[Mpi-forum] which WG for generalized requests?

Sun Nov 23 09:29:35 CST 2014

I merely meant that the content of the proposal has clearly been
iterated upon by a number of people and reached a steady state, even
if that state has issues.

The purpose of my comment was to avoid making the original greq
proposal more complicated by adding persistence.  I look forward to
new tickets on persistent greqs.

As for your technical comments on the proposal, I will add them to the
ticket for posterity.

Jeff

On Sat, Nov 22, 2014 at 11:01 PM, George Bosilca <bosilca at icl.utk.edu> wrote:
> I question the stability claim regarding this new ticket.
>
> I was part of the original greq working group with Rob and Darius.
> Unfortunately few notes remains from our meeting. If I recall correctly we
> dropped the ball on this proposal for two reasons.
> 1) The potential use of MPI functions in the greq library. If the greq
> library uses MPI for its own purposes, it has the potential to
> expect/require some form of MPI progress (as it will have to call MPI_Test
> or MPI_Wait) deep inside the greq progress function, function which is
> called from the MPI progress. This lead to a recursive stack in the MPI
> progress that was deemed undesirable and potentially error-prone.
> 2) The major assumption of the proposal, threads being undesirable, seemed
> to be in contradiction with the hardware evolution (and with the fact that
> some libraries had async progress).
>
> Moreover, the proposal was extremely unclear how the greq progress function
> interacts with the default progress engine of any MPI library other than
> MPICH, and about how often the progress functions should be called,
> especially when testing or waiting for multiple requests. Without such
> guarantees it is almost impossible to write portable and efficient libraries
> based on greq.
>
>   George.
>
>
> On Sat, Nov 22, 2014 at 6:37 PM, Jeff Hammond <jeff.science at gmail.com>
> wrote:
>>
>> The greq ticket is quite stable and I'd like to move forward with it
>> without adding baggage.
>>
>> Let's figure out more details of persistence before linear-combining it
>> with other features.
>>
>> Jeff
>>
>> Sent from my iPhone
>>
>> > On Nov 22, 2014, at 4:24 PM, Anthony Skjellum <skjellum at auburn.edu>
>> > wrote:
>> >
>> > Hi, I think we should put generalized requests in the Persistent group
>> > :-)
>> > Seriously, I think we need persistent generalized requests.  Perhaps we
>> > can compare notes offline.
>> >
>> > I really don't which group it goes in, but if we are revisiting GREQs we
>> > should consider persistent ones.
>> >
>> > Tony
>> >
>> >
>> >
>> > Anthony Skjellum, PhD
>> > Professor of Computer Science and Software Engineering
>> > COLSA Professor of Cybersecurity and Information Assurance
>> > Director of the Auburn Cyber Research Center and Lead Cyber Scientist
>> > for Auburn
>> > Samuel Ginn College of Engineering
>> > Auburn University
>> > skjellum at auburn.edu or skjellum at gmail.com
>> > cell: +1-205-807-4968 ; office: +1-334-844-6360
>> >
>> >
>> > CONFIDENTIALITY: This e-mail and any attachments are confidential and
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>> >
>> > ________________________________________
>> > From: mpi-forum [mpi-forum-bounces at lists.mpi-forum.org] on behalf of
>> > Jeff Hammond [jeff.science at gmail.com]
>> > Sent: Saturday, November 22, 2014 6:02 PM
>> > To: Main MPI Forum mailing list
>> > Subject: Re: [Mpi-forum] which WG for generalized requests?
>> >
>> > Martin:
>> >
>> > Can you assign one of the two slots for the large-count WG on Monday
>> > to be a joint meeting with the greq WG?  Again, this assumes Fab will
>> > not veto this plan...
>> >
>> > One of my main motivations for better greqs is large-count nonblocking
>> > collectives, so it makes sense to me to combine the discussion.  The
>> > other motivation for this at the San Jose meeting is that there's not
>> > time for a separate greq WG session since I'm otherwise obligated on
>> > Tuesday and it seems imprudent to overlap with WGs that Pavan is
>> > driving since he has expressed interest.
>> >
>> > Thanks!
>> >
>> > Jeff
>> >
>> >> On Sat, Nov 22, 2014 at 3:44 PM, Jeff Hammond <jeff.science at gmail.com>
>> >> wrote:
>> >> Ok.  Fab is currently the greq WG lead and I understand he's not going
>> >> to be absent from the Forum for a while (not immediately).
>> >>
>> >> Martin: Can you assign Pavan and/or me as the WG lead, assuming Fab
>> >> consents to it?
>> >>
>> >> Thanks,
>> >>
>> >> Jeff
>> >>
>> >>> On Sat, Nov 22, 2014 at 3:38 PM, Balaji, Pavan <balaji at anl.gov> wrote:
>> >>>
>> >>> It might make more sense to revive the generalized requests WG.  I'm
>> >>> very interested in helping drive the extended generalized requests proposal,
>> >>> whichever WG it ends up being in.
>> >>>
>> >>>  -- Pavan
>> >>>
>> >>>> On Nov 22, 2014, at 5:34 PM, Jeff Hammond <jeff.science at gmail.com>
>> >>>> wrote:
>> >>>>
>> >>>> I guess there is an inactive WG for generalized requests, but perhaps
>> >>>> it makes more sense to discuss in the context of the active p2p or
>> >>>> hybrid WG.
>> >>>>
>> >>>> Does anyone have any comments on this?
>> >>>>
>> >>>> The relevant ticket is
>> >>>> https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/457.
>> >>>>
>> >>>> My motivation for revisiting this issue is that I've found a number
>> >>>> of
>> >>>> problems that can be addressed with MPICH-style generalized requests,
>> >>>> including large-count nonblocking collectives.
>> >>>>
>> >>>> Thanks,
>> >>>>
>> >>>> Jeff
>> >>>>
>> >>>> --
>> >>>> Jeff Hammond
>> >>>> jeff.science at gmail.com
>> >>>> http://jeffhammond.github.io/
>> >>>> _______________________________________________
>> >>>> mpi-forum mailing list
>> >>>> mpi-forum at lists.mpi-forum.org
>> >>>> http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi-forum
>> >>>
>> >>> --
>> >>> Pavan Balaji  ✉️
>> >>> http://www.mcs.anl.gov/~balaji
>> >>>
>> >>> _______________________________________________
>> >>> mpi-forum mailing list
>> >>> mpi-forum at lists.mpi-forum.org
>> >>> http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi-forum
>> >>
>> >>
>> >>
>> >> --
>> >> Jeff Hammond
>> >> jeff.science at gmail.com
>> >> http://jeffhammond.github.io/
>> >
>> >
>> >
>> > --
>> > Jeff Hammond
>> > jeff.science at gmail.com
>> > http://jeffhammond.github.io/
>> > _______________________________________________
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-- 
Jeff Hammond
jeff.science at gmail.com
http://jeffhammond.github.io/