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GTrie

Build Status

Trie is the library that implements the trie.

Trie is a generic data structure, written Trie<T, U> where T is node key type and U is a value type.

Motivation

Trie may be faster than other data structures in some cases.

For example, Trie may be used as a replacement for std::HashMap in case of a dictionary where the number of words in dictionary is significantly less than number of different words in the input and matching probability is low.

Usage

use gtrie::Trie;

let mut t = Trie::new();

t.insert("this".chars(), 1);
t.insert("trie".chars(), 2);
t.insert("contains".chars(), 3);
t.insert("a".chars(), 4);
t.insert("number".chars(), 5);
t.insert("of".chars(), 6);
t.insert("words".chars(), 7);

assert_eq!(t.contains_key("number".chars()), true);
assert_eq!(t.contains_key("not_existing_key".chars()), false);
assert_eq!(t.get_value("words".chars()), Some(7));
assert_eq!(t.get_value("none".chars()), None);

Benchmarks

Benchmark std::HashMap<String, String> vs gtrie::Trie shows that Trie is significantly faster in the case of key mismatch but significantly slower in the case of matching key.

$ cargo bench
test hash_map_massive_match                        ... bench:     150,127 ns/iter (+/- 12,986)
test hash_map_massive_mismatch_on_0                ... bench:      93,246 ns/iter (+/- 5,108)
test hash_map_massive_mismatch_on_0_one_symbol_key ... bench:      93,706 ns/iter (+/- 5,908)
test hash_map_match                                ... bench:          24 ns/iter (+/- 3)
test hash_map_mismatch                             ... bench:          20 ns/iter (+/- 0)
test trie_massive_match                            ... bench:     231,343 ns/iter (+/- 4,940)
test trie_massive_mismatch_on_0                    ... bench:      28,743 ns/iter (+/- 8,401)
test trie_massive_mismatch_on_1                    ... bench:      28,734 ns/iter (+/- 1,839)
test trie_massive_mismatch_on_2                    ... bench:      28,760 ns/iter (+/- 2,582)
test trie_massive_mismatch_on_3                    ... bench:      28,829 ns/iter (+/- 2,504)
test trie_match                                    ... bench:          10 ns/iter (+/- 1)
test trie_mismatch                                 ... bench:           5 ns/iter (+/- 0)

Important

Search performance is highly dependent on the data stored in Trie and may be as significantly faster than std::HashMap as significantly slower.

Contribution

Source code and issues are hosted on GitHub:

https://github.com/aserebryakov/trie-rs

License

MIT License

Changelog

0.4.0

  • Significant performance improvement due to switch to data oriented model

0.3.0

  • Significantly improved performance of the key mismatch case
  • API is updated to be closer to std::HashMap

0.2.1

  • Benchmarks are improved

0.2.0

  • API is updated to be closer to std::HashMap

0.1.1

  • Basic trie implentation