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Add FFTW 3.3.8 source, and a Linux build
author Chris Cannam
date Tue, 19 Nov 2019 14:52:55 +0000 (2019-11-19)
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rev   line source
Chris@82 1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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Chris@82 3 <!-- This manual is for FFTW
Chris@82 4 (version 3.3.8, 24 May 2018).
Chris@82 5
Chris@82 6 Copyright (C) 2003 Matteo Frigo.
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Chris@82 8 Copyright (C) 2003 Massachusetts Institute of Technology.
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Chris@82 24 <head>
Chris@82 25 <title>FFTW 3.3.8: Guru Complex DFTs</title>
Chris@82 26
Chris@82 27 <meta name="description" content="FFTW 3.3.8: Guru Complex DFTs">
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Chris@82 35 <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
Chris@82 36 <link href="Guru-Interface.html#Guru-Interface" rel="up" title="Guru Interface">
Chris@82 37 <link href="Guru-Real_002ddata-DFTs.html#Guru-Real_002ddata-DFTs" rel="next" title="Guru Real-data DFTs">
Chris@82 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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Chris@82 68 </head>
Chris@82 69
Chris@82 70 <body lang="en">
Chris@82 71 <a name="Guru-Complex-DFTs"></a>
Chris@82 72 <div class="header">
Chris@82 73 <p>
Chris@82 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>
Chris@82 75 </div>
Chris@82 76 <hr>
Chris@82 77 <a name="Guru-Complex-DFTs-1"></a>
Chris@82 78 <h4 class="subsection">4.5.3 Guru Complex DFTs</h4>
Chris@82 79
Chris@82 80 <div class="example">
Chris@82 81 <pre class="example">fftw_plan fftw_plan_guru_dft(
Chris@82 82 int rank, const fftw_iodim *dims,
Chris@82 83 int howmany_rank, const fftw_iodim *howmany_dims,
Chris@82 84 fftw_complex *in, fftw_complex *out,
Chris@82 85 int sign, unsigned flags);
Chris@82 86
Chris@82 87 fftw_plan fftw_plan_guru_split_dft(
Chris@82 88 int rank, const fftw_iodim *dims,
Chris@82 89 int howmany_rank, const fftw_iodim *howmany_dims,
Chris@82 90 double *ri, double *ii, double *ro, double *io,
Chris@82 91 unsigned flags);
Chris@82 92 </pre></div>
Chris@82 93 <a name="index-fftw_005fplan_005fguru_005fdft"></a>
Chris@82 94 <a name="index-fftw_005fplan_005fguru_005fsplit_005fdft"></a>
Chris@82 95
Chris@82 96 <p>These two functions plan a complex-data, multi-dimensional DFT
Chris@82 97 for the interleaved and split format, respectively.
Chris@82 98 Transform dimensions are given by (<code>rank</code>, <code>dims</code>) over a
Chris@82 99 multi-dimensional vector (loop) of dimensions (<code>howmany_rank</code>,
Chris@82 100 <code>howmany_dims</code>). <code>dims</code> and <code>howmany_dims</code> should point
Chris@82 101 to <code>fftw_iodim</code> arrays of length <code>rank</code> and
Chris@82 102 <code>howmany_rank</code>, respectively.
Chris@82 103 </p>
Chris@82 104 <a name="index-flags-5"></a>
Chris@82 105 <p><code>flags</code> is a bitwise OR (&lsquo;<samp>|</samp>&rsquo;) of zero or more planner flags,
Chris@82 106 as defined in <a href="Planner-Flags.html#Planner-Flags">Planner Flags</a>.
Chris@82 107 </p>
Chris@82 108 <p>In the <code>fftw_plan_guru_dft</code> function, the pointers <code>in</code> and
Chris@82 109 <code>out</code> point to the interleaved input and output arrays,
Chris@82 110 respectively. The sign can be either <em>-1</em> (=
Chris@82 111 <code>FFTW_FORWARD</code>) or <em>+1</em> (= <code>FFTW_BACKWARD</code>). If the
Chris@82 112 pointers are equal, the transform is in-place.
Chris@82 113 </p>
Chris@82 114 <p>In the <code>fftw_plan_guru_split_dft</code> function,
Chris@82 115 <code>ri</code> and <code>ii</code> point to the real and imaginary input arrays,
Chris@82 116 and <code>ro</code> and <code>io</code> point to the real and imaginary output
Chris@82 117 arrays. The input and output pointers may be the same, indicating an
Chris@82 118 in-place transform. For example, for <code>fftw_complex</code> pointers
Chris@82 119 <code>in</code> and <code>out</code>, the corresponding parameters are:
Chris@82 120 </p>
Chris@82 121 <div class="example">
Chris@82 122 <pre class="example">ri = (double *) in;
Chris@82 123 ii = (double *) in + 1;
Chris@82 124 ro = (double *) out;
Chris@82 125 io = (double *) out + 1;
Chris@82 126 </pre></div>
Chris@82 127
Chris@82 128 <p>Because <code>fftw_plan_guru_split_dft</code> accepts split arrays, strides
Chris@82 129 are expressed in units of <code>double</code>. For a contiguous
Chris@82 130 <code>fftw_complex</code> array, the overall stride of the transform should
Chris@82 131 be 2, the distance between consecutive real parts or between
Chris@82 132 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
Chris@82 133 real and imaginary parts; real and imaginary arrays with different
Chris@82 134 strides are not supported.
Chris@82 135 </p>
Chris@82 136 <p>There is no <code>sign</code> parameter in <code>fftw_plan_guru_split_dft</code>.
Chris@82 137 This function always plans for an <code>FFTW_FORWARD</code> transform. To
Chris@82 138 plan for an <code>FFTW_BACKWARD</code> transform, you can exploit the
Chris@82 139 identity that the backwards DFT is equal to the forwards DFT with the
Chris@82 140 real and imaginary parts swapped. For example, in the case of the
Chris@82 141 <code>fftw_complex</code> arrays above, the <code>FFTW_BACKWARD</code> transform
Chris@82 142 is computed by the parameters:
Chris@82 143 </p>
Chris@82 144 <div class="example">
Chris@82 145 <pre class="example">ri = (double *) in + 1;
Chris@82 146 ii = (double *) in;
Chris@82 147 ro = (double *) out + 1;
Chris@82 148 io = (double *) out;
Chris@82 149 </pre></div>
Chris@82 150
Chris@82 151 <hr>
Chris@82 152 <div class="header">
Chris@82 153 <p>
Chris@82 154 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>
Chris@82 155 </div>
Chris@82 156
Chris@82 157
Chris@82 158
Chris@82 159 </body>
Chris@82 160 </html>