Merge branch '65-impl-distance-variant-of-stress-centrality-algo' into 'dev'

Resolve "impl distance variant of stress centrality algo"

Closes #65

See merge request !55

wotb/Cargo.toml

 [package]
 name = "duniter-wotb"
-version = "0.8.0-a0.5"
+version = "0.8.0-a0.6"
 authors = ["nanocryk <nanocryk@duniter.org>", "elois <elois@duniter.org>"]
 description = "Makes Web of Trust computations for the Duniter project."
 repository = "https://git.duniter.org/nodes/rust/duniter-rs"

wotb/lib.rs

@@ -589,37 +589,19 @@ mod tests {
                 0, 9, 55, 216, 865,
             ]
         );
-        /*let wot_size = wot3.size();
-        let members_count = wot3.get_enabled().len() as u64;
-        assert_eq!(members_count, 59);
-        let oriented_couples_count: u64 = members_count * (members_count - 1);
-        let mut centralities = vec![0; wot_size];
-        for i in 0..wot_size {
-            for j in 0..wot_size {
-                let paths = path_finder.find_paths(&wot3, NodeId(i), NodeId(j), 5);
-                let mut intermediate_members: Vec<NodeId> = Vec::new();
-                for path in paths {
-                    if path.len() > 2 {
-                        for node_id in &path[1..path.len() - 1] {
-                            if !intermediate_members.contains(node_id) {
-                                intermediate_members.push(*node_id);
-                            }
-                        }
-                    }
-                }
-                let centralities_copy = centralities.clone();
-                for node_id in intermediate_members {
-                    let centrality = &centralities_copy[node_id.0];
-                    if let Some(tmp) = centralities.get_mut(node_id.0) {
-                        *tmp = *centrality + 1;
-                    }
-                }
-            }
-        }
-        let mut relative_centralities = Vec::with_capacity(wot_size);
-        for centrality in centralities {
-            relative_centralities.push((centrality * 100_000 / oriented_couples_count) as usize);
-        }
-        assert_eq!(relative_centralities.len(), 59);*/
+
+        // Test distance stress centralities computation in g1_genesis wot
+        let distance_stress_centralities =
+            centralities_calculator.distance_stress_centralities(&wot3, 5);
+        assert_eq!(distance_stress_centralities.len(), 59);
+        assert_eq!(
+            distance_stress_centralities,
+            vec![
+                848, 240, 955, 80, 416, 203, 290, 645, 166, 908, 313, 231, 101, 202, 487, 769, 984,
+                0, 154, 534, 105, 697, 260, 700, 496, 1726, 711, 160, 217, 192, 89, 430, 636, 1276,
+                41, 420, 310, 0, 357, 125, 50, 15, 0, 12, 275, 170, 215, 1199, 0, 0, 0, 0, 201, 31,
+                0, 9, 55, 216, 865,
+            ]
+        );
     }
 }

wotb/operations/centrality.rs

@@ -25,9 +25,11 @@ pub trait CentralitiesCalculator<T: WebOfTrust> {
     fn betweenness_centralities(&self, wot: &T) -> Vec<u64>;
     /// Compute stress centrality of all members.
     fn stress_centralities(&self, wot: &T) -> Vec<u64>;
+    /// Compute distance stress centrality of all members.
+    fn distance_stress_centralities(&self, wot: &T, step_max: usize) -> Vec<u64>;
 }
 
-/// A new "rusty-er" implementation of `WoT` path finding.
+/// An implementation based on "Ulrik brandes" algo.
 #[derive(Debug, Clone, Copy)]
 pub struct UlrikBrandesCentralityCalculator;
 
@@ -138,4 +140,59 @@ impl<T: WebOfTrust> CentralitiesCalculator<T> for UlrikBrandesCentralityCalculat
         }
         centralities.into_iter().map(|c| c as u64).collect()
     }
+    fn distance_stress_centralities(&self, wot: &T, step_max: usize) -> Vec<u64> {
+        let wot_size = wot.size();
+        let mut centralities = vec![0.0; wot_size];
+        let enabled_nodes = wot.get_enabled();
+
+        // The source of any path belongs to enabled_nodes
+        for s in enabled_nodes.clone() {
+            let mut stack: Vec<NodeId> = Vec::with_capacity(wot_size);
+            let mut paths: HashMap<NodeId, Vec<NodeId>> = HashMap::with_capacity(wot_size);
+            let mut sigma = vec![0.0; wot_size];
+            let mut d: Vec<isize> = vec![-1; wot_size];
+            let mut q: VecDeque<NodeId> = VecDeque::with_capacity(wot_size);
+
+            sigma[s.0] = 1.0;
+            d[s.0] = 0;
+            q.push_back(s);
+            while !q.is_empty() {
+                let v = q.pop_front().unwrap();
+                stack.push(v);
+                if d[v.0] < step_max as isize {
+                    for w in wot.get_links_source(v).expect("v don't have any source !") {
+                        // w found for the first time ?
+                        if d[w.0] < 0 {
+                            q.push_back(w);
+                            d[w.0] = d[v.0] + 1;
+                        }
+                        // Shortest path to w via v
+                        if d[w.0] == d[v.0] + 1 {
+                            sigma[w.0] += sigma[v.0];
+                            paths.entry(w).or_insert_with(Vec::new).push(v);
+                        }
+                    }
+                }
+            }
+            let mut delta = vec![0.0; wot_size];
+            // stack returns vertices in order of non-increasing distance from s
+            while !stack.is_empty() {
+                let w = stack.pop().unwrap();
+                if paths.contains_key(&w) {
+                    for v in paths.get(&w).expect("Not found w in p !") {
+                        if enabled_nodes.contains(&w) {
+                            delta[v.0] += sigma[v.0] * (1.0 + (delta[w.0] / sigma[w.0]));
+                        } else {
+                            // If w not in enabled_nodes, no path can end at w
+                            delta[v.0] += sigma[v.0] * (delta[w.0] / sigma[w.0]);
+                        }
+                    }
+                }
+                if w != s {
+                    centralities[w.0] += delta[w.0];
+                }
+            }
+        }
+        centralities.into_iter().map(|c| c as u64).collect()
+    }
 }