[Mpi-forum] MPI attribute callback behavior

[Jeff Squyres]

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/