/// <summary>
/// Solves the given problem.
/// </summary>
/// <returns></returns>
public sealed override Tour Solve(STSProblem problem, STSPObjective objective, out STSPFitness fitness)
{
// generate random pool to select customers from.
if (_randomPool == null || _randomPool.Size < problem.Weights.Length)
{
_randomPool = new RandomPool(problem.Weights.Length);
}
else
{
_randomPool.Reset();
}
// keep adding customers until no more space is left or no more customers available.
var tour = problem.CreateEmptyTour();
fitness = new STSPFitness()
{
Weight = 0,
Customers = 1
};
while (_randomPool.MoveNext())
{
var customer = _randomPool.Current;
if (customer == problem.First ||
customer == problem.Last)
{
continue;
}
Pair location;
var cost = CheapestInsertionHelper.CalculateCheapest(tour, problem.Weights, customer, out location);
if (cost + fitness.Weight < problem.Max)
{
tour.InsertAfter(location.From, customer);
fitness.Weight = fitness.Weight + cost;
fitness.Customers = fitness.Customers + 1;
}
}
// calculate fitness.
fitness = objective.Calculate(problem, tour);
return(tour);
}
/// <summary>
/// Applies this operator.
/// </summary>
public bool Apply(STSProblem problem, STSPObjective objective, Tour solution, out STSPFitness delta)
{
var before = objective.Calculate(problem, solution);
var weights = problem.Weights;
delta = objective.Zero;
var i = _n;
var toInsert = new List <int>();
if (!_insertNew)
{ // select existing customers, to reinsert.
while (solution.Count > 1 && i > 0)
{
i--;
var index = RandomGeneratorExtensions.GetRandom().Generate(solution.Count);
var current = solution.GetCustomerAt(index);
if (current != Constants.NOT_SET)
{
if (current != solution.First &&
current != solution.Last &&
solution.Remove(current))
{
toInsert.Add(current);
}
}
}
}
else if (solution.Count < problem.Weights.Length)
{ // select random new customer to insert.
while (solution.Count > 1 && i > 0)
{
i--;
var current = RandomGeneratorExtensions.GetRandom().Generate(problem.Weights.Length);
if (!solution.Contains(current))
{
if (current != solution.First &&
current != solution.Last &&
solution.Remove(current))
{
toInsert.Add(current);
}
}
}
}
var fitness = objective.Calculate(problem, solution);
foreach (var current in toInsert)
{
// insert new.
Pair position;
var cost = CheapestInsertionHelper.CalculateCheapest(solution, weights, current, out position);
if (cost + fitness.Weight < problem.Max)
{
solution.InsertAfter(position.From, current);
fitness.Weight = fitness.Weight + cost;
fitness.Customers = fitness.Customers + 1;
}
}
var after = objective.Calculate(problem, solution);
delta = objective.Subtract(problem, after, before);
return(objective.CompareTo(problem, before, after) > 0);
}