Mercurial > hg > sv-dependency-builds

comparison src/fftw-3.3.5/doc/html/Basic-distributed_002dtranspose-interface.html @ 127:7867fa7e1b6b

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Current fftw source
author Chris Cannam <cannam@all-day-breakfast.com>
date Tue, 18 Oct 2016 13:40:26 +0100
parents
children
comparison
equal deleted inserted replaced
126:4a7071416412 127:7867fa7e1b6b
1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
2 <html>
3 <!-- This manual is for FFTW
4 (version 3.3.5, 30 July 2016).
5
6 Copyright (C) 2003 Matteo Frigo.
7
8 Copyright (C) 2003 Massachusetts Institute of Technology.
9
10 Permission is granted to make and distribute verbatim copies of this
11 manual provided the copyright notice and this permission notice are
12 preserved on all copies.
13
14 Permission is granted to copy and distribute modified versions of this
15 manual under the conditions for verbatim copying, provided that the
16 entire resulting derived work is distributed under the terms of a
17 permission notice identical to this one.
18
19 Permission is granted to copy and distribute translations of this manual
20 into another language, under the above conditions for modified versions,
21 except that this permission notice may be stated in a translation
22 approved by the Free Software Foundation. -->
23 <!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ -->
24 <head>
25 <title>FFTW 3.3.5: Basic distributed-transpose interface</title>
26
27 <meta name="description" content="FFTW 3.3.5: Basic distributed-transpose interface">
28 <meta name="keywords" content="FFTW 3.3.5: Basic distributed-transpose interface">
29 <meta name="resource-type" content="document">
30 <meta name="distribution" content="global">
31 <meta name="Generator" content="makeinfo">
32 <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
33 <link href="index.html#Top" rel="start" title="Top">
34 <link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
35 <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
36 <link href="FFTW-MPI-Transposes.html#FFTW-MPI-Transposes" rel="up" title="FFTW MPI Transposes">
37 <link href="Advanced-distributed_002dtranspose-interface.html#Advanced-distributed_002dtranspose-interface" rel="next" title="Advanced distributed-transpose interface">
38 <link href="FFTW-MPI-Transposes.html#FFTW-MPI-Transposes" rel="prev" title="FFTW MPI Transposes">
39 <style type="text/css">
40 <!--
41 a.summary-letter {text-decoration: none}
42 blockquote.smallquotation {font-size: smaller}
43 div.display {margin-left: 3.2em}
44 div.example {margin-left: 3.2em}
45 div.indentedblock {margin-left: 3.2em}
46 div.lisp {margin-left: 3.2em}
47 div.smalldisplay {margin-left: 3.2em}
48 div.smallexample {margin-left: 3.2em}
49 div.smallindentedblock {margin-left: 3.2em; font-size: smaller}
50 div.smalllisp {margin-left: 3.2em}
51 kbd {font-style:oblique}
52 pre.display {font-family: inherit}
53 pre.format {font-family: inherit}
54 pre.menu-comment {font-family: serif}
55 pre.menu-preformatted {font-family: serif}
56 pre.smalldisplay {font-family: inherit; font-size: smaller}
57 pre.smallexample {font-size: smaller}
58 pre.smallformat {font-family: inherit; font-size: smaller}
59 pre.smalllisp {font-size: smaller}
60 span.nocodebreak {white-space:nowrap}
61 span.nolinebreak {white-space:nowrap}
62 span.roman {font-family:serif; font-weight:normal}
63 span.sansserif {font-family:sans-serif; font-weight:normal}
64 ul.no-bullet {list-style: none}
65 -->
66 </style>
67
68
69 </head>
70
71 <body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
72 <a name="Basic-distributed_002dtranspose-interface"></a>
73 <div class="header">
74 <p>
75 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>
76 </div>
77 <hr>
78 <a name="Basic-distributed_002dtranspose-interface-1"></a>
79 <h4 class="subsection">6.7.1 Basic distributed-transpose interface</h4>
80
81 <p>In particular, suppose that we have an <code>n0</code> by <code>n1</code> array in
82 row-major order, block-distributed across the <code>n0</code> dimension. To
83 transpose this into an <code>n1</code> by <code>n0</code> array block-distributed
84 across the <code>n1</code> dimension, we would create a plan by calling the
85 following function:
86 </p>
87 <div class="example">
88 <pre class="example">fftw_plan fftw_mpi_plan_transpose(ptrdiff_t n0, ptrdiff_t n1,
89 double *in, double *out,
90 MPI_Comm comm, unsigned flags);
91 </pre></div>
92 <a name="index-fftw_005fmpi_005fplan_005ftranspose"></a>
93
94 <p>The input and output arrays (<code>in</code> and <code>out</code>) can be the
95 same. The transpose is actually executed by calling
96 <code>fftw_execute</code> on the plan, as usual.
97 <a name="index-fftw_005fexecute-3"></a>
98 </p>
99
100 <p>The <code>flags</code> are the usual FFTW planner flags, but support
101 two additional flags: <code>FFTW_MPI_TRANSPOSED_OUT</code> and/or
102 <code>FFTW_MPI_TRANSPOSED_IN</code>. What these flags indicate, for
103 transpose plans, is that the output and/or input, respectively, are
104 <em>locally</em> transposed. That is, on each process input data is
105 normally stored as a <code>local_n0</code> by <code>n1</code> array in row-major
106 order, but for an <code>FFTW_MPI_TRANSPOSED_IN</code> plan the input data is
107 stored as <code>n1</code> by <code>local_n0</code> in row-major order. Similarly,
108 <code>FFTW_MPI_TRANSPOSED_OUT</code> means that the output is <code>n0</code> by
109 <code>local_n1</code> instead of <code>local_n1</code> by <code>n0</code>.
110 <a name="index-FFTW_005fMPI_005fTRANSPOSED_005fOUT-1"></a>
111 <a name="index-FFTW_005fMPI_005fTRANSPOSED_005fIN-1"></a>
112 </p>
113
114 <p>To determine the local size of the array on each process before and
115 after the transpose, as well as the amount of storage that must be
116 allocated, one should call <code>fftw_mpi_local_size_2d_transposed</code>,
117 just as for a 2d DFT as described in the previous section:
118 <a name="index-data-distribution-4"></a>
119 </p>
120 <div class="example">
121 <pre class="example">ptrdiff_t fftw_mpi_local_size_2d_transposed
122 (ptrdiff_t n0, ptrdiff_t n1, MPI_Comm comm,
123 ptrdiff_t *local_n0, ptrdiff_t *local_0_start,
124 ptrdiff_t *local_n1, ptrdiff_t *local_1_start);
125 </pre></div>
126 <a name="index-fftw_005fmpi_005flocal_005fsize_005f2d_005ftransposed"></a>
127
128 <p>Again, the return value is the local storage to allocate, which in
129 this case is the number of <em>real</em> (<code>double</code>) values rather
130 than complex numbers as in the previous examples.
131 </p>
132 <hr>
133 <div class="header">
134 <p>
135 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>
136 </div>
137
138
139
140 </body>
141 </html>