From: "Rajeev Thakur" <thakur@XXXXXXXXXXX>
Date: January 31, 2008 11:37:37 AM CST
To: "'Mailing list for discussion of MPI 2.1'" <mpi-21@XXXXXXXXXXX>
Subject: Re: [mpi-21] Ballot 4 - User defined datarep - was Re:  
Question toMPI/IO
Reply-To: "Mailing list for discussion of MPI 2.1" <mpi-21@XXXXXXXXXXX>

>   Then in subsequent calls to the conversion function,
>   MPI will increment the value in position by the count of items
>   converted in the previous call, and userbuf is kept unchanged.

Maybe we should be more clear and say that "the userbuf pointer is left
unchanged"

Rajeev


> -----Original Message-----
> From: mpi-21-bounces@XXXXXXXXXXX
> [mailto:mpi-21-bounces@XXXXXXXXXXXX On Behalf Of Rolf Rabenseifner
> Sent: Thursday, January 31, 2008 10:49 AM
> To: mpi-21@XXXXXXXXXXX
> Subject: [mpi-21] Ballot 4 - User defined datarep - was Re:
> Question toMPI/IO
>
> This is a proposal for MPI 2.1, Ballot 4.
>
> I'm asking especially
>   Hubert Ritzdorf, Jean-Pierre Prost, John May, Bill Nitzberg,
> the participants of the email-discussion in 1999, to review
> this proposal.
>
> This is a follow up to:
>   Interpretation of user defined datarep
>   in
> http://www.cs.uiuc.edu/homes/wgropp/projects/parallel/MPI/mpi-
> errata/index.html
> with mail discussion in
>
> http://www.cs.uiuc.edu/homes/wgropp/projects/parallel/MPI/mpi-
> errata/discuss/datarep/
> ___________________________________
>
> Proposal:
> MPI-2.0 Sect. 9.5.3 User-defined Data Representations, page 254,
> lines 13-15 read:
>   Then in subsequent calls to the conversion function,
>   MPI will increment the value in position by the count of items
>   converted in the previous call.
>
> but should read:
>   Then in subsequent calls to the conversion function,
>   MPI will increment the value in position by the count of items
>   converted in the previous call, and userbuf is kept unchanged.
>
> ___________________________________
> Rationale for this clarification:
>   It was not clear, whether the userbuf pointer must also be moved
>   in the subsequent calls. This clarification was already done in
>   1999 and should already be implemented in existing implementations
>   of user-defined data representations.
> ___________________________________
> Total text page 254 lines 8-15:
>   If MPI cannot allocate a buffer large enough to hold all the
>   data to be converted from a read operation, it may call the
>   conversion function repeatedly using the same datatype and
>   userbuf, and reading successive chunks of data to be converted
>   in filebuf. For the first call (and in the case when all the data
>   to be converted fits into filebuf), MPI will call the function
>   with position set to zero. Data converted during this call will
>   be stored in the userbuf according to the first count data items
>   in datatype. Then in subsequent calls to the conversion function,
>   MPI will increment the value in position by the count of items
>   converted in the previous call,
>   (new text added:)
>   and userbuf is kept unchanged.
> ___________________________________
>
> Best regards
> Rolf
>
>
> Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner@XXXXXXX
> 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)
> _______________________________________________
> mpi-21 mailing list
> mpi-21@XXXXXXXXXXX
> http://lists.cs.uiuc.edu/mailman/listinfo/mpi-21
>
>

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