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122 lines
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122 lines
6.2 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- This manual is for FFTW
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(version 3.3.10, 10 December 2020).
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Copyright (C) 2003 Matteo Frigo.
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Copyright (C) 2003 Massachusetts Institute of Technology.
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Permission is granted to make and distribute verbatim copies of this
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manual provided the copyright notice and this permission notice are
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preserved on all copies.
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Permission is granted to copy and distribute modified versions of this
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manual under the conditions for verbatim copying, provided that the
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entire resulting derived work is distributed under the terms of a
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permission notice identical to this one.
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Permission is granted to copy and distribute translations of this manual
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into another language, under the above conditions for modified versions,
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except that this permission notice may be stated in a translation
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approved by the Free Software Foundation. -->
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<!-- Created by GNU Texinfo 6.7, http://www.gnu.org/software/texinfo/ -->
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<title>Advanced Real-data DFTs (FFTW 3.3.10)</title>
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<meta name="description" content="Advanced Real-data DFTs (FFTW 3.3.10)">
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<meta name="keywords" content="Advanced Real-data DFTs (FFTW 3.3.10)">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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<link href="index.html" rel="start" title="Top">
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<link href="Concept-Index.html" rel="index" title="Concept Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Advanced-Interface.html" rel="up" title="Advanced Interface">
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<link href="Advanced-Real_002dto_002dreal-Transforms.html" rel="next" title="Advanced Real-to-real Transforms">
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<link href="Advanced-Complex-DFTs.html" rel="prev" title="Advanced Complex DFTs">
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</style>
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</head>
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<body lang="en">
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<span id="Advanced-Real_002ddata-DFTs"></span><div class="header">
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<p>
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Next: <a href="Advanced-Real_002dto_002dreal-Transforms.html" accesskey="n" rel="next">Advanced Real-to-real Transforms</a>, Previous: <a href="Advanced-Complex-DFTs.html" accesskey="p" rel="prev">Advanced Complex DFTs</a>, Up: <a href="Advanced-Interface.html" accesskey="u" rel="up">Advanced Interface</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<span id="Advanced-Real_002ddata-DFTs-1"></span><h4 class="subsection">4.4.2 Advanced Real-data DFTs</h4>
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<div class="example">
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<pre class="example">fftw_plan fftw_plan_many_dft_r2c(int rank, const int *n, int howmany,
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double *in, const int *inembed,
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int istride, int idist,
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fftw_complex *out, const int *onembed,
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int ostride, int odist,
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unsigned flags);
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fftw_plan fftw_plan_many_dft_c2r(int rank, const int *n, int howmany,
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fftw_complex *in, const int *inembed,
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int istride, int idist,
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double *out, const int *onembed,
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int ostride, int odist,
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unsigned flags);
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</pre></div>
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<span id="index-fftw_005fplan_005fmany_005fdft_005fr2c"></span>
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<span id="index-fftw_005fplan_005fmany_005fdft_005fc2r"></span>
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<p>Like <code>fftw_plan_many_dft</code>, these two functions add <code>howmany</code>,
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<code>nembed</code>, <code>stride</code>, and <code>dist</code> parameters to the
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<code>fftw_plan_dft_r2c</code> and <code>fftw_plan_dft_c2r</code> functions, but
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otherwise behave the same as the basic interface.
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</p>
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<p>The interpretation of <code>howmany</code>, <code>stride</code>, and <code>dist</code> are
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the same as for <code>fftw_plan_many_dft</code>, above. Note that the
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<code>stride</code> and <code>dist</code> for the real array are in units of
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<code>double</code>, and for the complex array are in units of
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<code>fftw_complex</code>.
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</p>
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<p>If an <code>nembed</code> parameter is <code>NULL</code>, it is interpreted as what
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it would be in the basic interface, as described in <a href="Real_002ddata-DFT-Array-Format.html">Real-data DFT Array Format</a>. That is, for the complex array the size is assumed to be
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the same as <code>n</code>, but with the last dimension cut roughly in half.
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For the real array, the size is assumed to be <code>n</code> if the transform
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is out-of-place, or <code>n</code> with the last dimension “padded” if the
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transform is in-place.
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</p>
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<p>If an <code>nembed</code> parameter is non-<code>NULL</code>, it is interpreted as
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the physical size of the corresponding array, in row-major order, just
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as for <code>fftw_plan_many_dft</code>. In this case, each dimension of
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<code>nembed</code> should be <code>>=</code> what it would be in the basic
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interface (e.g. the halved or padded <code>n</code>).
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</p>
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<p>Arrays <code>n</code>, <code>inembed</code>, and <code>onembed</code> are not used after
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this function returns. You can safely free or reuse them.
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</p>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Advanced-Real_002dto_002dreal-Transforms.html" accesskey="n" rel="next">Advanced Real-to-real Transforms</a>, Previous: <a href="Advanced-Complex-DFTs.html" accesskey="p" rel="prev">Advanced Complex DFTs</a>, Up: <a href="Advanced-Interface.html" accesskey="u" rel="up">Advanced Interface</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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</div>
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</body>
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</html>
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