FEniCS using only one node on HPC machine. How do I use more than one?

Oh, that’s what singularity is! Our cluster has a module. I’ll go try that right now and report back.

Edit: We have singularity 3.6.0. I’ve got a .sif file running from importing the docker file:
singularity build fenics.sif docker://quay.io/fenicsproject/stable:latest
and it’s running in serial with the command
singularity exec -B $PWD fenics.sif python3 demo_poisson.py
where demo_poisson.py is the usual poisson demo in the working directory. However, I’m still having issues with mpirun very similar to what is described here (and par_test.py is the script from that thread as well):

mpirun -n 4 singularity exec -B $PWD fenics.sif python3 par_test.py 
rank / size:  0 / 1
rank / size:  0 / 1
rank / size:  0 / 1
rank / size:  0 / 1

I’ve tried a few other variations to no avail, but I think this has probably veered from the inital topic enough already.