[Mpi-forum] MPI attribute callback behavior

[Bronis R. de Supinski]

Hmm. You still modify A and B but I guess the mods
are not visible by that logic.

On Mon, 25 Apr 2011, Jeff Squyres wrote:

> Probably.
>
> But here's the kicker: MPI_COMM_FREE only *marks* a communicator for freeing; it doesn't necessarily actually free it.
>
> That's my only pause in thinking that it *could* be valid to call MPI_COMM_FREE on a communicator in an attribute callback related to that communicator.
>
> (ditto for TYPE_FREE and WIN_FREE)
>
>
> On Apr 25, 2011, at 11:53 AM, Bronis R. de Supinski wrote:
>
>>
>> Jeff:
>>
>> Maybe I am not following. Wouldn't it be illegal based
>> on your original reasoning for B (it is still being
>> created so the delete is non-deterministic) and for A
>> (seems like a bad idea to modify, i.e., delete, what
>> you are in the middle of copying).
>>
>> Bronis
>>
>>
>> On Mon, 25 Apr 2011, Jeff Squyres wrote:
>>
>>> Here's a followup question: is it valid to call MPI_COMM_FREE on objects A or B when in a keyval copy callback with original object A and new object B?
>>>
>>> I can't decide whether the answer should be "yes" or "no"...
>>>
>>>
>>> On Apr 14, 2011, at 10:36 AM, Jeff Squyres wrote:
>>>
>>>> An issue recently came up within Open MPI as to what exactly you are allowed to do within an attribute callback (e.g., when a communicator is copied or deleted).
>>>>
>>>> From a standards point of view (i.e., regardless of implementation), here's a list that we came up with:
>>>>
>>>> 1. While in a keyval copy callback with original object A and new object B:
>>>> - Call MPI_Comm_get_attr on A: ok
>>>> - Call MPI_Comm_get_attr on B: erroneous
>>>>  (B is still being created, and therefore the get is non-deterministic)
>>>> - Call MPI_Comm_set_attr on A: erroneous
>>>>  (seems like a bad idea to modify what you're in the middle of copying)
>>>> - Call MPI_Comm_set_attr on B: erroneous (non-deterministive) if keyval exists on A, otherwise ok
>>>> - Call MPI_Comm_delete_attr on A: erroneous
>>>>  (seems like a bad idea to modify what you're in the middle of copying)
>>>> - Call MPI_Comm_delete_attr on B: erroneous (non-deterministic)
>>>>  (same as get_attr on B, above)
>>>> - Call MPI_Comm_create_keyval: ok
>>>> - Call MPI_Comm_free_keyval: ok
>>>>
>>>> 2. While in a keyval delete callback on object A:
>>>> - Call MPI_Comm_get_attr on A: erroneous
>>>>  (A is being deleted; that attribute may have already been deleted)
>>>> - Call MPI_Comm_set_attr on A: erroneous
>>>>  (why allow setting on an object that is being deleted?)
>>>> - Call MPI_Comm_delete_attr on A: erroneous
>>>>  (it's going to be deleted anyway)
>>>> - Call MPI_Comm_create_keyval: ok
>>>> - Call MPI_Comm_delete_keyval: ok
>>>>
>>>> Does anyone disagree with this list?
>>>>
>>>> Should we put some kind of list like this in MPI-3?  (I can work up a ticket if we think supporting text like this should be there)
>>>>
>>>> --
>>>> Jeff Squyres
>>>> jsquyres at cisco.com
>>>> For corporate legal information go to:
>>>> http://www.cisco.com/web/about/doing_business/legal/cri/
>>>>
>>>
>>>
>>> --
>>> Jeff Squyres
>>> jsquyres at cisco.com
>>> For corporate legal information go to:
>>> http://www.cisco.com/web/about/doing_business/legal/cri/
>>>
>>>
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>
>
> -- 
> Jeff Squyres
> jsquyres at cisco.com
> For corporate legal information go to:
> http://www.cisco.com/web/about/doing_business/legal/cri/
>
>