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Re: 2D FFT Slow. Any ideas? [message #37234]

Mon, 08 December 2003 00:02

Brian
Messages: 27
Registered: March 2001

Junior Member

Hi,

The IDL code is

A=dcomplex(randomn(seed,2048, 2048,/DOUBLE), randomn(seed,2048,
2048,/DOUBLE))
t=systime(1)
FA=fft(A,-1)
print, systime(1)-t

The corresponding matlab code is

A = randn(2048,2048) + i*randn(2048,2048);
tic; FA=fft2(A); toc

I get around 10.4 sec in IDL, and around 3.7 sec in MATLAB 6.5

-brian

"R.G. Stockwell" <noemail@please.com> schrieb im Newsbeitrag
news:gN3Ab.767$o_.32178@news.uswest.net...
> "Brian" <brian.huether@NOdlrSPAM.de> wrote in message
> news:a298a85e9af4e70d51199dcae50c4c81@news.teranews.com...
>> I did a little benchmark between IDL and MATLAB. In each case I created
a
>> random double precision complex array of size 2048 by 2048 and timed how
>> long the 2D FFT took. In MATLAB 6.5 it took about 3.5 sec, and in IDL,
it
>> took about 10 sec. Is there a way to have IDL use MATLAB for the FFT,
>> perhaps using activex? Or would the overhead in using activex defeat the
>> purpose?
>>
>> thanks,
>>
>> brian
>>
>>
>
> You could try calling an external routine, some of the best being
available
> at (fastest ft in the west)
>
> http://fftw.org/
>
> Cheers,
> bob
>
> PS I can't believe active x calls would improve speed, but hey, you never
> know.
> And, I'm surprised that the canned IDL is not very fast. Any chance you
> don't really
> have a 2048^2 array in idl (did you make a 2049^2 array for instance?)
>
> If you post a blip of example code, I can run them here (matlab and idl)
and
> verify the time difference,
> which would be very interesting.
>
>

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[Message index]

		Re: 2D FFT Slow. Any ideas? By: Brian on Mon, 08 December 2003 00:02
		Re: 2D FFT Slow. Any ideas? By: R.G. Stockwell on Fri, 05 December 2003 13:05
		Re: 2D FFT Slow. Any ideas? By: K. Bowman on Fri, 05 December 2003 10:32
		Re: 2D FFT Slow. Any ideas? By: R.G. Stockwell on Fri, 05 December 2003 10:04
		Re: 2D FFT Slow. Any ideas? By: Richard French on Mon, 08 December 2003 12:17

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