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Add null config files
author Chris Cannam <cannam@all-day-breakfast.com>
date Mon, 02 Mar 2020 14:03:47 +0000
parents bd3cc4d1df30
children
rev   line source
cannam@167 1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
cannam@167 2 <html>
cannam@167 3 <!-- This manual is for FFTW
cannam@167 4 (version 3.3.8, 24 May 2018).
cannam@167 5
cannam@167 6 Copyright (C) 2003 Matteo Frigo.
cannam@167 7
cannam@167 8 Copyright (C) 2003 Massachusetts Institute of Technology.
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cannam@167 10 Permission is granted to make and distribute verbatim copies of this
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cannam@167 24 <head>
cannam@167 25 <title>FFTW 3.3.8: Other Multi-dimensional Real-data MPI Transforms</title>
cannam@167 26
cannam@167 27 <meta name="description" content="FFTW 3.3.8: Other Multi-dimensional Real-data MPI Transforms">
cannam@167 28 <meta name="keywords" content="FFTW 3.3.8: Other Multi-dimensional Real-data MPI Transforms">
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cannam@167 35 <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
cannam@167 36 <link href="Distributed_002dmemory-FFTW-with-MPI.html#Distributed_002dmemory-FFTW-with-MPI" rel="up" title="Distributed-memory FFTW with MPI">
cannam@167 37 <link href="FFTW-MPI-Transposes.html#FFTW-MPI-Transposes" rel="next" title="FFTW MPI Transposes">
cannam@167 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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cannam@167 68 </head>
cannam@167 69
cannam@167 70 <body lang="en">
cannam@167 71 <a name="Other-Multi_002ddimensional-Real_002ddata-MPI-Transforms"></a>
cannam@167 72 <div class="header">
cannam@167 73 <p>
cannam@167 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>
cannam@167 75 </div>
cannam@167 76 <hr>
cannam@167 77 <a name="Other-multi_002ddimensional-Real_002dData-MPI-Transforms"></a>
cannam@167 78 <h3 class="section">6.6 Other multi-dimensional Real-Data MPI Transforms</h3>
cannam@167 79
cannam@167 80 <a name="index-r2r-3"></a>
cannam@167 81 <p>FFTW&rsquo;s MPI interface also supports multi-dimensional &lsquo;<samp>r2r</samp>&rsquo;
cannam@167 82 transforms of all kinds supported by the serial interface
cannam@167 83 (e.g. discrete cosine and sine transforms, discrete Hartley
cannam@167 84 transforms, etc.). Only multi-dimensional &lsquo;<samp>r2r</samp>&rsquo; transforms, not
cannam@167 85 one-dimensional transforms, are currently parallelized.
cannam@167 86 </p>
cannam@167 87 <a name="index-fftw_005fr2r_005fkind-1"></a>
cannam@167 88 <p>These are used much like the multidimensional complex DFTs discussed
cannam@167 89 above, except that the data is real rather than complex, and one needs
cannam@167 90 to pass an r2r transform kind (<code>fftw_r2r_kind</code>) for each
cannam@167 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>).
cannam@167 92 </p>
cannam@167 93 <p>For example, one might perform a two-dimensional L&nbsp;&times;&nbsp;M
cannam@167 94 that is
cannam@167 95 an REDFT10 (DCT-II) in the first dimension and an RODFT10 (DST-II) in
cannam@167 96 the second dimension with code like:
cannam@167 97 </p>
cannam@167 98 <div class="example">
cannam@167 99 <pre class="example"> const ptrdiff_t L = ..., M = ...;
cannam@167 100 fftw_plan plan;
cannam@167 101 double *data;
cannam@167 102 ptrdiff_t alloc_local, local_n0, local_0_start, i, j;
cannam@167 103
cannam@167 104 /* <span class="roman">get local data size and allocate</span> */
cannam@167 105 alloc_local = fftw_mpi_local_size_2d(L, M, MPI_COMM_WORLD,
cannam@167 106 &amp;local_n0, &amp;local_0_start);
cannam@167 107 data = fftw_alloc_real(alloc_local);
cannam@167 108
cannam@167 109 /* <span class="roman">create plan for in-place REDFT10 x RODFT10</span> */
cannam@167 110 plan = fftw_mpi_plan_r2r_2d(L, M, data, data, MPI_COMM_WORLD,
cannam@167 111 FFTW_REDFT10, FFTW_RODFT10, FFTW_MEASURE);
cannam@167 112
cannam@167 113 /* <span class="roman">initialize data to some function</span> my_function(x,y) */
cannam@167 114 for (i = 0; i &lt; local_n0; ++i) for (j = 0; j &lt; M; ++j)
cannam@167 115 data[i*M + j] = my_function(local_0_start + i, j);
cannam@167 116
cannam@167 117 /* <span class="roman">compute transforms, in-place, as many times as desired</span> */
cannam@167 118 fftw_execute(plan);
cannam@167 119
cannam@167 120 fftw_destroy_plan(plan);
cannam@167 121 </pre></div>
cannam@167 122
cannam@167 123 <a name="index-fftw_005falloc_005freal-3"></a>
cannam@167 124 <p>Notice that we use the same &lsquo;<samp>local_size</samp>&rsquo; functions as we did for
cannam@167 125 complex data, only now we interpret the sizes in terms of real rather
cannam@167 126 than complex values, and correspondingly use <code>fftw_alloc_real</code>.
cannam@167 127 </p>
cannam@167 128
cannam@167 129
cannam@167 130
cannam@167 131 </body>
cannam@167 132 </html>