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my experience is that OpenMPI has slightly less latency and less
bandwidth than Intel MPI (which is based on mpich2) using InfiniBand.
I don't remember the numbers using shared memory.
As you are seeing a huge difference, I would suspect that either
something with your compilation is strange or more probable that you hit
the cc-numa effect of the Opteron.
You might want to bind the MPI processes (and even clean the filesystem
caches) to avoid that effect.
Sangamesh B wrote:
> Hi All,
> I wanted to switch from mpich2/mvapich2 to OpenMPI, as OpenMPI
> supports both ethernet and infiniband. Before doing that I tested an
> application 'GROMACS' to compare the performance of MPICH2 & OpenMPI.
> Both have been compiled with GNU compilers.
> After this benchmark, I came to know that OpenMPI is slower than MPICH2.
> This benchmark is run on a AMD dual core, dual opteron processor. Both
> have compiled with default configurations.
> The job is run on 2 nodes - 8 cores.
> OpenMPI - 25 m 39 s.
> MPICH2 - 15 m 53 s.
> Any comments ..?