I need to update some old codes to work with the most recent version of OpenMPI, but I'm very confused by the new --map-by system. In particular, I'm not sure how to replace --cpus-per-proc N.
Several websites have suggested using --map-by node:pe=N, but when I tried this it gives me a different result.
The original command is:
mpirun -np 3 --report-bindings --bind-to-core --cpus-per-proc 3 ./test.sh
Which gives:
[B/B/B/././././.] [./././././././.] [./././././././.] [./././././././.]
[./././././././.] [B/B/B/././././.] [./././././././.] [./././././././.]
[./././././././.] [./././././././.] [B/B/B/././././.] [./././././././.]
However, when I use the command:
mpirun -np 3 --report-bindings --bind-to core --map-by node:pe=3 ./test.sh
The output is:
[B/B/B/././././.] [./././././././.] [./././././././.] [./././././././.]
[./././B/B/B/./.] [./././././././.] [./././././././.] [./././././././.]
[././././././B/B] [B/././././././.] [./././././././.] [./././././././.]
Could someone please explain how to use the --map-by option?
To spread four MPI processes over four CPU sockets and have each process bound to three cores of the corresponding socket use:
-n 4 --map-by socket:pe=3 --bind-to core