Mercurial > hg > sv-dependency-builds
diff src/fftw-3.3.8/doc/html/Planner-Flags.html @ 82:d0c2a83c1364
Add FFTW 3.3.8 source, and a Linux build
| author | Chris Cannam |
|---|---|
| date | Tue, 19 Nov 2019 14:52:55 +0000 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/fftw-3.3.8/doc/html/Planner-Flags.html Tue Nov 19 14:52:55 2019 +0000 @@ -0,0 +1,218 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- This manual is for FFTW +(version 3.3.8, 24 May 2018). + +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. --> +<!-- Created by GNU Texinfo 6.3, http://www.gnu.org/software/texinfo/ --> +<head> +<title>FFTW 3.3.8: Planner Flags</title> + +<meta name="description" content="FFTW 3.3.8: Planner Flags"> +<meta name="keywords" content="FFTW 3.3.8: Planner Flags"> +<meta name="resource-type" content="document"> +<meta name="distribution" content="global"> +<meta name="Generator" content="makeinfo"> +<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> +<link href="index.html#Top" rel="start" title="Top"> +<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="Basic-Interface.html#Basic-Interface" rel="up" title="Basic Interface"> +<link href="Real_002ddata-DFTs.html#Real_002ddata-DFTs" rel="next" title="Real-data DFTs"> +<link href="Complex-DFTs.html#Complex-DFTs" rel="prev" title="Complex DFTs"> +<style type="text/css"> +<!-- +a.summary-letter {text-decoration: none} +blockquote.indentedblock {margin-right: 0em} +blockquote.smallindentedblock {margin-right: 0em; font-size: smaller} +blockquote.smallquotation {font-size: smaller} +div.display {margin-left: 3.2em} +div.example {margin-left: 3.2em} +div.lisp {margin-left: 3.2em} +div.smalldisplay {margin-left: 3.2em} +div.smallexample {margin-left: 3.2em} +div.smalllisp {margin-left: 3.2em} +kbd {font-style: oblique} +pre.display {font-family: inherit} +pre.format {font-family: inherit} +pre.menu-comment {font-family: serif} +pre.menu-preformatted {font-family: serif} +pre.smalldisplay {font-family: inherit; font-size: smaller} +pre.smallexample {font-size: smaller} +pre.smallformat {font-family: inherit; font-size: smaller} +pre.smalllisp {font-size: smaller} +span.nolinebreak {white-space: nowrap} +span.roman {font-family: initial; font-weight: normal} +span.sansserif {font-family: sans-serif; font-weight: normal} +ul.no-bullet {list-style: none} +--> +</style> + + +</head> + +<body lang="en"> +<a name="Planner-Flags"></a> +<div class="header"> +<p> +Next: <a href="Real_002ddata-DFTs.html#Real_002ddata-DFTs" accesskey="n" rel="next">Real-data DFTs</a>, Previous: <a href="Complex-DFTs.html#Complex-DFTs" accesskey="p" rel="prev">Complex DFTs</a>, Up: <a href="Basic-Interface.html#Basic-Interface" accesskey="u" rel="up">Basic Interface</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p> +</div> +<hr> +<a name="Planner-Flags-1"></a> +<h4 class="subsection">4.3.2 Planner Flags</h4> + +<p>All of the planner routines in FFTW accept an integer <code>flags</code> +argument, which is a bitwise OR (‘<samp>|</samp>’) of zero or more of the flag +constants defined below. These flags control the rigor (and time) of +the planning process, and can also impose (or lift) restrictions on the +type of transform algorithm that is employed. +</p> +<p><em>Important:</em> the planner overwrites the input array during +planning unless a saved plan (see <a href="Wisdom.html#Wisdom">Wisdom</a>) is available for that +problem, so you should initialize your input data after creating the +plan. The only exceptions to this are the <code>FFTW_ESTIMATE</code> and +<code>FFTW_WISDOM_ONLY</code> flags, as mentioned below. +</p> +<p>In all cases, if wisdom is available for the given problem that was +created with equal-or-greater planning rigor, then the more rigorous +wisdom is used. For example, in <code>FFTW_ESTIMATE</code> mode any available +wisdom is used, whereas in <code>FFTW_PATIENT</code> mode only wisdom created +in patient or exhaustive mode can be used. See <a href="Words-of-Wisdom_002dSaving-Plans.html#Words-of-Wisdom_002dSaving-Plans">Words of Wisdom-Saving Plans</a>. +</p> +<a name="Planning_002drigor-flags"></a> +<h4 class="subsubheading">Planning-rigor flags</h4> +<ul> +<li> <a name="index-FFTW_005fESTIMATE-2"></a> +<code>FFTW_ESTIMATE</code> specifies that, instead of actual measurements of +different algorithms, a simple heuristic is used to pick a (probably +sub-optimal) plan quickly. With this flag, the input/output arrays are +not overwritten during planning. + +</li><li> <a name="index-FFTW_005fMEASURE-2"></a> +<code>FFTW_MEASURE</code> tells FFTW to find an optimized plan by actually +<em>computing</em> several FFTs and measuring their execution time. +Depending on your machine, this can take some time (often a few +seconds). <code>FFTW_MEASURE</code> is the default planning option. + +</li><li> <a name="index-FFTW_005fPATIENT-2"></a> +<code>FFTW_PATIENT</code> is like <code>FFTW_MEASURE</code>, but considers a wider +range of algorithms and often produces a “more optimal” plan +(especially for large transforms), but at the expense of several times +longer planning time (especially for large transforms). + +</li><li> <a name="index-FFTW_005fEXHAUSTIVE-1"></a> +<code>FFTW_EXHAUSTIVE</code> is like <code>FFTW_PATIENT</code>, but considers an +even wider range of algorithms, including many that we think are +unlikely to be fast, to produce the most optimal plan but with a +substantially increased planning time. + +</li><li> <a name="index-FFTW_005fWISDOM_005fONLY"></a> +<code>FFTW_WISDOM_ONLY</code> is a special planning mode in which the plan +is only created if wisdom is available for the given problem, and +otherwise a <code>NULL</code> plan is returned. This can be combined with +other flags, e.g. ‘<samp>FFTW_WISDOM_ONLY | FFTW_PATIENT</samp>’ creates a +plan only if wisdom is available that was created in +<code>FFTW_PATIENT</code> or <code>FFTW_EXHAUSTIVE</code> mode. The +<code>FFTW_WISDOM_ONLY</code> flag is intended for users who need to detect +whether wisdom is available; for example, if wisdom is not available +one may wish to allocate new arrays for planning so that user data is +not overwritten. + +</li></ul> + +<a name="Algorithm_002drestriction-flags"></a> +<h4 class="subsubheading">Algorithm-restriction flags</h4> +<ul> +<li> <a name="index-FFTW_005fDESTROY_005fINPUT"></a> +<code>FFTW_DESTROY_INPUT</code> specifies that an out-of-place transform is +allowed to <em>overwrite its input</em> array with arbitrary data; this +can sometimes allow more efficient algorithms to be employed. +<a name="index-out_002dof_002dplace"></a> + +</li><li> <a name="index-FFTW_005fPRESERVE_005fINPUT-1"></a> +<code>FFTW_PRESERVE_INPUT</code> specifies that an out-of-place transform must +<em>not change its input</em> array. This is ordinarily the +<em>default</em>, except for c2r and hc2r (i.e. complex-to-real) +transforms for which <code>FFTW_DESTROY_INPUT</code> is the default. In the +latter cases, passing <code>FFTW_PRESERVE_INPUT</code> will attempt to use +algorithms that do not destroy the input, at the expense of worse +performance; for multi-dimensional c2r transforms, however, no +input-preserving algorithms are implemented and the planner will return +<code>NULL</code> if one is requested. +<a name="index-c2r-1"></a> +<a name="index-hc2r-1"></a> + +</li><li> <a name="index-FFTW_005fUNALIGNED"></a> +<a name="index-alignment-1"></a> +<a name="index-fftw_005fmalloc-4"></a> +<a name="index-fftw_005falignment_005fof"></a> +<code>FFTW_UNALIGNED</code> specifies that the algorithm may not impose any +unusual alignment requirements on the input/output arrays (i.e. no +SIMD may be used). This flag is normally <em>not necessary</em>, since +the planner automatically detects misaligned arrays. The only use for +this flag is if you want to use the new-array execute interface to +execute a given plan on a different array that may not be aligned like +the original. (Using <code>fftw_malloc</code> makes this flag unnecessary +even then. You can also use <code>fftw_alignment_of</code> to detect +whether two arrays are equivalently aligned.) + +</li></ul> + +<a name="Limiting-planning-time"></a> +<h4 class="subsubheading">Limiting planning time</h4> + +<div class="example"> +<pre class="example">extern void fftw_set_timelimit(double seconds); +</pre></div> +<a name="index-fftw_005fset_005ftimelimit"></a> + +<p>This function instructs FFTW to spend at most <code>seconds</code> seconds +(approximately) in the planner. If <code>seconds == +FFTW_NO_TIMELIMIT</code> (the default value, which is negative), then +planning time is unbounded. Otherwise, FFTW plans with a +progressively wider range of algorithms until the the given time limit +is reached or the given range of algorithms is explored, returning the +best available plan. +<a name="index-FFTW_005fNO_005fTIMELIMIT"></a> +</p> + +<p>For example, specifying <code>FFTW_PATIENT</code> first plans in +<code>FFTW_ESTIMATE</code> mode, then in <code>FFTW_MEASURE</code> mode, then +finally (time permitting) in <code>FFTW_PATIENT</code>. If +<code>FFTW_EXHAUSTIVE</code> is specified instead, the planner will further +progress to <code>FFTW_EXHAUSTIVE</code> mode. +</p> +<p>Note that the <code>seconds</code> argument specifies only a rough limit; in +practice, the planner may use somewhat more time if the time limit is +reached when the planner is in the middle of an operation that cannot +be interrupted. At the very least, the planner will complete planning +in <code>FFTW_ESTIMATE</code> mode (which is thus equivalent to a time limit +of 0). +</p> + +<hr> +<div class="header"> +<p> +Next: <a href="Real_002ddata-DFTs.html#Real_002ddata-DFTs" accesskey="n" rel="next">Real-data DFTs</a>, Previous: <a href="Complex-DFTs.html#Complex-DFTs" accesskey="p" rel="prev">Complex DFTs</a>, Up: <a href="Basic-Interface.html#Basic-Interface" accesskey="u" rel="up">Basic Interface</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p> +</div> + + + +</body> +</html>