I agree with your point Joel. I don't want to focus on mpirun (or SPAWN).
I don't care how an implementation decides inside MPI_INIT
how big to make COMM_WORLD. Maybe it checks an envar,
maybe the startup passes some "magic" args, maybe the MPP just
checks the partition size and says that is the how big it will be.
I want to define that if MPI_INIT is clueless to a choice to make for
COMM_WORLD it defaults to size=1 and continues rather than
aborting with an error.
My guess is the Paragon implementation of MPI_INIT is always clueful
and so you are unaffected by the proposal.