Performance Variations using MPI/Myrico

Thomas Davis tadavis at
Fri Apr 27 10:02:56 PDT 2001

Greg Lindahl wrote:
> On Wed, Apr 25, 2001 at 10:26:27AM -0700, Thomas Davis wrote:
> > We are looking for sites that run Intel Linux/SMP(dual)/MPI/Myricom 2k,
> > and have experienced performance variations.  IE, you've ran the NAS/FT
> > parallel benchmark, densely packed (using all CPU's on the nodes), and
> > noted that the runs come up different each time - and the difference is
> > not minor (as much as 80%).
> There are several sites with exactly that setup, such as the new Maui
> machine, and the new NCSA machine.

> Come to think of it, I think HPTi's bid for the last NERSC cluster RFP
> (which you have access to, yes?) has numbers for the NAS benchmarks on
> dual Intel/MPI/Lanai 7 cards. These times were not highly variable and
> we got the "right answer" compared to similar systems.

That's the problem.  We saw this in the bids - everybody had "right
answers", and very low variance.

So, we've been trying to figure out what is wrong.  We are just looking
for other people that have experienced this problem - and strangely,
everyone I've asked seems to have never seen it!

Thomas Davis		| ASG Cluster guy
tadavis at		| 
(510) 486-4524		| "80 nodes and chugging Captain!"

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