[Pw_forum] Intel MPI or OpenMPI?

[Nicola Marzari]

Dear Tran,

here are the Q-E tests for CP in a Q6600 :
http://quasiamore.mit.edu/pmwiki/index.php?n=Main.CP90Timings

If you get the same performance, things are running ok.

Always set the system varable OMP_NUM_THREADS to 1, otherwise
perfromance can easily decrease by one order of magnitude, on a 4
core job.

				nicola



Ha, Tran Van wrote:
> Thanks Nicola Marzari  and  Jun Dai for help me about FFTW.
> Dear Pwscf Users, I have a problem with my new quadcore Q6600 (I had no 
> problem with my old parrallel machine).
> I read the messages from our forum, especially 
> http://www.democritos.it/pipermail/pw_forum/2008-February/subject.html#8280
> As *Axel Kohlmeyer* said, we can get a speedup of roughly 2.5x to 3.5x from
> a quad core cpu over a corresponding single core but to me it's very 
> bad! using one core always run faster all 4 cores (the same with gamma 
> point also k-point).
> I used PWscf 4.0.3, Intel compiler 10.1.018 and OpenMPI 1.2.8. I don't 
> know why? Or I can change into using Intel MPI with my Quadcore?
> Thank you in advance for your help.
> 
> 
> Nam, Tran Van
> Hanoi University of Technology
> Faculty of Chemistry
> Department of Physical Chemistry
> 
> 
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Prof Nicola Marzari   Department of Materials Science and Engineering
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