/// <summary> /// Computes the maximum flow between <paramref name="src"/> and /// <paramref name="sink"/> /// </summary> /// <param name="src"></param> /// <param name="sink"></param> /// <returns></returns> public override double Compute(IVertex src, IVertex sink) { if (src == null) { throw new ArgumentNullException("src"); } if (sink == null) { throw new ArgumentNullException("sink"); } foreach (IVertex u in VisitedGraph.Vertices) { foreach (IEdge e in VisitedGraph.OutEdges(u)) { ResidualCapacities[e] = Capacities[e]; } } Colors[sink] = GraphColor.Gray; while (Colors[sink] != GraphColor.White) { PredecessorRecorderVisitor vis = new PredecessorRecorderVisitor( Predecessors ); VertexBuffer Q = new VertexBuffer(); BreadthFirstSearchAlgorithm bfs = new BreadthFirstSearchAlgorithm( ResidualGraph, Q, Colors ); bfs.RegisterPredecessorRecorderHandlers(vis); bfs.Compute(src); if (Colors[sink] != GraphColor.White) { Augment(src, sink); } } // while double flow = 0; foreach (IEdge e in VisitedGraph.OutEdges(src)) { flow += (Capacities[e] - ResidualCapacities[e]); } return(flow); }
/// <summary> /// Computes a set of eulerian trail, starting at <paramref name="s"/> /// that spans the entire graph. /// </summary> /// <remarks> /// <para> /// This method computes a set of eulerian trail starting at <paramref name="s"/> /// that spans the entire graph.The algorithm outline is as follows: /// </para> /// <para> /// The algorithms iterates throught the Eulerian circuit of the augmented /// graph (the augmented graph is the graph with additional edges to make /// the number of odd vertices even). /// </para> /// <para> /// If the current edge is not temporary, it is added to the current trail. /// </para> /// <para> /// If the current edge is temporary, the current trail is finished and /// added to the trail collection. The shortest path between the /// start vertex <paramref name="s"/> and the target vertex of the /// temporary edge is then used to start the new trail. This shortest /// path is computed using the <see cref="BreadthFirstSearchAlgorithm"/>. /// </para> /// </remarks> /// <param name="s">start vertex</param> /// <returns>eulerian trail set, all starting at s</returns> /// <exception cref="ArgumentNullException">s is a null reference.</exception> /// <exception cref="Exception">Eulerian trail not computed yet.</exception> public EdgeCollectionCollection Trails(IVertex s) { if (s == null) { throw new ArgumentNullException("s"); } if (this.Circuit.Count == 0) { throw new Exception("Circuit is empty"); } // find the first edge in the circuit. int i = 0; for (i = 0; i < this.Circuit.Count; ++i) { IEdge e = this.Circuit[i]; if (TemporaryEdges.Contains(e)) { continue; } if (e.Source == s) { break; } } if (i == this.Circuit.Count) { throw new Exception("Did not find vertex in eulerian trail?"); } // create collections EdgeCollectionCollection trails = new EdgeCollectionCollection(); EdgeCollection trail = new EdgeCollection(); BreadthFirstSearchAlgorithm bfs = new BreadthFirstSearchAlgorithm(VisitedGraph); PredecessorRecorderVisitor vis = new PredecessorRecorderVisitor(); bfs.RegisterPredecessorRecorderHandlers(vis); bfs.Compute(s); // go throught the edges and build the predecessor table. int start = i; for (; i < this.Circuit.Count; ++i) { IEdge e = this.Circuit[i]; if (TemporaryEdges.Contains(e)) { // store previous trail and start new one. if (trail.Count != 0) { trails.Add(trail); } // start new trail // take the shortest path from the start vertex to // the target vertex trail = vis.Path(e.Target); } else { trail.Add(e); } } // starting again on the circuit for (i = 0; i < start; ++i) { IEdge e = this.Circuit[i]; if (TemporaryEdges.Contains(e)) { // store previous trail and start new one. if (trail.Count != 0) { trails.Add(trail); } // start new trail // take the shortest path from the start vertex to // the target vertex trail = vis.Path(e.Target); } else { trail.Add(e); } } // adding the last element if (trail.Count != 0) { trails.Add(trail); } return(trails); }