[Mpi3-tools] Tools WG webex: tomorrow!

Marc-Andre Hermanns m.a.hermanns at grs-sim.de
Mon Jul 1 13:36:42 CDT 2013

Dave, all,

> ----8<----
>> 	• Jeff also brings up the idea of a callback (or some kind of MPI_T notification) to know when an MPI object is destroyed (per email conversation w/ Jeff, Kathryn, Martin).
>> 		• Marc-Andre will think about whether it will be useful for any tools to know when MPI objects get destroyed.
>> 		• Marc-Andre will also think about whether it would be useful for there to be an MPI_T mechanism to get some kind of unique ID for an MPI object (that will be durable after the handle is freed). This way, a tool can track the entire lifecycle of an object -- not just its handle.
> ----8<----
> I was unable to attend the call, but why isn't attaching an attribute
> with a destructor callback to the object in question sufficient?  Is
> it because we have MPI opaque objects which do not support attributes
> (e.g., MPI_Op)?

The fact that not all handles support attributes is afaik also part of 
Jeff's and Fab's proposal, but the specific question here is where there 
is a use-case for a tool knowing the difference between calling free and 
the actual destruction of the object.

In other words: If we design a new attributes interface that supports 
_all_ handles, should this also include a callback for destruction, or 
is the callback on free sufficient.

Marc-Andre Hermanns
German Research School for
Simulation Sciences GmbH
c/o Laboratory for Parallel Programming
52062 Aachen | Germany

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