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1 <html lang="en">
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2 <head>
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3 <title>Memory Allocation - FFTW 3.3.4</title>
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4 <meta http-equiv="Content-Type" content="text/html">
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5 <meta name="description" content="FFTW 3.3.4">
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7 <link title="Top" rel="start" href="index.html#Top">
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8 <link rel="up" href="Data-Types-and-Files.html#Data-Types-and-Files" title="Data Types and Files">
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9 <link rel="prev" href="Precision.html#Precision" title="Precision">
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10 <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
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11 <!--
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12 This manual is for FFTW
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13 (version 3.3.4, 20 September 2013).
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14
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15 Copyright (C) 2003 Matteo Frigo.
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16
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17 Copyright (C) 2003 Massachusetts Institute of Technology.
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18
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19 Permission is granted to make and distribute verbatim copies of
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20 this manual provided the copyright notice and this permission
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21 notice are preserved on all copies.
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22
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23 Permission is granted to copy and distribute modified versions of
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24 this manual under the conditions for verbatim copying, provided
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25 that the entire resulting derived work is distributed under the
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26 terms of a permission notice identical to this one.
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27
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28 Permission is granted to copy and distribute translations of this
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29 manual into another language, under the above conditions for
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30 modified versions, except that this permission notice may be
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31 stated in a translation approved by the Free Software Foundation.
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32 -->
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44 --></style>
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45 </head>
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46 <body>
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47 <div class="node">
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48 <a name="Memory-Allocation"></a>
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49 <p>
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50 Previous: <a rel="previous" accesskey="p" href="Precision.html#Precision">Precision</a>,
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51 Up: <a rel="up" accesskey="u" href="Data-Types-and-Files.html#Data-Types-and-Files">Data Types and Files</a>
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52 <hr>
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53 </div>
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54
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55 <h4 class="subsection">4.1.3 Memory Allocation</h4>
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56
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57 <pre class="example"> void *fftw_malloc(size_t n);
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58 void fftw_free(void *p);
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59 </pre>
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60 <p><a name="index-fftw_005fmalloc-145"></a><a name="index-fftw_005ffree-146"></a>
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61 These are functions that behave identically to <code>malloc</code> and
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62 <code>free</code>, except that they guarantee that the returned pointer obeys
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63 any special alignment restrictions imposed by any algorithm in FFTW
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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>.
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65 <a name="index-alignment-147"></a>
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66
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67 <p>Data allocated by <code>fftw_malloc</code> <em>must</em> be deallocated by
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68 <code>fftw_free</code> and not by the ordinary <code>free</code>.
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69
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70 <p>These routines simply call through to your operating system's
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71 <code>malloc</code> or, if necessary, its aligned equivalent
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72 (e.g. <code>memalign</code>), so you normally need not worry about any
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73 significant time or space overhead. You are <em>not required</em> to use
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74 them to allocate your data, but we strongly recommend it.
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75
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76 <p>Note: in C++, just as with ordinary <code>malloc</code>, you must typecast
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77 the output of <code>fftw_malloc</code> to whatever pointer type you are
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78 allocating.
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79 <a name="index-C_002b_002b-148"></a>
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80
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81 <p>We also provide the following two convenience functions to allocate
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82 real and complex arrays with <code>n</code> elements, which are equivalent
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83 to <code>(double *) fftw_malloc(sizeof(double) * n)</code> and
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84 <code>(fftw_complex *) fftw_malloc(sizeof(fftw_complex) * n)</code>,
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85 respectively:
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86
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87 <pre class="example"> double *fftw_alloc_real(size_t n);
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88 fftw_complex *fftw_alloc_complex(size_t n);
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89 </pre>
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90 <p><a name="index-fftw_005falloc_005freal-149"></a><a name="index-fftw_005falloc_005fcomplex-150"></a>
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91 The equivalent functions in other precisions allocate arrays of <code>n</code>
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92 elements in that precision. e.g. <code>fftwf_alloc_real(n)</code> is
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93 equivalent to <code>(float *) fftwf_malloc(sizeof(float) * n)</code>.
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94 <a name="index-precision-151"></a>
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95 <!-- -->
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96
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97 </body></html>
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98
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