| <!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="Creates a “fork-join” scope `s` with FIFO order, and invokes the closure with a reference to `s`. This closure can then spawn asynchronous tasks into `s`. Those tasks may run asynchronously with respect to the closure; they may themselves spawn additional tasks into `s`. When the closure returns, it will block until all tasks that have been spawned into `s` complete."><meta name="keywords" content="rust, rustlang, rust-lang, scope_fifo"><title>scope_fifo in rayon - 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="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 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="../rayon/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="../rayon/index.html"><div class="logo-container"><img class="rust-logo" src="../rust-logo.svg" alt="logo"></div></a><div class="sidebar-elems"><h2><a href="index.html">In rayon</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">rayon</a>::<wbr><a class="fn" href="#">scope_fifo</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/rayon_core/scope/mod.rs.html#395-398">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 scope_fifo<'scope, OP, R>(op: OP) -> R<span class="where fmt-newline">where<br> OP: FnOnce(&<a class="struct" href="struct.ScopeFifo.html" title="struct rayon::ScopeFifo">ScopeFifo</a><'scope>) -> R + Send,<br> R: Send,</span></code></pre></div><details class="rustdoc-toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Creates a “fork-join” scope <code>s</code> with FIFO order, and invokes the |
| closure with a reference to <code>s</code>. This closure can then spawn |
| asynchronous tasks into <code>s</code>. Those tasks may run asynchronously with |
| respect to the closure; they may themselves spawn additional tasks |
| into <code>s</code>. When the closure returns, it will block until all tasks |
| that have been spawned into <code>s</code> complete.</p> |
| <h2 id="task-execution"><a href="#task-execution">Task execution</a></h2> |
| <p>Tasks in a <code>scope_fifo()</code> run similarly to <a href="fn.scope.html"><code>scope()</code></a>, but there’s a |
| difference in the order of execution. Consider a similar example:</p> |
| |
| <div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="comment">// point start |
| </span>rayon::scope_fifo(|s| { |
| s.spawn_fifo(|s| { <span class="comment">// task s.1 |
| </span>s.spawn_fifo(|s| { <span class="comment">// task s.1.1 |
| </span>rayon::scope_fifo(|t| { |
| t.spawn_fifo(|<span class="kw">_</span>| ()); <span class="comment">// task t.1 |
| </span>t.spawn_fifo(|<span class="kw">_</span>| ()); <span class="comment">// task t.2 |
| </span>}); |
| }); |
| }); |
| s.spawn_fifo(|s| { <span class="comment">// task s.2 |
| </span>}); |
| <span class="comment">// point mid |
| </span>}); |
| <span class="comment">// point end</span></code></pre></div> |
| <p>The various tasks that are run will execute roughly like so:</p> |
| <div class="example-wrap"><pre class="language-notrust"><code>| (start) |
| | |
| | (FIFO scope `s` created) |
| +--------------------+ (task s.1) |
| +-------+ (task s.2) | |
| | | +---+ (task s.1.1) |
| | | | | |
| | | | | (FIFO scope `t` created) |
| | | | +----------------+ (task t.1) |
| | | | +---+ (task t.2) | |
| | (mid) | | | | | |
| : | | + <-+------------+ (scope `t` ends) |
| : | | | |
| |<------+------------+---+ (scope `s` ends) |
| | |
| | (end)</code></pre></div> |
| <p>Under <code>scope_fifo()</code>, the spawns are prioritized in a FIFO order on |
| the thread from which they were spawned, as opposed to <code>scope()</code>’s |
| LIFO. So in this example, we can expect <code>s.1</code> to execute before |
| <code>s.2</code>, and <code>t.1</code> before <code>t.2</code>. Other threads also steal tasks in |
| FIFO order, as usual. Overall, this has roughly the same order as |
| the now-deprecated <a href="struct.ThreadPoolBuilder.html#method.breadth_first"><code>breadth_first</code></a> option, except the effect is |
| isolated to a particular scope. If spawns are intermingled from any |
| combination of <code>scope()</code> and <code>scope_fifo()</code>, or from different |
| threads, their order is only specified with respect to spawns in the |
| same scope and thread.</p> |
| <p>For more details on this design, see Rayon <a href="https://github.com/rayon-rs/rfcs/blob/master/accepted/rfc0001-scope-scheduling.md">RFC #1</a>.</p> |
| <h2 id="panics"><a href="#panics">Panics</a></h2> |
| <p>If a panic occurs, either in the closure given to <code>scope_fifo()</code> or |
| in any of the spawned jobs, that panic will be propagated and the |
| call to <code>scope_fifo()</code> will panic. If multiple panics occurs, it is |
| non-deterministic which of their panic values will propagate. |
| Regardless, once a task is spawned using <code>scope.spawn_fifo()</code>, it |
| will execute, even if the spawning task should later panic. |
| <code>scope_fifo()</code> returns once all spawned jobs have completed, and any |
| panics are propagated at that point.</p> |
| </div></details></section></div></main><div id="rustdoc-vars" data-root-path="../" data-current-crate="rayon" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
