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Current fftw source
author Chris Cannam
date Tue, 18 Oct 2016 13:40:26 +0100
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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.
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10 Permission is granted to make and distribute verbatim copies of this
11 manual provided the copyright notice and this permission notice are
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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
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20 into another language, under the above conditions for modified versions,
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24 <head>
25 <title>FFTW 3.3.5: Memory Allocation</title>
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27 <meta name="description" content="FFTW 3.3.5: Memory Allocation">
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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">
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71 <body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
72 <a name="Memory-Allocation"></a>
73 <div class="header">
74 <p>
75 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>
76 </div>
77 <hr>
78 <a name="Memory-Allocation-1"></a>
79 <h4 class="subsection">4.1.3 Memory Allocation</h4>
80
81 <div class="example">
82 <pre class="example">void *fftw_malloc(size_t n);
83 void fftw_free(void *p);
84 </pre></div>
85 <a name="index-fftw_005fmalloc-3"></a>
86 <a name="index-fftw_005ffree-2"></a>
87
88 <p>These are functions that behave identically to <code>malloc</code> and
89 <code>free</code>, except that they guarantee that the returned pointer obeys
90 any special alignment restrictions imposed by any algorithm in FFTW
91 (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>.
92 <a name="index-alignment"></a>
93 </p>
94
95 <p>Data allocated by <code>fftw_malloc</code> <em>must</em> be deallocated by
96 <code>fftw_free</code> and not by the ordinary <code>free</code>.
97 </p>
98 <p>These routines simply call through to your operating system&rsquo;s
99 <code>malloc</code> or, if necessary, its aligned equivalent
100 (e.g. <code>memalign</code>), so you normally need not worry about any
101 significant time or space overhead. You are <em>not required</em> to use
102 them to allocate your data, but we strongly recommend it.
103 </p>
104 <p>Note: in C++, just as with ordinary <code>malloc</code>, you must typecast
105 the output of <code>fftw_malloc</code> to whatever pointer type you are
106 allocating.
107 <a name="index-C_002b_002b-4"></a>
108 </p>
109
110 <p>We also provide the following two convenience functions to allocate
111 real and complex arrays with <code>n</code> elements, which are equivalent
112 to <code>(double *) fftw_malloc(sizeof(double) * n)</code> and
113 <code>(fftw_complex *) fftw_malloc(sizeof(fftw_complex) * n)</code>,
114 respectively:
115 </p>
116 <div class="example">
117 <pre class="example">double *fftw_alloc_real(size_t n);
118 fftw_complex *fftw_alloc_complex(size_t n);
119 </pre></div>
120 <a name="index-fftw_005falloc_005freal-1"></a>
121 <a name="index-fftw_005falloc_005fcomplex-2"></a>
122
123 <p>The equivalent functions in other precisions allocate arrays of <code>n</code>
124 elements in that precision. e.g. <code>fftwf_alloc_real(n)</code> is
125 equivalent to <code>(float *) fftwf_malloc(sizeof(float) * n)</code>.
126 <a name="index-precision-4"></a>
127 </p>
128
129
130
131 </body>
132 </html>