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Add FFTW3
author Chris Cannam <cannam@all-day-breakfast.com>
date Wed, 20 Mar 2013 15:35:50 +0000
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cannam@95 1 <html lang="en">
cannam@95 2 <head>
cannam@95 3 <title>Other Multi-dimensional Real-data MPI Transforms - FFTW 3.3.3</title>
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cannam@95 8 <link rel="up" href="Distributed_002dmemory-FFTW-with-MPI.html#Distributed_002dmemory-FFTW-with-MPI" title="Distributed-memory FFTW with MPI">
cannam@95 9 <link rel="prev" href="Multi_002ddimensional-MPI-DFTs-of-Real-Data.html#Multi_002ddimensional-MPI-DFTs-of-Real-Data" title="Multi-dimensional MPI DFTs of Real Data">
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cannam@95 12 <!--
cannam@95 13 This manual is for FFTW
cannam@95 14 (version 3.3.3, 25 November 2012).
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cannam@95 16 Copyright (C) 2003 Matteo Frigo.
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cannam@95 18 Copyright (C) 2003 Massachusetts Institute of Technology.
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cannam@95 48 <div class="node">
cannam@95 49 <a name="Other-Multi-dimensional-Real-data-MPI-Transforms"></a>
cannam@95 50 <a name="Other-Multi_002ddimensional-Real_002ddata-MPI-Transforms"></a>
cannam@95 51 <p>
cannam@95 52 Next:&nbsp;<a rel="next" accesskey="n" href="FFTW-MPI-Transposes.html#FFTW-MPI-Transposes">FFTW MPI Transposes</a>,
cannam@95 53 Previous:&nbsp;<a rel="previous" accesskey="p" href="Multi_002ddimensional-MPI-DFTs-of-Real-Data.html#Multi_002ddimensional-MPI-DFTs-of-Real-Data">Multi-dimensional MPI DFTs of Real Data</a>,
cannam@95 54 Up:&nbsp;<a rel="up" accesskey="u" href="Distributed_002dmemory-FFTW-with-MPI.html#Distributed_002dmemory-FFTW-with-MPI">Distributed-memory FFTW with MPI</a>
cannam@95 55 <hr>
cannam@95 56 </div>
cannam@95 57
cannam@95 58 <h3 class="section">6.6 Other multi-dimensional Real-Data MPI Transforms</h3>
cannam@95 59
cannam@95 60 <p><a name="index-r2r-393"></a>FFTW's MPI interface also supports multi-dimensional &lsquo;<samp><span class="samp">r2r</span></samp>&rsquo;
cannam@95 61 transforms of all kinds supported by the serial interface
cannam@95 62 (e.g. discrete cosine and sine transforms, discrete Hartley
cannam@95 63 transforms, etc.). Only multi-dimensional &lsquo;<samp><span class="samp">r2r</span></samp>&rsquo; transforms, not
cannam@95 64 one-dimensional transforms, are currently parallelized.
cannam@95 65
cannam@95 66 <p><a name="index-fftw_005fr2r_005fkind-394"></a>These are used much like the multidimensional complex DFTs discussed
cannam@95 67 above, except that the data is real rather than complex, and one needs
cannam@95 68 to pass an r2r transform kind (<code>fftw_r2r_kind</code>) for each
cannam@95 69 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@95 70
cannam@95 71 <p>For example, one might perform a two-dimensional L&nbsp;&times;&nbsp;M that is
cannam@95 72 an REDFT10 (DCT-II) in the first dimension and an RODFT10 (DST-II) in
cannam@95 73 the second dimension with code like:
cannam@95 74
cannam@95 75 <pre class="example"> const ptrdiff_t L = ..., M = ...;
cannam@95 76 fftw_plan plan;
cannam@95 77 double *data;
cannam@95 78 ptrdiff_t alloc_local, local_n0, local_0_start, i, j;
cannam@95 79
cannam@95 80 /* <span class="roman">get local data size and allocate</span> */
cannam@95 81 alloc_local = fftw_mpi_local_size_2d(L, M, MPI_COMM_WORLD,
cannam@95 82 &amp;local_n0, &amp;local_0_start);
cannam@95 83 data = fftw_alloc_real(alloc_local);
cannam@95 84
cannam@95 85 /* <span class="roman">create plan for in-place REDFT10 x RODFT10</span> */
cannam@95 86 plan = fftw_mpi_plan_r2r_2d(L, M, data, data, MPI_COMM_WORLD,
cannam@95 87 FFTW_REDFT10, FFTW_RODFT10, FFTW_MEASURE);
cannam@95 88
cannam@95 89 /* <span class="roman">initialize data to some function</span> my_function(x,y) */
cannam@95 90 for (i = 0; i &lt; local_n0; ++i) for (j = 0; j &lt; M; ++j)
cannam@95 91 data[i*M + j] = my_function(local_0_start + i, j);
cannam@95 92
cannam@95 93 /* <span class="roman">compute transforms, in-place, as many times as desired</span> */
cannam@95 94 fftw_execute(plan);
cannam@95 95
cannam@95 96 fftw_destroy_plan(plan);
cannam@95 97 </pre>
cannam@95 98 <p><a name="index-fftw_005falloc_005freal-395"></a>Notice that we use the same &lsquo;<samp><span class="samp">local_size</span></samp>&rsquo; functions as we did for
cannam@95 99 complex data, only now we interpret the sizes in terms of real rather
cannam@95 100 than complex values, and correspondingly use <code>fftw_alloc_real</code>.
cannam@95 101
cannam@95 102 <!-- -->
cannam@95 103 </body></html>
cannam@95 104