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diff src/fftw-3.3.3/doc/html/Using-Plans.html @ 10:37bf6b4a2645
Add FFTW3
| author | Chris Cannam |
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| date | Wed, 20 Mar 2013 15:35:50 +0000 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/fftw-3.3.3/doc/html/Using-Plans.html Wed Mar 20 15:35:50 2013 +0000 @@ -0,0 +1,147 @@ +<html lang="en"> +<head> +<title>Using Plans - 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="FFTW-Reference.html#FFTW-Reference" title="FFTW Reference"> +<link rel="prev" href="Data-Types-and-Files.html#Data-Types-and-Files" title="Data Types and Files"> +<link rel="next" href="Basic-Interface.html#Basic-Interface" title="Basic Interface"> +<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="Using-Plans"></a> +<p> +Next: <a rel="next" accesskey="n" href="Basic-Interface.html#Basic-Interface">Basic Interface</a>, +Previous: <a rel="previous" accesskey="p" href="Data-Types-and-Files.html#Data-Types-and-Files">Data Types and Files</a>, +Up: <a rel="up" accesskey="u" href="FFTW-Reference.html#FFTW-Reference">FFTW Reference</a> +<hr> +</div> + +<h3 class="section">4.2 Using Plans</h3> + +<p>Plans for all transform types in FFTW are stored as type +<code>fftw_plan</code> (an opaque pointer type), and are created by one of the +various planning routines described in the following sections. +<a name="index-fftw_005fplan-152"></a>An <code>fftw_plan</code> contains all information necessary to compute the +transform, including the pointers to the input and output arrays. + +<pre class="example"> void fftw_execute(const fftw_plan plan); +</pre> + <p><a name="index-fftw_005fexecute-153"></a> +This executes the <code>plan</code>, to compute the corresponding transform on +the arrays for which it was planned (which must still exist). The plan +is not modified, and <code>fftw_execute</code> can be called as many times as +desired. + + <p>To apply a given plan to a different array, you can use the new-array execute +interface. See <a href="New_002darray-Execute-Functions.html#New_002darray-Execute-Functions">New-array Execute Functions</a>. + + <p><code>fftw_execute</code> (and equivalents) is the only function in FFTW +guaranteed to be thread-safe; see <a href="Thread-safety.html#Thread-safety">Thread safety</a>. + + <p>This function: +<pre class="example"> void fftw_destroy_plan(fftw_plan plan); +</pre> + <p><a name="index-fftw_005fdestroy_005fplan-154"></a>deallocates the <code>plan</code> and all its associated data. + + <p>FFTW's planner saves some other persistent data, such as the +accumulated wisdom and a list of algorithms available in the current +configuration. If you want to deallocate all of that and reset FFTW +to the pristine state it was in when you started your program, you can +call: + +<pre class="example"> void fftw_cleanup(void); +</pre> + <p><a name="index-fftw_005fcleanup-155"></a> +After calling <code>fftw_cleanup</code>, all existing plans become undefined, +and you should not attempt to execute them nor to destroy them. You can +however create and execute/destroy new plans, in which case FFTW starts +accumulating wisdom information again. + + <p><code>fftw_cleanup</code> does not deallocate your plans, however. To prevent +memory leaks, you must still call <code>fftw_destroy_plan</code> before +executing <code>fftw_cleanup</code>. + + <p>Occasionally, it may useful to know FFTW's internal “cost” metric +that it uses to compare plans to one another; this cost is +proportional to an execution time of the plan, in undocumented units, +if the plan was created with the <code>FFTW_MEASURE</code> or other +timing-based options, or alternatively is a heuristic cost function +for <code>FFTW_ESTIMATE</code> plans. (The cost values of measured and +estimated plans are not comparable, being in different units. Also, +costs from different FFTW versions or the same version compiled +differently may not be in the same units. Plans created from wisdom +have a cost of 0 since no timing measurement is performed for them. +Finally, certain problems for which only one top-level algorithm was +possible may have required no measurements of the cost of the whole +plan, in which case <code>fftw_cost</code> will also return 0.) The cost +metric for a given plan is returned by: + +<pre class="example"> double fftw_cost(const fftw_plan plan); +</pre> + <p><a name="index-fftw_005fcost-156"></a> +The following two routines are provided purely for academic purposes +(that is, for entertainment). + +<pre class="example"> void fftw_flops(const fftw_plan plan, + double *add, double *mul, double *fma); +</pre> + <p><a name="index-fftw_005fflops-157"></a> +Given a <code>plan</code>, set <code>add</code>, <code>mul</code>, and <code>fma</code> to an +exact count of the number of floating-point additions, multiplications, +and fused multiply-add operations involved in the plan's execution. The +total number of floating-point operations (flops) is <code>add + mul + +2*fma</code>, or <code>add + mul + fma</code> if the hardware supports fused +multiply-add instructions (although the number of FMA operations is only +approximate because of compiler voodoo). (The number of operations +should be an integer, but we use <code>double</code> to avoid overflowing +<code>int</code> for large transforms; the arguments are of type <code>double</code> +even for single and long-double precision versions of FFTW.) + +<pre class="example"> void fftw_fprint_plan(const fftw_plan plan, FILE *output_file); + void fftw_print_plan(const fftw_plan plan); +</pre> + <p><a name="index-fftw_005ffprint_005fplan-158"></a><a name="index-fftw_005fprint_005fplan-159"></a> +This outputs a “nerd-readable” representation of the <code>plan</code> to +the given file or to <code>stdout</code>, respectively. + +<!-- --> + </body></html> +