/// <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);
}