[Mpi-comments] On the use of environment variables

[Bruno Kinoshita]

Hello,

I am working on a masters thesis about workflows with CWL and MPI. The
workflows I am working with can be executed with tools (CWL runners) that
try to isolate the execution of each step.

This isolation can be done, for instance, with containers. When using the
containers, some CWL runners normally remove all environment variables
(e.g., with --cleanenv with Singularity).

Before passing all variables from the host or creating a wrapper script to
control which variables are sent, I am searching for confirmation that the
environment variables used in MPI implementations are not defined in the
standard.

I read parts of the MPI 5.0 specification, and I could only find
environment variables being mentioned as one of the possible mechanisms to
solve some sort of problem. So my understanding right now is that the MPI
specification does not say implementations MUST use environment variables,
only they MAY.

Could anyone please confirm this? This is my first message in the list; I
hope I am posting in the right place. If not, I apologize.

Thank you,

Bruno
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