[mpiwg-rma] [Mpi3-rma] [EXTERNAL] Re: MPI-3 UNIFIED model updates

[Jim Dinan]

Here's a refinement of the earlier draft erratum that incorporates this
change:

A window synchronization (e.g. MPI_WIN_SYNC, MPI_WIN_LOCK/UNLOCK, etc.) can
be used to order load/store operations with respect to actions performed by
other processes in the target's window. * In addition, an MPI
implementation may also support the use of external operations to provide
this ordering.*  If no synchronization is performed, the ordering of
load/store operations with respect to actions performed by other processes
in the target's window is not defined.

Rationale: The local process' view of the window may not be consistent with
the window because of performance optimizations or the consistency model
provided by the system.

 ~Jim.


On Thu, Aug 29, 2013 at 3:17 PM, Pavan Balaji <balaji at mcs.anl.gov> wrote:

>
> The only difference would be that we'll add there might be other
> implementation-specific ways to do the same.
>
>  -- Pavan
>
> On Aug 29, 2013, at 10:30 AM, Barrett, Brian W wrote:
>
> > On 8/28/13 7:22 PM, "Pavan Balaji" <balaji at mcs.anl.gov> wrote:
> >
> >>
> >> On 08/28/2013 03:47 PM, Barrett, Brian W wrote:
> >>> And, further, I believe
> >>> that:
> >>>
> >>> X = 0
> >>> Win_lock_all
> >>> Recv
> >>> do { compiler_fence(); } while (0 == X);
> >>>
> >>> will eventually complete on any platform that supports UNIFIED, as the
> >>> public and private copies are eventually consistent.  This gives us the
> >>> behaviors necessary for implementing SHMEM on MPI-3.
> >>
> >> Right, good point.  We could retain the definition that the public and
> >> private windows will eventually be the same without additional MPI
> calls.
> >>
> >> With that in mind, does requiring WIN_SYNC for immediate synchronization
> >> of the two windows + a statement that there might be
> >> implementation-specific ways (e.g., memory barriers) to do the same
> >> sound reasonable from an OpenSHMEM point-of-view?
> >
> > To me, yes.
> >
> > Brian
> >
> > --
> >  Brian W. Barrett
> >  Scalable System Software Group
> >  Sandia National Laboratories
> >
> >
> >
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