public AbstractChooser(IndexGraph g) { this.G = g; this.LEFT = new ArrayList<IndexVertex>(); this.RIGHT = new HashSet<IndexVertex>(); this.N_LEFT = new HashSet<IndexVertex>(); this.N_v_RIGHT = new ArrayList<VSubSet>(G.numVertices()); this.UB = 2; IndexedSet<IndexVertex> groundSet; groundSet = new IndexedSet<IndexVertex>(G.vertices()); // degInLeft = new DegreeList(g); // System.out.println("Inside abstract class constructor"); for (IndexVertex v : G.vertices()) { RIGHT.add(v); } for (int i = 0; i < G.numVertices(); i++) N_v_RIGHT.add(new VSubSet(groundSet)); // create for all v in LEFT N(v) in RIGHT for (IndexVertex x : G.vertices()) { VSubSet temp = new VSubSet(groundSet); for (IndexVertex y : G.neighbours(x)) { if (RIGHT.contains(y)) temp.add(y); } // System.out.println("temp:"+temp); N_v_RIGHT.set(x.id(), temp); } }
public static int linIS(IndexGraph g, List<IndexVertex> order) { // sizes is a list which for each neighbourhood stores the optimal size of an independent Set // can easily be changed to store sets instead of sizes Map<VSubSet, Integer> sizes = new HashMap<VSubSet, Integer>(); // groundset is the vertices of the graph, solutions will be subsets of the groundset IndexedSet<IndexVertex> groundset = new IndexedSet<IndexVertex>(g.vertices()); // list of the neighbourhoods to the remaining part of the graph ArrayList<VSubSet> neighbours = new ArrayList<VSubSet>(g.numVertices()); for (int i = 0; i < g.numVertices(); i++) { VSubSet nset = new VSubSet(groundset); nset.addAll(g.neighbours(g.getVertex(i))); neighbours.add(nset); } // add the empty neighbourhood with size 0 sizes.put(new VSubSet(groundset), 0); // store the vertices you have seen so far (while you iterate through order) starting with an // empty set VSubSet seen = new VSubSet(groundset); // and the vertices you have not seen VSubSet unseen = new VSubSet(groundset); for (IndexVertex v : g.vertices()) unseen.add(v); // will store the optimal solution int maxIS = 0; int maxListSize = 0; // go through the vertices in the given order for (IndexVertex v : order) { maxListSize = Math.max(maxListSize, sizes.size()); // System.out.println("Considering: "+v); // System.out.println("The list has size: "+sizes.size()); // add v to the already seen vertices (left side of the cut) seen.add(v); unseen.remove(v); // update the neighbourhoods for (IndexVertex u : g.neighbours(v)) { neighbours.get(u.id()).remove(v); } // System.out.println("Have added "+v); // make a new map for the next cut (after v is moved from right to left) Map<VSubSet, Integer> newsizes = new HashMap<VSubSet, Integer>(); // go through all neighbourhoods for (Entry<VSubSet, Integer> e : sizes.entrySet()) { VSubSet set = e.getKey(); int size = e.getValue(); // If v is in the neighbourhood we can not add it to the Independent set, otherwise we may. if (set.contains(v)) { // update the size (This will never change maxIS and should be removed) maxIS = Math.max(maxIS, size); // remove v from the neighbourhood set.remove(v); // if the neighbourhood is already in the new list update, else add Integer temp = newsizes.get(set); if (temp == null || temp < size) newsizes.put(set, size); } else { Integer temp = newsizes.get(set); boolean usedSet = false; // If v has no neighbours in the set we can still keep the set as is without adding v if ((temp == null || temp < size) && neighbours.get(v.id()).intersects(unseen)) { usedSet = true; newsizes.put(set, size); } // make a copy of the Independent Set and increase the size of the solution (add v to the // solution) VSubSet newset; if (usedSet) newset = (VSubSet) set.clone(); else newset = set; size++; maxIS = Math.max(maxIS, size); // update the neighbourhood by adding the neighbours of v newset.AddAll(neighbours.get(v.id())); temp = newsizes.get(newset); // add the new set to the map if (temp == null || temp < size) newsizes.put(newset, size); } } // set the map to the one for the current cut sizes = newsizes; // for( Entry<VSubSet, Integer> set : newsizes.entrySet()) // System.out.println(set.getKey()+" of size "+set.getValue()); } System.out.println("Max list size used is: " + maxListSize); return maxIS; }