Subject: bug#73649: OpenMPI + mpi4py broken: rank=0

From: Lars Bilke <[email-masked]>
Date: Tue, 10 Dec 2024 14:03:44 +0100

The issue seems that openmpi is version 5.x but mpi4py is compiled against version 4.x. You can get a consistent version by using this flag: --with-input=openmpi=[email-masked].  I could fix the issue with this call:

guix shell python python-mpi4py openmpi \
  --with-input=openmpi=[email-masked] -- \
  mpirun -n 12 python3 ...