicit barrier synchronization at the end
  • nowait: specifies that threads completing assigned work can proceed without waiting for all threads in the team to finish In the absence of this clause, threads encounter a barrier synchronization at the end of the work sharing construct

Scheduling clausesedit

  • scheduletype, chunk: This is useful if the work sharing construct is a do-loop or for-loop The iterations in the work sharing construct are assigned to threads according to the scheduling method defined by this clause The three types of scheduling are:
  1. static: Here, all the threads are allocated iterations before they execute the loop iterations The iterations are divided among threads equally by default However, specifying an integer for the parameter chunk will allocate chunk number of contiguous iterations to a particular thread
  2. dynamic: Here, some of the iterations are allocated to a smaller number of threads Once a particular thread finishes its allocated iteration, it returns to get another one from the iterations that are left The parameter chunk defines the number of contiguous iterations that are allocated to a thread at a time
  3. guided: A large chunk of contiguous iterations are allocated to each thread dynamically as above The chunk size decreases exponentially with each successive allocation to a minimum size specified in the parameter chunk

IF controledit

  • if: This will cause the threads to parallelize the task only if a condition is met Otherwise the code block executes serially


  • firstprivate: the data is private to each thread, but initialized using the value of the variable using the same name from the master thread
  • lastprivate: the data is private to each thread The value of this private data will be copied to a global variable using the same name outside the parallel region if current iteration is the last iteration in the parallelized loop A variable can be both firstprivate and lastprivate
  • threadprivate: The data is a global data, but it is private in each parallel region during the runtime The difference between threadprivate and private is the global scope associated with threadprivate and the preserved value across parallel regions

Data copyingedit

  • copyin: similar to firstprivate for private variables, threadprivate variables are not initialized, unless using copyin to pass the value from the corresponding global variables No copyout is needed because the value of a threadprivate variable is maintained throughout the execution of the whole program
  • copyprivate: used with single to support the copying of data values from private objects on one thread the single thread to the corresponding objects on other threads in the team


  • reductionoperator | intrinsic : list: the variable has a local copy in each thread, but the values of the local copies will be summarized reduced into a global shared variable This is very useful if a particular operation specified in operator for this particular clause on a variable runs iteratively, so that its value at a particular iteration depends on its value at a prior iteration The steps that lead up to the operational increment are parallelized, but the threads updates the global variable in a thread safe manner This would be required in parallelizing numerical integration of functions and differential equations, as a common example


  • flush: The value of this variable is restored from the register to the memory for using this value outside of a parallel part
  • master: Executed only by the master thread the thread which forked off all the others during the execution of the OpenMP directive No implicit barrier; other team members threads not required to reach

User-level runtime routinesedit

Used to modify/check the number of threads, detect if the execution context is in a parallel region, how many processors in current system, set/unset locks, timing functions, etc

Environment variablesedit

A method to alter the execution features of OpenMP applications Used to control loop iterations scheduling, default number of threads, etc For example, OMP_NUM_THREADS is used to specify number of threads for an application

Sample programsedit

In this section, some sample programs are provided to illustrate the concepts explained above

Hello Worldedit

A basic program that exercises the parallel, private and barrier directives, and the functions omp_get_thread_num and omp_get_num_threads not to be confused


This C program can be compiled using gcc-44 with the flag -fopenmp

#include <omph> #include <stdioh> #include <stdlibh> int main int argc, char argv return EXIT_SUCCESS;


This C++ program can be compiled using GCC: g++ -Wall -Wextra -Werror -fopenmp testcpp
NOTE: iostream is not thread-safe Therefore, for instance, cout calls must be executed in critical areas or by only one thread eg masterthread

#include <iostream> #include <omph> int main #pragma omp barrier #pragma omp master return 0;

Fortran 77edit

Here is a Fortran 77 version


Fortran 90 free-formedit

Here is a Fortran 90 free-form version

program hello90 use omp_lib integer:: id, nthreads !$omp parallel privateid id = omp_get_thread_num write , 'Hello World from thread', id !$omp barrier if id == 0 then nthreads = omp_get_num_threads write , 'There are', nthreads, 'threads' end if !$omp end parallel end program

Clauses in work-sharing constructs in C/C++edit

The application of some OpenMP clauses are illustrated in the simple examples in this section The code sample below updates the elements of an array b by performing a simple operation on the elements of an array a The parallelization is done by the OpenMP directive #pragma omp The scheduling of tasks is dynamic Notice how the iteration counters j and k have to be made private, whereas the primary iteration counter i is private by default The task of running through i is divided among multiple threads, and each thread creates its own versions of j and k in its execution stack, thus doing the full task allocated to it and updating the allocated part of the array b at the same time as the other threads

#define CHUNKSIZE 1 /defines the chunk size as 1 contiguous iteration/ /forks off the threads/ #pragma omp parallel privatej,k

The next code sample is a common usage of the reduction clause to calculate reduced sums Here, we add up all the elements of an array a with an i-dependent weight using a for loop, which we parallelize using OpenMP directives and reduction clause The scheduling is kept static

#define N 10000 /size of a/ void calculatelong ; /The function that calculates the elements of a/ int i; long w; long aN; calculatea; long sum = 0; /forks off the threads and starts the work-sharing construct/ #pragma omp parallel for privatew reduction+:sum schedulestatic,1 fori = 0; i < N; i++ printf"\n %li",sum;

An equivalent, less elegant, implementation of the above code is to create a local sum variable for each thread "loc_sum", and make a protected update of the global variable sum at the end of the process, through the directive critical Note that this protection is critical, as explained elsewhere

long sum = 0, loc_sum; /forks off the threads and starts the work-sharing construct/ #pragma omp parallel privatew,loc_sum #pragma omp critical sum = sum + loc_sum; printf"\n %li",sum;


OpenMP has been implemented in many commercial compilers For instance, Visual C++ 2005, 2008, 2010, 2012 and 2013 support it OpenMP 20, in Professional, Team System, Premium and Ultimate editions161718, as well as Intel Parallel Studio for various processors19 Oracle Solaris Studio compilers and tools support the latest OpenMP specifications with productivity enhancements for Solaris OS UltraSPARC and x86/x64 and Linux platforms The Fortran, C and C++ compilers from The Portland Group also support OpenMP 25 GCC has also supported OpenMP since version 42

Compilers with an implementation of OpenMP 30:

  • GCC 431
  • Mercurium compiler
  • Intel Fortran and C/C++ versions 110 and 111 compilers, Intel C/C++ and Fortran Composer XE 2011 and Intel Parallel Studio
  • IBM XL C/C++ compiler20
  • Sun Studio 12 update 1 has a full implementation of OpenMP 3021

Several compilers support OpenMP 31:

  • GCC 4722
  • Intel Fortran and C/C++ compilers 12123
  • LLVM/Clang 3724

Compilers supporting OpenMP 40:

  • GCC 490 for C/C++, GCC 491 for Fortran2225
  • Intel Fortran and C/C++ compilers 15026
  • LLVM/Clang 37 partial24

Auto-parallelizing compilers that generates source code annotated with OpenMP directives:

  • iPat/OMP
  • Parallware
  • ROSE compiler framework
  • S2P by KPIT Cummins Infosystems Ltd

Several profilers and debuggers expressly support OpenMP:

  • Allinea Distributed Debugging Tool DDT – debugger for OpenMP and MPI codes
  • Allinea MAP – profiler for OpenMP and MPI codes
  • ompP – profiler for OpenMP
  • VAMPIR – profiler for OpenMP and MPI codes

Pros and consedit


  • Portable multithreading code in C/C++ and other languages, one typically has to call platform-specific primitives in order to get multithreading
  • Simple: need not deal with message passing as MPI does
  • Data layout and decomposition is handled automatically by directives
  • Scalability comparable to MPI on shared-memory systems27
  • Incremental parallelism: can work on one part of the program at one time, no dramatic change to code is needed
  • Unified code for both serial and parallel applications: OpenMP constructs are treated as comments when sequential compilers are used
  • Original serial code statements need not, in general, be modified when parallelized with OpenMP This reduces the chance of inadvertently introducing bugs
  • Both coarse-grained and fine-grained parallelism are possible
  • In irregular multi-physics applications which do not adhere solely to the SPMD mode of computation, as encountered in tightly coupled fluid-particulate systems, the flexibility of OpenMP can have a big performance advantage over MPI2728
  • Can be used on various accelerators such as GPGPU29


  • Risk of introducing difficult to debug synchronization bugs and race conditions3031
  • Currently only runs efficiently in shared-memory multiprocessor platforms see however Intel's Cluster OpenMP and other distributed shared memory platforms
  • Requires a compiler that supports OpenMP
  • Scalability is limited by memory architecture
  • No support for compare-and-swap32
  • Reliable error handling is missing
  • Lacks fine-grained mechanisms to control thread-processor mapping
  • High chance of accidentally writing false sharing code

Performance expectationsedit

One might expect to get an N times speedup when running a program parallelized using OpenMP on a N processor platform However, this seldom occurs for these reasons:

  • When a dependency exists, a process must wait until the data it depends on is computed
  • When multiple processes share a non-parallel proof resource like a file to write in, their requests are executed sequentially Therefore, each thread must wait until the other thread releases the resource
  • A large part of the program may not be parallelized by OpenMP, which means that the theoretical upper limit of speedup is limited according to Amdahl's law
  • N processors in a symmetric multiprocessing SMP may have N times the computation power, but the memory bandwidth usually does not scale up N times Quite often, the original memory path is shared by multiple processors and performance degradation may be observed when they compete for the shared memory bandwidth
  • Many other common problems affecting the final speedup in parallel computing also apply to OpenMP, like load balancing and synchronization overhead

Thread affinityedit

Some vendors recommend setting the processor affinity on OpenMP threads to associate them with particular processor cores333435 This minimizes thread migration and context-switching cost among cores It also improves the data locality and reduces the cache-coherency traffic among the cores or processors


There are some public domain OpenMP benchmarks for users to try

  • NAS parallel benchmark
  • OpenMP validation suite
  • OpenMP source code repository
  • EPCC OpenMP Microbenchmarks

Learning resources onlineedit

  • Video Tutorials on YouTube
  • Tutorial on llnlgov
  • Reference/tutorial page on nerscgov
  • Tutorial in CI-Tutor

See alsoedit

  • Cilk and Cilk Plus
  • Message Passing Interface
  • Concurrency computer science
  • Heterogeneous System Architecture
  • Parallel computing
  • Parallel programming model
  • POSIX Threads
  • Unified Parallel C
  • X10 programming language
  • Parallel Virtual Machine
  • Bulk synchronous parallel
  • Grand Central Dispatch – comparable technology for C, C++, and Objective-C by Apple
  • Partitioned global address space
  • CUDA – Nvidia
  • AMD FireStream
  • Octopiler
  • OpenCL – Standard supported by Apple, Nvidia, Intel, IBM, AMD/ATI and many others
  • OpenACC – a standard for GPU acceleration, which is planned to be merged into OpenMP
  • SequenceL
  • Enduro/X middleware for multiprocessing and distributed transactions, using XATMI API


  1. ^ a b c "About the OpenMP ARB and" OpenMPorg 2013-07-11 Retrieved 2013-08-14 
  2. ^ a b "OpenMP Compilers" OpenMPorg 2013-04-10 Retrieved 2013-08-14 
  3. ^ a b Gagne, Abraham Silberschatz, Peter Baer Galvin, Greg Operating system concepts 9th ed Hoboken, NJ: Wiley pp 181–182 ISBN 978-1-118-06333-0 
  4. ^ OpenMP Tutorial at Supercomputing 2008
  5. ^ Using OpenMP – Portable Shared Memory Parallel Programming – Download Book Examples and Discuss
  6. ^ Costa, JJ; et al May 2006 "Running OpenMP applications efficiently on an everything-shared SDSM" Journal of Parallel and Distributed Computing Elsevier 66 5: 647–658 doi:101016/jjpdc200506018 Retrieved 12 October 2016  CS1 maint: Explicit use of et al link
  7. ^ Basumallik, Ayon; Min, Seung-Jai; Eigenmann, Rudolf 2007 "Programming Distributed Memory Sytems sic using OpenMP" Proceedings of the 2007 IEEE International Parallel and Distributed Processing Symposium New York: IEEE Press doi:101109/IPDPS2007370397  A preprint is available on Chen Ding's home page; see especially Section 3 on Translation of OpenMP to MPI
  8. ^ Wang, Jue; Hu, ChangJun; Zhang, JiLin; Li, JianJiang May 2010 "OpenMP compiler for distributed memory architectures" Science China Information Sciences Springer Publishing 53 5: 932–944 doi:101007/s11432-010-0074-0 Retrieved 12 October 2016  As of 2016update the KLCoMP software described in this paper does not appear to be publicly available
  9. ^ Cluster OpenMP a product that used to be available for Intel C++ Compiler versions 91 to 111 but was dropped in 120
  10. ^ Ayguade, Eduard; Copty, Nawal; Duran, Alejandro; Hoeflinger, Jay; Lin, Yuan; Massaioli, Federico; Su, Ernesto; Unnikrishnan, Priya; Zhang, Guansong 2007 A proposal for task parallelism in OpenMP PDF Proc Int'l Workshop on OpenMP 
  11. ^ "OpenMP Application Program Interface, Version 30" PDF openmporg May 2008 Retrieved 2014-02-06 
  12. ^ LaGrone, James; Aribuki, Ayodunni; Addison, Cody; Chapman, Barbara 2011 A Runtime Implementation of OpenMP Tasks Proc Int'l Workshop on OpenMP pp 165–178 CiteSeerX 10112212775 doi:101007/978-3-642-21487-5_13 
  13. ^ "OpenMP 40 API Released" OpenMPorg 2013-07-26 Retrieved 2013-08-14 
  14. ^ "OpenMP Application Program Interface, Version 40" PDF openmporg July 2013 Retrieved 2014-02-06 
  15. ^ http://supercomputingblogcom/openmp/tutorial-parallel-for-loops-with-openmp/
  16. ^ Visual C++ Editions, Visual Studio 2005
  17. ^ Visual C++ Editions, Visual Studio 2008
  18. ^ Visual C++ Editions, Visual Studio 2010
  19. ^ David Worthington, "Intel addresses development life cycle with Parallel Studio", SDTimes, 26 May 2009 accessed 28 May 2009
  20. ^ "XL C/C++ for Linux Features", accessed 9 June 2009
  21. ^ "Oracle Technology Network for Java Developers | Oracle Technology Network | Oracle" Developerssuncom Retrieved 2013-08-14 
  22. ^ a b "openmp – GCC Wiki" Gccgnuorg 2013-07-30 Retrieved 2013-08-14 
  23. ^ Submitted by Patrick Kennedy on Fri, 09/02/2011 – 11:28 2011-09-06 "Intel® C++ and Fortran Compilers now support the OpenMP 31 Specification | Intel® Developer Zone" Softwareintelcom Retrieved 2013-08-14 
  24. ^ a b "Clang 37 Release Notes" llvmorg Retrieved 2015-10-10 
  25. ^ "GCC 49 Release Series – Changes" wwwgnuorg 
  26. ^ "OpenMP 40 Features in Intel Compiler 150" Softwareintelcom 
  27. ^ a b Amritkar, Amit; Tafti, Danesh; Liu, Rui; Kufrin, Rick; Chapman, Barbara 2012 "OpenMP parallelism for fluid and fluid-particulate systems" Parallel Computing 38 9: 501 doi:101016/jparco201205005 
  28. ^ Amritkar, Amit; Deb, Surya; Tafti, Danesh 2014 "Efficient parallel CFD-DEM simulations using OpenMP" Journal of Computational Physics 256: 501 Bibcode:2014JCoPh256501A doi:101016/jjcp201309007 
  29. ^ Frequently Asked Questions on OpenMP
  30. ^ Detecting and Avoiding OpenMP Race Conditions in C++
  31. ^ Alexey Kolosov, Evgeniy Ryzhkov, Andrey Karpov 32 OpenMP traps for C++ developers
  32. ^ Stephen Blair-Chappell, Intel Corporation, Becoming a Parallel Programming Expert in Nine Minutes, presentation on ACCU 2010 conference
  33. ^ Chen, Yurong 2007-11-15 "Multi-Core Software" Intel Technology Journal Intel 11 4 doi:101535/itj110408 
  34. ^ "OMPM2001 Result" SPEC 2008-01-28 
  35. ^ "OMPM2001 Result" SPEC 2003-04-01 

Further readingedit

  • Quinn Michael J, Parallel Programming in C with MPI and OpenMP McGraw-Hill Inc 2004 ISBN 0-07-058201-7
  • R Chandra, R Menon, L Dagum, D Kohr, D Maydan, J McDonald, Parallel Programming in OpenMP Morgan Kaufmann, 2000 ISBN 1-55860-671-8
  • R Eigenmann Editor, M Voss Editor, OpenMP Shared Memory Parallel Programming: International Workshop on OpenMP Applications and Tools, WOMPAT 2001, West Lafayette, IN, USA, July 30–31, 2001 Lecture Notes in Computer Science Springer 2001 ISBN 3-540-42346-X
  • B Chapman, G Jost, R van der Pas, DJ Kuck foreword, Using OpenMP: Portable Shared Memory Parallel Programming The MIT Press October 31, 2007 ISBN 0-262-53302-2
  • Parallel Processing via MPI & OpenMP, M Firuziaan, O Nommensen Linux Enterprise, 10/2002
  • MSDN Magazine article on OpenMP
  • SC08 OpenMP Tutorial PDF – Hands-On Introduction to OpenMP, Mattson and Meadows, from SC08 Austin
  • OpenMP Specifications
  • Parallel Programming in Fortran 95 using OpenMP PDF

External linksedit

  • Official website, includes the latest OpenMP specifications, links to resources, lively set of forums where questions can be asked and are answered by OpenMP experts and implementors
  • OpenMPCon, website of the OpenMP Developers Conference
  • IWOMP, website for the annual International Workshop on OpenMP
  • GOMP is GCC's OpenMP implementation, part of GCC
  • IBM Octopiler with OpenMP support
  • Blaise Barney, Lawrence Livermore National Laboratory site on OpenMP
  • ompca, an application in REDLIB project for the interactive symbolic model-checker of C/C++ programs with OpenMP directives
  • Combining OpenMP and MPI PDF
  • Mixing MPI and OpenMP
  • Measure and visualize OpenMP parallelism by means of a C++ routing planner calculating the Speedup factor

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