Hi,
In the process of testing out reframe <https://reframe-hpc.readthedocs.io/> I
ran IMB pingpong using openmpi 3.1.0 with:
mpirun -np 2 --report-bindings IMB-MPI1 pingpong
I find that if set
OMPI_MCA_hwloc_base_binding_policy=core
I get slightly higher zero-size latency (1.58us vs 1.32us without this),
but the reported bindings are exactly the same (shown below - note
hyperthreading is enabled on this system).
I expected the bindings not to change given the docs say "--bind-to core"
is the default for this version of OpenMPI. So any suggestions as to why
the latency changes? I know it's not necessarily a huge change but seems
odd.
[openhpc-compute-0.novalocal:03604] MCW rank 0 bound to socket 0[core 0[hwt
0-1]]:
[BB/../../../../../../../../../../../../../../..][../../../../../../../../../../../../../../../..]
[openhpc-compute-1.novalocal:02213] MCW rank 1 bound to socket 0[core 0[hwt
0-1]]:
[BB/../../../../../../../../../../../../../../..][../../../../../../../../../../../../../../../..]
thanks
Steve
http://stackhpc.com/
Please note I work Tuesday to Friday.
