[Nek5000-users] question about efficient running nek5000

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

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
> _______________________________________________
> Nek5000-users mailing list
> Nek5000-users at lists.mcs.anl.gov
> https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users