[mpiwg-hybridpm] Endpoints

[Jim Dinan]

Eek, ok..  I guess there are a few options.  We could restrict what you can
do in a callback, but that would break backward compatibility.  We could
add a caveat that MPI_Comm_free needs to be called concurrently on all
ranks if there are any attribute callbacks that might want to use a
collective.  Worst case, we could remove the concurrency exception for
MPI_Comm_free on an endpoints communicator.

 ~Jim.


On Thu, Mar 6, 2014 at 10:59 AM, Jeff Squyres (jsquyres) <jsquyres at cisco.com
> wrote:

> There are (currently) no restrictions on what can happen in attribute
> callback functions.
>
> See Fab's presentation from several months ago (I don't remember when,
> exactly, but the meeting was in San Jose/Cisco) about all the problems w/
> attributes -- this is one of them (unrestricted access in callback
> functions).
>
>
>
> On Mar 6, 2014, at 7:51 AM, "Balaji, Pavan" <balaji at anl.gov> wrote:
>
> >
> > I'm pretty sure that's not correct.  You can have large collective ops
> and other operations in the callbacks.  HDF5 and PETSc do all sorts of
> stuff in these callbacks.
> >
> >  -- Pavan
> >
> > On Mar 6, 2014, at 9:39 AM, Jim Dinan <james.dinan at gmail.com> wrote:
> >
> >> I believe that the copy and free attribute callbacks are intended to be
> local functions that deal with objects the user has attached as attributes,
> that might need to be copied or freed.  Can't find text that confirms this
> explicitly, though..
> >>
> >>
> >> On Wed, Mar 5, 2014 at 6:31 PM, Balaji, Pavan <balaji at anl.gov> wrote:
> >>
> >> The endpoints proposal says that Comm_free is not fully synchronizing.
>  What happens if I have an attribute callback on that communicator which
> does a Bcast?  How will that work?
> >>
> >>  -- Pavan
> >>
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> --
> Jeff Squyres
> jsquyres at cisco.com
> For corporate legal information go to:
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