On 25 September 2014 20:50, Nathan Hjelm <hje...@lanl.gov> wrote:
> On Tue, Aug 26, 2014 at 07:03:24PM +0300, Lisandro Dalcin wrote:
>> I finally managed to track down some issues in mpi4py's test suite
>> using Open MPI 1.8+. The code below should be enough to reproduce the
>> problem. Run it under valgrind to make sense of my following
>> diagnostics.
>>
>> In this code I'm creating a 2D, periodic Cartesian topology out of
>> COMM_SELF. In this case, the process in COMM_SELF has 4 logical in/out
>> links to itself. So we have size=1 but indegree=outdegree=4. However,
>> in ompi/mca/coll/basic/coll_basic_module.c, "size * 2" request are
>> being allocated to manage communication:
>>
>> if (OMPI_COMM_IS_INTER(comm)) {
>> size = ompi_comm_remote_size(comm);
>> } else {
>> size = ompi_comm_size(comm);
>> }
>> basic_module->mccb_num_reqs = size * 2;
>> basic_module->mccb_reqs = (ompi_request_t**)
>> malloc(sizeof(ompi_request_t *) * basic_module->mccb_num_reqs);
>>
>> I guess you have to also special-case for topologies and allocate
>> indegree+outdegree requests (not sure about this number, just
>> guessing).
>>
>
> I wish this was possible but the topology information is not available
> at that point. We may be able to change that but I don't see the work
> completing anytime soon. I committed an alternative fix as r32796 and
> CMR'd it to 1.8.3. I can confirm that the attached reproducer no longer
> produces a SEGV. Let me know if you run into any more issues.
>
Did your fix get in for 1.8.3? I'm still getting the segfault.
--
Lisandro Dalcin
============
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