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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 7867fa7e1b6b
children
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cannam@127 3 <!-- This manual is for FFTW
cannam@127 4 (version 3.3.5, 30 July 2016).
cannam@127 5
cannam@127 6 Copyright (C) 2003 Matteo Frigo.
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cannam@127 8 Copyright (C) 2003 Massachusetts Institute of Technology.
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cannam@127 24 <head>
cannam@127 25 <title>FFTW 3.3.5: Other Multi-dimensional Real-data MPI Transforms</title>
cannam@127 26
cannam@127 27 <meta name="description" content="FFTW 3.3.5: Other Multi-dimensional Real-data MPI Transforms">
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cannam@127 36 <link href="Distributed_002dmemory-FFTW-with-MPI.html#Distributed_002dmemory-FFTW-with-MPI" rel="up" title="Distributed-memory FFTW with MPI">
cannam@127 37 <link href="FFTW-MPI-Transposes.html#FFTW-MPI-Transposes" rel="next" title="FFTW MPI Transposes">
cannam@127 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@127 69 </head>
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cannam@127 71 <body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
cannam@127 72 <a name="Other-Multi_002ddimensional-Real_002ddata-MPI-Transforms"></a>
cannam@127 73 <div class="header">
cannam@127 74 <p>
cannam@127 75 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@127 76 </div>
cannam@127 77 <hr>
cannam@127 78 <a name="Other-multi_002ddimensional-Real_002dData-MPI-Transforms"></a>
cannam@127 79 <h3 class="section">6.6 Other multi-dimensional Real-Data MPI Transforms</h3>
cannam@127 80
cannam@127 81 <a name="index-r2r-3"></a>
cannam@127 82 <p>FFTW&rsquo;s MPI interface also supports multi-dimensional &lsquo;<samp>r2r</samp>&rsquo;
cannam@127 83 transforms of all kinds supported by the serial interface
cannam@127 84 (e.g. discrete cosine and sine transforms, discrete Hartley
cannam@127 85 transforms, etc.). Only multi-dimensional &lsquo;<samp>r2r</samp>&rsquo; transforms, not
cannam@127 86 one-dimensional transforms, are currently parallelized.
cannam@127 87 </p>
cannam@127 88 <a name="index-fftw_005fr2r_005fkind-1"></a>
cannam@127 89 <p>These are used much like the multidimensional complex DFTs discussed
cannam@127 90 above, except that the data is real rather than complex, and one needs
cannam@127 91 to pass an r2r transform kind (<code>fftw_r2r_kind</code>) for each
cannam@127 92 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@127 93 </p>
cannam@127 94 <p>For example, one might perform a two-dimensional L&nbsp;&times;&nbsp;M that is
cannam@127 95 an REDFT10 (DCT-II) in the first dimension and an RODFT10 (DST-II) in
cannam@127 96 the second dimension with code like:
cannam@127 97 </p>
cannam@127 98 <div class="example">
cannam@127 99 <pre class="example"> const ptrdiff_t L = ..., M = ...;
cannam@127 100 fftw_plan plan;
cannam@127 101 double *data;
cannam@127 102 ptrdiff_t alloc_local, local_n0, local_0_start, i, j;
cannam@127 103
cannam@127 104 /* <span class="roman">get local data size and allocate</span> */
cannam@127 105 alloc_local = fftw_mpi_local_size_2d(L, M, MPI_COMM_WORLD,
cannam@127 106 &amp;local_n0, &amp;local_0_start);
cannam@127 107 data = fftw_alloc_real(alloc_local);
cannam@127 108
cannam@127 109 /* <span class="roman">create plan for in-place REDFT10 x RODFT10</span> */
cannam@127 110 plan = fftw_mpi_plan_r2r_2d(L, M, data, data, MPI_COMM_WORLD,
cannam@127 111 FFTW_REDFT10, FFTW_RODFT10, FFTW_MEASURE);
cannam@127 112
cannam@127 113 /* <span class="roman">initialize data to some function</span> my_function(x,y) */
cannam@127 114 for (i = 0; i &lt; local_n0; ++i) for (j = 0; j &lt; M; ++j)
cannam@127 115 data[i*M + j] = my_function(local_0_start + i, j);
cannam@127 116
cannam@127 117 /* <span class="roman">compute transforms, in-place, as many times as desired</span> */
cannam@127 118 fftw_execute(plan);
cannam@127 119
cannam@127 120 fftw_destroy_plan(plan);
cannam@127 121 </pre></div>
cannam@127 122
cannam@127 123 <a name="index-fftw_005falloc_005freal-3"></a>
cannam@127 124 <p>Notice that we use the same &lsquo;<samp>local_size</samp>&rsquo; functions as we did for
cannam@127 125 complex data, only now we interpret the sizes in terms of real rather
cannam@127 126 than complex values, and correspondingly use <code>fftw_alloc_real</code>.
cannam@127 127 </p>
cannam@127 128
cannam@127 129
cannam@127 130
cannam@127 131 </body>
cannam@127 132 </html>