From help-request at octave dot org Fri Dec 17 11:08:04 2004
Subject: fft source [was "Very important"]
From: Geraint Paul Bevan <g dot bevan at eng dot gla dot ac dot uk>
To: eman mohamed <eman_hofney at yahoo dot com>
CC: octave help mailing list <help at octave dot org>
Date: Fri, 17 Dec 2004 16:58:28 +0000

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eman mohamed wrote:
| Hi ;
|
| Can you please tell me where i can find the fft.m , i need the source
| code for fft soon please , as it is very important to me .
|
| If you have the source code please send it to me .
|
| Thanks alot for your help in advance .
|


Firstly, you should probably use more specific titles when posting to
mailing lists. "Very important" looks like a virus-laden or spam message.

Secondly, all of the sources to Octave are available from the download
page at www.octave.org.


If you type "which fft" at the Octave prompt, you will see that fft is a
builtin function. It is not implemented as an m-file.

There are numerous Octave files which have some part to play in the
implementation of FFT:

$ find /usr/local/src/octave/octave -name "*fft*"
/usr/local/src/octave/octave/libcruft/fftpack
/usr/local/src/octave/octave/libcruft/fftpack/cfftb.f
/usr/local/src/octave/octave/libcruft/fftpack/cfftb1.f
/usr/local/src/octave/octave/libcruft/fftpack/cfftf.f
/usr/local/src/octave/octave/libcruft/fftpack/cfftf1.f
/usr/local/src/octave/octave/libcruft/fftpack/cffti.f
/usr/local/src/octave/octave/libcruft/fftpack/cffti1.f
/usr/local/src/octave/octave/libcruft/fftpack/fftpack.doc
/usr/local/src/octave/octave/liboctave/oct-fftw.cc
/usr/local/src/octave/octave/liboctave/oct-fftw.h
/usr/local/src/octave/octave/scripts/signal/fftconv.m
/usr/local/src/octave/octave/scripts/signal/fftfilt.m
/usr/local/src/octave/octave/scripts/signal/fftshift.m
/usr/local/src/octave/octave/src/DLD-FUNCTIONS/fft.cc
/usr/local/src/octave/octave/src/DLD-FUNCTIONS/fft2.cc
/usr/local/src/octave/octave/src/DLD-FUNCTIONS/fftn.cc
/usr/local/src/octave/octave/src/DLD-FUNCTIONS/fftw_wisdom.cc
/usr/local/src/octave/octave/test/octave.test/signal/fft-1.m
/usr/local/src/octave/octave/test/octave.test/signal/fft2-1.m
/usr/local/src/octave/octave/test/octave.test/signal/ifft-1.m
/usr/local/src/octave/octave/test/octave.test/signal/ifft2-1.m

All of these files can be obtained in a tarball of via CVS. See
http://www.octave.org/download

If you look at fft.cc, you will see that a call to the fourier()
function in the NDArray code occurs,

try:
$ find /usr/local/src/octave/octave -name "*NDArray*"

However, the actual FFT itself is performed using standard libraries. If
you have the FFTW3 library installed on your system, Octave will use
that. If not, it will use FFTPACK (the code to which is contained in the
octave/libcruft directory).

- --
Geraint Bevan
http://www.mech.gla.ac.uk/~gbevan

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