On Thu, Oct 9, 2008 at 2:39 AM, Brian Dobbins <bdobb...@gmail.com> wrote:
> > Hi guys, > > [From Eugene Loh:] > >> OpenMPI - 25 m 39 s. >>> MPICH2 - 15 m 53 s. >>> >> With regards to your issue, do you have any indication when you get that >> 25m39s timing if there is a grotesque amount of time being spent in MPI >> calls? Or, is the slowdown due to non-MPI portions? > > > Just to add my two cents: if this job *can* be run on less than 8 > processors (ideally, even on just 1), then I'd recommend doing so. That is, > run it with OpenMPI and with MPICH2 on 1, 2 and 4 processors as well. If > the single-processor jobs still give vastly different timings, then perhaps > Eugene is on the right track and it comes down to various computational > optimizations and not so much the message-passing that's make a difference. > Timings from 2 and 4 process runs might be interesting as well to see how > this difference changes with process counts. > > I've seen differences between various MPI libraries before, but nothing > quite this severe either. If I get the time, maybe I'll try to set up > Gromacs tonight -- I've got both MPICH2 and OpenMPI installed here and can > try to duplicate the runs. Sangamesh, is this a standard benchmark case > that anyone can download and run? > Yes. ftp://ftp.gromacs.org/pub/benchmarks/gmxbench-3.0.tar.gz > > > Cheers, > - Brian > > > Brian Dobbins > Yale Engineering HPC > > > _______________________________________________ > users mailing list > us...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/users >
