| <!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="A crate with utilities to determine the number of CPUs available on the current system."><meta name="keywords" content="rust, rustlang, rust-lang, num_cpus"><title>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" 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="../crates.js"></script><script defer src="../main.js"></script><noscript><link rel="stylesheet" href="../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../favicon.svg"></head><body class="rustdoc mod crate"><!--[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="../num_cpus/index.html"><div class="logo-container"><img class="rust-logo" src="../rust-logo.svg" alt="logo"></div></a><h2></h2></nav><nav class="sidebar"><a class="sidebar-logo" href="../num_cpus/index.html"><div class="logo-container"><img class="rust-logo" src="../rust-logo.svg" alt="logo"></div></a><h2 class="location"><a href="#">Crate num_cpus</a></h2><div class="sidebar-elems"><ul class="block"><li class="version">Version 1.15.0</li><li><a id="all-types" href="all.html">All Items</a></li></ul><section><ul class="block"><li><a href="#functions">Functions</a></li></ul></section></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">Crate <a class="mod" href="#">num_cpus</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/num_cpus/lib.rs.html#1-459">source</a> · <a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class="inner">−</span>]</a></span></div><details class="rustdoc-toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>A crate with utilities to determine the number of CPUs available on the |
| current system.</p> |
| <p>Sometimes the CPU will exaggerate the number of CPUs it contains, because it can use |
| <a href="https://en.wikipedia.org/wiki/Simultaneous_multithreading">processor tricks</a> to deliver increased performance when there are more threads. This |
| crate provides methods to get both the logical and physical numbers of cores.</p> |
| <p>This information can be used as a guide to how many tasks can be run in parallel. |
| There are many properties of the system architecture that will affect parallelism, |
| for example memory access speeds (for all the caches and RAM) and the physical |
| architecture of the processor, so the number of CPUs should be used as a rough guide |
| only.</p> |
| <h3 id="examples"><a href="#examples">Examples</a></h3> |
| <p>Fetch the number of logical CPUs.</p> |
| |
| <div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">let </span>cpus = num_cpus::get();</code></pre></div> |
| <p>See <a href="https://docs.rs/rayon/1.*/rayon/struct.ThreadPool.html"><code>rayon::Threadpool</code></a> for an example of where the number of CPUs could be |
| used when setting up parallel jobs (Where the threadpool example uses a fixed |
| number 8, it could use the number of CPUs).</p> |
| </div></details><h2 id="functions" class="small-section-header"><a href="#functions">Functions</a></h2><div class="item-table"><div class="item-row"><div class="item-left module-item"><a class="fn" href="fn.get.html" title="num_cpus::get fn">get</a></div><div class="item-right docblock-short">Returns the number of available CPUs of the current system.</div></div><div class="item-row"><div class="item-left module-item"><a class="fn" href="fn.get_physical.html" title="num_cpus::get_physical fn">get_physical</a></div><div class="item-right docblock-short">Returns the number of physical cores of the current system.</div></div></div></section></div></main><div id="rustdoc-vars" data-root-path="../" data-current-crate="num_cpus" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
