private Node getPartialRoute(Node node, int rowNum, int colNum)
{
double[,] updated = new double[Cities.Length, Cities.Length];
for (int i = 0; i < Cities.Length; i++)
{
for (int k = 0; k < Cities.Length; k++)
{
updated[i, k] = node.getMatrix()[i, k];
}
}
ArrayList partialRoute = new ArrayList();
for (int i = 0; i < node.getRoute().Count; i++)
{
partialRoute.Add(node.getRoute()[i]);
}
double newbssf = node.getbssf() + node.getMatrix()[rowNum, colNum];
for (int i = 0; i < Cities.Length; i++)
{
updated[rowNum, i] = double.PositiveInfinity;
updated[i, colNum] = double.PositiveInfinity;
}
updated[rowNum, colNum] = double.PositiveInfinity;
updated[colNum, rowNum] = double.PositiveInfinity;
partialRoute.Add(Cities[colNum]);
Node newNode = new Node(newbssf, updated, partialRoute);
newNode.setNum(colNum);
return(reduceMatrix(newNode));
}
private Node reduceMatrix(Node node)
{
double[,] updated = new double[Cities.Length, Cities.Length];
double updatedbssf = node.getbssf();
for (int i = 0; i < Cities.Length; i++)
{
for (int k = 0; k < Cities.Length; k++)
{
updated[i, k] = node.getMatrix()[i, k];
}
}
for (int i = 0; i < Cities.Length; i++) //for each row
{
double min = double.PositiveInfinity;
for (int k = 0; k < Cities.Length; k++) //get minimum for each row
{
if (updated[i, k] < min)
{
min = updated[i, k];
}
}
if (min != 0 && min != double.PositiveInfinity)
{
for (int k = 0; k < Cities.Length; k++) //subtract minimum from each value
{
updated[i, k] -= min;
}
updatedbssf += min;
}
}
for (int i = 0; i < Cities.Length; i++) //for each column
{
double min = double.PositiveInfinity;
for (int k = 0; k < Cities.Length; k++) //get minimum for each column
{
if (updated[k, i] < min)
{
min = updated[k, i];
}
}
if (min != 0 && min != double.PositiveInfinity)
{
for (int k = 0; k < Cities.Length; k++) //subtract minimum from each value
{
updated[k, i] -= min;
}
updatedbssf += min;
}
}
Node newNode = new Node(updatedbssf, updated, node.getRoute());
newNode.setNum(node.getNum());
return(newNode);
}
/// <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];
string[] origResults = defaultSolveProblem();
double origbssf = Convert.ToDouble(origResults[COST]);
double[,] originalDistances = new double[Cities.Length, Cities.Length];
List <Node> todoNodes = new List <Node>();
int numSolutions = 0;
int numChildStates = 0;
int statesPruned = 0;
int numBSSF = 0;
int maxNumOfStates = 0;
double bestSolution = origbssf;
ArrayList routeSolution = new ArrayList();
for (int i = 0; i < Cities.Length; i++) //make original matrix from default route
{
for (int k = 0; k < Cities.Length; k++)
{
if (i == k)
{
originalDistances[i, k] = double.PositiveInfinity;
}
else
{
originalDistances[i, k] = Cities[i].costToGetTo(Cities[k]);
}
}
}
Stopwatch timer = new Stopwatch();
timer.Start();
routeSolution.Add(Cities[0]);
Node startNode = new Node(0, originalDistances, routeSolution);
//put nodes in queue
todoNodes.Add(reduceMatrix(startNode));
while (todoNodes.Count > 0) //while the list is not empty
{
if (timer.Elapsed.TotalSeconds >= TIME_LIMIT)
{
break;
}
Node node = todoNodes[0]; //get first element
if (node.getRoute().Count == Cities.Length) //if a leaf node
{
numSolutions++;
TSPSolution sol = new TSPSolution(node.getRoute());
if (sol.costOfRoute() < bestSolution) //reset the best solution if it is lower
{
bestSolution = sol.costOfRoute();
routeSolution = node.getRoute();
numBSSF++;
}
}
else //if not a leaf node
{
if (node.getbssf() <= bestSolution) //pruning not needed
{
for (int i = 1; i < Cities.Length; i++)
{
if (node.getMatrix()[node.getNum(), i] != double.PositiveInfinity)
{
todoNodes.Add(getPartialRoute(node, node.getNum(), i));
numChildStates++;
}
}
}
else
{
statesPruned++;
}
}
if (todoNodes.Count > maxNumOfStates)
{
maxNumOfStates = todoNodes.Count;
}
todoNodes.RemoveAt(0); //remove the node when finished calculating
todoNodes.Sort(); //sorting based on priority
}
timer.Stop();
bssf = new TSPSolution(routeSolution);
Console.WriteLine("Number of child states is " + numChildStates);
Console.WriteLine("Number of states pruned is " + statesPruned);
Console.WriteLine("Number of bssf updates is " + numBSSF);
Console.WriteLine("Number of stored states is " + maxNumOfStates);
results[COST] = bssf.costOfRoute().ToString(); // load results into array here, replacing these dummy values
results[TIME] = timer.Elapsed.ToString();
results[COUNT] = numSolutions.ToString();
return(results);
}
