FFTW Library at SCS

Description

FFTW (The Fastest Fourier Transform in the West) is a C subroutine library for computing the discrete Fourier transform (DFT) in one or more dimensions, of arbitrary input size, and of both real and complex data (as well as of even/odd data, i.e. the discrete cosine/sine transforms or DCT/DST). We believe that FFTW, which is free software, should become the FFT library of choice for most applications.

Note that there are two main versions of FFTW, version 2 and version 3 which are not compatible.

General Use

The basic usage of FFTW to compute a one-dimensional DFT of size N is simple, and it typically looks something like this code:

     #include <fftw3.h>
     ...
     {
         fftw_complex *in, *out;
         fftw_plan p;
         ...
         in = (fftw_complex*) fftw_malloc(sizeof(fftw_complex) * N);
         out = (fftw_complex*) fftw_malloc(sizeof(fftw_complex) * N);
         p = fftw_plan_dft_1d(N, in, out, FFTW_FORWARD, FFTW_ESTIMATE);
         ...
         fftw_execute(p); /* repeat as needed */
         ...
         fftw_destroy_plan(p);
         fftw_free(in); fftw_free(out);
     }

To link this code, you simply add -lfftw3 and -lm to your linker options. Other examples can be found at the FFTW tutorial pages.

Cluster Specific Use

Phoenix

• The fftw version 2 and version 3 are both installed as part of the OS install. The libraries are:
  • /usr/lib/libfftw.a -- version 2
  • /usr/lib/libfftw3.a -- version 3
  • shared objects are also available.
  • An fftw3 version compiled with single precision is available on: /usr/local/lib/fftw3/lib
• All versions are compiled with gcc.

Prism

• Only ffftw version 3 is installed on Prism. The libraries are:
  • /usr/lib64/libfftw3_threads.so.3.1.1
  • /usr/lib64/libfftw3_threads.so.3
  • /usr/lib64/libfftw3.so.3.1.1
  • /usr/lib64/libfftw3.so.3
• All versions are compiled with gcc.

-- JeffMcDonald - 19 Oct 2006 -- GeoffW - 29 Mar 2007