/// <summary>
/// Solves the given problem.
/// </summary>
/// <returns></returns>
public override TSolution Solve(TProblem problem, TObjective objective, out TFitness fitness)
{
var zero = objective.Zero;
_log.Log(Logging.TraceEventType.Information, "Started generating initial solution...");
TFitness globalBestFitness;
var globalBest = _generator.Solve(problem, objective, out globalBestFitness);
_log.Log(Logging.TraceEventType.Information, "Initial solution generated: {0}.", globalBestFitness);
// report new solution.
this.ReportIntermidiateResult(globalBest);
var difference = objective.Zero;
if (_localSearch.Apply(problem, objective, globalBest, out difference))
{ // localsearch leads to better solution, adjust the fitness.
globalBestFitness = objective.Subtract(problem, globalBestFitness, difference);
_log.Log(Logging.TraceEventType.Information, "Improvement found by local search: {0}.", globalBestFitness);
// report new solution.
this.ReportIntermidiateResult(globalBest);
}
var i = 0;
var level = 1;
while (!this.IsStopped &&
(_stopCondition == null || !_stopCondition.Invoke(i, level, problem, objective, globalBest)))
{ // keep running until stop condition is true or this solver is stopped.
// shake things up a bit, or in other word change neighbourhood.
var perturbedSolution = (TSolution)globalBest.Clone();
var perturbedDifference = objective.Zero;
_perturber.Apply(problem, objective, perturbedSolution, level, out perturbedDifference);
// improve things by using a local search procedure.
var localSearchDifference = objective.Zero;
_localSearch.ApplyUntil(problem, objective, perturbedSolution, out localSearchDifference);
// calculate new fitness and compare.
TFitness newFitness = default(TFitness);
if (!objective.IsNonContinuous)
{ // solution fitness can be updated by adding the differences.
newFitness = objective.Add(problem, globalBestFitness, perturbedDifference);
newFitness = objective.Add(problem, newFitness, localSearchDifference);
}
else
{ // solution fitness needs to updated every time.
newFitness = objective.Calculate(problem, perturbedSolution);
}
if (objective.IsBetterThan(problem, newFitness, globalBestFitness))
{ // there was an improvement, keep new solution as global.
globalBestFitness = newFitness;
globalBest = perturbedSolution;
level = 1; // reset level.
_log.Log(Logging.TraceEventType.Information, "Improvement found by perturber and local search: {0}.", globalBestFitness);
// report new solution.
this.ReportIntermidiateResult(globalBest);
}
else
{
level = level + 1;
}
}
_log.Log(Logging.TraceEventType.Information, "Stop condition reached, best: {0}.", globalBestFitness);
fitness = globalBestFitness;
return(globalBest);
}