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math.transforms.fft: bit simpler, faster.

db4
John Benediktsson 2012-08-09 12:34:02 -07:00
parent d6aa829a06
commit 79ee220d6c
1 changed files with 6 additions and 6 deletions
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12
extra/math/transforms/fft/fft.factor
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@ -9,9 +9,9 @@ IN: math.transforms.fft
! Discrete Fourier Transform ! Discrete Fourier Transform
:: (slow-fft) ( seq inverse? -- seq' ) :: (slow-fft) ( seq inverse? -- seq' )
seq length :> N seq length :> N
inverse? 1 -1 ? 2pi * i* N / :> O inverse? 1 -1 ? 2pi * i* N / N iota n*v :> omega
N iota [| k | N iota [| k |
0 seq [ O k * * e^ * + ] each-index 0 seq omega [ k * e^ * + ] 2each
inverse? [ N / ] when inverse? [ N / ] when
] map ; inline ] map ; inline
@ -19,12 +19,12 @@ IN: math.transforms.fft
:: (fft) ( seq inverse? -- seq' ) :: (fft) ( seq inverse? -- seq' )
seq length :> N seq length :> N
N 1 = [ seq ] [ N 1 = [ seq ] [
inverse? 1 -1 ? 2pi * i* N / :> O
N 2/ :> M
seq even-indices inverse? (fft) seq even-indices inverse? (fft)
seq odd-indices inverse? (fft) seq odd-indices inverse? (fft)
[ [ O * e^ * + inverse? [ 2 / ] when ] 2map-index ] inverse? 1 -1 ? 2pi * i* N /
[ [ O * e^ * - inverse? [ 2 / ] when ] 2map-index ] [ * e^ * ] curry map-index!
[ [ + inverse? [ 2 / ] when ] 2map ]
[ [ - inverse? [ 2 / ] when ] 2map ]
2bi append 2bi append
] if ; inline recursive ] if ; inline recursive