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: 190 ns/iter (+/- 24)
test tests::std_2 ... bench: 2,054 ns/iter (+/- 822)
test tests::ours_4 ... bench: 236 ns/iter (+/- 2)
test tests::std_4 ... bench: 11,913 ns/iter (+/- 60)
Dell server with 2x 10-core (20HT) Intel Xeon E5-2660 v3 @ 2.60GHz across two NUMA nodes:
text
test tests::ours_4 ... bench: 689 ns/iter (+/- 9)
test tests::std_4 ... bench: 4,762 ns/iter (+/- 151)
test tests::ours_8 ... bench: 1,380 ns/iter (+/- 13)
test tests::std_8 ... bench: 17,545 ns/iter (+/- 288)
test tests::ours_16 ... bench: 2,970 ns/iter (+/- 33)
test tests::std_16 ... bench: 38,215 ns/iter (+/- 469)
test tests::ours_32 ... bench: 3,838 ns/iter (+/- 129)
test tests::std_32 ... bench: 94,266 ns/iter (+/- 12,243)
Or, in plot form:
