Mercurial > hg > sv-dependency-builds

annotate src/fftw-3.3.3/doc/html/Guru-Complex-DFTs.html @ 83:ae30d91d2ffe

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Replace these with versions built using an older toolset (so as to avoid ABI compatibilities when linking on Ubuntu 14.04 for packaging purposes)
author Chris Cannam
date Fri, 07 Feb 2020 11:51:13 +0000
parents 37bf6b4a2645
children
rev   line source
Chris@10 1 <html lang="en">
Chris@10 2 <head>
Chris@10 3 <title>Guru Complex DFTs - FFTW 3.3.3</title>
Chris@10 4 <meta http-equiv="Content-Type" content="text/html">
Chris@10 5 <meta name="description" content="FFTW 3.3.3">
Chris@10 6 <meta name="generator" content="makeinfo 4.13">
Chris@10 7 <link title="Top" rel="start" href="index.html#Top">
Chris@10 8 <link rel="up" href="Guru-Interface.html#Guru-Interface" title="Guru Interface">
Chris@10 9 <link rel="prev" href="Guru-vector-and-transform-sizes.html#Guru-vector-and-transform-sizes" title="Guru vector and transform sizes">
Chris@10 10 <link rel="next" href="Guru-Real_002ddata-DFTs.html#Guru-Real_002ddata-DFTs" title="Guru Real-data DFTs">
Chris@10 11 <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
Chris@10 12 <!--
Chris@10 13 This manual is for FFTW
Chris@10 14 (version 3.3.3, 25 November 2012).
Chris@10 15
Chris@10 16 Copyright (C) 2003 Matteo Frigo.
Chris@10 17
Chris@10 18 Copyright (C) 2003 Massachusetts Institute of Technology.
Chris@10 19
Chris@10 20 Permission is granted to make and distribute verbatim copies of
Chris@10 21 this manual provided the copyright notice and this permission
Chris@10 22 notice are preserved on all copies.
Chris@10 23
Chris@10 24 Permission is granted to copy and distribute modified versions of
Chris@10 25 this manual under the conditions for verbatim copying, provided
Chris@10 26 that the entire resulting derived work is distributed under the
Chris@10 27 terms of a permission notice identical to this one.
Chris@10 28
Chris@10 29 Permission is granted to copy and distribute translations of this
Chris@10 30 manual into another language, under the above conditions for
Chris@10 31 modified versions, except that this permission notice may be
Chris@10 32 stated in a translation approved by the Free Software Foundation.
Chris@10 33 -->
Chris@10 34 <meta http-equiv="Content-Style-Type" content="text/css">
Chris@10 35 <style type="text/css"><!--
Chris@10 36 pre.display { font-family:inherit }
Chris@10 37 pre.format { font-family:inherit }
Chris@10 38 pre.smalldisplay { font-family:inherit; font-size:smaller }
Chris@10 39 pre.smallformat { font-family:inherit; font-size:smaller }
Chris@10 40 pre.smallexample { font-size:smaller }
Chris@10 41 pre.smalllisp { font-size:smaller }
Chris@10 42 span.sc { font-variant:small-caps }
Chris@10 43 span.roman { font-family:serif; font-weight:normal; }
Chris@10 44 span.sansserif { font-family:sans-serif; font-weight:normal; }
Chris@10 45 --></style>
Chris@10 46 </head>
Chris@10 47 <body>
Chris@10 48 <div class="node">
Chris@10 49 <a name="Guru-Complex-DFTs"></a>
Chris@10 50 <p>
Chris@10 51 Next:&nbsp;<a rel="next" accesskey="n" href="Guru-Real_002ddata-DFTs.html#Guru-Real_002ddata-DFTs">Guru Real-data DFTs</a>,
Chris@10 52 Previous:&nbsp;<a rel="previous" accesskey="p" href="Guru-vector-and-transform-sizes.html#Guru-vector-and-transform-sizes">Guru vector and transform sizes</a>,
Chris@10 53 Up:&nbsp;<a rel="up" accesskey="u" href="Guru-Interface.html#Guru-Interface">Guru Interface</a>
Chris@10 54 <hr>
Chris@10 55 </div>
Chris@10 56
Chris@10 57 <h4 class="subsection">4.5.3 Guru Complex DFTs</h4>
Chris@10 58
Chris@10 59 <pre class="example"> fftw_plan fftw_plan_guru_dft(
Chris@10 60 int rank, const fftw_iodim *dims,
Chris@10 61 int howmany_rank, const fftw_iodim *howmany_dims,
Chris@10 62 fftw_complex *in, fftw_complex *out,
Chris@10 63 int sign, unsigned flags);
Chris@10 64
Chris@10 65 fftw_plan fftw_plan_guru_split_dft(
Chris@10 66 int rank, const fftw_iodim *dims,
Chris@10 67 int howmany_rank, const fftw_iodim *howmany_dims,
Chris@10 68 double *ri, double *ii, double *ro, double *io,
Chris@10 69 unsigned flags);
Chris@10 70 </pre>
Chris@10 71 <p><a name="index-fftw_005fplan_005fguru_005fdft-248"></a><a name="index-fftw_005fplan_005fguru_005fsplit_005fdft-249"></a>
Chris@10 72 These two functions plan a complex-data, multi-dimensional DFT
Chris@10 73 for the interleaved and split format, respectively.
Chris@10 74 Transform dimensions are given by (<code>rank</code>, <code>dims</code>) over a
Chris@10 75 multi-dimensional vector (loop) of dimensions (<code>howmany_rank</code>,
Chris@10 76 <code>howmany_dims</code>). <code>dims</code> and <code>howmany_dims</code> should point
Chris@10 77 to <code>fftw_iodim</code> arrays of length <code>rank</code> and
Chris@10 78 <code>howmany_rank</code>, respectively.
Chris@10 79
Chris@10 80 <p><a name="index-flags-250"></a><code>flags</code> is a bitwise OR (&lsquo;<samp><span class="samp">|</span></samp>&rsquo;) of zero or more planner flags,
Chris@10 81 as defined in <a href="Planner-Flags.html#Planner-Flags">Planner Flags</a>.
Chris@10 82
Chris@10 83 <p>In the <code>fftw_plan_guru_dft</code> function, the pointers <code>in</code> and
Chris@10 84 <code>out</code> point to the interleaved input and output arrays,
Chris@10 85 respectively. The sign can be either -1 (=
Chris@10 86 <code>FFTW_FORWARD</code>) or +1 (= <code>FFTW_BACKWARD</code>). If the
Chris@10 87 pointers are equal, the transform is in-place.
Chris@10 88
Chris@10 89 <p>In the <code>fftw_plan_guru_split_dft</code> function,
Chris@10 90 <code>ri</code> and <code>ii</code> point to the real and imaginary input arrays,
Chris@10 91 and <code>ro</code> and <code>io</code> point to the real and imaginary output
Chris@10 92 arrays. The input and output pointers may be the same, indicating an
Chris@10 93 in-place transform. For example, for <code>fftw_complex</code> pointers
Chris@10 94 <code>in</code> and <code>out</code>, the corresponding parameters are:
Chris@10 95
Chris@10 96 <pre class="example"> ri = (double *) in;
Chris@10 97 ii = (double *) in + 1;
Chris@10 98 ro = (double *) out;
Chris@10 99 io = (double *) out + 1;
Chris@10 100 </pre>
Chris@10 101 <p>Because <code>fftw_plan_guru_split_dft</code> accepts split arrays, strides
Chris@10 102 are expressed in units of <code>double</code>. For a contiguous
Chris@10 103 <code>fftw_complex</code> array, the overall stride of the transform should
Chris@10 104 be 2, the distance between consecutive real parts or between
Chris@10 105 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
Chris@10 106 real and imaginary parts; real and imaginary arrays with different
Chris@10 107 strides are not supported.
Chris@10 108
Chris@10 109 <p>There is no <code>sign</code> parameter in <code>fftw_plan_guru_split_dft</code>.
Chris@10 110 This function always plans for an <code>FFTW_FORWARD</code> transform. To
Chris@10 111 plan for an <code>FFTW_BACKWARD</code> transform, you can exploit the
Chris@10 112 identity that the backwards DFT is equal to the forwards DFT with the
Chris@10 113 real and imaginary parts swapped. For example, in the case of the
Chris@10 114 <code>fftw_complex</code> arrays above, the <code>FFTW_BACKWARD</code> transform
Chris@10 115 is computed by the parameters:
Chris@10 116
Chris@10 117 <pre class="example"> ri = (double *) in + 1;
Chris@10 118 ii = (double *) in;
Chris@10 119 ro = (double *) out + 1;
Chris@10 120 io = (double *) out;
Chris@10 121 </pre>
Chris@10 122 <!-- =========> -->
Chris@10 123 </body></html>
Chris@10 124