"Jeff Squyres (jsquyres)" <jsquy...@cisco.com> writes: > This is, unfortunately, an undefined area of the MPI specification. I > do believe that our previous behavior was *correct* -- it just > deadlocks with PETSC because PETSC is relying on undefined behavior.
Jeff, can you clarify where in the standard this is left undefined? Is one to assume that callbacks can never call into MPI unless explicitly allowed? Note that empirically, this usage has worked with all implementations since 1998, except this version of Open MPI. If the callback is to be considered invalid, how would you recommend implementing two-way linked communicators? > For those who care, Microsoft/Cisco proposed a new attribute system to > the Forum a while ago that removes all these kinds of ambiguities (see > http://meetings.mpi-forum.org/secretary/2013/09/slides/jsquyres-attributes-revamp.pdf). > However, we didn't get a huge amount of interest, and therefore lost > our window of availability opportunity to be able to advance the > proposal. I'd be more than happy to talk anyone through the proposal > if they have interest/cycles in taking it over and advancing it with > the Forum. > > Two additional points from the PDF listed above: > > - on slide 21, it was decided to no allow the recursive behavior (i.e., you > can ignore the "This is under debate" bullet. > - the "destroy" callback was not judged to be useful; you can ignore slides > 22 and 23.
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