Does MPICH preserve the ability of doubles to hold integers up to 2^53 properly when doing MPI_{MAX,MIN}LOC over Fortran MPI_2DOUBLE_PRECISION? I see no evidence in http://www.mpi-forum.org/docs/mpi-11-html/node79.html that this isn't possible, but I guess implementations might fall back to the C implementation for MPI_DOUBLE_INT under the assumption that the Fortran programmer only needs half of the bits in the second double of MPI_2DOUBLE_PRECISION. The motivation is that, until https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/319 is part of the standard, there's no way to have loc be more than a 32b int, at least from C. This hideous hack via Fortran seems like the only viable option for the time being. Thanks, Jeff -- Jeff Hammond [email protected]