/// <summary>
/// constructs a sub-tree
/// </summary>
/// <param name="graph"></param>
/// <param name="visitedEdges"></param>
/// <param name="startEdge"></param>
/// <returns></returns>
private MinimumSpanningTree <T> ConstructSubTree(FeatureGraph <T> graph,
HashSet <int> visitedEdges,
Edge <T> startEdge)
{
// Manages the tree being constructed.
var tree = new MinimumSpanningTree <T>();
// Manages the list of candidate edges
var tempEdges = new UniqueEdgeList <T>();
// Seed of the breadth first search (BFS)
tempEdges.AddEdge(startEdge);
// Start BFS
while (tempEdges.Count > 0)
{
// Sort the edges based on distace.
tempEdges.Sort();
Edge <T> shortestEdge = null;
var edgesToRemove = new List <Edge <T> >();
// Find the shortest edge...
foreach (var edge in tempEdges.Edges)
{
var edgeSeen = tree.HasEdgeBeenSeen(edge);
var vertexSeen = tree.HasEdgeVerticesBeenSeen(edge);
// Make sure that we havent seen this edge.
if (edgeSeen)
{
continue;
}
if (vertexSeen)
{
visitedEdges.Add(edge.ID);
edgesToRemove.Add(edge);
continue;
}
shortestEdge = edge;
tree.AddEdge(shortestEdge);
break;
}
// Remove any edges that have been used up..
edgesToRemove.ForEach(x => tempEdges.RemoveEdge(x));
edgesToRemove.ForEach(x => graph.RemoveEdge(x));
// We didnt find an edge, so we have nothing else to connect...
if (shortestEdge == null)
{
// Make sure that we assert that there are no edges left...should be the case here!
System.Diagnostics.Debug.Assert(tempEdges.Count == 0);
break;
}
visitedEdges.Add(shortestEdge.ID);
// Removes the shortest edge from the graph...
graph.RemoveEdge(shortestEdge);
var adjacentEdges = graph.GetAdjacentEdgesFromEdgeVertices(shortestEdge);
//adjacentEdges.Sort();
tempEdges.AddEdges(adjacentEdges.Edges);
// Remove the shortest edge from the list of available edges left...
tempEdges.RemoveEdge(shortestEdge);
}
return(tree);
}
/// <summary>
/// Creates clusters based on the MST's linear relationship made via construction. Cutoff is the score (length) per edge
/// that is allowed.
/// </summary>
/// <param name="mst">Minimum Spanning Tree</param>
/// <param name="cutoff">Cutoff score</param>
/// <returns>List of clusters</returns>
private List <U> CreateClusters(MinimumSpanningTree <T> mst, double cutoff)
{
var clusters = new List <U>();
if (mst.LinearRelationship.Count < 1)
{
return(clusters);
}
var currentCluster = new U();
var hashedFeatures = new HashSet <T>(); // Tracks the current feature
// These are the features that dont ever get included into a cluster...
// This can only happen if the MST building picked a bunch of low-life features that
// dont ever construct a graph...
var lowLifeFeatures = new List <T>();
for (var i = 0; i < mst.LinearRelationship.Count; i++)
{
// note this isnt O(n^2), this is just the search for a sub cluster
//
var currentEdge = mst.LinearRelationship[i];
var vertexA = currentEdge.VertexA;
var vertexB = currentEdge.VertexB;
var seenA = hashedFeatures.Contains(vertexA);
var seenB = hashedFeatures.Contains(vertexB);
if (currentEdge.Length < cutoff)
{
if (!seenA)
{
hashedFeatures.Add(vertexA);
currentCluster.AddChildFeature(vertexA);
}
if (!seenB)
{
hashedFeatures.Add(vertexB);
currentCluster.AddChildFeature(vertexB);
}
}
else
{
if (currentCluster.Features.Count > 0)
{
clusters.Add(currentCluster);
}
currentCluster = new U();
if (!seenA && !seenB)
{
// I DONT KNOW WHAT TO DO WITH THESE ASSHOLES!
lowLifeFeatures.Add(vertexA);
lowLifeFeatures.Add(vertexB);
// We dont hash these guys yet, because later we'll see if they hit the market
// with their fake DVD's
}
else if (!seenA)
{
currentCluster.AddChildFeature(vertexA);
hashedFeatures.Add(vertexA);
}
else
{
hashedFeatures.Add(vertexB);
currentCluster.AddChildFeature(vertexB);
}
}
}
// Make sure we add the current cluster if it's not full yet...
if (currentCluster.Features.Count > 0)
{
clusters.Add(currentCluster);
}
foreach (var lowLife in lowLifeFeatures)
{
if (!hashedFeatures.Contains(lowLife))
{
var cluster = new U();
cluster.AddChildFeature(lowLife);
clusters.Add(cluster);
}
}
return(clusters);
}
