On Feb 19, 2008, at 10:27 AM, Craig Rasmussen wrote:

Don't know if there are implementations where the MPI handle is not an integer of size of an address. Would your suggestion work if it were?

Actually, does it matter? In the MPI spec, we can just mandate this part: type, BIND(C) :: MPI_HANDLE_TYPE private ....something.... end type MPI_HANDLE_TYPE So that MPI_HANDLE_TYPE is required to be available in Fortran. What exactly it contains and how it is implemented is up to each MPI implementation. They can make it an equivalent of a C pointer, or a C int, or whatever they need. Let's take two obvious concrete examples: 1. Open MPI defines C MPI communicators as typedef struct ompi_comm_t * MPI_Comm; As such, Open MPI's F03 interface for communicators would be: type, BIND(C) :: MPI_COMMUNICATOR private type(C_PTR) :: handle end type MPI_COMMUNICATOR 2. MPICH2 defines C MPI communicators as ints. Hence, MPICH2's F03 interface for communicators would be: type, BIND(C) :: MPI_COMMUNICATOR private type(C_INT) :: handle end type MPI_COMMUNICATOR Is that right? If so, my only concern is that the compiler can automatically translate between the F03 and C values without the need for a translation layer provided by the MPI implementation. That is, a Fortran function of MPI_SEND that takes an MPI_COMMUNICATOR type parameter (as described above) can be automatically translated to the appropriate MPI_Comm type in C. That is one of the goals of this interface, after all. The reason that I mention this is because I'm a C guy, not a Fortran guy, and the above "type, BIND(C)..." stuff looks analogous to a struct to me. If it is, and if that binding contains more than one member, are we ok on the "compiler will automatically translate it" front as long as there is only one member in the binding? An excellent topic for the teleconference! :-) -- Jeff Squyres Cisco Systems