[Mpi-comments] "safe" tag in MPI_Intercomm_create

[Rolf Rabenseifner]

If we ever make this routine a nonblocking collective,
the tag may be needed again, because I expect that
then, no two nonblocking MPI_Intercomm_create can be 
active with the same tag.

This means, one may include backward and future use.
It should not be a dummy. It should continue to
require to have a valid tag, i.e., in the tag space 
between 0 and the value returned with inquiring MPI_TAG.

Rolf

----- Original Message -----
> From: "William Gropp" <wgropp at illinois.edu>
> To: "Comments on the MPI Standard" <mpi-comments at lists.mpi-forum.org>
> Sent: Friday, September 7, 2012 5:55:14 PM
> Subject: Re: [Mpi-comments] "safe" tag in MPI_Intercomm_create
> Is this an MPI-next or a ticket zero change? Is this a chapter
> committee change (I think it should be, but I don't want to make that
> call unilaterally)?
> 
> Bill
> 
> William Gropp
> Director, Parallel Computing Institute
> Deputy Director for Research
> Institute for Advanced Computing Applications and Technologies
> Paul and Cynthia Saylor Professor of Computer Science
> University of Illinois Urbana-Champaign
> 
> 
> 
> On Sep 6, 2012, at 5:36 PM, Jim Dinan wrote:
> 
> > Hi Bill,
> >
> > That's right, the tag argument is vestigial as of MPI 3.0. I agree
> > with your suggestion of changing '"safe" tag' to:
> >
> > dummy - Ignored argument, retained for backward compatibility.
> >
> > ~Jim.
> >
> > On 9/6/12 5:02 PM, William Gropp wrote:
> >> I noted in ticket #305 that the argument is now ignored and
> >> retained only for backward compatibility. Deleting "safe" isn't
> >> enough.
> >>
> >> Bill
> >>
> >> William Gropp
> >> Director, Parallel Computing Institute
> >> Deputy Director for Research
> >> Institute for Advanced Computing Applications and Technologies
> >> Paul and Cynthia Saylor Professor of Computer Science
> >> University of Illinois Urbana-Champaign
> >>
> >>
> >>
> >> On Sep 6, 2012, at 1:47 PM, Jim Dinan wrote:
> >>
> >>> Hi All,
> >>>
> >>> It looks like we forgot to include the removal of the "safe"
> >>> qualifier from the tag argument as a part of the change to
> >>> MPI_Intercomm_create:
> >>>
> >>> https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/305
> >>>
> >>> Specifying that the tag argument must be "safe" was made
> >>> unnecessary by this change, since it eliminates the possibility of
> >>> interference with user communication.
> >>>
> >>> ~Jim.
> >>> _______________________________________________
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> >>> mpi-comments at lists.mpi-forum.org
> >>> http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi-comments
> >>
> >>
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-- 
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: Allmandring 30)