Another question about MPI

[pwflanigan]

I know this is something that has been discussed a lot (#2158, #2852, #2370, #2437, etc.), but I'm still confused. I'll try to ask a simple, straightforward question: I'm running MEEP on an HPC (Purdue's Anvil). When I submit a SLURM job with a line like

mpirun -np 4 python my_code.py

the output file has four identical copies of the standard output. Does this indicate that something is wrong with the parallelization, or is it actually splitting the problem into chunks like its supposed to? Does this indicate that MEEP was installed incorrectly, or can it be fixed by adjusting the SLURM script? Or is it not a problem at all? And looking at #2437, could adding if mp.am_master(): be useful?

[stevengj]

Probably Meep is not installed with MPI support enabled, because import meep automatically silences stdout except on the "master" process (0).

You can check meep.with_mpi() to see if it is compiled with MPI support. (And make sure mpi4py is installed too.)