public void GenerateChildren(ref List <NodeState> queue, ref int MaxNodeStateAmount, ref int BSSFupdates, ref int TotalNodeStates, ref int TotalNodeStatesPrunned, int startCity)
{
int cityCount = Cities.Length;
//Get the first node in the priority
NodeState currentNodeState = DeletePriorityNode(ref queue);
//If the currentNodeState should be prunned
if (currentNodeState.GetLowerBound() >= bssf.costOfRoute())
{
currentNodeState = PruneTheQueue(ref queue, currentNodeState, ref TotalNodeStatesPrunned);
}
//Generate a child for each city the currentNodeState can go to.
for (int i = 0; i < cityCount; i++)
{
if (!currentNodeState.AlreadyVisited(i))
{
//Make a child
NodeState child = MakeChild(ref currentNodeState, i);
child.ReduceMatrixAndUpdateLowerBound(cityCount);
// Add to node states because a child was generated
TotalNodeStates++;
//If LB is less BSSF then add to queue, TNS++
if (child.GetLowerBound() < bssf.costOfRoute())
{
//Before adding to the queue, see if you have a new BSSF
if (BetterBSSFExists(ref child, startCity))
{
bssf = new TSPSolution(child.GetRoute());
BSSFupdates++;
}
else
{
//add node to the queue
if (!child.HasVisitedAllCities())
{
//Add
AddNodeToPriorityQueue(ref queue, child);
}
}
}
else
{
//Prune. We don't need to even visit it.
TotalNodeStatesPrunned++;
}
}
}
//Check the MaxNodeStates
CheckQueueSize(ref MaxNodeStateAmount, queue.Count - 1);
}
/// <summary>
/// performs a Branch and Bound search of the state space of partial tours
/// stops when time limit expires and uses BSSF as solution
/// </summary>
/// <returns>results array for GUI that contains three ints: cost of solution, time spent to find solution, number of solutions found during search (not counting initial BSSF estimate)</returns>
public string[] bBSolveProblem()
{
string[] results = new string[3];
Stopwatch timer = new Stopwatch();
timer.Start();
//Obtain a BSSF by using a GREEDY approach.
int startCity = 0;
bssf = new TSPSolution(GenerateInitialBSSF(ref startCity));
//Make an initial Matrix
int cityCount = Cities.Length;
double[,] initialMatrix = GetInitialMatrix(cityCount);
//Put start city in list
ArrayList startingRoute = new ArrayList();
startingRoute.Add(Cities[startCity]);
//Make Start node
int lowerBound = 0;
List <bool> citiesVisited = InitializeCitiesVisitedList(startCity, cityCount);
NodeState startNode = new NodeState(initialMatrix, lowerBound, startingRoute, startCity, citiesVisited);
startNode.ReduceMatrixAndUpdateLowerBound(cityCount);
Console.WriteLine("Initial BSSF: " + bssf.costOfRoute().ToString());
List <NodeState> priorityQueue = new List <NodeState>();
priorityQueue.Add(null);
priorityQueue.Add(startNode);
//Now we are ready to execute the branch and bound algorithm
int MaxNodeStateAmount = 1;
int BSSFupdates = 0;
int TotalNodeStates = 1;
int TotalNodeStatesPrunned = 0;
BranchAndBound(ref priorityQueue, ref MaxNodeStateAmount, ref BSSFupdates, ref TotalNodeStates, ref TotalNodeStatesPrunned, startCity, ref timer);
timer.Stop();
Console.WriteLine("Max NodeState Amount: " + MaxNodeStateAmount.ToString());
Console.WriteLine("Total Node States: " + TotalNodeStates.ToString());
Console.WriteLine("Total Node States Prunned: " + TotalNodeStatesPrunned.ToString() + "\r\n");
results[COST] = bssf.costOfRoute().ToString();
results[TIME] = timer.Elapsed.ToString();
results[COUNT] = BSSFupdates.ToString();
return(results);
}
