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author Chris Cannam <cannam@all-day-breakfast.com>
date Wed, 20 Mar 2013 15:35:50 +0000
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1 <html lang="en">
2 <head>
3 <title>Memory Allocation - FFTW 3.3.3</title>
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11 <!--
12 This manual is for FFTW
13 (version 3.3.3, 25 November 2012).
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15 Copyright (C) 2003 Matteo Frigo.
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17 Copyright (C) 2003 Massachusetts Institute of Technology.
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48 <a name="Memory-Allocation"></a>
49 <p>
50 Previous:&nbsp;<a rel="previous" accesskey="p" href="Precision.html#Precision">Precision</a>,
51 Up:&nbsp;<a rel="up" accesskey="u" href="Data-Types-and-Files.html#Data-Types-and-Files">Data Types and Files</a>
52 <hr>
53 </div>
54
55 <h4 class="subsection">4.1.3 Memory Allocation</h4>
56
57 <pre class="example"> void *fftw_malloc(size_t n);
58 void fftw_free(void *p);
59 </pre>
60 <p><a name="index-fftw_005fmalloc-145"></a><a name="index-fftw_005ffree-146"></a>
61 These are functions that behave identically to <code>malloc</code> and
62 <code>free</code>, except that they guarantee that the returned pointer obeys
63 any special alignment restrictions imposed by any algorithm in FFTW
64 (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>.
65 <a name="index-alignment-147"></a>
66
67 <p>Data allocated by <code>fftw_malloc</code> <em>must</em> be deallocated by
68 <code>fftw_free</code> and not by the ordinary <code>free</code>.
69
70 <p>These routines simply call through to your operating system's
71 <code>malloc</code> or, if necessary, its aligned equivalent
72 (e.g. <code>memalign</code>), so you normally need not worry about any
73 significant time or space overhead. You are <em>not required</em> to use
74 them to allocate your data, but we strongly recommend it.
75
76 <p>Note: in C++, just as with ordinary <code>malloc</code>, you must typecast
77 the output of <code>fftw_malloc</code> to whatever pointer type you are
78 allocating.
79 <a name="index-C_002b_002b-148"></a>
80
81 <p>We also provide the following two convenience functions to allocate
82 real and complex arrays with <code>n</code> elements, which are equivalent
83 to <code>(double *) fftw_malloc(sizeof(double) * n)</code> and
84 <code>(fftw_complex *) fftw_malloc(sizeof(fftw_complex) * n)</code>,
85 respectively:
86
87 <pre class="example"> double *fftw_alloc_real(size_t n);
88 fftw_complex *fftw_alloc_complex(size_t n);
89 </pre>
90 <p><a name="index-fftw_005falloc_005freal-149"></a><a name="index-fftw_005falloc_005fcomplex-150"></a>
91 The equivalent functions in other precisions allocate arrays of <code>n</code>
92 elements in that precision. e.g. <code>fftwf_alloc_real(n)</code> is
93 equivalent to <code>(float *) fftwf_malloc(sizeof(float) * n)</code>.
94 <a name="index-precision-151"></a>
95 <!-- -->
96
97 </body></html>
98