/// <summary>
/// Solves the given problem.
/// </summary>
/// <returns></returns>
public sealed override Tour Solve(TSPTWProblem problem, TObjective objective, out float fitness)
{
// generate random order for unplaced customers.
var customers = new List <int>();
for (var customer = 0; customer < problem.Times.Length / 2; customer++)
{
if (customer != problem.First &&
customer != problem.Last)
{
customers.Add(customer);
}
}
customers.Shuffle <int>();
// generate empty route based on problem definition.
var route = problem.CreateEmptyTour();
// add all customers by using cheapest insertion.
for (var i = 0; i < customers.Count; i++)
{
CheapestInsertionDirectedHelper.InsertCheapestDirected(route, problem.Times, problem.TurnPenalties,
customers[i], float.MaxValue);
}
// calculate fitness.
fitness = objective.Calculate(problem, route);
return(route);
}
/// <summary>
/// Applies this operator.
/// </summary>
public bool Apply(TSProblem problem, TSPObjective objective, Tour solution, out float delta)
{
if (problem.Weights.Length <= 2)
{
delta = 0;
return(false);
}
var before = objective.Calculate(problem, solution);
var weights = problem.Weights;
var turnPenalties = problem.TurnPenalties;
delta = 0;
// test switching directions in random order.
if (_pool == null || solution.Count != _pool.Size)
{ // create a new pool.
_pool = new RandomPool(solution.Count);
}
else
{ // just reset the existing one.
_pool.Reset();
}
var i = _n;
var toInsert = new List <int>();
while (_pool.MoveNext() && i > 0)
{
i--;
var currentId = _pool.Current;
var current = solution.GetDirectedId(currentId);
if (current != Constants.NOT_SET)
{
if (current != solution.First &&
current != solution.Last &&
solution.Remove(current))
{
toInsert.Add(current);
}
}
}
foreach (var current in toInsert)
{
CheapestInsertionDirectedHelper.InsertCheapestDirected(solution, weights, turnPenalties,
DirectedHelper.ExtractId(current));
}
var after = objective.Calculate(problem, solution);
delta = after - before;
return(delta < 0);
}
/// <summary>
/// Solves the given problem.
/// </summary>
/// <returns></returns>
public sealed override Tour Solve(STSProblem problem, STSPObjective objective, out STSPFitness fitness)
{
// generate empty route based on problem definition.
var route = problem.CreateEmptyTour();
fitness = new STSPFitness()
{
Weight = 0,
Customers = 1
};
// generate random pool to select customers from.
if (_randomPool == null || _randomPool.Size < problem.Weights.Length)
{
_randomPool = new RandomPool(problem.Weights.Length / 2);
}
else
{
_randomPool.Reset();
}
// keep adding customers until no more space is left or no more customers available.
while (_randomPool.MoveNext())
{
var customer = _randomPool.Current;
if (customer == DirectedHelper.ExtractId(route.First) ||
(route.Last.HasValue && customer == DirectedHelper.ExtractId(route.Last.Value)))
{ // customer is first or last.
continue;
}
var cost = CheapestInsertionDirectedHelper.InsertCheapestDirected(route, problem.Weights, problem.TurnPenalties,
customer, problem.Max - fitness.Weight);
if (cost > 0)
{
fitness.Customers++;
fitness.Weight += cost;
}
}
// calculate fitness.
fitness = objective.Calculate(problem, route);
return(route);
}