jellyfish 1.0.0

Approximate and phonetic matching of strings.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138

use crate::common::FastVec;
use ahash::AHashMap;
use smallvec::smallvec;
use std::cmp;
use unicode_segmentation::UnicodeSegmentation;

fn range_vec(size: usize) -> FastVec<usize> {
    let mut vec = FastVec::new();
    let mut p: usize = 0;
    vec.resize_with(size, || {
        p += 1;
        p - 1
    });
    vec
}

pub fn vec_levenshtein_distance<T: PartialEq>(v1: &FastVec<T>, v2: &FastVec<T>) -> usize {
    let rows = v1.len() + 1;
    let cols = v2.len() + 1;

    if rows == 1 {
        return cols - 1;
    } else if cols == 1 {
        return rows - 1;
    }

    let mut cur = range_vec(cols);

    for r in 1..rows {
        // make a copy of the previous row so we can edit cur
        let prev = cur.clone();
        cur = smallvec![0; cols];
        cur[0] = r;
        for c in 1..cols {
            // deletion cost or insertion cost
            let del_or_ins = cmp::min(prev[c] + 1, cur[c - 1] + 1);
            let edit = prev[c - 1] + (if v1[r - 1] == v2[c - 1] { 0 } else { 1 });
            cur[c] = cmp::min(del_or_ins, edit);
        }
    }

    // last element of bottom row
    cur[cols - 1]
}

pub fn vec_damerau_levenshtein_distance<T: Eq + std::hash::Hash>(
    v1: &FastVec<T>,
    v2: &FastVec<T>,
) -> usize {
    let len1 = v1.len();
    let len2 = v2.len();
    let infinite = len1 + len2;

    let mut item_position = AHashMap::with_capacity(cmp::max(len1, len2));
    // distance matrix
    // try using a flat array instead of a 2d vec for speed
    let mut score: Vec<usize> = vec![0; (len1 + 2) * (len2 + 2)];
    let idx = |i: usize, j: usize| (len2 + 2) * i + j;
    //let mut score: FastVec<FastVec<usize>> = smallvec![smallvec![0; len2 + 2]; len1 + 2];

    score[0] = infinite;
    for i in 0..=len1 {
        score[idx(i + 1, 0)] = infinite;
        score[idx(i + 1, 1)] = i;
    }
    for i in 0..=len2 {
        score[idx(0, i + 1)] = infinite;
        score[idx(1, i + 1)] = i;
    }

    for i in 1..len1 + 1 {
        let mut db = 0;
        for j in 1..len2 + 1 {
            let i1 = item_position.entry(&v2[j - 1]).or_insert(0);
            let j1 = db;
            let mut cost = 1;
            if v1[i - 1] == v2[j - 1] {
                cost = 0;
                db = j;
            }

            // min of the four options
            score[idx(i + 1, j + 1)] = cmp::min(
                // substitution & insertion
                cmp::min(score[idx(i, j)] + cost, score[idx(i + 1, j)] + 1),
                cmp::min(
                    // deletion & transposition
                    score[idx(i, j + 1)] + 1,
                    score[idx(*i1, j1)] + (i - *i1 - 1) + 1 + (j - j1 - 1),
                ),
            )
        }
        // store the position of this character for transpositions
        item_position.insert(&v1[i - 1], i);
    }

    score[idx(len1 + 1, len2 + 1)]
}

pub fn levenshtein_distance(s1: &str, s2: &str) -> usize {
    if s1 == s2 {
        return 0;
    }

    let us1 = UnicodeSegmentation::graphemes(s1, true).collect::<FastVec<&str>>();
    let us2 = UnicodeSegmentation::graphemes(s2, true).collect::<FastVec<&str>>();

    vec_levenshtein_distance(&us1, &us2)
}

pub fn damerau_levenshtein_distance(s1: &str, s2: &str) -> usize {
    if s1 == s2 {
        return 0;
    }

    let us1 = UnicodeSegmentation::graphemes(s1, true).collect::<FastVec<&str>>();
    let us2 = UnicodeSegmentation::graphemes(s2, true).collect::<FastVec<&str>>();

    vec_damerau_levenshtein_distance(&us1, &us2)
}

#[cfg(test)]
mod test {
    use super::*;
    use crate::testutils::testutils;
    #[test]
    fn test_levenshtein() {
        testutils::test_distance_func("testdata/levenshtein.csv", levenshtein_distance);
    }

    #[test]
    fn test_damerau_levenshtein() {
        testutils::test_distance_func(
            "testdata/damerau_levenshtein.csv",
            damerau_levenshtein_distance,
        );
    }
}