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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="Returns the number of available CPUs of the current system."><meta name="keywords" content="rust, rustlang, rust-lang, get"><title>get in num_cpus - 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" type="text/css" href="../normalize.css"><link rel="stylesheet" type="text/css" href="../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../ayu.css" disabled><link rel="stylesheet" type="text/css" href="../dark.css" disabled><link rel="stylesheet" type="text/css" href="../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../storage.js"></script><script src="../crates.js"></script><script defer src="../main.js"></script>
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</a><div class="sidebar-elems"><h2 class="location">Other items in<br><a href="index.html">num_cpus</a></h2><div id="sidebar-vars" data-name="get" data-ty="fn" data-relpath=""></div><script defer src="sidebar-items.js"></script></div></nav><main><div class="width-limiter"><div class="sub-container"><a class="sub-logo-container" href="../num_cpus/index.html"><img class="rust-logo" src="../rust-logo.png" alt="logo"></a><nav class="sub"><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!" aria-haspopup="menu" title="themes"><img width="18" height="18" alt="Pick another theme!" src="../brush.svg"></button><div id="theme-choices" role="menu"></div></div><form class="search-form"><div class="search-container"><div><select id="crate-search"><option value="All crates">All crates</option></select><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"></div><button type="button" id="help-button" title="help">?</button><a id="settings-menu" href="../settings.html" title="settings"><img width="18" height="18" alt="Change settings" src="../wheel.svg"></a></div></form></nav></div><section id="main-content" class="content"><h1 class="fqn"><span class="in-band">Function <a href="index.html">num_cpus</a>::<wbr><a class="fn" href="#">get</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></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></span><a class="srclink" href="../src/num_cpus/lib.rs.html#73-75" title="goto source code">[src]</a></span></h1><div class="docblock item-decl"><pre class="rust fn"><code>pub fn get() -> <a class="primitive" href="https://doc.rust-lang.org/1.59.0/std/primitive.usize.html">usize</a></code></pre></div><details class="rustdoc-toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Returns the number of available CPUs of the current system.</p>
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<p>This function will get the number of logical cores. Sometimes this is different from the number
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of physical cores (See <a href="https://en.wikipedia.org/wiki/Simultaneous_multithreading">Simultaneous multithreading on Wikipedia</a>).</p>
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<p>This will always return at least <code>1</code>.</p>
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<h2 id="examples" class="section-header"><a href="#examples">Examples</a></h2>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">let</span> <span class="ident">cpus</span> <span class="op">=</span> <span class="ident">num_cpus::get</span>();
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<span class="kw">if</span> <span class="ident">cpus</span> <span class="op">></span> <span class="number">1</span> {
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<span class="macro">println!</span>(<span class="string">"We are on a multicore system with {} CPUs"</span>, <span class="ident">cpus</span>);
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} <span class="kw">else</span> {
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<span class="macro">println!</span>(<span class="string">"We are on a single core system"</span>);
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}</code></pre></div>
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<h2 id="note" class="section-header"><a href="#note">Note</a></h2>
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<p>This will check <a href="http://www.gnu.org/software/libc/manual/html_node/CPU-Affinity.html">sched affinity</a> on Linux, showing a lower number of CPUs if the current
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thread does not have access to all the computer’s CPUs.</p>
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<p>This will also check <a href="https://www.kernel.org/doc/Documentation/cgroup-v1/cgroups.txt">cgroups</a>, frequently used in containers to constrain CPU usage.</p>
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