[Beowulf] Infiniband modular switches

Nifty niftyompi Mitch niftyompi at niftyegg.com
Sat Jul 26 23:54:20 EDT 2008


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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