Greg Lindahl wrote:
On Mon, May 11, 2009 at 05:56:43PM -0400, Gus Correa wrote:
However, here is somebody that did an experiment with increasing
values of N, and his results suggest that performance increases
logarithmically with problem size (N), not linearly,
saturating when you get closer to the maximum possible for your
current memory size.
This is well-known. And of course faster interconnect means that you
get closer to peak at smaller problem sizes.
>
> -- greg
>
Hi Greg, list
What you said is right on my point and question:
How far/close I am now to the maximum performance that can be achieved?
Memory is 16GB/node, maximum possible is 128GB/node.
24 nodes with Infiniband III, single switch.
Max problem size w/ current memory: N=196,000,
max problem size if I had 128GB/node: N=554,000.
Current Rmax/Rpeak=83.6%, and I've read the comment that anything
below 85% is not good enough (for a "small cluster" I presume).
So, is 85% feasible?
Is 85% the top?
Imagining the nodes had 128GB, N=554,000,
what is your guess for Rmax/Rpeak?
(YMMV is not an answer! :) )
Many thanks,
Gus Correa
PSs - The problem with this HPL thing is that it becomes addictive,
and I need to go do some work, production, not tests, tests, tests ...
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Gustavo Correa
Lamont-Doherty Earth Observatory - Columbia University
Palisades, NY, 10964-8000 - USA
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