Who wrote Example 4.23 of MPI 3.1?
I propose to add the exception rather than delete that example. I do not
want to have to use real datatypes when sending nothing.
Is NULL a valid buffer handle? Can I pass null pointers when count=0?
Jeff
On Tuesday, January 12, 2016, William Gropp <wgropp(a)illinois.edu> wrote:
> The standard says that the null handles are invalid for input unless
> explicitly permitted. There’s no exemption for a datatype argument where
> the associated count is zero.
>
> Bill
>
> William Gropp
> Director, Parallel Computing Institute
> Thomas M. Siebel Chair in Computer Science
> Chief Scientist, NCSA
> University of Illinois Urbana-Champaign
>
>
>
>
>
> On Jan 12, 2016, at 9:26 PM, Jeff Hammond <jeff.science(a)gmail.com
> <javascript:_e(%7B%7D,'cvml','jeff.science(a)gmail.com');>> wrote:
>
> Is it allowed to communicate messages with
> (buffer=NULL,count=0,type=MPI_DATATYPE_NULL)?
>
> George thinks MPI_DATATYPE_NULL cannot be used even when count=0, which I
> think is ridiculous, particularly when one makes the analogy to buffer=NULL.
>
> See http://www.open-mpi.org/community/lists/users/2016/01/28255.php
> <https://urldefense.proofpoint.com/v2/url?u=http-3A__www.open-2Dmpi.org_comm…>
> for the thread in question.
>
> There is example code in MPI that uses this behavior. George and I agree
> that example text is non-normative, but I cannot imagine how this example
> came to exist without the Forum believing it to be valid.
>
> Jeff
>
> --
> Jeff Hammond
> jeff.science(a)gmail.com
> <javascript:_e(%7B%7D,'cvml','jeff.science(a)gmail.com');>
> http://jeffhammond.github.io/
> <https://urldefense.proofpoint.com/v2/url?u=http-3A__jeffhammond.github.io_&…>
> _______________________________________________
> mpi-forum mailing list
> mpi-forum(a)lists.mpi-forum.org
> <javascript:_e(%7B%7D,'cvml','mpi-forum(a)lists.mpi-forum.org');>
> http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi-forum
>
>
>
--
Jeff Hammond
jeff.science(a)gmail.com
http://jeffhammond.github.io/
The standard says that the null handles are invalid for input unless explicitly permitted. There’s no exemption for a datatype argument where the associated count is zero.
Bill
William Gropp
Director, Parallel Computing Institute
Thomas M. Siebel Chair in Computer Science
Chief Scientist, NCSA
University of Illinois Urbana-Champaign
On Jan 12, 2016, at 9:26 PM, Jeff Hammond <jeff.science(a)gmail.com> wrote:
> Is it allowed to communicate messages with (buffer=NULL,count=0,type=MPI_DATATYPE_NULL)?
>
> George thinks MPI_DATATYPE_NULL cannot be used even when count=0, which I think is ridiculous, particularly when one makes the analogy to buffer=NULL.
>
> See http://www.open-mpi.org/community/lists/users/2016/01/28255.php for the thread in question.
>
> There is example code in MPI that uses this behavior. George and I agree that example text is non-normative, but I cannot imagine how this example came to exist without the Forum believing it to be valid.
>
> Jeff
>
> --
> Jeff Hammond
> jeff.science(a)gmail.com
> http://jeffhammond.github.io/
> _______________________________________________
> mpi-forum mailing list
> mpi-forum(a)lists.mpi-forum.org
> http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi-forum
It is valid. The buffer and type are significant only when the count is non-zero.
-- Pavan
Sent from my iPhone
On Jan 13, 2016, at 11:26 AM, Jeff Hammond <jeff.science(a)gmail.com<mailto:[email protected]>> wrote:
Is it allowed to communicate messages with (buffer=NULL,count=0,type=MPI_DATATYPE_NULL)?
George thinks MPI_DATATYPE_NULL cannot be used even when count=0, which I think is ridiculous, particularly when one makes the analogy to buffer=NULL.
See http://www.open-mpi.org/community/lists/users/2016/01/28255.php for the thread in question.
There is example code in MPI that uses this behavior. George and I agree that example text is non-normative, but I cannot imagine how this example came to exist without the Forum believing it to be valid.
Jeff
--
Jeff Hammond
jeff.science(a)gmail.com<mailto:[email protected]>
http://jeffhammond.github.io/
_______________________________________________
mpi-forum mailing list
mpi-forum(a)lists.mpi-forum.org<mailto:[email protected]>
http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi-forum
Is it allowed to communicate messages with
(buffer=NULL,count=0,type=MPI_DATATYPE_NULL)?
George thinks MPI_DATATYPE_NULL cannot be used even when count=0, which I
think is ridiculous, particularly when one makes the analogy to buffer=NULL.
See http://www.open-mpi.org/community/lists/users/2016/01/28255.php for the
thread in question.
There is example code in MPI that uses this behavior. George and I agree
that example text is non-normative, but I cannot imagine how this example
came to exist without the Forum believing it to be valid.
Jeff
--
Jeff Hammond
jeff.science(a)gmail.com
http://jeffhammond.github.io/
