Q2.4: FFT Software

Comprehensive list of FFT software: Links to over 65 different pieces of one-dimensional FFT code.
http://tjev.tel.etf.hr/josip/DSP/fft.html
FFT Software including optimised fft routines and mixed-radix algorithms: ftp://usc.edu/pub/C-numanal/fft-stuff.tar.gz
OR, ftp://svr-ftp.eng.cam.ac.uk/pub/comp.speech/analysis/fft-stuff.tar.gz
mixfft03.zip: C-source for a very fast arbitrary N FFT routine: The C-source is ShareWare: read the text file included in the package before using the FFT routine commercially.
Jens J. Nielsen: jnielsen@internet.dk
Available from ftp://svr-ftp.eng.cam.ac.uk/pub/comp.speech/analysis/mixfft03.zip
OR ftp://ftp.coast.net/simtel/msdos/c/mixfft03.zip
FFTW: FFTW is a C subroutine library for computing the FFT in one or more dimensions. It is not limited to sizes that are powers of two, and includes real-complex and parallel transforms.
Also on the FFTW web site are benchmarks comparing the performance and accuracy of many public-domain FFT implementations on a variety of platforms, as well as links to other sources of FFT code and information.
Available from http://theory.lcs.mit.edu/~fftw
Developed by Matteo Frigo and Steven G. Johnson: fftw@theory.lcs.mit.edu