Developer Guide for Intel® oneAPI Math Kernel Library for Linux*
Interaction with the Message-Passing Interface
To improve performance of cluster applications, it is critical for Intel® oneAPI Math Kernel Library (oneMKL) to use the optimal number of threads, as well as the correct thread affinity. Usually, the optimal number is the number of available cores per node divided by the number of MPI processes per node. You can set the number of threads using one of the available methods, described in Techniques to Set the Number of Threads .
If the number of threads is not set, Intel® oneAPI Math Kernel Library (oneMKL) checks whether it runs under MPI provided by the Intel® MPI Library. If this is true, the following environment variables define Intel® oneAPI Math Kernel Library (oneMKL) threading behavior:
I_MPI_THREAD_LEVEL
MKL_MPI_PPN
I_MPI_NUMBER_OF_MPI_PROCESSES_PER_NODE
I_MPI_PIN_MAPPING
OMPI_COMM_WORLD_LOCAL_SIZE
MPI_LOCALNRANKS
0 or undefined.
Intel® oneAPI Math Kernel Library (oneMKL) considers that thread support level of Intel MPI Library is MPI_THREAD_SINGLE and defaults to sequential execution.
1, 2, or 3.
This value determines Intel® oneAPI Math Kernel Library (oneMKL) conclusion of the thread support level:
In all these cases, Intel® oneAPI Math Kernel Library (oneMKL) determines the number of MPI processes per node using the other environment variables listed and defaults to the number of threads equal to the number of available cores per node divided by the number of MPI processes per node. * 1 - MPI_THREAD_FUNNELED * 2 - MPI_THREAD_SERIALIZED * 3 - MPI_THREAD_MULTIPLE
Product and Performance Information |
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Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex . Notice revision #20201201 |