[gmx-users] Scaling on IBM/SP2 Power3

[Anton Feenstra]

David van der Spoel wrote:
> 
> On Wed, 2002-11-06 at 12:01, Anton Feenstra wrote:
> > Hi All,
> >
> >
> > I'm examining the scaling properties on our IBM/SP2 Power3 AIX4.3
> > 16/32 cpus/node machine here. Problem is, at 10 cpu's (all on one
> > node) scaling is down to 50-55% (for a 40000 atoms system). Looking
> > at the scaling benchmarks on the Gromacs page, I'd expect something
> > well above 70-80% at least! Worse, for the 2 cpu job scaling is
> > already only 94% while that should be close(r) to 100%.
> >
> > I am now trying to convince the loadleveler to run a new job with
> > MP_EAGER_LIMIT=65536, which should reduce message sending latency
> > for MPI. I've already set '#@network.mpi = csss,shared,us' and
> > MP_SHARED_MEMORY=yes, which should convince MPI to use shared
> > memory communication.
> >
> > I'd appreciate any comments and/or other suggestions!
> You are omitting the most important information: is this with PME or
> with a cut-off? With cut-off you should be able to reproduce the gmx
> benchmarks, with PME it won't be as nice... Erik (and me) are working on
> this though...

That is one of the reasons I have not (yet) switched to using PME... ;-}
So, I'm using cut-offs which should give me better scaling than I have.

-- 
Groetjes,

Anton
 ________ ___________________________________________________________
|        | Anton Feenstra                                            |
| .      | Dept. of Pharmacochemistry - Vrije Universiteit Amsterdam |
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| ' __   | Feenstra at chem.vu.nl - http://www.chem.vu.nl/afdelingen/FAR|
|  /  \  |-----------------------------------------------------------|
| (    ) | Dept. of Biophysical Chemistry - University of Groningen  |
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