public override IOperation InstrumentedApply()
{
var trees = SymbolicExpressionTreeParameter.ActualValue;
var similarityMatrix = SymbolicExpressionTreeHash.ComputeSimilarityMatrix(trees, false, StrictSimilarity);
DoubleValue averageSimilarity(int i) => new DoubleValue(Enumerable.Range(0, trees.Length).Where(j => i != j).Average(j => similarityMatrix[i, j]));
AverageSimilarityParameter.ActualValue = new ItemArray <DoubleValue>(Enumerable.Range(0, trees.Length).Select(averageSimilarity));
return(base.InstrumentedApply());
}
protected override IScope[] Select(List <IScope> scopes)
{
var w = SimilarityWeight;
if (w.IsAlmost(0))
{
ApplyInnerSelector();
return(CurrentScope.SubScopes[1].SubScopes.ToArray()); // return selected individuals (selectors create two sub-scopes with remaining and selected)
}
var trees = SymbolicExpressionTreeParameter.ActualValue;
var qualities = QualityParameter.ActualValue;
// calculate average similarity for each tree
var similarityMatrix = SymbolicExpressionTreeHash.ComputeSimilarityMatrix(trees, simplify: false, strict: StrictSimilarity);
var similarities = new double[trees.Length];
for (int i = 0; i < trees.Length; ++i)
{
for (int j = 0; j < trees.Length; ++j)
{
if (i != j)
{
similarities[i] += similarityMatrix[i, j];
}
}
similarities[i] /= (trees.Length - 1);
}
var v = 1 - w;
var maximization = MaximizationParameter.ActualValue.Value;
var diversities = new ItemArray <DoubleValue>(trees.Length);
for (int i = 0; i < trees.Length; ++i)
{
var q = qualities[i].Value;
var d = 1 - similarities[i]; // average distance
// assuming both q and d are in the interval [0, 1]
var value = maximization
? (v * q) + (w * d)
: (v * q) - (w * d);
diversities[i] = new DoubleValue(value);
}
Selector.QualityParameter.ActualName = "Diversity";
DiversityParameter.ActualValue = diversities;
ApplyInnerSelector(); // apply inner selector
return(CurrentScope.SubScopes[1].SubScopes.ToArray());
}
