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Subject: [OMPI users] OpenMPI providing rank?
From: Yves Caniou (yves.caniou_at_[hidden])
Date: 2010-07-27 23:34:49


Hi,

I have some performance issue on a parallel machine composed of nodes of 16
procs each. The application is launched on multiple of 16 procs for given
numbers of nodes.
I was told by people using MX MPI with this machine to attach a script to
mpiexec, which 'numactl' things, in order to make the execution performance
stable.

Looking on the faq (the oldest one is for OpenMPI v1.3?), I saw that maybe the
solution would be for me to use the --mca mpi_paffinity_alone 1
Is that correct? -- BTW, I have both memory and processor affinity:
>ompi_info | grep affinity
           MCA paffinity: linux (MCA v2.0, API v2.0, Component v1.4.2)
           MCA maffinity: first_use (MCA v2.0, API v2.0, Component v1.4.2)
           MCA maffinity: libnuma (MCA v2.0, API v2.0, Component v1.4.2)
Does it handle memory too, or do I have to use another option like
--mca mpi_maffinity 1?

Still, I would like to test the numactl solution. Does OpenMPI provide an
equivalent to $MXMPI_ID which gives at least gives the NODE on which a
process is launched by OpenMPI, so that I can adapt the script that was given
to me?

Tkx.

.Yves.