tests/floyd_warshall.rs

use petgraph::algo::floyd_warshall;
use petgraph::{prelude::*, Directed, Graph, Undirected};
use std::collections::HashMap;

#[test]
fn floyd_warshall_uniform_weight() {
    let mut graph: Graph<(), (), Directed> = Graph::new();
    let a = graph.add_node(());
    let b = graph.add_node(());
    let c = graph.add_node(());
    let d = graph.add_node(());
    let e = graph.add_node(());
    let f = graph.add_node(());
    let g = graph.add_node(());
    let h = graph.add_node(());

    graph.extend_with_edges(&[
        (a, b),
        (b, c),
        (c, d),
        (d, a),
        (e, f),
        (b, e),
        (f, g),
        (g, h),
        (h, e),
    ]);
    // a ----> b ----> e ----> f
    // ^       |       ^       |
    // |       v       |       v
    // d <---- c       h <---- g

    let inf = std::i32::MAX;
    let expected_res: HashMap<(NodeIndex, NodeIndex), i32> = [
        ((a, a), 0),
        ((a, b), 1),
        ((a, c), 2),
        ((a, d), 3),
        ((a, e), 2),
        ((a, f), 3),
        ((a, g), 4),
        ((a, h), 5),
        ((b, a), 3),
        ((b, b), 0),
        ((b, c), 1),
        ((b, d), 2),
        ((b, e), 1),
        ((b, f), 2),
        ((b, g), 3),
        ((b, h), 4),
        ((c, a), 2),
        ((c, b), 3),
        ((c, c), 0),
        ((c, d), 1),
        ((c, e), 4),
        ((c, f), 5),
        ((c, g), 6),
        ((c, h), 7),
        ((d, a), 1),
        ((d, b), 2),
        ((d, c), 3),
        ((d, d), 0),
        ((d, e), 3),
        ((d, f), 4),
        ((d, g), 5),
        ((d, h), 6),
        ((e, a), inf),
        ((e, b), inf),
        ((e, c), inf),
        ((e, d), inf),
        ((e, e), 0),
        ((e, f), 1),
        ((e, g), 2),
        ((e, h), 3),
        ((f, a), inf),
        ((f, b), inf),
        ((f, c), inf),
        ((f, d), inf),
        ((f, e), 3),
        ((f, f), 0),
        ((f, g), 1),
        ((f, h), 2),
        ((g, a), inf),
        ((g, b), inf),
        ((g, c), inf),
        ((g, d), inf),
        ((g, e), 2),
        ((g, f), 3),
        ((g, g), 0),
        ((g, h), 1),
        ((h, a), inf),
        ((h, b), inf),
        ((h, c), inf),
        ((h, d), inf),
        ((h, e), 1),
        ((h, f), 2),
        ((h, g), 3),
        ((h, h), 0),
    ]
    .iter()
    .cloned()
    .collect();
    let res = floyd_warshall(&graph, |_| 1_i32).unwrap();

    let nodes = [a, b, c, d, e, f, g, h];
    for node1 in &nodes {
        for node2 in &nodes {
            assert_eq!(
                res.get(&(*node1, *node2)).unwrap(),
                expected_res.get(&(*node1, *node2)).unwrap()
            );
        }
    }
}

#[test]
fn floyd_warshall_weighted() {
    let mut graph: Graph<(), (), Directed> = Graph::new();
    let a = graph.add_node(());
    let b = graph.add_node(());
    let c = graph.add_node(());
    let d = graph.add_node(());

    graph.extend_with_edges(&[(a, b), (a, c), (a, d), (b, c), (b, d), (c, d)]);

    let inf = std::i32::MAX;
    let expected_res: HashMap<(NodeIndex, NodeIndex), i32> = [
        ((a, a), 0),
        ((a, b), 1),
        ((a, c), 3),
        ((a, d), 3),
        ((b, a), inf),
        ((b, b), 0),
        ((b, c), 2),
        ((b, d), 2),
        ((c, a), inf),
        ((c, b), inf),
        ((c, c), 0),
        ((c, d), 2),
        ((d, a), inf),
        ((d, b), inf),
        ((d, c), inf),
        ((d, d), 0),
    ]
    .iter()
    .cloned()
    .collect();

    let weight_map: HashMap<(NodeIndex, NodeIndex), i32> = [
        ((a, a), 0),
        ((a, b), 1),
        ((a, c), 4),
        ((a, d), 10),
        ((b, b), 0),
        ((b, c), 2),
        ((b, d), 2),
        ((c, c), 0),
        ((c, d), 2),
    ]
    .iter()
    .cloned()
    .collect();

    let res = floyd_warshall(&graph, |edge| {
        if let Some(weight) = weight_map.get(&(edge.source(), edge.target())) {
            *weight
        } else {
            inf
        }
    })
    .unwrap();

    let nodes = [a, b, c, d];
    for node1 in &nodes {
        for node2 in &nodes {
            assert_eq!(
                res.get(&(*node1, *node2)).unwrap(),
                expected_res.get(&(*node1, *node2)).unwrap()
            );
        }
    }
}

#[test]
fn floyd_warshall_weighted_undirected() {
    let mut graph: Graph<(), (), Undirected> = Graph::new_undirected();
    let a = graph.add_node(());
    let b = graph.add_node(());
    let c = graph.add_node(());
    let d = graph.add_node(());

    graph.extend_with_edges(&[(a, b), (a, c), (a, d), (b, d), (c, b), (c, d)]);

    let inf = std::i32::MAX;
    let expected_res: HashMap<(NodeIndex, NodeIndex), i32> = [
        ((a, a), 0),
        ((a, b), 1),
        ((a, c), 3),
        ((a, d), 3),
        ((b, a), 1),
        ((b, b), 0),
        ((b, c), 2),
        ((b, d), 2),
        ((c, a), 3),
        ((c, b), 2),
        ((c, c), 0),
        ((c, d), 2),
        ((d, a), 3),
        ((d, b), 2),
        ((d, c), 2),
        ((d, d), 0),
    ]
    .iter()
    .cloned()
    .collect();

    let weight_map: HashMap<(NodeIndex, NodeIndex), i32> = [
        ((a, a), 0),
        ((a, b), 1),
        ((a, c), 4),
        ((a, d), 10),
        ((b, b), 0),
        ((b, d), 2),
        ((c, b), 2),
        ((c, c), 0),
        ((c, d), 2),
    ]
    .iter()
    .cloned()
    .collect();

    let res = floyd_warshall(&graph, |edge| {
        if let Some(weight) = weight_map.get(&(edge.source(), edge.target())) {
            *weight
        } else {
            inf
        }
    })
    .unwrap();

    let nodes = [a, b, c, d];
    for node1 in &nodes {
        for node2 in &nodes {
            assert_eq!(
                res.get(&(*node1, *node2)).unwrap(),
                expected_res.get(&(*node1, *node2)).unwrap()
            );
        }
    }
}

#[test]
fn floyd_warshall_negative_cycle() {
    let mut graph: Graph<(), (), Directed> = Graph::new();
    let a = graph.add_node(());
    let b = graph.add_node(());
    let c = graph.add_node(());

    graph.extend_with_edges(&[(a, b), (b, c), (c, a)]);

    let inf = std::i32::MAX;

    let weight_map: HashMap<(NodeIndex, NodeIndex), i32> = [
        ((a, a), 0),
        ((a, b), 1),
        ((b, b), 0),
        ((b, c), -3),
        ((c, c), 0),
        ((c, a), 1),
    ]
    .iter()
    .cloned()
    .collect();

    let res = floyd_warshall(&graph, |edge| {
        if let Some(weight) = weight_map.get(&(edge.source(), edge.target())) {
            *weight
        } else {
            inf
        }
    });

    assert!(res.is_err());
}