static bool match_common(MPI_Request req, MPI_Request sender, MPI_Request receiver);
static bool match_types(MPI_Datatype stype, MPI_Datatype rtype);
static bool match_common(MPI_Request req, MPI_Request sender, MPI_Request receiver);
static bool match_types(MPI_Datatype stype, MPI_Datatype rtype);