MPI Fails on MacOS in Some Configurations

[popescu-v]

Description

Currently, Khiops is supported on MacOS as a Conda package, which uses MPICH as its MPI backend. In some configurations, MPI_Init_thread fails when calling, indirectly, gethostbyname which fails in some cases, e.g. when using some VPN configurations.

See also:

• https://stackoverflow.com/questions/23112515/mpich2-gethostbyname-failed
• https://github.com/pmodels/mpich/issues/4710
• https://github.com/CDAT/cdms/issues/391

Questions/Ideas

• There are two possible mitigation strategies for this:
  1. Add -host localhost to the KHIOPS_MPI_COMMAND environment variable options in khiops_env (for the Conda package) on MacOS
  2. Add export MPICH_INTERFACE_HOSTNAME=localhost to khiops_env (for the Conda package) on MacOS

The second option seems preferable, as it keeps the KHIOPS_MPI_COMMAND unchanged and the same for all UNIXes.

Context

• Khiops version: 10.2.3-b.3
• OS description (use khiops -s): MacOS