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Subject: Re: [OMPI devel] GROUP_EMPTY fixes break intel tests :-(
From: Edgar Gabriel (gabriel_at_[hidden])
Date: 2007-12-06 11:09:46


well, the best I could find is the following in section 5.2.1

"MPI_GROUP_EMPTY, which is a valid handle to an empty group, should not
be confused with MPI_GROUP_NULL, which in turn is an invalid handle. The
former may be used as an argument to group operations; the latter, which
is returned when a group is freed, in not a valid argument. ( End of
advice to users.) "

Jeff Squyres wrote:
> So the changes that we debated and had Edgar put in *do* break some
> intel tests. Doh! :-(
>
> MPI_Group_compare_f
> MPI_Group_intersection2_c
> MPI_Group_intersection2_f
>
> It looks like these tests are specifically calling MPI_GROUP_FREE on
> MPI_GROUP_EMPTY.
>
> I note that there is code in the ompi/group/group_*.c code that
> specifically calls OBJ_RETAIN on ompi_group_empty when we return
> MPI_GROUP_EMPTY. I wonder if this RETAIN was added (and the MPI param
> check removed) in reaction to the intel tests...?
>
> Can someone cite again where we thought the spec said that we should
> not free GROUP_EMPTY? Was is just on the argument that it's a
> predefined handle and therefore should never be freed?
>
> I cannot find any specific text in 1.2 or the errata stating that it's
> bad to free GROUP_EMPTY. I agree that this is somewhat counter to the
> rest of the MPI philosophy of not freeing predefined handles, though.
>

-- 
Edgar Gabriel
Assistant Professor
Parallel Software Technologies Lab      http://pstl.cs.uh.edu
Department of Computer Science          University of Houston
Philip G. Hoffman Hall, Room 524        Houston, TX-77204, USA
Tel: +1 (713) 743-3857                  Fax: +1 (713) 743-3335