weavatrix-search-vector 0.3.1

Persistent, mutable, bounded vector candidate search for Rust and Weavatrix
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
139
140
141
142
143
144
145
146
147
148
149
150

use super::mapped_search::MappedScratch;
use super::{MappedGraph, MappedVectorIndex};
use crate::mmap::Mapping;
use crate::vector::Candidate;
use std::cmp::Reverse;

impl MappedGraph {
    pub(super) fn node_layers<'a>(&self, mapping: &'a Mapping) -> &'a [u64] {
        mapping
            .u64_slice(self.node_layers_offset, self.node_count + 1)
            .expect("validated graph node-layer section")
    }

    pub(super) fn layer_neighbors<'a>(&self, mapping: &'a Mapping) -> &'a [u64] {
        mapping
            .u64_slice(self.layer_neighbors_offset, self.total_layers + 1)
            .expect("validated graph layer-neighbor section")
    }

    pub(super) fn neighbors<'a>(&self, mapping: &'a Mapping) -> &'a [u32] {
        mapping
            .u32_slice(self.neighbors_offset, self.neighbor_count)
            .expect("validated graph neighbor section")
    }

    fn node_neighbors<'a>(&self, mapping: &'a Mapping, node: usize, level: usize) -> &'a [u32] {
        let node_layers = self.node_layers(mapping);
        let layer = usize::try_from(node_layers[node]).expect("validated layer offset") + level;
        let layer_neighbors = self.layer_neighbors(mapping);
        let start = usize::try_from(layer_neighbors[layer]).expect("validated neighbor offset");
        let end = usize::try_from(layer_neighbors[layer + 1]).expect("validated neighbor offset");
        &self.neighbors(mapping)[start..end]
    }

    #[allow(clippy::too_many_arguments)]
    pub(super) fn search_into<F>(
        &self,
        index: &MappedVectorIndex,
        query: &[f32],
        inverse_norm: f32,
        expansion: usize,
        scratch: &mut MappedScratch,
        output: &mut Vec<Candidate>,
        accepts: &F,
    ) where
        F: Fn(u64) -> bool,
    {
        let Some(mut entry) = self.entry else {
            return;
        };
        for level in (1..=self.max_level).rev() {
            entry = self.greedy(index, query, inverse_norm, entry, level);
        }
        self.explore_layer(
            index,
            query,
            inverse_norm,
            entry,
            expansion,
            0,
            scratch,
            accepts,
        );
        output.extend(scratch.results.iter().copied());
    }

    fn greedy(
        &self,
        index: &MappedVectorIndex,
        query: &[f32],
        inverse_norm: f32,
        mut best: usize,
        level: usize,
    ) -> usize {
        let mut best_candidate =
            Candidate::new(index.distance_query(best, query, inverse_norm), best);
        loop {
            let mut improved = false;
            for neighbor in self.node_neighbors(&index.mapping, best, level) {
                let neighbor = *neighbor as usize;
                let candidate = Candidate::new(
                    index.distance_query(neighbor, query, inverse_norm),
                    neighbor,
                );
                if candidate < best_candidate {
                    best = neighbor;
                    best_candidate = candidate;
                    improved = true;
                }
            }
            if !improved {
                return best;
            }
        }
    }

    #[allow(clippy::too_many_arguments)]
    fn explore_layer<F>(
        &self,
        index: &MappedVectorIndex,
        query: &[f32],
        inverse_norm: f32,
        entry: usize,
        expansion: usize,
        level: usize,
        scratch: &mut MappedScratch,
        accepts: &F,
    ) where
        F: Fn(u64) -> bool,
    {
        scratch.begin();
        let first = Candidate::new(index.distance_query(entry, query, inverse_norm), entry);
        scratch.mark(entry);
        scratch.candidates.push(Reverse(first));
        if accepts(index.key_slice()[entry]) {
            scratch.results.push(first);
        }
        while let Some(Reverse(current)) = scratch.candidates.pop() {
            if scratch.results.len() >= expansion
                && scratch.results.peek().is_some_and(|worst| current > *worst)
            {
                break;
            }
            for neighbor in self.node_neighbors(&index.mapping, current.index(), level) {
                let neighbor = *neighbor as usize;
                if !scratch.mark(neighbor) {
                    continue;
                }
                let candidate = Candidate::new(
                    index.distance_query(neighbor, query, inverse_norm),
                    neighbor,
                );
                if scratch.results.len() < expansion
                    || scratch
                        .results
                        .peek()
                        .is_some_and(|worst| candidate < *worst)
                {
                    scratch.candidates.push(Reverse(candidate));
                    if accepts(index.key_slice()[neighbor]) {
                        scratch.results.push(candidate);
                        if scratch.results.len() > expansion {
                            scratch.results.pop();
                        }
                    }
                }
            }
        }
    }
}