Mercurial > hg > sv-dependency-builds

comparison src/fftw-3.3.8/doc/html/Memory-Allocation.html @ 82:d0c2a83c1364

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Add FFTW 3.3.8 source, and a Linux build
author Chris Cannam
date Tue, 19 Nov 2019 14:52:55 +0000
parents
children
comparison
equal deleted inserted replaced
81:7029a4916348 82:d0c2a83c1364
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 3.3.8, 24 May 2018).
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 6.3, http://www.gnu.org/software/texinfo/ -->
24 <head>
25 <title>FFTW 3.3.8: Memory Allocation</title>
26
27 <meta name="description" content="FFTW 3.3.8: Memory Allocation">
28 <meta name="keywords" content="FFTW 3.3.8: Memory Allocation">
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="Data-Types-and-Files.html#Data-Types-and-Files" rel="up" title="Data Types and Files">
37 <link href="Using-Plans.html#Using-Plans" rel="next" title="Using Plans">
38 <link href="Precision.html#Precision" rel="prev" title="Precision">
39 <style type="text/css">
40 <!--
41 a.summary-letter {text-decoration: none}
42 blockquote.indentedblock {margin-right: 0em}
43 blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
44 blockquote.smallquotation {font-size: smaller}
45 div.display {margin-left: 3.2em}
46 div.example {margin-left: 3.2em}
47 div.lisp {margin-left: 3.2em}
48 div.smalldisplay {margin-left: 3.2em}
49 div.smallexample {margin-left: 3.2em}
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.nolinebreak {white-space: nowrap}
61 span.roman {font-family: initial; font-weight: normal}
62 span.sansserif {font-family: sans-serif; font-weight: normal}
63 ul.no-bullet {list-style: none}
64 -->
65 </style>
66
67
68 </head>
69
70 <body lang="en">
71 <a name="Memory-Allocation"></a>
72 <div class="header">
73 <p>
74 Previous: <a href="Precision.html#Precision" accesskey="p" rel="prev">Precision</a>, Up: <a href="Data-Types-and-Files.html#Data-Types-and-Files" accesskey="u" rel="up">Data Types and Files</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>
75 </div>
76 <hr>
77 <a name="Memory-Allocation-1"></a>
78 <h4 class="subsection">4.1.3 Memory Allocation</h4>
79
80 <div class="example">
81 <pre class="example">void *fftw_malloc(size_t n);
82 void fftw_free(void *p);
83 </pre></div>
84 <a name="index-fftw_005fmalloc-3"></a>
85 <a name="index-fftw_005ffree-2"></a>
86
87 <p>These are functions that behave identically to <code>malloc</code> and
88 <code>free</code>, except that they guarantee that the returned pointer obeys
89 any special alignment restrictions imposed by any algorithm in FFTW
90 (e.g. for SIMD acceleration). See <a href="SIMD-alignment-and-fftw_005fmalloc.html#SIMD-alignment-and-fftw_005fmalloc">SIMD alignment and fftw_malloc</a>.
91 <a name="index-alignment"></a>
92 </p>
93
94 <p>Data allocated by <code>fftw_malloc</code> <em>must</em> be deallocated by
95 <code>fftw_free</code> and not by the ordinary <code>free</code>.
96 </p>
97 <p>These routines simply call through to your operating system&rsquo;s
98 <code>malloc</code> or, if necessary, its aligned equivalent
99 (e.g. <code>memalign</code>), so you normally need not worry about any
100 significant time or space overhead. You are <em>not required</em> to use
101 them to allocate your data, but we strongly recommend it.
102 </p>
103 <p>Note: in C++, just as with ordinary <code>malloc</code>, you must typecast
104 the output of <code>fftw_malloc</code> to whatever pointer type you are
105 allocating.
106 <a name="index-C_002b_002b-4"></a>
107 </p>
108
109 <p>We also provide the following two convenience functions to allocate
110 real and complex arrays with <code>n</code> elements, which are equivalent
111 to <code>(double *) fftw_malloc(sizeof(double) * n)</code> and
112 <code>(fftw_complex *) fftw_malloc(sizeof(fftw_complex) * n)</code>,
113 respectively:
114 </p>
115 <div class="example">
116 <pre class="example">double *fftw_alloc_real(size_t n);
117 fftw_complex *fftw_alloc_complex(size_t n);
118 </pre></div>
119 <a name="index-fftw_005falloc_005freal-1"></a>
120 <a name="index-fftw_005falloc_005fcomplex-2"></a>
121
122 <p>The equivalent functions in other precisions allocate arrays of <code>n</code>
123 elements in that precision. e.g. <code>fftwf_alloc_real(n)</code> is
124 equivalent to <code>(float *) fftwf_malloc(sizeof(float) * n)</code>.
125 <a name="index-precision-4"></a>
126 </p>
127
128
129
130 </body>
131 </html>