public static ItemArray <IItem> Apply(IItem initiator, IItem guide, IntValue k, PercentValue n)
{
if (!(initiator is RealVector) || !(guide is RealVector))
{
throw new ArgumentException("Cannot relink path because one of the provided solutions or both have the wrong type.");
}
if (n.Value <= 0.0)
{
throw new ArgumentException("RelinkingAccuracy must be greater than 0.");
}
RealVector v1 = initiator.Clone() as RealVector;
RealVector v2 = guide as RealVector;
if (v1.Length != v2.Length)
{
throw new ArgumentException("The solutions are of different length.");
}
IList <RealVector> solutions = new List <RealVector>();
for (int i = 0; i < k.Value; i++)
{
RealVector solution = v1.Clone() as RealVector;
for (int j = 0; j < solution.Length; j++)
{
solution[j] = v1[j] + 1 / (k.Value - i) * (v2[j] - v1[j]);
}
solutions.Add(solution);
}
IList <IItem> selection = new List <IItem>();
if (solutions.Count > 0)
{
int noSol = (int)(solutions.Count * n.Value);
if (noSol <= 0)
{
noSol++;
}
double stepSize = (double)solutions.Count / (double)noSol;
for (int i = 0; i < noSol; i++)
{
selection.Add(solutions.ElementAt((int)((i + 1) * stepSize - stepSize * 0.5)));
}
}
return(new ItemArray <IItem>(selection));
}
public override IOperation Apply()
{
RealVector bestSol = CurrentScope.Variables[SolutionParameter.ActualName].Value as RealVector;
if (bestSol == null)
{
throw new ArgumentException("Cannot improve solution because it has the wrong type.");
}
var evaluator = Evaluator;
double bestSolQuality = evaluator.Evaluate(bestSol);
// create perturbed solutions
RealVector[] simplex = new RealVector[bestSol.Length];
for (int i = 0; i < simplex.Length; i++)
{
simplex[i] = bestSol.Clone() as RealVector;
simplex[i][i] += 0.1 * (Bounds[0, 1] - Bounds[0, 0]);
if (simplex[i][i] > Bounds[0, 1])
{
simplex[i][i] = Bounds[0, 1];
}
if (simplex[i][i] < Bounds[0, 0])
{
simplex[i][i] = Bounds[0, 0];
}
}
// improve solutions
for (int i = 0; i < ImprovementAttempts.Value; i++)
{
// order according to their objective function value
Array.Sort(simplex, (x, y) => evaluator.Evaluate(x).CompareTo(evaluator.Evaluate(y)));
// calculate centroid
RealVector centroid = new RealVector(bestSol.Length);
foreach (var vector in simplex)
{
for (int j = 0; j < centroid.Length; j++)
{
centroid[j] += vector[j];
}
}
for (int j = 0; j < centroid.Length; j++)
{
centroid[j] /= simplex.Length;
}
// reflection
RealVector reflectionPoint = new RealVector(bestSol.Length);
for (int j = 0; j < reflectionPoint.Length; j++)
{
reflectionPoint[j] = centroid[j] + Alpha.Value * (centroid[j] - simplex[simplex.Length - 1][j]);
}
double reflectionPointQuality = evaluator.Evaluate(reflectionPoint);
if (evaluator.Evaluate(simplex[0]) <= reflectionPointQuality &&
reflectionPointQuality < evaluator.Evaluate(simplex[simplex.Length - 2]))
{
simplex[simplex.Length - 1] = reflectionPoint;
}
// expansion
if (reflectionPointQuality < evaluator.Evaluate(simplex[0]))
{
RealVector expansionPoint = new RealVector(bestSol.Length);
for (int j = 0; j < expansionPoint.Length; j++)
{
expansionPoint[j] = centroid[j] + Beta.Value * (reflectionPoint[j] - centroid[j]);
}
simplex[simplex.Length - 1] = evaluator.Evaluate(expansionPoint) < reflectionPointQuality ? expansionPoint : reflectionPoint;
}
// contraction
if (evaluator.Evaluate(simplex[simplex.Length - 2]) <= reflectionPointQuality &&
reflectionPointQuality < evaluator.Evaluate(simplex[simplex.Length - 1]))
{
RealVector outsideContractionPoint = new RealVector(bestSol.Length);
for (int j = 0; j < outsideContractionPoint.Length; j++)
{
outsideContractionPoint[j] = centroid[j] + Gamma.Value * (reflectionPoint[j] - centroid[j]);
}
if (evaluator.Evaluate(outsideContractionPoint) <= reflectionPointQuality)
{
simplex[simplex.Length - 1] = outsideContractionPoint;
if (evaluator.Evaluate(reflectionPoint) >= evaluator.Evaluate(simplex[simplex.Length - 1]))
{
RealVector insideContractionPoint = new RealVector(bestSol.Length);
for (int j = 0; j < insideContractionPoint.Length; j++)
{
insideContractionPoint[j] = centroid[j] - Gamma.Value * (reflectionPoint[j] - centroid[j]);
}
if (evaluator.Evaluate(insideContractionPoint) < evaluator.Evaluate(simplex[simplex.Length - 1]))
{
simplex[simplex.Length - 1] = insideContractionPoint;
}
}
}
}
// reduction
for (int j = 1; j < simplex.Length; j++)
{
for (int k = 0; k < simplex[j].Length; k++)
{
simplex[j][k] = simplex[0][k] + Delta.Value * (simplex[j][k] - simplex[0][k]);
}
}
}
for (int i = 0; i < simplex[0].Length; i++)
{
if (simplex[0][i] > Bounds[0, 1])
{
simplex[0][i] = Bounds[0, 1];
}
if (simplex[0][i] < Bounds[0, 0])
{
simplex[0][i] = Bounds[0, 0];
}
}
CurrentScope.Variables[SolutionParameter.ActualName].Value = simplex[0];
CurrentScope.Variables.Add(new Variable("LocalEvaluatedSolutions", ImprovementAttempts));
return(base.Apply());
}
