private void EnqueueFirstShortestPath(
IQueue <DeviationPath> queue,
IDictionary <TVertex, TEdge> successors,
IDictionary <TVertex, double> distances,
TVertex root)
{
Contract.Requires(queue != null);
Contract.Requires(queue.Count == 0);
Contract.Requires(successors != null);
Contract.Requires(distances != null);
Contract.Requires(root != null);
var path = new List <TEdge>();
AppendShortestPath(
path,
successors,
root);
if (path.Count == 0)
{
return; // unreachable vertices
}
if (!EdgeExtensions.HasCycles <TVertex, TEdge>(path))
{
this.AddComputedShortestPath(path);
}
// create deviation paths
this.EnqueueDeviationPaths(
queue,
root,
distances,
path.ToArray(),
0);
}
protected override void InternalCompute()
{
var cancelManager = this.Services.CancelManager;
TVertex root;
if (!this.TryGetRootVertex(out root))
{
throw new InvalidOperationException("root vertex not set");
}
TVertex goal;
if (!this.TryGetGoalVertex(out goal))
{
throw new InvalidOperationException("goal vertex not set");
}
// start by building the minimum tree starting from the goal vertex.
IDictionary <TVertex, TEdge> successors;
IDictionary <TVertex, double> distances;
this.ComputeMinimumTree(goal, out successors, out distances);
if (cancelManager.IsCancelling)
{
return;
}
var queue = new FibonacciQueue <DeviationPath, double>(dp => dp.Weight);
var vertexCount = this.VisitedGraph.VertexCount;
// first shortest path
this.EnqueueFirstShortestPath(queue, successors, distances, root);
while (queue.Count > 0 &&
this.ComputedShortestPathCount < this.ShortestPathCount)
{
if (cancelManager.IsCancelling)
{
return;
}
var deviation = queue.Dequeue();
// turn into path
var path = new List <TEdge>();
for (int i = 0; i < deviation.DeviationIndex; ++i)
{
path.Add(deviation.ParentPath[i]);
}
path.Add(deviation.DeviationEdge);
int startEdge = path.Count;
this.AppendShortestPath(path, successors, deviation.DeviationEdge.Target);
Contract.Assert(deviation.Weight == Enumerable.Sum(path, e => edgeWeights(e)));
Contract.Assert(path.Count > 0);
// add to list if loopless
if (!EdgeExtensions.HasCycles <TVertex, TEdge>(path))
{
this.AddComputedShortestPath(path);
}
// append new deviation paths
if (path.Count < vertexCount)
{
this.EnqueueDeviationPaths(
queue,
root,
successors,
distances,
path.ToArray(),
startEdge
);
}
}
}
