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Current fftw source
author Chris Cannam
date Tue, 18 Oct 2016 13:40:26 +0100
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Chris@42 24 <head>
Chris@42 25 <title>FFTW 3.3.5: MPI Data Distribution Functions</title>
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Chris@42 71 <body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
Chris@42 72 <a name="MPI-Data-Distribution-Functions"></a>
Chris@42 73 <div class="header">
Chris@42 74 <p>
Chris@42 75 Next: <a href="MPI-Plan-Creation.html#MPI-Plan-Creation" accesskey="n" rel="next">MPI Plan Creation</a>, Previous: <a href="Using-MPI-Plans.html#Using-MPI-Plans" accesskey="p" rel="prev">Using MPI Plans</a>, Up: <a href="FFTW-MPI-Reference.html#FFTW-MPI-Reference" accesskey="u" rel="up">FFTW MPI Reference</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@42 76 </div>
Chris@42 77 <hr>
Chris@42 78 <a name="MPI-Data-Distribution-Functions-1"></a>
Chris@42 79 <h4 class="subsection">6.12.4 MPI Data Distribution Functions</h4>
Chris@42 80
Chris@42 81 <a name="index-data-distribution-5"></a>
Chris@42 82 <p>As described above (see <a href="MPI-Data-Distribution.html#MPI-Data-Distribution">MPI Data Distribution</a>), in order to
Chris@42 83 allocate your arrays, <em>before</em> creating a plan, you must first
Chris@42 84 call one of the following routines to determine the required
Chris@42 85 allocation size and the portion of the array locally stored on a given
Chris@42 86 process. The <code>MPI_Comm</code> communicator passed here must be
Chris@42 87 equivalent to the communicator used below for plan creation.
Chris@42 88 </p>
Chris@42 89 <p>The basic interface for multidimensional transforms consists of the
Chris@42 90 functions:
Chris@42 91 </p>
Chris@42 92 <a name="index-fftw_005fmpi_005flocal_005fsize_005f2d-2"></a>
Chris@42 93 <a name="index-fftw_005fmpi_005flocal_005fsize_005f3d"></a>
Chris@42 94 <a name="index-fftw_005fmpi_005flocal_005fsize"></a>
Chris@42 95 <a name="index-fftw_005fmpi_005flocal_005fsize_005f2d_005ftransposed-1"></a>
Chris@42 96 <a name="index-fftw_005fmpi_005flocal_005fsize_005f3d_005ftransposed-1"></a>
Chris@42 97 <a name="index-fftw_005fmpi_005flocal_005fsize_005ftransposed"></a>
Chris@42 98 <div class="example">
Chris@42 99 <pre class="example">ptrdiff_t fftw_mpi_local_size_2d(ptrdiff_t n0, ptrdiff_t n1, MPI_Comm comm,
Chris@42 100 ptrdiff_t *local_n0, ptrdiff_t *local_0_start);
Chris@42 101 ptrdiff_t fftw_mpi_local_size_3d(ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t n2,
Chris@42 102 MPI_Comm comm,
Chris@42 103 ptrdiff_t *local_n0, ptrdiff_t *local_0_start);
Chris@42 104 ptrdiff_t fftw_mpi_local_size(int rnk, const ptrdiff_t *n, MPI_Comm comm,
Chris@42 105 ptrdiff_t *local_n0, ptrdiff_t *local_0_start);
Chris@42 106
Chris@42 107 ptrdiff_t fftw_mpi_local_size_2d_transposed(ptrdiff_t n0, ptrdiff_t n1, MPI_Comm comm,
Chris@42 108 ptrdiff_t *local_n0, ptrdiff_t *local_0_start,
Chris@42 109 ptrdiff_t *local_n1, ptrdiff_t *local_1_start);
Chris@42 110 ptrdiff_t fftw_mpi_local_size_3d_transposed(ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t n2,
Chris@42 111 MPI_Comm comm,
Chris@42 112 ptrdiff_t *local_n0, ptrdiff_t *local_0_start,
Chris@42 113 ptrdiff_t *local_n1, ptrdiff_t *local_1_start);
Chris@42 114 ptrdiff_t fftw_mpi_local_size_transposed(int rnk, const ptrdiff_t *n, MPI_Comm comm,
Chris@42 115 ptrdiff_t *local_n0, ptrdiff_t *local_0_start,
Chris@42 116 ptrdiff_t *local_n1, ptrdiff_t *local_1_start);
Chris@42 117 </pre></div>
Chris@42 118
Chris@42 119 <p>These functions return the number of elements to allocate (complex
Chris@42 120 numbers for DFT/r2c/c2r plans, real numbers for r2r plans), whereas
Chris@42 121 the <code>local_n0</code> and <code>local_0_start</code> return the portion
Chris@42 122 (<code>local_0_start</code> to <code>local_0_start + local_n0 - 1</code>) of the
Chris@42 123 first dimension of an n<sub>0</sub>&nbsp;&times;&nbsp;n<sub>1</sub>&nbsp;&times;&nbsp;n<sub>2</sub>&nbsp;&times;&nbsp;&hellip;&nbsp;&times;&nbsp;n<sub>d-1</sub> array that is stored on the local
Chris@42 124 process. See <a href="Basic-and-advanced-distribution-interfaces.html#Basic-and-advanced-distribution-interfaces">Basic and advanced distribution interfaces</a>. For
Chris@42 125 <code>FFTW_MPI_TRANSPOSED_OUT</code> plans, the &lsquo;<samp>_transposed</samp>&rsquo; variants
Chris@42 126 are useful in order to also return the local portion of the first
Chris@42 127 dimension in the n<sub>1</sub>&nbsp;&times;&nbsp;n<sub>0</sub>&nbsp;&times;&nbsp;n<sub>2</sub>&nbsp;&times;&hellip;&times;&nbsp;n<sub>d-1</sub> transposed output.
Chris@42 128 See <a href="Transposed-distributions.html#Transposed-distributions">Transposed distributions</a>.
Chris@42 129 The advanced interface for multidimensional transforms is:
Chris@42 130 </p>
Chris@42 131 <a name="index-advanced-interface-5"></a>
Chris@42 132 <a name="index-fftw_005fmpi_005flocal_005fsize_005fmany-1"></a>
Chris@42 133 <a name="index-fftw_005fmpi_005flocal_005fsize_005fmany_005ftransposed-1"></a>
Chris@42 134 <div class="example">
Chris@42 135 <pre class="example">ptrdiff_t fftw_mpi_local_size_many(int rnk, const ptrdiff_t *n, ptrdiff_t howmany,
Chris@42 136 ptrdiff_t block0, MPI_Comm comm,
Chris@42 137 ptrdiff_t *local_n0, ptrdiff_t *local_0_start);
Chris@42 138 ptrdiff_t fftw_mpi_local_size_many_transposed(int rnk, const ptrdiff_t *n, ptrdiff_t howmany,
Chris@42 139 ptrdiff_t block0, ptrdiff_t block1, MPI_Comm comm,
Chris@42 140 ptrdiff_t *local_n0, ptrdiff_t *local_0_start,
Chris@42 141 ptrdiff_t *local_n1, ptrdiff_t *local_1_start);
Chris@42 142 </pre></div>
Chris@42 143
Chris@42 144 <p>These differ from the basic interface in only two ways. First, they
Chris@42 145 allow you to specify block sizes <code>block0</code> and <code>block1</code> (the
Chris@42 146 latter for the transposed output); you can pass
Chris@42 147 <code>FFTW_MPI_DEFAULT_BLOCK</code> to use FFTW&rsquo;s default block size as in
Chris@42 148 the basic interface. Second, you can pass a <code>howmany</code> parameter,
Chris@42 149 corresponding to the advanced planning interface below: this is for
Chris@42 150 transforms of contiguous <code>howmany</code>-tuples of numbers
Chris@42 151 (<code>howmany = 1</code> in the basic interface).
Chris@42 152 </p>
Chris@42 153 <p>The corresponding basic and advanced routines for one-dimensional
Chris@42 154 transforms (currently only complex DFTs) are:
Chris@42 155 </p>
Chris@42 156 <a name="index-fftw_005fmpi_005flocal_005fsize_005f1d-1"></a>
Chris@42 157 <a name="index-fftw_005fmpi_005flocal_005fsize_005fmany_005f1d"></a>
Chris@42 158 <div class="example">
Chris@42 159 <pre class="example">ptrdiff_t fftw_mpi_local_size_1d(
Chris@42 160 ptrdiff_t n0, MPI_Comm comm, int sign, unsigned flags,
Chris@42 161 ptrdiff_t *local_ni, ptrdiff_t *local_i_start,
Chris@42 162 ptrdiff_t *local_no, ptrdiff_t *local_o_start);
Chris@42 163 ptrdiff_t fftw_mpi_local_size_many_1d(
Chris@42 164 ptrdiff_t n0, ptrdiff_t howmany,
Chris@42 165 MPI_Comm comm, int sign, unsigned flags,
Chris@42 166 ptrdiff_t *local_ni, ptrdiff_t *local_i_start,
Chris@42 167 ptrdiff_t *local_no, ptrdiff_t *local_o_start);
Chris@42 168 </pre></div>
Chris@42 169
Chris@42 170 <a name="index-FFTW_005fMPI_005fSCRAMBLED_005fOUT-1"></a>
Chris@42 171 <a name="index-FFTW_005fMPI_005fSCRAMBLED_005fIN-1"></a>
Chris@42 172 <p>As above, the return value is the number of elements to allocate
Chris@42 173 (complex numbers, for complex DFTs). The <code>local_ni</code> and
Chris@42 174 <code>local_i_start</code> arguments return the portion
Chris@42 175 (<code>local_i_start</code> to <code>local_i_start + local_ni - 1</code>) of the
Chris@42 176 1d array that is stored on this process for the transform
Chris@42 177 <em>input</em>, and <code>local_no</code> and <code>local_o_start</code> are the
Chris@42 178 corresponding quantities for the input. The <code>sign</code>
Chris@42 179 (<code>FFTW_FORWARD</code> or <code>FFTW_BACKWARD</code>) and <code>flags</code> must
Chris@42 180 match the arguments passed when creating a plan. Although the inputs
Chris@42 181 and outputs have different data distributions in general, it is
Chris@42 182 guaranteed that the <em>output</em> data distribution of an
Chris@42 183 <code>FFTW_FORWARD</code> plan will match the <em>input</em> data distribution
Chris@42 184 of an <code>FFTW_BACKWARD</code> plan and vice versa; similarly for the
Chris@42 185 <code>FFTW_MPI_SCRAMBLED_OUT</code> and <code>FFTW_MPI_SCRAMBLED_IN</code> flags.
Chris@42 186 See <a href="One_002ddimensional-distributions.html#One_002ddimensional-distributions">One-dimensional distributions</a>.
Chris@42 187 </p>
Chris@42 188 <hr>
Chris@42 189 <div class="header">
Chris@42 190 <p>
Chris@42 191 Next: <a href="MPI-Plan-Creation.html#MPI-Plan-Creation" accesskey="n" rel="next">MPI Plan Creation</a>, Previous: <a href="Using-MPI-Plans.html#Using-MPI-Plans" accesskey="p" rel="prev">Using MPI Plans</a>, Up: <a href="FFTW-MPI-Reference.html#FFTW-MPI-Reference" accesskey="u" rel="up">FFTW MPI Reference</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@42 192 </div>
Chris@42 193
Chris@42 194
Chris@42 195
Chris@42 196 </body>
Chris@42 197 </html>