crossbeam-deque-0.8.5/.cargo_vcs_info.json0000644000000001550000000000100141260ustar { "git": { "sha1": "9c3182abebb36bdc9446d75d4644190fef70fa01" }, "path_in_vcs": "crossbeam-deque" }crossbeam-deque-0.8.5/CHANGELOG.md000064400000000000000000000071171046102023000145340ustar 00000000000000# Version 0.8.5 - Remove dependency on `cfg-if`. (#1072) # Version 0.8.4 - Bump the minimum supported Rust version to 1.61. (#1037) # Version 0.8.3 - Add `Stealer::{steal_batch_with_limit, steal_batch_with_limit_and_pop}` methods. (#903) - Add `Injector::{steal_batch_with_limit, steal_batch_with_limit_and_pop}` methods. (#903) # Version 0.8.2 - Bump the minimum supported Rust version to 1.38. (#877) # Version 0.8.1 - Fix deque steal race condition. (#726) - Add `Stealer::len` method. (#708) # Version 0.8.0 **Note:** This release has been yanked. See [GHSA-pqqp-xmhj-wgcw](https://github.com/crossbeam-rs/crossbeam/security/advisories/GHSA-pqqp-xmhj-wgcw) for details. - Bump the minimum supported Rust version to 1.36. - Add `Worker::len()` and `Injector::len()` methods. - Add `std` (enabled by default) feature for forward compatibility. # Version 0.7.4 - Fix deque steal race condition. # Version 0.7.3 **Note:** This release has been yanked. See [GHSA-pqqp-xmhj-wgcw](https://github.com/crossbeam-rs/crossbeam/security/advisories/GHSA-pqqp-xmhj-wgcw) for details. - Stop stealing from the same deque. (#448) - Fix unsoundness issues by adopting `MaybeUninit`. (#458) # Version 0.7.2 **Note:** This release has been yanked. See [GHSA-pqqp-xmhj-wgcw](https://github.com/crossbeam-rs/crossbeam/security/advisories/GHSA-pqqp-xmhj-wgcw) for details. - Bump `crossbeam-epoch` to `0.8`. - Bump `crossbeam-utils` to `0.7`. # Version 0.7.1 **Note:** This release has been yanked. See [GHSA-pqqp-xmhj-wgcw](https://github.com/crossbeam-rs/crossbeam/security/advisories/GHSA-pqqp-xmhj-wgcw) for details. - Bump the minimum required version of `crossbeam-utils`. # Version 0.7.0 **Note:** This release has been yanked. See [GHSA-pqqp-xmhj-wgcw](https://github.com/crossbeam-rs/crossbeam/security/advisories/GHSA-pqqp-xmhj-wgcw) for details. - Make `Worker::pop()` faster in the FIFO case. - Replace `fifo()` nad `lifo()` with `Worker::new_fifo()` and `Worker::new_lifo()`. - Add more batched steal methods. - Introduce `Injector`, a MPMC queue. - Rename `Steal::Data` to `Steal::Success`. - Add `Steal::or_else()` and implement `FromIterator` for `Steal`. - Add `#[must_use]` to `Steal`. # Version 0.6.3 - Bump `crossbeam-epoch` to `0.7`. # Version 0.6.2 - Update `crosbeam-utils` to `0.6`. # Version 0.6.1 - Change a few `Relaxed` orderings to `Release` in order to fix false positives by tsan. # Version 0.6.0 - Add `Stealer::steal_many` for batched stealing. - Change the return type of `pop` to `Pop` so that spinning can be handled manually. # Version 0.5.2 - Update `crossbeam-utils` to `0.5.0`. # Version 0.5.1 - Minor optimizations. # Version 0.5.0 - Add two deque constructors : `fifo()` and `lifo()`. - Update `rand` to `0.5.3`. - Rename `Deque` to `Worker`. - Return `Option` from `Stealer::steal`. - Remove methods `Deque::len` and `Stealer::len`. - Remove method `Deque::stealer`. - Remove method `Deque::steal`. # Version 0.4.1 - Update `crossbeam-epoch` to `0.5.0`. # Version 0.4.0 - Update `crossbeam-epoch` to `0.4.2`. - Update `crossbeam-utils` to `0.4.0`. - Require minimum Rust version 1.25. # Version 0.3.1 - Add `Deque::capacity`. - Add `Deque::min_capacity`. - Add `Deque::shrink_to_fit`. - Update `crossbeam-epoch` to `0.3.0`. - Support Rust 1.20. - Shrink the buffer in `Deque::push` if necessary. # Version 0.3.0 - Update `crossbeam-epoch` to `0.4.0`. - Drop support for Rust 1.13. # Version 0.2.0 - Update `crossbeam-epoch` to `0.3.0`. - Support Rust 1.13. # Version 0.1.1 - Update `crossbeam-epoch` to `0.2.0`. # Version 0.1.0 - First implementation of the Chase-Lev deque. crossbeam-deque-0.8.5/Cargo.toml0000644000000023350000000000100121260ustar # THIS FILE IS AUTOMATICALLY GENERATED BY CARGO # # When uploading crates to the registry Cargo will automatically # "normalize" Cargo.toml files for maximal compatibility # with all versions of Cargo and also rewrite `path` dependencies # to registry (e.g., crates.io) dependencies. # # If you are reading this file be aware that the original Cargo.toml # will likely look very different (and much more reasonable). # See Cargo.toml.orig for the original contents. [package] edition = "2021" rust-version = "1.61" name = "crossbeam-deque" version = "0.8.5" description = "Concurrent work-stealing deque" homepage = "https://github.com/crossbeam-rs/crossbeam/tree/master/crossbeam-deque" readme = "README.md" keywords = [ "chase-lev", "lock-free", "scheduler", "scheduling", ] categories = [ "algorithms", "concurrency", "data-structures", ] license = "MIT OR Apache-2.0" repository = "https://github.com/crossbeam-rs/crossbeam" [dependencies.crossbeam-epoch] version = "0.9.17" default-features = false [dependencies.crossbeam-utils] version = "0.8.18" default-features = false [dev-dependencies.rand] version = "0.8" [features] default = ["std"] std = [ "crossbeam-epoch/std", "crossbeam-utils/std", ] crossbeam-deque-0.8.5/Cargo.toml.orig000064400000000000000000000017611046102023000156110ustar 00000000000000[package] name = "crossbeam-deque" # When publishing a new version: # - Update CHANGELOG.md # - Update README.md # - Create "crossbeam-deque-X.Y.Z" git tag version = "0.8.5" edition = "2021" rust-version = "1.61" license = "MIT OR Apache-2.0" repository = "https://github.com/crossbeam-rs/crossbeam" homepage = "https://github.com/crossbeam-rs/crossbeam/tree/master/crossbeam-deque" description = "Concurrent work-stealing deque" keywords = ["chase-lev", "lock-free", "scheduler", "scheduling"] categories = ["algorithms", "concurrency", "data-structures"] [features] default = ["std"] # Enable to use APIs that require `std`. # This is enabled by default. # # NOTE: Disabling `std` feature is not supported yet. std = ["crossbeam-epoch/std", "crossbeam-utils/std"] [dependencies] crossbeam-epoch = { version = "0.9.17", path = "../crossbeam-epoch", default-features = false } crossbeam-utils = { version = "0.8.18", path = "../crossbeam-utils", default-features = false } [dev-dependencies] rand = "0.8" crossbeam-deque-0.8.5/LICENSE-APACHE000064400000000000000000000251371046102023000146510ustar 00000000000000 Apache License Version 2.0, January 2004 http://www.apache.org/licenses/ TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 1. 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See the License for the specific language governing permissions and limitations under the License. crossbeam-deque-0.8.5/LICENSE-MIT000064400000000000000000000021131046102023000143460ustar 00000000000000The MIT License (MIT) Copyright (c) 2019 The Crossbeam Project Developers Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. 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IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. crossbeam-deque-0.8.5/README.md000064400000000000000000000032121046102023000141720ustar 00000000000000# Crossbeam Deque [![Build Status](https://github.com/crossbeam-rs/crossbeam/workflows/CI/badge.svg)]( https://github.com/crossbeam-rs/crossbeam/actions) [![License](https://img.shields.io/badge/license-MIT_OR_Apache--2.0-blue.svg)]( https://github.com/crossbeam-rs/crossbeam/tree/master/crossbeam-deque#license) [![Cargo](https://img.shields.io/crates/v/crossbeam-deque.svg)]( https://crates.io/crates/crossbeam-deque) [![Documentation](https://docs.rs/crossbeam-deque/badge.svg)]( https://docs.rs/crossbeam-deque) [![Rust 1.61+](https://img.shields.io/badge/rust-1.61+-lightgray.svg)]( https://www.rust-lang.org) [![chat](https://img.shields.io/discord/569610676205781012.svg?logo=discord)](https://discord.com/invite/JXYwgWZ) This crate provides work-stealing deques, which are primarily intended for building task schedulers. ## Usage Add this to your `Cargo.toml`: ```toml [dependencies] crossbeam-deque = "0.8" ``` ## Compatibility Crossbeam Deque supports stable Rust releases going back at least six months, and every time the minimum supported Rust version is increased, a new minor version is released. Currently, the minimum supported Rust version is 1.61. ## License Licensed under either of * Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0) * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT) at your option. #### Contribution Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions. crossbeam-deque-0.8.5/src/deque.rs000064400000000000000000002164441046102023000151700ustar 00000000000000use std::cell::{Cell, UnsafeCell}; use std::cmp; use std::fmt; use std::marker::PhantomData; use std::mem::{self, MaybeUninit}; use std::ptr; use std::slice; use std::sync::atomic::{self, AtomicIsize, AtomicPtr, AtomicUsize, Ordering}; use std::sync::Arc; use crossbeam_epoch::{self as epoch, Atomic, Owned}; use crossbeam_utils::{Backoff, CachePadded}; // Minimum buffer capacity. const MIN_CAP: usize = 64; // Maximum number of tasks that can be stolen in `steal_batch()` and `steal_batch_and_pop()`. const MAX_BATCH: usize = 32; // If a buffer of at least this size is retired, thread-local garbage is flushed so that it gets // deallocated as soon as possible. const FLUSH_THRESHOLD_BYTES: usize = 1 << 10; /// A buffer that holds tasks in a worker queue. /// /// This is just a pointer to the buffer and its length - dropping an instance of this struct will /// *not* deallocate the buffer. struct Buffer { /// Pointer to the allocated memory. ptr: *mut T, /// Capacity of the buffer. Always a power of two. cap: usize, } unsafe impl Send for Buffer {} impl Buffer { /// Allocates a new buffer with the specified capacity. fn alloc(cap: usize) -> Buffer { debug_assert_eq!(cap, cap.next_power_of_two()); let ptr = Box::into_raw( (0..cap) .map(|_| MaybeUninit::::uninit()) .collect::>(), ) .cast::(); Buffer { ptr, cap } } /// Deallocates the buffer. unsafe fn dealloc(self) { drop(Box::from_raw(slice::from_raw_parts_mut( self.ptr.cast::>(), self.cap, ))); } /// Returns a pointer to the task at the specified `index`. unsafe fn at(&self, index: isize) -> *mut T { // `self.cap` is always a power of two. // We do all the loads at `MaybeUninit` because we might realize, after loading, that we // don't actually have the right to access this memory. self.ptr.offset(index & (self.cap - 1) as isize) } /// Writes `task` into the specified `index`. /// /// This method might be concurrently called with another `read` at the same index, which is /// technically speaking a data race and therefore UB. We should use an atomic store here, but /// that would be more expensive and difficult to implement generically for all types `T`. /// Hence, as a hack, we use a volatile write instead. unsafe fn write(&self, index: isize, task: MaybeUninit) { ptr::write_volatile(self.at(index).cast::>(), task) } /// Reads a task from the specified `index`. /// /// This method might be concurrently called with another `write` at the same index, which is /// technically speaking a data race and therefore UB. We should use an atomic load here, but /// that would be more expensive and difficult to implement generically for all types `T`. /// Hence, as a hack, we use a volatile load instead. unsafe fn read(&self, index: isize) -> MaybeUninit { ptr::read_volatile(self.at(index).cast::>()) } } impl Clone for Buffer { fn clone(&self) -> Buffer { *self } } impl Copy for Buffer {} /// Internal queue data shared between the worker and stealers. /// /// The implementation is based on the following work: /// /// 1. [Chase and Lev. Dynamic circular work-stealing deque. SPAA 2005.][chase-lev] /// 2. [Le, Pop, Cohen, and Nardelli. Correct and efficient work-stealing for weak memory models. /// PPoPP 2013.][weak-mem] /// 3. [Norris and Demsky. CDSchecker: checking concurrent data structures written with C/C++ /// atomics. OOPSLA 2013.][checker] /// /// [chase-lev]: https://dl.acm.org/citation.cfm?id=1073974 /// [weak-mem]: https://dl.acm.org/citation.cfm?id=2442524 /// [checker]: https://dl.acm.org/citation.cfm?id=2509514 struct Inner { /// The front index. front: AtomicIsize, /// The back index. back: AtomicIsize, /// The underlying buffer. buffer: CachePadded>>, } impl Drop for Inner { fn drop(&mut self) { // Load the back index, front index, and buffer. let b = *self.back.get_mut(); let f = *self.front.get_mut(); unsafe { let buffer = self.buffer.load(Ordering::Relaxed, epoch::unprotected()); // Go through the buffer from front to back and drop all tasks in the queue. let mut i = f; while i != b { buffer.deref().at(i).drop_in_place(); i = i.wrapping_add(1); } // Free the memory allocated by the buffer. buffer.into_owned().into_box().dealloc(); } } } /// Worker queue flavor: FIFO or LIFO. #[derive(Clone, Copy, Debug, Eq, PartialEq)] enum Flavor { /// The first-in first-out flavor. Fifo, /// The last-in first-out flavor. Lifo, } /// A worker queue. /// /// This is a FIFO or LIFO queue that is owned by a single thread, but other threads may steal /// tasks from it. Task schedulers typically create a single worker queue per thread. /// /// # Examples /// /// A FIFO worker: /// /// ``` /// use crossbeam_deque::{Steal, Worker}; /// /// let w = Worker::new_fifo(); /// let s = w.stealer(); /// /// w.push(1); /// w.push(2); /// w.push(3); /// /// assert_eq!(s.steal(), Steal::Success(1)); /// assert_eq!(w.pop(), Some(2)); /// assert_eq!(w.pop(), Some(3)); /// ``` /// /// A LIFO worker: /// /// ``` /// use crossbeam_deque::{Steal, Worker}; /// /// let w = Worker::new_lifo(); /// let s = w.stealer(); /// /// w.push(1); /// w.push(2); /// w.push(3); /// /// assert_eq!(s.steal(), Steal::Success(1)); /// assert_eq!(w.pop(), Some(3)); /// assert_eq!(w.pop(), Some(2)); /// ``` pub struct Worker { /// A reference to the inner representation of the queue. inner: Arc>>, /// A copy of `inner.buffer` for quick access. buffer: Cell>, /// The flavor of the queue. flavor: Flavor, /// Indicates that the worker cannot be shared among threads. _marker: PhantomData<*mut ()>, // !Send + !Sync } unsafe impl Send for Worker {} impl Worker { /// Creates a FIFO worker queue. /// /// Tasks are pushed and popped from opposite ends. /// /// # Examples /// /// ``` /// use crossbeam_deque::Worker; /// /// let w = Worker::::new_fifo(); /// ``` pub fn new_fifo() -> Worker { let buffer = Buffer::alloc(MIN_CAP); let inner = Arc::new(CachePadded::new(Inner { front: AtomicIsize::new(0), back: AtomicIsize::new(0), buffer: CachePadded::new(Atomic::new(buffer)), })); Worker { inner, buffer: Cell::new(buffer), flavor: Flavor::Fifo, _marker: PhantomData, } } /// Creates a LIFO worker queue. /// /// Tasks are pushed and popped from the same end. /// /// # Examples /// /// ``` /// use crossbeam_deque::Worker; /// /// let w = Worker::::new_lifo(); /// ``` pub fn new_lifo() -> Worker { let buffer = Buffer::alloc(MIN_CAP); let inner = Arc::new(CachePadded::new(Inner { front: AtomicIsize::new(0), back: AtomicIsize::new(0), buffer: CachePadded::new(Atomic::new(buffer)), })); Worker { inner, buffer: Cell::new(buffer), flavor: Flavor::Lifo, _marker: PhantomData, } } /// Creates a stealer for this queue. /// /// The returned stealer can be shared among threads and cloned. /// /// # Examples /// /// ``` /// use crossbeam_deque::Worker; /// /// let w = Worker::::new_lifo(); /// let s = w.stealer(); /// ``` pub fn stealer(&self) -> Stealer { Stealer { inner: self.inner.clone(), flavor: self.flavor, } } /// Resizes the internal buffer to the new capacity of `new_cap`. #[cold] unsafe fn resize(&self, new_cap: usize) { // Load the back index, front index, and buffer. let b = self.inner.back.load(Ordering::Relaxed); let f = self.inner.front.load(Ordering::Relaxed); let buffer = self.buffer.get(); // Allocate a new buffer and copy data from the old buffer to the new one. let new = Buffer::alloc(new_cap); let mut i = f; while i != b { ptr::copy_nonoverlapping(buffer.at(i), new.at(i), 1); i = i.wrapping_add(1); } let guard = &epoch::pin(); // Replace the old buffer with the new one. self.buffer.replace(new); let old = self.inner .buffer .swap(Owned::new(new).into_shared(guard), Ordering::Release, guard); // Destroy the old buffer later. guard.defer_unchecked(move || old.into_owned().into_box().dealloc()); // If the buffer is very large, then flush the thread-local garbage in order to deallocate // it as soon as possible. if mem::size_of::() * new_cap >= FLUSH_THRESHOLD_BYTES { guard.flush(); } } /// Reserves enough capacity so that `reserve_cap` tasks can be pushed without growing the /// buffer. fn reserve(&self, reserve_cap: usize) { if reserve_cap > 0 { // Compute the current length. let b = self.inner.back.load(Ordering::Relaxed); let f = self.inner.front.load(Ordering::SeqCst); let len = b.wrapping_sub(f) as usize; // The current capacity. let cap = self.buffer.get().cap; // Is there enough capacity to push `reserve_cap` tasks? if cap - len < reserve_cap { // Keep doubling the capacity as much as is needed. let mut new_cap = cap * 2; while new_cap - len < reserve_cap { new_cap *= 2; } // Resize the buffer. unsafe { self.resize(new_cap); } } } } /// Returns `true` if the queue is empty. /// /// ``` /// use crossbeam_deque::Worker; /// /// let w = Worker::new_lifo(); /// /// assert!(w.is_empty()); /// w.push(1); /// assert!(!w.is_empty()); /// ``` pub fn is_empty(&self) -> bool { let b = self.inner.back.load(Ordering::Relaxed); let f = self.inner.front.load(Ordering::SeqCst); b.wrapping_sub(f) <= 0 } /// Returns the number of tasks in the deque. /// /// ``` /// use crossbeam_deque::Worker; /// /// let w = Worker::new_lifo(); /// /// assert_eq!(w.len(), 0); /// w.push(1); /// assert_eq!(w.len(), 1); /// w.push(1); /// assert_eq!(w.len(), 2); /// ``` pub fn len(&self) -> usize { let b = self.inner.back.load(Ordering::Relaxed); let f = self.inner.front.load(Ordering::SeqCst); b.wrapping_sub(f).max(0) as usize } /// Pushes a task into the queue. /// /// # Examples /// /// ``` /// use crossbeam_deque::Worker; /// /// let w = Worker::new_lifo(); /// w.push(1); /// w.push(2); /// ``` pub fn push(&self, task: T) { // Load the back index, front index, and buffer. let b = self.inner.back.load(Ordering::Relaxed); let f = self.inner.front.load(Ordering::Acquire); let mut buffer = self.buffer.get(); // Calculate the length of the queue. let len = b.wrapping_sub(f); // Is the queue full? if len >= buffer.cap as isize { // Yes. Grow the underlying buffer. unsafe { self.resize(2 * buffer.cap); } buffer = self.buffer.get(); } // Write `task` into the slot. unsafe { buffer.write(b, MaybeUninit::new(task)); } atomic::fence(Ordering::Release); // Increment the back index. // // This ordering could be `Relaxed`, but then thread sanitizer would falsely report data // races because it doesn't understand fences. self.inner.back.store(b.wrapping_add(1), Ordering::Release); } /// Pops a task from the queue. /// /// # Examples /// /// ``` /// use crossbeam_deque::Worker; /// /// let w = Worker::new_fifo(); /// w.push(1); /// w.push(2); /// /// assert_eq!(w.pop(), Some(1)); /// assert_eq!(w.pop(), Some(2)); /// assert_eq!(w.pop(), None); /// ``` pub fn pop(&self) -> Option { // Load the back and front index. let b = self.inner.back.load(Ordering::Relaxed); let f = self.inner.front.load(Ordering::Relaxed); // Calculate the length of the queue. let len = b.wrapping_sub(f); // Is the queue empty? if len <= 0 { return None; } match self.flavor { // Pop from the front of the queue. Flavor::Fifo => { // Try incrementing the front index to pop the task. let f = self.inner.front.fetch_add(1, Ordering::SeqCst); let new_f = f.wrapping_add(1); if b.wrapping_sub(new_f) < 0 { self.inner.front.store(f, Ordering::Relaxed); return None; } unsafe { // Read the popped task. let buffer = self.buffer.get(); let task = buffer.read(f).assume_init(); // Shrink the buffer if `len - 1` is less than one fourth of the capacity. if buffer.cap > MIN_CAP && len <= buffer.cap as isize / 4 { self.resize(buffer.cap / 2); } Some(task) } } // Pop from the back of the queue. Flavor::Lifo => { // Decrement the back index. let b = b.wrapping_sub(1); self.inner.back.store(b, Ordering::Relaxed); atomic::fence(Ordering::SeqCst); // Load the front index. let f = self.inner.front.load(Ordering::Relaxed); // Compute the length after the back index was decremented. let len = b.wrapping_sub(f); if len < 0 { // The queue is empty. Restore the back index to the original task. self.inner.back.store(b.wrapping_add(1), Ordering::Relaxed); None } else { // Read the task to be popped. let buffer = self.buffer.get(); let mut task = unsafe { Some(buffer.read(b)) }; // Are we popping the last task from the queue? if len == 0 { // Try incrementing the front index. if self .inner .front .compare_exchange( f, f.wrapping_add(1), Ordering::SeqCst, Ordering::Relaxed, ) .is_err() { // Failed. We didn't pop anything. Reset to `None`. task.take(); } // Restore the back index to the original task. self.inner.back.store(b.wrapping_add(1), Ordering::Relaxed); } else { // Shrink the buffer if `len` is less than one fourth of the capacity. if buffer.cap > MIN_CAP && len < buffer.cap as isize / 4 { unsafe { self.resize(buffer.cap / 2); } } } task.map(|t| unsafe { t.assume_init() }) } } } } } impl fmt::Debug for Worker { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { f.pad("Worker { .. }") } } /// A stealer handle of a worker queue. /// /// Stealers can be shared among threads. /// /// Task schedulers typically have a single worker queue per worker thread. /// /// # Examples /// /// ``` /// use crossbeam_deque::{Steal, Worker}; /// /// let w = Worker::new_lifo(); /// w.push(1); /// w.push(2); /// /// let s = w.stealer(); /// assert_eq!(s.steal(), Steal::Success(1)); /// assert_eq!(s.steal(), Steal::Success(2)); /// assert_eq!(s.steal(), Steal::Empty); /// ``` pub struct Stealer { /// A reference to the inner representation of the queue. inner: Arc>>, /// The flavor of the queue. flavor: Flavor, } unsafe impl Send for Stealer {} unsafe impl Sync for Stealer {} impl Stealer { /// Returns `true` if the queue is empty. /// /// ``` /// use crossbeam_deque::Worker; /// /// let w = Worker::new_lifo(); /// let s = w.stealer(); /// /// assert!(s.is_empty()); /// w.push(1); /// assert!(!s.is_empty()); /// ``` pub fn is_empty(&self) -> bool { let f = self.inner.front.load(Ordering::Acquire); atomic::fence(Ordering::SeqCst); let b = self.inner.back.load(Ordering::Acquire); b.wrapping_sub(f) <= 0 } /// Returns the number of tasks in the deque. /// /// ``` /// use crossbeam_deque::Worker; /// /// let w = Worker::new_lifo(); /// let s = w.stealer(); /// /// assert_eq!(s.len(), 0); /// w.push(1); /// assert_eq!(s.len(), 1); /// w.push(2); /// assert_eq!(s.len(), 2); /// ``` pub fn len(&self) -> usize { let f = self.inner.front.load(Ordering::Acquire); atomic::fence(Ordering::SeqCst); let b = self.inner.back.load(Ordering::Acquire); b.wrapping_sub(f).max(0) as usize } /// Steals a task from the queue. /// /// # Examples /// /// ``` /// use crossbeam_deque::{Steal, Worker}; /// /// let w = Worker::new_lifo(); /// w.push(1); /// w.push(2); /// /// let s = w.stealer(); /// assert_eq!(s.steal(), Steal::Success(1)); /// assert_eq!(s.steal(), Steal::Success(2)); /// ``` pub fn steal(&self) -> Steal { // Load the front index. let f = self.inner.front.load(Ordering::Acquire); // A SeqCst fence is needed here. // // If the current thread is already pinned (reentrantly), we must manually issue the // fence. Otherwise, the following pinning will issue the fence anyway, so we don't // have to. if epoch::is_pinned() { atomic::fence(Ordering::SeqCst); } let guard = &epoch::pin(); // Load the back index. let b = self.inner.back.load(Ordering::Acquire); // Is the queue empty? if b.wrapping_sub(f) <= 0 { return Steal::Empty; } // Load the buffer and read the task at the front. let buffer = self.inner.buffer.load(Ordering::Acquire, guard); let task = unsafe { buffer.deref().read(f) }; // Try incrementing the front index to steal the task. // If the buffer has been swapped or the increment fails, we retry. if self.inner.buffer.load(Ordering::Acquire, guard) != buffer || self .inner .front .compare_exchange(f, f.wrapping_add(1), Ordering::SeqCst, Ordering::Relaxed) .is_err() { // We didn't steal this task, forget it. return Steal::Retry; } // Return the stolen task. Steal::Success(unsafe { task.assume_init() }) } /// Steals a batch of tasks and pushes them into another worker. /// /// How many tasks exactly will be stolen is not specified. That said, this method will try to /// steal around half of the tasks in the queue, but also not more than some constant limit. /// /// # Examples /// /// ``` /// use crossbeam_deque::Worker; /// /// let w1 = Worker::new_fifo(); /// w1.push(1); /// w1.push(2); /// w1.push(3); /// w1.push(4); /// /// let s = w1.stealer(); /// let w2 = Worker::new_fifo(); /// /// let _ = s.steal_batch(&w2); /// assert_eq!(w2.pop(), Some(1)); /// assert_eq!(w2.pop(), Some(2)); /// ``` pub fn steal_batch(&self, dest: &Worker) -> Steal<()> { self.steal_batch_with_limit(dest, MAX_BATCH) } /// Steals no more than `limit` of tasks and pushes them into another worker. /// /// How many tasks exactly will be stolen is not specified. That said, this method will try to /// steal around half of the tasks in the queue, but also not more than the given limit. /// /// # Examples /// /// ``` /// use crossbeam_deque::Worker; /// /// let w1 = Worker::new_fifo(); /// w1.push(1); /// w1.push(2); /// w1.push(3); /// w1.push(4); /// w1.push(5); /// w1.push(6); /// /// let s = w1.stealer(); /// let w2 = Worker::new_fifo(); /// /// let _ = s.steal_batch_with_limit(&w2, 2); /// assert_eq!(w2.pop(), Some(1)); /// assert_eq!(w2.pop(), Some(2)); /// assert_eq!(w2.pop(), None); /// /// w1.push(7); /// w1.push(8); /// // Setting a large limit does not guarantee that all elements will be popped. In this case, /// // half of the elements are currently popped, but the number of popped elements is considered /// // an implementation detail that may be changed in the future. /// let _ = s.steal_batch_with_limit(&w2, std::usize::MAX); /// assert_eq!(w2.len(), 3); /// ``` pub fn steal_batch_with_limit(&self, dest: &Worker, limit: usize) -> Steal<()> { assert!(limit > 0); if Arc::ptr_eq(&self.inner, &dest.inner) { if dest.is_empty() { return Steal::Empty; } else { return Steal::Success(()); } } // Load the front index. let mut f = self.inner.front.load(Ordering::Acquire); // A SeqCst fence is needed here. // // If the current thread is already pinned (reentrantly), we must manually issue the // fence. Otherwise, the following pinning will issue the fence anyway, so we don't // have to. if epoch::is_pinned() { atomic::fence(Ordering::SeqCst); } let guard = &epoch::pin(); // Load the back index. let b = self.inner.back.load(Ordering::Acquire); // Is the queue empty? let len = b.wrapping_sub(f); if len <= 0 { return Steal::Empty; } // Reserve capacity for the stolen batch. let batch_size = cmp::min((len as usize + 1) / 2, limit); dest.reserve(batch_size); let mut batch_size = batch_size as isize; // Get the destination buffer and back index. let dest_buffer = dest.buffer.get(); let mut dest_b = dest.inner.back.load(Ordering::Relaxed); // Load the buffer. let buffer = self.inner.buffer.load(Ordering::Acquire, guard); match self.flavor { // Steal a batch of tasks from the front at once. Flavor::Fifo => { // Copy the batch from the source to the destination buffer. match dest.flavor { Flavor::Fifo => { for i in 0..batch_size { unsafe { let task = buffer.deref().read(f.wrapping_add(i)); dest_buffer.write(dest_b.wrapping_add(i), task); } } } Flavor::Lifo => { for i in 0..batch_size { unsafe { let task = buffer.deref().read(f.wrapping_add(i)); dest_buffer.write(dest_b.wrapping_add(batch_size - 1 - i), task); } } } } // Try incrementing the front index to steal the batch. // If the buffer has been swapped or the increment fails, we retry. if self.inner.buffer.load(Ordering::Acquire, guard) != buffer || self .inner .front .compare_exchange( f, f.wrapping_add(batch_size), Ordering::SeqCst, Ordering::Relaxed, ) .is_err() { return Steal::Retry; } dest_b = dest_b.wrapping_add(batch_size); } // Steal a batch of tasks from the front one by one. Flavor::Lifo => { // This loop may modify the batch_size, which triggers a clippy lint warning. // Use a new variable to avoid the warning, and to make it clear we aren't // modifying the loop exit condition during iteration. let original_batch_size = batch_size; for i in 0..original_batch_size { // If this is not the first steal, check whether the queue is empty. if i > 0 { // We've already got the current front index. Now execute the fence to // synchronize with other threads. atomic::fence(Ordering::SeqCst); // Load the back index. let b = self.inner.back.load(Ordering::Acquire); // Is the queue empty? if b.wrapping_sub(f) <= 0 { batch_size = i; break; } } // Read the task at the front. let task = unsafe { buffer.deref().read(f) }; // Try incrementing the front index to steal the task. // If the buffer has been swapped or the increment fails, we retry. if self.inner.buffer.load(Ordering::Acquire, guard) != buffer || self .inner .front .compare_exchange( f, f.wrapping_add(1), Ordering::SeqCst, Ordering::Relaxed, ) .is_err() { // We didn't steal this task, forget it and break from the loop. batch_size = i; break; } // Write the stolen task into the destination buffer. unsafe { dest_buffer.write(dest_b, task); } // Move the source front index and the destination back index one step forward. f = f.wrapping_add(1); dest_b = dest_b.wrapping_add(1); } // If we didn't steal anything, the operation needs to be retried. if batch_size == 0 { return Steal::Retry; } // If stealing into a FIFO queue, stolen tasks need to be reversed. if dest.flavor == Flavor::Fifo { for i in 0..batch_size / 2 { unsafe { let i1 = dest_b.wrapping_sub(batch_size - i); let i2 = dest_b.wrapping_sub(i + 1); let t1 = dest_buffer.read(i1); let t2 = dest_buffer.read(i2); dest_buffer.write(i1, t2); dest_buffer.write(i2, t1); } } } } } atomic::fence(Ordering::Release); // Update the back index in the destination queue. // // This ordering could be `Relaxed`, but then thread sanitizer would falsely report data // races because it doesn't understand fences. dest.inner.back.store(dest_b, Ordering::Release); // Return with success. Steal::Success(()) } /// Steals a batch of tasks, pushes them into another worker, and pops a task from that worker. /// /// How many tasks exactly will be stolen is not specified. That said, this method will try to /// steal around half of the tasks in the queue, but also not more than some constant limit. /// /// # Examples /// /// ``` /// use crossbeam_deque::{Steal, Worker}; /// /// let w1 = Worker::new_fifo(); /// w1.push(1); /// w1.push(2); /// w1.push(3); /// w1.push(4); /// /// let s = w1.stealer(); /// let w2 = Worker::new_fifo(); /// /// assert_eq!(s.steal_batch_and_pop(&w2), Steal::Success(1)); /// assert_eq!(w2.pop(), Some(2)); /// ``` pub fn steal_batch_and_pop(&self, dest: &Worker) -> Steal { self.steal_batch_with_limit_and_pop(dest, MAX_BATCH) } /// Steals no more than `limit` of tasks, pushes them into another worker, and pops a task from /// that worker. /// /// How many tasks exactly will be stolen is not specified. That said, this method will try to /// steal around half of the tasks in the queue, but also not more than the given limit. /// /// # Examples /// /// ``` /// use crossbeam_deque::{Steal, Worker}; /// /// let w1 = Worker::new_fifo(); /// w1.push(1); /// w1.push(2); /// w1.push(3); /// w1.push(4); /// w1.push(5); /// w1.push(6); /// /// let s = w1.stealer(); /// let w2 = Worker::new_fifo(); /// /// assert_eq!(s.steal_batch_with_limit_and_pop(&w2, 2), Steal::Success(1)); /// assert_eq!(w2.pop(), Some(2)); /// assert_eq!(w2.pop(), None); /// /// w1.push(7); /// w1.push(8); /// // Setting a large limit does not guarantee that all elements will be popped. In this case, /// // half of the elements are currently popped, but the number of popped elements is considered /// // an implementation detail that may be changed in the future. /// assert_eq!(s.steal_batch_with_limit_and_pop(&w2, std::usize::MAX), Steal::Success(3)); /// assert_eq!(w2.pop(), Some(4)); /// assert_eq!(w2.pop(), Some(5)); /// assert_eq!(w2.pop(), None); /// ``` pub fn steal_batch_with_limit_and_pop(&self, dest: &Worker, limit: usize) -> Steal { assert!(limit > 0); if Arc::ptr_eq(&self.inner, &dest.inner) { match dest.pop() { None => return Steal::Empty, Some(task) => return Steal::Success(task), } } // Load the front index. let mut f = self.inner.front.load(Ordering::Acquire); // A SeqCst fence is needed here. // // If the current thread is already pinned (reentrantly), we must manually issue the // fence. Otherwise, the following pinning will issue the fence anyway, so we don't // have to. if epoch::is_pinned() { atomic::fence(Ordering::SeqCst); } let guard = &epoch::pin(); // Load the back index. let b = self.inner.back.load(Ordering::Acquire); // Is the queue empty? let len = b.wrapping_sub(f); if len <= 0 { return Steal::Empty; } // Reserve capacity for the stolen batch. let batch_size = cmp::min((len as usize - 1) / 2, limit - 1); dest.reserve(batch_size); let mut batch_size = batch_size as isize; // Get the destination buffer and back index. let dest_buffer = dest.buffer.get(); let mut dest_b = dest.inner.back.load(Ordering::Relaxed); // Load the buffer let buffer = self.inner.buffer.load(Ordering::Acquire, guard); // Read the task at the front. let mut task = unsafe { buffer.deref().read(f) }; match self.flavor { // Steal a batch of tasks from the front at once. Flavor::Fifo => { // Copy the batch from the source to the destination buffer. match dest.flavor { Flavor::Fifo => { for i in 0..batch_size { unsafe { let task = buffer.deref().read(f.wrapping_add(i + 1)); dest_buffer.write(dest_b.wrapping_add(i), task); } } } Flavor::Lifo => { for i in 0..batch_size { unsafe { let task = buffer.deref().read(f.wrapping_add(i + 1)); dest_buffer.write(dest_b.wrapping_add(batch_size - 1 - i), task); } } } } // Try incrementing the front index to steal the task. // If the buffer has been swapped or the increment fails, we retry. if self.inner.buffer.load(Ordering::Acquire, guard) != buffer || self .inner .front .compare_exchange( f, f.wrapping_add(batch_size + 1), Ordering::SeqCst, Ordering::Relaxed, ) .is_err() { // We didn't steal this task, forget it. return Steal::Retry; } dest_b = dest_b.wrapping_add(batch_size); } // Steal a batch of tasks from the front one by one. Flavor::Lifo => { // Try incrementing the front index to steal the task. if self .inner .front .compare_exchange(f, f.wrapping_add(1), Ordering::SeqCst, Ordering::Relaxed) .is_err() { // We didn't steal this task, forget it. return Steal::Retry; } // Move the front index one step forward. f = f.wrapping_add(1); // Repeat the same procedure for the batch steals. // // This loop may modify the batch_size, which triggers a clippy lint warning. // Use a new variable to avoid the warning, and to make it clear we aren't // modifying the loop exit condition during iteration. let original_batch_size = batch_size; for i in 0..original_batch_size { // We've already got the current front index. Now execute the fence to // synchronize with other threads. atomic::fence(Ordering::SeqCst); // Load the back index. let b = self.inner.back.load(Ordering::Acquire); // Is the queue empty? if b.wrapping_sub(f) <= 0 { batch_size = i; break; } // Read the task at the front. let tmp = unsafe { buffer.deref().read(f) }; // Try incrementing the front index to steal the task. // If the buffer has been swapped or the increment fails, we retry. if self.inner.buffer.load(Ordering::Acquire, guard) != buffer || self .inner .front .compare_exchange( f, f.wrapping_add(1), Ordering::SeqCst, Ordering::Relaxed, ) .is_err() { // We didn't steal this task, forget it and break from the loop. batch_size = i; break; } // Write the previously stolen task into the destination buffer. unsafe { dest_buffer.write(dest_b, mem::replace(&mut task, tmp)); } // Move the source front index and the destination back index one step forward. f = f.wrapping_add(1); dest_b = dest_b.wrapping_add(1); } // If stealing into a FIFO queue, stolen tasks need to be reversed. if dest.flavor == Flavor::Fifo { for i in 0..batch_size / 2 { unsafe { let i1 = dest_b.wrapping_sub(batch_size - i); let i2 = dest_b.wrapping_sub(i + 1); let t1 = dest_buffer.read(i1); let t2 = dest_buffer.read(i2); dest_buffer.write(i1, t2); dest_buffer.write(i2, t1); } } } } } atomic::fence(Ordering::Release); // Update the back index in the destination queue. // // This ordering could be `Relaxed`, but then thread sanitizer would falsely report data // races because it doesn't understand fences. dest.inner.back.store(dest_b, Ordering::Release); // Return with success. Steal::Success(unsafe { task.assume_init() }) } } impl Clone for Stealer { fn clone(&self) -> Stealer { Stealer { inner: self.inner.clone(), flavor: self.flavor, } } } impl fmt::Debug for Stealer { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { f.pad("Stealer { .. }") } } // Bits indicating the state of a slot: // * If a task has been written into the slot, `WRITE` is set. // * If a task has been read from the slot, `READ` is set. // * If the block is being destroyed, `DESTROY` is set. const WRITE: usize = 1; const READ: usize = 2; const DESTROY: usize = 4; // Each block covers one "lap" of indices. const LAP: usize = 64; // The maximum number of values a block can hold. const BLOCK_CAP: usize = LAP - 1; // How many lower bits are reserved for metadata. const SHIFT: usize = 1; // Indicates that the block is not the last one. const HAS_NEXT: usize = 1; /// A slot in a block. struct Slot { /// The task. task: UnsafeCell>, /// The state of the slot. state: AtomicUsize, } impl Slot { const UNINIT: Self = Self { task: UnsafeCell::new(MaybeUninit::uninit()), state: AtomicUsize::new(0), }; /// Waits until a task is written into the slot. fn wait_write(&self) { let backoff = Backoff::new(); while self.state.load(Ordering::Acquire) & WRITE == 0 { backoff.snooze(); } } } /// A block in a linked list. /// /// Each block in the list can hold up to `BLOCK_CAP` values. struct Block { /// The next block in the linked list. next: AtomicPtr>, /// Slots for values. slots: [Slot; BLOCK_CAP], } impl Block { /// Creates an empty block that starts at `start_index`. fn new() -> Block { Self { next: AtomicPtr::new(ptr::null_mut()), slots: [Slot::UNINIT; BLOCK_CAP], } } /// Waits until the next pointer is set. fn wait_next(&self) -> *mut Block { let backoff = Backoff::new(); loop { let next = self.next.load(Ordering::Acquire); if !next.is_null() { return next; } backoff.snooze(); } } /// Sets the `DESTROY` bit in slots starting from `start` and destroys the block. unsafe fn destroy(this: *mut Block, count: usize) { // It is not necessary to set the `DESTROY` bit in the last slot because that slot has // begun destruction of the block. for i in (0..count).rev() { let slot = (*this).slots.get_unchecked(i); // Mark the `DESTROY` bit if a thread is still using the slot. if slot.state.load(Ordering::Acquire) & READ == 0 && slot.state.fetch_or(DESTROY, Ordering::AcqRel) & READ == 0 { // If a thread is still using the slot, it will continue destruction of the block. return; } } // No thread is using the block, now it is safe to destroy it. drop(Box::from_raw(this)); } } /// A position in a queue. struct Position { /// The index in the queue. index: AtomicUsize, /// The block in the linked list. block: AtomicPtr>, } /// An injector queue. /// /// This is a FIFO queue that can be shared among multiple threads. Task schedulers typically have /// a single injector queue, which is the entry point for new tasks. /// /// # Examples /// /// ``` /// use crossbeam_deque::{Injector, Steal}; /// /// let q = Injector::new(); /// q.push(1); /// q.push(2); /// /// assert_eq!(q.steal(), Steal::Success(1)); /// assert_eq!(q.steal(), Steal::Success(2)); /// assert_eq!(q.steal(), Steal::Empty); /// ``` pub struct Injector { /// The head of the queue. head: CachePadded>, /// The tail of the queue. tail: CachePadded>, /// Indicates that dropping a `Injector` may drop values of type `T`. _marker: PhantomData, } unsafe impl Send for Injector {} unsafe impl Sync for Injector {} impl Default for Injector { fn default() -> Self { let block = Box::into_raw(Box::new(Block::::new())); Self { head: CachePadded::new(Position { block: AtomicPtr::new(block), index: AtomicUsize::new(0), }), tail: CachePadded::new(Position { block: AtomicPtr::new(block), index: AtomicUsize::new(0), }), _marker: PhantomData, } } } impl Injector { /// Creates a new injector queue. /// /// # Examples /// /// ``` /// use crossbeam_deque::Injector; /// /// let q = Injector::::new(); /// ``` pub fn new() -> Injector { Self::default() } /// Pushes a task into the queue. /// /// # Examples /// /// ``` /// use crossbeam_deque::Injector; /// /// let w = Injector::new(); /// w.push(1); /// w.push(2); /// ``` pub fn push(&self, task: T) { let backoff = Backoff::new(); let mut tail = self.tail.index.load(Ordering::Acquire); let mut block = self.tail.block.load(Ordering::Acquire); let mut next_block = None; loop { // Calculate the offset of the index into the block. let offset = (tail >> SHIFT) % LAP; // If we reached the end of the block, wait until the next one is installed. if offset == BLOCK_CAP { backoff.snooze(); tail = self.tail.index.load(Ordering::Acquire); block = self.tail.block.load(Ordering::Acquire); continue; } // If we're going to have to install the next block, allocate it in advance in order to // make the wait for other threads as short as possible. if offset + 1 == BLOCK_CAP && next_block.is_none() { next_block = Some(Box::new(Block::::new())); } let new_tail = tail + (1 << SHIFT); // Try advancing the tail forward. match self.tail.index.compare_exchange_weak( tail, new_tail, Ordering::SeqCst, Ordering::Acquire, ) { Ok(_) => unsafe { // If we've reached the end of the block, install the next one. if offset + 1 == BLOCK_CAP { let next_block = Box::into_raw(next_block.unwrap()); let next_index = new_tail.wrapping_add(1 << SHIFT); self.tail.block.store(next_block, Ordering::Release); self.tail.index.store(next_index, Ordering::Release); (*block).next.store(next_block, Ordering::Release); } // Write the task into the slot. let slot = (*block).slots.get_unchecked(offset); slot.task.get().write(MaybeUninit::new(task)); slot.state.fetch_or(WRITE, Ordering::Release); return; }, Err(t) => { tail = t; block = self.tail.block.load(Ordering::Acquire); backoff.spin(); } } } } /// Steals a task from the queue. /// /// # Examples /// /// ``` /// use crossbeam_deque::{Injector, Steal}; /// /// let q = Injector::new(); /// q.push(1); /// q.push(2); /// /// assert_eq!(q.steal(), Steal::Success(1)); /// assert_eq!(q.steal(), Steal::Success(2)); /// assert_eq!(q.steal(), Steal::Empty); /// ``` pub fn steal(&self) -> Steal { let mut head; let mut block; let mut offset; let backoff = Backoff::new(); loop { head = self.head.index.load(Ordering::Acquire); block = self.head.block.load(Ordering::Acquire); // Calculate the offset of the index into the block. offset = (head >> SHIFT) % LAP; // If we reached the end of the block, wait until the next one is installed. if offset == BLOCK_CAP { backoff.snooze(); } else { break; } } let mut new_head = head + (1 << SHIFT); if new_head & HAS_NEXT == 0 { atomic::fence(Ordering::SeqCst); let tail = self.tail.index.load(Ordering::Relaxed); // If the tail equals the head, that means the queue is empty. if head >> SHIFT == tail >> SHIFT { return Steal::Empty; } // If head and tail are not in the same block, set `HAS_NEXT` in head. if (head >> SHIFT) / LAP != (tail >> SHIFT) / LAP { new_head |= HAS_NEXT; } } // Try moving the head index forward. if self .head .index .compare_exchange_weak(head, new_head, Ordering::SeqCst, Ordering::Acquire) .is_err() { return Steal::Retry; } unsafe { // If we've reached the end of the block, move to the next one. if offset + 1 == BLOCK_CAP { let next = (*block).wait_next(); let mut next_index = (new_head & !HAS_NEXT).wrapping_add(1 << SHIFT); if !(*next).next.load(Ordering::Relaxed).is_null() { next_index |= HAS_NEXT; } self.head.block.store(next, Ordering::Release); self.head.index.store(next_index, Ordering::Release); } // Read the task. let slot = (*block).slots.get_unchecked(offset); slot.wait_write(); let task = slot.task.get().read().assume_init(); // Destroy the block if we've reached the end, or if another thread wanted to destroy // but couldn't because we were busy reading from the slot. if (offset + 1 == BLOCK_CAP) || (slot.state.fetch_or(READ, Ordering::AcqRel) & DESTROY != 0) { Block::destroy(block, offset); } Steal::Success(task) } } /// Steals a batch of tasks and pushes them into a worker. /// /// How many tasks exactly will be stolen is not specified. That said, this method will try to /// steal around half of the tasks in the queue, but also not more than some constant limit. /// /// # Examples /// /// ``` /// use crossbeam_deque::{Injector, Worker}; /// /// let q = Injector::new(); /// q.push(1); /// q.push(2); /// q.push(3); /// q.push(4); /// /// let w = Worker::new_fifo(); /// let _ = q.steal_batch(&w); /// assert_eq!(w.pop(), Some(1)); /// assert_eq!(w.pop(), Some(2)); /// ``` pub fn steal_batch(&self, dest: &Worker) -> Steal<()> { self.steal_batch_with_limit(dest, MAX_BATCH) } /// Steals no more than of tasks and pushes them into a worker. /// /// How many tasks exactly will be stolen is not specified. That said, this method will try to /// steal around half of the tasks in the queue, but also not more than some constant limit. /// /// # Examples /// /// ``` /// use crossbeam_deque::{Injector, Worker}; /// /// let q = Injector::new(); /// q.push(1); /// q.push(2); /// q.push(3); /// q.push(4); /// q.push(5); /// q.push(6); /// /// let w = Worker::new_fifo(); /// let _ = q.steal_batch_with_limit(&w, 2); /// assert_eq!(w.pop(), Some(1)); /// assert_eq!(w.pop(), Some(2)); /// assert_eq!(w.pop(), None); /// /// q.push(7); /// q.push(8); /// // Setting a large limit does not guarantee that all elements will be popped. In this case, /// // half of the elements are currently popped, but the number of popped elements is considered /// // an implementation detail that may be changed in the future. /// let _ = q.steal_batch_with_limit(&w, std::usize::MAX); /// assert_eq!(w.len(), 3); /// ``` pub fn steal_batch_with_limit(&self, dest: &Worker, limit: usize) -> Steal<()> { assert!(limit > 0); let mut head; let mut block; let mut offset; let backoff = Backoff::new(); loop { head = self.head.index.load(Ordering::Acquire); block = self.head.block.load(Ordering::Acquire); // Calculate the offset of the index into the block. offset = (head >> SHIFT) % LAP; // If we reached the end of the block, wait until the next one is installed. if offset == BLOCK_CAP { backoff.snooze(); } else { break; } } let mut new_head = head; let advance; if new_head & HAS_NEXT == 0 { atomic::fence(Ordering::SeqCst); let tail = self.tail.index.load(Ordering::Relaxed); // If the tail equals the head, that means the queue is empty. if head >> SHIFT == tail >> SHIFT { return Steal::Empty; } // If head and tail are not in the same block, set `HAS_NEXT` in head. Also, calculate // the right batch size to steal. if (head >> SHIFT) / LAP != (tail >> SHIFT) / LAP { new_head |= HAS_NEXT; // We can steal all tasks till the end of the block. advance = (BLOCK_CAP - offset).min(limit); } else { let len = (tail - head) >> SHIFT; // Steal half of the available tasks. advance = ((len + 1) / 2).min(limit); } } else { // We can steal all tasks till the end of the block. advance = (BLOCK_CAP - offset).min(limit); } new_head += advance << SHIFT; let new_offset = offset + advance; // Try moving the head index forward. if self .head .index .compare_exchange_weak(head, new_head, Ordering::SeqCst, Ordering::Acquire) .is_err() { return Steal::Retry; } // Reserve capacity for the stolen batch. let batch_size = new_offset - offset; dest.reserve(batch_size); // Get the destination buffer and back index. let dest_buffer = dest.buffer.get(); let dest_b = dest.inner.back.load(Ordering::Relaxed); unsafe { // If we've reached the end of the block, move to the next one. if new_offset == BLOCK_CAP { let next = (*block).wait_next(); let mut next_index = (new_head & !HAS_NEXT).wrapping_add(1 << SHIFT); if !(*next).next.load(Ordering::Relaxed).is_null() { next_index |= HAS_NEXT; } self.head.block.store(next, Ordering::Release); self.head.index.store(next_index, Ordering::Release); } // Copy values from the injector into the destination queue. match dest.flavor { Flavor::Fifo => { for i in 0..batch_size { // Read the task. let slot = (*block).slots.get_unchecked(offset + i); slot.wait_write(); let task = slot.task.get().read(); // Write it into the destination queue. dest_buffer.write(dest_b.wrapping_add(i as isize), task); } } Flavor::Lifo => { for i in 0..batch_size { // Read the task. let slot = (*block).slots.get_unchecked(offset + i); slot.wait_write(); let task = slot.task.get().read(); // Write it into the destination queue. dest_buffer.write(dest_b.wrapping_add((batch_size - 1 - i) as isize), task); } } } atomic::fence(Ordering::Release); // Update the back index in the destination queue. // // This ordering could be `Relaxed`, but then thread sanitizer would falsely report // data races because it doesn't understand fences. dest.inner .back .store(dest_b.wrapping_add(batch_size as isize), Ordering::Release); // Destroy the block if we've reached the end, or if another thread wanted to destroy // but couldn't because we were busy reading from the slot. if new_offset == BLOCK_CAP { Block::destroy(block, offset); } else { for i in offset..new_offset { let slot = (*block).slots.get_unchecked(i); if slot.state.fetch_or(READ, Ordering::AcqRel) & DESTROY != 0 { Block::destroy(block, offset); break; } } } Steal::Success(()) } } /// Steals a batch of tasks, pushes them into a worker, and pops a task from that worker. /// /// How many tasks exactly will be stolen is not specified. That said, this method will try to /// steal around half of the tasks in the queue, but also not more than some constant limit. /// /// # Examples /// /// ``` /// use crossbeam_deque::{Injector, Steal, Worker}; /// /// let q = Injector::new(); /// q.push(1); /// q.push(2); /// q.push(3); /// q.push(4); /// /// let w = Worker::new_fifo(); /// assert_eq!(q.steal_batch_and_pop(&w), Steal::Success(1)); /// assert_eq!(w.pop(), Some(2)); /// ``` pub fn steal_batch_and_pop(&self, dest: &Worker) -> Steal { // TODO: we use `MAX_BATCH + 1` as the hard limit for Injecter as the performance is slightly // better, but we may change it in the future to be compatible with the same method in Stealer. self.steal_batch_with_limit_and_pop(dest, MAX_BATCH + 1) } /// Steals no more than `limit` of tasks, pushes them into a worker, and pops a task from that worker. /// /// How many tasks exactly will be stolen is not specified. That said, this method will try to /// steal around half of the tasks in the queue, but also not more than the given limit. /// /// # Examples /// /// ``` /// use crossbeam_deque::{Injector, Steal, Worker}; /// /// let q = Injector::new(); /// q.push(1); /// q.push(2); /// q.push(3); /// q.push(4); /// q.push(5); /// q.push(6); /// /// let w = Worker::new_fifo(); /// assert_eq!(q.steal_batch_with_limit_and_pop(&w, 2), Steal::Success(1)); /// assert_eq!(w.pop(), Some(2)); /// assert_eq!(w.pop(), None); /// /// q.push(7); /// // Setting a large limit does not guarantee that all elements will be popped. In this case, /// // half of the elements are currently popped, but the number of popped elements is considered /// // an implementation detail that may be changed in the future. /// assert_eq!(q.steal_batch_with_limit_and_pop(&w, std::usize::MAX), Steal::Success(3)); /// assert_eq!(w.pop(), Some(4)); /// assert_eq!(w.pop(), Some(5)); /// assert_eq!(w.pop(), None); /// ``` pub fn steal_batch_with_limit_and_pop(&self, dest: &Worker, limit: usize) -> Steal { assert!(limit > 0); let mut head; let mut block; let mut offset; let backoff = Backoff::new(); loop { head = self.head.index.load(Ordering::Acquire); block = self.head.block.load(Ordering::Acquire); // Calculate the offset of the index into the block. offset = (head >> SHIFT) % LAP; // If we reached the end of the block, wait until the next one is installed. if offset == BLOCK_CAP { backoff.snooze(); } else { break; } } let mut new_head = head; let advance; if new_head & HAS_NEXT == 0 { atomic::fence(Ordering::SeqCst); let tail = self.tail.index.load(Ordering::Relaxed); // If the tail equals the head, that means the queue is empty. if head >> SHIFT == tail >> SHIFT { return Steal::Empty; } // If head and tail are not in the same block, set `HAS_NEXT` in head. if (head >> SHIFT) / LAP != (tail >> SHIFT) / LAP { new_head |= HAS_NEXT; // We can steal all tasks till the end of the block. advance = (BLOCK_CAP - offset).min(limit); } else { let len = (tail - head) >> SHIFT; // Steal half of the available tasks. advance = ((len + 1) / 2).min(limit); } } else { // We can steal all tasks till the end of the block. advance = (BLOCK_CAP - offset).min(limit); } new_head += advance << SHIFT; let new_offset = offset + advance; // Try moving the head index forward. if self .head .index .compare_exchange_weak(head, new_head, Ordering::SeqCst, Ordering::Acquire) .is_err() { return Steal::Retry; } // Reserve capacity for the stolen batch. let batch_size = new_offset - offset - 1; dest.reserve(batch_size); // Get the destination buffer and back index. let dest_buffer = dest.buffer.get(); let dest_b = dest.inner.back.load(Ordering::Relaxed); unsafe { // If we've reached the end of the block, move to the next one. if new_offset == BLOCK_CAP { let next = (*block).wait_next(); let mut next_index = (new_head & !HAS_NEXT).wrapping_add(1 << SHIFT); if !(*next).next.load(Ordering::Relaxed).is_null() { next_index |= HAS_NEXT; } self.head.block.store(next, Ordering::Release); self.head.index.store(next_index, Ordering::Release); } // Read the task. let slot = (*block).slots.get_unchecked(offset); slot.wait_write(); let task = slot.task.get().read(); match dest.flavor { Flavor::Fifo => { // Copy values from the injector into the destination queue. for i in 0..batch_size { // Read the task. let slot = (*block).slots.get_unchecked(offset + i + 1); slot.wait_write(); let task = slot.task.get().read(); // Write it into the destination queue. dest_buffer.write(dest_b.wrapping_add(i as isize), task); } } Flavor::Lifo => { // Copy values from the injector into the destination queue. for i in 0..batch_size { // Read the task. let slot = (*block).slots.get_unchecked(offset + i + 1); slot.wait_write(); let task = slot.task.get().read(); // Write it into the destination queue. dest_buffer.write(dest_b.wrapping_add((batch_size - 1 - i) as isize), task); } } } atomic::fence(Ordering::Release); // Update the back index in the destination queue. // // This ordering could be `Relaxed`, but then thread sanitizer would falsely report // data races because it doesn't understand fences. dest.inner .back .store(dest_b.wrapping_add(batch_size as isize), Ordering::Release); // Destroy the block if we've reached the end, or if another thread wanted to destroy // but couldn't because we were busy reading from the slot. if new_offset == BLOCK_CAP { Block::destroy(block, offset); } else { for i in offset..new_offset { let slot = (*block).slots.get_unchecked(i); if slot.state.fetch_or(READ, Ordering::AcqRel) & DESTROY != 0 { Block::destroy(block, offset); break; } } } Steal::Success(task.assume_init()) } } /// Returns `true` if the queue is empty. /// /// # Examples /// /// ``` /// use crossbeam_deque::Injector; /// /// let q = Injector::new(); /// /// assert!(q.is_empty()); /// q.push(1); /// assert!(!q.is_empty()); /// ``` pub fn is_empty(&self) -> bool { let head = self.head.index.load(Ordering::SeqCst); let tail = self.tail.index.load(Ordering::SeqCst); head >> SHIFT == tail >> SHIFT } /// Returns the number of tasks in the queue. /// /// # Examples /// /// ``` /// use crossbeam_deque::Injector; /// /// let q = Injector::new(); /// /// assert_eq!(q.len(), 0); /// q.push(1); /// assert_eq!(q.len(), 1); /// q.push(1); /// assert_eq!(q.len(), 2); /// ``` pub fn len(&self) -> usize { loop { // Load the tail index, then load the head index. let mut tail = self.tail.index.load(Ordering::SeqCst); let mut head = self.head.index.load(Ordering::SeqCst); // If the tail index didn't change, we've got consistent indices to work with. if self.tail.index.load(Ordering::SeqCst) == tail { // Erase the lower bits. tail &= !((1 << SHIFT) - 1); head &= !((1 << SHIFT) - 1); // Fix up indices if they fall onto block ends. if (tail >> SHIFT) & (LAP - 1) == LAP - 1 { tail = tail.wrapping_add(1 << SHIFT); } if (head >> SHIFT) & (LAP - 1) == LAP - 1 { head = head.wrapping_add(1 << SHIFT); } // Rotate indices so that head falls into the first block. let lap = (head >> SHIFT) / LAP; tail = tail.wrapping_sub((lap * LAP) << SHIFT); head = head.wrapping_sub((lap * LAP) << SHIFT); // Remove the lower bits. tail >>= SHIFT; head >>= SHIFT; // Return the difference minus the number of blocks between tail and head. return tail - head - tail / LAP; } } } } impl Drop for Injector { fn drop(&mut self) { let mut head = *self.head.index.get_mut(); let mut tail = *self.tail.index.get_mut(); let mut block = *self.head.block.get_mut(); // Erase the lower bits. head &= !((1 << SHIFT) - 1); tail &= !((1 << SHIFT) - 1); unsafe { // Drop all values between `head` and `tail` and deallocate the heap-allocated blocks. while head != tail { let offset = (head >> SHIFT) % LAP; if offset < BLOCK_CAP { // Drop the task in the slot. let slot = (*block).slots.get_unchecked(offset); (*slot.task.get()).assume_init_drop(); } else { // Deallocate the block and move to the next one. let next = *(*block).next.get_mut(); drop(Box::from_raw(block)); block = next; } head = head.wrapping_add(1 << SHIFT); } // Deallocate the last remaining block. drop(Box::from_raw(block)); } } } impl fmt::Debug for Injector { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { f.pad("Worker { .. }") } } /// Possible outcomes of a steal operation. /// /// # Examples /// /// There are lots of ways to chain results of steal operations together: /// /// ``` /// use crossbeam_deque::Steal::{self, Empty, Retry, Success}; /// /// let collect = |v: Vec>| v.into_iter().collect::>(); /// /// assert_eq!(collect(vec![Empty, Empty, Empty]), Empty); /// assert_eq!(collect(vec![Empty, Retry, Empty]), Retry); /// assert_eq!(collect(vec![Retry, Success(1), Empty]), Success(1)); /// /// assert_eq!(collect(vec![Empty, Empty]).or_else(|| Retry), Retry); /// assert_eq!(collect(vec![Retry, Empty]).or_else(|| Success(1)), Success(1)); /// ``` #[must_use] #[derive(PartialEq, Eq, Copy, Clone)] pub enum Steal { /// The queue was empty at the time of stealing. Empty, /// At least one task was successfully stolen. Success(T), /// The steal operation needs to be retried. Retry, } impl Steal { /// Returns `true` if the queue was empty at the time of stealing. /// /// # Examples /// /// ``` /// use crossbeam_deque::Steal::{Empty, Retry, Success}; /// /// assert!(!Success(7).is_empty()); /// assert!(!Retry::.is_empty()); /// /// assert!(Empty::.is_empty()); /// ``` pub fn is_empty(&self) -> bool { match self { Steal::Empty => true, _ => false, } } /// Returns `true` if at least one task was stolen. /// /// # Examples /// /// ``` /// use crossbeam_deque::Steal::{Empty, Retry, Success}; /// /// assert!(!Empty::.is_success()); /// assert!(!Retry::.is_success()); /// /// assert!(Success(7).is_success()); /// ``` pub fn is_success(&self) -> bool { match self { Steal::Success(_) => true, _ => false, } } /// Returns `true` if the steal operation needs to be retried. /// /// # Examples /// /// ``` /// use crossbeam_deque::Steal::{Empty, Retry, Success}; /// /// assert!(!Empty::.is_retry()); /// assert!(!Success(7).is_retry()); /// /// assert!(Retry::.is_retry()); /// ``` pub fn is_retry(&self) -> bool { match self { Steal::Retry => true, _ => false, } } /// Returns the result of the operation, if successful. /// /// # Examples /// /// ``` /// use crossbeam_deque::Steal::{Empty, Retry, Success}; /// /// assert_eq!(Empty::.success(), None); /// assert_eq!(Retry::.success(), None); /// /// assert_eq!(Success(7).success(), Some(7)); /// ``` pub fn success(self) -> Option { match self { Steal::Success(res) => Some(res), _ => None, } } /// If no task was stolen, attempts another steal operation. /// /// Returns this steal result if it is `Success`. Otherwise, closure `f` is invoked and then: /// /// * If the second steal resulted in `Success`, it is returned. /// * If both steals were unsuccessful but any resulted in `Retry`, then `Retry` is returned. /// * If both resulted in `None`, then `None` is returned. /// /// # Examples /// /// ``` /// use crossbeam_deque::Steal::{Empty, Retry, Success}; /// /// assert_eq!(Success(1).or_else(|| Success(2)), Success(1)); /// assert_eq!(Retry.or_else(|| Success(2)), Success(2)); /// /// assert_eq!(Retry.or_else(|| Empty), Retry::); /// assert_eq!(Empty.or_else(|| Retry), Retry::); /// /// assert_eq!(Empty.or_else(|| Empty), Empty::); /// ``` pub fn or_else(self, f: F) -> Steal where F: FnOnce() -> Steal, { match self { Steal::Empty => f(), Steal::Success(_) => self, Steal::Retry => { if let Steal::Success(res) = f() { Steal::Success(res) } else { Steal::Retry } } } } } impl fmt::Debug for Steal { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { match self { Steal::Empty => f.pad("Empty"), Steal::Success(_) => f.pad("Success(..)"), Steal::Retry => f.pad("Retry"), } } } impl FromIterator> for Steal { /// Consumes items until a `Success` is found and returns it. /// /// If no `Success` was found, but there was at least one `Retry`, then returns `Retry`. /// Otherwise, `Empty` is returned. fn from_iter(iter: I) -> Steal where I: IntoIterator>, { let mut retry = false; for s in iter { match &s { Steal::Empty => {} Steal::Success(_) => return s, Steal::Retry => retry = true, } } if retry { Steal::Retry } else { Steal::Empty } } } crossbeam-deque-0.8.5/src/lib.rs000064400000000000000000000075611046102023000146310ustar 00000000000000//! Concurrent work-stealing deques. //! //! These data structures are most commonly used in work-stealing schedulers. The typical setup //! involves a number of threads, each having its own FIFO or LIFO queue (*worker*). There is also //! one global FIFO queue (*injector*) and a list of references to *worker* queues that are able to //! steal tasks (*stealers*). //! //! We spawn a new task onto the scheduler by pushing it into the *injector* queue. Each worker //! thread waits in a loop until it finds the next task to run and then runs it. To find a task, it //! first looks into its local *worker* queue, and then into the *injector* and *stealers*. //! //! # Queues //! //! [`Injector`] is a FIFO queue, where tasks are pushed and stolen from opposite ends. It is //! shared among threads and is usually the entry point for new tasks. //! //! [`Worker`] has two constructors: //! //! * [`new_fifo()`] - Creates a FIFO queue, in which tasks are pushed and popped from opposite //! ends. //! * [`new_lifo()`] - Creates a LIFO queue, in which tasks are pushed and popped from the same //! end. //! //! Each [`Worker`] is owned by a single thread and supports only push and pop operations. //! //! Method [`stealer()`] creates a [`Stealer`] that may be shared among threads and can only steal //! tasks from its [`Worker`]. Tasks are stolen from the end opposite to where they get pushed. //! //! # Stealing //! //! Steal operations come in three flavors: //! //! 1. [`steal()`] - Steals one task. //! 2. [`steal_batch()`] - Steals a batch of tasks and moves them into another worker. //! 3. [`steal_batch_and_pop()`] - Steals a batch of tasks, moves them into another queue, and pops //! one task from that worker. //! //! In contrast to push and pop operations, stealing can spuriously fail with [`Steal::Retry`], in //! which case the steal operation needs to be retried. //! //! # Examples //! //! Suppose a thread in a work-stealing scheduler is idle and looking for the next task to run. To //! find an available task, it might do the following: //! //! 1. Try popping one task from the local worker queue. //! 2. Try stealing a batch of tasks from the global injector queue. //! 3. Try stealing one task from another thread using the stealer list. //! //! An implementation of this work-stealing strategy: //! //! ``` //! use crossbeam_deque::{Injector, Stealer, Worker}; //! use std::iter; //! //! fn find_task( //! local: &Worker, //! global: &Injector, //! stealers: &[Stealer], //! ) -> Option { //! // Pop a task from the local queue, if not empty. //! local.pop().or_else(|| { //! // Otherwise, we need to look for a task elsewhere. //! iter::repeat_with(|| { //! // Try stealing a batch of tasks from the global queue. //! global.steal_batch_and_pop(local) //! // Or try stealing a task from one of the other threads. //! .or_else(|| stealers.iter().map(|s| s.steal()).collect()) //! }) //! // Loop while no task was stolen and any steal operation needs to be retried. //! .find(|s| !s.is_retry()) //! // Extract the stolen task, if there is one. //! .and_then(|s| s.success()) //! }) //! } //! ``` //! //! [`new_fifo()`]: Worker::new_fifo //! [`new_lifo()`]: Worker::new_lifo //! [`stealer()`]: Worker::stealer //! [`steal()`]: Stealer::steal //! [`steal_batch()`]: Stealer::steal_batch //! [`steal_batch_and_pop()`]: Stealer::steal_batch_and_pop #![doc(test( no_crate_inject, attr( deny(warnings, rust_2018_idioms), allow(dead_code, unused_assignments, unused_variables) ) ))] #![warn( missing_docs, missing_debug_implementations, rust_2018_idioms, unreachable_pub )] #![cfg_attr(not(feature = "std"), no_std)] #[cfg(feature = "std")] mod deque; #[cfg(feature = "std")] pub use crate::deque::{Injector, Steal, Stealer, Worker}; crossbeam-deque-0.8.5/tests/fifo.rs000064400000000000000000000207521046102023000153560ustar 00000000000000use std::sync::atomic::Ordering::SeqCst; use std::sync::atomic::{AtomicBool, AtomicUsize}; use std::sync::{Arc, Mutex}; use crossbeam_deque::Steal::{Empty, Success}; use crossbeam_deque::Worker; use crossbeam_utils::thread::scope; use rand::Rng; #[test] fn smoke() { let w = Worker::new_fifo(); let s = w.stealer(); assert_eq!(w.pop(), None); assert_eq!(s.steal(), Empty); w.push(1); assert_eq!(w.pop(), Some(1)); assert_eq!(w.pop(), None); assert_eq!(s.steal(), Empty); w.push(2); assert_eq!(s.steal(), Success(2)); assert_eq!(s.steal(), Empty); assert_eq!(w.pop(), None); w.push(3); w.push(4); w.push(5); assert_eq!(s.steal(), Success(3)); assert_eq!(s.steal(), Success(4)); assert_eq!(s.steal(), Success(5)); assert_eq!(s.steal(), Empty); w.push(6); w.push(7); w.push(8); w.push(9); assert_eq!(w.pop(), Some(6)); assert_eq!(s.steal(), Success(7)); assert_eq!(w.pop(), Some(8)); assert_eq!(w.pop(), Some(9)); assert_eq!(w.pop(), None); } #[test] fn is_empty() { let w = Worker::new_fifo(); let s = w.stealer(); assert!(w.is_empty()); w.push(1); assert!(!w.is_empty()); w.push(2); assert!(!w.is_empty()); let _ = w.pop(); assert!(!w.is_empty()); let _ = w.pop(); assert!(w.is_empty()); assert!(s.is_empty()); w.push(1); assert!(!s.is_empty()); w.push(2); assert!(!s.is_empty()); let _ = s.steal(); assert!(!s.is_empty()); let _ = s.steal(); assert!(s.is_empty()); } #[test] fn spsc() { #[cfg(miri)] const STEPS: usize = 500; #[cfg(not(miri))] const STEPS: usize = 50_000; let w = Worker::new_fifo(); let s = w.stealer(); scope(|scope| { scope.spawn(|_| { for i in 0..STEPS { loop { if let Success(v) = s.steal() { assert_eq!(i, v); break; } } } assert_eq!(s.steal(), Empty); }); for i in 0..STEPS { w.push(i); } }) .unwrap(); } #[test] fn stampede() { const THREADS: usize = 8; #[cfg(miri)] const COUNT: usize = 500; #[cfg(not(miri))] const COUNT: usize = 50_000; let w = Worker::new_fifo(); for i in 0..COUNT { w.push(Box::new(i + 1)); } let remaining = Arc::new(AtomicUsize::new(COUNT)); scope(|scope| { for _ in 0..THREADS { let s = w.stealer(); let remaining = remaining.clone(); scope.spawn(move |_| { let mut last = 0; while remaining.load(SeqCst) > 0 { if let Success(x) = s.steal() { assert!(last < *x); last = *x; remaining.fetch_sub(1, SeqCst); } } }); } let mut last = 0; while remaining.load(SeqCst) > 0 { if let Some(x) = w.pop() { assert!(last < *x); last = *x; remaining.fetch_sub(1, SeqCst); } } }) .unwrap(); } #[test] fn stress() { const THREADS: usize = 8; #[cfg(miri)] const COUNT: usize = 500; #[cfg(not(miri))] const COUNT: usize = 50_000; let w = Worker::new_fifo(); let done = Arc::new(AtomicBool::new(false)); let hits = Arc::new(AtomicUsize::new(0)); scope(|scope| { for _ in 0..THREADS { let s = w.stealer(); let done = done.clone(); let hits = hits.clone(); scope.spawn(move |_| { let w2 = Worker::new_fifo(); while !done.load(SeqCst) { if let Success(_) = s.steal() { hits.fetch_add(1, SeqCst); } let _ = s.steal_batch(&w2); if let Success(_) = s.steal_batch_and_pop(&w2) { hits.fetch_add(1, SeqCst); } while w2.pop().is_some() { hits.fetch_add(1, SeqCst); } } }); } let mut rng = rand::thread_rng(); let mut expected = 0; while expected < COUNT { if rng.gen_range(0..3) == 0 { while w.pop().is_some() { hits.fetch_add(1, SeqCst); } } else { w.push(expected); expected += 1; } } while hits.load(SeqCst) < COUNT { while w.pop().is_some() { hits.fetch_add(1, SeqCst); } } done.store(true, SeqCst); }) .unwrap(); } #[cfg_attr(miri, ignore)] // Miri is too slow #[test] fn no_starvation() { const THREADS: usize = 8; const COUNT: usize = 50_000; let w = Worker::new_fifo(); let done = Arc::new(AtomicBool::new(false)); let mut all_hits = Vec::new(); scope(|scope| { for _ in 0..THREADS { let s = w.stealer(); let done = done.clone(); let hits = Arc::new(AtomicUsize::new(0)); all_hits.push(hits.clone()); scope.spawn(move |_| { let w2 = Worker::new_fifo(); while !done.load(SeqCst) { if let Success(_) = s.steal() { hits.fetch_add(1, SeqCst); } let _ = s.steal_batch(&w2); if let Success(_) = s.steal_batch_and_pop(&w2) { hits.fetch_add(1, SeqCst); } while w2.pop().is_some() { hits.fetch_add(1, SeqCst); } } }); } let mut rng = rand::thread_rng(); let mut my_hits = 0; loop { for i in 0..rng.gen_range(0..COUNT) { if rng.gen_range(0..3) == 0 && my_hits == 0 { while w.pop().is_some() { my_hits += 1; } } else { w.push(i); } } if my_hits > 0 && all_hits.iter().all(|h| h.load(SeqCst) > 0) { break; } } done.store(true, SeqCst); }) .unwrap(); } #[test] fn destructors() { #[cfg(miri)] const THREADS: usize = 2; #[cfg(not(miri))] const THREADS: usize = 8; #[cfg(miri)] const COUNT: usize = 500; #[cfg(not(miri))] const COUNT: usize = 50_000; #[cfg(miri)] const STEPS: usize = 100; #[cfg(not(miri))] const STEPS: usize = 1000; struct Elem(usize, Arc>>); impl Drop for Elem { fn drop(&mut self) { self.1.lock().unwrap().push(self.0); } } let w = Worker::new_fifo(); let dropped = Arc::new(Mutex::new(Vec::new())); let remaining = Arc::new(AtomicUsize::new(COUNT)); for i in 0..COUNT { w.push(Elem(i, dropped.clone())); } scope(|scope| { for _ in 0..THREADS { let remaining = remaining.clone(); let s = w.stealer(); scope.spawn(move |_| { let w2 = Worker::new_fifo(); let mut cnt = 0; while cnt < STEPS { if let Success(_) = s.steal() { cnt += 1; remaining.fetch_sub(1, SeqCst); } let _ = s.steal_batch(&w2); if let Success(_) = s.steal_batch_and_pop(&w2) { cnt += 1; remaining.fetch_sub(1, SeqCst); } while w2.pop().is_some() { cnt += 1; remaining.fetch_sub(1, SeqCst); } } }); } for _ in 0..STEPS { if w.pop().is_some() { remaining.fetch_sub(1, SeqCst); } } }) .unwrap(); let rem = remaining.load(SeqCst); assert!(rem > 0); { let mut v = dropped.lock().unwrap(); assert_eq!(v.len(), COUNT - rem); v.clear(); } drop(w); { let mut v = dropped.lock().unwrap(); assert_eq!(v.len(), rem); v.sort_unstable(); for pair in v.windows(2) { assert_eq!(pair[0] + 1, pair[1]); } } } crossbeam-deque-0.8.5/tests/injector.rs000064400000000000000000000216011046102023000162420ustar 00000000000000use std::sync::atomic::Ordering::SeqCst; use std::sync::atomic::{AtomicBool, AtomicUsize}; use std::sync::{Arc, Mutex}; use crossbeam_deque::Steal::{Empty, Success}; use crossbeam_deque::{Injector, Worker}; use crossbeam_utils::thread::scope; use rand::Rng; #[test] fn smoke() { let q = Injector::new(); assert_eq!(q.steal(), Empty); q.push(1); q.push(2); assert_eq!(q.steal(), Success(1)); assert_eq!(q.steal(), Success(2)); assert_eq!(q.steal(), Empty); q.push(3); assert_eq!(q.steal(), Success(3)); assert_eq!(q.steal(), Empty); } #[test] fn is_empty() { let q = Injector::new(); assert!(q.is_empty()); q.push(1); assert!(!q.is_empty()); q.push(2); assert!(!q.is_empty()); let _ = q.steal(); assert!(!q.is_empty()); let _ = q.steal(); assert!(q.is_empty()); q.push(3); assert!(!q.is_empty()); let _ = q.steal(); assert!(q.is_empty()); } #[test] fn spsc() { #[cfg(miri)] const COUNT: usize = 500; #[cfg(not(miri))] const COUNT: usize = 100_000; let q = Injector::new(); scope(|scope| { scope.spawn(|_| { for i in 0..COUNT { loop { if let Success(v) = q.steal() { assert_eq!(i, v); break; } #[cfg(miri)] std::hint::spin_loop(); } } assert_eq!(q.steal(), Empty); }); for i in 0..COUNT { q.push(i); } }) .unwrap(); } #[test] fn mpmc() { #[cfg(miri)] const COUNT: usize = 500; #[cfg(not(miri))] const COUNT: usize = 25_000; const THREADS: usize = 4; let q = Injector::new(); let v = (0..COUNT).map(|_| AtomicUsize::new(0)).collect::>(); scope(|scope| { for _ in 0..THREADS { scope.spawn(|_| { for i in 0..COUNT { q.push(i); } }); } for _ in 0..THREADS { scope.spawn(|_| { for _ in 0..COUNT { loop { if let Success(n) = q.steal() { v[n].fetch_add(1, SeqCst); break; } #[cfg(miri)] std::hint::spin_loop(); } } }); } }) .unwrap(); for c in v { assert_eq!(c.load(SeqCst), THREADS); } } #[test] fn stampede() { const THREADS: usize = 8; #[cfg(miri)] const COUNT: usize = 500; #[cfg(not(miri))] const COUNT: usize = 50_000; let q = Injector::new(); for i in 0..COUNT { q.push(Box::new(i + 1)); } let remaining = Arc::new(AtomicUsize::new(COUNT)); scope(|scope| { for _ in 0..THREADS { let remaining = remaining.clone(); let q = &q; scope.spawn(move |_| { let mut last = 0; while remaining.load(SeqCst) > 0 { if let Success(x) = q.steal() { assert!(last < *x); last = *x; remaining.fetch_sub(1, SeqCst); } } }); } let mut last = 0; while remaining.load(SeqCst) > 0 { if let Success(x) = q.steal() { assert!(last < *x); last = *x; remaining.fetch_sub(1, SeqCst); } } }) .unwrap(); } #[test] fn stress() { const THREADS: usize = 8; #[cfg(miri)] const COUNT: usize = 500; #[cfg(not(miri))] const COUNT: usize = 50_000; let q = Injector::new(); let done = Arc::new(AtomicBool::new(false)); let hits = Arc::new(AtomicUsize::new(0)); scope(|scope| { for _ in 0..THREADS { let done = done.clone(); let hits = hits.clone(); let q = &q; scope.spawn(move |_| { let w2 = Worker::new_fifo(); while !done.load(SeqCst) { if let Success(_) = q.steal() { hits.fetch_add(1, SeqCst); } let _ = q.steal_batch(&w2); if let Success(_) = q.steal_batch_and_pop(&w2) { hits.fetch_add(1, SeqCst); } while w2.pop().is_some() { hits.fetch_add(1, SeqCst); } } }); } let mut rng = rand::thread_rng(); let mut expected = 0; while expected < COUNT { if rng.gen_range(0..3) == 0 { while let Success(_) = q.steal() { hits.fetch_add(1, SeqCst); } } else { q.push(expected); expected += 1; } } while hits.load(SeqCst) < COUNT { while let Success(_) = q.steal() { hits.fetch_add(1, SeqCst); } } done.store(true, SeqCst); }) .unwrap(); } #[cfg_attr(miri, ignore)] // Miri is too slow #[test] fn no_starvation() { const THREADS: usize = 8; const COUNT: usize = 50_000; let q = Injector::new(); let done = Arc::new(AtomicBool::new(false)); let mut all_hits = Vec::new(); scope(|scope| { for _ in 0..THREADS { let done = done.clone(); let hits = Arc::new(AtomicUsize::new(0)); all_hits.push(hits.clone()); let q = &q; scope.spawn(move |_| { let w2 = Worker::new_fifo(); while !done.load(SeqCst) { if let Success(_) = q.steal() { hits.fetch_add(1, SeqCst); } let _ = q.steal_batch(&w2); if let Success(_) = q.steal_batch_and_pop(&w2) { hits.fetch_add(1, SeqCst); } while w2.pop().is_some() { hits.fetch_add(1, SeqCst); } } }); } let mut rng = rand::thread_rng(); let mut my_hits = 0; loop { for i in 0..rng.gen_range(0..COUNT) { if rng.gen_range(0..3) == 0 && my_hits == 0 { while let Success(_) = q.steal() { my_hits += 1; } } else { q.push(i); } } if my_hits > 0 && all_hits.iter().all(|h| h.load(SeqCst) > 0) { break; } } done.store(true, SeqCst); }) .unwrap(); } #[test] fn destructors() { #[cfg(miri)] const THREADS: usize = 2; #[cfg(not(miri))] const THREADS: usize = 8; #[cfg(miri)] const COUNT: usize = 500; #[cfg(not(miri))] const COUNT: usize = 50_000; #[cfg(miri)] const STEPS: usize = 100; #[cfg(not(miri))] const STEPS: usize = 1000; struct Elem(usize, Arc>>); impl Drop for Elem { fn drop(&mut self) { self.1.lock().unwrap().push(self.0); } } let q = Injector::new(); let dropped = Arc::new(Mutex::new(Vec::new())); let remaining = Arc::new(AtomicUsize::new(COUNT)); for i in 0..COUNT { q.push(Elem(i, dropped.clone())); } scope(|scope| { for _ in 0..THREADS { let remaining = remaining.clone(); let q = &q; scope.spawn(move |_| { let w2 = Worker::new_fifo(); let mut cnt = 0; while cnt < STEPS { if let Success(_) = q.steal() { cnt += 1; remaining.fetch_sub(1, SeqCst); } let _ = q.steal_batch(&w2); if let Success(_) = q.steal_batch_and_pop(&w2) { cnt += 1; remaining.fetch_sub(1, SeqCst); } while w2.pop().is_some() { cnt += 1; remaining.fetch_sub(1, SeqCst); } } }); } for _ in 0..STEPS { if let Success(_) = q.steal() { remaining.fetch_sub(1, SeqCst); } } }) .unwrap(); let rem = remaining.load(SeqCst); assert!(rem > 0); { let mut v = dropped.lock().unwrap(); assert_eq!(v.len(), COUNT - rem); v.clear(); } drop(q); { let mut v = dropped.lock().unwrap(); assert_eq!(v.len(), rem); v.sort_unstable(); for pair in v.windows(2) { assert_eq!(pair[0] + 1, pair[1]); } } } crossbeam-deque-0.8.5/tests/lifo.rs000064400000000000000000000210771046102023000153650ustar 00000000000000use std::sync::atomic::Ordering::SeqCst; use std::sync::atomic::{AtomicBool, AtomicUsize}; use std::sync::{Arc, Mutex}; use crossbeam_deque::Steal::{Empty, Success}; use crossbeam_deque::Worker; use crossbeam_utils::thread::scope; use rand::Rng; #[test] fn smoke() { let w = Worker::new_lifo(); let s = w.stealer(); assert_eq!(w.pop(), None); assert_eq!(s.steal(), Empty); w.push(1); assert_eq!(w.pop(), Some(1)); assert_eq!(w.pop(), None); assert_eq!(s.steal(), Empty); w.push(2); assert_eq!(s.steal(), Success(2)); assert_eq!(s.steal(), Empty); assert_eq!(w.pop(), None); w.push(3); w.push(4); w.push(5); assert_eq!(s.steal(), Success(3)); assert_eq!(s.steal(), Success(4)); assert_eq!(s.steal(), Success(5)); assert_eq!(s.steal(), Empty); w.push(6); w.push(7); w.push(8); w.push(9); assert_eq!(w.pop(), Some(9)); assert_eq!(s.steal(), Success(6)); assert_eq!(w.pop(), Some(8)); assert_eq!(w.pop(), Some(7)); assert_eq!(w.pop(), None); } #[test] fn is_empty() { let w = Worker::new_lifo(); let s = w.stealer(); assert!(w.is_empty()); w.push(1); assert!(!w.is_empty()); w.push(2); assert!(!w.is_empty()); let _ = w.pop(); assert!(!w.is_empty()); let _ = w.pop(); assert!(w.is_empty()); assert!(s.is_empty()); w.push(1); assert!(!s.is_empty()); w.push(2); assert!(!s.is_empty()); let _ = s.steal(); assert!(!s.is_empty()); let _ = s.steal(); assert!(s.is_empty()); } #[test] fn spsc() { #[cfg(miri)] const STEPS: usize = 500; #[cfg(not(miri))] const STEPS: usize = 50_000; let w = Worker::new_lifo(); let s = w.stealer(); scope(|scope| { scope.spawn(|_| { for i in 0..STEPS { loop { if let Success(v) = s.steal() { assert_eq!(i, v); break; } #[cfg(miri)] std::hint::spin_loop(); } } assert_eq!(s.steal(), Empty); }); for i in 0..STEPS { w.push(i); } }) .unwrap(); } #[test] fn stampede() { const THREADS: usize = 8; #[cfg(miri)] const COUNT: usize = 500; #[cfg(not(miri))] const COUNT: usize = 50_000; let w = Worker::new_lifo(); for i in 0..COUNT { w.push(Box::new(i + 1)); } let remaining = Arc::new(AtomicUsize::new(COUNT)); scope(|scope| { for _ in 0..THREADS { let s = w.stealer(); let remaining = remaining.clone(); scope.spawn(move |_| { let mut last = 0; while remaining.load(SeqCst) > 0 { if let Success(x) = s.steal() { assert!(last < *x); last = *x; remaining.fetch_sub(1, SeqCst); } } }); } let mut last = COUNT + 1; while remaining.load(SeqCst) > 0 { if let Some(x) = w.pop() { assert!(last > *x); last = *x; remaining.fetch_sub(1, SeqCst); } } }) .unwrap(); } #[test] fn stress() { const THREADS: usize = 8; #[cfg(miri)] const COUNT: usize = 500; #[cfg(not(miri))] const COUNT: usize = 50_000; let w = Worker::new_lifo(); let done = Arc::new(AtomicBool::new(false)); let hits = Arc::new(AtomicUsize::new(0)); scope(|scope| { for _ in 0..THREADS { let s = w.stealer(); let done = done.clone(); let hits = hits.clone(); scope.spawn(move |_| { let w2 = Worker::new_lifo(); while !done.load(SeqCst) { if let Success(_) = s.steal() { hits.fetch_add(1, SeqCst); } let _ = s.steal_batch(&w2); if let Success(_) = s.steal_batch_and_pop(&w2) { hits.fetch_add(1, SeqCst); } while w2.pop().is_some() { hits.fetch_add(1, SeqCst); } } }); } let mut rng = rand::thread_rng(); let mut expected = 0; while expected < COUNT { if rng.gen_range(0..3) == 0 { while w.pop().is_some() { hits.fetch_add(1, SeqCst); } } else { w.push(expected); expected += 1; } } while hits.load(SeqCst) < COUNT { while w.pop().is_some() { hits.fetch_add(1, SeqCst); } } done.store(true, SeqCst); }) .unwrap(); } #[cfg_attr(miri, ignore)] // Miri is too slow #[test] fn no_starvation() { const THREADS: usize = 8; const COUNT: usize = 50_000; let w = Worker::new_lifo(); let done = Arc::new(AtomicBool::new(false)); let mut all_hits = Vec::new(); scope(|scope| { for _ in 0..THREADS { let s = w.stealer(); let done = done.clone(); let hits = Arc::new(AtomicUsize::new(0)); all_hits.push(hits.clone()); scope.spawn(move |_| { let w2 = Worker::new_lifo(); while !done.load(SeqCst) { if let Success(_) = s.steal() { hits.fetch_add(1, SeqCst); } let _ = s.steal_batch(&w2); if let Success(_) = s.steal_batch_and_pop(&w2) { hits.fetch_add(1, SeqCst); } while w2.pop().is_some() { hits.fetch_add(1, SeqCst); } } }); } let mut rng = rand::thread_rng(); let mut my_hits = 0; loop { for i in 0..rng.gen_range(0..COUNT) { if rng.gen_range(0..3) == 0 && my_hits == 0 { while w.pop().is_some() { my_hits += 1; } } else { w.push(i); } } if my_hits > 0 && all_hits.iter().all(|h| h.load(SeqCst) > 0) { break; } } done.store(true, SeqCst); }) .unwrap(); } #[test] fn destructors() { #[cfg(miri)] const THREADS: usize = 2; #[cfg(not(miri))] const THREADS: usize = 8; #[cfg(miri)] const COUNT: usize = 500; #[cfg(not(miri))] const COUNT: usize = 50_000; #[cfg(miri)] const STEPS: usize = 100; #[cfg(not(miri))] const STEPS: usize = 1000; struct Elem(usize, Arc>>); impl Drop for Elem { fn drop(&mut self) { self.1.lock().unwrap().push(self.0); } } let w = Worker::new_lifo(); let dropped = Arc::new(Mutex::new(Vec::new())); let remaining = Arc::new(AtomicUsize::new(COUNT)); for i in 0..COUNT { w.push(Elem(i, dropped.clone())); } scope(|scope| { for _ in 0..THREADS { let remaining = remaining.clone(); let s = w.stealer(); scope.spawn(move |_| { let w2 = Worker::new_lifo(); let mut cnt = 0; while cnt < STEPS { if let Success(_) = s.steal() { cnt += 1; remaining.fetch_sub(1, SeqCst); } let _ = s.steal_batch(&w2); if let Success(_) = s.steal_batch_and_pop(&w2) { cnt += 1; remaining.fetch_sub(1, SeqCst); } while w2.pop().is_some() { cnt += 1; remaining.fetch_sub(1, SeqCst); } } }); } for _ in 0..STEPS { if w.pop().is_some() { remaining.fetch_sub(1, SeqCst); } } }) .unwrap(); let rem = remaining.load(SeqCst); assert!(rem > 0); { let mut v = dropped.lock().unwrap(); assert_eq!(v.len(), COUNT - rem); v.clear(); } drop(w); { let mut v = dropped.lock().unwrap(); assert_eq!(v.len(), rem); v.sort_unstable(); for pair in v.windows(2) { assert_eq!(pair[0] + 1, pair[1]); } } } crossbeam-deque-0.8.5/tests/steal.rs000064400000000000000000000104061046102023000155360ustar 00000000000000use crossbeam_deque::Steal::Success; use crossbeam_deque::{Injector, Worker}; #[test] fn steal_fifo() { let w = Worker::new_fifo(); for i in 1..=3 { w.push(i); } let s = w.stealer(); assert_eq!(s.steal(), Success(1)); assert_eq!(s.steal(), Success(2)); assert_eq!(s.steal(), Success(3)); } #[test] fn steal_lifo() { let w = Worker::new_lifo(); for i in 1..=3 { w.push(i); } let s = w.stealer(); assert_eq!(s.steal(), Success(1)); assert_eq!(s.steal(), Success(2)); assert_eq!(s.steal(), Success(3)); } #[test] fn steal_injector() { let q = Injector::new(); for i in 1..=3 { q.push(i); } assert_eq!(q.steal(), Success(1)); assert_eq!(q.steal(), Success(2)); assert_eq!(q.steal(), Success(3)); } #[test] fn steal_batch_fifo_fifo() { let w = Worker::new_fifo(); for i in 1..=4 { w.push(i); } let s = w.stealer(); let w2 = Worker::new_fifo(); assert_eq!(s.steal_batch(&w2), Success(())); assert_eq!(w2.pop(), Some(1)); assert_eq!(w2.pop(), Some(2)); } #[test] fn steal_batch_lifo_lifo() { let w = Worker::new_lifo(); for i in 1..=4 { w.push(i); } let s = w.stealer(); let w2 = Worker::new_lifo(); assert_eq!(s.steal_batch(&w2), Success(())); assert_eq!(w2.pop(), Some(2)); assert_eq!(w2.pop(), Some(1)); } #[test] fn steal_batch_fifo_lifo() { let w = Worker::new_fifo(); for i in 1..=4 { w.push(i); } let s = w.stealer(); let w2 = Worker::new_lifo(); assert_eq!(s.steal_batch(&w2), Success(())); assert_eq!(w2.pop(), Some(1)); assert_eq!(w2.pop(), Some(2)); } #[test] fn steal_batch_lifo_fifo() { let w = Worker::new_lifo(); for i in 1..=4 { w.push(i); } let s = w.stealer(); let w2 = Worker::new_fifo(); assert_eq!(s.steal_batch(&w2), Success(())); assert_eq!(w2.pop(), Some(2)); assert_eq!(w2.pop(), Some(1)); } #[test] fn steal_batch_injector_fifo() { let q = Injector::new(); for i in 1..=4 { q.push(i); } let w2 = Worker::new_fifo(); assert_eq!(q.steal_batch(&w2), Success(())); assert_eq!(w2.pop(), Some(1)); assert_eq!(w2.pop(), Some(2)); } #[test] fn steal_batch_injector_lifo() { let q = Injector::new(); for i in 1..=4 { q.push(i); } let w2 = Worker::new_lifo(); assert_eq!(q.steal_batch(&w2), Success(())); assert_eq!(w2.pop(), Some(1)); assert_eq!(w2.pop(), Some(2)); } #[test] fn steal_batch_and_pop_fifo_fifo() { let w = Worker::new_fifo(); for i in 1..=6 { w.push(i); } let s = w.stealer(); let w2 = Worker::new_fifo(); assert_eq!(s.steal_batch_and_pop(&w2), Success(1)); assert_eq!(w2.pop(), Some(2)); assert_eq!(w2.pop(), Some(3)); } #[test] fn steal_batch_and_pop_lifo_lifo() { let w = Worker::new_lifo(); for i in 1..=6 { w.push(i); } let s = w.stealer(); let w2 = Worker::new_lifo(); assert_eq!(s.steal_batch_and_pop(&w2), Success(3)); assert_eq!(w2.pop(), Some(2)); assert_eq!(w2.pop(), Some(1)); } #[test] fn steal_batch_and_pop_fifo_lifo() { let w = Worker::new_fifo(); for i in 1..=6 { w.push(i); } let s = w.stealer(); let w2 = Worker::new_lifo(); assert_eq!(s.steal_batch_and_pop(&w2), Success(1)); assert_eq!(w2.pop(), Some(2)); assert_eq!(w2.pop(), Some(3)); } #[test] fn steal_batch_and_pop_lifo_fifo() { let w = Worker::new_lifo(); for i in 1..=6 { w.push(i); } let s = w.stealer(); let w2 = Worker::new_fifo(); assert_eq!(s.steal_batch_and_pop(&w2), Success(3)); assert_eq!(w2.pop(), Some(2)); assert_eq!(w2.pop(), Some(1)); } #[test] fn steal_batch_and_pop_injector_fifo() { let q = Injector::new(); for i in 1..=6 { q.push(i); } let w2 = Worker::new_fifo(); assert_eq!(q.steal_batch_and_pop(&w2), Success(1)); assert_eq!(w2.pop(), Some(2)); assert_eq!(w2.pop(), Some(3)); } #[test] fn steal_batch_and_pop_injector_lifo() { let q = Injector::new(); for i in 1..=6 { q.push(i); } let w2 = Worker::new_lifo(); assert_eq!(q.steal_batch_and_pop(&w2), Success(1)); assert_eq!(w2.pop(), Some(2)); assert_eq!(w2.pop(), Some(3)); }