/// <summary>
/// Adds a new settled vertex.
/// </summary>
public static uint AddSettledVertex(this PathTree tree, uint vertex, WeightAndDir <float> weightAndDir, uint hops, uint pPointer)
{
var hopsAndDirection = hops * 4 + weightAndDir.Direction._val;
return(tree.Add(vertex, (uint)(weightAndDir.Weight * WeightFactor),
hopsAndDirection, pPointer));
}
/// <summary>
/// Gets a settled vertex.
/// </summary>
public static void GetSettledVertex(this PathTree tree, uint pointer, out uint vertex,
out WeightAndDir <float> weightAndDir, out uint hops)
{
uint data0, data1, data2;
tree.Get(pointer, out data0, out data1, out data2);
vertex = data0;
weightAndDir = new WeightAndDir <float>()
{
Weight = data1 / WeightFactor,
Direction = new Dir()
{
_val = (byte)(data2 & 3)
}
};
hops = data2 / 4;
}
/// <summary>
/// Calculates witness paths.
/// </summary>
public virtual void Calculate(DirectedGraph graph, WeightHandler <T> weightHandler, uint vertex,
uint source, Dictionary <uint, Shortcut <T> > targets, int maxSettles, int hopLimit)
{
pathTree.Clear();
pointerHeap.Clear();
var forwardSettled = new HashSet <uint>();
var backwardSettled = new HashSet <uint>();
var forwardTargets = new HashSet <uint>();
var backwardTargets = new HashSet <uint>();
var maxWeight = 0f;
foreach (var targetPair in targets)
{
var target = targetPair.Key;
var shortcut = targetPair.Value;
var e = new OriginalEdge(source, target);
var shortcutForward = weightHandler.GetMetric(shortcut.Forward);
if (shortcutForward > 0 && shortcutForward < float.MaxValue)
{
forwardTargets.Add(e.Vertex2);
if (shortcutForward > maxWeight)
{
maxWeight = shortcutForward;
}
}
var shortcutBackward = weightHandler.GetMetric(shortcut.Backward);
if (shortcutBackward > 0 && shortcutBackward < float.MaxValue)
{
backwardTargets.Add(e.Vertex2);
if (shortcutBackward > maxWeight)
{
maxWeight = shortcutBackward;
}
}
}
// queue the source.
pathTree.Clear();
pointerHeap.Clear();
var p = pathTree.AddSettledVertex(source, new WeightAndDir <float>()
{
Direction = new Dir(true, true),
Weight = 0
}, 0);
pointerHeap.Push(p, 0);
// dequeue vertices until stopping conditions are reached.
var cVertex = Constants.NO_VERTEX;
WeightAndDir <float> cWeight;
var cHops = uint.MaxValue;
var enumerator = graph.GetEdgeEnumerator();
while (pointerHeap.Count > 0)
{
var cPointer = pointerHeap.Pop();
pathTree.GetSettledVertex(cPointer, out cVertex, out cWeight, out cHops);
if (cVertex == vertex)
{
continue;
}
if (cWeight.Weight >= maxWeight)
{
break;
}
if (forwardSettled.Contains(cVertex) ||
forwardTargets.Count == 0 ||
forwardSettled.Count > maxSettles)
{
cWeight.Direction = new Dir(false, cWeight.Direction.B);
}
if (backwardSettled.Contains(cVertex) ||
backwardTargets.Count == 0 ||
backwardSettled.Count > maxSettles)
{
cWeight.Direction = new Dir(cWeight.Direction.F, false);
}
if (cWeight.Direction.F)
{
forwardSettled.Add(cVertex);
if (forwardTargets.Contains(cVertex))
{ // target reached, evaluate it as a shortcut.
Shortcut <T> shortcut;
if (targets.TryGetValue(cVertex, out shortcut))
{
var shortcutForward = weightHandler.GetMetric(shortcut.Forward);
if (shortcutForward > cWeight.Weight)
{ // a witness path was found, don't add a shortcut.
shortcut.Forward = weightHandler.Zero;
targets[cVertex] = shortcut;
}
}
forwardTargets.Remove(cVertex);
if (forwardTargets.Count == 0)
{
if (backwardTargets.Count == 0)
{
break;
}
cWeight.Direction = new Dir(false, cWeight.Direction.B);
if (!cWeight.Direction.F && !cWeight.Direction.B)
{
continue;
}
}
}
}
if (cWeight.Direction.B)
{
backwardSettled.Add(cVertex);
if (backwardTargets.Contains(cVertex))
{ // target reached, evaluate it as a shortcut.
Shortcut <T> shortcut;
if (targets.TryGetValue(cVertex, out shortcut))
{
var shortcutBackward = weightHandler.GetMetric(shortcut.Backward);
if (shortcutBackward > cWeight.Weight)
{ // a witness path was found, don't add a shortcut.
shortcut.Backward = weightHandler.Zero;
targets[cVertex] = shortcut;
}
}
backwardTargets.Remove(cVertex);
if (backwardTargets.Count == 0)
{
if (forwardTargets.Count == 0)
{
break;
}
cWeight.Direction = new Dir(cWeight.Direction.F, false);
if (!cWeight.Direction.F && !cWeight.Direction.B)
{
continue;
}
}
}
}
if (cHops + 1 >= hopLimit)
{
continue;
}
if (forwardSettled.Count > maxSettles &&
backwardSettled.Count > maxSettles)
{
continue;
}
enumerator.MoveTo(cVertex);
while (enumerator.MoveNext())
{
var nVertex = enumerator.Neighbour;
var nWeight = ContractedEdgeDataSerializer.Deserialize(enumerator.Data0);
nWeight = new WeightAndDir <float>()
{
Direction = Dir.Combine(cWeight.Direction, nWeight.Direction),
Weight = cWeight.Weight + nWeight.Weight
};
if (nWeight.Direction.F &&
forwardSettled.Contains(nVertex))
{
nWeight.Direction = new Dir(false, nWeight.Direction.B);
}
if (nWeight.Direction.B &&
backwardSettled.Contains(nVertex))
{
nWeight.Direction = new Dir(nWeight.Direction.F, false);
}
if (!nWeight.Direction.F && !nWeight.Direction.B)
{
continue;
}
var nPoiner = pathTree.AddSettledVertex(nVertex, nWeight, cHops + 1);
pointerHeap.Push(nPoiner, nWeight.Weight);
}
}
}
