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Replace these with versions built using an older toolset (so as to avoid ABI compatibilities when linking on Ubuntu 14.04 for packaging purposes)
author Chris Cannam
date Fri, 07 Feb 2020 11:51:13 +0000
parents d0c2a83c1364
children
rev   line source
Chris@82 1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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Chris@82 3 <!-- This manual is for FFTW
Chris@82 4 (version 3.3.8, 24 May 2018).
Chris@82 5
Chris@82 6 Copyright (C) 2003 Matteo Frigo.
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Chris@82 8 Copyright (C) 2003 Massachusetts Institute of Technology.
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Chris@82 24 <head>
Chris@82 25 <title>FFTW 3.3.8: Other Multi-dimensional Real-data MPI Transforms</title>
Chris@82 26
Chris@82 27 <meta name="description" content="FFTW 3.3.8: Other Multi-dimensional Real-data MPI Transforms">
Chris@82 28 <meta name="keywords" content="FFTW 3.3.8: Other Multi-dimensional Real-data MPI Transforms">
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Chris@82 34 <link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
Chris@82 35 <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
Chris@82 36 <link href="Distributed_002dmemory-FFTW-with-MPI.html#Distributed_002dmemory-FFTW-with-MPI" rel="up" title="Distributed-memory FFTW with MPI">
Chris@82 37 <link href="FFTW-MPI-Transposes.html#FFTW-MPI-Transposes" rel="next" title="FFTW MPI Transposes">
Chris@82 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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Chris@82 66
Chris@82 67
Chris@82 68 </head>
Chris@82 69
Chris@82 70 <body lang="en">
Chris@82 71 <a name="Other-Multi_002ddimensional-Real_002ddata-MPI-Transforms"></a>
Chris@82 72 <div class="header">
Chris@82 73 <p>
Chris@82 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>
Chris@82 75 </div>
Chris@82 76 <hr>
Chris@82 77 <a name="Other-multi_002ddimensional-Real_002dData-MPI-Transforms"></a>
Chris@82 78 <h3 class="section">6.6 Other multi-dimensional Real-Data MPI Transforms</h3>
Chris@82 79
Chris@82 80 <a name="index-r2r-3"></a>
Chris@82 81 <p>FFTW&rsquo;s MPI interface also supports multi-dimensional &lsquo;<samp>r2r</samp>&rsquo;
Chris@82 82 transforms of all kinds supported by the serial interface
Chris@82 83 (e.g. discrete cosine and sine transforms, discrete Hartley
Chris@82 84 transforms, etc.). Only multi-dimensional &lsquo;<samp>r2r</samp>&rsquo; transforms, not
Chris@82 85 one-dimensional transforms, are currently parallelized.
Chris@82 86 </p>
Chris@82 87 <a name="index-fftw_005fr2r_005fkind-1"></a>
Chris@82 88 <p>These are used much like the multidimensional complex DFTs discussed
Chris@82 89 above, except that the data is real rather than complex, and one needs
Chris@82 90 to pass an r2r transform kind (<code>fftw_r2r_kind</code>) for each
Chris@82 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>).
Chris@82 92 </p>
Chris@82 93 <p>For example, one might perform a two-dimensional L&nbsp;&times;&nbsp;M
Chris@82 94 that is
Chris@82 95 an REDFT10 (DCT-II) in the first dimension and an RODFT10 (DST-II) in
Chris@82 96 the second dimension with code like:
Chris@82 97 </p>
Chris@82 98 <div class="example">
Chris@82 99 <pre class="example"> const ptrdiff_t L = ..., M = ...;
Chris@82 100 fftw_plan plan;
Chris@82 101 double *data;
Chris@82 102 ptrdiff_t alloc_local, local_n0, local_0_start, i, j;
Chris@82 103
Chris@82 104 /* <span class="roman">get local data size and allocate</span> */
Chris@82 105 alloc_local = fftw_mpi_local_size_2d(L, M, MPI_COMM_WORLD,
Chris@82 106 &amp;local_n0, &amp;local_0_start);
Chris@82 107 data = fftw_alloc_real(alloc_local);
Chris@82 108
Chris@82 109 /* <span class="roman">create plan for in-place REDFT10 x RODFT10</span> */
Chris@82 110 plan = fftw_mpi_plan_r2r_2d(L, M, data, data, MPI_COMM_WORLD,
Chris@82 111 FFTW_REDFT10, FFTW_RODFT10, FFTW_MEASURE);
Chris@82 112
Chris@82 113 /* <span class="roman">initialize data to some function</span> my_function(x,y) */
Chris@82 114 for (i = 0; i &lt; local_n0; ++i) for (j = 0; j &lt; M; ++j)
Chris@82 115 data[i*M + j] = my_function(local_0_start + i, j);
Chris@82 116
Chris@82 117 /* <span class="roman">compute transforms, in-place, as many times as desired</span> */
Chris@82 118 fftw_execute(plan);
Chris@82 119
Chris@82 120 fftw_destroy_plan(plan);
Chris@82 121 </pre></div>
Chris@82 122
Chris@82 123 <a name="index-fftw_005falloc_005freal-3"></a>
Chris@82 124 <p>Notice that we use the same &lsquo;<samp>local_size</samp>&rsquo; functions as we did for
Chris@82 125 complex data, only now we interpret the sizes in terms of real rather
Chris@82 126 than complex values, and correspondingly use <code>fftw_alloc_real</code>.
Chris@82 127 </p>
Chris@82 128
Chris@82 129
Chris@82 130
Chris@82 131 </body>
Chris@82 132 </html>