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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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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.
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cannam@167 8 Copyright (C) 2003 Massachusetts Institute of Technology.
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cannam@167 24 <head>
cannam@167 25 <title>FFTW 3.3.8: Basic distributed-transpose interface</title>
cannam@167 26
cannam@167 27 <meta name="description" content="FFTW 3.3.8: Basic distributed-transpose interface">
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cannam@167 36 <link href="FFTW-MPI-Transposes.html#FFTW-MPI-Transposes" rel="up" title="FFTW MPI Transposes">
cannam@167 37 <link href="Advanced-distributed_002dtranspose-interface.html#Advanced-distributed_002dtranspose-interface" rel="next" title="Advanced distributed-transpose interface">
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cannam@167 68 </head>
cannam@167 69
cannam@167 70 <body lang="en">
cannam@167 71 <a name="Basic-distributed_002dtranspose-interface"></a>
cannam@167 72 <div class="header">
cannam@167 73 <p>
cannam@167 74 Next: <a href="Advanced-distributed_002dtranspose-interface.html#Advanced-distributed_002dtranspose-interface" accesskey="n" rel="next">Advanced distributed-transpose interface</a>, Previous: <a href="FFTW-MPI-Transposes.html#FFTW-MPI-Transposes" accesskey="p" rel="prev">FFTW MPI Transposes</a>, Up: <a href="FFTW-MPI-Transposes.html#FFTW-MPI-Transposes" accesskey="u" rel="up">FFTW MPI Transposes</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="Basic-distributed_002dtranspose-interface-1"></a>
cannam@167 78 <h4 class="subsection">6.7.1 Basic distributed-transpose interface</h4>
cannam@167 79
cannam@167 80 <p>In particular, suppose that we have an <code>n0</code> by <code>n1</code> array in
cannam@167 81 row-major order, block-distributed across the <code>n0</code> dimension. To
cannam@167 82 transpose this into an <code>n1</code> by <code>n0</code> array block-distributed
cannam@167 83 across the <code>n1</code> dimension, we would create a plan by calling the
cannam@167 84 following function:
cannam@167 85 </p>
cannam@167 86 <div class="example">
cannam@167 87 <pre class="example">fftw_plan fftw_mpi_plan_transpose(ptrdiff_t n0, ptrdiff_t n1,
cannam@167 88 double *in, double *out,
cannam@167 89 MPI_Comm comm, unsigned flags);
cannam@167 90 </pre></div>
cannam@167 91 <a name="index-fftw_005fmpi_005fplan_005ftranspose"></a>
cannam@167 92
cannam@167 93 <p>The input and output arrays (<code>in</code> and <code>out</code>) can be the
cannam@167 94 same. The transpose is actually executed by calling
cannam@167 95 <code>fftw_execute</code> on the plan, as usual.
cannam@167 96 <a name="index-fftw_005fexecute-3"></a>
cannam@167 97 </p>
cannam@167 98
cannam@167 99 <p>The <code>flags</code> are the usual FFTW planner flags, but support
cannam@167 100 two additional flags: <code>FFTW_MPI_TRANSPOSED_OUT</code> and/or
cannam@167 101 <code>FFTW_MPI_TRANSPOSED_IN</code>. What these flags indicate, for
cannam@167 102 transpose plans, is that the output and/or input, respectively, are
cannam@167 103 <em>locally</em> transposed. That is, on each process input data is
cannam@167 104 normally stored as a <code>local_n0</code> by <code>n1</code> array in row-major
cannam@167 105 order, but for an <code>FFTW_MPI_TRANSPOSED_IN</code> plan the input data is
cannam@167 106 stored as <code>n1</code> by <code>local_n0</code> in row-major order. Similarly,
cannam@167 107 <code>FFTW_MPI_TRANSPOSED_OUT</code> means that the output is <code>n0</code> by
cannam@167 108 <code>local_n1</code> instead of <code>local_n1</code> by <code>n0</code>.
cannam@167 109 <a name="index-FFTW_005fMPI_005fTRANSPOSED_005fOUT-1"></a>
cannam@167 110 <a name="index-FFTW_005fMPI_005fTRANSPOSED_005fIN-1"></a>
cannam@167 111 </p>
cannam@167 112
cannam@167 113 <p>To determine the local size of the array on each process before and
cannam@167 114 after the transpose, as well as the amount of storage that must be
cannam@167 115 allocated, one should call <code>fftw_mpi_local_size_2d_transposed</code>,
cannam@167 116 just as for a 2d DFT as described in the previous section:
cannam@167 117 <a name="index-data-distribution-4"></a>
cannam@167 118 </p>
cannam@167 119 <div class="example">
cannam@167 120 <pre class="example">ptrdiff_t fftw_mpi_local_size_2d_transposed
cannam@167 121 (ptrdiff_t n0, ptrdiff_t n1, MPI_Comm comm,
cannam@167 122 ptrdiff_t *local_n0, ptrdiff_t *local_0_start,
cannam@167 123 ptrdiff_t *local_n1, ptrdiff_t *local_1_start);
cannam@167 124 </pre></div>
cannam@167 125 <a name="index-fftw_005fmpi_005flocal_005fsize_005f2d_005ftransposed"></a>
cannam@167 126
cannam@167 127 <p>Again, the return value is the local storage to allocate, which in
cannam@167 128 this case is the number of <em>real</em> (<code>double</code>) values rather
cannam@167 129 than complex numbers as in the previous examples.
cannam@167 130 </p>
cannam@167 131 <hr>
cannam@167 132 <div class="header">
cannam@167 133 <p>
cannam@167 134 Next: <a href="Advanced-distributed_002dtranspose-interface.html#Advanced-distributed_002dtranspose-interface" accesskey="n" rel="next">Advanced distributed-transpose interface</a>, Previous: <a href="FFTW-MPI-Transposes.html#FFTW-MPI-Transposes" accesskey="p" rel="prev">FFTW MPI Transposes</a>, Up: <a href="FFTW-MPI-Transposes.html#FFTW-MPI-Transposes" accesskey="u" rel="up">FFTW MPI Transposes</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@167 135 </div>
cannam@167 136
cannam@167 137
cannam@167 138
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cannam@167 140 </html>