[mpi-21] Ballot 4 - User defined datarep - was Re: Question toMPI/IO

[Hubert Ritzdorf]

Rajeev Thakur wrote:
>>   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
>   
I agree to Rajeev. This was the original point of my question.

Hubert
>
>   
>> -----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
>>
>>
>>     
>
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