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Current fftw source
author Chris Cannam <cannam@all-day-breakfast.com>
date Tue, 18 Oct 2016 13:40:26 +0100
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cannam@127 1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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cannam@127 3 <!-- This manual is for FFTW
cannam@127 4 (version 3.3.5, 30 July 2016).
cannam@127 5
cannam@127 6 Copyright (C) 2003 Matteo Frigo.
cannam@127 7
cannam@127 8 Copyright (C) 2003 Massachusetts Institute of Technology.
cannam@127 9
cannam@127 10 Permission is granted to make and distribute verbatim copies of this
cannam@127 11 manual provided the copyright notice and this permission notice are
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cannam@127 14 Permission is granted to copy and distribute modified versions of this
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cannam@127 24 <head>
cannam@127 25 <title>FFTW 3.3.5: Memory Allocation</title>
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cannam@127 69 </head>
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cannam@127 71 <body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
cannam@127 72 <a name="Memory-Allocation"></a>
cannam@127 73 <div class="header">
cannam@127 74 <p>
cannam@127 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>
cannam@127 76 </div>
cannam@127 77 <hr>
cannam@127 78 <a name="Memory-Allocation-1"></a>
cannam@127 79 <h4 class="subsection">4.1.3 Memory Allocation</h4>
cannam@127 80
cannam@127 81 <div class="example">
cannam@127 82 <pre class="example">void *fftw_malloc(size_t n);
cannam@127 83 void fftw_free(void *p);
cannam@127 84 </pre></div>
cannam@127 85 <a name="index-fftw_005fmalloc-3"></a>
cannam@127 86 <a name="index-fftw_005ffree-2"></a>
cannam@127 87
cannam@127 88 <p>These are functions that behave identically to <code>malloc</code> and
cannam@127 89 <code>free</code>, except that they guarantee that the returned pointer obeys
cannam@127 90 any special alignment restrictions imposed by any algorithm in FFTW
cannam@127 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>.
cannam@127 92 <a name="index-alignment"></a>
cannam@127 93 </p>
cannam@127 94
cannam@127 95 <p>Data allocated by <code>fftw_malloc</code> <em>must</em> be deallocated by
cannam@127 96 <code>fftw_free</code> and not by the ordinary <code>free</code>.
cannam@127 97 </p>
cannam@127 98 <p>These routines simply call through to your operating system&rsquo;s
cannam@127 99 <code>malloc</code> or, if necessary, its aligned equivalent
cannam@127 100 (e.g. <code>memalign</code>), so you normally need not worry about any
cannam@127 101 significant time or space overhead. You are <em>not required</em> to use
cannam@127 102 them to allocate your data, but we strongly recommend it.
cannam@127 103 </p>
cannam@127 104 <p>Note: in C++, just as with ordinary <code>malloc</code>, you must typecast
cannam@127 105 the output of <code>fftw_malloc</code> to whatever pointer type you are
cannam@127 106 allocating.
cannam@127 107 <a name="index-C_002b_002b-4"></a>
cannam@127 108 </p>
cannam@127 109
cannam@127 110 <p>We also provide the following two convenience functions to allocate
cannam@127 111 real and complex arrays with <code>n</code> elements, which are equivalent
cannam@127 112 to <code>(double *) fftw_malloc(sizeof(double) * n)</code> and
cannam@127 113 <code>(fftw_complex *) fftw_malloc(sizeof(fftw_complex) * n)</code>,
cannam@127 114 respectively:
cannam@127 115 </p>
cannam@127 116 <div class="example">
cannam@127 117 <pre class="example">double *fftw_alloc_real(size_t n);
cannam@127 118 fftw_complex *fftw_alloc_complex(size_t n);
cannam@127 119 </pre></div>
cannam@127 120 <a name="index-fftw_005falloc_005freal-1"></a>
cannam@127 121 <a name="index-fftw_005falloc_005fcomplex-2"></a>
cannam@127 122
cannam@127 123 <p>The equivalent functions in other precisions allocate arrays of <code>n</code>
cannam@127 124 elements in that precision. e.g. <code>fftwf_alloc_real(n)</code> is
cannam@127 125 equivalent to <code>(float *) fftwf_malloc(sizeof(float) * n)</code>.
cannam@127 126 <a name="index-precision-4"></a>
cannam@127 127 </p>
cannam@127 128
cannam@127 129
cannam@127 130
cannam@127 131 </body>
cannam@127 132 </html>