Assigning N cores per MPI rank

Question

I'm trying to assign N cores per MPI rank. I'm running an application with 256 MPI ranks, and I would like to assign 16 cores per MPI rank.

The solutions I found are useful but want me to use a rankfile and this gets tedious after a certain number of rank-core relationship.

Is there a better way to do it?

score 1 · Accepted Answer · answered May 16 '18 at 23:57

1

With Open MPI, you can

mpirun --map-by node:PE=16 ...

answered May 16 '18 at 23:57

One question : when this is done how can one access the individual processors of each rank? – AdityaG May 17 '18 at 11:29
What do you mean ? The MPI task is bound on 16 cores. It is up to the app to create threads and bind them to the 15 other cores. The OpenMP runtime can do that if you use hybrid MPI+OpenMP – Gilles Gouaillardet May 17 '18 at 11:47
yes that was what I was missing ... hybrid parallel program. This especially is useful only when the program is hybrid parallel right ? Please correct me if I am wrong. – AdityaG May 18 '18 at 09:25

1 Answers1