In Slurm, is it possible to assign a different number of CPUs for every task?

Question

I am running MPI-over-openmp jobs in a Slurm cluster and I am trying to figure out a way to give different number of CPUs to each generated task. For example, let's say we run this job:

srun --nodes 1 --ntasks 2 --cpus-per-task 2 ./mpi_exe

This would generate 2 MPI processes in a single node, with 2 CPUs each. However I would like to, for example, assign 3 CPUs to the first process and 1 in the second process.

Do you know any way to achieve this?

Answer 1

Have a look at Heterogeneous Jobs. For your example, this should do the trick:

srun -N1 -n1 -c3 : -N1 -n1 -c1 ./mpi_exe