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

[xiaoyin ji]

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.

Best,
Xiaoyin Ji