|
d@0
|
1 <html lang="en">
|
|
d@0
|
2 <head>
|
|
d@0
|
3 <title>Advanced Complex DFTs - FFTW 3.2.1</title>
|
|
d@0
|
4 <meta http-equiv="Content-Type" content="text/html">
|
|
d@0
|
5 <meta name="description" content="FFTW 3.2.1">
|
|
d@0
|
6 <meta name="generator" content="makeinfo 4.8">
|
|
d@0
|
7 <link title="Top" rel="start" href="index.html#Top">
|
|
d@0
|
8 <link rel="up" href="Advanced-Interface.html#Advanced-Interface" title="Advanced Interface">
|
|
d@0
|
9 <link rel="prev" href="Advanced-Interface.html#Advanced-Interface" title="Advanced Interface">
|
|
d@0
|
10 <link rel="next" href="Advanced-Real_002ddata-DFTs.html#Advanced-Real_002ddata-DFTs" title="Advanced Real-data DFTs">
|
|
d@0
|
11 <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
|
|
d@0
|
12 <!--
|
|
d@0
|
13 This manual is for FFTW
|
|
d@0
|
14 (version 3.2.1, 5 February 2009).
|
|
d@0
|
15
|
|
d@0
|
16 Copyright (C) 2003 Matteo Frigo.
|
|
d@0
|
17
|
|
d@0
|
18 Copyright (C) 2003 Massachusetts Institute of Technology.
|
|
d@0
|
19
|
|
d@0
|
20 Permission is granted to make and distribute verbatim copies of
|
|
d@0
|
21 this manual provided the copyright notice and this permission
|
|
d@0
|
22 notice are preserved on all copies.
|
|
d@0
|
23
|
|
d@0
|
24 Permission is granted to copy and distribute modified versions of
|
|
d@0
|
25 this manual under the conditions for verbatim copying, provided
|
|
d@0
|
26 that the entire resulting derived work is distributed under the
|
|
d@0
|
27 terms of a permission notice identical to this one.
|
|
d@0
|
28
|
|
d@0
|
29 Permission is granted to copy and distribute translations of this
|
|
d@0
|
30 manual into another language, under the above conditions for
|
|
d@0
|
31 modified versions, except that this permission notice may be
|
|
d@0
|
32 stated in a translation approved by the Free Software Foundation.
|
|
d@0
|
33 -->
|
|
d@0
|
34 <meta http-equiv="Content-Style-Type" content="text/css">
|
|
d@0
|
35 <style type="text/css"><!--
|
|
d@0
|
36 pre.display { font-family:inherit }
|
|
d@0
|
37 pre.format { font-family:inherit }
|
|
d@0
|
38 pre.smalldisplay { font-family:inherit; font-size:smaller }
|
|
d@0
|
39 pre.smallformat { font-family:inherit; font-size:smaller }
|
|
d@0
|
40 pre.smallexample { font-size:smaller }
|
|
d@0
|
41 pre.smalllisp { font-size:smaller }
|
|
d@0
|
42 span.sc { font-variant:small-caps }
|
|
d@0
|
43 span.roman { font-family:serif; font-weight:normal; }
|
|
d@0
|
44 span.sansserif { font-family:sans-serif; font-weight:normal; }
|
|
d@0
|
45 --></style>
|
|
d@0
|
46 </head>
|
|
d@0
|
47 <body>
|
|
d@0
|
48 <div class="node">
|
|
d@0
|
49 <p>
|
|
d@0
|
50 <a name="Advanced-Complex-DFTs"></a>
|
|
d@0
|
51 Next: <a rel="next" accesskey="n" href="Advanced-Real_002ddata-DFTs.html#Advanced-Real_002ddata-DFTs">Advanced Real-data DFTs</a>,
|
|
d@0
|
52 Previous: <a rel="previous" accesskey="p" href="Advanced-Interface.html#Advanced-Interface">Advanced Interface</a>,
|
|
d@0
|
53 Up: <a rel="up" accesskey="u" href="Advanced-Interface.html#Advanced-Interface">Advanced Interface</a>
|
|
d@0
|
54 <hr>
|
|
d@0
|
55 </div>
|
|
d@0
|
56
|
|
d@0
|
57 <h4 class="subsection">4.4.1 Advanced Complex DFTs</h4>
|
|
d@0
|
58
|
|
d@0
|
59 <pre class="example"> fftw_plan fftw_plan_many_dft(int rank, const int *n, int howmany,
|
|
d@0
|
60 fftw_complex *in, const int *inembed,
|
|
d@0
|
61 int istride, int idist,
|
|
d@0
|
62 fftw_complex *out, const int *onembed,
|
|
d@0
|
63 int ostride, int odist,
|
|
d@0
|
64 int sign, unsigned flags);
|
|
d@0
|
65 </pre>
|
|
d@0
|
66 <p><a name="index-fftw_005fplan_005fmany_005fdft-223"></a>
|
|
d@0
|
67 This plans multidimensional complex DFTs, and is exactly the same as
|
|
d@0
|
68 <code>fftw_plan_dft</code> except for the new parameters <code>howmany</code>,
|
|
d@0
|
69 {<code>i</code>,<code>o</code>}<code>nembed</code>, {<code>i</code>,<code>o</code>}<code>stride</code>,
|
|
d@0
|
70 and {<code>i</code>,<code>o</code>}<code>dist</code>.
|
|
d@0
|
71
|
|
d@0
|
72 <p><code>howmany</code> is the number of transforms to compute, where the
|
|
d@0
|
73 <code>k</code>-th transform is of the arrays starting at <code>in+k*idist</code> and
|
|
d@0
|
74 <code>out+k*odist</code>. The resulting plans can often be faster than
|
|
d@0
|
75 calling FFTW multiple times for the individual transforms. The basic
|
|
d@0
|
76 <code>fftw_plan_dft</code> interface corresponds to <code>howmany=1</code> (in which
|
|
d@0
|
77 case the <code>dist</code> parameters are ignored).
|
|
d@0
|
78 <a name="index-howmany-parameter-224"></a><a name="index-dist-225"></a>
|
|
d@0
|
79 The two <code>nembed</code> parameters (which should be arrays of length
|
|
d@0
|
80 <code>rank</code>) indicate the sizes of the input and output array
|
|
d@0
|
81 dimensions, respectively, where the transform is of a subarray of size
|
|
d@0
|
82 <code>n</code>. (Each dimension of <code>n</code> should be <code><=</code> the
|
|
d@0
|
83 corresponding dimension of the <code>nembed</code> arrays.) That is, the
|
|
d@0
|
84 input and output arrays are stored in row-major order with size given by
|
|
d@0
|
85 <code>nembed</code> (not counting the strides and howmany multiplicities).
|
|
d@0
|
86 Passing <code>NULL</code> for an <code>nembed</code> parameter is equivalent to
|
|
d@0
|
87 passing <code>n</code> (i.e. same physical and logical dimensions, as in the
|
|
d@0
|
88 basic interface.)
|
|
d@0
|
89
|
|
d@0
|
90 <p>The <code>stride</code> parameters indicate that the <code>j</code>-th element of
|
|
d@0
|
91 the input or output arrays is located at <code>j*istride</code> or
|
|
d@0
|
92 <code>j*ostride</code>, respectively. (For a multi-dimensional array,
|
|
d@0
|
93 <code>j</code> is the ordinary row-major index.) When combined with the
|
|
d@0
|
94 <code>k</code>-th transform in a <code>howmany</code> loop, from above, this means
|
|
d@0
|
95 that the (<code>j</code>,<code>k</code>)-th element is at <code>j*stride+k*dist</code>.
|
|
d@0
|
96 (The basic <code>fftw_plan_dft</code> interface corresponds to a stride of 1.)
|
|
d@0
|
97 <a name="index-stride-226"></a>
|
|
d@0
|
98 For in-place transforms, the input and output <code>stride</code> and
|
|
d@0
|
99 <code>dist</code> parameters should be the same; otherwise, the planner may
|
|
d@0
|
100 return <code>NULL</code>.
|
|
d@0
|
101
|
|
d@0
|
102 <p>Arrays <code>n</code>, <code>inembed</code>, and <code>onembed</code> are not used after
|
|
d@0
|
103 this function returns. You can safely free or reuse them.
|
|
d@0
|
104
|
|
d@0
|
105 <p>So, for example, to transform a sequence of contiguous arrays, stored
|
|
d@0
|
106 one after another, one would use a <code>stride</code> of 1 and a <code>dist</code>
|
|
d@0
|
107 of N, where N is the product of the dimensions. In
|
|
d@0
|
108 another example, to transform an array of contiguous “vectors” of
|
|
d@0
|
109 length M, one would use a <code>howmany</code> of M, a
|
|
d@0
|
110 <code>stride</code> of M, and a <code>dist</code> of 1.
|
|
d@0
|
111 <a name="index-vector-227"></a>
|
|
d@0
|
112 <!-- =========> -->
|
|
d@0
|
113
|
|
d@0
|
114 </body></html>
|
|
d@0
|
115
|
