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_at_[hidden] [mailto:mpi-21-bounces_at_[hidden]] On Behalf Of Rolf Rabenseifner Sent: Thursday, January 31, 2008 10:49 AM To: mpi-21_at_[hidden] 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_at_[hidden] 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_at_[hidden] http://lists.cs.uiuc.edu/mailman/listinfo/mpi-21