[Mpi-forum] which WG for generalized requests?

Sat Nov 22 23:01:49 CST 2014

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
> >
> >
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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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