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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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Chris@82 1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
Chris@82 2 <html>
Chris@82 3 <!-- This manual is for FFTW
Chris@82 4 (version 3.3.8, 24 May 2018).
Chris@82 5
Chris@82 6 Copyright (C) 2003 Matteo Frigo.
Chris@82 7
Chris@82 8 Copyright (C) 2003 Massachusetts Institute of Technology.
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Chris@82 10 Permission is granted to make and distribute verbatim copies of this
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Chris@82 12 preserved on all copies.
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Chris@82 14 Permission is granted to copy and distribute modified versions of this
Chris@82 15 manual under the conditions for verbatim copying, provided that the
Chris@82 16 entire resulting derived work is distributed under the terms of a
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Chris@82 22 approved by the Free Software Foundation. -->
Chris@82 23 <!-- Created by GNU Texinfo 6.3, http://www.gnu.org/software/texinfo/ -->
Chris@82 24 <head>
Chris@82 25 <title>FFTW 3.3.8: Column-major Format</title>
Chris@82 26
Chris@82 27 <meta name="description" content="FFTW 3.3.8: Column-major Format">
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Chris@82 33 <link href="index.html#Top" rel="start" title="Top">
Chris@82 34 <link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
Chris@82 35 <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
Chris@82 36 <link href="Multi_002ddimensional-Array-Format.html#Multi_002ddimensional-Array-Format" rel="up" title="Multi-dimensional Array Format">
Chris@82 37 <link href="Fixed_002dsize-Arrays-in-C.html#Fixed_002dsize-Arrays-in-C" rel="next" title="Fixed-size Arrays in C">
Chris@82 38 <link href="Row_002dmajor-Format.html#Row_002dmajor-Format" rel="prev" title="Row-major Format">
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Chris@82 66
Chris@82 67
Chris@82 68 </head>
Chris@82 69
Chris@82 70 <body lang="en">
Chris@82 71 <a name="Column_002dmajor-Format"></a>
Chris@82 72 <div class="header">
Chris@82 73 <p>
Chris@82 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>
Chris@82 75 </div>
Chris@82 76 <hr>
Chris@82 77 <a name="Column_002dmajor-Format-1"></a>
Chris@82 78 <h4 class="subsection">3.2.2 Column-major Format</h4>
Chris@82 79 <a name="index-column_002dmajor"></a>
Chris@82 80
Chris@82 81 <p>Readers from the Fortran world are used to arrays stored in
Chris@82 82 <em>column-major</em> order (sometimes called &ldquo;Fortran order&rdquo;). This is
Chris@82 83 essentially the exact opposite of row-major order in that, here, the
Chris@82 84 <em>first</em> dimension&rsquo;s index varies most quickly.
Chris@82 85 </p>
Chris@82 86 <p>If you have an array stored in column-major order and wish to
Chris@82 87 transform it using FFTW, it is quite easy to do. When creating the
Chris@82 88 plan, simply pass the dimensions of the array to the planner in
Chris@82 89 <em>reverse order</em>. For example, if your array is a rank three
Chris@82 90 <code>N x M x L</code> matrix in column-major order, you should pass the
Chris@82 91 dimensions of the array as if it were an <code>L x M x N</code> matrix
Chris@82 92 (which it is, from the perspective of FFTW). This is done for you
Chris@82 93 <em>automatically</em> by the FFTW legacy-Fortran interface
Chris@82 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
Chris@82 95 manually with the modern Fortran interface (see <a href="Reversing-array-dimensions.html#Reversing-array-dimensions">Reversing array dimensions</a>).
Chris@82 96 <a name="index-Fortran-interface"></a>
Chris@82 97 </p>
Chris@82 98
Chris@82 99
Chris@82 100
Chris@82 101 </body>
Chris@82 102 </html>