Mercurial > hg > sv-dependency-builds
diff src/fftw-3.3.3/doc/html/Row_002dmajor-Format.html @ 10:37bf6b4a2645
Add FFTW3
| author | Chris Cannam |
|---|---|
| date | Wed, 20 Mar 2013 15:35:50 +0000 |
| parents | |
| children |
line wrap: on
line diff
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/fftw-3.3.3/doc/html/Row_002dmajor-Format.html Wed Mar 20 15:35:50 2013 +0000 @@ -0,0 +1,93 @@ +<html lang="en"> +<head> +<title>Row-major Format - FFTW 3.3.3</title> +<meta http-equiv="Content-Type" content="text/html"> +<meta name="description" content="FFTW 3.3.3"> +<meta name="generator" content="makeinfo 4.13"> +<link title="Top" rel="start" href="index.html#Top"> +<link rel="up" href="Multi_002ddimensional-Array-Format.html#Multi_002ddimensional-Array-Format" title="Multi-dimensional Array Format"> +<link rel="prev" href="Multi_002ddimensional-Array-Format.html#Multi_002ddimensional-Array-Format" title="Multi-dimensional Array Format"> +<link rel="next" href="Column_002dmajor-Format.html#Column_002dmajor-Format" title="Column-major Format"> +<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> +<!-- +This manual is for FFTW +(version 3.3.3, 25 November 2012). + +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"> +<a name="Row-major-Format"></a> +<a name="Row_002dmajor-Format"></a> +<p> +Next: <a rel="next" accesskey="n" href="Column_002dmajor-Format.html#Column_002dmajor-Format">Column-major Format</a>, +Previous: <a rel="previous" accesskey="p" href="Multi_002ddimensional-Array-Format.html#Multi_002ddimensional-Array-Format">Multi-dimensional Array Format</a>, +Up: <a rel="up" accesskey="u" href="Multi_002ddimensional-Array-Format.html#Multi_002ddimensional-Array-Format">Multi-dimensional Array Format</a> +<hr> +</div> + +<h4 class="subsection">3.2.1 Row-major Format</h4> + +<p><a name="index-row_002dmajor-115"></a> +The multi-dimensional arrays passed to <code>fftw_plan_dft</code> etcetera +are expected to be stored as a single contiguous block in +<dfn>row-major</dfn> order (sometimes called “C order”). Basically, this +means that as you step through adjacent memory locations, the first +dimension's index varies most slowly and the last dimension's index +varies most quickly. + + <p>To be more explicit, let us consider an array of rank d whose +dimensions are n<sub>0</sub> × n<sub>1</sub> × n<sub>2</sub> × … × n<sub>d-1</sub>. Now, we specify a location in the array by a +sequence of d (zero-based) indices, one for each dimension: +(i<sub>0</sub>, i<sub>1</sub>, i<sub>2</sub>,..., i<sub>d-1</sub>). If the array is stored in row-major +order, then this element is located at the position +i<sub>d-1</sub> + n<sub>d-1</sub> * (i<sub>d-2</sub> + n<sub>d-2</sub> * (... + n<sub>1</sub> * i<sub>0</sub>)). + + <p>Note that, for the ordinary complex DFT, each element of the array +must be of type <code>fftw_complex</code>; i.e. a (real, imaginary) pair of +(double-precision) numbers. + + <p>In the advanced FFTW interface, the physical dimensions n from +which the indices are computed can be different from (larger than) +the logical dimensions of the transform to be computed, in order to +transform a subset of a larger array. +<a name="index-advanced-interface-116"></a>Note also that, in the advanced interface, the expression above is +multiplied by a <dfn>stride</dfn> to get the actual array index—this is +useful in situations where each element of the multi-dimensional array +is actually a data structure (or another array), and you just want to +transform a single field. In the basic interface, however, the stride +is 1. +<a name="index-stride-117"></a> +<!-- =========> --> + + </body></html> +