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Subject: Re: [OMPI devel] RFC: [slightly] Optimize Fortran MPI_SEND / MPI_RECV
From: Brian W. Barrett (brbarret_at_[hidden])
Date: 2009-02-07 12:23:07

On Sat, 7 Feb 2009, Jeff Squyres wrote:

> End result: I guess I'm a little surprised that the difference is that clear
> -- does a function call really take 10ns? I'm also surprised that the
> layered C version has significantly more jitter than the non-layered version;
> I can't really explain that. I'd welcome anyone else replicating experiment
> and/or eyeballing my code to make sure I didn't bork something up.

That is significantly higher than I would have expected for a single
function call. When I did all the component tests a couple years ago, a
function call into a shared library was about 5ns on an Intel Xeon
(pre-Core 2 design) and about 2.5 on an AMD Opteron.