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[performance] Improve the performance of damerau_levenshtein #32

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merged 4 commits into from
Apr 8, 2019
Merged

[performance] Improve the performance of damerau_levenshtein #32

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d32cdcf
[performance] Improve the performance of damerau_levenshtein
lovasoa Mar 30, 2019
f242bdf
Switch back to rust 2015 to fix CI
lovasoa Mar 31, 2019
7d8494e
Increase minimum required rust version to 1.31
lovasoa Mar 31, 2019
5ff3cdf
Simplify the levenshtein function
lovasoa Mar 31, 2019
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2 changes: 1 addition & 1 deletion .travis.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,7 @@ os:
- windows

rust:
- 1.27.0
- 1.31.0
- nightly
- beta
- stable
Expand Down
4 changes: 4 additions & 0 deletions Cargo.toml
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Expand Up @@ -14,6 +14,10 @@ repository = "https://github.com/dguo/strsim-rs"
documentation = "https://docs.rs/strsim/"
exclude = ["/.travis.yml", "/appveyor.yml", "/dev"]

[dependencies]
hashbrown = "0.1.8"
ndarray = "0.12.1"

[badges]
travis-ci = { repository = "dguo/strsim-rs" }
appveyor = { repository = "dguo/strsim-rs" }
83 changes: 41 additions & 42 deletions src/lib.rs
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@@ -1,13 +1,18 @@
//! This library implements string similarity metrics.

extern crate hashbrown;
extern crate ndarray;

use std::char;
use std::cmp::{max, min};
use std::collections::HashMap;
use std::error::Error;
use std::fmt::{self, Display, Formatter};
use std::hash::Hash;
use std::str::Chars;

use hashbrown::HashMap;
use ndarray::Array2;

#[derive(Debug, PartialEq)]
pub enum StrSimError {
DifferentLengthArgs,
Expand Down Expand Up @@ -103,7 +108,7 @@ pub fn generic_jaro<'a, 'b, Iter1, Iter2, Elem1, Elem2>(a: &'a Iter1, b: &'b Ite

for (j, b_elem) in b.into_iter().enumerate() {
if min_bound <= j && j <= max_bound && a_elem == b_elem &&
!b_consumed[j] {
!b_consumed[j] {
b_consumed[j] = true;
matches += 1.0;

Expand All @@ -121,8 +126,8 @@ pub fn generic_jaro<'a, 'b, Iter1, Iter2, Elem1, Elem2>(a: &'a Iter1, b: &'b Ite
0.0
} else {
(1.0 / 3.0) * ((matches / a_len as f64) +
(matches / b_len as f64) +
((matches - transpositions) / matches))
(matches / b_len as f64) +
((matches - transpositions) / matches))
}
}

Expand Down Expand Up @@ -161,7 +166,7 @@ pub fn generic_jaro_winkler<'a, 'b, Iter1, Iter2, Elem1, Elem2>(a: &'a Iter1, b:
let prefix_length = a.into_iter()
.zip(b.into_iter())
.take_while(|&(ref a_elem, ref b_elem)| a_elem == b_elem)
.count();
.count();

let jaro_winkler_distance =
jaro_distance + (0.1 * prefix_length as f64 * (1.0 - jaro_distance));
Expand Down Expand Up @@ -197,25 +202,21 @@ pub fn generic_levenshtein<'a, 'b, Iter1, Iter2, Elem1, Elem2>(a: &'a Iter1, b:
where &'a Iter1: IntoIterator<Item=Elem1>,
&'b Iter2: IntoIterator<Item=Elem2>,
Elem1: PartialEq<Elem2> {
let a_len = a.into_iter().count();
let b_len = b.into_iter().count();

if a_len == 0 { return b_len; }
if b_len == 0 { return a_len; }
if a.into_iter().next().is_none() { return b_len; }

let mut cache: Vec<usize> = (1..b_len+1).collect();

let mut result = 0;
let mut distance_a;
let mut distance_b;

for (i, a_elem) in a.into_iter().enumerate() {
result = i;
distance_b = i;
result = i + 1;
let mut distance_b = i;

for (j, b_elem) in b.into_iter().enumerate() {
let cost = if a_elem == b_elem { 0 } else { 1 };
distance_a = distance_b + cost;
let cost = if a_elem == b_elem { 0usize } else { 1usize };
let distance_a = distance_b + cost;
distance_b = cache[j];
result = min(result + 1, min(distance_a, distance_b + 1));
cache[j] = result;
Expand Down Expand Up @@ -293,7 +294,7 @@ pub fn osa_distance(a: &str, b: &str) -> usize {
min(prev_distances[j + 1] + 1,
prev_distances[j] + cost));
if i > 0 && j > 0 && a_char != b_char &&
a_char == prev_b_char && b_char == prev_a_char {
a_char == prev_b_char && b_char == prev_a_char {
curr_distances[j + 1] = min(curr_distances[j + 1],
prev_two_distances[j - 1] + 1);
}
Expand Down Expand Up @@ -326,55 +327,53 @@ pub fn generic_damerau_levenshtein<Elem>(a_elems: &[Elem], b_elems: &[Elem]) ->
if a_len == 0 { return b_len; }
if b_len == 0 { return a_len; }

let mut distances = vec![vec![0; b_len + 2]; a_len + 2];
let mut distances = Array2::<usize>::zeros((a_len + 2, b_len + 2));
let max_distance = a_len + b_len;
distances[0][0] = max_distance;
distances[[0, 0]] = max_distance;

for i in 0..(a_len + 1) {
distances[i + 1][0] = max_distance;
distances[i + 1][1] = i;
distances[[i + 1, 0]] = max_distance;
distances[[i + 1, 1]] = i;
}

for j in 0..(b_len + 1) {
distances[0][j + 1] = max_distance;
distances[1][j + 1] = j;
distances[[0, j + 1]] = max_distance;
distances[[1, j + 1]] = j;
}

let mut elems: HashMap<Elem, usize> = HashMap::new();
let mut elems: HashMap<Elem, usize> = HashMap::with_capacity(64);

for i in 1..(a_len + 1) {
let mut db = 0;

for j in 1..(b_len + 1) {
let k = match elems.get(&b_elems[j - 1]) {
Some(value) => value.clone(),
Some(&value) => value,
None => 0
};

let l = db;

let mut cost = 1;
let insertion_cost = distances[[i, j + 1]] + 1;
let deletion_cost = distances[[i + 1, j]] + 1;
let transposition_cost = distances[[k, db]] + (i - k - 1) + 1 +
(j - db - 1);

let mut substitution_cost = distances[[i, j]] + 1;
if a_elems[i - 1] == b_elems[j - 1] {
cost = 0;
db = j;
substitution_cost -= 1;
}

let substitution_cost = distances[i][j] + cost;
let insertion_cost = distances[i][j + 1] + 1;
let deletion_cost = distances[i + 1][j] + 1;
let transposition_cost = distances[k][l] + (i - k - 1) + 1 +
(j - l - 1);

distances[i + 1][j + 1] = min(substitution_cost,
min(insertion_cost,
min(deletion_cost,
transposition_cost)));
distances[[i + 1, j + 1]] = min(substitution_cost,
min(insertion_cost,
min(deletion_cost,
transposition_cost)));
}

elems.insert(a_elems[i - 1].clone(), i);
}

distances[a_len + 1][b_len + 1]
distances[[a_len + 1, b_len + 1]]
}

/// Like optimal string alignment, but substrings can be edited an unlimited
Expand Down Expand Up @@ -457,7 +456,7 @@ mod tests {

#[test]
fn jaro_both_empty() {
assert_eq!(1.0, jaro("", ""));
assert_eq!(1.0, jaro("", ""));
}

#[test]
Expand Down Expand Up @@ -545,9 +544,9 @@ mod tests {
#[test]
fn jaro_winkler_multibyte() {
assert!((0.89 - jaro_winkler("testabctest", "testöঙ香test")).abs() <
0.001);
0.001);
assert!((0.89 - jaro_winkler("testöঙ香test", "testabctest")).abs() <
0.001);
0.001);
}

#[test]
Expand Down Expand Up @@ -580,7 +579,7 @@ mod tests {
#[test]
fn jaro_winkler_long_prefix() {
assert!((0.911 - jaro_winkler("cheeseburger", "cheese fries")).abs() <
0.001);
0.001);
}

#[test]
Expand All @@ -597,7 +596,7 @@ mod tests {
fn jaro_winkler_very_long_prefix() {
assert!((1.0 - jaro_winkler("thequickbrownfoxjumpedoverx",
"thequickbrownfoxjumpedovery")).abs() <
0.001);
0.001);
}

#[test]
Expand Down