public QuadAssignment GenerateNeighbor(ISimAnSolution baseSolution)
{
if (!(baseSolution is QuadAssignment qaSol))
{
return(null);
}
// generate a copy of the existing assignment
QuadAssignment neighbor = new QuadAssignment();
foreach (var item in qaSol.AssignmentSolution)
{
neighbor.AssignmentSolution.Add(item.Key, item.Value);
}
// exchange one pair of unit-location assignments
int unit1 = _rnd.Next(0, QuadAssignment.MaterialFlow.GetLength(0));
int unit2 = _rnd.Next(0, QuadAssignment.MaterialFlow.GetLength(0));
int assignment1 = qaSol.AssignmentSolution[unit1];
int assignment2 = qaSol.AssignmentSolution[unit2];
neighbor.AssignmentSolution[unit1] = assignment2;
neighbor.AssignmentSolution[unit2] = assignment1;
// calculate objective value and return neighbor
neighbor.CalculateFitness();
return(neighbor);
}
public void OptimizeAssignment(double[,] materialFlow, double[,] distances)
{
QuadAssignment.MaterialFlow = materialFlow;
QuadAssignment.Distances = distances;
if (materialFlow.GetLength(0) > distances.GetLength(0))
{
throw new ArgumentException($"Not enough locations to assign all units!");
}
//setup the heuristic optimization
SimAnHeurParams saParams = new SimAnHeurParams(defaultStepSize: 5, defaultCoolDown: 0.95, startTemp: 35);
saParams.GenerateNeighborSolution = this.GenerateNeighbor;
saParams.MaxIter = (int)Math.Pow(10, 4);
//optimize
ISimAnSolution startSolution = GenerateStartSolution();
SimAnHeuristic heuristic = new SimAnHeuristic(saParams, startSolution);
SimAnOutput output = heuristic.Minimize();
Console.WriteLine("**************");
Console.WriteLine(output.ToString());
Console.WriteLine("**************");
foreach (var item in (output.BestSolution as QuadAssignment).AssignmentSolution)
{
Console.WriteLine($" Unit {item.Key} assigned to location {item.Value}.");
}
Console.WriteLine("**************");
}
internal SimAnOutput(ISimAnSolution finalSol,
List <double> temperatureFitness,
List <double> iterFitness,
double initSolVal)
{
BestSolution = finalSol;
TemperatureFitnessLevels = temperatureFitness;
IterationFitnessLevels = iterFitness;
Iterations = iterFitness.Count;
InitialObjective = initSolVal;
}
public SimAnOutput Minimize()
{
bool stop = false;
_bestSolution = _startSolution;
ISimAnSolution currentSolution = _startSolution;
double deltaFitness, curTemp = _params.StartTemp;
int iter = 0, iterCoolDown;
iterCoolDown = iter + _params.CoolDownStepSize(curTemp);
int accepted = 0;
List <double> temperatureFitnessLevels = new List <double>();
List <double> iterationFitnessLevels = new List <double>()
{
currentSolution.Fitness
};
while (!stop)
{
//generate neighbor solution
ISimAnSolution neighbor = _params.GenerateNeighborSolution(currentSolution);
deltaFitness = neighbor.Fitness - currentSolution.Fitness;
//acceptance test
if (AcceptNeighbor(deltaFitness, curTemp))
{
currentSolution = neighbor;
accepted += 1;
}
//improvement test
if (currentSolution.Fitness < _bestSolution.Fitness)
{
_bestSolution = currentSolution;
}
iterationFitnessLevels.Add(currentSolution.Fitness);
iter++;
//cooldown by annealing schedule
if (iter == iterCoolDown)
{
//record statistics for this temp-level (plateau)
temperatureFitnessLevels.Add(_bestSolution.Fitness);
//update temperature and set next cooldown iteration
curTemp = _params.CoolDown(curTemp);
iterCoolDown += _params.CoolDownStepSize(curTemp);
//test abort criterion
stop = StopSearchAfterPlateau(accepted, temperatureFitnessLevels);
//reset number of accepted solutions within plateau
accepted = 0;
}
stop = stop | iter > _params.MaxIter;
}
return(new SimAnOutput(_bestSolution, temperatureFitnessLevels, iterationFitnessLevels, _startSolution.Fitness));
}
public SimAnHeuristic(SimAnHeurParams p, ISimAnSolution startSol, int randomSeed = 1)
{
if (p == null)
{
throw new ArgumentNullException(nameof(p));
}
if (p.CoolDown == null)
{
throw new ArgumentNullException(nameof(p), "CoolDown of the SimAnHeurParams is null.");
}
if (p.CoolDownStepSize == null)
{
throw new ArgumentNullException(nameof(p), "CoolDownStepSize of the SimAnHeurParams is null.");
}
if (p.GenerateNeighborSolution == null)
{
throw new ArgumentNullException(nameof(p), "GenerateNeighborSolution of the SimAnHeurParams is null.");
}
_params = p;
_startSolution = startSol;
_rnd = new Random(randomSeed);
}
