public DirectedGraph Sample(DirectedGraph graph, int sampledVertexCount, double burningProbability, Random random)
{
var result = new DirectedGraph();
var index2index = new Dictionary<int, int>();
var visit = new bool[graph.Vertices.Count];
while (result.Vertices.Count < sampledVertexCount) {
// 開始点を決める
int start;
do { start = random.Next(graph.Vertices.Count); } while (visit[start]);
var stack = new Stack<int>();
stack.Push(start);
AddVertexToResultGraph(start, graph, result, index2index);
visit[start] = true;
while (stack.Count > 0 && result.Vertices.Count < sampledVertexCount) {
int v = stack.Pop();
var outEdges = graph.OutEdges[v];
for (int i = 0; i < outEdges.Count; ++i) {
if (random.NextDouble() >= burningProbability) { break; }
// i番目以降の辺を一つ選んでi番目と入れ替える
int j = random.Next(i, outEdges.Count);
Edge t = outEdges[i];
outEdges[i] = outEdges[j];
outEdges[j] = t;
// 結果に追加
int dst = outEdges[i].Dst;
if (!visit[dst]) { AddVertexToResultGraph(dst, graph, result, index2index); }
result.AddEdge(new Edge(index2index[v], index2index[dst]));
// 再帰的に探索
if (!visit[dst]) {
visit[dst] = true;
stack.Push(dst);
}
}
}
}
return result;
}
/// <summary>
/// Cools system until it reaches minimal, targeted temperature.
/// </summary>
/// <param name="algorithm">Simulated annealing algorithm being cooled.</param>
/// <param name="coolingAction">Delegate of action to cool system by one step of cooling ratio.</param>
/// <returns>Processor time cost</returns>
//TODO: Possibly a more narrow dependency to something like ISimulatedAnnealing to not force cast for CurrentTemperature access?
public IEnumerable<IAlgorithmProgressReport> Cool(IAlgorithm algorithm, Action coolingAction)
{
if (algorithm == null) throw new ArgumentException(nameof(algorithm));
if (coolingAction == null) throw new ArgumentException(nameof(coolingAction));
var startTime = DateTime.Now.Ticks;
while (algorithm.CanContinueSearching())
{
//Pick random node from graph and keep on adding them to solution until correctness criteria is met
HashSet<Node> proposedSolution = new HashSet<Node>();
List<Node> nodesCopy = algorithm.Graph.Nodes;
Stack<int> randomIndexes = new Stack<int>(Enumerable.Range(0, nodesCopy.Count).OrderBy(r => _random.Next()));
while (!algorithm.Problem.IsSolutionCorrect(proposedSolution))
{
proposedSolution.Add(nodesCopy[randomIndexes.Pop()]);
}
bool wasAccepted = false;
//Accept the answer if algorithm allows
if (algorithm.CanAcceptAnswer(proposedSolution))
{
algorithm.Problem.SetNewSolution(proposedSolution);
wasAccepted = true;
}
var casted = algorithm as SimulatedAnnealing;
var currentTemp = casted == null ? 0 : casted.CurrentTemperature;
yield return new SimulatedAnnealingProgressReport(DateTime.Now.Ticks - startTime, algorithm.Problem.CurrentSolution, (uint)(algorithm.Graph.TotalNodes - algorithm.Problem.CurrentSolution.Count + 1), currentTemp, wasAccepted);
//Cool system
coolingAction.Invoke();
}
}
