private void Run()
{
Forest.Clear();
PriorityQueue <Node, TCost> priorityQueue = new PriorityQueue <Node, TCost>();
HashSet <Node> processed = new HashSet <Node>();
Dictionary <Node, Arc> parentArc = new Dictionary <Node, Arc>();
// start with one point from each component
var components = new ConnectedComponents(Graph, ConnectedComponents.Flags.CreateComponents);
foreach (var c in components.Components)
{
Node root = c.First();
processed.Add(root);
foreach (var arc in Graph.Arcs(root))
{
Node v = Graph.Other(arc, root);
parentArc[v] = arc;
priorityQueue[v] = Cost(arc);
}
}
components = null;
while (priorityQueue.Count != 0)
{
Node n = priorityQueue.Peek();
priorityQueue.Pop();
processed.Add(n);
Arc arcToAdd = parentArc[n];
Forest.Add(arcToAdd);
ForestGraph.Enable(arcToAdd, true);
foreach (var arc in Graph.Arcs(n))
{
Node v = Graph.Other(arc, n);
if (processed.Contains(v))
{
continue;
}
TCost arcCost = Cost(arc);
TCost vCost;
bool vInPriorityQueue = priorityQueue.TryGetPriority(v, out vCost);
if (!vInPriorityQueue || arcCost.CompareTo(vCost) < 0)
{
priorityQueue[v] = arcCost;
parentArc[v] = arc;
}
}
}
}
private void Run()
{
Forest.Clear();
PriorityQueue <Node, TCost> priorityQueue = new PriorityQueue <Node, TCost>();
HashSet <Node> hashSet = new HashSet <Node>();
Dictionary <Node, Arc> dictionary = new Dictionary <Node, Arc>();
ConnectedComponents connectedComponents = new ConnectedComponents(Graph, ConnectedComponents.Flags.CreateComponents);
foreach (HashSet <Node> component in connectedComponents.Components)
{
Node node = Enumerable.First <Node>((IEnumerable <Node>)component);
hashSet.Add(node);
foreach (Arc item in Graph.Arcs(node, ArcFilter.All))
{
Node node2 = Graph.Other(item, node);
dictionary[node2] = item;
priorityQueue[node2] = Cost(item);
}
}
connectedComponents = null;
while (priorityQueue.Count != 0)
{
Node node3 = priorityQueue.Peek();
priorityQueue.Pop();
hashSet.Add(node3);
Forest.Add(dictionary[node3]);
foreach (Arc item2 in Graph.Arcs(node3, ArcFilter.All))
{
Node node4 = Graph.Other(item2, node3);
if (!hashSet.Contains(node4))
{
TCost value = Cost(item2);
if (value.CompareTo(priorityQueue[node4]) < 0)
{
priorityQueue[node4] = value;
dictionary[node4] = item2;
}
}
}
}
}
public BiEdgeConnectedComponents(IGraph graph, Flags flags = Flags.None)
{
Graph = graph;
BridgeDfs bridgeDfs = new BridgeDfs();
bridgeDfs.Run(graph, null);
Count = bridgeDfs.ComponentCount;
if ((flags & Flags.CreateBridges) != 0)
{
Bridges = bridgeDfs.Bridges;
}
if ((flags & Flags.CreateComponents) != 0)
{
Subgraph subgraph = new Subgraph(graph);
foreach (Arc bridge in bridgeDfs.Bridges)
{
subgraph.Enable(bridge, false);
}
Components = new ConnectedComponents(subgraph, ConnectedComponents.Flags.CreateComponents).Components;
}
}
public BiEdgeConnectedComponents(IGraph graph, Flags flags = 0)
{
Graph = graph;
var dfs = new BridgeDfs();
dfs.Run(graph);
Count = dfs.ComponentCount;
if (0 != (flags & Flags.CreateBridges))
{
Bridges = dfs.Bridges;
}
if (0 != (flags & Flags.CreateComponents))
{
Subgraph withoutBridges = new Subgraph(graph);
foreach (var arc in dfs.Bridges)
{
withoutBridges.Enable(arc, false);
}
Components = new ConnectedComponents(withoutBridges, ConnectedComponents.Flags.CreateComponents).Components;
}
}
public Isomorphism(IGraph firstGraph, IGraph secondGraph, int maxIterations = 16)
{
FirstGraph = firstGraph;
SecondGraph = secondGraph;
FirstToSecond = null;
if (firstGraph.NodeCount() != secondGraph.NodeCount() ||
firstGraph.ArcCount() != secondGraph.ArcCount() ||
firstGraph.ArcCount(ArcFilter.Edge) != secondGraph.ArcCount(ArcFilter.Edge))
{
Isomorphic = false;
}
else
{
ConnectedComponents firstCC = new ConnectedComponents(firstGraph, ConnectedComponents.Flags.CreateComponents);
ConnectedComponents secondCC = new ConnectedComponents(secondGraph, ConnectedComponents.Flags.CreateComponents);
if (firstCC.Count != secondCC.Count ||
!firstCC.Components.Select(s => s.Count).OrderBy(x => x).SequenceEqual(
secondCC.Components.Select(s => s.Count).OrderBy(x => x)))
{
Isomorphic = false;
}
else
{
NodeHash firstHash = new NodeHash(firstGraph);
NodeHash secondHash = new NodeHash(secondGraph);
if (firstHash.ColoringHash != secondHash.ColoringHash)
{
// degree distribution not equal
Isomorphic = false;
}
else if (firstHash.RegularGraph && secondHash.RegularGraph &&
firstHash.ColoringHash == secondHash.ColoringHash)
{
// TODO do something with regular graphs
// maybe spectral test
Isomorphic = null;
}
else
{
Isomorphic = null;
for (int i = 0; i < maxIterations; ++i)
{
firstHash.Iterate();
secondHash.Iterate();
if (firstHash.ColoringHash != secondHash.ColoringHash)
{
Isomorphic = false;
break;
}
}
if (Isomorphic == null)
{
// graphs are very probably isomorphic (or tricky), try to find the mapping
var firstColor = firstHash.GetSortedColoring();
var secondColor = secondHash.GetSortedColoring();
// is the canonical coloring the same, and does it uniquely identify nodes?
Isomorphic = true;
for (int i = 0; i < firstColor.Count; ++i)
{
if (firstColor[i].Value != secondColor[i].Value)
{
// unlikely because the hashes matched
Isomorphic = false;
break;
}
else if (i > 0 && firstColor[i].Value == firstColor[i - 1].Value)
{
// two nodes colored the same way (this may happen)
// TODO handle this case. Else we won't work for graphs with symmetries.
Isomorphic = null;
break;
}
}
if (Isomorphic == true)
{
FirstToSecond = new Dictionary <Node, Node>(firstColor.Count);
for (int i = 0; i < firstColor.Count; ++i)
{
FirstToSecond[firstColor[i].Key] = secondColor[i].Key;
}
}
}
}
}
}
}
