[Mpi3-rma] draft of a proposal for RMA interfaces

[Richard Graham]

Just to get discussion going again.  Talking with several folks I have heard
several concerns expressed about the proposal.  I think it would be good if
these (and others) could be raised on the list, so we can start discussion.
We can continue this next week in Chicago, but Vinod will not be able to
make this meeting, so an e-mail discussion will help.

Here are the issues I have hear of so far:
  - May not work well on current h/w that is not cache coherent, as it
requires a remote thread in this case.  I believe this is for the SX series
of machines, but Jesper please correct me if I am wrong here.  What would be
an alternative approach that could provide expected performance on platforms
that may require work on the remote end for RMA for correctness, and work
well on platforms that do require very specific remote cache management (or
other actions) for correctness ?
  - Concern about future high-end platforms, under that assumption that
these will not be cache coherent (and will actually have caches ­ if they
don¹t this is not a concern), and therefore this proposal is aimed at a
short-lived technical capability.
  - What is missing ?

Rich


On 9/6/08 6:06 PM, "Vinod tipparaju" <tipparajuv at hotmail.com> wrote:

> 
> 
> Rajeev,
> 
> Excellent questions.
> 
> Technically, yes. However, ARMCI does more thinking about Global Arrays.
> Particularly because of stride data transfers (multiple stride levels).
> However, I don't see why we cannot have an alternative port. The only way to
> know is to prototype the interfaces, implement Global Arrays on top of them
> and see how the interfaces fare. From superficial thinking, I think they will
> do just fine ;-). We however cannot say this about all potential
> implementations.
> 
> I am not sure if Dan Bonachea is a member of this list. I will write him a
> message if he isn't.
> 
> Thanks,
> Vinod.
> 
> ----------------------------------------
>> > From: thakur at mcs.anl.gov
>> > To: mpi3-rma at lists.mpi-forum.org
>> > Date: Sat, 6 Sep 2008 16:24:35 -0500
>> > Subject: Re: [Mpi3-rma] draft of a proposal for RMA interfaces
>> >
>> > Vinod,
>> >       Thanks for the proposal and the nice presentation. A question I had
>> > was does it meet the needs of the Global Arrays library? That is, if this
>> > were available in MPI today, would you implement Global Arrays with MPI and
>> > nothing else (not ARMCI). Similarly, it would be good to run it by Dan
>> > Bonachea and see what he has to say regarding implementing UPC.
>> >
>> > Regards,
>> > Rajeev
>> > 
>> >
>>> >> -----Original Message-----
>>> >> From: mpi3-rma-bounces at lists.mpi-forum.org
>>> >> [mailto:mpi3-rma-bounces at lists.mpi-forum.org] On Behalf Of
>>> >> Vinod tipparaju
>>> >> Sent: Thursday, September 04, 2008 1:50 AM
>>> >> To: mpi3-rma at lists.mpi-forum.org
>>> >> Subject: [Mpi3-rma] draft of a proposal for RMA interfaces
>>> >>
>>> >>
>>> >> Folks,
>>> >>
>>> >> Attached is a draft of a new proposal for MPI3-RMA interfaces
>>> >> for your perusal.
>>> >>
>>> >> Thanks,
>>> >> Vinod Tipparaju, ORNL.
>>> >>
>> >
>> > _______________________________________________
>> > mpi3-rma mailing list
>> > mpi3-rma at lists.mpi-forum.org
>> > http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi3-rma
> 
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