[mpiwg-languages] static datatypes lifetimes

[Jeff Hammond]

I think the API you want then is basically UCC.  Prescribe everything for
every operation.

Jeff

On Sun, Apr 27, 2025 at 6:10 PM Skjellum, Anthony <askjellum at tntech.edu>
wrote:

> Another issue: Info arguments are missing on non-blocking and blocking
> collectives.
>
>
> Anthony Skjellum, PhD
> Professor of Computer Science
> Director, Advanced Scalable Computing,
>               Extreme Networks & Data (ASCEND) Center
> Tennessee Technological University
> email: askjellum at tntech.edu
> cell: +1-205-807-4968
>
>
> ------------------------------
> *From:* mpiwg-languages <mpiwg-languages-bounces at lists.mpi-forum.org> on
> behalf of Jeff Hammond via mpiwg-languages <
> mpiwg-languages at lists.mpi-forum.org>
> *Sent:* Saturday, April 26, 2025 11:53 PM
> *To:* mpiwg-languages at lists.mpi-forum.org <
> mpiwg-languages at lists.mpi-forum.org>
> *Cc:* Jeff Hammond <jeff.science at gmail.com>;
> mpiwg-languages at lists.mpi-forum.org <mpiwg-languages at lists.mpi-forum.org>
> *Subject:* Re: [mpiwg-languages] static datatypes lifetimes
>
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> Attributes on ops, datatypes and files is critical for multiple use cases.
> It’s ridiculous we don’t have them. The standard is inconsistent without.
> Jeff Sent from my iPhone On 27. Apr 2025, at 5. 51, Joseph Schuchart via
> mpiwg-languages <mpiwg-languages@ lists. mpi-forum. org>
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> Attributes on ops, datatypes and files is critical for multiple use cases.
> It’s ridiculous we don’t have them. The standard is inconsistent without.
>
> Jeff
>
> Sent from my iPhone
>
> On 27. Apr 2025, at 5.51, Joseph Schuchart via mpiwg-languages <
> mpiwg-languages at lists.mpi-forum.org> wrote:
>
> 
> Unfortunately, there is a catch: MPI_COMM_SELF is only
> relevant/available/valid in the World Process Model (WPM), i. e. , if using
> `MPI_Init`/`MPI_Finalize`. In the Sessions process model, predefined
> communicators are not available. The life-time
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> Unfortunately, there is a catch: MPI_COMM_SELF is only
> relevant/available/valid in the World Process Model (WPM), i.e., if
> using `MPI_Init`/`MPI_Finalize`. In the Sessions process model,
> predefined communicators are not available.
>
> The life-time of datatypes is a known quirk and I think it was
> discovered after Sessions became part of the standard. They are not
> bound to any other MPI object and can survive complete shutdown of all
> sessions / the WPM. IIRC in Open MPI (but have to check), datatypes
> retain a reference on the internal MPI instance and it is the
> application's responsibility to free all MPI objects before shutdown.
> Once the last datatype/session/wpm is gone we release the instance.
>
> I don't like the state of things there and it is problematic. For
> starters, it prevents complete session isolation (and the benefits that
> come with it, such as different threading levels). It's not clear to me
> how that can be rectified and I think the Forum is not clear on that
> either, which is why we ended up with this weird zombie state. If
> someone wants to open a ticket to start a discussion on this I'm happy
> to participate.
>
> For the problem at hand though (as I understand it), maybe it's
> sufficient to add attributes to datatypes? I don't see why that would be
> a problem and if it helps with language adoption we have a good argument
> for it.
>
> Cheers
> Joseph
>
> On 4/25/25 17:24, Alfredo Correa via mpiwg-languages wrote:
> > Hi Sayan, On Fri, Apr 25, 2025 at 2: 03 PM Ghosh, Sayan
> > <sayan. ghosh@ pnnl. gov> wrote: Consider finalize-delete-callback
> > (this is what Alfredo is alluding to perhaps w. r. t
> > datatype-attached-to-environment) – that seems to rely on MPI_COMM_SELF
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> > Hi Sayan,
> >
> > On Fri, Apr 25, 2025 at 2:03 PM Ghosh, Sayan <sayan.ghosh at pnnl.gov> wrote:
> >
> >       * Consider finalize-delete-callback (this is what Alfredo is
> >         alluding to perhaps w.r.t datatype-attached-to-environment) –
> >         that seems to rely on MPI_COMM_SELF callback (freeing
> >         comm-self triggers callback)
> >
> >
> >
> > That is a good point. At first glance, attaching things to
> > MPI_COMM_WORLD or MPI_COMM_SELF would have a similar effect to
> > attaching stuff to the environment.
> > I didn't think about this because I was reluctant to modify (in any
> > way) either of these special communicators, in particular MPI_COMM_WORLD.
> > But MPI_COMM_SELF might still be a good candidate; others can point
> > out if there is a catch.
> >
> > Thanks,
> > Alfredo
> > _
> > _
> >
> >
>
>
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-- 
Jeff Hammond
jeff.science at gmail.com
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