[petsc-users] strange PETSc/KSP GMRES timings for MPI+OMP configuration on KNLs

[Damian Kaliszan]

Hi,

For  several  days  I've been trying to figure out what is going wrong
with my python app timings solving Ax=b with KSP (GMRES) solver when trying to run on Intel's KNL 7210/7230.

I  downsized  the  problem  to  1000x1000 A matrix and a single node and
observed the following:


I'm attaching 2 extreme timings where configurations differ only by 1 OMP thread (64MPI/1 OMP vs 64/2 OMPs),
23321 vs 23325 slurm task ids.

Any help will be appreciated....

Best,
Damian
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