19 lines
4.9 KiB
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19 lines
4.9 KiB
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<!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)."><title>sample in rand::seq::index - Rust</title><script>if(window.location.protocol!=="file:")document.head.insertAdjacentHTML("beforeend","SourceSerif4-Regular-6b053e98.ttf.woff2,FiraSans-Italic-81dc35de.woff2,FiraSans-Regular-0fe48ade.woff2,FiraSans-MediumItalic-ccf7e434.woff2,FiraSans-Medium-e1aa3f0a.woff2,SourceCodePro-Regular-8badfe75.ttf.woff2,SourceCodePro-Semibold-aa29a496.ttf.woff2".split(",").map(f=>`<link rel="preload" as="font" type="font/woff2"href="../../../static.files/${f}">`).join(""))</script><link rel="stylesheet" href="../../../static.files/normalize-9960930a.css"><link rel="stylesheet" href="../../../static.files/rustdoc-ca0dd0c4.css"><meta name="rustdoc-vars" data-root-path="../../../" data-static-root-path="../../../static.files/" data-current-crate="rand" data-themes="" data-resource-suffix="" data-rustdoc-version="1.93.1 (01f6ddf75 2026-02-11) (Arch Linux rust 1:1.93.1-1)" data-channel="1.93.1" data-search-js="search-9e2438ea.js" data-stringdex-js="stringdex-a3946164.js" data-settings-js="settings-c38705f0.js" ><script src="../../../static.files/storage-e2aeef58.js"></script><script defer src="sidebar-items.js"></script><script defer src="../../../static.files/main-a410ff4d.js"></script><noscript><link rel="stylesheet" href="../../../static.files/noscript-263c88ec.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]--><rustdoc-topbar><h2><a href="#">sample</a></h2></rustdoc-topbar><nav class="sidebar"><div class="sidebar-crate"><a class="logo-container" href="../../../rand/index.html"><img src="https://www.rust-lang.org/logos/rust-logo-128x128-blk.png" alt="logo"></a><h2><a href="../../../rand/index.html">rand</a><span class="version">0.9.2</span></h2></div><div class="sidebar-elems"><div id="rustdoc-modnav"><h2><a href="index.html">In rand::<wbr>seq::<wbr>index</a></h2></div></div></nav><div class="sidebar-resizer" title="Drag to resize sidebar"></div><main><div class="width-limiter"><section id="main-content" class="content"><div class="main-heading"><div class="rustdoc-breadcrumbs"><a href="../../index.html">rand</a>::<wbr><a href="../index.html">seq</a>::<wbr><a href="index.html">index</a></div><h1>Function <span class="fn">sample</span> <button id="copy-path" title="Copy item path to clipboard">Copy item path</button></h1><rustdoc-toolbar></rustdoc-toolbar><span class="sub-heading"><a class="src" href="../../../src/rand/seq/index.rs.html#240-283">Source</a> </span></div><pre class="rust item-decl"><code>pub fn sample<R>(rng: <a class="primitive" href="https://doc.rust-lang.org/1.93.1/std/primitive.reference.html">&mut R</a>, length: <a class="primitive" href="https://doc.rust-lang.org/1.93.1/std/primitive.usize.html">usize</a>, amount: <a class="primitive" href="https://doc.rust-lang.org/1.93.1/std/primitive.usize.html">usize</a>) -> <a class="enum" href="enum.IndexVec.html" title="enum rand::seq::index::IndexVec">IndexVec</a><div class="where">where
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R: <a class="trait" href="../../trait.Rng.html" title="trait rand::Rng">Rng</a> + ?<a class="trait" href="https://doc.rust-lang.org/1.93.1/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,</div></code></pre><details class="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
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return them in random order (fully shuffled).</p>
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<p>This method is used internally by the slice sampling methods, but it can
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sometimes be useful to have the indices themselves so this is provided as
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an alternative.</p>
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<p>The implementation used is not specified; we automatically select the
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fastest available algorithm for the <code>length</code> and <code>amount</code> parameters
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(based on detailed profiling on an Intel Haswell CPU). Roughly speaking,
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complexity is <code>O(amount)</code>, except that when <code>amount</code> is small, performance
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is closer to <code>O(amount^2)</code>, and when <code>length</code> is close to <code>amount</code> then
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<code>O(length)</code>.</p>
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<p>Note that performance is significantly better over <code>u32</code> indices than over
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<code>u64</code> indices. Because of this we hide the underlying type behind an
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abstraction, <code>IndexVec</code>.</p>
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<p>If an allocation-free <code>no_std</code> function is required, it is suggested
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to adapt the internal <code>sample_floyd</code> implementation.</p>
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<p>Panics if <code>amount > length</code>.</p>
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</div></details></section></div></main></body></html> |