Mercurial > hg > batch-feature-extraction-tool
view Lib/fftw-3.2.1/doc/html/Complex-Multi_002dDimensional-DFTs.html @ 9:262e084a15a9
Vectorised everything and made use of unique_ptr so there should be no more memory leaks. Hurrah for RAII
author | Geogaddi\David <d.m.ronan@qmul.ac.uk> |
---|---|
date | Wed, 12 Aug 2015 22:25:06 +0100 |
parents | 25bf17994ef1 |
children |
line wrap: on
line source
<html lang="en"> <head> <title>Complex Multi-Dimensional DFTs - FFTW 3.2.1</title> <meta http-equiv="Content-Type" content="text/html"> <meta name="description" content="FFTW 3.2.1"> <meta name="generator" content="makeinfo 4.8"> <link title="Top" rel="start" href="index.html#Top"> <link rel="up" href="Tutorial.html#Tutorial" title="Tutorial"> <link rel="prev" href="Complex-One_002dDimensional-DFTs.html#Complex-One_002dDimensional-DFTs" title="Complex One-Dimensional DFTs"> <link rel="next" href="One_002dDimensional-DFTs-of-Real-Data.html#One_002dDimensional-DFTs-of-Real-Data" title="One-Dimensional DFTs of Real Data"> <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> <!-- This manual is for FFTW (version 3.2.1, 5 February 2009). Copyright (C) 2003 Matteo Frigo. Copyright (C) 2003 Massachusetts Institute of Technology. Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation approved by the Free Software Foundation. --> <meta http-equiv="Content-Style-Type" content="text/css"> <style type="text/css"><!-- pre.display { font-family:inherit } pre.format { font-family:inherit } pre.smalldisplay { font-family:inherit; font-size:smaller } pre.smallformat { font-family:inherit; font-size:smaller } pre.smallexample { font-size:smaller } pre.smalllisp { font-size:smaller } span.sc { font-variant:small-caps } span.roman { font-family:serif; font-weight:normal; } span.sansserif { font-family:sans-serif; font-weight:normal; } --></style> </head> <body> <div class="node"> <p> <a name="Complex-Multi-Dimensional-DFTs"></a> <a name="Complex-Multi_002dDimensional-DFTs"></a> Next: <a rel="next" accesskey="n" href="One_002dDimensional-DFTs-of-Real-Data.html#One_002dDimensional-DFTs-of-Real-Data">One-Dimensional DFTs of Real Data</a>, Previous: <a rel="previous" accesskey="p" href="Complex-One_002dDimensional-DFTs.html#Complex-One_002dDimensional-DFTs">Complex One-Dimensional DFTs</a>, Up: <a rel="up" accesskey="u" href="Tutorial.html#Tutorial">Tutorial</a> <hr> </div> <h3 class="section">2.2 Complex Multi-Dimensional DFTs</h3> <p>Multi-dimensional transforms work much the same way as one-dimensional transforms: you allocate arrays of <code>fftw_complex</code> (preferably using <code>fftw_malloc</code>), create an <code>fftw_plan</code>, execute it as many times as you want with <code>fftw_execute(plan)</code>, and clean up with <code>fftw_destroy_plan(plan)</code> (and <code>fftw_free</code>). The only difference is the routine you use to create the plan: <pre class="example"> fftw_plan fftw_plan_dft_2d(int n0, int n1, fftw_complex *in, fftw_complex *out, int sign, unsigned flags); fftw_plan fftw_plan_dft_3d(int n0, int n1, int n2, fftw_complex *in, fftw_complex *out, int sign, unsigned flags); fftw_plan fftw_plan_dft(int rank, const int *n, fftw_complex *in, fftw_complex *out, int sign, unsigned flags); </pre> <p><a name="index-fftw_005fplan_005fdft_005f2d-38"></a><a name="index-fftw_005fplan_005fdft_005f3d-39"></a><a name="index-fftw_005fplan_005fdft-40"></a> These routines create plans for <code>n0</code> by <code>n1</code> two-dimensional (2d) transforms, <code>n0</code> by <code>n1</code> by <code>n2</code> 3d transforms, and arbitrary <code>rank</code>-dimensional transforms, respectively. In the <a name="index-rank-41"></a>third case, <code>n</code> is a pointer to an array <code>n[rank]</code> denoting an <code>n[0]</code> by <code>n[1]</code> by <small class="dots">...</small> by <code>n[rank-1]</code> transform. All of these transforms operate on contiguous arrays in the C-standard <dfn>row-major</dfn> order, so that the last dimension has the fastest-varying index in the array. This layout is described further in <a href="Multi_002ddimensional-Array-Format.html#Multi_002ddimensional-Array-Format">Multi-dimensional Array Format</a>. <p>You may have noticed that all the planner routines described so far have overlapping functionality. For example, you can plan a 1d or 2d transform by using <code>fftw_plan_dft</code> with a <code>rank</code> of <code>1</code> or <code>2</code>, or even by calling <code>fftw_plan_dft_3d</code> with <code>n0</code> and/or <code>n1</code> equal to <code>1</code> (with no loss in efficiency). This pattern continues, and FFTW's planning routines in general form a “partial order,” sequences of <a name="index-partial-order-42"></a>interfaces with strictly increasing generality but correspondingly greater complexity. <p><code>fftw_plan_dft</code> is the most general complex-DFT routine that we describe in this tutorial, but there are also the advanced and guru interfaces, <a name="index-advanced-interface-43"></a><a name="index-guru-interface-44"></a>which allow one to efficiently combine multiple/strided transforms into a single FFTW plan, transform a subset of a larger multi-dimensional array, and/or to handle more general complex-number formats. For more information, see <a href="FFTW-Reference.html#FFTW-Reference">FFTW Reference</a>. <!-- --> </body></html>