Intel® MPI Library

Developer Guide for Linux* OS

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ID 768728
Date 10/31/2024
Public
Document Table of Contents
Document Table of Contents x
Developer Guide for Linux* OS
Developer Guide for Linux* OS x
Introduction Installation and Prerequisites Compiling and Linking Running Applications Debugging Applications Analysis and Tuning Troubleshooting Additional Supported Features Examples Notices and Disclaimers
Introduction x
Introducing Intel® MPI Library Conventions and Symbols Related Information
Installation and Prerequisites x
Installation Prerequisite Steps
Compiling and Linking x
Compiling an MPI Program Compilers Support ILP64 Support
Running Applications x
Running Intel® MPI Library in Containers Selecting a Library Configuration Running an MPI Program Running an MPI/OpenMP* Program MPMD Launch Mode Fabrics Control Job Schedulers Support Controlling Process Placement Java* MPI Applications Support
Running Intel® MPI Library in Containers x
Build a Singularity* Container for an MPI Application Run the Application with a Container
Fabrics Control x
Selecting Fabrics Libfabric* Support OFI* Providers Support
Debugging Applications x
Debugging Using -gtool for Debugging
Analysis and Tuning x
Displaying MPI Debug Information Tracing Applications Interoperability with Other Tools Through -gtool MPI Tuning
Troubleshooting x
Error Message: Bad Termination Error Message: No such file or Directory Error Message: Permission Denied Error Message: Fatal Error Error Message: Bad File Descriptor Error Message: Too Many Open Files Problem: High Memory Consumption Readings Problem: MPI Application Hangs Problem: Password Required Problem: Cannot Execute Binary File Problem: MPI limitation for Docker*
Additional Supported Features x
Asynchronous Progress Control Device-Initiated Communications Notified One-Sided Communications Multiple Endpoints Support
Multiple Endpoints Support x
MPI_THREAD_SPLIT Programming Model Threading Runtimes Support OpenMP* Threading Runtime See Also Program Examples Code Change Guide
Examples x
async_progress_sample.c thread_split.cpp thread_split_omp_for.c thread_split_omp_task.c thread_split_pthreads.c
Developer Guide for Linux* OS

Threading Runtimes Support

The MPI thread-split programming model has special support of the OpenMP* runtime, but you may use any other threading runtime. The support differs in the way you communicate with the MPI runtime to set up thread_id for a thread and the way you set up the number of threads to be run concurrently. If you choose the OpenMP runtime support, make sure you have the OpenMP runtime library, which comes with the recent Intel® compilers and GNU* gcc compilers, and link the application against it.

The support is controlled with the I_MPI_THREAD_RUNTIME environment variable. Since the threading runtime support is a non-standard functionality, you must enable it explicitly using the generic or openmp argument for the OpenMP* runtime support.

You can set the maximum number of threads to be used in each process concurrently with the I_MPI_THREAD_MAX environment variable. This helps the MPI implementation allocate the hardware resources efficiently. By default, the maximum number of threads per rank is 1.

OpenMP* Threading Runtime

The OpenMP runtime supports the both implicit and explicit submodels. By default, the Intel MPI Library assumes that thread_id is set with the omp_get_thread_num() function call defined in the OpenMP standard. This scenario corresponds to the implicit submodel. You can use the explicit submodel by setting the thread_id info key for a communicator, which is particularly useful for OpenMP tasks.

By default, the maximum number of threads is set with the omp_get_max_threads() function. To override this function, set either I_MPI_THREAD_MAX or  OMP_NUM_THREADS environment variable.

Parent topic: Multiple Endpoints Support
Level Two Title