| <!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="Randomly sample exactly `amount` distinct indices from `0..length`, and return them in random order (fully shuffled)."><meta name="keywords" content="rust, rustlang, rust-lang, sample"><title>sample in rand::seq::index - Rust</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../../normalize.css"><link rel="stylesheet" href="../../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../../ayu.css" disabled><link rel="stylesheet" href="../../../dark.css" disabled><link rel="stylesheet" href="../../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../../storage.js"></script><script defer src="sidebar-items.js"></script><script defer src="../../../main.js"></script><noscript><link rel="stylesheet" href="../../../noscript.css"></noscript><link rel="icon" href="https://www.rust-lang.org/favicon.ico"></head><body class="rustdoc fn"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="mobile-topbar"><button class="sidebar-menu-toggle">☰</button><a class="sidebar-logo" href="../../../rand/index.html"><div class="logo-container"><img src="https://www.rust-lang.org/logos/rust-logo-128x128-blk.png" alt="logo"></div></a><h2></h2></nav><nav class="sidebar"><a class="sidebar-logo" href="../../../rand/index.html"><div class="logo-container"> |
| <img src="https://www.rust-lang.org/logos/rust-logo-128x128-blk.png" alt="logo"></div></a><div class="sidebar-elems"><h2><a href="index.html">In rand::seq::index</a></h2></div></nav><main><div class="width-limiter"><nav class="sub"><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="main-heading"><h1 class="fqn">Function <a href="../../index.html">rand</a>::<wbr><a href="../index.html">seq</a>::<wbr><a href="index.html">index</a>::<wbr><a class="fn" href="#">sample</a><button id="copy-path" onclick="copy_path(this)" title="Copy item path to clipboard"><img src="../../../clipboard.svg" width="19" height="18" alt="Copy item path"></button></h1><span class="out-of-band"><a class="srclink" href="../../../src/rand/seq/index.rs.html#222-259">source</a> · <a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class="inner">−</span>]</a></span></div><div class="item-decl"><pre class="rust fn"><code>pub fn sample<R>(rng: &mut R, length: usize, amount: usize) -> <a class="enum" href="enum.IndexVec.html" title="enum rand::seq::index::IndexVec">IndexVec</a><span class="where fmt-newline">where<br> R: <a class="trait" href="../../trait.Rng.html" title="trait rand::Rng">Rng</a> + ?Sized,</span></code></pre></div><details class="rustdoc-toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Randomly sample exactly <code>amount</code> distinct indices from <code>0..length</code>, and |
| return them in random order (fully shuffled).</p> |
| <p>This method is used internally by the slice sampling methods, but it can |
| sometimes be useful to have the indices themselves so this is provided as |
| an alternative.</p> |
| <p>The implementation used is not specified; we automatically select the |
| fastest available algorithm for the <code>length</code> and <code>amount</code> parameters |
| (based on detailed profiling on an Intel Haswell CPU). Roughly speaking, |
| complexity is <code>O(amount)</code>, except that when <code>amount</code> is small, performance |
| is closer to <code>O(amount^2)</code>, and when <code>length</code> is close to <code>amount</code> then |
| <code>O(length)</code>.</p> |
| <p>Note that performance is significantly better over <code>u32</code> indices than over |
| <code>u64</code> indices. Because of this we hide the underlying type behind an |
| abstraction, <code>IndexVec</code>.</p> |
| <p>If an allocation-free <code>no_std</code> function is required, it is suggested |
| to adapt the internal <code>sample_floyd</code> implementation.</p> |
| <p>Panics if <code>amount > length</code>.</p> |
| </div></details></section></div></main><div id="rustdoc-vars" data-root-path="../../../" data-current-crate="rand" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
