/// <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()
{
Stopwatch timer = new Stopwatch();
timer.Start();
initialBSSF = true;
greedySolveProblem();
string[] results = new string[3];
int n = Cities.Length;
double[,] baseMatrix = new double[n, n];
int count;
ReducedMatrix currentCity;
queue = new PriorityQueue();
ReducedMatrix reduced;
for (int i = 0; i < n; i++)
{
for (int j = 0; j < n; j++)
{
if (i == j)
{
baseMatrix[i, j] = Double.PositiveInfinity;
}
else
{
baseMatrix[i, j] = Cities[i].costToGetTo(Cities[j]);
}
}
}
reduced = new ReducedMatrix(baseMatrix, Cities.Length, Cities[0]);
reduced.reduce();
queue.add(reduced);
count = 0;
totalStates = 1;
while (true)
{
if (queue.getSize() > maxStroedStates)
{
maxStroedStates = queue.getSize();
}
if (timer.ElapsedMilliseconds > time_limit)
{
break;
}
currentCity = queue.remove();
if (currentCity == null)
{
break;
}
if (currentBssf < currentCity.bound)
{
break;
}
for (int i = 1; i < n; i++)
{
if (currentCity.matrix[currentCity.cityNumber, i] != INFINITY)
{
ReducedMatrix newMatrix = new ReducedMatrix(currentCity, Cities[i], i);
newMatrix.cancel(currentCity.cityNumber, i);
newMatrix.reduce();
if (newMatrix.Route.Count == Cities.Length)
{
if (newMatrix.bound < currentBssf)
{
numBSSFUpdates++;
bssf = new TSPSolution(newMatrix.Route);
currentBssf = newMatrix.bound;
}
count++;
break;
}
if (newMatrix.bound < currentBssf)
{
queue.add(newMatrix);
totalStates++;
}
else
{
numStatesPruned++;
}
}
}
}
timer.Stop();
numStatesPruned += queue.getSize();
String track;
track = "MAX #of stored states " + maxStroedStates + "\n";
track += "#of BSSF updates " + numBSSFUpdates + "\n";
track += "Total states created " + totalStates + "\n";
track += "Total states pruned " + numStatesPruned + "\n";
MessageBox.Show(track);
results[COST] = bssf.costOfRoute().ToString(); // load results into array here, replacing these dummy values
results[TIME] = timer.Elapsed.ToString();
results[COUNT] = count.ToString();
return(results);
}