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

[William Gropp]

My feeling on this is (a) there have already been too many oversights because of the tremendous scope of the changes and (b) the mpif.h interface, in practice, should and will be used mostly for legacy applications - thus either defining it as similar to the original "basic" support, with any new constants, will satisfy the users without the risk of finding another MPI_SIZEOF issue.  At this point I have no confidence that there isn't something else lurking in the wings, and that argues for as conservative an approach as possible.

Bill

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





On Jun 14, 2014, at 12:49 PM, Rolf Rabenseifner wrote:

> Yes, the "Extended Support" listed of about 5 additional routines,
> but as far as I understand, MPI_SIZEOF is the only one
> that needs an INTERFACE description in mpif.h.
> 
> All other routines are without any implementation-problems.
> 
> Therefore, it would be enough to allow in the special case
> that MODULE (and INTERFACE) are not supported by the target compiler, 
> that 
> - the Fortran Support requires only mpif.h (same as in MPI-2.0), 
>   and
> - MPI_SIZEOF is not provided.
> 
> Additionally, we can restrict the MPI_SIZEOF support only 23 dimensions 
> - in mpif.h
> - or generally if TS29113 or other non-Standard methods
>   are not available,
> supposed that "DOUBLE PRECISION" is the longest
> Fortran type Name:
> 
> 123456789012345678901234567890123456789012345678901234567890123456789012
>      SUBROUTINE MPI_SIZEOF(x,n)
>      DOUBLE PRECISION x(1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,*)
> !                        1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
> What did mpich and OpenMPI in the past with MPI_SIZEOF? 
> 
> Rolf
> 
> ----- Original Message -----
>> From: "William Gropp" <wgropp at illinois.edu>
>> To: "MPI-WG Fortran working group" <mpiwg-fortran at lists.mpi-forum.org>
>> Sent: Saturday, June 14, 2014 6:36:35 AM
>> Subject: Re: [MPIWG Fortran] MPI_SIZEOF: Errata	required	(was:	Another	MPI_SIZEOF question)
>> 
>> 
>> Not quite true.  See my email, which gives specific locations in the
>> standard for the relevant text.  Note also that MPI_SIZEOF is *not*
>> the only function that is not included in the "basic" Fortran
>> support - the routines to create a type based on precision and range
>> are also not required for basic support.  
>> 
>> 
>> I think there are two options for the so-called Fortran 77 support.
>>  Continue to support the "basic" support, as defined in MPI-2, or
>> delete it entirely.  Anything else is likely to leave errors and
>> mistakes.  And while I agree with Jeff that its not good practice to
>> remove something like F77 support at a point release, I believe that
>> the language in the standard removed Fortran 77 with 3.0.  We're
>> just now recognizing that.
>> 
>> 
>> Bill
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> William Gropp
>> Director, Parallel Computing Institute Thomas M. Siebel Chair in
>> Computer Science
>> 
>> 
>> University of Illinois Urbana-Champaign
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> On Jun 13, 2014, at 10:32 AM, Rolf Rabenseifner wrote:
>> 
>> 
>> 2) The requirement of having this function in mpif.h was changed:
>> 
>>   MPI-2.0 through 2.2 requiered MPI_SIZEOF in mpif.h
>>   "unless the target compiler does not support modules
>>   or KIND-parametrized types."
>> 
>>   This restriction was removed.
>> 
>> 
>> _______________________________________________
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>> mpiwg-fortran at lists.mpi-forum.org
>> http://lists.mpi-forum.org/mailman/listinfo.cgi/mpiwg-fortran
> 
> -- 
> Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner at hlrs.de
> High Performance Computing Center (HLRS) . phone ++49(0)711/685-65530
> University of Stuttgart . . . . . . . . .. fax ++49(0)711 / 685-65832
> Head of Dpmt Parallel Computing . . . www.hlrs.de/people/rabenseifner
> Nobelstr. 19, D-70550 Stuttgart, Germany . . . . (Office: Room 1.307)
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