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65 lines
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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="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."><title>scope_fifo in rayon - 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="rayon" 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="alternate icon" type="image/png" href="../static.files/favicon-32x32-eab170b8.png"><link rel="icon" type="image/svg+xml" href="../static.files/favicon-044be391.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]--><rustdoc-topbar><h2><a href="#">scope_fifo</a></h2></rustdoc-topbar><nav class="sidebar"><div class="sidebar-crate"><h2><a href="../rayon/index.html">rayon</a><span class="version">1.11.0</span></h2></div><div class="sidebar-elems"><section id="rustdoc-toc"><h2 class="location"><a href="#">scope_<wbr>fifo</a></h2><h3><a href="#">Sections</a></h3><ul class="block top-toc"><li><a href="#task-execution" title="Task execution">Task execution</a></li><li><a href="#panics" title="Panics">Panics</a></li></ul></section><div id="rustdoc-modnav"><h2 class="in-crate"><a href="index.html">In crate rayon</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">rayon</a></div><h1>Function <span class="fn">scope_<wbr>fifo</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/rayon_core/scope/mod.rs.html#366-369">Source</a> </span></div><pre class="rust item-decl"><code>pub fn scope_fifo<'scope, OP, R>(op: OP) -> R<div class="where">where
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OP: <a class="trait" href="https://doc.rust-lang.org/1.93.1/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>(&<a class="struct" href="struct.ScopeFifo.html" title="struct rayon::ScopeFifo">ScopeFifo</a><'scope>) -> R + <a class="trait" href="https://doc.rust-lang.org/1.93.1/core/marker/trait.Send.html" title="trait core::marker::Send">Send</a>,
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R: <a class="trait" href="https://doc.rust-lang.org/1.93.1/core/marker/trait.Send.html" title="trait core::marker::Send">Send</a>,</div></code></pre><details class="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
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closure with a reference to <code>s</code>. This closure can then spawn
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asynchronous tasks into <code>s</code>. Those tasks may run asynchronously with
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respect to the closure; they may themselves spawn additional tasks
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into <code>s</code>. When the closure returns, it will block until all tasks
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that have been spawned into <code>s</code> complete.</p>
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<h2 id="task-execution"><a class="doc-anchor" href="#task-execution">§</a>Task execution</h2>
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<p>Tasks in a <code>scope_fifo()</code> run similarly to <a href="fn.scope.html" title="fn rayon::scope"><code>scope()</code></a>, but there’s a
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difference in the order of execution. Consider a similar example:</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="comment">// point start
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</span>rayon::scope_fifo(|s| {
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s.spawn_fifo(|s| { <span class="comment">// task s.1
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</span>s.spawn_fifo(|s| { <span class="comment">// task s.1.1
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</span>rayon::scope_fifo(|t| {
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t.spawn_fifo(|<span class="kw">_</span>| ()); <span class="comment">// task t.1
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</span>t.spawn_fifo(|<span class="kw">_</span>| ()); <span class="comment">// task t.2
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</span>});
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});
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});
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s.spawn_fifo(|s| { <span class="comment">// task s.2
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</span>});
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<span class="comment">// point mid
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</span>});
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<span class="comment">// point end</span></code></pre></div>
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<p>The various tasks that are run will execute roughly like so:</p>
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<div class="example-wrap"><pre class="language-notrust"><code>| (start)
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|
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| (FIFO scope `s` created)
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+--------------------+ (task s.1)
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+-------+ (task s.2) |
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| | +---+ (task s.1.1)
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| | | |
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| | | | (FIFO scope `t` created)
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| | | +----------------+ (task t.1)
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| | | +---+ (task t.2) |
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| (mid) | | | | |
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: | | + <-+------------+ (scope `t` ends)
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: | | |
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|<------+------------+---+ (scope `s` ends)
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|
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| (end)</code></pre></div>
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<p>Under <code>scope_fifo()</code>, the spawns are prioritized in a FIFO order on
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the thread from which they were spawned, as opposed to <code>scope()</code>’s
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LIFO. So in this example, we can expect <code>s.1</code> to execute before
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<code>s.2</code>, and <code>t.1</code> before <code>t.2</code>. Other threads also steal tasks in
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FIFO order, as usual. Overall, this has roughly the same order as
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the now-deprecated <a href="struct.ThreadPoolBuilder.html#method.breadth_first" title="method rayon::ThreadPoolBuilder::breadth_first"><code>breadth_first</code></a> option, except the effect is
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isolated to a particular scope. If spawns are intermingled from any
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combination of <code>scope()</code> and <code>scope_fifo()</code>, or from different
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threads, their order is only specified with respect to spawns in the
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same scope and thread.</p>
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<p>For more details on this design, see Rayon <a href="https://github.com/rayon-rs/rfcs/blob/main/accepted/rfc0001-scope-scheduling.md">RFC #1</a>.</p>
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<h2 id="panics"><a class="doc-anchor" href="#panics">§</a>Panics</h2>
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<p>If a panic occurs, either in the closure given to <code>scope_fifo()</code> or
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in any of the spawned jobs, that panic will be propagated and the
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call to <code>scope_fifo()</code> will panic. If multiple panics occurs, it is
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non-deterministic which of their panic values will propagate.
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Regardless, once a task is spawned using <code>scope.spawn_fifo()</code>, it
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will execute, even if the spawning task should later panic.
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<code>scope_fifo()</code> returns once all spawned jobs have completed, and any
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panics are propagated at that point.</p>
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</div></details></section></div></main></body></html> |