[Mpi3-ft] Question about MPI_ANY_SOURCE and process failures

[Solt, David George]

err = MPI_Recv(....., rankX, ..., comm, status);

if communication to rankX fails, this receive will return with err.

Err = MPI_Recv(...., MPI_ANY_SOURCE, ..., comm, status);

When does this MPI_Recv return a failure?   When ANY rank in comm is unreachable or when ALL ranks in comm are unreachable.   Since self is always reachable, the ALL option is really NEVER.

We had been assuming ALL/NEVER but will likely change to ANY.   In such case, status points to the first failed rank that could have matched the request.

Thanks,
Dave