protected override int ExecuteTest()
{
if (NodeStates.FixedTargetNodeCount <= 1 || NodeStates.VariableTargetNodeCount > 0)
{
return(0);
}
var removedNodes = 0;
var mst = new MinimalSpanningTree(NodeStates.FixedTargetNodeIndices.ToList(), DistanceLookup);
mst.Span(StartNodeIndex);
var maxEdgeDistance = mst.SpanningEdges.Max(e => e.Priority);
for (var i = 0; i < SearchSpaceSize; i++)
{
if (NodeStates.IsTarget(i) || NodeStates.IsRemoved(i))
{
continue;
}
// Theoretically, this can be sped up by using Voronoi partitions. The Voronoi base of i is the
// terminal with the smallest distance to i by definition, so only the distance to that terminal
// has to be checked.
if (NodeStates.FixedTargetNodeIndices.All(t => DistanceLookup[i, t] >= maxEdgeDistance))
{
EdgeSet.EdgesOf(i).ForEach(EdgeSet.Remove);
NodeStates.MarkNodeAsRemoved(i);
removedNodes++;
}
}
return(removedNodes);
}
/// <summary>
/// Removes all nodes that were marked as removed from the search space and updates the distance lookup and the edge set.
/// </summary>
private void ContractSearchSpace()
{
var distanceLookup = _data.DistanceLookup;
// Save all edges by the GraphNodes they are connecting. (the indices are worthless after the search space is contracted)
var edges =
_data.EdgeSet.Select(
e => Tuple.Create(distanceLookup.IndexToNode(e.N1), distanceLookup.IndexToNode(e.N2), e.Weight))
.ToList();
// Contract the search space and update _distanceLookup.
_nodeStates.SearchSpace = distanceLookup.RemoveNodes(_nodeStates.SearchSpace.Where(n => _nodeStates.IsRemoved(n.DistancesIndex)));
// Add all edges back.
_data.EdgeSet = new GraphEdgeSet(distanceLookup.CacheSize);
foreach (var tuple in edges)
{
_data.EdgeSet.Add(tuple.Item1.DistancesIndex, tuple.Item2.DistancesIndex, tuple.Item3);
}
}