So I started out by looking at FFTW, but (a) calling C is enough of a mess that I prefer not to,
Mon, 20 May 2002 01:49:48 +0000
So I started out by looking at FFTW, but (a) calling C is enough of a mess that I prefer not to, (b) it wants doubles as input, not the shorts that I actually have, (c) I wanted to find out how an FFT works anyway. Lots of web trawling later I game up on most of the other FFT code snippets I could find, downloaded the appropriate Numerical Recipes ("In C" variant) chapter, and transcribed their C into Lisp. With a few type declarations it does a forward-then-reverse in-place transform in about 1.4ms.
Then I actually did try FFTW, and it's slower (2.2 seconds for the forward transforms alone). Could be C calling overhead, or my lousy measurements, or possibly that 2^10 is neither a very big nor complicated size anyway and I would have found it more of a win if I had some weirdo 31765 byte buffer, or something.
And earlier today I saw When Clones Go Bad. Trouble was, having re-read a lot of Jon Courtenay Grimwood books recently (he throws neuroscience terms around like confetti - or like confetti would be if it were heavier, slightly squishy, oxygen-dependent, full of chemicals and - and actually not very much like confetti at all, then) is that I kept hearing Princess Amidala's name as Amygdala