private void Swap(int xi, int yi)
{
SubProblem temp = this.queue[xi];
this.queue[xi] = this.queue[yi];
this.queue[yi] = temp;
}
public SubProblem Pop()
{
SubProblem minimum = this.queue[0];
this.Swap(0, this.queue.Count - 1);
this.queue.RemoveAt(queue.Count - 1);
int i = 0;
while (this.GetLeftChildIndex(i) < this.queue.Count)
{
int leftChildIndex = this.GetLeftChildIndex(i);
int rightChildIndex = this.GetRightChildIndex(i);
int minChildIndex;
if (rightChildIndex >= this.queue.Count)
{
minChildIndex = leftChildIndex;
}
else if (this.GetHeuristic(this.queue[leftChildIndex]) < this.GetHeuristic(this.queue[rightChildIndex]))
{
minChildIndex = leftChildIndex;
}
else
{
minChildIndex = rightChildIndex;
}
if (this.GetHeuristic(this.queue[minChildIndex]) < this.GetHeuristic(this.queue[i]))
{
this.Swap(i, minChildIndex);
i = minChildIndex;
}
else
{
break;
}
}
return(minimum);
}
public double GetHeuristic(SubProblem subProblem)
{
return(4 * subProblem.lowerBound / subProblem.path.Count);
}
public void Add(SubProblem subProblem)
{
this.queue.Add(subProblem);
this.BubbleUp(this.queue.Count - 1);
}
public int BBSolution(Stopwatch timer)
{
// Stats
int maxStates = 0;
int totalStates = 0;
int prunedStates = 0;
int count = 0;
PriorityQueue q = new PriorityQueue();
SubProblem initialSubProblem = new SubProblem(
this.CalculateCostMatrix(),
this.Cities.Length,
0,
new List <int>()
);
initialSubProblem.path.Add(0);
q.Add(initialSubProblem);
while (!q.Empty() && timer.ElapsedMilliseconds < this.time_limit)
{
// Update statistics
if (q.Size() > maxStates)
{
maxStates = q.Size();
}
++totalStates;
SubProblem subProblem = q.Pop();
if (subProblem.path.Count == this.Cities.Length &&
subProblem.path[subProblem.GetCurrentCityIndex()] != 0)
{
// The subproblem is a valid solution!
this.bssf = new TSPSolution(PathToRoute(subProblem.path));
count++;
}
else
{
if (subProblem.HasMorePaths())
{
for (int col = 0; col < this.Cities.Length; ++col)
{
if (subProblem.reducedMatrix[subProblem.GetCurrentCityIndex(), col] != double.PositiveInfinity)
{
if (subProblem.reducedMatrix[subProblem.GetCurrentCityIndex(), col] + subProblem.lowerBound < this.costOfBssf())
{
List <int> pathClone = new List <int>(subProblem.path);
SubProblem newProblem = new SubProblem(
(double[, ])subProblem.reducedMatrix.Clone(),
this.Cities.Length,
subProblem.lowerBound,
pathClone
);
newProblem.path.Add(col);
newProblem.BlockPaths(
subProblem.GetCurrentCityIndex(),
newProblem.GetCurrentCityIndex()
);
newProblem.ReduceCostMatrix();
q.Add(newProblem);
}
else
{
++prunedStates;
}
}
}
}
}
}
// Print stats
Console.WriteLine("Max # of states: {0}", maxStates);
Console.WriteLine("Total # number of states: {0}", totalStates);
Console.WriteLine("# of states pruned: {0}", prunedStates);
return(count);
}
