private static void Mutate(List <string> genes, IReadOnlyList <string> numbers, IReadOnlyList <string> operations, int minNumbers,
int maxNumbers, FnFitnessDelegate fnGetFitness)
{
var count = Rand.Random.Next(1, 10);
var initialFitness = fnGetFitness(genes);
while (count > 0)
{
count--;
if (fnGetFitness(genes) > initialFitness)
{
return;
}
var numberCount = (1 + genes.Count) / 2;
var adding = numberCount < maxNumbers && Rand.PercentChance(1);
if (adding)
{
genes.Add(Rand.SelectItem(operations));
genes.Add(Rand.SelectItem(numbers));
continue;
}
var removing = numberCount > minNumbers && Rand.PercentChance(5);
if (removing)
{
var index = Rand.Random.Next(0, genes.Count - 1);
genes.RemoveAt(index);
genes.RemoveAt(index);
continue;
}
var index2 = Rand.Random.Next(0, genes.Count);
genes[index2] = (index2 & 1) == 1
? Rand.SelectItem(operations)
: Rand.SelectItem(numbers);
}
}
private static int GetFitness(IReadOnlyList <string> genes, int expectedTotal, FnFitnessDelegate fnEvaluate)
{
try
{
var result = fnEvaluate(genes);
var fitness = result != expectedTotal
? expectedTotal - Math.Abs(result - expectedTotal)
: 1000 - genes.Count;
return(fitness);
}
catch (OverflowException)
{
return(1000);
}
}
