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