private LbDifferenceResult CalculateGreatestLBDifference(State state)
{
LbDifferenceResult currentGreatestLbDiff = null;
for (int i = 0; i < state.Matrix.GetMatrix().GetLength(0); i++)
{
for (int j = 0; j < state.Matrix.GetMatrix().GetLength(0); j++)
{
if (state.Matrix.GetMatrix()[i, j] == 0)
{
LbDifferenceResult lbDifference = GetLbDifference(i, j, state);
if (currentGreatestLbDiff == null ||
lbDifference.LowerBoundDifference > currentGreatestLbDiff.LowerBoundDifference)
{
if (currentGreatestLbDiff != null)
{
_prunedSates += 2;
}
currentGreatestLbDiff = lbDifference;
}
else
{
_prunedSates += 2;
}
}
}
}
return(currentGreatestLbDiff);
}
public PathCalculation CalculatePath()
{
Stopwatch stopwatch = new Stopwatch();
stopwatch.Start();
while (pq.Count != 0)
{
if (stopwatch.Elapsed.Seconds >= 30)
{
break;
}
State state = pq.RemoveMin();
if (state.GetLowerBound() < _bssf)
{
LbDifferenceResult greatestDifferenceResult = CalculateGreatestLBDifference(state);
State[] children = new State[2]
{
greatestDifferenceResult.IncludeState, greatestDifferenceResult.ExcludeState
};
foreach (State child in children)
{
if (IsSolution(child))
{
bssfUpdates++;
_bssf = child.GetLowerBound();
_bestStateSoFar = child;
}
else if (child.GetLowerBound() < _bssf)
{
// Dividing by the number cities in the solution is a great way to prioritize those solutions
// that are further along. This helps the algorithm "dig deeper" into the search.
pq.Add((int)child.GetLowerBound() / (child.GetCitiesInSolution() == 0 ? 1 : child.GetCitiesInSolution()), child);
if (pq.Count > _maxStatesStored)
{
_maxStatesStored = pq.Count;
}
}
else
{
_prunedSates++;
}
}
}
else
{
_prunedSates++;
}
}
stopwatch.Stop();
Console.WriteLine("----------------------------------");
Console.WriteLine("Elapsed Time: " + stopwatch.ElapsedMilliseconds);
Console.WriteLine("Problem Size: " + _cities.Length);
Console.WriteLine("Max States: " + _maxStatesStored);
Console.WriteLine("Total Created: " + _createdStates);
Console.WriteLine("States Pruned: " + _prunedSates);
Console.WriteLine("----------------------------------");
return(GeneratePathResult(_bestStateSoFar, _cities, stopwatch.ElapsedMilliseconds));
}