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CUDA-x86.

PGI FORTRAN OpenMP: poor performance in a big loop???
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mkcolg



Joined: 30 Jun 2004
Posts: 6122
Location: The Portland Group Inc.

PostPosted: Tue Jun 12, 2012 12:38 pm    Post subject: Reply with quote

Hi Nick,

Quote:
Therefore, the sequential computing with "-O3 -fast" is better choice compared to parallel computing?
No, you can't conclude this for a general case. I think a more likely scenario here is that the compiler is optimizing away the calculations (the value of A is never used, hence it can be removed). The only thing you're measuring here is the OpenMP overhead.

For OpenMP performance, I'd recommend looking at some benchmarks such as NAS Parallel Benchmarks or the SPEC OMP2001 suite.

- Mat
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Nick Kong



Joined: 08 Jun 2012
Posts: 11

PostPosted: Tue Jun 12, 2012 1:59 pm    Post subject: Reply with quote

Dear Mat,

Thank you for your quick response!

It seems that, for some coding structures, "-O3 -fast" can optimize the "sequential computing" with better performance compared to "parallel computing", but this is not general case. I will keep eye on this if there are more cases of this kind.

Thank you again for your help.
Nick
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Flin



Joined: 25 Jun 2012
Posts: 1

PostPosted: Mon Jun 25, 2012 1:00 am    Post subject: Reply with quote

Have you tried it with Schedule(Static)?
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