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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 3.3.5, 30 July 2016).
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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 5.2, http://www.gnu.org/software/texinfo/ -->
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24 <head>
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25 <title>FFTW 3.3.5: Multi-threaded FFTW</title>
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26
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27 <meta name="description" content="FFTW 3.3.5: Multi-threaded FFTW">
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28 <meta name="keywords" content="FFTW 3.3.5: Multi-threaded FFTW">
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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="index.html#Top" rel="up" title="Top">
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37 <link href="Installation-and-Supported-Hardware_002fSoftware.html#Installation-and-Supported-Hardware_002fSoftware" rel="next" title="Installation and Supported Hardware/Software">
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38 <link href="Multi_002ddimensional-Transforms.html#Multi_002ddimensional-Transforms" rel="prev" title="Multi-dimensional Transforms">
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65 -->
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66 </style>
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67
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68
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69 </head>
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70
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71 <body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
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72 <a name="Multi_002dthreaded-FFTW"></a>
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73 <div class="header">
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74 <p>
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75 Next: <a href="Distributed_002dmemory-FFTW-with-MPI.html#Distributed_002dmemory-FFTW-with-MPI" accesskey="n" rel="next">Distributed-memory FFTW with MPI</a>, Previous: <a href="FFTW-Reference.html#FFTW-Reference" accesskey="p" rel="prev">FFTW Reference</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</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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76 </div>
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77 <hr>
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78 <a name="Multi_002dthreaded-FFTW-1"></a>
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79 <h2 class="chapter">5 Multi-threaded FFTW</h2>
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80
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81 <a name="index-parallel-transform"></a>
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82 <p>In this chapter we document the parallel FFTW routines for
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83 shared-memory parallel hardware. These routines, which support
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84 parallel one- and multi-dimensional transforms of both real and
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85 complex data, are the easiest way to take advantage of multiple
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86 processors with FFTW. They work just like the corresponding
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87 uniprocessor transform routines, except that you have an extra
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88 initialization routine to call, and there is a routine to set the
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89 number of threads to employ. Any program that uses the uniprocessor
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90 FFTW can therefore be trivially modified to use the multi-threaded
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91 FFTW.
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92 </p>
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93 <p>A shared-memory machine is one in which all CPUs can directly access
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94 the same main memory, and such machines are now common due to the
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95 ubiquity of multi-core CPUs. FFTW’s multi-threading support allows
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96 you to utilize these additional CPUs transparently from a single
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97 program. However, this does not necessarily translate into
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98 performance gains—when multiple threads/CPUs are employed, there is
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99 an overhead required for synchronization that may outweigh the
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100 computatational parallelism. Therefore, you can only benefit from
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101 threads if your problem is sufficiently large.
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102 <a name="index-shared_002dmemory"></a>
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103 <a name="index-threads"></a>
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104 </p>
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105 <table class="menu" border="0" cellspacing="0">
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106 <tr><td align="left" valign="top">• <a href="Installation-and-Supported-Hardware_002fSoftware.html#Installation-and-Supported-Hardware_002fSoftware" accesskey="1">Installation and Supported Hardware/Software</a>:</td><td> </td><td align="left" valign="top">
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107 </td></tr>
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108 <tr><td align="left" valign="top">• <a href="Usage-of-Multi_002dthreaded-FFTW.html#Usage-of-Multi_002dthreaded-FFTW" accesskey="2">Usage of Multi-threaded FFTW</a>:</td><td> </td><td align="left" valign="top">
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109 </td></tr>
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110 <tr><td align="left" valign="top">• <a href="How-Many-Threads-to-Use_003f.html#How-Many-Threads-to-Use_003f" accesskey="3">How Many Threads to Use?</a>:</td><td> </td><td align="left" valign="top">
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111 </td></tr>
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112 <tr><td align="left" valign="top">• <a href="Thread-safety.html#Thread-safety" accesskey="4">Thread safety</a>:</td><td> </td><td align="left" valign="top">
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113 </td></tr>
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114 </table>
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115
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116
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117
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118
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119 </body>
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120 </html>
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