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1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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2 <html>
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3 <!-- This manual is for FFTW
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4 (version 3.3.8, 24 May 2018).
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5
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6 Copyright (C) 2003 Matteo Frigo.
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7
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8 Copyright (C) 2003 Massachusetts Institute of Technology.
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9
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10 Permission is granted to make and distribute verbatim copies of this
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11 manual provided the copyright notice and this permission notice are
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12 preserved on all copies.
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13
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14 Permission is granted to copy and distribute modified versions of this
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15 manual under the conditions for verbatim copying, provided that the
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16 entire resulting derived work is distributed under the terms of a
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17 permission notice identical to this one.
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18
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19 Permission is granted to copy and distribute translations of this manual
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20 into another language, under the above conditions for modified versions,
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21 except that this permission notice may be stated in a translation
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22 approved by the Free Software Foundation. -->
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23 <!-- Created by GNU Texinfo 6.3, http://www.gnu.org/software/texinfo/ -->
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24 <head>
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25 <title>FFTW 3.3.8: Memory Allocation</title>
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26
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27 <meta name="description" content="FFTW 3.3.8: Memory Allocation">
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33 <link href="index.html#Top" rel="start" title="Top">
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34 <link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
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35 <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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36 <link href="Data-Types-and-Files.html#Data-Types-and-Files" rel="up" title="Data Types and Files">
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37 <link href="Using-Plans.html#Using-Plans" rel="next" title="Using Plans">
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38 <link href="Precision.html#Precision" rel="prev" title="Precision">
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40 <!--
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63 ul.no-bullet {list-style: none}
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64 -->
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65 </style>
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66
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67
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68 </head>
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69
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70 <body lang="en">
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71 <a name="Memory-Allocation"></a>
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72 <div class="header">
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73 <p>
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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> [<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>
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75 </div>
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76 <hr>
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77 <a name="Memory-Allocation-1"></a>
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78 <h4 class="subsection">4.1.3 Memory Allocation</h4>
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79
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80 <div class="example">
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81 <pre class="example">void *fftw_malloc(size_t n);
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82 void fftw_free(void *p);
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83 </pre></div>
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84 <a name="index-fftw_005fmalloc-3"></a>
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85 <a name="index-fftw_005ffree-2"></a>
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86
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87 <p>These are functions that behave identically to <code>malloc</code> and
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88 <code>free</code>, except that they guarantee that the returned pointer obeys
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89 any special alignment restrictions imposed by any algorithm in FFTW
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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>.
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91 <a name="index-alignment"></a>
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92 </p>
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93
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94 <p>Data allocated by <code>fftw_malloc</code> <em>must</em> be deallocated by
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95 <code>fftw_free</code> and not by the ordinary <code>free</code>.
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96 </p>
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97 <p>These routines simply call through to your operating system’s
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98 <code>malloc</code> or, if necessary, its aligned equivalent
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99 (e.g. <code>memalign</code>), so you normally need not worry about any
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100 significant time or space overhead. You are <em>not required</em> to use
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101 them to allocate your data, but we strongly recommend it.
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102 </p>
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103 <p>Note: in C++, just as with ordinary <code>malloc</code>, you must typecast
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104 the output of <code>fftw_malloc</code> to whatever pointer type you are
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105 allocating.
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106 <a name="index-C_002b_002b-4"></a>
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107 </p>
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108
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109 <p>We also provide the following two convenience functions to allocate
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110 real and complex arrays with <code>n</code> elements, which are equivalent
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111 to <code>(double *) fftw_malloc(sizeof(double) * n)</code> and
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112 <code>(fftw_complex *) fftw_malloc(sizeof(fftw_complex) * n)</code>,
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113 respectively:
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114 </p>
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115 <div class="example">
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116 <pre class="example">double *fftw_alloc_real(size_t n);
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117 fftw_complex *fftw_alloc_complex(size_t n);
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118 </pre></div>
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119 <a name="index-fftw_005falloc_005freal-1"></a>
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120 <a name="index-fftw_005falloc_005fcomplex-2"></a>
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121
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122 <p>The equivalent functions in other precisions allocate arrays of <code>n</code>
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123 elements in that precision. e.g. <code>fftwf_alloc_real(n)</code> is
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124 equivalent to <code>(float *) fftwf_malloc(sizeof(float) * n)</code>.
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125 <a name="index-precision-4"></a>
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126 </p>
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127
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128
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129
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130 </body>
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131 </html>
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