Inter-communicator Extensions to MPI in the MPIX

MPI is the new standard for multicomputer and cluster message passing introduced by the Message-Passing Interface Forum (MPIF) in April 1994. This paper describes the current inter-communicator interface found in MPI and the reasons for its current design. We also motivate the need for additional inter-communicator operations and introduce the extensions we have included in MPIX (MPI eXtension Library), a library of extensions to MPI that we are currently developing. Inter-communicators may be used for a variety of purposes such as in client/server applications (i.e., I/O and graphics servers) and for process management in dynamic process environments and multi-protocol implementations; MPI's de nitions are unnecessarily restrictive, so we extend them here. We discuss the inter-communicator collective operations de ned in MPIX and illustrate their use. We also discuss additional inter-communicator construction routines not in the original MPI interface, but that are provided in MPIX. Our nal contribution is a strategy for extending virtual topologies to support inter-communicators with the MPIX inter-communicator library.