However, if you all already think that MPI_Request_free is bad, then what do you think about the evil MPI_Cancel?

MPI_Cancel is a performance hint as far as I'm concerned, one that is frequently ignored. Can you point to any semantic difficulties with it? Greg Bronevetsky Post-Doctoral Researcher 1028 Building 451 Lawrence Livermore National Lab (925) 424-5756 [email protected]