Fortran 90 codes for Fast Fourier Transforms and Discrete Weighted Transforms, for use in number theory research.

Code and links in Fortran and C for the Fast Fourier Transform.

By David O'Halloran. The Welchel phase-rotation FFT is a new form of the fast Fourier transform (FFT) that replaces data movement at runtime with equivalent multiplications by precomputed constants. The result is an FFT that is easy to pipeline.

OFFT, "Outrageously Fast Fortran Transpose", and BFFFT, "Blazingly Fast FFT, 2-Dimensional Vectorized Fast Fourier Transform" written in Fortran 90.

Source code of a subroutine to transform (forward or inverse) a one-dimensional complex array in place.