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Subject: Re: [OMPI users] Performance: MPICH2 vs OpenMPI
From: Sangamesh B (forum.san_at_[hidden])
Date: 2008-10-08 10:27:31


FYI attached here OpenMPI install details

On Wed, Oct 8, 2008 at 7:56 PM, Sangamesh B <forum.san_at_[hidden]> wrote:

>
>
> On Wed, Oct 8, 2008 at 7:16 PM, Jeff Squyres <jsquyres_at_[hidden]> wrote:
>
>> On Oct 8, 2008, at 9:10 AM, Sangamesh B wrote:
>>
>> 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.
>>>
>>
>>
>> A few things:
>>
>> - What version of Open MPI are you using? Please send the information
>> listed here:
>>
> 1.2.7
>
>>
>> http://www.open-mpi.org/community/help/
>>
>> - Did you specify to use mpi_leave_pinned?
>
> No
>
>> 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?
>
> No
>
>> 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?
>
> No.
>
>> 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
>
>>
>> --
>> Jeff Squyres
>> Cisco Systems
>>
>>
>> _______________________________________________
>> users mailing list
>> users_at_[hidden]
>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>>
>
>

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