On Wed, Oct 8, 2008 at 7:16 PM, Jeff Squyres <firstname.lastname@example.org>
On Oct 8, 2008, at 9:10 AM, Sangamesh B wrote:
A few things:
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.
- What version of Open MPI are you using? Please send the information listed here:
Use "--mca mpi_leave_pinned 1" on your mpirun command line (I don't know if leave pinned behavior benefits Gromacs or not, but it likely won't hurt)
- Did you enable processor affinity?
Use "--mca mpi_paffinity_alone 1" on your mpirun command line.
Will use these options in the next benchmark
- Are you sure that Open MPI didn't fall back to ethernet (and not use IB)? Use "--mca btl openib,self" on your mpirun command line.
I'm using TCP. There is no infiniband support. But eventhough the results can be compared?
- Have you tried compiling Open MPI with something other than GCC?
Just this week, we've gotten some reports from an OMPI member that they are sometimes seeing *huge* performance differences with OMPI compiled with GCC vs. any other compiler (Intel, PGI, Pathscale). We are working to figure out why; no root cause has been identified yet.
I'll try for other than gcc and comeback to you