2016-05-10 15:03:32 -04:00
|
|
|
|
<!DOCTYPE html>
|
|
|
|
|
|
<html lang="en">
|
|
|
|
|
|
<head>
|
|
|
|
|
|
<meta charset="utf-8">
|
|
|
|
|
|
<meta name="viewport" content="width=device-width, initial-scale=1.0">
|
|
|
|
|
|
<meta name="generator" content="rustdoc">
|
|
|
|
|
|
<meta name="description" content="API documentation for the Rust `distance` fn in crate `hamming`.">
|
|
|
|
|
|
<meta name="keywords" content="rust, rustlang, rust-lang, distance">
|
|
|
|
|
|
|
|
|
|
|
|
<title>hamming::distance - Rust</title>
|
|
|
|
|
|
|
|
|
|
|
|
<link rel="stylesheet" type="text/css" href="../rustdoc.css">
|
|
|
|
|
|
<link rel="stylesheet" type="text/css" href="../main.css">
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
</head>
|
|
|
|
|
|
<body class="rustdoc">
|
|
|
|
|
|
<!--[if lte IE 8]>
|
|
|
|
|
|
<div class="warning">
|
|
|
|
|
|
This old browser is unsupported and will most likely display funky
|
|
|
|
|
|
things.
|
|
|
|
|
|
</div>
|
|
|
|
|
|
<![endif]-->
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<nav class="sidebar">
|
|
|
|
|
|
|
|
|
|
|
|
<p class='location'><a href='index.html'>hamming</a></p><script>window.sidebarCurrent = {name: 'distance', ty: 'fn', relpath: ''};</script><script defer src="sidebar-items.js"></script>
|
|
|
|
|
|
</nav>
|
|
|
|
|
|
|
|
|
|
|
|
<nav class="sub">
|
|
|
|
|
|
<form class="search-form js-only">
|
|
|
|
|
|
<div class="search-container">
|
|
|
|
|
|
<input class="search-input" name="search"
|
|
|
|
|
|
autocomplete="off"
|
|
|
|
|
|
placeholder="Click or press ‘S’ to search, ‘?’ for more options…"
|
|
|
|
|
|
type="search">
|
|
|
|
|
|
</div>
|
|
|
|
|
|
</form>
|
|
|
|
|
|
</nav>
|
|
|
|
|
|
|
|
|
|
|
|
<section id='main' class="content fn">
|
|
|
|
|
|
<h1 class='fqn'><span class='in-band'>Function <a href='index.html'>hamming</a>::<wbr><a class='fn' href=''>distance</a></span><span class='out-of-band'><span id='render-detail'>
|
|
|
|
|
|
<a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">
|
|
|
|
|
|
[<span class='inner'>−</span>]
|
|
|
|
|
|
</a>
|
2016-05-10 23:34:09 -04:00
|
|
|
|
</span><a id='src-178' class='srclink' href='../src/hamming/distance_.rs.html#202-206' title='goto source code'>[src]</a></span></h1>
|
2016-05-10 15:03:32 -04:00
|
|
|
|
<pre class='rust fn'>pub fn distance(x: <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.slice.html'>&[</a><a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.u8.html'>u8</a><a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.slice.html'>]</a>, y: <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.slice.html'>&[</a><a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.u8.html'>u8</a><a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.slice.html'>]</a>) -> <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.u64.html'>u64</a></pre><div class='docblock'><p>Computes the bitwise <a href="https://en.wikipedia.org/wiki/Hamming_distance">Hamming
|
|
|
|
|
|
distance</a> between
|
|
|
|
|
|
<code>x</code> and <code>y</code>, that is, the number of bits where <code>x</code> and <code>y</code> differ,
|
|
|
|
|
|
or, the number of set bits in the xor of <code>x</code> and <code>y</code>.</p>
|
|
|
|
|
|
|
|
|
|
|
|
<p>When <code>x</code> and <code>y</code> have the same 8-byte alignment, this uses
|
|
|
|
|
|
<code>distance_fast</code>, a highly optimised version of the following naive
|
|
|
|
|
|
version:</p>
|
|
|
|
|
|
|
|
|
|
|
|
<pre class='rust rust-example-rendered'>
|
|
|
|
|
|
<span class='kw'>fn</span> <span class='ident'>naive</span>(<span class='ident'>x</span>: <span class='kw-2'>&</span>[<span class='ident'>u8</span>], <span class='ident'>y</span>: <span class='kw-2'>&</span>[<span class='ident'>u8</span>]) <span class='op'>-></span> <span class='ident'>u64</span> {
|
|
|
|
|
|
<span class='ident'>x</span>.<span class='ident'>iter</span>().<span class='ident'>zip</span>(<span class='ident'>y</span>).<span class='ident'>fold</span>(<span class='number'>0</span>, <span class='op'>|</span><span class='ident'>a</span>, (<span class='ident'>b</span>, <span class='ident'>c</span>)<span class='op'>|</span> <span class='ident'>a</span> <span class='op'>+</span> (<span class='op'>*</span><span class='ident'>b</span> <span class='op'>^</span> <span class='op'>*</span><span class='ident'>c</span>).<span class='ident'>count_ones</span>() <span class='kw'>as</span> <span class='ident'>u64</span>)
|
|
|
|
|
|
}</pre>
|
|
|
|
|
|
|
|
|
|
|
|
<p>If alignments differ, a slower but less restrictive algorithm is
|
|
|
|
|
|
used.</p>
|
|
|
|
|
|
|
|
|
|
|
|
<p>It is essentially guaranteed that <code>x</code> and <code>y</code> will have the same
|
|
|
|
|
|
8-byte alignment if they are both just <code>Vec<u8></code>s of non-trivial
|
|
|
|
|
|
length (e.g. larger than 8) as in the example below.</p>
|
|
|
|
|
|
|
|
|
|
|
|
<h1 id='panics' class='section-header'><a href='#panics'>Panics</a></h1>
|
|
|
|
|
|
<p><code>x</code> and <code>y</code> must have the same length, or else <code>distance</code> panics.</p>
|
|
|
|
|
|
|
|
|
|
|
|
<h1 id='performance-comparison' class='section-header'><a href='#performance-comparison'>Performance Comparison</a></h1>
|
|
|
|
|
|
<table>
|
|
|
|
|
|
<thead>
|
|
|
|
|
|
<tr>
|
|
|
|
|
|
<th style="text-align: right">length</th>
|
|
|
|
|
|
<th style="text-align: right"><code>naive</code> (ns)</th>
|
|
|
|
|
|
<th style="text-align: right"><code>distance</code> (ns)</th>
|
|
|
|
|
|
<th style="text-align: right"><code>naive</code>/<code>distance</code></th>
|
|
|
|
|
|
</tr>
|
|
|
|
|
|
</thead>
|
|
|
|
|
|
|
|
|
|
|
|
<tbody>
|
|
|
|
|
|
<tr>
|
|
|
|
|
|
<td style="text-align: right">1</td>
|
|
|
|
|
|
<td style="text-align: right">5</td>
|
|
|
|
|
|
<td style="text-align: right">6</td>
|
|
|
|
|
|
<td style="text-align: right">0.83</td>
|
|
|
|
|
|
</tr>
|
|
|
|
|
|
<tr>
|
|
|
|
|
|
<td style="text-align: right">10</td>
|
|
|
|
|
|
<td style="text-align: right">44</td>
|
|
|
|
|
|
<td style="text-align: right">45</td>
|
|
|
|
|
|
<td style="text-align: right">0.97</td>
|
|
|
|
|
|
</tr>
|
|
|
|
|
|
<tr>
|
|
|
|
|
|
<td style="text-align: right">100</td>
|
|
|
|
|
|
<td style="text-align: right">461</td>
|
|
|
|
|
|
<td style="text-align: right">473</td>
|
|
|
|
|
|
<td style="text-align: right">0.97</td>
|
|
|
|
|
|
</tr>
|
|
|
|
|
|
<tr>
|
|
|
|
|
|
<td style="text-align: right">1,000</td>
|
|
|
|
|
|
<td style="text-align: right">4,510</td>
|
|
|
|
|
|
<td style="text-align: right">397</td>
|
|
|
|
|
|
<td style="text-align: right">11</td>
|
|
|
|
|
|
</tr>
|
|
|
|
|
|
<tr>
|
|
|
|
|
|
<td style="text-align: right">10,000</td>
|
|
|
|
|
|
<td style="text-align: right">46,700</td>
|
|
|
|
|
|
<td style="text-align: right">2,740</td>
|
|
|
|
|
|
<td style="text-align: right">17</td>
|
|
|
|
|
|
</tr>
|
|
|
|
|
|
<tr>
|
|
|
|
|
|
<td style="text-align: right">100,000</td>
|
|
|
|
|
|
<td style="text-align: right">45,600</td>
|
|
|
|
|
|
<td style="text-align: right">20,400</td>
|
|
|
|
|
|
<td style="text-align: right">22</td>
|
|
|
|
|
|
</tr>
|
|
|
|
|
|
<tr>
|
|
|
|
|
|
<td style="text-align: right">1,000,000</td>
|
|
|
|
|
|
<td style="text-align: right">4,590,000</td>
|
|
|
|
|
|
<td style="text-align: right">196,000</td>
|
|
|
|
|
|
<td style="text-align: right">23</td>
|
|
|
|
|
|
</tr>
|
|
|
|
|
|
</tbody>
|
|
|
|
|
|
</table>
|
|
|
|
|
|
|
|
|
|
|
|
<p>The benchmarks ensured that <code>x</code> and <code>y</code> had the same alignment.</p>
|
|
|
|
|
|
|
|
|
|
|
|
<h1 id='examples' class='section-header'><a href='#examples'>Examples</a></h1>
|
|
|
|
|
|
<pre class='rust rust-example-rendered'>
|
|
|
|
|
|
<span class='kw'>let</span> <span class='ident'>x</span> <span class='op'>=</span> <span class='macro'>vec</span><span class='macro'>!</span>[<span class='number'>0xFF</span>; <span class='number'>1000</span>];
|
|
|
|
|
|
<span class='kw'>let</span> <span class='ident'>y</span> <span class='op'>=</span> <span class='macro'>vec</span><span class='macro'>!</span>[<span class='number'>0</span>; <span class='number'>1000</span>];
|
|
|
|
|
|
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>hamming</span>::<span class='ident'>distance</span>(<span class='kw-2'>&</span><span class='ident'>x</span>, <span class='kw-2'>&</span><span class='ident'>y</span>), <span class='number'>8</span> <span class='op'>*</span> <span class='number'>1000</span>);</pre>
|
|
|
|
|
|
</div></section>
|
|
|
|
|
|
<section id='search' class="content hidden"></section>
|
|
|
|
|
|
|
|
|
|
|
|
<section class="footer"></section>
|
|
|
|
|
|
|
|
|
|
|
|
<aside id="help" class="hidden">
|
|
|
|
|
|
<div>
|
|
|
|
|
|
<h1 class="hidden">Help</h1>
|
|
|
|
|
|
|
|
|
|
|
|
<div class="shortcuts">
|
|
|
|
|
|
<h2>Keyboard Shortcuts</h2>
|
|
|
|
|
|
|
|
|
|
|
|
<dl>
|
|
|
|
|
|
<dt>?</dt>
|
|
|
|
|
|
<dd>Show this help dialog</dd>
|
|
|
|
|
|
<dt>S</dt>
|
|
|
|
|
|
<dd>Focus the search field</dd>
|
|
|
|
|
|
<dt>⇤</dt>
|
|
|
|
|
|
<dd>Move up in search results</dd>
|
|
|
|
|
|
<dt>⇥</dt>
|
|
|
|
|
|
<dd>Move down in search results</dd>
|
|
|
|
|
|
<dt>⏎</dt>
|
|
|
|
|
|
<dd>Go to active search result</dd>
|
|
|
|
|
|
</dl>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
|
|
|
|
|
|
<div class="infos">
|
|
|
|
|
|
<h2>Search Tricks</h2>
|
|
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
|
Prefix searches with a type followed by a colon (e.g.
|
|
|
|
|
|
<code>fn:</code>) to restrict the search to a given type.
|
|
|
|
|
|
</p>
|
|
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
|
Accepted types are: <code>fn</code>, <code>mod</code>,
|
|
|
|
|
|
<code>struct</code>, <code>enum</code>,
|
|
|
|
|
|
<code>trait</code>, <code>type</code>, <code>macro</code>,
|
|
|
|
|
|
and <code>const</code>.
|
|
|
|
|
|
</p>
|
|
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
|
Search functions by type signature (e.g.
|
|
|
|
|
|
<code>vec -> usize</code> or <code>* -> vec</code>)
|
|
|
|
|
|
</p>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
</aside>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<script>
|
|
|
|
|
|
window.rootPath = "../";
|
|
|
|
|
|
window.currentCrate = "hamming";
|
|
|
|
|
|
window.playgroundUrl = "";
|
|
|
|
|
|
</script>
|
|
|
|
|
|
<script src="../jquery.js"></script>
|
|
|
|
|
|
<script src="../main.js"></script>
|
|
|
|
|
|
|
|
|
|
|
|
<script defer src="../search-index.js"></script>
|
|
|
|
|
|
</body>
|
|
|
|
|
|
</html>
|
