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Subject: Re: [OMPI users] segmentation fault
From: Vaz, Guilherme (G.Vaz_at_[hidden])
Date: 2010-12-16 04:20:31


Ok, ok. It is indeed a CFD program, and Gus got it right. Number of cells per core means memory per core (sorry for the inaccuracy).
My PC has 12GB of RAM. And the same calculation runs fine in an old Ubuntu8.04 32bits with 4GB RAM.
What I find strange is that the same problems runs with 1 core (without evoking mpiexec) and then for large number of cores/processes, for instance mpiexec -n 32. Something in between not. And it is not a bug in the program because it runs in other machines and the code has not been changed.

Anymore hints?

Thanks in advance.

Guilherme

dr. ir. Guilherme Vaz
CFD Researcher
Research & Development
E mailto:G.Vaz_at_[hidden]
T +31 317 49 33 25

MARIN
2, Haagsteeg, P.O. Box 28, 6700 AA Wageningen, The Netherlands
T +31 317 49 39 11, F +31 317 49 32 45, I www.marin.nl

-----Original Message-----
From: users-bounces_at_[hidden] [mailto:users-bounces_at_[hidden]] On Behalf Of Gus Correa
Sent: Thursday, December 16, 2010 12:46 AM
To: Open MPI Users
Subject: Re: [OMPI users] segmentation fault

Maybe a CFD jargon?
Perhaps the number (not size) of cells in a mesh/grid being handled
by each core/cpu?

Ralph Castain wrote:
> I have no idea what you mean by "cell sizes per core". Certainly not any
> terminology within OMPI...
>
>
> On Dec 15, 2010, at 3:47 PM, Vaz, Guilherme wrote:
>
>>
>> Dear all,
>>
>> I have a problem with openmpi1.3, ifort+mkl v11.1 in Ubuntu10.04
>> systems (32 or 64bit). My code worked in Ubuntu8.04 and works in
>> RedHat based systems, with slightly different version changes on mkl
>> and ifort. There were no changes in the source code.
>> The problem is that the application works for small cell sizes per
>> core, but not for large cell sizes per core. And it always works for 1
>> core.
>> Example: a grid with 1.2Million cells does not work with mpiexec -n 4
>> <my_app> but it works with mpiexec -n 32 <my_app>. It seems that there
>> is a maximum of cell/core. And it works with <my_app>.
>>
>> Is this a stack size (or any memory problem)? Should I set the ulimit
>> -s unlimited not only on my bashrc but also in the ssh environment
>> (and how)? Or is something else?
>> Any clues/tips?
>>
>> Thanks for any help.
>>
>> Gui
>>
>>
>>
>>
>> <imagec393d1.JPG><image4c4685.JPG>
>>
>> dr. ir. Guilherme Vaz
>>
>> CFD Researcher
>>
>>
>> Research & Development
>>
>>
>>
>>
>>
>> *MARIN*
>>
>>
>>
>>
>>
>> 2, Haagsteeg
>> E G.Vaz_at_[hidden] <mailto:G.Vaz_at_[hidden]> P.O. Box 28 T +31 317 49 39 11
>> 6700 AA Wageningen F +31 317 49 32 45
>> T +31 317 49 33 25 The Netherlands I www.marin.nl <http://www.marin.nl>
>>
>>
>> _______________________________________________
>> users mailing list
>> users_at_[hidden] <mailto:users_at_[hidden]>
>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>
>
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