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Subject: Re: [OMPI users] Hybrid program
From: Gabriele Fatigati (g.fatigati_at_[hidden])
Date: 2008-11-18 14:46:39


Ok,
but in Ompi 1.3 how can i enable it?

2008/11/18 Ralph Castain <rhc_at_[hidden]>:
> 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
>
> _______________________________________________
> 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]