Fast Fourier Transforms
FORTRAN77 Calling Examples

FFTW3 is a directory of FORTRAN77 programs which demonstrate the use of the FFTW3 library, which was written by Matteo Frigo and Steven Johnson.

FFTW3 is a library of C routines which can compute the Fast Fourier transform very efficiently.

FFTW3 can compute the discrete Fourier transform of:

FFTW3 can also compute the discrete Hartley transform of real data.

The length of the data is not required to be a power of 2. Any length of data can be processed.

The data is not restricted to 1 dimensional vectors. FFTW3 can handle data that is 2 or 3 dimensional. In fact, the program can handle data with any dimensionality.

The FORTRAN77 include file is in /usr/local/include. A sample copy is also available in this directory.

Interested users should go to the FFTW home page: http://www.fftw.org/ which contains the current source code, examples, and documentation.


Any program, subroutine or function that calls the FFTW3 functions must include, in its declarations, the statement

        include "fftw3.f"
which will add the appropriate declarations for the FFTW3 functions.

At link time, you must include the compiled FFTW3 library, which is probably a file with the name libfftw3.a. If directory is the directory where this library is stored, then an appropriate command might be

        gfortran myprog.f -Ldirectory -lfftw3


The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.

Non-free licenses may also be purchased from MIT, for users who do not want their programs protected by the GPL.


FFTW3 examples are available in a C version and a FORTRAN77 version and a FORTRAN90 version.

Related Programs:

FFTPACK5, a FORTRAN77 library which contains FFT routines.

GSL, a C++ library which includes a number of FFT routines.

NMS, a FORTRAN90 library which includes a number of FFT routines.

SFTPACK, a FORTRAN77 library which implements the "slow" Fourier transform, intended as a teaching tool and comparison with the fast Fourier transform.

WALSH, a FORTRAN77 library which implements versions of the Walsh and Haar transforms.


Matteo Frigo and Steven Johnson


  1. William Briggs, Van Emden Henson,
    The Discrete Fourier Transform,
    LC: QA403.5 B75
  2. Elbert Brigham,
    The Fast Fourier Transform and Its Applications,
    Prentice-Hall, 1988.
  3. Matteo Frigo, Steven Johnson,
    User Manual for FFTW.

Examples and Tests:

You can go up one level to the FORTRAN77 source codes.

Last revised on 05 January 2006.