sinistra 0.1.0-202603071957

A generic graph framework with pluggable storage and topology and streaming graph algorithms.
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

use std::collections::VecDeque;

use crate::graph::{
    EdgeHandle, EndpointTopology, Graph, GraphEdgesExt, GraphEndpointsExt, Policy, PropertySet,
    Traversal, TraversalEvent, VertexHandle,
};

pub struct Bfs<'graph, G, V> {
    graph: &'graph G,
    frontier: VecDeque<VertexHandle>,
    visited: V,
}

impl<'graph, G, V> Bfs<'graph, G, V>
where
    G: Graph,
    V: PropertySet<Key = VertexHandle> + Default,
    G::Topology: EndpointTopology,
{
    pub fn new(graph: &'graph G, start: VertexHandle, visited: V) -> Traversal<Self> {
        let bfs = Self {
            graph,
            frontier: VecDeque::new(),
            visited,
        };

        Traversal::new(bfs, start)
    }
}

impl<'graph, G, V> Policy for Bfs<'graph, G, V>
where
    G: Graph,
    V: PropertySet<Key = VertexHandle>,
    G::Topology: EndpointTopology,
{
    type Event = Event;
    type Item = VertexHandle;

    fn start(&mut self, start: VertexHandle) {
        self.frontier.push_back(start);
    }

    fn pop(&mut self) -> Option<Self::Item> {
        self.frontier.pop_front()
    }

    fn process(&mut self, source: VertexHandle, pending: &mut VecDeque<Self::Event>) {
        for edge in self.graph.out_edges(source) {
            let (_, target) = self.graph.edge_endpoints(edge).unwrap();

            pending.push_back(Event::Core(TraversalEvent::Examine {
                source,
                target,
                edge,
            }));

            if self.visited.mark(target, true) {
                self.frontier.push_back(target);

                pending.push_back(Event::TreeEdge {
                    source,
                    edge,
                    target,
                });

                pending.push_back(Event::Core(TraversalEvent::Discover { vertex: target }));
            }
        }

        pending.push_back(Event::Core(TraversalEvent::Finish { vertex: source }));
    }
}

#[derive(Debug, Clone, Copy)]
pub enum Event {
    Core(TraversalEvent),

    TreeEdge {
        source: VertexHandle,
        edge: EdgeHandle,
        target: VertexHandle,
    },
}

pub fn bfs<G, V>(graph: &G, start: VertexHandle) -> Traversal<Bfs<'_, G, V>>
where
    G: Graph,
    V: PropertySet<Key = VertexHandle> + Default,
    G::Topology: EndpointTopology,
{
    Bfs::new(graph, start, V::default())
}

pub fn bfs_vertices<G, V>(graph: &G, start: VertexHandle) -> impl Iterator<Item = VertexHandle>
where
    G: Graph,
    V: PropertySet<Key = VertexHandle> + Default,
    G::Topology: EndpointTopology,
{
    bfs::<G, V>(graph, start).filter_map(|event| {
        if let Event::Core(TraversalEvent::Discover { vertex }) = event {
            Some(vertex)
        } else {
            None
        }
    })
}

pub fn bfs_tree_edges<G, V>(
    graph: &G,
    start: VertexHandle,
) -> impl Iterator<Item = (VertexHandle, EdgeHandle, VertexHandle)>
where
    G: Graph,
    V: PropertySet<Key = VertexHandle> + Default,
    G::Topology: EndpointTopology,
{
    bfs::<G, V>(graph, start).filter_map(|event| {
        if let Event::TreeEdge {
            source,
            edge,
            target,
        } = event
        {
            Some((source, edge, target))
        } else {
            None
        }
    })
}