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Add null config files
author Chris Cannam <cannam@all-day-breakfast.com>
date Mon, 02 Mar 2020 14:03:47 +0000
parents 7867fa7e1b6b
children
rev   line source
cannam@127 1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
cannam@127 2 <html>
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 10 Permission is granted to make and distribute verbatim copies of this
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cannam@127 14 Permission is granted to copy and distribute modified versions of this
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cannam@127 23 <!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ -->
cannam@127 24 <head>
cannam@127 25 <title>FFTW 3.3.5: Column-major Format</title>
cannam@127 26
cannam@127 27 <meta name="description" content="FFTW 3.3.5: Column-major Format">
cannam@127 28 <meta name="keywords" content="FFTW 3.3.5: Column-major Format">
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cannam@127 35 <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
cannam@127 36 <link href="Multi_002ddimensional-Array-Format.html#Multi_002ddimensional-Array-Format" rel="up" title="Multi-dimensional Array Format">
cannam@127 37 <link href="Fixed_002dsize-Arrays-in-C.html#Fixed_002dsize-Arrays-in-C" rel="next" title="Fixed-size Arrays in C">
cannam@127 38 <link href="Row_002dmajor-Format.html#Row_002dmajor-Format" rel="prev" title="Row-major Format">
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cannam@127 69 </head>
cannam@127 70
cannam@127 71 <body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
cannam@127 72 <a name="Column_002dmajor-Format"></a>
cannam@127 73 <div class="header">
cannam@127 74 <p>
cannam@127 75 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>
cannam@127 76 </div>
cannam@127 77 <hr>
cannam@127 78 <a name="Column_002dmajor-Format-1"></a>
cannam@127 79 <h4 class="subsection">3.2.2 Column-major Format</h4>
cannam@127 80 <a name="index-column_002dmajor"></a>
cannam@127 81
cannam@127 82 <p>Readers from the Fortran world are used to arrays stored in
cannam@127 83 <em>column-major</em> order (sometimes called &ldquo;Fortran order&rdquo;). This is
cannam@127 84 essentially the exact opposite of row-major order in that, here, the
cannam@127 85 <em>first</em> dimension&rsquo;s index varies most quickly.
cannam@127 86 </p>
cannam@127 87 <p>If you have an array stored in column-major order and wish to
cannam@127 88 transform it using FFTW, it is quite easy to do. When creating the
cannam@127 89 plan, simply pass the dimensions of the array to the planner in
cannam@127 90 <em>reverse order</em>. For example, if your array is a rank three
cannam@127 91 <code>N x M x L</code> matrix in column-major order, you should pass the
cannam@127 92 dimensions of the array as if it were an <code>L x M x N</code> matrix
cannam@127 93 (which it is, from the perspective of FFTW). This is done for you
cannam@127 94 <em>automatically</em> by the FFTW legacy-Fortran interface
cannam@127 95 (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
cannam@127 96 manually with the modern Fortran interface (see <a href="Reversing-array-dimensions.html#Reversing-array-dimensions">Reversing array dimensions</a>).
cannam@127 97 <a name="index-Fortran-interface"></a>
cannam@127 98 </p>
cannam@127 99
cannam@127 100
cannam@127 101
cannam@127 102 </body>
cannam@127 103 </html>