[MPIWG Fortran] Another MPI_SIZEOF question

[William Gropp]

This naming corresponds to MPI-3 but not to the use in MPI-1 nor to what some users may still want, which is what Jeff is talking about.  

And note: When the original MPI Fortran interface was defined, it was known not to be standard conformant - in fact, I raised that issue and raised a straw man alternative that was not accepted by the MPI Forum.  The fact at the time was that it was widely recognized that Fortran's (meaning Fortran 77) strict rules with the absence of any escape combined with no real general data mechanism, needed by many different libraries, not just MPI, made the type checking rules impractical, and virtually no compiler of the time implemented this check (the only one I knew of was WATFOR, and you could turn it off). 

Despite this, many applications were written using Fortran.  Those applications in practice, despite not conforming to the letter of the standard, were portable and contributed to the success of MPI.  I don't find comments about "MPI never supported Fortran" to be useful, even if they are technically true.

In my opinion, the use of "mpif.h" should have been to support existing programs in their existing compilation environments.  That might be fixed-format early Fortran, either Fortran 77 or perhaps Fortran 90 or Fortran 95. The goal of MPI-3 should have been to ensure that new programs used the mpi or mpi_f08 modules and that existing programs could continue to be used.  That is *not* the situation that we have now.   As far as I can tell from the requirement that MPI_SIZEOF be supported, mpif.h also requires Fortran 2008 + TS29113, meaning that many legacy MPI programs cannot be compiled with a standard conforming MPI implementation and a Fortran compiler that implements only, say, Fortran 2008 (but not the TS29113, which is *not* part of the standard) or Fortran 2003.  

Bill

William Gropp
Director, Parallel Computing Institute
Thomas M. Siebel Chair in Computer Science
University of Illinois Urbana-Champaign





On Jun 10, 2014, at 2:44 PM, Jeff Squyres (jsquyres) wrote:

> On Jun 10, 2014, at 8:35 AM, Jeff Hammond <jeff.science at gmail.com> wrote:
> 
>> What shorthand will you permit for what is meant when Bill and I refer
>> to Fortran 77 support in MPI that distinguishes it from F90 and F08
>> module support?
> 
> I usually say "the mpif.h interface", "the (Fortran) mpi module", and "the mpi_f08 module".  Indeed, I have renamed the "ompi/mpi/f77" and "ompi/mpi/f90" directories from previous versions of OMPI to "ompi/mpi/fortran/mpifh" and "ompi/mpi/fortran/use-mpi".  
> 
> Meaning: I have seen the error of my ways and corrected myself.  You can, too.  :-)
> 
> -- 
> 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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