public IList <Cluster <TNode, double> > Solve([NotNull] IList <TNode> Nodes, [NotNull] CostAnalyzer <double> costanalyzer, double maxCostOfNearestNeighbor, int maxNodesPerCluster = -1)
{
var clusterFactory = new ClusterFactory(Nodes, costanalyzer);
var transposedCostMatrix = CostMatrix <double> .CreateTransposed(costanalyzer.CostMatrix);
var transposedCostanalyzer = new CostAnalyzer <double>(transposedCostMatrix);
// While unhandled indexes available and the loop runs for at most a certain amount of times, continue the algorithm
for (var counter = 0; counter < Nodes.Count * maxFactorOfLoopCount && clusterFactory.NodesAsIndexes.Count > 0; counter++)
{
// set the current pointer to a random node index among the nodes not yet classified in a cluster
int currentPointer = clusterFactory.NodesAsIndexes[randomizer.Next(0, clusterFactory.NodesAsIndexes.Count - 1)];
var candidateCluster = CalculateCluster(clusterFactory.NodesAsIndexes, costanalyzer, transposedCostanalyzer, maxCostOfNearestNeighbor, maxNodesPerCluster);
if (candidateCluster.Count > 1)
{
// loop over the cluster again maybe to cut the cluster in pieces. Clusters with one item are thrown back in the pool
for (int indexInCluster = 0; indexInCluster < candidateCluster.Count - 1; indexInCluster++)
{
var maxCostInCluster = indexInCluster == 0 ?
costanalyzer.AllNeighborsOrdered(candidateCluster[0])[candidateCluster[1]]
: candidateCluster.Take(indexInCluster + 1).Tuples().Max(t => costanalyzer.AllNeighborsOrdered(t.Item1)[t.Item2]);
var nodesOutsideClusterQuiteCloseToCluster = costanalyzer.AllNeighborsOrdered(candidateCluster[indexInCluster])
.Where(neighbor =>
!candidateCluster.Contains(neighbor.Key) && neighbor.Value <= maxCostInCluster);
if (nodesOutsideClusterQuiteCloseToCluster.Count() > 1) // Split the cluster
{
var firstPart = candidateCluster.GetRange(0, indexInCluster + 1);
clusterFactory.CreateCluster(firstPart);
candidateCluster.RemoveRange(0, indexInCluster + 1);
indexInCluster = -1;
}
}
}
clusterFactory.CreateCluster(candidateCluster);
}
// Here we add the singleton clusters from the remaining nodes
clusterFactory.CreateSingletonClusters();
return(clusterFactory.ListOfClusters);
}
public void CreateCluster(IList <int> clusterNodes)
{
if (clusterNodes.Count > 1) // don't add singleton clusters here
{
double costOfCluster = clusterNodes.Tuples().Sum(t => costanalyzer.AllNeighborsOrdered(t.Item1)[t.Item2]);
double reverseCost = clusterNodes.Reverse().Tuples().Sum(n => costanalyzer.AllNeighborsOrdered(n.Item1)[n.Item2]);
foreach (var j in clusterNodes)
{
NodesAsIndexes.Remove(j); // accepted as final member of the cluster
}
ListOfClusters.Add(new Cluster <TNode, double>(clusterNodes.Select(n => allNodes[n]), costOfCluster, reverseCost));
}
}
private static void ExpandClusterFromStartPoint(int startIndex, List <int> constructingCluster, bool atTail, IList <int> nodesAsIndexes, CostAnalyzer <double> costanalyzer, double maxCostOfNearestNeighbor, int maxNodesPerCluster)
{
int currentPointer = startIndex;
bool foundNextNodeInChain;
if (maxNodesPerCluster < 0 || constructingCluster.Count < maxNodesPerCluster - 1)
{
do
{
foundNextNodeInChain = false;
var myNeighborsNotAlreadyInConstructingCluster =
costanalyzer.AllNeighborsOrdered(currentPointer).Where(neighbor => currentPointer != neighbor.Key && !constructingCluster.Contains(neighbor.Key));
if (myNeighborsNotAlreadyInConstructingCluster.Any())
{
var nearestNeighbor = myNeighborsNotAlreadyInConstructingCluster.FirstOrDefault(); // The closest neighbor
if (nearestNeighbor.Value <= maxCostOfNearestNeighbor &&
nodesAsIndexes.Contains(nearestNeighbor.Key)) // No overlapping with other clusters. We stop if the next one is in another cluster.
{
if (constructingCluster.Count == 0)
{
constructingCluster.Add(currentPointer); // If we start construct a cluster don't forget to add the beginning node.
}
if (atTail)
{
constructingCluster.Add(nearestNeighbor.Key);
}
else
{
constructingCluster.Insert(0, nearestNeighbor.Key);
}
currentPointer = nearestNeighbor.Key; // Move the pointer to the neighbor
foundNextNodeInChain = true;
}
}
}while (foundNextNodeInChain && (maxNodesPerCluster < 0 || constructingCluster.Count < maxNodesPerCluster));
}
}
