[Mpi-forum] MPI Ain't and MPI 3.1

[Jim Dinan]

Hi Nick,

I've just gotten around to updating the ticket with feedback from the June
meeting.  My apologies, the ticket was way out of sync with the progress on
this issue.  I'm hopeful that the new proposal text addresses your concerns
with respect to segmented and tagged architectures:

https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/349

The solution you described is similar to "proposed solution #2" on the
ticket, which won't work for Fortran, because Fortran lacks the unsigned
integers we would need for the MPI_Disp type.

 ~Jim.



On Wed, Jul 17, 2013 at 8:03 AM, N.M. Maclaren <nmm1 at cam.ac.uk> wrote:

> On Jul 16 2013, Jim Dinan wrote:
>
>>
>> I apologize for the long-delayed follow-up from our last meeting on how to
>> handle the MPI Aint arithmetic ticket (tt #349).  At the last meeting, we
>> all agreed that this is an important fix that we would like to get out
>> ASAP, but we weren't sure how to do it.  I wanted to resume that
>> discussion
>> on the mailing list to get broader feedback and help move the discussion
>> along in between meetings, if we can.
>>
>
> This isn't about the procedure, but about the proposed solution. I think
> that it is a serious mistake, and merely compounds the problems caused by
> MPI_BOTTOM. The simplest resolution would be that the conversion functions
> would take a window argument, as well, and that the
> Aint/address/displacement were required to be associated with that window.
> E.g.:
>
>    int MPI_Get_disp(const void *location, MPI_Disp *disp, MPI_Win win);
>    int MPI_Aint_to_disp(MPI_Aint aint, MPI_Disp *disp, MPI_Win win);
>    int MPI_Disp_to_aint(MPI_Disp disp, MPI_Aint *aint, MPI_Win win);
>
> The point here is that even C still supports segmented and tagged memory
> architectures. Currently, they are in abeyance, but they still exist and
> they may return to the mainstream any time. The wording in the C (and even
> C++) standard is phrased the way it is specifically to allow for such
> things. Fortran, of course, has always supported them, and more.
>
>
> Regards,
> Nick Maclaren.
>
>
>
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