/// <inheritdoc />
protected override void InternalCompute()
{
// Adding vertices to the new graph
// and pushing filtered vertices in queue
var filteredVertices = new Queue <TVertex>();
foreach (TVertex vertex in VisitedGraph.Vertices)
{
CondensedGraph.AddVertex(vertex);
if (!VertexPredicate(vertex))
{
filteredVertices.Enqueue(vertex);
}
}
// Adding all edges
foreach (TEdge edge in VisitedGraph.Edges)
{
var mergedEdge = new MergedEdge <TVertex, TEdge>(edge.Source, edge.Target);
mergedEdge.Edges.Add(edge);
CondensedGraph.AddEdge(mergedEdge);
}
// Remove vertices
while (filteredVertices.Count > 0)
{
TVertex filteredVertex = filteredVertices.Dequeue();
// Do the cross product between in-edges and out-edges
MergeVertex(filteredVertex);
}
}
private void MergeVertex([NotNull] TVertex vertex)
{
Debug.Assert(vertex != null);
// Get in-edges and out-edges
var inEdges = new List <MergedEdge <TVertex, TEdge> >(CondensedGraph.InEdges(vertex));
var outEdges = new List <MergedEdge <TVertex, TEdge> >(CondensedGraph.OutEdges(vertex));
// Remove vertex
CondensedGraph.RemoveVertex(vertex);
// Add condensed edges
foreach (MergedEdge <TVertex, TEdge> inEdge in inEdges)
{
if (EqualityComparer <TVertex> .Default.Equals(inEdge.Source, vertex))
{
continue;
}
foreach (MergedEdge <TVertex, TEdge> outEdge in outEdges)
{
if (EqualityComparer <TVertex> .Default.Equals(outEdge.Target, vertex))
{
continue;
}
var newEdge = MergedEdge <TVertex, TEdge> .Merge(inEdge, outEdge);
CondensedGraph.AddEdge(newEdge);
}
}
}
/// <summary>
/// Merges the given two edges.
/// </summary>
/// <param name="inEdge">First edge.</param>
/// <param name="outEdge">Second edge.</param>
/// <returns>The merged edge.</returns>
public static MergedEdge <TVertex, TEdge> Merge(
MergedEdge <TVertex, TEdge> inEdge,
MergedEdge <TVertex, TEdge> outEdge)
{
if (inEdge is null)
{
throw new ArgumentNullException(nameof(inEdge));
}
if (outEdge is null)
{
throw new ArgumentNullException(nameof(outEdge));
}
var newEdge = new MergedEdge <TVertex, TEdge>(inEdge.Source, outEdge.Target)
{
_edges = new List <TEdge>(inEdge.Edges.Count + outEdge.Edges.Count)
};
newEdge._edges.AddRange(inEdge._edges);
newEdge._edges.AddRange(outEdge._edges);
return(newEdge);
}