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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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1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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3 <!-- This manual is for FFTW
4 (version 3.3.8, 24 May 2018).
5
6 Copyright (C) 2003 Matteo Frigo.
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8 Copyright (C) 2003 Massachusetts Institute of Technology.
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24 <head>
25 <title>FFTW 3.3.8: Guru Real-data DFTs</title>
26
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35 <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
36 <link href="Guru-Interface.html#Guru-Interface" rel="up" title="Guru Interface">
37 <link href="Guru-Real_002dto_002dreal-Transforms.html#Guru-Real_002dto_002dreal-Transforms" rel="next" title="Guru Real-to-real Transforms">
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70 <body lang="en">
71 <a name="Guru-Real_002ddata-DFTs"></a>
72 <div class="header">
73 <p>
74 Next: <a href="Guru-Real_002dto_002dreal-Transforms.html#Guru-Real_002dto_002dreal-Transforms" accesskey="n" rel="next">Guru Real-to-real Transforms</a>, Previous: <a href="Guru-Complex-DFTs.html#Guru-Complex-DFTs" accesskey="p" rel="prev">Guru Complex DFTs</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>
75 </div>
76 <hr>
77 <a name="Guru-Real_002ddata-DFTs-1"></a>
78 <h4 class="subsection">4.5.4 Guru Real-data DFTs</h4>
79
80 <div class="example">
81 <pre class="example">fftw_plan fftw_plan_guru_dft_r2c(
82 int rank, const fftw_iodim *dims,
83 int howmany_rank, const fftw_iodim *howmany_dims,
84 double *in, fftw_complex *out,
85 unsigned flags);
86
87 fftw_plan fftw_plan_guru_split_dft_r2c(
88 int rank, const fftw_iodim *dims,
89 int howmany_rank, const fftw_iodim *howmany_dims,
90 double *in, double *ro, double *io,
91 unsigned flags);
92
93 fftw_plan fftw_plan_guru_dft_c2r(
94 int rank, const fftw_iodim *dims,
95 int howmany_rank, const fftw_iodim *howmany_dims,
96 fftw_complex *in, double *out,
97 unsigned flags);
98
99 fftw_plan fftw_plan_guru_split_dft_c2r(
100 int rank, const fftw_iodim *dims,
101 int howmany_rank, const fftw_iodim *howmany_dims,
102 double *ri, double *ii, double *out,
103 unsigned flags);
104 </pre></div>
105 <a name="index-fftw_005fplan_005fguru_005fdft_005fr2c"></a>
106 <a name="index-fftw_005fplan_005fguru_005fsplit_005fdft_005fr2c"></a>
107 <a name="index-fftw_005fplan_005fguru_005fdft_005fc2r"></a>
108 <a name="index-fftw_005fplan_005fguru_005fsplit_005fdft_005fc2r"></a>
109
110 <p>Plan a real-input (r2c) or real-output (c2r), multi-dimensional DFT with
111 transform dimensions given by (<code>rank</code>, <code>dims</code>) over a
112 multi-dimensional vector (loop) of dimensions (<code>howmany_rank</code>,
113 <code>howmany_dims</code>). <code>dims</code> and <code>howmany_dims</code> should point
114 to <code>fftw_iodim</code> arrays of length <code>rank</code> and
115 <code>howmany_rank</code>, respectively. As for the basic and advanced
116 interfaces, an r2c transform is <code>FFTW_FORWARD</code> and a c2r transform
117 is <code>FFTW_BACKWARD</code>.
118 </p>
119 <p>The <em>last</em> dimension of <code>dims</code> is interpreted specially:
120 that dimension of the real array has size <code>dims[rank-1].n</code>, but
121 that dimension of the complex array has size <code>dims[rank-1].n/2+1</code>
122 (division rounded down). The strides, on the other hand, are taken to
123 be exactly as specified. It is up to the user to specify the strides
124 appropriately for the peculiar dimensions of the data, and we do not
125 guarantee that the planner will succeed (return non-<code>NULL</code>) for
126 any dimensions other than those described in <a href="Real_002ddata-DFT-Array-Format.html#Real_002ddata-DFT-Array-Format">Real-data DFT Array Format</a> and generalized in <a href="Advanced-Real_002ddata-DFTs.html#Advanced-Real_002ddata-DFTs">Advanced Real-data DFTs</a>. (That is,
127 for an in-place transform, each individual dimension should be able to
128 operate in place.)
129 <a name="index-in_002dplace-6"></a>
130 </p>
131
132 <p><code>in</code> and <code>out</code> point to the input and output arrays for r2c
133 and c2r transforms, respectively. For split arrays, <code>ri</code> and
134 <code>ii</code> point to the real and imaginary input arrays for a c2r
135 transform, and <code>ro</code> and <code>io</code> point to the real and imaginary
136 output arrays for an r2c transform. <code>in</code> and <code>ro</code> or
137 <code>ri</code> and <code>out</code> may be the same, indicating an in-place
138 transform. (In-place transforms where <code>in</code> and <code>io</code> or
139 <code>ii</code> and <code>out</code> are the same are not currently supported.)
140 </p>
141 <a name="index-flags-6"></a>
142 <p><code>flags</code> is a bitwise OR (&lsquo;<samp>|</samp>&rsquo;) of zero or more planner flags,
143 as defined in <a href="Planner-Flags.html#Planner-Flags">Planner Flags</a>.
144 </p>
145 <p>In-place transforms of rank greater than 1 are currently only
146 supported for interleaved arrays. For split arrays, the planner will
147 return <code>NULL</code>.
148 <a name="index-in_002dplace-7"></a>
149 </p>
150 <hr>
151 <div class="header">
152 <p>
153 Next: <a href="Guru-Real_002dto_002dreal-Transforms.html#Guru-Real_002dto_002dreal-Transforms" accesskey="n" rel="next">Guru Real-to-real Transforms</a>, Previous: <a href="Guru-Complex-DFTs.html#Guru-Complex-DFTs" accesskey="p" rel="prev">Guru Complex DFTs</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>
154 </div>
155
156
157
158 </body>
159 </html>