Cray's MPICH has a number of settings (changed using environment variables) that affect what algorithms are used, buffer space, etc. For a list of these variables and their default settings, you can set the following prior to calling
This causes rank 0 to display all MPICH environment variables and their current settings at MPI initialization time. If two or more nodes are used, MPICH/GNI environment settings are also included in the listing.
For more information about some of these settings, please see the man page for
intro_mpi. You can also find that information on Cray's documentation page (under "Introduction to MPI man pages").