> On 24 Oct 2017, at 06:21, Barry Smith <[email protected]> wrote: > >>>> - With PetscSFBcastBegin() / PetscSFBcastEnd() you currently still have to >>>> use the C MPI types in the Fortran calling code, rather than the Fortran >>>> ones. I think it is a bit confusing to have to mix the two up in the same >>>> code. If you put MPI_INTEGER instead of MPI_INT for example, it dies in >>>> F90Array1dAccess() with 'unsupported MPI_Datatype'. Could the Fortran MPI >>>> types be supported in these routines just by adding them as alternatives >>>> into the conditionals? >>> Hmm, Jed will need to provide wisdom the Linux manual page for MPI_INTEGER >>> clearly states: >>> >>> Note that the Fortran types should only be used in Fortran programs, and >>> the C types should only be used in C programs. For example, it is in error >>> to use MPI_INT for a Fortran INTEGER. Datatypes are of type MPI_Datatype in >>> C and of type INTEGER in Fortran. >>> >>> If this is true then there is no place we can do the change properly. >> >> Yes, I first thought that MPI_Type_f2c() would convert Fortran MPI datatypes >> to the C ones (e.g. turn MPI_INTEGER into MPI_INT), so that the C side of >> the interface wouldn't have to worry about the Fortran MPI datatypes, but it >> doesn't really seem to do that. > > Do did I. Its existence seems to contradict the statement in the Linux > manual page. Well wait for Jed.
A fortran INTEGER may have a different width to a C int. Hence the distinction. The MPI_XXX_f2c functions convert handles on the fortran side to handles on the C side (MPI_XXX_c2f does the opposite). Perhaps the standard sheds some light: Moving handles from Fortran to C http://mpi-forum.org/docs/mpi-3.1/mpi31-report/node446.htm#Node446 Interlanguage communication http://mpi-forum.org/docs/mpi-3.1/mpi31-report/node456.htm#Node456 Lawrence
