On Thu, Jul 24, 2008 at 05:22:24PM -0700, Greg Lindahl wrote:
> On Mon, Jul 14, 2008 at 01:42:07PM -0400, Patrick Geoffray wrote:
>
> > AlltoAll of large messages is not a useless synthetic benchmark IMHO.
>
> AlltoAll is a real thing used by real codes, but do keep in mind that
> there are many algorithms for AlltoAll with various message sizes and
> network topologies, so it's testing both the raw interconnect and the
> AlltoAll implementation. I don't know of the results you mention were
> run with an optimal AlltoAll... do you?
Is there a single "optimal AlltoAll"?
I can imagine a handful of ways to build an AlltoAll but I suspect that
various cards, system, transports, switches, topologies ... each will
act differently on different processors and memory systems. Is there
a collection of coded algorithms that can be built into the likes of
OpenMPI? If so a simple site hook to benchmark then pick/linkto one
over another could follow.
--
T o m M i t c h e l l
Looking for a place to hang my hat.
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