FFTPACK

FFTPACK is a package of Fortran-77 subroutines for the Fast Fourier Transform of periodic and other symmetric sequences developed by Paul N. Swarztrauber from the National Center for Atmospheric Research in Boulder, Colorado. The project was sponsored by the National Science Foundation.

The subroutines are transferrable by WWW and FTP from the Netlib site:

http://www.netlib.org/

There are 12 subroutines in the package, plus 7 auxiliary subroutines, which serve to initialize other subroutines, 19 subroutines in total. The essential subroutines are as follows:

rfftf

forward transform of a real periodic sequence

rfftb

backward transform of a real coefficient array

ezfftf

a simplified real periodic forward transform

ezfftb

a simplified real periodic backward transform

sint

sine transform of a real odd sequence

cost

cosine transform of a real even sequence

sinqf

forward sine transform with odd wave numbers

sinqb

unnormalized inverse of sinqf

cosqf

forward cosine transform with odd wave numbers

cosqb

unnormalized inverse of cosqf

cfftf

forward transform of a complex periodic sequence

cfftb

unnormalized inverse of cfftf

See, e.g.,

http://beige.ucs.indiana.edu/FFTPACK/doc

for more information about those routines.