weavatrix-graph 0.6.1

Deterministic, evidence-carrying graph primitives for repository intelligence
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

use super::{Predecessors, Step};
use crate::{GraphError, IndexGraphView, Result};

#[allow(clippy::too_many_arguments)]
pub(super) fn shortest_residual_path<G>(
    graph: &G,
    nodes: &[Option<G::Node>],
    source: usize,
    sink: usize,
    capacities: &[u64],
    costs: &[i64],
    flows: &[u64],
) -> Result<Option<Predecessors<G::Edge>>>
where
    G: IndexGraphView,
{
    let mut distances = vec![None; graph.node_bound()];
    let mut predecessors = vec![None; graph.node_bound()];
    distances[source] = Some(0_i128);
    for _ in 1..graph.node_count() {
        if !relax_residual(
            graph,
            nodes,
            capacities,
            costs,
            flows,
            &mut distances,
            &mut predecessors,
        )? {
            break;
        }
    }
    let mut probe = predecessors.clone();
    if relax_residual(
        graph,
        nodes,
        capacities,
        costs,
        flows,
        &mut distances,
        &mut probe,
    )? {
        return Err(GraphError::NegativeCycle {
            algorithm: "minimum-cost maximum flow",
        });
    }
    Ok(distances[sink].map(|_| predecessors))
}

#[allow(clippy::too_many_arguments)]
fn relax_residual<G>(
    graph: &G,
    nodes: &[Option<G::Node>],
    capacities: &[u64],
    costs: &[i64],
    flows: &[u64],
    distances: &mut [Option<i128>],
    predecessors: &mut Predecessors<G::Edge>,
) -> Result<bool>
where
    G: IndexGraphView,
{
    let mut changed = false;
    for source in 0..nodes.len() {
        let Some(distance) = distances[source] else {
            continue;
        };
        let Some(node) = nodes[source] else {
            continue;
        };
        for edge in graph.outgoing_edges(node) {
            let slot = G::edge_slot(edge);
            if capacities[slot] > flows[slot] {
                let target = graph
                    .edge_endpoints(edge)
                    .map_or(source, |ends| G::node_slot(ends.target()));
                changed |= relax(
                    distance,
                    i128::from(costs[slot]),
                    source,
                    target,
                    edge,
                    true,
                    distances,
                    predecessors,
                )?;
            }
        }
        for edge in graph.incoming_edges(node) {
            let slot = G::edge_slot(edge);
            if flows[slot] > 0 {
                let target = graph
                    .edge_endpoints(edge)
                    .map_or(source, |ends| G::node_slot(ends.source()));
                changed |= relax(
                    distance,
                    -i128::from(costs[slot]),
                    source,
                    target,
                    edge,
                    false,
                    distances,
                    predecessors,
                )?;
            }
        }
    }
    Ok(changed)
}

#[allow(clippy::too_many_arguments)]
fn relax<Edge: Copy>(
    distance: i128,
    cost: i128,
    source: usize,
    target: usize,
    edge: Edge,
    forward: bool,
    distances: &mut [Option<i128>],
    predecessors: &mut Predecessors<Edge>,
) -> Result<bool> {
    let candidate = distance
        .checked_add(cost)
        .ok_or(GraphError::ArithmeticOverflow {
            operation: "minimum-cost residual relaxation",
        })?;
    if distances[target].is_some_and(|known| candidate >= known) {
        return Ok(false);
    }
    distances[target] = Some(candidate);
    predecessors[target] = Some(Step {
        previous: source,
        edge,
        forward,
    });
    Ok(true)
}