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Add FFTW 3.3.8 source, and a Linux build
author Chris Cannam
date Tue, 19 Nov 2019 14:52:55 +0000
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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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3 <!-- This manual is for FFTW
4 (version 3.3.8, 24 May 2018).
5
6 Copyright (C) 2003 Matteo Frigo.
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8 Copyright (C) 2003 Massachusetts Institute of Technology.
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24 <head>
25 <title>FFTW 3.3.8: Column-major Format</title>
26
27 <meta name="description" content="FFTW 3.3.8: Column-major Format">
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34 <link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
35 <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
36 <link href="Multi_002ddimensional-Array-Format.html#Multi_002ddimensional-Array-Format" rel="up" title="Multi-dimensional Array Format">
37 <link href="Fixed_002dsize-Arrays-in-C.html#Fixed_002dsize-Arrays-in-C" rel="next" title="Fixed-size Arrays in C">
38 <link href="Row_002dmajor-Format.html#Row_002dmajor-Format" rel="prev" title="Row-major Format">
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70 <body lang="en">
71 <a name="Column_002dmajor-Format"></a>
72 <div class="header">
73 <p>
74 Next: <a href="Fixed_002dsize-Arrays-in-C.html#Fixed_002dsize-Arrays-in-C" accesskey="n" rel="next">Fixed-size Arrays in C</a>, Previous: <a href="Row_002dmajor-Format.html#Row_002dmajor-Format" accesskey="p" rel="prev">Row-major Format</a>, Up: <a href="Multi_002ddimensional-Array-Format.html#Multi_002ddimensional-Array-Format" accesskey="u" rel="up">Multi-dimensional Array Format</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>
75 </div>
76 <hr>
77 <a name="Column_002dmajor-Format-1"></a>
78 <h4 class="subsection">3.2.2 Column-major Format</h4>
79 <a name="index-column_002dmajor"></a>
80
81 <p>Readers from the Fortran world are used to arrays stored in
82 <em>column-major</em> order (sometimes called &ldquo;Fortran order&rdquo;). This is
83 essentially the exact opposite of row-major order in that, here, the
84 <em>first</em> dimension&rsquo;s index varies most quickly.
85 </p>
86 <p>If you have an array stored in column-major order and wish to
87 transform it using FFTW, it is quite easy to do. When creating the
88 plan, simply pass the dimensions of the array to the planner in
89 <em>reverse order</em>. For example, if your array is a rank three
90 <code>N x M x L</code> matrix in column-major order, you should pass the
91 dimensions of the array as if it were an <code>L x M x N</code> matrix
92 (which it is, from the perspective of FFTW). This is done for you
93 <em>automatically</em> by the FFTW legacy-Fortran interface
94 (see <a href="Calling-FFTW-from-Legacy-Fortran.html#Calling-FFTW-from-Legacy-Fortran">Calling FFTW from Legacy Fortran</a>), but you must do it
95 manually with the modern Fortran interface (see <a href="Reversing-array-dimensions.html#Reversing-array-dimensions">Reversing array dimensions</a>).
96 <a name="index-Fortran-interface"></a>
97 </p>
98
99
100
101 </body>
102 </html>