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

Jeff Squyres (jsquyres) jsquyres at cisco.com
Thu Mar 21 10:47:58 CDT 2013

On Mar 21, 2013, at 8:44 AM, "Schulz, Martin" <schulzm at llnl.gov> wrote:

> I feared that this would be the reaction and that were also my original reservations. From a tools perspective this would indeed be the easiest and cleanest solution, but I can see the downside. Implementation effort for rewriting aside (which I realize is important), do you expect a large performance impact, though?

I can't speak for NEC.

The reason we did it this was in OMPI was not for performance -- it was for implementation-specific reasons.  That is, there are some cases where we want to do something different for the Fortran implementation vs. the C implementation.  One obvious example of this is for just about any function involving callbacks.

MPICH may not have this issue because their handles are always integers, but for OMPI, C handles=pointers/F handles=integers, so we have to do some swizzling/de-swizzling for the conversion.

Jeff Squyres
jsquyres at cisco.com
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