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Add FFTW3
author Chris Cannam <cannam@all-day-breakfast.com>
date Wed, 20 Mar 2013 15:35:50 +0000
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cannam@95 1 <html lang="en">
cannam@95 2 <head>
cannam@95 3 <title>Advanced Real-data DFTs - FFTW 3.3.3</title>
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cannam@95 8 <link rel="up" href="Advanced-Interface.html#Advanced-Interface" title="Advanced Interface">
cannam@95 9 <link rel="prev" href="Advanced-Complex-DFTs.html#Advanced-Complex-DFTs" title="Advanced Complex DFTs">
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cannam@95 12 <!--
cannam@95 13 This manual is for FFTW
cannam@95 14 (version 3.3.3, 25 November 2012).
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cannam@95 16 Copyright (C) 2003 Matteo Frigo.
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cannam@95 18 Copyright (C) 2003 Massachusetts Institute of Technology.
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cannam@95 48 <div class="node">
cannam@95 49 <a name="Advanced-Real-data-DFTs"></a>
cannam@95 50 <a name="Advanced-Real_002ddata-DFTs"></a>
cannam@95 51 <p>
cannam@95 52 Next:&nbsp;<a rel="next" accesskey="n" href="Advanced-Real_002dto_002dreal-Transforms.html#Advanced-Real_002dto_002dreal-Transforms">Advanced Real-to-real Transforms</a>,
cannam@95 53 Previous:&nbsp;<a rel="previous" accesskey="p" href="Advanced-Complex-DFTs.html#Advanced-Complex-DFTs">Advanced Complex DFTs</a>,
cannam@95 54 Up:&nbsp;<a rel="up" accesskey="u" href="Advanced-Interface.html#Advanced-Interface">Advanced Interface</a>
cannam@95 55 <hr>
cannam@95 56 </div>
cannam@95 57
cannam@95 58 <h4 class="subsection">4.4.2 Advanced Real-data DFTs</h4>
cannam@95 59
cannam@95 60 <pre class="example"> fftw_plan fftw_plan_many_dft_r2c(int rank, const int *n, int howmany,
cannam@95 61 double *in, const int *inembed,
cannam@95 62 int istride, int idist,
cannam@95 63 fftw_complex *out, const int *onembed,
cannam@95 64 int ostride, int odist,
cannam@95 65 unsigned flags);
cannam@95 66 fftw_plan fftw_plan_many_dft_c2r(int rank, const int *n, int howmany,
cannam@95 67 fftw_complex *in, const int *inembed,
cannam@95 68 int istride, int idist,
cannam@95 69 double *out, const int *onembed,
cannam@95 70 int ostride, int odist,
cannam@95 71 unsigned flags);
cannam@95 72 </pre>
cannam@95 73 <p><a name="index-fftw_005fplan_005fmany_005fdft_005fr2c-236"></a><a name="index-fftw_005fplan_005fmany_005fdft_005fc2r-237"></a>
cannam@95 74 Like <code>fftw_plan_many_dft</code>, these two functions add <code>howmany</code>,
cannam@95 75 <code>nembed</code>, <code>stride</code>, and <code>dist</code> parameters to the
cannam@95 76 <code>fftw_plan_dft_r2c</code> and <code>fftw_plan_dft_c2r</code> functions, but
cannam@95 77 otherwise behave the same as the basic interface.
cannam@95 78
cannam@95 79 <p>The interpretation of <code>howmany</code>, <code>stride</code>, and <code>dist</code> are
cannam@95 80 the same as for <code>fftw_plan_many_dft</code>, above. Note that the
cannam@95 81 <code>stride</code> and <code>dist</code> for the real array are in units of
cannam@95 82 <code>double</code>, and for the complex array are in units of
cannam@95 83 <code>fftw_complex</code>.
cannam@95 84
cannam@95 85 <p>If an <code>nembed</code> parameter is <code>NULL</code>, it is interpreted as what
cannam@95 86 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
cannam@95 87 the same as <code>n</code>, but with the last dimension cut roughly in half.
cannam@95 88 For the real array, the size is assumed to be <code>n</code> if the transform
cannam@95 89 is out-of-place, or <code>n</code> with the last dimension &ldquo;padded&rdquo; if the
cannam@95 90 transform is in-place.
cannam@95 91
cannam@95 92 <p>If an <code>nembed</code> parameter is non-<code>NULL</code>, it is interpreted as
cannam@95 93 the physical size of the corresponding array, in row-major order, just
cannam@95 94 as for <code>fftw_plan_many_dft</code>. In this case, each dimension of
cannam@95 95 <code>nembed</code> should be <code>&gt;=</code> what it would be in the basic
cannam@95 96 interface (e.g. the halved or padded <code>n</code>).
cannam@95 97
cannam@95 98 <p>Arrays <code>n</code>, <code>inembed</code>, and <code>onembed</code> are not used after
cannam@95 99 this function returns. You can safely free or reuse them.
cannam@95 100
cannam@95 101 <!-- =========> -->
cannam@95 102 </body></html>
cannam@95 103