hashbrown

Build Status Crates.io Documentation

This crate is a Rust port of Google's high-performance [SwissTable] hash map, adapted to make it a drop-in replacement for Rust's standard HashMap and HashSet types.

The original C++ version of SwissTable can be found [here], and this [CppCon talk] gives an overview of how the algorithm works.

Since Rust 1.36, this is now the HashMap implementation for the Rust standard library. All benchmarks and features below are compared to the previous hash table implementation in the Rust standard library.

Change log

Features

Performance

Compared to the previous implementation of std::collections::HashMap (Rust 1.35).

With the hashbrown default AHash hasher:

text name oldstdhash ns/iter hashbrown ns/iter diff ns/iter diff % speedup insert_ahash_highbits 20,846 7,397 -13,449 -64.52% x 2.82 insert_ahash_random 20,515 7,796 -12,719 -62.00% x 2.63 insert_ahash_serial 21,668 7,264 -14,404 -66.48% x 2.98 insert_erase_ahash_highbits 29,570 17,498 -12,072 -40.83% x 1.69 insert_erase_ahash_random 39,569 17,474 -22,095 -55.84% x 2.26 insert_erase_ahash_serial 32,073 17,332 -14,741 -45.96% x 1.85 iter_ahash_highbits 1,572 2,087 515 32.76% x 0.75 iter_ahash_random 1,609 2,074 465 28.90% x 0.78 iter_ahash_serial 2,293 2,120 -173 -7.54% x 1.08 lookup_ahash_highbits 3,460 4,403 943 27.25% x 0.79 lookup_ahash_random 6,377 3,911 -2,466 -38.67% x 1.63 lookup_ahash_serial 3,629 3,586 -43 -1.18% x 1.01 lookup_fail_ahash_highbits 5,286 3,411 -1,875 -35.47% x 1.55 lookup_fail_ahash_random 12,365 4,171 -8,194 -66.27% x 2.96 lookup_fail_ahash_serial 4,902 3,240 -1,662 -33.90% x 1.51

With the libstd default SipHash hasher:

text name oldstdhash ns/iter hashbrown ns/iter diff ns/iter diff % speedup insert_std_highbits 32,598 20,199 -12,399 -38.04% x 1.61 insert_std_random 29,824 20,760 -9,064 -30.39% x 1.44 insert_std_serial 33,151 17,256 -15,895 -47.95% x 1.92 insert_erase_std_highbits 74,731 48,735 -25,996 -34.79% x 1.53 insert_erase_std_random 73,828 47,649 -26,179 -35.46% x 1.55 insert_erase_std_serial 73,864 40,147 -33,717 -45.65% x 1.84 iter_std_highbits 1,518 2,264 746 49.14% x 0.67 iter_std_random 1,502 2,414 912 60.72% x 0.62 iter_std_serial 6,361 2,118 -4,243 -66.70% x 3.00 lookup_std_highbits 21,705 16,962 -4,743 -21.85% x 1.28 lookup_std_random 21,654 17,158 -4,496 -20.76% x 1.26 lookup_std_serial 18,726 14,509 -4,217 -22.52% x 1.29 lookup_fail_std_highbits 25,852 17,323 -8,529 -32.99% x 1.49 lookup_fail_std_random 25,913 17,760 -8,153 -31.46% x 1.46 lookup_fail_std_serial 22,648 14,839 -7,809 -34.48% x 1.53

Usage

Add this to your Cargo.toml:

toml [dependencies] hashbrown = "0.5"

Then:

```rust use hashbrown::HashMap;

let mut map = HashMap::new(); map.insert(1, "one"); ```

This crate has the following Cargo features:

License

Licensed under either of:

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.