/// <summary>
/// Tries to improve the existing route using CI and return true if succesful.
/// </summary>
/// <param name="problem"></param>
/// <param name="route"></param>
/// <param name="difference"></param>
/// <returns></returns>
public bool Improve(IProblemWeights problem, IRoute route, out double difference)
{
bool improvement = false;
difference = 0;
if (route.Count > 3)
{
// loop over all customers and try cheapest insertion.
for (int customer = 0; customer < problem.Size; customer++)
{
//string route_string = route.ToString();
//IRoute previous = route.Clone() as IRoute;
if (route.Contains(customer))
{
// remove customer and keep position.
int next = route.GetNeigbours(customer)[0];
route.Remove(customer);
// insert again.
ArbitraryInsertionSolver.InsertOne(problem, route, customer, out difference);
if (!route.IsValid())
{
throw new Exception();
}
if (route.GetNeigbours(customer)[0] != next &&
difference < 0)
{ // another customer was found as the best, improvement is succesful.
improvement = true;
break;
}
}
}
}
return(improvement);
}
/// <summary>
/// Does the actual solving.
/// </summary>
/// <param name="problem"></param>
/// <returns></returns>
protected override IRoute DoSolve(IProblem problem)
{
// convert to a symetric problem if needed.
IProblem _problem = problem;
if (!_problem.Symmetric)
{
_problem = Convertor.ConvertToSymmetric(_problem);
_was_asym = true;
}
// create the list of customers.
_customers = new List<int>();
for (int customer = 0; customer < _problem.Size; customer++)
{
_customers.Add(customer);
}
_sparse_set = SparseSetHelper.CreateNearestNeighourSet(_problem, _customers, _customers.Count / 10);
//_sparse_set = SparseSetHelper.CreateNonSparseSet(_problem, _customers);
// construct a route from the customers.
//FixedSymmetricRoute init_route = new FixedSymmetricRoute(_customers);
// construct a random route using best-placement.
ArbitraryInsertionSolver bp_solver = new ArbitraryInsertionSolver();
IRoute bp_route = bp_solver.Solve(_problem);
FixedSymmetricRoute init_route = new FixedSymmetricRoute(bp_route);
double init_route_weight = LinKernighanSolver.Weight(_problem, init_route);
RouteFound route = new RouteFound()
{
Route = init_route,
RouteWeight = init_route_weight
};
OsmSharp.Logging.Log.TraceEvent("LinKernighanSolver", Logging.TraceEventType.Information, "Route {0}:{1}",
route.Route.ToString(),
route.RouteWeight);
// step 2.
EdgeSet X = new EdgeSet();
EdgeSet Y = new EdgeSet();
IList<int> untried_t_1 = new List<int>(route.Route);
while (untried_t_1.Count > 0)
{
// select t1.
int t_1 = untried_t_1[0];
untried_t_1.RemoveAt(0);
// search route with t_1.
RouteFound t_1_route = this.AfterSelectt1(_problem, route, X, Y, t_1);
// select the better route.
if (t_1_route.RouteWeight < route.RouteWeight)
{
untried_t_1 = new List<int>(route.Route);
route = RouteFound.SelectBest(route, t_1_route);
X = new EdgeSet();
Y = new EdgeSet();
}
} // step 2 and step 12.
// convert back to asym solution if needed.
//result.RemoveAt(result.Count - 1);
if (_was_asym)
{
return this.ConvertToASymRoute(new List<int>(route.Route));
}
return route.Route;
}
/// <summary>
/// Returns a solution found using best-placement.
/// </summary>
/// <returns></returns>
protected override IRoute DoSolve(IProblem problem)
{
// build the customer list to place.
List <int> customers = null;
if (_customers != null)
{ // copy the list of the given customers and keep this order.
customers = new List <int>(_customers);
}
else
{ // generate some random route.
customers = new List <int>();
List <int> customers_to_place = new List <int>();
for (int customer = 0; customer < problem.Size; customer++)
{
customers_to_place.Add(customer);
}
while (customers_to_place.Count > 0)
{
int idx = OsmSharp.Math.Random.StaticRandomGenerator.Get().Generate(customers_to_place.Count);
customers.Add(customers_to_place[idx]);
customers_to_place.RemoveAt(idx);
}
}
// initialize the route based on the problem definition.
IRoute route = null;
double weight = double.MaxValue;
if (problem.Symmetric)
{ // create a symmetric route that is dynamic and can accept new customers.
if (problem.First.HasValue && problem.Last.HasValue && problem.First == problem.Last)
{ // route is a round.
route = new DynamicSymmetricRoute(problem.First.Value);
}
else
{ // not a round.
throw new NotImplementedException("No symmetric routes implemented that are not rounds!");
}
}
else
{ // create a asymmetric route that is dynamic and can accept new customers.
if (problem.First.HasValue)
{ // the first customer is set.
// test if the last customer is the same.
if (!problem.Last.HasValue ||
problem.Last == problem.First)
{ // the route is a round.
route = new DynamicAsymmetricRoute(customers.Count, problem.First.Value, true);
// remove the first customer.
customers.Remove(problem.First.Value);
// find the customer that is farthest away and add it.
int to = -1;
weight = double.MinValue;
for (int x = 0; x < customers.Count; x++)
{
if (x != problem.First.Value)
{ // only different customers.
double current_weight = problem.WeightMatrix[x][problem.First.Value] +
problem.WeightMatrix[problem.First.Value][x];
if (current_weight > weight)
{ // the current weight is better.
to = x;
weight = current_weight;
}
}
}
route.InsertAfter(problem.First.Value, to);
customers.Remove(to);
}
else
{ // the route is not a round.
route = new DynamicAsymmetricRoute(customers.Count, problem.First.Value, false);
route.InsertAfter(problem.First.Value, problem.Last.Value);
// remove the first customer.
customers.Remove(problem.First.Value);
customers.Remove(problem.Last.Value);
}
}
else
{ // the first and last customer can be choosen randomly.
// find two customers close together.
int from = -1;
int to = -1;
for (int x = 0; x < customers.Count; x++)
{
for (int y = 0; y < customers.Count; y++)
{
if (x != y)
{ // only different customers.
double current_weight = problem.WeightMatrix[x][y];
if (current_weight < weight)
{ // the current weight is better.
from = x;
to = y;
weight = current_weight;
if (weight == 0)
{ // no edge with less weight is going to be found.
break;
}
}
}
}
}
route = new DynamicAsymmetricRoute(customers.Count, from, false);
route.InsertAfter(from, to);
// remove the first customer.
customers.Remove(from);
customers.Remove(to);
}
}
// insert the rest of the customers.
while (customers.Count > 0 && !_stopped)
{ // keep placing customer 0 until all customers are placed.
int customer = customers[0];
customers.RemoveAt(0);
// insert the customer at the best place.
double difference;
ArbitraryInsertionSolver.InsertOne(problem, route, customer, out difference);
}
return(route);
}
