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Add FFTW 3.3.8 source, and a Linux build
author Chris Cannam <cannam@all-day-breakfast.com>
date Tue, 19 Nov 2019 14:52:55 +0000
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cannam@167 1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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cannam@167 3 <!-- This manual is for FFTW
cannam@167 4 (version 3.3.8, 24 May 2018).
cannam@167 5
cannam@167 6 Copyright (C) 2003 Matteo Frigo.
cannam@167 7
cannam@167 8 Copyright (C) 2003 Massachusetts Institute of Technology.
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cannam@167 24 <head>
cannam@167 25 <title>FFTW 3.3.8: Guru Complex DFTs</title>
cannam@167 26
cannam@167 27 <meta name="description" content="FFTW 3.3.8: Guru Complex DFTs">
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cannam@167 35 <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
cannam@167 36 <link href="Guru-Interface.html#Guru-Interface" rel="up" title="Guru Interface">
cannam@167 37 <link href="Guru-Real_002ddata-DFTs.html#Guru-Real_002ddata-DFTs" rel="next" title="Guru Real-data DFTs">
cannam@167 38 <link href="Guru-vector-and-transform-sizes.html#Guru-vector-and-transform-sizes" rel="prev" title="Guru vector and transform sizes">
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cannam@167 68 </head>
cannam@167 69
cannam@167 70 <body lang="en">
cannam@167 71 <a name="Guru-Complex-DFTs"></a>
cannam@167 72 <div class="header">
cannam@167 73 <p>
cannam@167 74 Next: <a href="Guru-Real_002ddata-DFTs.html#Guru-Real_002ddata-DFTs" accesskey="n" rel="next">Guru Real-data DFTs</a>, Previous: <a href="Guru-vector-and-transform-sizes.html#Guru-vector-and-transform-sizes" accesskey="p" rel="prev">Guru vector and transform sizes</a>, Up: <a href="Guru-Interface.html#Guru-Interface" accesskey="u" rel="up">Guru Interface</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
cannam@167 75 </div>
cannam@167 76 <hr>
cannam@167 77 <a name="Guru-Complex-DFTs-1"></a>
cannam@167 78 <h4 class="subsection">4.5.3 Guru Complex DFTs</h4>
cannam@167 79
cannam@167 80 <div class="example">
cannam@167 81 <pre class="example">fftw_plan fftw_plan_guru_dft(
cannam@167 82 int rank, const fftw_iodim *dims,
cannam@167 83 int howmany_rank, const fftw_iodim *howmany_dims,
cannam@167 84 fftw_complex *in, fftw_complex *out,
cannam@167 85 int sign, unsigned flags);
cannam@167 86
cannam@167 87 fftw_plan fftw_plan_guru_split_dft(
cannam@167 88 int rank, const fftw_iodim *dims,
cannam@167 89 int howmany_rank, const fftw_iodim *howmany_dims,
cannam@167 90 double *ri, double *ii, double *ro, double *io,
cannam@167 91 unsigned flags);
cannam@167 92 </pre></div>
cannam@167 93 <a name="index-fftw_005fplan_005fguru_005fdft"></a>
cannam@167 94 <a name="index-fftw_005fplan_005fguru_005fsplit_005fdft"></a>
cannam@167 95
cannam@167 96 <p>These two functions plan a complex-data, multi-dimensional DFT
cannam@167 97 for the interleaved and split format, respectively.
cannam@167 98 Transform dimensions are given by (<code>rank</code>, <code>dims</code>) over a
cannam@167 99 multi-dimensional vector (loop) of dimensions (<code>howmany_rank</code>,
cannam@167 100 <code>howmany_dims</code>). <code>dims</code> and <code>howmany_dims</code> should point
cannam@167 101 to <code>fftw_iodim</code> arrays of length <code>rank</code> and
cannam@167 102 <code>howmany_rank</code>, respectively.
cannam@167 103 </p>
cannam@167 104 <a name="index-flags-5"></a>
cannam@167 105 <p><code>flags</code> is a bitwise OR (&lsquo;<samp>|</samp>&rsquo;) of zero or more planner flags,
cannam@167 106 as defined in <a href="Planner-Flags.html#Planner-Flags">Planner Flags</a>.
cannam@167 107 </p>
cannam@167 108 <p>In the <code>fftw_plan_guru_dft</code> function, the pointers <code>in</code> and
cannam@167 109 <code>out</code> point to the interleaved input and output arrays,
cannam@167 110 respectively. The sign can be either <em>-1</em> (=
cannam@167 111 <code>FFTW_FORWARD</code>) or <em>+1</em> (= <code>FFTW_BACKWARD</code>). If the
cannam@167 112 pointers are equal, the transform is in-place.
cannam@167 113 </p>
cannam@167 114 <p>In the <code>fftw_plan_guru_split_dft</code> function,
cannam@167 115 <code>ri</code> and <code>ii</code> point to the real and imaginary input arrays,
cannam@167 116 and <code>ro</code> and <code>io</code> point to the real and imaginary output
cannam@167 117 arrays. The input and output pointers may be the same, indicating an
cannam@167 118 in-place transform. For example, for <code>fftw_complex</code> pointers
cannam@167 119 <code>in</code> and <code>out</code>, the corresponding parameters are:
cannam@167 120 </p>
cannam@167 121 <div class="example">
cannam@167 122 <pre class="example">ri = (double *) in;
cannam@167 123 ii = (double *) in + 1;
cannam@167 124 ro = (double *) out;
cannam@167 125 io = (double *) out + 1;
cannam@167 126 </pre></div>
cannam@167 127
cannam@167 128 <p>Because <code>fftw_plan_guru_split_dft</code> accepts split arrays, strides
cannam@167 129 are expressed in units of <code>double</code>. For a contiguous
cannam@167 130 <code>fftw_complex</code> array, the overall stride of the transform should
cannam@167 131 be 2, the distance between consecutive real parts or between
cannam@167 132 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
cannam@167 133 real and imaginary parts; real and imaginary arrays with different
cannam@167 134 strides are not supported.
cannam@167 135 </p>
cannam@167 136 <p>There is no <code>sign</code> parameter in <code>fftw_plan_guru_split_dft</code>.
cannam@167 137 This function always plans for an <code>FFTW_FORWARD</code> transform. To
cannam@167 138 plan for an <code>FFTW_BACKWARD</code> transform, you can exploit the
cannam@167 139 identity that the backwards DFT is equal to the forwards DFT with the
cannam@167 140 real and imaginary parts swapped. For example, in the case of the
cannam@167 141 <code>fftw_complex</code> arrays above, the <code>FFTW_BACKWARD</code> transform
cannam@167 142 is computed by the parameters:
cannam@167 143 </p>
cannam@167 144 <div class="example">
cannam@167 145 <pre class="example">ri = (double *) in + 1;
cannam@167 146 ii = (double *) in;
cannam@167 147 ro = (double *) out + 1;
cannam@167 148 io = (double *) out;
cannam@167 149 </pre></div>
cannam@167 150
cannam@167 151 <hr>
cannam@167 152 <div class="header">
cannam@167 153 <p>
cannam@167 154 Next: <a href="Guru-Real_002ddata-DFTs.html#Guru-Real_002ddata-DFTs" accesskey="n" rel="next">Guru Real-data DFTs</a>, Previous: <a href="Guru-vector-and-transform-sizes.html#Guru-vector-and-transform-sizes" accesskey="p" rel="prev">Guru vector and transform sizes</a>, Up: <a href="Guru-Interface.html#Guru-Interface" accesskey="u" rel="up">Guru Interface</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
cannam@167 155 </div>
cannam@167 156
cannam@167 157
cannam@167 158
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cannam@167 160 </html>