/// <summary>
/// Compute the transitive closure and store it in the supplied graph 'tc'
/// </summary>
/// <param name="tc">
/// Mutable Graph instance to store the transitive closure
/// </param>
/// <exception cref="ArgumentNullException">
/// <paramref name="tc"/> is a <null/>.
/// </exception>
public void Create(IMutableVertexAndEdgeListGraph tc)
{
if (tc == null)
{
throw new ArgumentNullException("tc");
}
CondensationGraphAlgorithm cgalgo = new CondensationGraphAlgorithm(VisitedGraph);
cgalgo.Create(cg);
ArrayList topo_order = new ArrayList(cg.VerticesCount);
TopologicalSortAlgorithm topo = new TopologicalSortAlgorithm(cg, topo_order);
topo.Compute();
VertexIntDictionary in_a_chain = new VertexIntDictionary();
VertexIntDictionary topo_number = new VertexIntDictionary();
for (int order = 0; order < topo_order.Count; order++)
{
IVertex v = (IVertex)topo_order[order];
topo_number.Add(v, order);
if (!in_a_chain.Contains(v)) // Initially no vertex is present in a chain
{
in_a_chain.Add(v, 0);
}
}
VertexListMatrix chains = new VertexListMatrix();
int position = -1;
foreach (IVertex v in topo_order)
{
if (in_a_chain[v] == 0)
{
// Start a new chain
position = chains.AddRow();
IVertex next = v;
for (;;)
{
chains[position].Add(next);
in_a_chain[next] = 1;
// Get adjacent vertices ordered by topological number
// Extend the chain by choosing the adj vertex with lowest topo#
ArrayList adj = TopoSortAdjVertices(next, cg, topo_number);
if ((next = FirstNotInChain(adj, in_a_chain)) == null)
{
break;
}
}
}
}
VertexIntDictionary chain_number = new VertexIntDictionary();
VertexIntDictionary pos_in_chain = new VertexIntDictionary();
// Record chain positions of vertices
SetChainPositions(chains, chain_number, pos_in_chain);
VertexListMatrix successors = new VertexListMatrix();
successors.CreateObjectMatrix(cg.VerticesCount, chains.RowCount, int.MaxValue);
if (topo_order.Count > 0)
{
for (int rtopo = topo_order.Count - 1; rtopo > -1; rtopo--)
{
IVertex u = (IVertex)topo_order[rtopo];
foreach (IVertex v in TopoSortAdjVertices(u, cg, topo_number))
{
if (topo_number[v] < (int)successors[u.ID][chain_number[v]])
{
// {succ(u)} = {succ(u)} U {succ(v)}
LeftUnion(successors[u.ID], successors[v.ID]);
// {succ(u)} = {succ(u)} U {v}
successors[u.ID][chain_number[v]] = topo_number[v];
}
}
}
}
// Create transitive closure of condensation graph
// Remove existing edges in CG & rebuild edges for TC from
// successor set (to avoid duplicating parallel edges)
ArrayList edges = new ArrayList();
foreach (IEdge e in cg.Edges)
{
edges.Add(e);
}
foreach (IEdge e in edges)
{
cg.RemoveEdge(e);
}
foreach (IVertex u in cg.Vertices)
{
int i = u.ID;
for (int j = 0; j < chains.RowCount; j++)
{
int tnumber = (int)successors[i][j];
if (tnumber < int.MaxValue)
{
IVertex v = (IVertex)topo_order[tnumber];
for (int k = pos_in_chain[v]; k < chains[j].Count; k++)
{
cg.AddEdge(u, (IVertex)chains[j][k]);
}
}
}
}
// Maps a vertex in input graph to it's transitive closure graph
graphTransitiveClosures = new VertexVertexDictionary();
// Add vertices to transitive closure graph
foreach (IVertex v in visitedGraph.Vertices)
{
if (!graphTransitiveClosures.Contains(v))
{
IVertex vTransform = tc.AddVertex();
OnInitTransitiveClosureVertex(
new TransitiveClosureVertexEventArgs(
v, vTransform)
);
// Fire the TC Vertex Event
graphTransitiveClosures.Add(v, vTransform);
}
}
//Add edges connecting vertices within SCC & adjacent
// SCC (strongly connected component)
IVertexCollection scc_vertices = null;
foreach (IVertex s_tccg in cg.Vertices)
{
scc_vertices = (IVertexCollection)cgalgo.SCCVerticesMap[s_tccg.ID];
if (scc_vertices.Count > 1)
{
foreach (IVertex u in scc_vertices)
{
foreach (IVertex v in scc_vertices)
{
OnExamineEdge(tc.AddEdge(graphTransitiveClosures[u], graphTransitiveClosures[v]));
}
}
}
foreach (IEdge adj_edge in cg.OutEdges(s_tccg))
{
IVertex t_tccg = adj_edge.Target;
foreach (IVertex s in (IVertexCollection)cgalgo.SCCVerticesMap[s_tccg.ID])
{
foreach (IVertex t in (IVertexCollection)cgalgo.SCCVerticesMap[t_tccg.ID])
{
OnExamineEdge(tc.AddEdge(graphTransitiveClosures[s], graphTransitiveClosures[t]));
}
}
}
}
}
