[petsc-users] Very poor speed up performance

[Satish Balay]

On Wed, 22 Dec 2010, Yongjun Chen wrote:

> Satish,
> 
> I have reconfigured the PETSC with –download-mpich=1 and
> –with-device=ch3:sock. The results show that the speed up can now remain
> increasing when computing cores increase from 1 to 16. However, the maximum
> speed up is still only around 6.0 with 16 cores. The new log files can be
> found in the attachment.

Perhaps this was mentioned eariler. Performance doesn't scale with
number of cores. [its depends on both scalable compute unites -aka
cores, as well as scalable memory modules]

When the hardware is not designed to provide scalable performance -
expecting it is wrong. The goal should be to extract max performance
out of a given piece of hardware - not scalable performance.

Wrt with-device=ch3:sock - it might not be the best performer for
shared memory Try the default 'device=ch3:nemsis'

Satish