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  • Committer: Package Import Robot
  • Author(s): Matthias Klose
  • Date: 2011-12-14 13:21:22 UTC
  • mfrom: (3.1.5 sid)
  • Revision ID: package-import@ubuntu.com-20111214132122-l4avyl2kkr7vq5aj
Tags: 3.3-1ubuntu1
* Merge with Debian; remaining changes:
  - Revert the ARM workaround.

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doc/html/Real_002ddata-DFT-Array-Format.html
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<html lang="en">
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<head>
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<title>Real-data DFT Array Format - FFTW 3.2.2</title>
 
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<title>Real-data DFT Array Format - FFTW 3.3</title>
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<meta http-equiv="Content-Type" content="text/html">
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<meta name="description" content="FFTW 3.2.2">
 
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<meta name="description" content="FFTW 3.3">
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<meta name="generator" content="makeinfo 4.13">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Basic-Interface.html#Basic-Interface" title="Basic Interface">
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<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
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<!--
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This manual is for FFTW
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(version 3.2.2, 12 July 2009).
 
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(version 3.3, 26 July 2011).
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Copyright (C) 2003 Matteo Frigo.
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<h4 class="subsection">4.3.4 Real-data DFT Array Format</h4>
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<p><a name="index-r2c_002fc2r-multi_002ddimensional-array-format-190"></a>
 
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<p><a name="index-r2c_002fc2r-multi_002ddimensional-array-format-199"></a>
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The output of a DFT of real data (r2c) contains symmetries that, in
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principle, make half of the outputs redundant (see <a href="What-FFTW-Really-Computes.html#What-FFTW-Really-Computes">What FFTW Really Computes</a>).  (Similarly for the input of an inverse c2r transform.)  In
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practice, it is not possible to entirely realize these savings in an
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any other dimension, but implementation turns out to be simpler if the
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last, contiguous, dimension is used.)
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   <p><a name="index-out_002dof_002dplace-191"></a>For an out-of-place transform, the real data is simply an array with
 
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   <p><a name="index-out_002dof_002dplace-200"></a>For an out-of-place transform, the real data is simply an array with
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physical dimensions n<sub>0</sub>&nbsp;&times;&nbsp;n<sub>1</sub>&nbsp;&times;&nbsp;n<sub>2</sub>&nbsp;&times;&nbsp;&hellip;&nbsp;&times;&nbsp;n<sub>d-1</sub> in row-major order.
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   <p><a name="index-in_002dplace-192"></a><a name="index-padding-193"></a>For an in-place transform, some complications arise since the complex data
 
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   <p><a name="index-in_002dplace-201"></a><a name="index-padding-202"></a>For an in-place transform, some complications arise since the complex data
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is slightly larger than the real data.  In this case, the final
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dimension of the real data must be <em>padded</em> with extra values to
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accommodate the size of the complex data&mdash;two extra if the last