...

Code execution

When using OpenMPI, binding is controlled using the –-bind-to parameter. To bind processes to cores, use --bind-to core. Possible other values can be found in the man page.

...

If no specific requests regarding the number of tasks has been done, mpirun defaults to hyperthreading and starts cores*2 processes. If a number of tasks has been specified (either with -n or with -N and/or --tasks-per-node),  an (Open) mpirun  honors this via the flag -map-by. For example:

#!/bin/bash
#SBATCH -N 4

module load gcc/9.23.0 openmpi/gcc.9/34.1.5
mpirun 4

cpus_per_node=${SLURM_JOB_CPUS_PER_NODE%\(*}

mpirun -map-by ppr:$cpus_per_node:node ./yourexe

#!/bin/bash
#SBATCH -N 4
#SBATCH --tasks-per-node 96

module load gcc/9.23.0 openmpi/gcc.9/34.1.5
mpirun4

tasks_per_node=${SLURM_TASKS_PER_NODE%\(*}

mpirun -map-by ppr:$tasks_per_node:node ./yourexe