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1 <html lang="en">
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2 <head>
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3 <title>Guru Real-data DFTs - FFTW 3.3.3</title>
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4 <meta http-equiv="Content-Type" content="text/html">
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5 <meta name="description" content="FFTW 3.3.3">
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6 <meta name="generator" content="makeinfo 4.13">
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7 <link title="Top" rel="start" href="index.html#Top">
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8 <link rel="up" href="Guru-Interface.html#Guru-Interface" title="Guru Interface">
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9 <link rel="prev" href="Guru-Complex-DFTs.html#Guru-Complex-DFTs" title="Guru Complex DFTs">
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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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11 <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
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12 <!--
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13 This manual is for FFTW
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14 (version 3.3.3, 25 November 2012).
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15
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16 Copyright (C) 2003 Matteo Frigo.
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17
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18 Copyright (C) 2003 Massachusetts Institute of Technology.
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19
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20 Permission is granted to make and distribute verbatim copies of
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21 this manual provided the copyright notice and this permission
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22 notice are preserved on all copies.
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23
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24 Permission is granted to copy and distribute modified versions of
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25 this manual under the conditions for verbatim copying, provided
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26 that the entire resulting derived work is distributed under the
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27 terms of a permission notice identical to this one.
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28
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29 Permission is granted to copy and distribute translations of this
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30 manual into another language, under the above conditions for
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31 modified versions, except that this permission notice may be
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32 stated in a translation approved by the Free Software Foundation.
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33 -->
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34 <meta http-equiv="Content-Style-Type" content="text/css">
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35 <style type="text/css"><!--
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44 span.sansserif { font-family:sans-serif; font-weight:normal; }
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45 --></style>
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46 </head>
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47 <body>
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48 <div class="node">
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49 <a name="Guru-Real-data-DFTs"></a>
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50 <a name="Guru-Real_002ddata-DFTs"></a>
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51 <p>
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52 Next: <a rel="next" accesskey="n" href="Guru-Real_002dto_002dreal-Transforms.html#Guru-Real_002dto_002dreal-Transforms">Guru Real-to-real Transforms</a>,
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53 Previous: <a rel="previous" accesskey="p" href="Guru-Complex-DFTs.html#Guru-Complex-DFTs">Guru Complex DFTs</a>,
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54 Up: <a rel="up" accesskey="u" href="Guru-Interface.html#Guru-Interface">Guru Interface</a>
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55 <hr>
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56 </div>
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57
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58 <h4 class="subsection">4.5.4 Guru Real-data DFTs</h4>
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59
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60 <pre class="example"> fftw_plan fftw_plan_guru_dft_r2c(
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61 int rank, const fftw_iodim *dims,
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62 int howmany_rank, const fftw_iodim *howmany_dims,
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63 double *in, fftw_complex *out,
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64 unsigned flags);
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65
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66 fftw_plan fftw_plan_guru_split_dft_r2c(
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67 int rank, const fftw_iodim *dims,
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68 int howmany_rank, const fftw_iodim *howmany_dims,
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69 double *in, double *ro, double *io,
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70 unsigned flags);
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71
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72 fftw_plan fftw_plan_guru_dft_c2r(
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73 int rank, const fftw_iodim *dims,
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74 int howmany_rank, const fftw_iodim *howmany_dims,
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75 fftw_complex *in, double *out,
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76 unsigned flags);
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77
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78 fftw_plan fftw_plan_guru_split_dft_c2r(
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79 int rank, const fftw_iodim *dims,
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80 int howmany_rank, const fftw_iodim *howmany_dims,
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81 double *ri, double *ii, double *out,
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82 unsigned flags);
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83 </pre>
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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>
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85 Plan a real-input (r2c) or real-output (c2r), multi-dimensional DFT with
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86 transform dimensions given by (<code>rank</code>, <code>dims</code>) over a
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87 multi-dimensional vector (loop) of dimensions (<code>howmany_rank</code>,
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88 <code>howmany_dims</code>). <code>dims</code> and <code>howmany_dims</code> should point
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89 to <code>fftw_iodim</code> arrays of length <code>rank</code> and
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90 <code>howmany_rank</code>, respectively. As for the basic and advanced
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91 interfaces, an r2c transform is <code>FFTW_FORWARD</code> and a c2r transform
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92 is <code>FFTW_BACKWARD</code>.
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93
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94 <p>The <em>last</em> dimension of <code>dims</code> is interpreted specially:
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95 that dimension of the real array has size <code>dims[rank-1].n</code>, but
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96 that dimension of the complex array has size <code>dims[rank-1].n/2+1</code>
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97 (division rounded down). The strides, on the other hand, are taken to
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98 be exactly as specified. It is up to the user to specify the strides
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99 appropriately for the peculiar dimensions of the data, and we do not
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100 guarantee that the planner will succeed (return non-<code>NULL</code>) for
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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,
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102 for an in-place transform, each individual dimension should be able to
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103 operate in place.)
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104 <a name="index-in_002dplace-255"></a>
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105
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106 <p><code>in</code> and <code>out</code> point to the input and output arrays for r2c
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107 and c2r transforms, respectively. For split arrays, <code>ri</code> and
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108 <code>ii</code> point to the real and imaginary input arrays for a c2r
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109 transform, and <code>ro</code> and <code>io</code> point to the real and imaginary
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110 output arrays for an r2c transform. <code>in</code> and <code>ro</code> or
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111 <code>ri</code> and <code>out</code> may be the same, indicating an in-place
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112 transform. (In-place transforms where <code>in</code> and <code>io</code> or
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113 <code>ii</code> and <code>out</code> are the same are not currently supported.)
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114
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115 <p><a name="index-flags-256"></a><code>flags</code> is a bitwise OR (‘<samp><span class="samp">|</span></samp>’) of zero or more planner flags,
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116 as defined in <a href="Planner-Flags.html#Planner-Flags">Planner Flags</a>.
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117
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118 <p>In-place transforms of rank greater than 1 are currently only
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119 supported for interleaved arrays. For split arrays, the planner will
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120 return <code>NULL</code>.
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121 <a name="index-in_002dplace-257"></a>
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122 <!-- =========> -->
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123
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124 </body></html>
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125
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