Bug: 172365435

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  1. fdbed56 Update vpnprofilestore_test to legacykeystore_test in TEST_MAPPING am: 433ff92f39 am: 8686d150a1 by easoncylee · 4 months ago master
  2. 8686d15 Update vpnprofilestore_test to legacykeystore_test in TEST_MAPPING am: 433ff92f39 by easoncylee · 4 months ago
  3. 433ff92 Update vpnprofilestore_test to legacykeystore_test in TEST_MAPPING by easoncylee · 4 months ago android-s-beta-4 android-s-beta-5 android-s-beta-3
  4. f9fb091 Upgrade rust/crates/hashbrown to 0.11.2 am: 486b32152e am: 8c1f11ab5b am: 2425c10714 by Joel Galenson · 7 months ago android12-dev
  5. 2425c10 Upgrade rust/crates/hashbrown to 0.11.2 am: 486b32152e am: 8c1f11ab5b by Joel Galenson · 7 months ago

hashbrown

Build Status Crates.io Documentation Rust

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. However you may still want to use this crate instead since it works in environments without std, such as embedded systems and kernels.

Change log

Features

  • Drop-in replacement for the standard library HashMap and HashSet types.
  • Uses AHash as the default hasher, which is much faster than SipHash. However, AHash does not provide the same level of HashDoS resistance as SipHash, so if that is important to you, you might want to consider using a different hasher.
  • Around 2x faster than the previous standard library HashMap.
  • Lower memory usage: only 1 byte of overhead per entry instead of 8.
  • Compatible with #[no_std] (but requires a global allocator with the alloc crate).
  • Empty hash maps do not allocate any memory.
  • SIMD lookups to scan multiple hash entries in parallel.

Performance

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

With the hashbrown default AHash hasher:

nameoldstdhash ns/iterhashbrown ns/iterdiff ns/iterdiff %speedup
insert_ahash_highbits18,8658,020-10,845-57.49%x 2.35
insert_ahash_random19,7118,019-11,692-59.32%x 2.46
insert_ahash_serial19,3656,463-12,902-66.63%x 3.00
insert_erase_ahash_highbits51,13617,916-33,220-64.96%x 2.85
insert_erase_ahash_random51,15717,688-33,469-65.42%x 2.89
insert_erase_ahash_serial45,47914,895-30,584-67.25%x 3.05
iter_ahash_highbits1,3991,092-307-21.94%x 1.28
iter_ahash_random1,5861,059-527-33.23%x 1.50
iter_ahash_serial3,1681,079-2,089-65.94%x 2.94
lookup_ahash_highbits32,3514,792-27,559-85.19%x 6.75
lookup_ahash_random17,4194,817-12,602-72.35%x 3.62
lookup_ahash_serial15,2543,606-11,648-76.36%x 4.23
lookup_fail_ahash_highbits21,1874,369-16,818-79.38%x 4.85
lookup_fail_ahash_random21,5504,395-17,155-79.61%x 4.90
lookup_fail_ahash_serial19,4503,176-16,274-83.67%x 6.12

With the libstd default SipHash hasher:

nameoldstdhash ns/iterhashbrown ns/iterdiff ns/iterdiff %speedup
insert_std_highbits19,21616,885-2,331-12.13%x 1.14
insert_std_random19,17917,034-2,145-11.18%x 1.13
insert_std_serial19,46217,493-1,969-10.12%x 1.11
insert_erase_std_highbits50,82535,847-14,978-29.47%x 1.42
insert_erase_std_random51,44835,392-16,056-31.21%x 1.45
insert_erase_std_serial87,71138,091-49,620-56.57%x 2.30
iter_std_highbits1,3781,159-219-15.89%x 1.19
iter_std_random1,3951,132-263-18.85%x 1.23
iter_std_serial1,7041,105-599-35.15%x 1.54
lookup_std_highbits17,19513,642-3,553-20.66%x 1.26
lookup_std_random17,18113,773-3,408-19.84%x 1.25
lookup_std_serial15,48313,651-1,832-11.83%x 1.13
lookup_fail_std_highbits20,92613,474-7,452-35.61%x 1.55
lookup_fail_std_random21,76613,505-8,261-37.95%x 1.61
lookup_fail_std_serial19,33613,519-5,817-30.08%x 1.43

Usage

Add this to your Cargo.toml:

[dependencies]
hashbrown = "0.11"

Then:

use hashbrown::HashMap;

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

Flags

This crate has the following Cargo features:

  • nightly: Enables nightly-only features including: #[may_dangle].
  • serde: Enables serde serialization support.
  • rayon: Enables rayon parallel iterator support.
  • raw: Enables access to the experimental and unsafe RawTable API.
  • inline-more: Adds inline hints to most functions, improving run-time performance at the cost of compilation time. (enabled by default)
  • bumpalo: Provides a BumpWrapper type which allows bumpalo to be used for memory allocation.
  • ahash: Compiles with ahash as default hasher. (enabled by default)
  • ahash-compile-time-rng: Activates the compile-time-rng feature of ahash. For targets with no random number generator this pre-generates seeds at compile time and embeds them as constants. See aHash's documentation (disabled by default)

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.