[Mpi-forum] MPI attribute callback behavior

[Jeff Squyres]

...so are you saying that you think it's valid or invalid to call MPI_COMM_FREE in the callbacks in this case?

What do you think about the rest of the items in the list?


On Apr 25, 2011, at 12:01 PM, Bronis R. de Supinski wrote:

> 
> 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/
>> 
>> 


-- 
Jeff Squyres
jsquyres at cisco.com
For corporate legal information go to:
http://www.cisco.com/web/about/doing_business/legal/cri/