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| author | Chris Cannam <cannam@all-day-breakfast.com> |
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| date | Wed, 20 Mar 2013 15:35:50 +0000 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/fftw-3.3.3/doc/html/Guru-Complex-DFTs.html Wed Mar 20 15:35:50 2013 +0000 @@ -0,0 +1,124 @@ +<html lang="en"> +<head> +<title>Guru Complex DFTs - FFTW 3.3.3</title> +<meta http-equiv="Content-Type" content="text/html"> +<meta name="description" content="FFTW 3.3.3"> +<meta name="generator" content="makeinfo 4.13"> +<link title="Top" rel="start" href="index.html#Top"> +<link rel="up" href="Guru-Interface.html#Guru-Interface" title="Guru Interface"> +<link rel="prev" href="Guru-vector-and-transform-sizes.html#Guru-vector-and-transform-sizes" title="Guru vector and transform sizes"> +<link rel="next" href="Guru-Real_002ddata-DFTs.html#Guru-Real_002ddata-DFTs" title="Guru Real-data DFTs"> +<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> +<!-- +This manual is for FFTW +(version 3.3.3, 25 November 2012). + +Copyright (C) 2003 Matteo Frigo. + +Copyright (C) 2003 Massachusetts Institute of Technology. + + Permission is granted to make and distribute verbatim copies of + this manual provided the copyright notice and this permission + notice are preserved on all copies. + + Permission is granted to copy and distribute modified versions of + this manual under the conditions for verbatim copying, provided + that the entire resulting derived work is distributed under the + terms of a permission notice identical to this one. + + Permission is granted to copy and distribute translations of this + manual into another language, under the above conditions for + modified versions, except that this permission notice may be + stated in a translation approved by the Free Software Foundation. + --> +<meta http-equiv="Content-Style-Type" content="text/css"> +<style type="text/css"><!-- + pre.display { font-family:inherit } + pre.format { font-family:inherit } + pre.smalldisplay { font-family:inherit; font-size:smaller } + pre.smallformat { font-family:inherit; font-size:smaller } + pre.smallexample { font-size:smaller } + pre.smalllisp { font-size:smaller } + span.sc { font-variant:small-caps } + span.roman { font-family:serif; font-weight:normal; } + span.sansserif { font-family:sans-serif; font-weight:normal; } +--></style> +</head> +<body> +<div class="node"> +<a name="Guru-Complex-DFTs"></a> +<p> +Next: <a rel="next" accesskey="n" href="Guru-Real_002ddata-DFTs.html#Guru-Real_002ddata-DFTs">Guru Real-data DFTs</a>, +Previous: <a rel="previous" accesskey="p" href="Guru-vector-and-transform-sizes.html#Guru-vector-and-transform-sizes">Guru vector and transform sizes</a>, +Up: <a rel="up" accesskey="u" href="Guru-Interface.html#Guru-Interface">Guru Interface</a> +<hr> +</div> + +<h4 class="subsection">4.5.3 Guru Complex DFTs</h4> + +<pre class="example"> fftw_plan fftw_plan_guru_dft( + int rank, const fftw_iodim *dims, + int howmany_rank, const fftw_iodim *howmany_dims, + fftw_complex *in, fftw_complex *out, + int sign, unsigned flags); + + fftw_plan fftw_plan_guru_split_dft( + int rank, const fftw_iodim *dims, + int howmany_rank, const fftw_iodim *howmany_dims, + double *ri, double *ii, double *ro, double *io, + unsigned flags); +</pre> + <p><a name="index-fftw_005fplan_005fguru_005fdft-248"></a><a name="index-fftw_005fplan_005fguru_005fsplit_005fdft-249"></a> +These two functions plan a complex-data, multi-dimensional DFT +for the interleaved and split format, respectively. +Transform dimensions are given by (<code>rank</code>, <code>dims</code>) over a +multi-dimensional vector (loop) of dimensions (<code>howmany_rank</code>, +<code>howmany_dims</code>). <code>dims</code> and <code>howmany_dims</code> should point +to <code>fftw_iodim</code> arrays of length <code>rank</code> and +<code>howmany_rank</code>, respectively. + + <p><a name="index-flags-250"></a><code>flags</code> is a bitwise OR (‘<samp><span class="samp">|</span></samp>’) of zero or more planner flags, +as defined in <a href="Planner-Flags.html#Planner-Flags">Planner Flags</a>. + + <p>In the <code>fftw_plan_guru_dft</code> function, the pointers <code>in</code> and +<code>out</code> point to the interleaved input and output arrays, +respectively. The sign can be either -1 (= +<code>FFTW_FORWARD</code>) or +1 (= <code>FFTW_BACKWARD</code>). If the +pointers are equal, the transform is in-place. + + <p>In the <code>fftw_plan_guru_split_dft</code> function, +<code>ri</code> and <code>ii</code> point to the real and imaginary input arrays, +and <code>ro</code> and <code>io</code> point to the real and imaginary output +arrays. The input and output pointers may be the same, indicating an +in-place transform. For example, for <code>fftw_complex</code> pointers +<code>in</code> and <code>out</code>, the corresponding parameters are: + +<pre class="example"> ri = (double *) in; + ii = (double *) in + 1; + ro = (double *) out; + io = (double *) out + 1; +</pre> + <p>Because <code>fftw_plan_guru_split_dft</code> accepts split arrays, strides +are expressed in units of <code>double</code>. For a contiguous +<code>fftw_complex</code> array, the overall stride of the transform should +be 2, the distance between consecutive real parts or between +consecutive imaginary parts; see <a href="Guru-vector-and-transform-sizes.html#Guru-vector-and-transform-sizes">Guru vector and transform sizes</a>. Note that the dimension strides are applied equally to the +real and imaginary parts; real and imaginary arrays with different +strides are not supported. + + <p>There is no <code>sign</code> parameter in <code>fftw_plan_guru_split_dft</code>. +This function always plans for an <code>FFTW_FORWARD</code> transform. To +plan for an <code>FFTW_BACKWARD</code> transform, you can exploit the +identity that the backwards DFT is equal to the forwards DFT with the +real and imaginary parts swapped. For example, in the case of the +<code>fftw_complex</code> arrays above, the <code>FFTW_BACKWARD</code> transform +is computed by the parameters: + +<pre class="example"> ri = (double *) in + 1; + ii = (double *) in; + ro = (double *) out + 1; + io = (double *) out; +</pre> + <!-- =========> --> + </body></html> +