150 lines
6.8 KiB
HTML
150 lines
6.8 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
|
<html>
|
|
<!-- This manual is for FFTW
|
|
(version 3.3.10, 10 December 2020).
|
|
|
|
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. -->
|
|
<!-- Created by GNU Texinfo 6.7, http://www.gnu.org/software/texinfo/ -->
|
|
<head>
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
|
|
<title>Guru Complex DFTs (FFTW 3.3.10)</title>
|
|
|
|
<meta name="description" content="Guru Complex DFTs (FFTW 3.3.10)">
|
|
<meta name="keywords" content="Guru Complex DFTs (FFTW 3.3.10)">
|
|
<meta name="resource-type" content="document">
|
|
<meta name="distribution" content="global">
|
|
<meta name="Generator" content="makeinfo">
|
|
<link href="index.html" rel="start" title="Top">
|
|
<link href="Concept-Index.html" rel="index" title="Concept Index">
|
|
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
|
|
<link href="Guru-Interface.html" rel="up" title="Guru Interface">
|
|
<link href="Guru-Real_002ddata-DFTs.html" rel="next" title="Guru Real-data DFTs">
|
|
<link href="Guru-vector-and-transform-sizes.html" rel="prev" title="Guru vector and transform sizes">
|
|
<style type="text/css">
|
|
<!--
|
|
a.summary-letter {text-decoration: none}
|
|
blockquote.indentedblock {margin-right: 0em}
|
|
div.display {margin-left: 3.2em}
|
|
div.example {margin-left: 3.2em}
|
|
div.lisp {margin-left: 3.2em}
|
|
kbd {font-style: oblique}
|
|
pre.display {font-family: inherit}
|
|
pre.format {font-family: inherit}
|
|
pre.menu-comment {font-family: serif}
|
|
pre.menu-preformatted {font-family: serif}
|
|
span.nolinebreak {white-space: nowrap}
|
|
span.roman {font-family: initial; font-weight: normal}
|
|
span.sansserif {font-family: sans-serif; font-weight: normal}
|
|
ul.no-bullet {list-style: none}
|
|
-->
|
|
</style>
|
|
|
|
|
|
</head>
|
|
|
|
<body lang="en">
|
|
<span id="Guru-Complex-DFTs"></span><div class="header">
|
|
<p>
|
|
Next: <a href="Guru-Real_002ddata-DFTs.html" accesskey="n" rel="next">Guru Real-data DFTs</a>, Previous: <a href="Guru-vector-and-transform-sizes.html" accesskey="p" rel="prev">Guru vector and transform sizes</a>, Up: <a href="Guru-Interface.html" accesskey="u" rel="up">Guru Interface</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
|
|
</div>
|
|
<hr>
|
|
<span id="Guru-Complex-DFTs-1"></span><h4 class="subsection">4.5.3 Guru Complex DFTs</h4>
|
|
|
|
<div class="example">
|
|
<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></div>
|
|
<span id="index-fftw_005fplan_005fguru_005fdft"></span>
|
|
<span id="index-fftw_005fplan_005fguru_005fsplit_005fdft"></span>
|
|
|
|
<p>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>
|
|
<span id="index-flags-5"></span>
|
|
<p><code>flags</code> is a bitwise OR (‘<samp>|</samp>’) of zero or more planner flags,
|
|
as defined in <a href="Planner-Flags.html">Planner Flags</a>.
|
|
</p>
|
|
<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 <em>-1</em> (=
|
|
<code>FFTW_FORWARD</code>) or <em>+1</em> (= <code>FFTW_BACKWARD</code>). If the
|
|
pointers are equal, the transform is in-place.
|
|
</p>
|
|
<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:
|
|
</p>
|
|
<div class="example">
|
|
<pre class="example">ri = (double *) in;
|
|
ii = (double *) in + 1;
|
|
ro = (double *) out;
|
|
io = (double *) out + 1;
|
|
</pre></div>
|
|
|
|
<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</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>
|
|
<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:
|
|
</p>
|
|
<div class="example">
|
|
<pre class="example">ri = (double *) in + 1;
|
|
ii = (double *) in;
|
|
ro = (double *) out + 1;
|
|
io = (double *) out;
|
|
</pre></div>
|
|
|
|
<hr>
|
|
<div class="header">
|
|
<p>
|
|
Next: <a href="Guru-Real_002ddata-DFTs.html" accesskey="n" rel="next">Guru Real-data DFTs</a>, Previous: <a href="Guru-vector-and-transform-sizes.html" accesskey="p" rel="prev">Guru vector and transform sizes</a>, Up: <a href="Guru-Interface.html" accesskey="u" rel="up">Guru Interface</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
|
|
</div>
|
|
|
|
|
|
|
|
</body>
|
|
</html>
|