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Subject: Re: [OMPI users] Performance: MPICH2 vs OpenMPI
From: Ashley Pittman (apittman_at_[hidden])
Date: 2008-10-08 10:58:12


On Wed, 2008-10-08 at 09:46 -0400, Jeff Squyres wrote:
> - 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.

Jeff,

You probably already know this but the obvious candidate here is the
memcpy() function, icc sticks in it's own which in some cases is much
better than the libc one. It's unusual for compilers to have *huge*
differences from code optimisations alone.

Ashley,