[MPI3 Fortran] [Mpi-comments] MPI 3.0: Fortran 2008 interface - issue with the LOGICAL kind

[Jeff Squyres (jsquyres)]

On Mar 26, 2013, at 12:16 PM, Bill Long <longb at cray.com> wrote:

> I don't think there is a problem.  To accommodate -i8 you have to recompile the MPI module with the -i8 flag set.  We've been shipping two mpi modules as long as I can remember; the compiler scripts pick the right one based on how the user code is compiled.  Same as how we select the right version of other libraries that also have Fortran default type arguments. Within the MPI module source the values of MPI_INTEGER and the similar data types for other Fortran default types are set based on detection of the actual sizes of the default types (which change with the compiler options).  If you are using the module compiled with -i8, MPI_INTEGER will encode the information for an 8-byte integer.


But not all Fortran types have corresponding C types (from a standards/strict perspective), right?  (e.g., logical -- and I'm not sure about the various complex types...?)  So the MPI implementation needs to know that it has to create some synthetic / "good enough" MPI datatypes based on actual Fortran types.

...at least, that's what OMPI does...

-- 
Jeff Squyres
jsquyres at cisco.com
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