Intel® MPI Library Developer Guide for Windows* OS

Developer Guide

Contents

Running an MPI/OpenMP* Program

To run a hybrid MPI/OpenMP* program, follow these steps:
  1. Make sure the thread-safe (debug or release, as desired) Intel® MPI Library configuration is enabled (release is the default version). To switch to such a configuration,
    run
    vars.bat
     with the appropriate argument. See Selecting Library Configuration for details. For example: 
    > vars.bat release
  2. Set the
    I_MPI_PIN_DOMAIN
     environment variable to specify the desired process pinning scheme. The recommended value is
    omp
    : 
    > set I_MPI_PIN_DOMAIN=omp
    This sets the process pinning domain size to be equal to
    OMP_NUM_THREADS
    . Therefore, if for example
    OMP_NUM_THREADS
     is equal to
    4
    , each MPI process can create up to four threads within the corresponding domain (set of logical processors). If
    OMP_NUM_THREADS
     is not set, each node is treated as a separate domain, which allows as many threads per MPI process as there are cores.
    For pinning OpenMP* threads within the domain, use the Intel® compiler
    KMP_AFFINITY
     environment variable. See the Intel compiler documentation for more details.
  3. Run your hybrid program as a regular MPI program. You can set the
    OMP_NUM_THREADS
     and
    I_MPI_PIN_DOMAIN
     variables directly in the launch command. For example: 
    > mpiexec -n 4 -genv OMP_NUM_THREADS=4 -genv I_MPI_PIN_DOMAIN=omp myprog.exe

See Also

Intel® MPI Library Developer Reference
, section
Tuning Reference > Process Pinning >
>
Interoperability with OpenMP*
.

Product and Performance Information

1

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.