public Solution Solve(KnapsackData data)
{
_data = data;
long start = DateTime.UtcNow.Millisecond;
var current = new BinarySolution(data.AvailableItems.Count);
var best = current;
current.UpdateFitness(data, Alpha);
while (_temperature > _endingTemperature)
{
for (var m = 0; m < _samplingSize; m++)
{
current = GetNextState(current);
if (current.Fitness < best.Fitness)
{
best = current;
}
}
Cool();
}
long end = DateTime.UtcNow.Millisecond;
var pickedItem = GenerateSolution(data, best);
return(new Solution(pickedItem, end - start));
}
private BinarySolution GetNeighbour(BinarySolution current)
{
var mutated = new BinarySolution(current);
var rnd = new Random();
var x = rnd.Next(current.GetSize());
mutated.Flip(x);
mutated.UpdateFitness(_data, Alpha);
return(mutated);
}
public List <Item> GenerateSolution(KnapsackData knapsackData, BinarySolution solution)
{
var pickedItem = new List <Item>();
for (var i = 0; i < knapsackData.AvailableItems.Count; i++)
{
if (solution.GetBit(i) == 1)
{
pickedItem.Add(knapsackData.AvailableItems[i]);
}
}
return(pickedItem);
}
private BinarySolution GetNextState(BinarySolution current)
{
var newSolution = GetNeighbour(current);
var delta = newSolution.Fitness - current.Fitness;
if (delta < 0)
{
return(newSolution);
}
var rnd = new Random();
var x = rnd.NextDouble();
if (x < Math.Exp(-delta / _temperature))
{
return(newSolution);
}
return(current);
}
public BinarySolution(BinarySolution other)
{
_chromosome = other._chromosome;
Fitness = other.Fitness;
Weight = other.Weight;
}