[Mpi3-rma] [EXTERNAL] Re: Disp_unit in allocate_shared should be returned by win_shared_query?
Hubert.Ritzdorf at EMEA.NEC.COM
Thu Jul 26 13:12:27 CDT 2012
I vote for #2.
From: mpi3-rma-bounces at lists.mpi-forum.org [mpi3-rma-bounces at lists.mpi-forum.org] on behalf of Jim Dinan [dinan at mcs.anl.gov]
Sent: Wednesday, July 25, 2012 8:45 PM
To: mpi3-rma at lists.mpi-forum.org
Subject: Re: [Mpi3-rma] [EXTERNAL] Re: Disp_unit in allocate_shared should be returned by win_shared_query?
We should try to reach a decision on this issue before the end of the
week. I think it would be helpful to hear some other opinions. So far,
we have three options to choose from:
1) Require that the displacement unit be the same at all processes for
2) Allow different displacement units at each process in shared memory
windows and allow processes to determine the displacement unit at remote
processes via MPI_Win_shared_query(). This is in addition to the MPI-2
self-query already possible with MPI_Win_get_attr(MPI_WIN_DISP_UNIT).
3) Allow different displacement units at each process in shared memory
windows and provide only the MPI-2 self-query already possible with
MPI_Win_get_attr(MPI_WIN_DISP_UNIT). Manual communication would be
needed to exchange disp_unit information.
A (very) rough summary of the discussion on this issue:
* Given that non-uniform disp_unit values are currently allowed,
processes may need to use disp_unit in address calculations.
* Requiring programmers to use the disp_unit at each process in
address calculations diminishes the usefulness of the shared memory
programming model. It's also not clear if there is a use case to
support the non-uniform disp_unit model.
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