OSError: libmpi_cxx.so.40: cannot open shared object file: No such file or directory while import torch

[adrianwojdat]

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/local/lib/python3.7/dist-packages/torch/__init__.py", line 135, in <module>
    _load_global_deps()
  File "/usr/local/lib/python3.7/dist-packages/torch/__init__.py", line 93, in _load_global_deps
    ctypes.CDLL(lib_path, mode=ctypes.RTLD_GLOBAL)
  File "/usr/lib/python3.7/ctypes/__init__.py", line 356, in __init__
    self._handle = _dlopen(self._name, mode)
OSError: libmpi_cxx.so.40: cannot open shared object file: No such file or directory

To solve this problem we need to reinstall openmpi

sudo apt-get install --reinstall openmpi-bin libopenmpi-dev

[nikrtyd]

Quick note for Fedora/other RH-based distro users:

Sometimes this error shows up even if openmpi and openmpi-devel packages were already installed.
To fix that, you should add the path to OpenMPI libraries to LD_LIBRARY_PATH:

1. Open the config file: sudo nano /etc/ld.so.conf.d/openmpi-x86_64.conf.
2. Add /usr/lib64/openmpi/lib if it doesn't exist.