If tests pass, and the parallel version is built, test the parallel code:
$ mpiexec -np 2 gpaw-python -c "import gpaw.mpi as mpi; print(mpi.rank)" 1 0
Many MPI versions have their own
-c option which may
invalidate python command line options. In this case
test the parallel code as in the example below.
$ ase build H -V 2 | gpaw -P 2 run -p mode=pw
This will perform a calculation for a single spin-polarized hydrogen atom parallelized with spin up on one processor and spin down on the other.