FFT
A Common Lisp library to do Fast Fourier Transform on a multi-dimensional array of numbers. See Bordeaux-FFT for a faster implementation for one-dimensional arrays.

This library is by Patrick Stein.

The array can be any number of dimensions, but each dimension must be a power-of-two in size.

Here is a simple example on a two-dimensional input buffer.

(require :asdf)
(asdf:operate 'asdf:load-op 'fft)

(defparameter *buf* #2A((1 2 3 4)(5 6 7 8)))

(let ((transformed (fft:fft *buf*)))
    (fft:ifft transformed))

Here is an example using the a parallelized version that uses pcall which, in turn, uses Bordeaux-Threads:

(require :asdf)
(asdf:operate 'asdf:load-op 'pfft)

(defparameter *buf* #2A((1 2 3 4)(5 6 7 8)))

(let ((transformed (pfft:pfft *buf*)))
    (pfft:pifft transformed))

For a more complete description, see the home page.


Mathematics