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Subject: Re: [OMPI devel] reduce_scatter bug with hierarch
From: Tim Mattox (timattox_at_[hidden])
Date: 2009-01-13 23:53:45


George, I suggest that you file a CMR for r20267 and we can
go from there. If it makes 1.3 it makes it, otherwise we have
it ready for 1.3.1 At this point the earliest 1.3 will go out is
Wednesday late morning (presuming I'm the one moving
the bits), and is more likely to hit the website in the afternoon.
By morning I'll have odin's MTT results on r20267 on the trunk
using hierarch, and we can see if it fixed the problem.

On Tue, Jan 13, 2009 at 10:28 PM, George Bosilca <bosilca_at_[hidden]> wrote:
> Unfortunately, this pinpoint the fact that we didn't test enough the
> collective module mixing thing. I went over the tuned collective functions
> and changed all instances to use the correct module information. It is now
> on the trunk, revision 20267. Simultaneously,I checked that all other
> collective components do the right thing ... and I have to admit tuned was
> the only faulty one.
>
> This is clearly a bug in the tuned, and correcting it will allow people to
> use the hierarch. In the current incarnation 1.3 will mostly/always segfault
> when hierarch is active. I would prefer not to give a broken toy out there.
> How about pushing r20267 in the 1.3?
>
> george.
>
>
> On Jan 13, 2009, at 20:13 , Jeff Squyres wrote:
>
>> Thanks for digging into this. Can you file a bug? Let's mark it for
>> v1.3.1.
>>
>> I say 1.3.1 instead of 1.3.0 because this *only* affects hierarch, and
>> since hierarch isn't currently selected by default (you must specifically
>> elevate hierarch's priority to get it to run), there's no danger that users
>> will run into this problem in default runs.
>>
>> But clearly the problem needs to be fixed, and therefore we need a bug to
>> track it.
>>
>>
>>
>> On Jan 13, 2009, at 2:09 PM, Edgar Gabriel wrote:
>>
>>> I just debugged the Reduce_scatter bug mentioned previously. The bug is
>>> unfortunately not in hierarch, but in tuned.
>>>
>>> Here is the code snipplet causing the problems:
>>>
>>> int reduce_scatter (...., mca_coll_base_module_t *module)
>>> {
>>> ...
>>> err = comm->c_coll.coll_reduce (...., module)
>>> ...
>>> }
>>>
>>>
>>> but should be
>>> {
>>> ...
>>> err = comm->c_coll.coll_reduce (..., comm->c_coll.coll_reduce_module);
>>> ...
>>> }
>>>
>>> The problem as it is right now is, that when using hierarch, only a
>>> subset of the function are set, e.g. reduce,allreduce, bcast and barrier.
>>> Thus, reduce_scatter is from tuned in most scenarios, and calls the
>>> subsequent functions with the wrong module. Hierarch of course does not like
>>> that :-)
>>>
>>> Anyway, a quick glance through the tuned code reveals a significant
>>> number of instances where this appears(reduce_scatter, allreduce, allgather,
>>> allgatherv). Basic, hierarch and inter seem to do that mostly correctly.
>>>
>>> Thanks
>>> Edgar
>>> --
>>> 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
>>> _______________________________________________
>>> devel mailing list
>>> devel_at_[hidden]
>>> http://www.open-mpi.org/mailman/listinfo.cgi/devel
>>
>>
>> --
>> Jeff Squyres
>> Cisco Systems
>>
>> _______________________________________________
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>> http://www.open-mpi.org/mailman/listinfo.cgi/devel
>
> _______________________________________________
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> devel_at_[hidden]
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>

-- 
Tim Mattox, Ph.D. - http://homepage.mac.com/tmattox/
 tmattox_at_[hidden] || timattox_at_[hidden]
    I'm a bright... http://www.the-brights.net/