/// <summary>
/// Choose a random node from the tree. Uses reservoir sampling.
/// </summary>
/// <param name="rnd">Random number generator.</param>
/// <param name="root">The root of the tree.</param>
/// <returns>A random node.</returns>
public RandomNodeResult SampleRandomNode(IGenerateRandom rnd, TreeGenomeNode root)
{
var index = new int[1];
var reservoir = new RandomNodeResult();
index[0] = 0;
InternalSampleRandomNode(rnd, null, root, index, reservoir);
return(reservoir);
}
/// <summary>
///
/// </summary>
/// <param name="rnd"></param>
/// <param name="parent"></param>
/// <param name="current"></param>
/// <param name="index"></param>
/// <param name="reservoir"></param>
private void InternalSampleRandomNode(IGenerateRandom rnd, TreeGenomeNode parent, TreeGenomeNode current,
int[] index, RandomNodeResult reservoir)
{
int currentIndex = index[0];
index[0]++;
// determine if we replace the reservoir
int j = rnd.NextInt(0, currentIndex + 1);
if (j == 0)
{
reservoir.Parent = parent;
reservoir.Child = current;
}
// traverse on to the children
foreach (TreeGenomeNode child in current.Children)
{
InternalSampleRandomNode(rnd, current, child, index, reservoir);
}
}
/// <summary>
///
/// </summary>
/// <param name="rnd"></param>
/// <param name="parent"></param>
/// <param name="current"></param>
/// <param name="index"></param>
/// <param name="reservoir"></param>
private void InternalSampleRandomNode(IGenerateRandom rnd, TreeGenomeNode parent, TreeGenomeNode current,
int[] index, RandomNodeResult reservoir)
{
int currentIndex = index[0];
index[0]++;
// determine if we replace the reservoir
int j = rnd.NextInt(0, currentIndex + 1);
if (j == 0)
{
reservoir.Parent = parent;
reservoir.Child = current;
}
// traverse on to the children
foreach (TreeGenomeNode child in current.Children)
{
InternalSampleRandomNode(rnd, current, child, index, reservoir);
}
}
/// <inheritdoc />
public void PerformOperation(IGenerateRandom rnd, IGenome[] parents, int parentIndex, IGenome[] offspring,
int offspringIndex)
{
var parent1 = (TreeGenome)parents[parentIndex];
EvaluateTree eval = parent1.Evaluator;
var off1 = (TreeGenome)_owner.Population.GenomeFactory.Factor(parent1);
RandomNodeResult off1Point = eval.SampleRandomNode(rnd, off1.Root);
int len = rnd.NextInt(1, _maxGraftLength + 1);
TreeGenomeNode randomSequence = eval.Grow(rnd, len);
if (off1Point.Parent == null)
{
off1.Root = randomSequence;
}
else
{
int idx = off1Point.Parent.Children.IndexOf(off1Point.Child);
off1Point.Parent.Children[idx] = randomSequence;
}
offspring[0] = off1;
}
/// <summary>
/// Choose a random node from the tree. Uses reservoir sampling.
/// </summary>
/// <param name="rnd">Random number generator.</param>
/// <param name="root">The root of the tree.</param>
/// <returns>A random node.</returns>
public RandomNodeResult SampleRandomNode(IGenerateRandom rnd, TreeGenomeNode root)
{
var index = new int[1];
var reservoir = new RandomNodeResult();
index[0] = 0;
InternalSampleRandomNode(rnd, null, root, index, reservoir);
return reservoir;
}
