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Current fftw source
author Chris Cannam
date Tue, 18 Oct 2016 13:40:26 +0100
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Chris@42 1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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Chris@42 3 <!-- This manual is for FFTW
Chris@42 4 (version 3.3.5, 30 July 2016).
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Chris@42 6 Copyright (C) 2003 Matteo Frigo.
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Chris@42 8 Copyright (C) 2003 Massachusetts Institute of Technology.
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Chris@42 24 <head>
Chris@42 25 <title>FFTW 3.3.5: Advanced Real-data DFTs</title>
Chris@42 26
Chris@42 27 <meta name="description" content="FFTW 3.3.5: Advanced Real-data DFTs">
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Chris@42 36 <link href="Advanced-Interface.html#Advanced-Interface" rel="up" title="Advanced Interface">
Chris@42 37 <link href="Advanced-Real_002dto_002dreal-Transforms.html#Advanced-Real_002dto_002dreal-Transforms" rel="next" title="Advanced Real-to-real Transforms">
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Chris@42 69 </head>
Chris@42 70
Chris@42 71 <body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
Chris@42 72 <a name="Advanced-Real_002ddata-DFTs"></a>
Chris@42 73 <div class="header">
Chris@42 74 <p>
Chris@42 75 Next: <a href="Advanced-Real_002dto_002dreal-Transforms.html#Advanced-Real_002dto_002dreal-Transforms" accesskey="n" rel="next">Advanced Real-to-real Transforms</a>, Previous: <a href="Advanced-Complex-DFTs.html#Advanced-Complex-DFTs" accesskey="p" rel="prev">Advanced Complex DFTs</a>, Up: <a href="Advanced-Interface.html#Advanced-Interface" accesskey="u" rel="up">Advanced 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@42 76 </div>
Chris@42 77 <hr>
Chris@42 78 <a name="Advanced-Real_002ddata-DFTs-1"></a>
Chris@42 79 <h4 class="subsection">4.4.2 Advanced Real-data DFTs</h4>
Chris@42 80
Chris@42 81 <div class="example">
Chris@42 82 <pre class="example">fftw_plan fftw_plan_many_dft_r2c(int rank, const int *n, int howmany,
Chris@42 83 double *in, const int *inembed,
Chris@42 84 int istride, int idist,
Chris@42 85 fftw_complex *out, const int *onembed,
Chris@42 86 int ostride, int odist,
Chris@42 87 unsigned flags);
Chris@42 88 fftw_plan fftw_plan_many_dft_c2r(int rank, const int *n, int howmany,
Chris@42 89 fftw_complex *in, const int *inembed,
Chris@42 90 int istride, int idist,
Chris@42 91 double *out, const int *onembed,
Chris@42 92 int ostride, int odist,
Chris@42 93 unsigned flags);
Chris@42 94 </pre></div>
Chris@42 95 <a name="index-fftw_005fplan_005fmany_005fdft_005fr2c"></a>
Chris@42 96 <a name="index-fftw_005fplan_005fmany_005fdft_005fc2r"></a>
Chris@42 97
Chris@42 98 <p>Like <code>fftw_plan_many_dft</code>, these two functions add <code>howmany</code>,
Chris@42 99 <code>nembed</code>, <code>stride</code>, and <code>dist</code> parameters to the
Chris@42 100 <code>fftw_plan_dft_r2c</code> and <code>fftw_plan_dft_c2r</code> functions, but
Chris@42 101 otherwise behave the same as the basic interface.
Chris@42 102 </p>
Chris@42 103 <p>The interpretation of <code>howmany</code>, <code>stride</code>, and <code>dist</code> are
Chris@42 104 the same as for <code>fftw_plan_many_dft</code>, above. Note that the
Chris@42 105 <code>stride</code> and <code>dist</code> for the real array are in units of
Chris@42 106 <code>double</code>, and for the complex array are in units of
Chris@42 107 <code>fftw_complex</code>.
Chris@42 108 </p>
Chris@42 109 <p>If an <code>nembed</code> parameter is <code>NULL</code>, it is interpreted as what
Chris@42 110 it would be in the basic interface, as described in <a href="Real_002ddata-DFT-Array-Format.html#Real_002ddata-DFT-Array-Format">Real-data DFT Array Format</a>. That is, for the complex array the size is assumed to be
Chris@42 111 the same as <code>n</code>, but with the last dimension cut roughly in half.
Chris@42 112 For the real array, the size is assumed to be <code>n</code> if the transform
Chris@42 113 is out-of-place, or <code>n</code> with the last dimension &ldquo;padded&rdquo; if the
Chris@42 114 transform is in-place.
Chris@42 115 </p>
Chris@42 116 <p>If an <code>nembed</code> parameter is non-<code>NULL</code>, it is interpreted as
Chris@42 117 the physical size of the corresponding array, in row-major order, just
Chris@42 118 as for <code>fftw_plan_many_dft</code>. In this case, each dimension of
Chris@42 119 <code>nembed</code> should be <code>&gt;=</code> what it would be in the basic
Chris@42 120 interface (e.g. the halved or padded <code>n</code>).
Chris@42 121 </p>
Chris@42 122 <p>Arrays <code>n</code>, <code>inembed</code>, and <code>onembed</code> are not used after
Chris@42 123 this function returns. You can safely free or reuse them.
Chris@42 124 </p>
Chris@42 125 <hr>
Chris@42 126 <div class="header">
Chris@42 127 <p>
Chris@42 128 Next: <a href="Advanced-Real_002dto_002dreal-Transforms.html#Advanced-Real_002dto_002dreal-Transforms" accesskey="n" rel="next">Advanced Real-to-real Transforms</a>, Previous: <a href="Advanced-Complex-DFTs.html#Advanced-Complex-DFTs" accesskey="p" rel="prev">Advanced Complex DFTs</a>, Up: <a href="Advanced-Interface.html#Advanced-Interface" accesskey="u" rel="up">Advanced 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@42 129 </div>
Chris@42 130
Chris@42 131
Chris@42 132
Chris@42 133 </body>
Chris@42 134 </html>