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Add FFTW 3.3.8 source, and a Linux build
author Chris Cannam
date Tue, 19 Nov 2019 14:52:55 +0000
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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).
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Chris@82 6 Copyright (C) 2003 Matteo Frigo.
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Chris@82 24 <head>
Chris@82 25 <title>FFTW 3.3.8: Basic distributed-transpose interface</title>
Chris@82 26
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Chris@82 36 <link href="FFTW-MPI-Transposes.html#FFTW-MPI-Transposes" rel="up" title="FFTW MPI Transposes">
Chris@82 37 <link href="Advanced-distributed_002dtranspose-interface.html#Advanced-distributed_002dtranspose-interface" rel="next" title="Advanced distributed-transpose interface">
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Chris@82 68 </head>
Chris@82 69
Chris@82 70 <body lang="en">
Chris@82 71 <a name="Basic-distributed_002dtranspose-interface"></a>
Chris@82 72 <div class="header">
Chris@82 73 <p>
Chris@82 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>
Chris@82 75 </div>
Chris@82 76 <hr>
Chris@82 77 <a name="Basic-distributed_002dtranspose-interface-1"></a>
Chris@82 78 <h4 class="subsection">6.7.1 Basic distributed-transpose interface</h4>
Chris@82 79
Chris@82 80 <p>In particular, suppose that we have an <code>n0</code> by <code>n1</code> array in
Chris@82 81 row-major order, block-distributed across the <code>n0</code> dimension. To
Chris@82 82 transpose this into an <code>n1</code> by <code>n0</code> array block-distributed
Chris@82 83 across the <code>n1</code> dimension, we would create a plan by calling the
Chris@82 84 following function:
Chris@82 85 </p>
Chris@82 86 <div class="example">
Chris@82 87 <pre class="example">fftw_plan fftw_mpi_plan_transpose(ptrdiff_t n0, ptrdiff_t n1,
Chris@82 88 double *in, double *out,
Chris@82 89 MPI_Comm comm, unsigned flags);
Chris@82 90 </pre></div>
Chris@82 91 <a name="index-fftw_005fmpi_005fplan_005ftranspose"></a>
Chris@82 92
Chris@82 93 <p>The input and output arrays (<code>in</code> and <code>out</code>) can be the
Chris@82 94 same. The transpose is actually executed by calling
Chris@82 95 <code>fftw_execute</code> on the plan, as usual.
Chris@82 96 <a name="index-fftw_005fexecute-3"></a>
Chris@82 97 </p>
Chris@82 98
Chris@82 99 <p>The <code>flags</code> are the usual FFTW planner flags, but support
Chris@82 100 two additional flags: <code>FFTW_MPI_TRANSPOSED_OUT</code> and/or
Chris@82 101 <code>FFTW_MPI_TRANSPOSED_IN</code>. What these flags indicate, for
Chris@82 102 transpose plans, is that the output and/or input, respectively, are
Chris@82 103 <em>locally</em> transposed. That is, on each process input data is
Chris@82 104 normally stored as a <code>local_n0</code> by <code>n1</code> array in row-major
Chris@82 105 order, but for an <code>FFTW_MPI_TRANSPOSED_IN</code> plan the input data is
Chris@82 106 stored as <code>n1</code> by <code>local_n0</code> in row-major order. Similarly,
Chris@82 107 <code>FFTW_MPI_TRANSPOSED_OUT</code> means that the output is <code>n0</code> by
Chris@82 108 <code>local_n1</code> instead of <code>local_n1</code> by <code>n0</code>.
Chris@82 109 <a name="index-FFTW_005fMPI_005fTRANSPOSED_005fOUT-1"></a>
Chris@82 110 <a name="index-FFTW_005fMPI_005fTRANSPOSED_005fIN-1"></a>
Chris@82 111 </p>
Chris@82 112
Chris@82 113 <p>To determine the local size of the array on each process before and
Chris@82 114 after the transpose, as well as the amount of storage that must be
Chris@82 115 allocated, one should call <code>fftw_mpi_local_size_2d_transposed</code>,
Chris@82 116 just as for a 2d DFT as described in the previous section:
Chris@82 117 <a name="index-data-distribution-4"></a>
Chris@82 118 </p>
Chris@82 119 <div class="example">
Chris@82 120 <pre class="example">ptrdiff_t fftw_mpi_local_size_2d_transposed
Chris@82 121 (ptrdiff_t n0, ptrdiff_t n1, MPI_Comm comm,
Chris@82 122 ptrdiff_t *local_n0, ptrdiff_t *local_0_start,
Chris@82 123 ptrdiff_t *local_n1, ptrdiff_t *local_1_start);
Chris@82 124 </pre></div>
Chris@82 125 <a name="index-fftw_005fmpi_005flocal_005fsize_005f2d_005ftransposed"></a>
Chris@82 126
Chris@82 127 <p>Again, the return value is the local storage to allocate, which in
Chris@82 128 this case is the number of <em>real</em> (<code>double</code>) values rather
Chris@82 129 than complex numbers as in the previous examples.
Chris@82 130 </p>
Chris@82 131 <hr>
Chris@82 132 <div class="header">
Chris@82 133 <p>
Chris@82 134 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>
Chris@82 135 </div>
Chris@82 136
Chris@82 137
Chris@82 138
Chris@82 139 </body>
Chris@82 140 </html>