[Beowulf] Re: building a new cluster
schuang21 at yahoo.com
Fri Sep 3 18:35:10 EDT 2004
A second graph, using 16M grid points, is posted:
I have repeated the timing several times and confirmed all numbers.
However I still cannot come up with a "theory" to explain the curve for
Opteron in the case of 16M points: beyond 16 processors it goes up at
32 processors and then goes down at 64 processors. But going down is
good anyway... :-)
> --- Tim Mattox <tmattox at gmail.com> wrote:
> > Hello SCH,
> > That is an interesting graph. Are you running a representative
> > data set?
> > 2 Million gridpoints seems small compared to what I'm used to
> > CFD
> > people run on our clusters. But I don't know your code or problem
> > set,
> > so 2 Million may be just what you want to work with.
> > I say this because the wallclock times in your graph are rather
> > short, with
> > all but one of the runs on faster than 100 Mbit networks at under
> > seconds.
> > You may be seeing the job's startup overhead more than your actual
> > code's
> > behaviour.
> > If you can, try running a bigger job, and/or for more timesteps.
> > More timesteps
> > will hide the startup overhead, and a bigger job (if that is
> > representative
> > of your desired runs) should allow you to scale to larger numbers
> > nodes.
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