A thread barrier like [std::sync::Barrier] with a more scalable implementation than the one
provided by the standard library (which uses a Mutex). A barrier enables multiple threads to
synchronize the beginning of some computation.
```rust use hurdles::Barrier; use std::thread;
let mut handles = Vec::with_capacity(10); let mut barrier = Barrier::new(10); for _ in 0..10 { let mut c = barrier.clone(); // The same messages will be printed together. // You will NOT see any interleaving. handles.push(thread::spawn(move|| { println!("before wait"); c.wait(); println!("after wait"); })); } // Wait for other threads to finish. for handle in handles { handle.join().unwrap(); } ```
This crate currently implements a counter-based linear barrier as described in "3.1 Centralized Barriers" in Mellor-Crummey and Scott’s paper Algorithms for scalable synchronization on shared-memory multiprocessors from 1991. For a higher-level explanation, see Lars-Dominik Braun's Introduction to barrier algorithms.
Modern laptop with 2-core (4HT) Intel Core i7-5600U @ 2.60GHz:
text
test tests::ours_2 ... bench: 135 ns/iter (+/- 1)
test tests::std_2 ... bench: 276 ns/iter (+/- 181)
test tests::ours_4 ... bench: 235 ns/iter (+/- 14)
test tests::std_4 ... bench: 11,882 ns/iter (+/- 111)
Dell server with 2x 10-core (20HT) Intel Xeon E5-2660 v3 @ 2.60GHz across two NUMA nodes:
text
test tests::ours_4 ... bench: 568 ns/iter (+/- 4)
test tests::std_4 ... bench: 4,568 ns/iter (+/- 88)
test tests::ours_8 ... bench: 1,454 ns/iter (+/- 14)
test tests::std_8 ... bench: 17,668 ns/iter (+/- 322)
test tests::ours_16 ... bench: 2,856 ns/iter (+/- 32)
test tests::std_16 ... bench: 38,254 ns/iter (+/- 597)
test tests::ours_32 ... bench: 3,848 ns/iter (+/- 36)
test tests::std_32 ... bench: 86,194 ns/iter (+/- 15,506)