GAMMA programs use OpenMP for parallel processing. The number of threads used range from 3-12+ from program to program. This can lead to severe CPU contention when running multiple GAMMA jobs on the same machine, drastically increasing the run time of those jobs.
This allows running multiple jobs on the same machine without CPU contention. For example, running two jobs on an 8 core machine would typically result in both jobs trying to use all 8 cores at the same time. Setting ++omp-num-threads=4 for each job would limit the total demand to match the number of available cores and eliminates the performance degradation.
GAMMA programs use OpenMP for parallel processing. The number of threads used range from 3-12+ from program to program. This can lead to severe CPU contention when running multiple GAMMA jobs on the same machine, drastically increasing the run time of those jobs.
This PR adds a command line parameter to the
main()entrypoint to set theOMP_NUM_THREADSenvironment variable. See https://www.ibm.com/docs/en/zos/2.2.0?topic=suce-environment-variables-openmpThis allows running multiple jobs on the same machine without CPU contention. For example, running two jobs on an 8 core machine would typically result in both jobs trying to use all 8 cores at the same time. Setting
++omp-num-threads=4for each job would limit the total demand to match the number of available cores and eliminates the performance degradation.