[MPIWG Fortran] MPI_SIZEOF: Errata required (was: Another MPI_SIZEOF question)

[Bill Long]

On Jun 11, 2014, at 3:07 PM, Jeff Squyres (jsquyres) <jsquyres at cisco.com> wrote:

> On Jun 9, 2014, at 8:31 PM, Jeff Squyres (jsquyres) <jsquyres at cisco.com> wrote:
> 
>> Yeah, I kinda came to that same conclusion over the weekend (that OMPI's MPI_SIZEOF support in mpif.h would have to depend on which Fortran compiler is used).  Urrrgh...
> 
> 
> Actually, this doesn't work, either.  If you have an mpif.h that contains an "INTERFACE MPI_Sizeof", the compiler will treat it differently depending on whether it is included from source.f or source.f90 (and probably other variants, too).  Gaahhh!


Not sure why you say this.  Unless the lines get too long because of long names, you can write an include file so that it works for both fixed and free source forms.  The assumed source form is the only distinction to the compiler between source files that end in .f and .f90.


> 
> This means that it is not possible -- and has never been possible -- to have an MPI-3.0 compliant MPI_SIZEOF interface in mpif.h.  An errata is therefore required.
> 
> I open to suggestions.
> 
> 1. One obvious possibility is to re-instate "extended Fortran support"-like language, a la MPI-2.2.  This does not make it possible to have MPI_SIZEOF in mpif.h, however, so I don't think it really solves the problem.
> 
> 2. Another possibility is to say that MPI_SIZEOF is only available in the mpi and mpi_f08 modules (e.g., add an exception in MPI-3.x 17.1.4 saying that MPI_SIZEOF support is excluded from mpif.h).  Per Bill Gropp's email (http://lists.mpi-forum.org/mpiwg-fortran/2014/06/1572.php), we'll actually have to add exceptions / remove references to overloading for all mpif.h cases -- not just MPI_SIZEOF.

As you might recall from earlier conference calls,  I prefer that nothing be added to mpif.h that was not there before.  None of the new functions or constants.  It should be frozen at MPI 2.2 for compatibility with legacy codes.  If programmers want to use new features, they have to modify their sources anyway, and should change to using a module at the same time.

Cheers,
Bill
 
P.S.  For benefit of JH:  My family ancestry is 25% each of Dutch, Danish, English, and, yes, GERMAN !  :)


> 
> Thoughts?
> 
> -- 
> Jeff Squyres
> jsquyres at cisco.com
> For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/
> 
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Bill Long                                                                       longb at cray.com
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