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author Chris Cannam
date Wed, 07 Sep 2016 10:40:32 +0100
parents 26056e866c29
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Chris@19 1 <html lang="en">
Chris@19 2 <head>
Chris@19 3 <title>Guru Real-data DFTs - FFTW 3.3.4</title>
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Chris@19 8 <link rel="up" href="Guru-Interface.html#Guru-Interface" title="Guru Interface">
Chris@19 9 <link rel="prev" href="Guru-Complex-DFTs.html#Guru-Complex-DFTs" title="Guru Complex DFTs">
Chris@19 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@19 12 <!--
Chris@19 13 This manual is for FFTW
Chris@19 14 (version 3.3.4, 20 September 2013).
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Chris@19 46 </head>
Chris@19 47 <body>
Chris@19 48 <div class="node">
Chris@19 49 <a name="Guru-Real-data-DFTs"></a>
Chris@19 50 <a name="Guru-Real_002ddata-DFTs"></a>
Chris@19 51 <p>
Chris@19 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@19 53 Previous:&nbsp;<a rel="previous" accesskey="p" href="Guru-Complex-DFTs.html#Guru-Complex-DFTs">Guru Complex DFTs</a>,
Chris@19 54 Up:&nbsp;<a rel="up" accesskey="u" href="Guru-Interface.html#Guru-Interface">Guru Interface</a>
Chris@19 55 <hr>
Chris@19 56 </div>
Chris@19 57
Chris@19 58 <h4 class="subsection">4.5.4 Guru Real-data DFTs</h4>
Chris@19 59
Chris@19 60 <pre class="example"> fftw_plan fftw_plan_guru_dft_r2c(
Chris@19 61 int rank, const fftw_iodim *dims,
Chris@19 62 int howmany_rank, const fftw_iodim *howmany_dims,
Chris@19 63 double *in, fftw_complex *out,
Chris@19 64 unsigned flags);
Chris@19 65
Chris@19 66 fftw_plan fftw_plan_guru_split_dft_r2c(
Chris@19 67 int rank, const fftw_iodim *dims,
Chris@19 68 int howmany_rank, const fftw_iodim *howmany_dims,
Chris@19 69 double *in, double *ro, double *io,
Chris@19 70 unsigned flags);
Chris@19 71
Chris@19 72 fftw_plan fftw_plan_guru_dft_c2r(
Chris@19 73 int rank, const fftw_iodim *dims,
Chris@19 74 int howmany_rank, const fftw_iodim *howmany_dims,
Chris@19 75 fftw_complex *in, double *out,
Chris@19 76 unsigned flags);
Chris@19 77
Chris@19 78 fftw_plan fftw_plan_guru_split_dft_c2r(
Chris@19 79 int rank, const fftw_iodim *dims,
Chris@19 80 int howmany_rank, const fftw_iodim *howmany_dims,
Chris@19 81 double *ri, double *ii, double *out,
Chris@19 82 unsigned flags);
Chris@19 83 </pre>
Chris@19 84 <p><a name="index-fftw_005fplan_005fguru_005fdft_005fr2c-253"></a><a name="index-fftw_005fplan_005fguru_005fsplit_005fdft_005fr2c-254"></a><a name="index-fftw_005fplan_005fguru_005fdft_005fc2r-255"></a><a name="index-fftw_005fplan_005fguru_005fsplit_005fdft_005fc2r-256"></a>
Chris@19 85 Plan a real-input (r2c) or real-output (c2r), multi-dimensional DFT with
Chris@19 86 transform dimensions given by (<code>rank</code>, <code>dims</code>) over a
Chris@19 87 multi-dimensional vector (loop) of dimensions (<code>howmany_rank</code>,
Chris@19 88 <code>howmany_dims</code>). <code>dims</code> and <code>howmany_dims</code> should point
Chris@19 89 to <code>fftw_iodim</code> arrays of length <code>rank</code> and
Chris@19 90 <code>howmany_rank</code>, respectively. As for the basic and advanced
Chris@19 91 interfaces, an r2c transform is <code>FFTW_FORWARD</code> and a c2r transform
Chris@19 92 is <code>FFTW_BACKWARD</code>.
Chris@19 93
Chris@19 94 <p>The <em>last</em> dimension of <code>dims</code> is interpreted specially:
Chris@19 95 that dimension of the real array has size <code>dims[rank-1].n</code>, but
Chris@19 96 that dimension of the complex array has size <code>dims[rank-1].n/2+1</code>
Chris@19 97 (division rounded down). The strides, on the other hand, are taken to
Chris@19 98 be exactly as specified. It is up to the user to specify the strides
Chris@19 99 appropriately for the peculiar dimensions of the data, and we do not
Chris@19 100 guarantee that the planner will succeed (return non-<code>NULL</code>) for
Chris@19 101 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@19 102 for an in-place transform, each individual dimension should be able to
Chris@19 103 operate in place.)
Chris@19 104 <a name="index-in_002dplace-257"></a>
Chris@19 105
Chris@19 106 <p><code>in</code> and <code>out</code> point to the input and output arrays for r2c
Chris@19 107 and c2r transforms, respectively. For split arrays, <code>ri</code> and
Chris@19 108 <code>ii</code> point to the real and imaginary input arrays for a c2r
Chris@19 109 transform, and <code>ro</code> and <code>io</code> point to the real and imaginary
Chris@19 110 output arrays for an r2c transform. <code>in</code> and <code>ro</code> or
Chris@19 111 <code>ri</code> and <code>out</code> may be the same, indicating an in-place
Chris@19 112 transform. (In-place transforms where <code>in</code> and <code>io</code> or
Chris@19 113 <code>ii</code> and <code>out</code> are the same are not currently supported.)
Chris@19 114
Chris@19 115 <p><a name="index-flags-258"></a><code>flags</code> is a bitwise OR (&lsquo;<samp><span class="samp">|</span></samp>&rsquo;) of zero or more planner flags,
Chris@19 116 as defined in <a href="Planner-Flags.html#Planner-Flags">Planner Flags</a>.
Chris@19 117
Chris@19 118 <p>In-place transforms of rank greater than 1 are currently only
Chris@19 119 supported for interleaved arrays. For split arrays, the planner will
Chris@19 120 return <code>NULL</code>.
Chris@19 121 <a name="index-in_002dplace-259"></a>
Chris@19 122 <!-- =========> -->
Chris@19 123
Chris@19 124 </body></html>
Chris@19 125