[Mpi3-rma] MPI_WIN_CREATE_DYNAMIC and target_disp

[Hubert Ritzdorf]

Hi,

dependent on the actual discussion, I propose a change in the current version of MPI 3.0 draft.
I send it to the rma list instead of mpi-comments list in order to get one of the discussed
changes or this change into the MPI document:

The argument target_disp in the RMA function MPI_{GET, RGET, PUT, RPUT, ACCUMULATE, ...}
is qualified as non-negative integer. I think, that this cannot be guaranteed for the Fortran version of
new function MPI_WIN_CREATE_DYNAMIC. The displacement is actually relative to
MPI_BOTTOM which is a variable in a common block or module.

The location of MPI_BOTTOM may be dependent on compiler (and possibly compiler options)
and the sequence of common blocks/modules in memory.
(Example: The memory of a window might be located in a common block, which is located
in front of the common block which contains MPI_BOTTOM).
Therefore, non-negative displacements cannot be guaranteed for windows created
by MPI_WIN_CREATE_DYNAMIC in Fortran .

The simple change would be to remove "non-negative". But I assume that a rationale would be required.

Hubert

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