[Mpi3-hybridpm] Threading homeworking / next telecon

[Sur, Sayantan]

Jeff,

I like the direction you are headed with this proposal. I was also thinking in a similar manner to improve performance of MPI apps in multi-threaded context by eliminating the requirement of locking a global shared state.

Do you think that if this concept becomes reality, you won't need "endpoints" any more (at least for your use case of extracting more performance out of 1 MPI process + many threads scenario)?

Thanks,
Sayantan

> -----Original Message-----
> From: mpi3-hybridpm-bounces at lists.mpi-forum.org [mailto:mpi3-hybridpm-
> bounces at lists.mpi-forum.org] On Behalf Of Jeff Hammond
> Sent: Monday, March 25, 2013 10:08 AM
> To: mpi3-hybridpm at lists.mpi-forum.org
> Subject: Re: [Mpi3-hybridpm] Threading homeworking / next telecon
> 
> I finally wrote up another ticket that was my attempt at a more holistic
> proposal for thread-safety.  It's a bit raw, so please try to extract the essence
> of it before poking at specific flaws.
> 
> https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/373
> 
> Jeff
> 
> On Mon, Mar 25, 2013 at 11:18 AM, Jeff Hammond
> <jhammond at alcf.anl.gov> wrote:
> > In case people aren't on the call or didn't hear me clearly,
> > https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/371 is related to
> > the two-faced issue of threads.
> >
> > Best,
> >
> > Jeff
> >
> > On Thu, Mar 14, 2013 at 4:45 PM, Rajeev Thakur <thakur at mcs.anl.gov>
> wrote:
> >> The analysis of thread safety needs of MPI routines that Bill mentioned on
> Wed is available here:
> http://wiki.mpich.org/mpich/index.php/Thread_Safety . It is referenced in
> this paper, www.mcs.anl.gov/~thakur/papers/threads-parco.pdf.
> >>
> >> Rajeev
> >>
> >> On Mar 14, 2013, at 3:00 PM, Barrett, Brian W wrote:
> >>
> >>> Hi all -
> >>>
> >>> As a reminder, there's a hybrid telecon on Monday, March 25th at
> >>> 12:00pm EDT.  During the telcon, we'll be following up from the
> >>> meeting about threading (notes below).  Before the meeting, we're
> >>> supposed to think about a couple of different issues regarding
> >>> threads and the MPI spec,
> >>> including:
> >>>
> >>>  * which MPI functions have functionality / usability deficiencies
> >>> if an MPI does not support MPI_THREAD_MULTIPLE
> >>>  * which MPI functions have use cases which present threading issues
> >>> in the presence of threads?
> >>>
> >>> Some notes from this week's working group meeting:
> >>>
> >>>  * Jeff H. brought up the fact that library initialization is
> >>> impossible to do in a thread safe manner.  Query_thread, for
> >>> example, may not be called from the non-main thread in
> >>> MPI_THREAD_FUNNELED (or by two threads simultaneously in
> MPI_THREAD_SERIALIZED).
> >>>  * The tools working group has some use cases where the Intialized /
> >>> Init race condition is problematic
> >>>  * Fab would like us to revive the generalized request discussion;
> >>> it's a feature that lacks a significant amount of usability without
> >>> MPI_THREAD_MULTIPLE, but MPI_THREAD_MULTIPLE's support is slow
> in
> >>> expanding.
> >>>  * Bill brought up the concern that the forum has the tendency to be
> >>> two-faced about threads.  We talk about "just use a thread" when
> >>> trying to solve a particular problem, then are reluctant to require
> >>> threads as part of the model; we should figure out how to deal with that.
> >>>
> >>> Brian
> >>>
> >>> --
> >>>  Brian W. Barrett
> >>>  Scalable System Software Group
> >>>  Sandia National Laboratories
> >>>
> >>>
> >>>
> >>>
> >>>
> >>> _______________________________________________
> >>> Mpi3-hybridpm mailing list
> >>> Mpi3-hybridpm at lists.mpi-forum.org
> >>> http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi3-hybridpm
> >>
> >>
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> >
> >
> >
> > --
> > Jeff Hammond
> > Argonne Leadership Computing Facility
> > University of Chicago Computation Institute jhammond at alcf.anl.gov /
> > (630) 252-5381 http://www.linkedin.com/in/jeffhammond
> > https://wiki.alcf.anl.gov/parts/index.php/User:Jhammond
> 
> 
> 
> --
> Jeff Hammond
> Argonne Leadership Computing Facility
> University of Chicago Computation Institute
> jhammond at alcf.anl.gov / (630) 252-5381
> http://www.linkedin.com/in/jeffhammond
> https://wiki.alcf.anl.gov/parts/index.php/User:Jhammond
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