/// <summary>
/// Crossover operator.
/// </summary>
///
/// <param name="pair">Pair chromosome to crossover with.</param>
///
/// <remarks><para>The method performs crossover between two chromosomes ?interchanging
/// randomly selected sub trees.</para></remarks>
///
public override void Crossover(IChromosome pair)
{
GPTreeChromosome p = (GPTreeChromosome)pair;
// check for correct pair
if (p != null)
{
// do we need to use root node for crossover ?
if ((root.Children == null) || (rand.Next(maxLevel) == 0))
{
// give the root to the pair and use pair's part as a new root
root = p.RandomSwap(root);
}
else
{
GPTreeNode node = root;
for ( ; ;)
{
// choose random child
int r = rand.Next(node.Gene.ArgumentsCount);
GPTreeNode child = (GPTreeNode)node.Children[r];
// swap the random node, if it is an end node or
// random generator "selected" this node
if ((child.Children == null) || (rand.Next(maxLevel) == 0))
{
// swap the node with pair's one
node.Children[r] = p.RandomSwap(child);
break;
}
// go further by tree
node = child;
}
}
// trim both of them
Trim(root, maxLevel);
Trim(p.root, maxLevel);
}
}
/// <summary>
/// Initializes a new instance of the <see cref="GPTreeChromosome"/> class.
/// </summary>
///
/// <param name="source">Source genetic tree to clone from.</param>
///
/// <remarks><para>This constructor creates new genetic tree as a copy of the
/// specified <paramref name="source"/> tree.</para></remarks>
///
protected GPTreeChromosome(GPTreeChromosome source)
{
root = (GPTreeNode)source.root.Clone( );
fitness = source.fitness;
}