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/
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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.
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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.
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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)
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