UndirectedGraph::contractions: take edge orbits as input

src/main.rs

@@ -11,8 +11,8 @@ fn main() {
     println!("normal_g.expanding_differential(&orbits) = {:?}", normal_g.expanding_differential(&orbits));
     println!("normal_g.contractions() = {:?}", normal_g.contractions(&vec![0_usize]));
     let h: UndirectedGraph = UndirectedGraph::new(7,vec![(0, 1), (0, 2), (0, 6), (1, 4), (1, 6), (2, 5), (2, 6), (3, 4), (3, 5), (3, 6), (4, 5)]);
-    let edge_orbit_reps_h: Vec<usize> = vec![0, 2, 3, 4, 7, 9, 10];
-    println!("normal_h.contractions(&edge_orbits_h) = {:?}", h.contractions(&edge_orbit_reps_h));
+    let edge_orbits_h: Vec<usize> = vec![0, 0, 2, 3, 4, 3, 4, 10, 7, 7, 9];
+    println!("normal_h.contractions(&edge_orbits_h) = {:?}", h.contractions(&edge_orbits_h));
     let triangle: UndirectedGraph = UndirectedGraph::new(3, vec![(0,1), (1,2), (0,2)]);
     println!("triangle.normal_form() = {:?}", triangle.normal_form(true));
     println!("triangle.contractions() = {:?}", triangle.contractions(&vec![0_usize]));

src/undirected_graph.rs

@@ -324,11 +324,16 @@ impl UndirectedGraph {
 
     pub fn contractions(
         &self,
-        edge_orbit_reps: &Vec<usize>,
+        edge_orbits: &Vec<usize>,
     ) -> HashMap<UndirectedGraph, HashMap<usize, usize>> {
         // TODO: Check that passing around hashmaps is not too expensive.
         let mut contractions: HashMap<UndirectedGraph, HashMap<usize, usize>> = HashMap::new();
-        for &edge_orbit_rep in edge_orbit_reps {
+        let mut edge_orbit_reps: HashSet<usize> = HashSet::new();
+        for &edge_orbit_rep in edge_orbits {
+            // Skip orbits already seen.
+            if !edge_orbit_reps.insert(edge_orbit_rep) {
+                continue;
+            }
             let edge: (usize, usize) = self.edges[edge_orbit_rep];
             // TODO: Optimize the computation of new_edges.
             let mut new_edges: Vec<(usize, usize)> = self.edges.clone();