Comments on: Public Domain Fourier Transform Library for Common Lisp http://nklein.com/2009/10/public-domain-fourier-transform-library-for-common-lisp/ software development and consulting Sun, 20 May 2012 18:07:58 +0000 hourly 1 http://wordpress.org/?v=3.3.2 By: pat http://nklein.com/2009/10/public-domain-fourier-transform-library-for-common-lisp/comment-page-1/#comment-373 pat Thu, 08 Oct 2009 14:18:20 +0000 http://nklein.com/?p=941#comment-373 I never got FFTW working on my Mac. I may play with it some more to try to get a better idea of the speed comparison. That said, it looks like I lose terribly to <a href="http://vintage-digital.com/hefner/software/bordeaux-fft/manual.html" rel="nofollow">Bordeaux-FFT</a> though. It only handles one-dimensional arrays, but I should probably look to it for some guidance about how to make this really sing. For a 1,048,576 sample array, my FFT takes 4.92 seconds while the Bordeaux-FFT library takes 0.72 seconds. I never got FFTW working on my Mac. I may play with it some more to try to get a better idea of the speed comparison.

That said, it looks like I lose terribly to Bordeaux-FFT though. It only handles one-dimensional arrays, but I should probably look to it for some guidance about how to make this really sing. For a 1,048,576 sample array, my FFT takes 4.92 seconds while the Bordeaux-FFT library takes 0.72 seconds.

]]> By: pat http://nklein.com/2009/10/public-domain-fourier-transform-library-for-common-lisp/comment-page-1/#comment-369 pat Thu, 08 Oct 2009 12:44:30 +0000 http://nklein.com/?p=941#comment-369 No, I didn't. Another person pointed it out in <a href="http://nklein.com/2009/10/lisp-troubles-fabricating-a-closure/#comments" rel="nofollow">this thread</a>. I don't know how I missed it when I was searching Google for FFT and Lisp because it comes up in the top ten hits. All I found before is FFTW bindings. Also, Bordeaux FFT isn't mentioned on the Cliki, nor is it hosted on common-lisp.net like Bordeaux Threads is. I will get Bordeaux FFT on the Cliki and on my page. Thanks for the heads up. No, I didn’t. Another person pointed it out in this thread. I don’t know how I missed it when I was searching Google for FFT and Lisp because it comes up in the top ten hits. All I found before is FFTW bindings. Also, Bordeaux FFT isn’t mentioned on the Cliki, nor is it hosted on common-lisp.net like Bordeaux Threads is.

I will get Bordeaux FFT on the Cliki and on my page. Thanks for the heads up.

]]> By: stassats http://nklein.com/2009/10/public-domain-fourier-transform-library-for-common-lisp/comment-page-1/#comment-366 stassats Thu, 08 Oct 2009 12:15:45 +0000 http://nklein.com/?p=941#comment-366 Did you know about http://vintage-digital.com/hefner/software/bordeaux-fft/manual.html ? Did you know about http://vintage-digital.com/hefner/software/bordeaux-fft/manual.html ?

]]> By: Leslie P. Polzer http://nklein.com/2009/10/public-domain-fourier-transform-library-for-common-lisp/comment-page-1/#comment-364 Leslie P. Polzer Thu, 08 Oct 2009 07:23:56 +0000 http://nklein.com/?p=941#comment-364 Have you done any benchmarks against FFTW? I'd be interested in the results, even with an unoptimized version of CL-FFT. Have you done any benchmarks against FFTW? I’d be interested in the results, even with an unoptimized version of CL-FFT.

]]> By: pat http://nklein.com/2009/10/public-domain-fourier-transform-library-for-common-lisp/comment-page-1/#comment-361 pat Thu, 08 Oct 2009 03:07:09 +0000 http://nklein.com/?p=941#comment-361 I know all about DCTs. A few jobs ago, I did image-processing with a bent toward "what can we do with JPEG images without inverse DCT-ing them". You're missing a word in your last sentence there though... was that "you'll see that you didn't lose much information anyways" or what? Anyhow... DCTs have much of the same stricture as DFTs did.... they are much happier with axis-aligned modulations that are at a frequency that's a power-of-two divided by the image size. For other things, they really spread around the power more than I was hoping my GA would. I know all about DCTs. A few jobs ago, I did image-processing with a bent toward “what can we do with JPEG images without inverse DCT-ing them”. You’re missing a word in your last sentence there though… was that “you’ll see that you didn’t lose much information anyways” or what?

Anyhow… DCTs have much of the same stricture as DFTs did…. they are much happier with axis-aligned modulations that are at a frequency that’s a power-of-two divided by the image size. For other things, they really spread around the power more than I was hoping my GA would.

]]> By: Reddit sux http://nklein.com/2009/10/public-domain-fourier-transform-library-for-common-lisp/comment-page-1/#comment-360 Reddit sux Thu, 08 Oct 2009 00:03:05 +0000 http://nklein.com/?p=941#comment-360 In typical reddit manner they are wrong. You should've done the DCT. Go look at how jpegs are compressed and you'll see that you didn't much information anyways. In typical reddit manner they are wrong. You should’ve done the DCT.

Go look at how jpegs are compressed and you’ll see that you didn’t much information anyways.

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