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Re: Help, no improvement in FFT speed on a multiprocessor system [message #67901 is a reply to message #67898]

Mon, 07 September 2009 06:40

Kenneth P. Bowman
Messages: 585
Registered: May 2000

Senior Member

In article <4aa34391$1@darkstar>, "Marco" <null@null.net> wrote:

> I'm running IDL 7.1 on a Linux 2.6. This is an HP quad processor with each
> processors having 6 cores for 24 cores total.
>
> Doing large 2-D FFTs (>8Kx8K) I get no benefit from the extra processors.
> I can vary the number used in IDL from 24 down to 1, and see that the
> number actually of processors actually showing a load is the correct number,
> but from 4 to 24 threads, the speed is the same and no faster than Matlab,
> which uses only a single processor out of the 24.
>
> I've tried varied IDL_CPU_TPOOL_NTHREADS and IDL_CPU_TPOOL_MIN_ELTS, but
> have not been able to improve the results.
>
> Any suggestions?
>
> Thanks in advance,

Do your array dimensions have small prime factors (2, 3, 4, or 5)?

Ken Bowman

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		Re: Help, no improvement in FFT speed on a multiprocessor system By: Kenneth P. Bowman on Mon, 07 September 2009 14:30
		Re: Help, no improvement in FFT speed on a multiprocessor system By: Marco on Mon, 07 September 2009 12:58
		Re: Help, no improvement in FFT speed on a multiprocessor system By: Kenneth P. Bowman on Mon, 07 September 2009 06:40

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