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Subject: [OMPI users] 50% performance reduction due to OpenMPI v 1.3.2 forcing all MPI traffic over Ethernet instead of using Infiniband
From: Jim Kress ORG (jimkress_58_at_[hidden])
Date: 2009-06-22 20:14:20


For the app I am using, ORCA (a Quantum Chemistry program), when it was
compiled using openMPI 1.2.8 and run under 1.2.8 with the following in
the openmpi-mca-params.conf file:

btl=self,openib

the app ran fine with no traffic over my Ethernet network and all
traffic over my Infiniband network.

However, now that ORCA has been recompiled with openMPI v1.3.2 and run
under 1.3.2 (using the same openmpi-mca-params.conf file), the
performance has been reduced by 50% and all the MPI traffic is going
over the Ethernet network.

As a matter of fact, the openMPI v1.3.2 performance now looks exactly
like the performance I get if I use MPICH 1.2.7.

Anyone have any ideas:

1) How could this have happened?

2) How can I fix it?

a 50% reduction in performance is just not acceptable. Ideas/
suggestions would be appreciated.

Jim