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Current fftw source
author Chris Cannam <cannam@all-day-breakfast.com>
date Tue, 18 Oct 2016 13:40:26 +0100
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72 <a name="Advanced-Real_002ddata-DFTs"></a>
73 <div class="header">
74 <p>
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>
76 </div>
77 <hr>
78 <a name="Advanced-Real_002ddata-DFTs-1"></a>
79 <h4 class="subsection">4.4.2 Advanced Real-data DFTs</h4>
80
81 <div class="example">
82 <pre class="example">fftw_plan fftw_plan_many_dft_r2c(int rank, const int *n, int howmany,
83 double *in, const int *inembed,
84 int istride, int idist,
85 fftw_complex *out, const int *onembed,
86 int ostride, int odist,
87 unsigned flags);
88 fftw_plan fftw_plan_many_dft_c2r(int rank, const int *n, int howmany,
89 fftw_complex *in, const int *inembed,
90 int istride, int idist,
91 double *out, const int *onembed,
92 int ostride, int odist,
93 unsigned flags);
94 </pre></div>
95 <a name="index-fftw_005fplan_005fmany_005fdft_005fr2c"></a>
96 <a name="index-fftw_005fplan_005fmany_005fdft_005fc2r"></a>
97
98 <p>Like <code>fftw_plan_many_dft</code>, these two functions add <code>howmany</code>,
99 <code>nembed</code>, <code>stride</code>, and <code>dist</code> parameters to the
100 <code>fftw_plan_dft_r2c</code> and <code>fftw_plan_dft_c2r</code> functions, but
101 otherwise behave the same as the basic interface.
102 </p>
103 <p>The interpretation of <code>howmany</code>, <code>stride</code>, and <code>dist</code> are
104 the same as for <code>fftw_plan_many_dft</code>, above. Note that the
105 <code>stride</code> and <code>dist</code> for the real array are in units of
106 <code>double</code>, and for the complex array are in units of
107 <code>fftw_complex</code>.
108 </p>
109 <p>If an <code>nembed</code> parameter is <code>NULL</code>, it is interpreted as what
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
111 the same as <code>n</code>, but with the last dimension cut roughly in half.
112 For the real array, the size is assumed to be <code>n</code> if the transform
113 is out-of-place, or <code>n</code> with the last dimension &ldquo;padded&rdquo; if the
114 transform is in-place.
115 </p>
116 <p>If an <code>nembed</code> parameter is non-<code>NULL</code>, it is interpreted as
117 the physical size of the corresponding array, in row-major order, just
118 as for <code>fftw_plan_many_dft</code>. In this case, each dimension of
119 <code>nembed</code> should be <code>&gt;=</code> what it would be in the basic
120 interface (e.g. the halved or padded <code>n</code>).
121 </p>
122 <p>Arrays <code>n</code>, <code>inembed</code>, and <code>onembed</code> are not used after
123 this function returns. You can safely free or reuse them.
124 </p>
125 <hr>
126 <div class="header">
127 <p>
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>
129 </div>
130
131
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