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Replace these with versions built using an older toolset (so as to avoid ABI compatibilities when linking on Ubuntu 14.04 for packaging purposes)
author Chris Cannam
date Fri, 07 Feb 2020 11:51:13 +0000
parents 37bf6b4a2645
children
rev   line source
Chris@10 1 <html lang="en">
Chris@10 2 <head>
Chris@10 3 <title>Guru Real-data DFTs - FFTW 3.3.3</title>
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Chris@10 9 <link rel="prev" href="Guru-Complex-DFTs.html#Guru-Complex-DFTs" title="Guru Complex DFTs">
Chris@10 10 <link rel="next" href="Guru-Real_002dto_002dreal-Transforms.html#Guru-Real_002dto_002dreal-Transforms" title="Guru Real-to-real Transforms">
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Chris@10 12 <!--
Chris@10 13 This manual is for FFTW
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Chris@10 48 <div class="node">
Chris@10 49 <a name="Guru-Real-data-DFTs"></a>
Chris@10 50 <a name="Guru-Real_002ddata-DFTs"></a>
Chris@10 51 <p>
Chris@10 52 Next:&nbsp;<a rel="next" accesskey="n" href="Guru-Real_002dto_002dreal-Transforms.html#Guru-Real_002dto_002dreal-Transforms">Guru Real-to-real Transforms</a>,
Chris@10 53 Previous:&nbsp;<a rel="previous" accesskey="p" href="Guru-Complex-DFTs.html#Guru-Complex-DFTs">Guru Complex DFTs</a>,
Chris@10 54 Up:&nbsp;<a rel="up" accesskey="u" href="Guru-Interface.html#Guru-Interface">Guru Interface</a>
Chris@10 55 <hr>
Chris@10 56 </div>
Chris@10 57
Chris@10 58 <h4 class="subsection">4.5.4 Guru Real-data DFTs</h4>
Chris@10 59
Chris@10 60 <pre class="example"> fftw_plan fftw_plan_guru_dft_r2c(
Chris@10 61 int rank, const fftw_iodim *dims,
Chris@10 62 int howmany_rank, const fftw_iodim *howmany_dims,
Chris@10 63 double *in, fftw_complex *out,
Chris@10 64 unsigned flags);
Chris@10 65
Chris@10 66 fftw_plan fftw_plan_guru_split_dft_r2c(
Chris@10 67 int rank, const fftw_iodim *dims,
Chris@10 68 int howmany_rank, const fftw_iodim *howmany_dims,
Chris@10 69 double *in, double *ro, double *io,
Chris@10 70 unsigned flags);
Chris@10 71
Chris@10 72 fftw_plan fftw_plan_guru_dft_c2r(
Chris@10 73 int rank, const fftw_iodim *dims,
Chris@10 74 int howmany_rank, const fftw_iodim *howmany_dims,
Chris@10 75 fftw_complex *in, double *out,
Chris@10 76 unsigned flags);
Chris@10 77
Chris@10 78 fftw_plan fftw_plan_guru_split_dft_c2r(
Chris@10 79 int rank, const fftw_iodim *dims,
Chris@10 80 int howmany_rank, const fftw_iodim *howmany_dims,
Chris@10 81 double *ri, double *ii, double *out,
Chris@10 82 unsigned flags);
Chris@10 83 </pre>
Chris@10 84 <p><a name="index-fftw_005fplan_005fguru_005fdft_005fr2c-251"></a><a name="index-fftw_005fplan_005fguru_005fsplit_005fdft_005fr2c-252"></a><a name="index-fftw_005fplan_005fguru_005fdft_005fc2r-253"></a><a name="index-fftw_005fplan_005fguru_005fsplit_005fdft_005fc2r-254"></a>
Chris@10 85 Plan a real-input (r2c) or real-output (c2r), multi-dimensional DFT with
Chris@10 86 transform dimensions given by (<code>rank</code>, <code>dims</code>) over a
Chris@10 87 multi-dimensional vector (loop) of dimensions (<code>howmany_rank</code>,
Chris@10 88 <code>howmany_dims</code>). <code>dims</code> and <code>howmany_dims</code> should point
Chris@10 89 to <code>fftw_iodim</code> arrays of length <code>rank</code> and
Chris@10 90 <code>howmany_rank</code>, respectively. As for the basic and advanced
Chris@10 91 interfaces, an r2c transform is <code>FFTW_FORWARD</code> and a c2r transform
Chris@10 92 is <code>FFTW_BACKWARD</code>.
Chris@10 93
Chris@10 94 <p>The <em>last</em> dimension of <code>dims</code> is interpreted specially:
Chris@10 95 that dimension of the real array has size <code>dims[rank-1].n</code>, but
Chris@10 96 that dimension of the complex array has size <code>dims[rank-1].n/2+1</code>
Chris@10 97 (division rounded down). The strides, on the other hand, are taken to
Chris@10 98 be exactly as specified. It is up to the user to specify the strides
Chris@10 99 appropriately for the peculiar dimensions of the data, and we do not
Chris@10 100 guarantee that the planner will succeed (return non-<code>NULL</code>) for
Chris@10 101 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,
Chris@10 102 for an in-place transform, each individual dimension should be able to
Chris@10 103 operate in place.)
Chris@10 104 <a name="index-in_002dplace-255"></a>
Chris@10 105
Chris@10 106 <p><code>in</code> and <code>out</code> point to the input and output arrays for r2c
Chris@10 107 and c2r transforms, respectively. For split arrays, <code>ri</code> and
Chris@10 108 <code>ii</code> point to the real and imaginary input arrays for a c2r
Chris@10 109 transform, and <code>ro</code> and <code>io</code> point to the real and imaginary
Chris@10 110 output arrays for an r2c transform. <code>in</code> and <code>ro</code> or
Chris@10 111 <code>ri</code> and <code>out</code> may be the same, indicating an in-place
Chris@10 112 transform. (In-place transforms where <code>in</code> and <code>io</code> or
Chris@10 113 <code>ii</code> and <code>out</code> are the same are not currently supported.)
Chris@10 114
Chris@10 115 <p><a name="index-flags-256"></a><code>flags</code> is a bitwise OR (&lsquo;<samp><span class="samp">|</span></samp>&rsquo;) of zero or more planner flags,
Chris@10 116 as defined in <a href="Planner-Flags.html#Planner-Flags">Planner Flags</a>.
Chris@10 117
Chris@10 118 <p>In-place transforms of rank greater than 1 are currently only
Chris@10 119 supported for interleaved arrays. For split arrays, the planner will
Chris@10 120 return <code>NULL</code>.
Chris@10 121 <a name="index-in_002dplace-257"></a>
Chris@10 122 <!-- =========> -->
Chris@10 123
Chris@10 124 </body></html>
Chris@10 125