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2 <head>
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3 <title>Multi-threaded FFTW - FFTW 3.3.3</title>
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4 <meta http-equiv="Content-Type" content="text/html">
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5 <meta name="description" content="FFTW 3.3.3">
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6 <meta name="generator" content="makeinfo 4.13">
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7 <link title="Top" rel="start" href="index.html#Top">
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8 <link rel="prev" href="FFTW-Reference.html#FFTW-Reference" title="FFTW Reference">
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9 <link rel="next" href="Distributed_002dmemory-FFTW-with-MPI.html#Distributed_002dmemory-FFTW-with-MPI" title="Distributed-memory FFTW with MPI">
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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 3.3.3, 25 November 2012).
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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="Multi-threaded-FFTW"></a>
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49 <a name="Multi_002dthreaded-FFTW"></a>
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50 <p>
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51 Next: <a rel="next" accesskey="n" href="Distributed_002dmemory-FFTW-with-MPI.html#Distributed_002dmemory-FFTW-with-MPI">Distributed-memory FFTW with MPI</a>,
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52 Previous: <a rel="previous" accesskey="p" href="FFTW-Reference.html#FFTW-Reference">FFTW Reference</a>,
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53 Up: <a rel="up" accesskey="u" href="index.html#Top">Top</a>
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54 <hr>
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55 </div>
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56
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57 <h2 class="chapter">5 Multi-threaded FFTW</h2>
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58
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59 <p><a name="index-parallel-transform-326"></a>In this chapter we document the parallel FFTW routines for
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60 shared-memory parallel hardware. These routines, which support
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61 parallel one- and multi-dimensional transforms of both real and
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62 complex data, are the easiest way to take advantage of multiple
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63 processors with FFTW. They work just like the corresponding
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64 uniprocessor transform routines, except that you have an extra
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65 initialization routine to call, and there is a routine to set the
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66 number of threads to employ. Any program that uses the uniprocessor
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67 FFTW can therefore be trivially modified to use the multi-threaded
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68 FFTW.
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69
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70 <p>A shared-memory machine is one in which all CPUs can directly access
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71 the same main memory, and such machines are now common due to the
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72 ubiquity of multi-core CPUs. FFTW's multi-threading support allows
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73 you to utilize these additional CPUs transparently from a single
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74 program. However, this does not necessarily translate into
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75 performance gains—when multiple threads/CPUs are employed, there is
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76 an overhead required for synchronization that may outweigh the
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77 computatational parallelism. Therefore, you can only benefit from
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78 threads if your problem is sufficiently large.
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79 <a name="index-shared_002dmemory-327"></a><a name="index-threads-328"></a>
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80
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81 <ul class="menu">
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82 <li><a accesskey="1" href="Installation-and-Supported-Hardware_002fSoftware.html#Installation-and-Supported-Hardware_002fSoftware">Installation and Supported Hardware/Software</a>
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83 <li><a accesskey="2" href="Usage-of-Multi_002dthreaded-FFTW.html#Usage-of-Multi_002dthreaded-FFTW">Usage of Multi-threaded FFTW</a>
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84 <li><a accesskey="3" href="How-Many-Threads-to-Use_003f.html#How-Many-Threads-to-Use_003f">How Many Threads to Use?</a>
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85 <li><a accesskey="4" href="Thread-safety.html#Thread-safety">Thread safety</a>
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86 </ul>
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87
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88 <!-- -->
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89 </body></html>
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90
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