Possible depletion and OpenMPI conflict?

User Support
1

Hello - I’m unsure if an issue I’m running into is an error somewhere in my own installation, or a possible incompatibility between OpenMC and the version of OpenMPI I’m trying to use.

I currently have the newest dev branch of OpenMC installed in a conda environment on my machine. I don’t notice any problems with running OpenMC for problems that don’t need depletion - like a simple eigenvalue mode run. However, if I try to import openmc.depletion while using OpenMPI 5 (the newest release, as of this February, installed in a conda environment with conda install), I run into the following error (I replaced the exact file path with $CONDA_PREFIX/$HOME as appropriate when posting it here):

Traceback (most recent call last):
  File "$HOME/openmc_models/bcc_model.py", line 2, in <module>
	import openmc.deplete
  File "$CONDA_PREFIX/lib/python3.11/site-packages/openmc/deplete/__init__.py", line 11, in <module>
	from .coupled_operator import *
  File "$CONDA_PREFIX/python3.11/site-packages/openmc/deplete/coupled_operator.py", line 21, in <module>
	import openmc.lib
  File "$CONDA_PREFIX/lib/python3.11/site-packages/openmc/lib/__init__.py", line 30, in <module>
	_dll = CDLL(str(_filename))  # TODO: Remove str() when Python 3.12+
       	^^^^^^^^^^^^^^^^^^^^
  File "$CONDA_PREFIX/lib/python3.11/ctypes/__init__.py", line 376, in __init__
	self._handle = _dlopen(self._name, mode)
               	^^^^^^^^^^^^^^^^^^^^^^^^^
OSError: /lib/x86_64-linux-gnu/libmpi_cxx.so.40: undefined symbol: ompi_mpi_errors_throw_exceptions

From my initial research to try to fix this, I found that ompi_mpi_errors_throw_exceptions was not used in OpenMPI 5, like it was in OpenMPI 4. Sure enough, if I clone the environment I used above, and change nothing except downgrading OpenMPI to version 4, openmc.depletion imports and runs with no errors.

I used to have OpenMPI 4 installed, and it’s possible that there’s something I missed in uninstalling it that is causing this issue (possibly when cmake runs find package?), which is why I wanted to see if anyone else could reproduce this error on their own machine, or if it’s just an bug on my end.