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Current fftw source
author Chris Cannam
date Tue, 18 Oct 2016 13:40:26 +0100
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Chris@42 1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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Chris@42 3 <!-- This manual is for FFTW
Chris@42 4 (version 3.3.5, 30 July 2016).
Chris@42 5
Chris@42 6 Copyright (C) 2003 Matteo Frigo.
Chris@42 7
Chris@42 8 Copyright (C) 2003 Massachusetts Institute of Technology.
Chris@42 9
Chris@42 10 Permission is granted to make and distribute verbatim copies of this
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Chris@42 24 <head>
Chris@42 25 <title>FFTW 3.3.5: 64-bit Guru Interface</title>
Chris@42 26
Chris@42 27 <meta name="description" content="FFTW 3.3.5: 64-bit Guru Interface">
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Chris@42 35 <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
Chris@42 36 <link href="Guru-Interface.html#Guru-Interface" rel="up" title="Guru Interface">
Chris@42 37 <link href="New_002darray-Execute-Functions.html#New_002darray-Execute-Functions" rel="next" title="New-array Execute Functions">
Chris@42 38 <link href="Guru-Real_002dto_002dreal-Transforms.html#Guru-Real_002dto_002dreal-Transforms" rel="prev" title="Guru Real-to-real Transforms">
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Chris@42 69 </head>
Chris@42 70
Chris@42 71 <body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
Chris@42 72 <a name="g_t64_002dbit-Guru-Interface"></a>
Chris@42 73 <div class="header">
Chris@42 74 <p>
Chris@42 75 Previous: <a href="Guru-Real_002dto_002dreal-Transforms.html#Guru-Real_002dto_002dreal-Transforms" accesskey="p" rel="prev">Guru Real-to-real Transforms</a>, Up: <a href="Guru-Interface.html#Guru-Interface" accesskey="u" rel="up">Guru Interface</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>
Chris@42 76 </div>
Chris@42 77 <hr>
Chris@42 78 <a name="g_t64_002dbit-Guru-Interface-1"></a>
Chris@42 79 <h4 class="subsection">4.5.6 64-bit Guru Interface</h4>
Chris@42 80 <a name="index-64_002dbit-architecture"></a>
Chris@42 81
Chris@42 82 <p>When compiled in 64-bit mode on a 64-bit architecture (where addresses
Chris@42 83 are 64 bits wide), FFTW uses 64-bit quantities internally for all
Chris@42 84 transform sizes, strides, and so on&mdash;you don&rsquo;t have to do anything
Chris@42 85 special to exploit this. However, in the ordinary FFTW interfaces,
Chris@42 86 you specify the transform size by an <code>int</code> quantity, which is
Chris@42 87 normally only 32 bits wide. This means that, even though FFTW is
Chris@42 88 using 64-bit sizes internally, you cannot specify a single transform
Chris@42 89 dimension larger than
Chris@42 90 2<sup><small>31</small></sup>&minus;1numbers.
Chris@42 91 </p>
Chris@42 92 <p>We expect that few users will require transforms larger than this, but,
Chris@42 93 for those who do, we provide a 64-bit version of the guru interface in
Chris@42 94 which all sizes are specified as integers of type <code>ptrdiff_t</code>
Chris@42 95 instead of <code>int</code>. (<code>ptrdiff_t</code> is a signed integer type
Chris@42 96 defined by the C standard to be wide enough to represent address
Chris@42 97 differences, and thus must be at least 64 bits wide on a 64-bit
Chris@42 98 machine.) We stress that there is <em>no performance advantage</em> to
Chris@42 99 using this interface&mdash;the same internal FFTW code is employed
Chris@42 100 regardless&mdash;and it is only necessary if you want to specify very
Chris@42 101 large transform sizes.
Chris@42 102 <a name="index-ptrdiff_005ft"></a>
Chris@42 103 </p>
Chris@42 104
Chris@42 105 <p>In particular, the 64-bit guru interface is a set of planner routines
Chris@42 106 that are exactly the same as the guru planner routines, except that
Chris@42 107 they are named with &lsquo;<samp>guru64</samp>&rsquo; instead of &lsquo;<samp>guru</samp>&rsquo; and they take
Chris@42 108 arguments of type <code>fftw_iodim64</code> instead of <code>fftw_iodim</code>.
Chris@42 109 For example, instead of <code>fftw_plan_guru_dft</code>, we have
Chris@42 110 <code>fftw_plan_guru64_dft</code>.
Chris@42 111 </p>
Chris@42 112 <div class="example">
Chris@42 113 <pre class="example">fftw_plan fftw_plan_guru64_dft(
Chris@42 114 int rank, const fftw_iodim64 *dims,
Chris@42 115 int howmany_rank, const fftw_iodim64 *howmany_dims,
Chris@42 116 fftw_complex *in, fftw_complex *out,
Chris@42 117 int sign, unsigned flags);
Chris@42 118 </pre></div>
Chris@42 119 <a name="index-fftw_005fplan_005fguru64_005fdft"></a>
Chris@42 120
Chris@42 121 <p>The <code>fftw_iodim64</code> type is similar to <code>fftw_iodim</code>, with the
Chris@42 122 same interpretation, except that it uses type <code>ptrdiff_t</code> instead
Chris@42 123 of type <code>int</code>.
Chris@42 124 </p>
Chris@42 125 <div class="example">
Chris@42 126 <pre class="example">typedef struct {
Chris@42 127 ptrdiff_t n;
Chris@42 128 ptrdiff_t is;
Chris@42 129 ptrdiff_t os;
Chris@42 130 } fftw_iodim64;
Chris@42 131 </pre></div>
Chris@42 132 <a name="index-fftw_005fiodim64"></a>
Chris@42 133
Chris@42 134 <p>Every other &lsquo;<samp>fftw_plan_guru</samp>&rsquo; function also has a
Chris@42 135 &lsquo;<samp>fftw_plan_guru64</samp>&rsquo; equivalent, but we do not repeat their
Chris@42 136 documentation here since they are identical to the 32-bit versions
Chris@42 137 except as noted above.
Chris@42 138 </p>
Chris@42 139 <hr>
Chris@42 140 <div class="header">
Chris@42 141 <p>
Chris@42 142 Previous: <a href="Guru-Real_002dto_002dreal-Transforms.html#Guru-Real_002dto_002dreal-Transforms" accesskey="p" rel="prev">Guru Real-to-real Transforms</a>, Up: <a href="Guru-Interface.html#Guru-Interface" accesskey="u" rel="up">Guru Interface</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>
Chris@42 143 </div>
Chris@42 144
Chris@42 145
Chris@42 146
Chris@42 147 </body>
Chris@42 148 </html>