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Subject: Re: [OMPI users] Hybrid program
From: Ralph Castain (rhc_at_[hidden])
Date: 2008-11-18 13:39:02


I am afraid it is only available in 1.3 - we didn't backport it to the
1.2 series

On Nov 18, 2008, at 10:06 AM, Gabriele Fatigati wrote:

> Hi,
> how can i set "slot mapping" as you told me? With TASK GEOMETRY? Or is
> a new 1.3 OpenMPI feature?
>
> Thanks.
>
> 2008/11/18 Ralph Castain <rhc_at_[hidden]>:
>> Unfortunately, paffinity doesn't know anything about assigning
>> threads to
>> cores. This is actually a behavior of Linux, which only allows
>> paffinity to
>> be set at the process level. So, when you set paffinity on a
>> process, you
>> bind all threads of that process to the specified core(s). You cannot
>> specify that a thread be given a specific core.
>>
>> In this case, your two threads/process are sharing the same core
>> and thus
>> contending for it. As you'd expect in that situation, one thread
>> gets the
>> vast majority of the attention, while the other thread is mostly
>> idle.
>>
>> If you can upgrade to the beta 1.3 release, try using the slot
>> mapping to
>> assign multiple cores to each process. This will ensure that the
>> threads for
>> that process have exclusive access to those cores, but will not
>> bind a
>> particular thread to one core - the threads can "move around"
>> across the
>> specified set of cores. Your threads will then be able to run without
>> interfering with each other.
>>
>> Ralph
>>
>>
>> On Nov 18, 2008, at 9:18 AM, Gabriele Fatigati wrote:
>>
>>> Dear OpenMPI developers,
>>> i have a strange problem with mixed program MPI+OPENMP over OpenMPI
>>> 1.2.6. I'm using PJL TASK GEOMETRY in LSF Scheduler, setting 2 MPI
>>> process every compute node, and 2 OMP threads per process. Using
>>> paffinity and maffinity, i've noted that over every node, i have 2
>>> thread that works 100%, and 2 threads doesn't works, or works very
>>> few.
>>>
>>> If i disable paffinity and maffinity, 4 threads works well, without
>>> load imbalance.
>>> I don't understand this issue: paffinity and maffinity should map
>>> every thread over a specific core, optimizing the cache flow, but i
>>> have this without settings there!
>>>
>>> Can i use paffinity and maffinity in mixed MPI+OpenMP program? Or it
>>> works only over MPI thread?
>>>
>>> Thanks in advance.
>>>
>>>
>>> --
>>> Ing. Gabriele Fatigati
>>>
>>> CINECA Systems & Tecnologies Department
>>>
>>> Supercomputing Group
>>>
>>> Via Magnanelli 6/3, Casalecchio di Reno (BO) Italy
>>>
>>> www.cineca.it Tel: +39 051 6171722
>>>
>>> g.fatigati_at_[hidden]
>>> _______________________________________________
>>> users mailing list
>>> users_at_[hidden]
>>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>>
>> _______________________________________________
>> users mailing list
>> users_at_[hidden]
>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>>
>>
>
>
>
> --
> Ing. Gabriele Fatigati
>
> CINECA Systems & Tecnologies Department
>
> Supercomputing Group
>
> Via Magnanelli 6/3, Casalecchio di Reno (BO) Italy
>
> www.cineca.it Tel: +39 051 6171722
>
> g.fatigati_at_[hidden]
> _______________________________________________
> users mailing list
> users_at_[hidden]
> http://www.open-mpi.org/mailman/listinfo.cgi/users