//Stacked MST
public static LightWeightGraph GetStackedMST(DistanceMatrix distances, int numMSTs)
{
int numNodes = distances.Count;
//in a complete graph, there are n*(n-1)/2 edges
//an MST contains n-1 edges
//number of msts is n/2
if (numMSTs > numNodes / 2)
{
numMSTs = numNodes / 2;
}
LightWeightNode[] nodes = new LightWeightNode[numNodes];
List <int>[] edges = new List <int> [numNodes];
List <double>[] weights = new List <double> [numNodes];
//List<double>[] edgeWeights = new List<double>[numNodes];
for (int i = 0; i < numNodes; i++)
{
edges[i] = new List <int>();
weights[i] = new List <double>();
}
//Add all of the distances to the Heap
List <distXY> points = new List <distXY>();
for (int x = 0; x < numNodes - 1; x++)
{
for (int y = x + 1; y < numNodes; y++)
{
points.Add(new distXY(x, y, distances[x, y]));
}
}
//Now we need to start making our MST
for (int n = 0; n < numMSTs; n++)
{
MinHeapPriorityQueue <distXY> minheap = new MinHeapPriorityQueue <distXY>(((x, y) => x.Dist > y.Dist));
minheap.addAll(points);
DisjointSet ds = new DisjointSet(numNodes);
int k = 0;
while (k < numNodes - 1)
{
distXY e = minheap.extractMin();
if (ds.diff(e.X, e.Y)) //different
{
ds.union(e.X, e.Y);
//change the dist
e.Dist = double.MaxValue;
//Add it
edges[e.X].Add(e.Y);
edges[e.Y].Add(e.X);
weights[e.X].Add(distances[e.X, e.Y]);
weights[e.Y].Add(distances[e.X, e.Y]);
k++;
}
}
}
for (int i = 0; i < numNodes; i++)
{
nodes[i] = new LightWeightNode(i, true, edges[i], weights[i]);
}
return(new LightWeightGraph(nodes, true));
}
//Knn based
public static LightWeightGraph GetKNNGraph(DistanceMatrix distances, int numNeighbors)
{
int numNodes = distances.Count;
var nodes = new LightWeightNode[numNodes];
List <int>[] edgeLists = new List <int> [numNodes];
List <double>[] edgeWeights = new List <double> [numNodes];
for (int i = 0; i < numNodes; i++)
{
edgeLists[i] = new List <int>();
edgeWeights[i] = new List <double>();
}
//prevent redundant edges
HashSet <Tuple <int, int> > addedEdges = new HashSet <Tuple <int, int> >();
//Our comparator
MinHeapPriorityQueue <Tuple <int, double> > .isGreaterThan comp =
new MinHeapPriorityQueue <Tuple <int, double> > .isGreaterThan((x, y) => { return(x.Item2 > y.Item2); });
//Add Edges
for (int i = 0; i < numNodes; i++)
{
//get list of edges
List <Tuple <int, double> > edges = new List <Tuple <int, double> >();
for (int j = 0; j < numNodes; j++)
{
//Make sure we don't load our heap with repeated edges
if (i != j)
{
edges.Add(new Tuple <int, double>(j, distances[i, j]));
}
}
//Build the heap
MinHeapPriorityQueue <Tuple <int, double> > heap = new MinHeapPriorityQueue <Tuple <int, double> >(comp);
heap.addAll(edges);
//Now add all of the neighbors
for (int edgeNum = 0; edgeNum < numNeighbors; edgeNum++)
{
if (heap.isEmpty())
{
break;
}
Tuple <int, double> e = heap.extractMin();
Tuple <int, int> edgeNodePair = (e.Item1 < i)
? new Tuple <int, int>(e.Item1, i)
: new Tuple <int, int>(i, e.Item1);
//if (!addedEdges.Contains(edgeNodePair))
if (!addedEdges.Contains(edgeNodePair))
{
//make sure we don't add this edge again in the future
//addedEdges.Add(edgeNodePair);
addedEdges.Add(edgeNodePair);
//Add the double edge now
edgeLists[i].Add(e.Item1);
edgeLists[e.Item1].Add(i);
edgeWeights[i].Add((double)e.Item2);
edgeWeights[e.Item1].Add((double)e.Item2);
}
}
}
for (int i = 0; i < numNodes; i++)
{
nodes[i] = new LightWeightNode(i, true, edgeLists[i], edgeWeights[i]);
}
return(new LightWeightGraph(nodes, true));
}
public LightWeightGraph GetLOOGraph(DistanceMatrix distances, int numNeighbors, bool[] exclusion = null, int numToLeaveOut = 0)
{
int numNodes = distances.Count;
var nodes = new LightWeightGraph.LightWeightNode[numNodes];
List <int>[] edgeLists = new List <int> [numNodes];
List <double>[] edgeWeights = new List <double> [numNodes];
for (int i = 0; i < numNodes; i++)
{
edgeLists[i] = new List <int>();
edgeWeights[i] = new List <double>();
}
//prevent redundant edges
HashSet <Tuple <int, int> > addedEdges = new HashSet <Tuple <int, int> >();
//Our comparator
MinHeapPriorityQueue <Tuple <int, double> > .isGreaterThan comp = ((x, y) => x.Item2 > y.Item2);
//Deal with _skipLast Choice
int lastNeighbor = (_skipLast) ? numNodes - 1 : numNodes;
//Add Edges
for (int i = 0; i < lastNeighbor; i++)
{
if (exclusion != null && exclusion[i])
{
continue;
}
// Deal with the leave one out
double probability = (double)numToLeaveOut / numNodes;
double rollDie = rnd.NextDouble();
if (rollDie < probability)
{
//Console.WriteLine("Skipped Node " + i);
_numLeftOut++;
continue;
}
//get list of edges
List <Tuple <int, double> > edges = new List <Tuple <int, double> >();
for (int j = 0; j < numNodes; j++)
{
//Make sure we don't load our heap with repeated edges
if (i != j)
{
edges.Add(new Tuple <int, double>(j, distances[i, j]));
}
}
//Build the heap
MinHeapPriorityQueue <Tuple <int, double> > heap = new MinHeapPriorityQueue <Tuple <int, double> >(comp);
heap.addAll(edges);
//Now add all of the neighbors
for (int edgeNum = 0; edgeNum < numNeighbors; edgeNum++)
{
if (heap.isEmpty())
{
break;
}
Tuple <int, double> e = heap.extractMin();
Tuple <int, int> edgeNodePair = (e.Item1 < i)
? new Tuple <int, int>(e.Item1, i)
: new Tuple <int, int>(i, e.Item1);
//if (!addedEdges.Contains(edgeNodePair))
if (!addedEdges.Contains(edgeNodePair))
{
//make sure we don't add this edge again in the future
//addedEdges.Add(edgeNodePair);
addedEdges.Add(edgeNodePair);
//Add the double edge now
edgeLists[i].Add(e.Item1);
edgeLists[e.Item1].Add(i);
edgeWeights[i].Add((double)e.Item2);
edgeWeights[e.Item1].Add((double)e.Item2);
}
}
}
for (int i = 0; i < numNodes; i++)
{
nodes[i] = new LightWeightGraph.LightWeightNode(i, true, edgeLists[i], edgeWeights[i]);
}
return(new LightWeightGraph(nodes, true));
}
