| <!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="Source of the Rust file `/root/.cargo/git/checkouts/rayon-3b3b152053499ede/a07ce2e/src/iter/find_first_last/mod.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>mod.rs - source</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="../../../../source-script.js"></script><script defer src="../../../../source-files.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 source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><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></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../../../rayon/index.html"><img class="rust-logo" src="../../../../rust-logo.svg" alt="logo"></a><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="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| </pre><pre class="rust"><code><span class="kw">use </span><span class="kw">super</span>::plumbing::<span class="kw-2">*</span>; |
| <span class="kw">use super</span>::<span class="kw-2">*</span>; |
| <span class="kw">use </span>std::cell::Cell; |
| <span class="kw">use </span>std::sync::atomic::{AtomicUsize, Ordering}; |
| |
| <span class="attribute">#[cfg(test)] |
| </span><span class="kw">mod </span>test; |
| |
| <span class="comment">// The key optimization for find_first is that a consumer can stop its search if |
| // some consumer to its left already found a match (and similarly for consumers |
| // to the right for find_last). To make this work, all consumers need some |
| // notion of their position in the data relative to other consumers, including |
| // unindexed consumers that have no built-in notion of position. |
| // |
| // To solve this, we assign each consumer a lower and upper bound for an |
| // imaginary "range" of data that it consumes. The initial consumer starts with |
| // the range 0..usize::max_value(). The split divides this range in half so that |
| // one resulting consumer has the range 0..(usize::max_value() / 2), and the |
| // other has (usize::max_value() / 2)..usize::max_value(). Every subsequent |
| // split divides the range in half again until it cannot be split anymore |
| // (i.e. its length is 1), in which case the split returns two consumers with |
| // the same range. In that case both consumers will continue to consume all |
| // their data regardless of whether a better match is found, but the reducer |
| // will still return the correct answer. |
| |
| </span><span class="attribute">#[derive(Copy, Clone)] |
| </span><span class="kw">enum </span>MatchPosition { |
| Leftmost, |
| Rightmost, |
| } |
| |
| <span class="doccomment">/// Returns true if pos1 is a better match than pos2 according to MatchPosition |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">fn </span>better_position(pos1: usize, pos2: usize, mp: MatchPosition) -> bool { |
| <span class="kw">match </span>mp { |
| MatchPosition::Leftmost => pos1 < pos2, |
| MatchPosition::Rightmost => pos1 > pos2, |
| } |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>find_first<I, P>(pi: I, find_op: P) -> <span class="prelude-ty">Option</span><I::Item> |
| <span class="kw">where |
| </span>I: ParallelIterator, |
| P: Fn(<span class="kw-2">&</span>I::Item) -> bool + Sync, |
| { |
| <span class="kw">let </span>best_found = AtomicUsize::new(usize::max_value()); |
| <span class="kw">let </span>consumer = FindConsumer::new(<span class="kw-2">&</span>find_op, MatchPosition::Leftmost, <span class="kw-2">&</span>best_found); |
| pi.drive_unindexed(consumer) |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>find_last<I, P>(pi: I, find_op: P) -> <span class="prelude-ty">Option</span><I::Item> |
| <span class="kw">where |
| </span>I: ParallelIterator, |
| P: Fn(<span class="kw-2">&</span>I::Item) -> bool + Sync, |
| { |
| <span class="kw">let </span>best_found = AtomicUsize::new(<span class="number">0</span>); |
| <span class="kw">let </span>consumer = FindConsumer::new(<span class="kw-2">&</span>find_op, MatchPosition::Rightmost, <span class="kw-2">&</span>best_found); |
| pi.drive_unindexed(consumer) |
| } |
| |
| <span class="kw">struct </span>FindConsumer<<span class="lifetime">'p</span>, P> { |
| find_op: <span class="kw-2">&</span><span class="lifetime">'p </span>P, |
| lower_bound: Cell<usize>, |
| upper_bound: usize, |
| match_position: MatchPosition, |
| best_found: <span class="kw-2">&</span><span class="lifetime">'p </span>AtomicUsize, |
| } |
| |
| <span class="kw">impl</span><<span class="lifetime">'p</span>, P> FindConsumer<<span class="lifetime">'p</span>, P> { |
| <span class="kw">fn </span>new(find_op: <span class="kw-2">&</span><span class="lifetime">'p </span>P, match_position: MatchPosition, best_found: <span class="kw-2">&</span><span class="lifetime">'p </span>AtomicUsize) -> <span class="self">Self </span>{ |
| FindConsumer { |
| find_op, |
| lower_bound: Cell::new(<span class="number">0</span>), |
| upper_bound: usize::max_value(), |
| match_position, |
| best_found, |
| } |
| } |
| |
| <span class="kw">fn </span>current_index(<span class="kw-2">&</span><span class="self">self</span>) -> usize { |
| <span class="kw">match </span><span class="self">self</span>.match_position { |
| MatchPosition::Leftmost => <span class="self">self</span>.lower_bound.get(), |
| MatchPosition::Rightmost => <span class="self">self</span>.upper_bound, |
| } |
| } |
| } |
| |
| <span class="kw">impl</span><<span class="lifetime">'p</span>, T, P> Consumer<T> <span class="kw">for </span>FindConsumer<<span class="lifetime">'p</span>, P> |
| <span class="kw">where |
| </span>T: Send, |
| P: Fn(<span class="kw-2">&</span>T) -> bool + Sync, |
| { |
| <span class="kw">type </span>Folder = FindFolder<<span class="lifetime">'p</span>, T, P>; |
| <span class="kw">type </span>Reducer = FindReducer; |
| <span class="kw">type </span><span class="prelude-ty">Result </span>= <span class="prelude-ty">Option</span><T>; |
| |
| <span class="kw">fn </span>split_at(<span class="self">self</span>, _index: usize) -> (<span class="self">Self</span>, <span class="self">Self</span>, <span class="self">Self</span>::Reducer) { |
| <span class="kw">let </span>dir = <span class="self">self</span>.match_position; |
| ( |
| <span class="self">self</span>.split_off_left(), |
| <span class="self">self</span>, |
| FindReducer { |
| match_position: dir, |
| }, |
| ) |
| } |
| |
| <span class="kw">fn </span>into_folder(<span class="self">self</span>) -> <span class="self">Self</span>::Folder { |
| FindFolder { |
| find_op: <span class="self">self</span>.find_op, |
| boundary: <span class="self">self</span>.current_index(), |
| match_position: <span class="self">self</span>.match_position, |
| best_found: <span class="self">self</span>.best_found, |
| item: <span class="prelude-val">None</span>, |
| } |
| } |
| |
| <span class="kw">fn </span>full(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="comment">// can stop consuming if the best found index so far is *strictly* |
| // better than anything this consumer will find |
| </span>better_position( |
| <span class="self">self</span>.best_found.load(Ordering::Relaxed), |
| <span class="self">self</span>.current_index(), |
| <span class="self">self</span>.match_position, |
| ) |
| } |
| } |
| |
| <span class="kw">impl</span><<span class="lifetime">'p</span>, T, P> UnindexedConsumer<T> <span class="kw">for </span>FindConsumer<<span class="lifetime">'p</span>, P> |
| <span class="kw">where |
| </span>T: Send, |
| P: Fn(<span class="kw-2">&</span>T) -> bool + Sync, |
| { |
| <span class="kw">fn </span>split_off_left(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="self">Self </span>{ |
| <span class="comment">// Upper bound for one consumer will be lower bound for the other. This |
| // overlap is okay, because only one of the bounds will be used for |
| // comparing against best_found; the other is kept only to be able to |
| // divide the range in half. |
| // |
| // When the resolution of usize has been exhausted (i.e. when |
| // upper_bound = lower_bound), both results of this split will have the |
| // same range. When that happens, we lose the ability to tell one |
| // consumer to stop working when the other finds a better match, but the |
| // reducer ensures that the best answer is still returned (see the test |
| // above). |
| </span><span class="kw">let </span>old_lower_bound = <span class="self">self</span>.lower_bound.get(); |
| <span class="kw">let </span>median = old_lower_bound + ((<span class="self">self</span>.upper_bound - old_lower_bound) / <span class="number">2</span>); |
| <span class="self">self</span>.lower_bound.set(median); |
| |
| FindConsumer { |
| find_op: <span class="self">self</span>.find_op, |
| lower_bound: Cell::new(old_lower_bound), |
| upper_bound: median, |
| match_position: <span class="self">self</span>.match_position, |
| best_found: <span class="self">self</span>.best_found, |
| } |
| } |
| |
| <span class="kw">fn </span>to_reducer(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="self">Self</span>::Reducer { |
| FindReducer { |
| match_position: <span class="self">self</span>.match_position, |
| } |
| } |
| } |
| |
| <span class="kw">struct </span>FindFolder<<span class="lifetime">'p</span>, T, P> { |
| find_op: <span class="kw-2">&</span><span class="lifetime">'p </span>P, |
| boundary: usize, |
| match_position: MatchPosition, |
| best_found: <span class="kw-2">&</span><span class="lifetime">'p </span>AtomicUsize, |
| item: <span class="prelude-ty">Option</span><T>, |
| } |
| |
| <span class="kw">impl</span><<span class="lifetime">'p</span>, P: <span class="lifetime">'p </span>+ Fn(<span class="kw-2">&</span>T) -> bool, T> Folder<T> <span class="kw">for </span>FindFolder<<span class="lifetime">'p</span>, T, P> { |
| <span class="kw">type </span><span class="prelude-ty">Result </span>= <span class="prelude-ty">Option</span><T>; |
| |
| <span class="kw">fn </span>consume(<span class="kw-2">mut </span><span class="self">self</span>, item: T) -> <span class="self">Self </span>{ |
| <span class="kw">let </span>found_best_in_range = <span class="kw">match </span><span class="self">self</span>.match_position { |
| MatchPosition::Leftmost => <span class="self">self</span>.item.is_some(), |
| MatchPosition::Rightmost => <span class="bool-val">false</span>, |
| }; |
| |
| <span class="kw">if </span>!found_best_in_range && (<span class="self">self</span>.find_op)(<span class="kw-2">&</span>item) { |
| <span class="comment">// Continuously try to set best_found until we succeed or we |
| // discover a better match was already found. |
| </span><span class="kw">let </span><span class="kw-2">mut </span>current = <span class="self">self</span>.best_found.load(Ordering::Relaxed); |
| <span class="kw">loop </span>{ |
| <span class="kw">if </span>better_position(current, <span class="self">self</span>.boundary, <span class="self">self</span>.match_position) { |
| <span class="kw">break</span>; |
| } |
| <span class="kw">match </span><span class="self">self</span>.best_found.compare_exchange_weak( |
| current, |
| <span class="self">self</span>.boundary, |
| Ordering::Relaxed, |
| Ordering::Relaxed, |
| ) { |
| <span class="prelude-val">Ok</span>(<span class="kw">_</span>) => { |
| <span class="self">self</span>.item = <span class="prelude-val">Some</span>(item); |
| <span class="kw">break</span>; |
| } |
| <span class="prelude-val">Err</span>(v) => current = v, |
| } |
| } |
| } |
| <span class="self">self |
| </span>} |
| |
| <span class="kw">fn </span>complete(<span class="self">self</span>) -> <span class="self">Self</span>::Result { |
| <span class="self">self</span>.item |
| } |
| |
| <span class="kw">fn </span>full(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="kw">let </span>found_best_in_range = <span class="kw">match </span><span class="self">self</span>.match_position { |
| MatchPosition::Leftmost => <span class="self">self</span>.item.is_some(), |
| MatchPosition::Rightmost => <span class="bool-val">false</span>, |
| }; |
| |
| found_best_in_range |
| || better_position( |
| <span class="self">self</span>.best_found.load(Ordering::Relaxed), |
| <span class="self">self</span>.boundary, |
| <span class="self">self</span>.match_position, |
| ) |
| } |
| } |
| |
| <span class="kw">struct </span>FindReducer { |
| match_position: MatchPosition, |
| } |
| |
| <span class="kw">impl</span><T> Reducer<<span class="prelude-ty">Option</span><T>> <span class="kw">for </span>FindReducer { |
| <span class="kw">fn </span>reduce(<span class="self">self</span>, left: <span class="prelude-ty">Option</span><T>, right: <span class="prelude-ty">Option</span><T>) -> <span class="prelude-ty">Option</span><T> { |
| <span class="kw">match </span><span class="self">self</span>.match_position { |
| MatchPosition::Leftmost => left.or(right), |
| MatchPosition::Rightmost => right.or(left), |
| } |
| } |
| } |
| </code></pre></div> |
| </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> |
