graph_layout/
lib.rs

1pub use vector::{Vector, P2d};
2
3mod vector;
4
5#[inline]
6fn attractive_force<V>(p1: &V, p2: &V, k_s: f32) -> V where V: Vector<Scalar=f32>
7{
8    let mut force = p1.sub(p2);
9    let length = force.length_squared().sqrt();
10    let strength = length / k_s;
11    force.scale(strength);
12    return force;
13}
14
15#[inline]
16fn repulsive_force<V>(p1: &V, p2: &V, k_r: f32) -> V where V: Vector<Scalar=f32>
17{
18    let mut force = p1.sub(p2);
19    let length_squared = force.length_squared();
20    if length_squared > 0.0 {
21        let strength = k_r / length_squared;
22        force.scale(strength);
23    }
24    return force;
25}
26
27fn calculate_node_forces<V>(forces: &mut[V], node_positions: &[V], node_neighbors: &[Vec<usize>],
28                  k_r: f32, k_s: f32) where V: Vector<Scalar=f32> {
29    let n = forces.len();
30    assert!(node_positions.len() == n);
31    assert!(node_neighbors.len() == n);
32
33    // Reset all forces to zero.
34    for force in &mut forces[..] {
35        force.reset();
36    }
37
38    // Calculate repulsive force between all pairs.
39    for i1 in 0 .. n - 1 {
40        for i2 in i1 + 1 .. n {
41            let force = repulsive_force(&node_positions[i1], &node_positions[i2], k_r);
42            forces[i1].add_scaled(1.0, &force);
43            forces[i2].add_scaled(-1.0, &force);
44        }
45    }
46
47    // Calculate spring force between adjacent pairs.
48    for i1 in 0 .. n {
49        for i2 in node_neighbors[i1].iter().map(|&i| i as usize) {
50            if i1 < i2 {
51                let force = attractive_force(&node_positions[i1], &node_positions[i2], k_s);
52                forces[i1].add_scaled(-1.0, &force);
53                forces[i2].add_scaled(1.0, &force);
54            }
55        }
56    }
57}
58
59fn update_node_positions<V>(forces: &[V], node_positions: &mut[V], step: f32, min_pos: &V, max_pos: &V) -> f32
60where V: Vector<Scalar=f32> {
61    let n = forces.len();
62    assert!(node_positions.len() == n);
63
64    let mut sum_distance = 0.0;
65
66    for i in 0..n {
67        let before = node_positions[i].clone();
68
69        let length = forces[i].length_squared().sqrt();
70        if length > 0.0 {
71            // XXX: can we treat the scaled force as moved distance?
72            node_positions[i].add_scaled(step / length, &forces[i]);
73        }
74        node_positions[i].clip_within(min_pos, max_pos);
75
76        // add up the moved distance
77        sum_distance += before.sub(&node_positions[i]).length_squared().sqrt();
78    }
79
80    return sum_distance;
81}
82
83pub fn fruchterman_reingold<F,V>(step_fn: F, max_iter: usize, converge_eps: f32, k_r: f32, k_s: f32, min_pos: &V, max_pos: &V,
84                             node_positions: &mut[V], node_neighbors: &[Vec<usize>])
85where V: Vector<Scalar=f32>, F: Fn(usize) -> f32
86{
87    let n = node_positions.len();
88    assert!(node_neighbors.len() == n);
89
90    // initialize forces
91    let mut forces: Vec<V> = (0..n).map(|_| V::new()).collect();
92
93    let mut iter: usize = 0;
94    while iter < max_iter {
95        let step = step_fn(iter);
96        iter += 1;
97
98        calculate_node_forces(&mut forces, node_positions, node_neighbors, k_r, k_s);
99        let dist_moved = update_node_positions(&forces, node_positions, step, min_pos, max_pos);
100        if dist_moved < converge_eps {
101            break;
102        }
103    }
104}
105
106pub fn typical_fruchterman_reingold_2d(area: f32, node_positions: &mut[P2d], node_neighbors: &[Vec<usize>]) {
107    let n = node_positions.len();
108    assert!(node_neighbors.len() == n);
109
110    const MAX_ITER: usize = 300;
111    const EPS: f32 = 0.1;
112    const OPT_PAIR_SQR_DIST_SCALE: f32 = 0.3;
113
114    let min_pos = P2d(0.0, 0.0);
115    let max_pos = P2d(1.0, 1.0);
116    let step_fn = |iter| { 1.0 / (1.0 + (iter as f32) * 0.1) };
117
118    let k_r: f32 = OPT_PAIR_SQR_DIST_SCALE * area / (n as f32);
119    let k_s = k_r.sqrt();
120
121    fruchterman_reingold(step_fn, MAX_ITER, EPS, k_r, k_s, &min_pos, &max_pos, node_positions, node_neighbors);
122}
graph_layout/lib.rs

graph_layout/
lib.rs
