[Mpi-forum] MPI attribute callback behavior

[Jeff Squyres]

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/