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From: Tim Prins (tprins_at_[hidden])
Date: 2007-08-16 11:53:35


2 process was plenty. Like I said, when running in debug mode, it tends
to 'work' since memory is initialized to \0 and we fall through. In an
optimized build, looking at the mtt results it looks like it segfaults
about 10% of the time.

But if you apply the patch I sent, it will tell you when an invaild
lookup happens, which should be every time it runs.


Mohamad Chaarawi wrote:
> Hey Tim,
> I understand what you are talking about.
> Im trying to reproduce the problem. How many processes are your running
> with, because with the default (4 for the group) it's passing..
> Thanks,
> Mohamad
> On Thu, August 16, 2007 7:49 am, Tim Prins wrote:
>> Sorry, I pushed the wrong button and sent this before it was ready....
>> Tim Prins wrote:
>>> Hi folks,
>>> I am running into a problem with the ibm test 'group'. I will try to
>>> explain what I think is going on, but I do not really understand the
>>> group code so please forgive me if it is wrong...
>>> The test creates a group based on MPI_COMM_WORLD (group1), and a group
>>> that has half the procs in group1 (newgroup). Next, all the processes
>>> do:
>>> MPI_Group_intersection(newgroup,group1,&group2)
>>> ompi_group_intersection figures out what procs are needed for group2,
>>> then calls
>>> ompi_group_incl, passing 'newgroup' and '&group2'
>>> This then calls (since I am not using sparse groups)
>>> ompi_group_incl_plist
>>> However, ompi_group_plist assumes that the current process is a member
>>> of the passed group ('newgroup'). Thus when it calls
>>> ompi_group_peer_lookup on 'newgroup', half of the processes get garbage
>>> back since they are not in 'newgroup'. In most cases, memory is
>>> initialized to \0 and things fall through, but we get intermittent
>>> segfaults in optimized builds.
>> Here is a patch to a error check which highlights the problem:
>> Index: group/group.h
>> ===================================================================
>> --- group/group.h (revision 15869)
>> +++ group/group.h (working copy)
>> @@ -308,7 +308,7 @@
>> static inline struct ompi_proc_t* ompi_group_peer_lookup(ompi_group_t
>> *group, int peer_id)
>> {
>> - if (peer_id >= group->grp_proc_count) {
>> + if (peer_id >= group->grp_proc_count || peer_id < 0) {
>> opal_output(0, "ompi_group_lookup_peer: invalid peer index
>> (%d)", peer_id);
>>> Thanks,
>>> Tim
>>> _______________________________________________
>>> devel mailing list
>>> devel_at_[hidden]
>> _______________________________________________
>> devel mailing list
>> devel_at_[hidden]