Can PETSc detect the number of CPUs on each computer node?

Matthew Knepley knepley at
Tue Jun 16 12:53:35 CDT 2009

On Tue, Jun 16, 2009 at 12:38 PM, xiaoyin ji <sapphire.jxy at> wrote:

> Hi there,
> I'm using PETSc MATMPIAIJ and ksp solver. It seems that PETSc will run
> obviously faster if I set the number of CPUs close to the number of
> computer nodes in the job file. By default MPIAIJ matrix is stored in
> different processors and ksp solver will communicate for each step,
> however since on each node several CPUs share the same memory while
> ksp may still try to communicate through network card, this may mess
> up a bit. Is there any way to detect which CPUs are sharing the same
> memory? Thanks a lot.

The interface for this is mpirun or the job submission mechanism.


> Best,
> Xiaoyin Ji
What most experimenters take for granted before they begin their experiments
is infinitely more interesting than any results to which their experiments
-- Norbert Wiener
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