On May 27, 2014, at 9:11 PM, Gilles Gouaillardet <gilles.gouaillar...@gmail.com> wrote:
> in the case of intercomm_create, the children free all the communicators and > then MPI_Disconnect() and then MPI_Finalize() and exits. > the parent only MPI_Disconnect() without freeing all the communicators. > MPI_Finalize() tries to disconnect and communicate with already exited > processes. > > my understanding is that there are two ways of seeing things : > a) the "R-way" : the problem is the parent should not try to communicate to > already exited processes > b) the "J-way" : the problem is the children should have waited either in > MPI_Comm_free() or MPI_Finalize() I didn't ignore Ralph's email; I was pointing out what the MPI semantics are supposed to be. I had only a short time this morning to look at the intercomm_create test program, and it looks like Gilles might be correct -- the children are freeing all relevant communicators *but the parent is not*. If this is, indeed, correct, then a) OMPI's implementation might be fine because the test program is erroneous (i.e., the children *think* that they are disconnected and therefore allow themselves to exit, but the parents *think* that they are still connected and therefore try to contact the children during the parents' MPI_FINALIZE), and b) his original patch to the test program could well be correct. I won't have time to investigate this today; if someone else could look at the test code and confirm whether this is correct or not, that would be appreciated. > as far as i am concerned, i have no opinion on which of a) or b) is the > correct/most appropriate approach. To be totally clear: MPI says it is erroneous for only some (not all) processes in a communicator to call MPI_COMM_FREE. So if that's the real problem, then the discussion about why the parent(s) is(are) trying to contact the children is moot -- the test is erroneous, and erroneous application behavior is undefined. All that being said, if we want to make this error case a bit friendlier to the user, that would be great (i.e., a show_help something like "It looks like an MPI process is trying to contact another MPI process that has already exited/called MPI_FINALIZE. This is almost certainly an error in the application..."). But that's definitely extra bonus points, and not required. -- Jeff Squyres jsquy...@cisco.com For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/
