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Add FFTW 3.3.8 source, and a Linux build
author Chris Cannam <cannam@all-day-breakfast.com>
date Tue, 19 Nov 2019 14:52:55 +0000
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1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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3 <!-- This manual is for FFTW
4 (version 3.3.8, 24 May 2018).
5
6 Copyright (C) 2003 Matteo Frigo.
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8 Copyright (C) 2003 Massachusetts Institute of Technology.
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24 <head>
25 <title>FFTW 3.3.8: Other Multi-dimensional Real-data MPI Transforms</title>
26
27 <meta name="description" content="FFTW 3.3.8: Other Multi-dimensional Real-data MPI Transforms">
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34 <link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
35 <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
36 <link href="Distributed_002dmemory-FFTW-with-MPI.html#Distributed_002dmemory-FFTW-with-MPI" rel="up" title="Distributed-memory FFTW with MPI">
37 <link href="FFTW-MPI-Transposes.html#FFTW-MPI-Transposes" rel="next" title="FFTW MPI Transposes">
38 <link href="Multi_002ddimensional-MPI-DFTs-of-Real-Data.html#Multi_002ddimensional-MPI-DFTs-of-Real-Data" rel="prev" title="Multi-dimensional MPI DFTs of Real Data">
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70 <body lang="en">
71 <a name="Other-Multi_002ddimensional-Real_002ddata-MPI-Transforms"></a>
72 <div class="header">
73 <p>
74 Next: <a href="FFTW-MPI-Transposes.html#FFTW-MPI-Transposes" accesskey="n" rel="next">FFTW MPI Transposes</a>, Previous: <a href="Multi_002ddimensional-MPI-DFTs-of-Real-Data.html#Multi_002ddimensional-MPI-DFTs-of-Real-Data" accesskey="p" rel="prev">Multi-dimensional MPI DFTs of Real Data</a>, Up: <a href="Distributed_002dmemory-FFTW-with-MPI.html#Distributed_002dmemory-FFTW-with-MPI" accesskey="u" rel="up">Distributed-memory FFTW with MPI</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>
75 </div>
76 <hr>
77 <a name="Other-multi_002ddimensional-Real_002dData-MPI-Transforms"></a>
78 <h3 class="section">6.6 Other multi-dimensional Real-Data MPI Transforms</h3>
79
80 <a name="index-r2r-3"></a>
81 <p>FFTW&rsquo;s MPI interface also supports multi-dimensional &lsquo;<samp>r2r</samp>&rsquo;
82 transforms of all kinds supported by the serial interface
83 (e.g. discrete cosine and sine transforms, discrete Hartley
84 transforms, etc.). Only multi-dimensional &lsquo;<samp>r2r</samp>&rsquo; transforms, not
85 one-dimensional transforms, are currently parallelized.
86 </p>
87 <a name="index-fftw_005fr2r_005fkind-1"></a>
88 <p>These are used much like the multidimensional complex DFTs discussed
89 above, except that the data is real rather than complex, and one needs
90 to pass an r2r transform kind (<code>fftw_r2r_kind</code>) for each
91 dimension as in the serial FFTW (see <a href="More-DFTs-of-Real-Data.html#More-DFTs-of-Real-Data">More DFTs of Real Data</a>).
92 </p>
93 <p>For example, one might perform a two-dimensional L&nbsp;&times;&nbsp;M
94 that is
95 an REDFT10 (DCT-II) in the first dimension and an RODFT10 (DST-II) in
96 the second dimension with code like:
97 </p>
98 <div class="example">
99 <pre class="example"> const ptrdiff_t L = ..., M = ...;
100 fftw_plan plan;
101 double *data;
102 ptrdiff_t alloc_local, local_n0, local_0_start, i, j;
103
104 /* <span class="roman">get local data size and allocate</span> */
105 alloc_local = fftw_mpi_local_size_2d(L, M, MPI_COMM_WORLD,
106 &amp;local_n0, &amp;local_0_start);
107 data = fftw_alloc_real(alloc_local);
108
109 /* <span class="roman">create plan for in-place REDFT10 x RODFT10</span> */
110 plan = fftw_mpi_plan_r2r_2d(L, M, data, data, MPI_COMM_WORLD,
111 FFTW_REDFT10, FFTW_RODFT10, FFTW_MEASURE);
112
113 /* <span class="roman">initialize data to some function</span> my_function(x,y) */
114 for (i = 0; i &lt; local_n0; ++i) for (j = 0; j &lt; M; ++j)
115 data[i*M + j] = my_function(local_0_start + i, j);
116
117 /* <span class="roman">compute transforms, in-place, as many times as desired</span> */
118 fftw_execute(plan);
119
120 fftw_destroy_plan(plan);
121 </pre></div>
122
123 <a name="index-fftw_005falloc_005freal-3"></a>
124 <p>Notice that we use the same &lsquo;<samp>local_size</samp>&rsquo; functions as we did for
125 complex data, only now we interpret the sizes in terms of real rather
126 than complex values, and correspondingly use <code>fftw_alloc_real</code>.
127 </p>
128
129
130
131 </body>
132 </html>