Common problems

Hanging when using ProcessPoolExecutor

(Written 05/12/2021)

If you use concurrent.futures.ProcessPoolExecutor, then you cannot use openMP within pyscf. Fixes:

• Set the environment variable export OPENMP_NUM_THREADS=1 before running
• Instead use loky.get_reusable_executor (you have to install the loky package)
• Instead use mpi4py.futures.MPIPoolExecutor