[Nek5000-users] question about efficient running nek5000

[nek5000-users at lists.mcs.anl.gov]

Mike,

Thanks for your answer!, Total grid points is 32499936, which I believe it
is greater than 20k for both cases!

Ami

On Wed, Feb 4, 2015 at 2:17 PM, <nek5000-users at lists.mcs.anl.gov> wrote:

> Hi Ami,
>
> How many nodes were in your simulation? Nek scales well if your number of
> gridpoints per core is large enough, e.g., greater than 20K or so in my
> experience.
>
> It's not clear to me if the power-of-two issue would be the cause here;
> perhaps Paul could comment.
>
> Mike
>
> On Feb 4, 2015, at 12:09 PM, <nek5000-users at lists.mcs.anl.gov>
>  wrote:
>
> > Hi,
> >
> > I ran nek5000 on 1024 CPUs which is divided to 128 nodes and 8 cores per
> node, and the same problem on 1200 CPUs with 100 nodes and 12 cores per
> node, however in second case I got lower efficiency, simulation goes slower
> about 5~8 percent!! I ran both cases on the same cluster!! Does anyone have
> any idea why I do not get higher efficiency with the higher number of CPUs
> but less nodes involved!? Could memory be a limitation here or since
> numbers in first case are power of 2, it is more efficient!?
> >
> > Thanks,
> > Ami
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