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

[Jeff Hammond]

How does what you want not meet the definition of "implementation defined"
rather than "defined"?  I know this is semantic hair-splitting, but you are
not proposing to define the semantics of RMA in the way that one normally
thinks of the term "defined".  I don't see how your "definition" is any
more of a definition than saying that one can either use MPI_RECV or "some
combination of function calls and instructions that would allow the user to
receive the data and set the message queue in the proper state as if it
were RECVed" since what you are saying we're going to "define" is the user
can employ MPI_WIN_SYNC or "some combination of function calls and
instructions that would allow the user to synchronize the public and
private windows in the same manner as WIN_SYNC would do".

Jeff


On Tue, Aug 27, 2013 at 11:38 AM, Underwood, Keith D <
keith.d.underwood at intel.com> wrote:

>  Yes, I want it to be defined.  I don’t think that version of defined is
> a problem.  The definition just has to happen in terms of what is in memory
> and say “an implementation might reorder your loads in fun and exciting
> ways” ;-)  This is pretty close to just saying the public and private
> window are the same.  ****
>
> ** **
>
> Undefined in the way MPI phrases it allows a unified where it is
> impossible to use it without the MPI_WIN_SYNC.  That isn’t ok.****
>
> ** **
>
> *From:* mpiwg-rma [mailto:mpiwg-rma-bounces at lists.mpi-forum.org] *On
> Behalf Of *Jeff Hammond
> *Sent:* Tuesday, August 27, 2013 2:31 PM
> *To:* Pavan Balaji
> *Cc:* MPI Forum
>
> *Subject:* Re: [mpiwg-rma] FW: [Mpi3-rma] [EXTERNAL] Re: MPI-3 UNIFIED
> model updates****
>
>  ** **
>
> Keith's definition is not a definition in the sense of MPI semantics being
> "defined".  What he is proposing is to be pedantic about the fact that the
> user may want to rely upon implementation-defined behavior to realize the
> best performance or to avoid changing existing SHMEM code.****
>
> ** **
>
> The MPI standard isn't defining something if it's not explicitly defined
> in the standard.  Therefore, it must be called "undefined".  If you or
> Keith want to call this "defined" behavior, then I'm going to insist that
> it be defined in the usual sense, which means the text of the standard will
> enumerate the behavior of MPI in an architecture-independent way.****
>
> ** **
>
> Jeff****
>
> ** **
>
> On Tue, Aug 27, 2013 at 11:19 AM, Pavan Balaji <balaji at mcs.anl.gov> wrote:
> ****
>
>
> On 08/27/2013 12:57 PM, Jeff Hammond wrote:****
>
> The MPI standard will not define by what mechanism the SHMEM
> implementation will establish the necessary consistency.  This is what I
> mean by undefined = implementation-defined.  I do not think that Keith
> is proposing to enumerate all processor memory models and the
> appropriate fences required to achieve the affect of win_sync but at
> lower cost.  Thus, it is the implementation - or perhaps more
> accurately, the platform on which the implementation resides - that will
> define these semantics.****
>
> ** **
>
> Here's what I understood from Keith --
>
> He wants a statement in the standard that says the application can do
> platform-specific memory consistency to synchronize the public and private
> windows in UNIFIED.
>
> I do agree that that's a very flimsy statement and doesn't really mean
> much.  But I'm calling it a definition, while I think you are saying that
> it's pretty much undefined.
>
> I like leaving it totally undefined better than the above "definition".***
> *
>
>
>
>  -- Pavan
>
> --
> Pavan Balaji
> http://www.mcs.anl.gov/~balaji****
>
>
>
> ****
>
> ** **
>
> --
> Jeff Hammond
> jeff.science at gmail.com ****
>
> _______________________________________________
> mpiwg-rma mailing list
> mpiwg-rma at lists.mpi-forum.org
> http://lists.mpi-forum.org/mailman/listinfo.cgi/mpiwg-rma
>



-- 
Jeff Hammond
jeff.science at gmail.com
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