FFTW(3pm)						User Contributed Perl Documentation						 FFTW(3pm)

NAME

       PDL::FFTW - PDL interface to the Fastest Fourier Transform in the West v2.x

DESCRIPTION

       This is a means to interface PDL with the FFTW library. It's similar to the standard FFT routine but it's usually faster and has support
       for real transforms. It works well for the types of PDLs for which was the library was compiled (otherwise it must do conversions).

SYNOPSIS

	   use PDL::FFTW

	   load_wisdom("file_name");

	   out_cplx_pdl =  fftw(in_cplx_pdl);
	   out_cplx_pdl = ifftw(in_cplx_pdl);

	   out_cplx_pdl =  rfftw(in_real_pdl);
	   out_real_pdl = irfftw(in_cplx_pdl);

	   cplx_pdl = nfftw(cplx_pdl);
	   cplx_pdl = infftw(cplx_pdl);

	   cplx_pdl = Cmul(a_cplx_pdl, b_cplx_pdl);
	   cplx_pdl = Cconj(a_cplx_pdl);
	   real_pdl = Cmod(a_cplx_pdl);
	   real_pdl = Cmod2(a_cplx_pdl);

FFTW documentation
       Please refer to the FFTW documentation for a better understanding of these functions.

       Note that complex numbers are represented as piddles with leading dimension size 2 (real/imaginary pairs).

FUNCTIONS

   load_wisdom
       Loads the wisdom from a file for better FFTW performance.

       The wisdom is automatically saved when the program ends. It will be automagically called when the variable $PDL::FFT::wisdom is set to a
       file name.  For example, the following is a useful idiom to have in your .perldlrc file:

	 $PDL::FFT::wisdom = "$ENV{HOME}/.fftwisdom"; # save fftw wisdom in this file

       Explicit usage:

	 load_wisdom($fname);

   fftw
       calculate the complex FFT of a real piddle (complex input, complex output)

	  $pdl_cplx = fftw $pdl_cplx;

   ifftw
       Complex inverse FFT (complex input, complex output).

	  $pdl_cplx = ifftw $pdl_cplx;

   nfftw
       Complex inplace FFT (complex input, complex output).

	  $pdl_cplx = nfftw $pdl_cplx;

   infftw
       Complex inplace inverse FFT (complex input, complex output).

	  $pdl_cplx = infftw $pdl_cplx;

   rfftw
       Real FFT. For an input piddle of dimensions [n1,n2,...] the output is [2,(n1/2)+1,n2,...] (real input, complex output).

	 $pdl_cplx = fftw $pdl_real;

   irfftw
       Real inverse FFT. Have a look at rfftw to understand the format. USE ONLY an even n1! (complex input, real output)

	 $pdl_real = ifftw $pdl_cplx;

   nrfftw
       Real inplace FFT. If you want a transformation on a piddle with dimensions [n1,n2,....] you MUST pass in a piddle with dimensions
       [2*(n1/2+1),n2,...] (real input, complex output).

       Use with care due to dimension restrictions mentioned below.  For details check the html docs that come with the fftw library.

	 $pdl_cplx = nrfftw $pdl_real;

   inrfftw
       Real inplace inverse FFT. Have a look at nrfftw to understand the format. USE ONLY an even first dimension size! (complex input, real
       output)

	 $pdl_real = infftw $pdl_cplx;

   rfftwconv
       ND convolution using real ffts from the FFTW library

	 $conv = rfftwconv $im, kernctr $im, $k; # kernctr is from PDL::FFT

   fftwconv
       ND convolution using complex ffts from the FFTW library

       Assumes real input!

	 $conv = fftwconv $im, kernctr $im, $k; # kernctr is from PDL::FFT

   Cmul
	 Signature: (a(n); b(n); [o]c(n))

   Cmul
       Complex multiplication

	  $out_pdl_cplx = Cmul($a_pdl_cplx,$b_pdl_cplx);

       Cmul does not process bad values.  It will set the bad-value flag of all output piddles if the flag is set for any of the input piddles.

   Cscale
	 Signature: (a(n); b(); [o]c(n))

   Cscale
       Complex by real multiplation.

	 $out_pdl_cplx = Cscale($a_pdl_cplx,$b_pdl_real);

       Cscale does not process bad values.  It will set the bad-value flag of all output piddles if the flag is set for any of the input piddles.

   Cdiv
	 Signature: (a(n); b(n); [o]c(n))

   Cdiv
       Complex division.

	 $out_pdl_cplx = Cdiv($a_pdl_cplx,$b_pdl_cplx);

       Cdiv does not process bad values.  It will set the bad-value flag of all output piddles if the flag is set for any of the input piddles.

   Cbmul
	 Signature: (a(n); b(n))

   Cbmul
       Complex inplace multiplication.

	  Cbmul($a_pdl_cplx,$b_pdl_cplx);

       Cbmul does not process bad values.  It will set the bad-value flag of all output piddles if the flag is set for any of the input piddles.

   Cbscale
	 Signature: (a(n); b())

   Cbscale
       Complex inplace multiplaction by real.

	  Cbscale($a_pdl_cplx,$b_pdl_real);

       Cbscale does not process bad values.  It will set the bad-value flag of all output piddles if the flag is set for any of the input piddles.

   Cconj
	 Signature: (a(n); [o]c(n))

   Cconj
       Complex conjugate.

	  $out_pdl_cplx = Cconj($a_pdl_cplx);

       Cconj does not process bad values.  It will set the bad-value flag of all output piddles if the flag is set for any of the input piddles.

   Cbconj
	 Signature: (a(n))

   Cbconj
       Complex inplace conjugate.

	  Cbconj($a_pdl_cplx);

       Cbconj does not process bad values.  It will set the bad-value flag of all output piddles if the flag is set for any of the input piddles.

   Cexp
	 Signature: (a(n); [o]c(n))

   Cexp
       Complex exponentation.

	  $out_pdl_cplx = Cexp($a_pdl_cplx);

       Cexp does not process bad values.  It will set the bad-value flag of all output piddles if the flag is set for any of the input piddles.

   Cbexp
	 Signature: (a(n))

   Cbexp
       Complex inplace exponentation.

	  $out_pdl_cplx = Cbexp($a_pdl_cplx);

       Cbexp does not process bad values.  It will set the bad-value flag of all output piddles if the flag is set for any of the input piddles.

   Cmod
	 Signature: (a(n); [o]c())

   Cmod
       modulus of a complex piddle.

	 $out_pdl_real = Cmod($a_pdl_cplx);

       Cmod does not process bad values.  It will set the bad-value flag of all output piddles if the flag is set for any of the input piddles.

   Carg
	 Signature: (a(n); [o]c())

   Carg
       argument of a complex number.

	  $out_pdl_real = Carg($a_pdl_cplx);

       Carg does not process bad values.  It will set the bad-value flag of all output piddles if the flag is set for any of the input piddles.

   Cmod2
	 Signature: (a(n); [o]c())

   Cmod2
       Returns squared modulus of a complex number.

	  $out_pdl_real = Cmod2($a_pdl_cplx);

       Cmod2 does not process bad values.  It will set the bad-value flag of all output piddles if the flag is set for any of the input piddles.

AUTHOR

       Copyright (C) 1999 Christian Pellegrin, 2000 Christian Soeller.	All rights reserved. There is no warranty. You are allowed to redistribute
       this software / documentation under certain conditions. For details, see the file COPYING in the PDL distribution. If this file is
       separated from the PDL distribution, the copyright notice should be included in the file.

perl v5.14.2							    2012-05-30								 FFTW(3pm)