File: C:/Ruby27-x64/share/doc/ruby/html/Prime/EratosthenesSieve.html
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>class Prime::EratosthenesSieve - RDoc Documentation</title>
<script type="text/javascript">
var rdoc_rel_prefix = "../";
var index_rel_prefix = "../";
</script>
<script src="../js/navigation.js" defer></script>
<script src="../js/search.js" defer></script>
<script src="../js/search_index.js" defer></script>
<script src="../js/searcher.js" defer></script>
<script src="../js/darkfish.js" defer></script>
<link href="../css/fonts.css" rel="stylesheet">
<link href="../css/rdoc.css" rel="stylesheet">
<body id="top" role="document" class="class">
<nav role="navigation">
<div id="project-navigation">
<div id="home-section" role="region" title="Quick navigation" class="nav-section">
<h2>
<a href="../index.html" rel="home">Home</a>
</h2>
<div id="table-of-contents-navigation">
<a href="../table_of_contents.html#pages">Pages</a>
<a href="../table_of_contents.html#classes">Classes</a>
<a href="../table_of_contents.html#methods">Methods</a>
</div>
</div>
<div id="search-section" role="search" class="project-section initially-hidden">
<form action="#" method="get" accept-charset="utf-8">
<div id="search-field-wrapper">
<input id="search-field" role="combobox" aria-label="Search"
aria-autocomplete="list" aria-controls="search-results"
type="text" name="search" placeholder="Search" spellcheck="false"
title="Type to search, Up and Down to navigate, Enter to load">
</div>
<ul id="search-results" aria-label="Search Results"
aria-busy="false" aria-expanded="false"
aria-atomic="false" class="initially-hidden"></ul>
</form>
</div>
</div>
<div id="class-metadata">
<div id="parent-class-section" class="nav-section">
<h3>Parent</h3>
<p class="link"><a href="../Object.html">Object</a>
</div>
<div id="includes-section" class="nav-section">
<h3>Included Modules</h3>
<ul class="link-list">
<li><a class="include" href="../Singleton.html">Singleton</a>
</ul>
</div>
<!-- Method Quickref -->
<div id="method-list-section" class="nav-section">
<h3>Methods</h3>
<ul class="link-list" role="directory">
<li ><a href="#method-c-new">::new</a>
<li ><a href="#method-i-compute_primes">#compute_primes</a>
<li ><a href="#method-i-get_nth_prime">#get_nth_prime</a>
</ul>
</div>
</div>
</nav>
<main role="main" aria-labelledby="class-Prime::EratosthenesSieve">
<h1 id="class-Prime::EratosthenesSieve" class="class">
class Prime::EratosthenesSieve
</h1>
<section class="description">
<p>Internal use. An implementation of Eratosthenes' sieve</p>
</section>
<section id="5Buntitled-5D" class="documentation-section">
<section id="public-class-5Buntitled-5D-method-details" class="method-section">
<header>
<h3>Public Class Methods</h3>
</header>
<div id="method-c-new" class="method-detail ">
<div class="method-heading">
<span class="method-name">new</span><span
class="method-args">()</span>
<span class="method-click-advice">click to toggle source</span>
</div>
<div class="method-description">
<div class="method-source-code" id="new-source">
<pre><span class="ruby-comment"># File lib/prime.rb, line 422</span>
<span class="ruby-keyword">def</span> <span class="ruby-identifier ruby-title">initialize</span>
<span class="ruby-ivar">@primes</span> = [<span class="ruby-value">2</span>, <span class="ruby-value">3</span>, <span class="ruby-value">5</span>, <span class="ruby-value">7</span>, <span class="ruby-value">11</span>, <span class="ruby-value">13</span>, <span class="ruby-value">17</span>, <span class="ruby-value">19</span>, <span class="ruby-value">23</span>, <span class="ruby-value">29</span>, <span class="ruby-value">31</span>, <span class="ruby-value">37</span>, <span class="ruby-value">41</span>, <span class="ruby-value">43</span>, <span class="ruby-value">47</span>, <span class="ruby-value">53</span>, <span class="ruby-value">59</span>, <span class="ruby-value">61</span>, <span class="ruby-value">67</span>, <span class="ruby-value">71</span>, <span class="ruby-value">73</span>, <span class="ruby-value">79</span>, <span class="ruby-value">83</span>, <span class="ruby-value">89</span>, <span class="ruby-value">97</span>, <span class="ruby-value">101</span>]
<span class="ruby-comment"># @max_checked must be an even number</span>
<span class="ruby-ivar">@max_checked</span> = <span class="ruby-ivar">@primes</span>.<span class="ruby-identifier">last</span> <span class="ruby-operator">+</span> <span class="ruby-value">1</span>
<span class="ruby-keyword">end</span></pre>
</div>
</div>
</div>
</section>
<section id="public-instance-5Buntitled-5D-method-details" class="method-section">
<header>
<h3>Public Instance Methods</h3>
</header>
<div id="method-i-get_nth_prime" class="method-detail ">
<div class="method-heading">
<span class="method-name">get_nth_prime</span><span
class="method-args">(n)</span>
<span class="method-click-advice">click to toggle source</span>
</div>
<div class="method-description">
<div class="method-source-code" id="get_nth_prime-source">
<pre><span class="ruby-comment"># File lib/prime.rb, line 428</span>
<span class="ruby-keyword">def</span> <span class="ruby-identifier ruby-title">get_nth_prime</span>(<span class="ruby-identifier">n</span>)
<span class="ruby-identifier">compute_primes</span> <span class="ruby-keyword">while</span> <span class="ruby-ivar">@primes</span>.<span class="ruby-identifier">size</span> <span class="ruby-operator"><=</span> <span class="ruby-identifier">n</span>
<span class="ruby-ivar">@primes</span>[<span class="ruby-identifier">n</span>]
<span class="ruby-keyword">end</span></pre>
</div>
</div>
</div>
</section>
<section id="private-instance-5Buntitled-5D-method-details" class="method-section">
<header>
<h3>Private Instance Methods</h3>
</header>
<div id="method-i-compute_primes" class="method-detail ">
<div class="method-heading">
<span class="method-name">compute_primes</span><span
class="method-args">()</span>
<span class="method-click-advice">click to toggle source</span>
</div>
<div class="method-description">
<div class="method-source-code" id="compute_primes-source">
<pre><span class="ruby-comment"># File lib/prime.rb, line 434</span>
<span class="ruby-keyword">def</span> <span class="ruby-identifier ruby-title">compute_primes</span>
<span class="ruby-comment"># max_segment_size must be an even number</span>
<span class="ruby-identifier">max_segment_size</span> = <span class="ruby-value">1e6</span>.<span class="ruby-identifier">to_i</span>
<span class="ruby-identifier">max_cached_prime</span> = <span class="ruby-ivar">@primes</span>.<span class="ruby-identifier">last</span>
<span class="ruby-comment"># do not double count primes if #compute_primes is interrupted</span>
<span class="ruby-comment"># by Timeout.timeout</span>
<span class="ruby-ivar">@max_checked</span> = <span class="ruby-identifier">max_cached_prime</span> <span class="ruby-operator">+</span> <span class="ruby-value">1</span> <span class="ruby-keyword">if</span> <span class="ruby-identifier">max_cached_prime</span> <span class="ruby-operator">></span> <span class="ruby-ivar">@max_checked</span>
<span class="ruby-identifier">segment_min</span> = <span class="ruby-ivar">@max_checked</span>
<span class="ruby-identifier">segment_max</span> = [<span class="ruby-identifier">segment_min</span> <span class="ruby-operator">+</span> <span class="ruby-identifier">max_segment_size</span>, <span class="ruby-identifier">max_cached_prime</span> <span class="ruby-operator">*</span> <span class="ruby-value">2</span>].<span class="ruby-identifier">min</span>
<span class="ruby-identifier">root</span> = <span class="ruby-constant">Integer</span>.<span class="ruby-identifier">sqrt</span>(<span class="ruby-identifier">segment_max</span>)
<span class="ruby-identifier">segment</span> = ((<span class="ruby-identifier">segment_min</span> <span class="ruby-operator">+</span> <span class="ruby-value">1</span>) <span class="ruby-operator">..</span> <span class="ruby-identifier">segment_max</span>).<span class="ruby-identifier">step</span>(<span class="ruby-value">2</span>).<span class="ruby-identifier">to_a</span>
(<span class="ruby-value">1</span><span class="ruby-operator">..</span><span class="ruby-constant">Float</span><span class="ruby-operator">::</span><span class="ruby-constant">INFINITY</span>).<span class="ruby-identifier">each</span> <span class="ruby-keyword">do</span> <span class="ruby-operator">|</span><span class="ruby-identifier">sieving</span><span class="ruby-operator">|</span>
<span class="ruby-identifier">prime</span> = <span class="ruby-ivar">@primes</span>[<span class="ruby-identifier">sieving</span>]
<span class="ruby-keyword">break</span> <span class="ruby-keyword">if</span> <span class="ruby-identifier">prime</span> <span class="ruby-operator">></span> <span class="ruby-identifier">root</span>
<span class="ruby-identifier">composite_index</span> = (<span class="ruby-operator">-</span>(<span class="ruby-identifier">segment_min</span> <span class="ruby-operator">+</span> <span class="ruby-value">1</span> <span class="ruby-operator">+</span> <span class="ruby-identifier">prime</span>) <span class="ruby-operator">/</span> <span class="ruby-value">2</span>) <span class="ruby-operator">%</span> <span class="ruby-identifier">prime</span>
<span class="ruby-keyword">while</span> <span class="ruby-identifier">composite_index</span> <span class="ruby-operator"><</span> <span class="ruby-identifier">segment</span>.<span class="ruby-identifier">size</span> <span class="ruby-keyword">do</span>
<span class="ruby-identifier">segment</span>[<span class="ruby-identifier">composite_index</span>] = <span class="ruby-keyword">nil</span>
<span class="ruby-identifier">composite_index</span> <span class="ruby-operator">+=</span> <span class="ruby-identifier">prime</span>
<span class="ruby-keyword">end</span>
<span class="ruby-keyword">end</span>
<span class="ruby-ivar">@primes</span>.<span class="ruby-identifier">concat</span>(<span class="ruby-identifier">segment</span>.<span class="ruby-identifier">compact!</span>)
<span class="ruby-ivar">@max_checked</span> = <span class="ruby-identifier">segment_max</span>
<span class="ruby-keyword">end</span></pre>
</div>
</div>
</div>
</section>
</section>
</main>
<footer id="validator-badges" role="contentinfo">
<p><a href="https://validator.w3.org/check/referer">Validate</a>
<p>Generated by <a href="https://ruby.github.io/rdoc/">RDoc</a> 6.2.1.1.
<p>Based on <a href="http://deveiate.org/projects/Darkfish-RDoc/">Darkfish</a> by <a href="http://deveiate.org">Michael Granger</a>.
</footer>