/// <summary>
/// Computes the reached target leaves for the current tree.
/// </summary>
/// <param name="tree">
/// The tree.
/// </param>
/// <param name="parentGenomes">
/// The parent genomes.
/// </param>
/// <param name="indexSetsForCategoricalFeaturesInDoubleRepresentation">
/// The index sets for categorical features in double representation.
/// (
/// <see cref="GeneticEngineering{TLearnerModel,TPredictorModel,TSamplingStrategy}.ComputeIndexSetsForCategoricalFeaturesInDoubleRepresentation"/>
/// ).
/// </param>
/// <returns>
/// The <see cref="IEnumerable{TreeNodeAndFixations}"/> that conatins all leaf nodes that an offspring of the
/// <paramref name="parentGenomes"/> can fall into.
/// </returns>
public static IEnumerable <TreeNodeAndFixations> ComputeReachableTargetLeavesForTree(
GenomePredictionTree tree,
ParentGenomesConverted parentGenomes,
Dictionary <int, HashSet <int> > indexSetsForCategoricalFeaturesInDoubleRepresentation)
{
if (indexSetsForCategoricalFeaturesInDoubleRepresentation == null)
{
indexSetsForCategoricalFeaturesInDoubleRepresentation = new Dictionary <int, HashSet <int> >(0);
}
var queue = new List <TreeNodeAndFixations> {
new TreeNodeAndFixations(tree.Root, null)
};
var head = 0;
while (head < queue.Count)
{
var currentNodeAndFixations = queue[head++];
var currentNode = currentNodeAndFixations.CurrentNode;
// check if we reached a leaf:
if (currentNode.IsLeafNode())
{
yield return(currentNodeAndFixations.CreateCopy());
continue;
}
var competitiveParentGoesLeft = CheckIfParentGoesLeft(parentGenomes.CompetitiveParent, currentNode);
var nonCompetitiveParentGoesLeft = CheckIfParentGoesLeft(parentGenomes.NonCompetitiveParent, currentNode);
var parentsFollowSamePath = competitiveParentGoesLeft == nonCompetitiveParentGoesLeft;
// no need to fix features
if (parentsFollowSamePath)
{
var childNode = tree.Nodes[competitiveParentGoesLeft ? currentNode.LeftIndex : currentNode.RightIndex];
var childNodeAndFixation = new TreeNodeAndFixations(childNode, currentNodeAndFixations.FixedIndicesInDoubleRepresentation);
queue.Add(childNodeAndFixation);
continue;
}
// we know that parents will take separate paths.
AddTreeNodeAndFixationsIfParentCanContinue(
parentGenomes,
tree,
currentNodeAndFixations,
TargetLeafGenomeFixation.FixedToCompetitiveParent,
indexSetsForCategoricalFeaturesInDoubleRepresentation,
queue);
AddTreeNodeAndFixationsIfParentCanContinue(
parentGenomes,
tree,
currentNodeAndFixations,
TargetLeafGenomeFixation.FixedToNonCompetitiveParent,
indexSetsForCategoricalFeaturesInDoubleRepresentation,
queue);
}
}
/// <summary>
/// Checks if the given <paramref name="parentToCheck"/> can follow the current tree path.
/// </summary>
/// <param name="parents">
/// The converted parent genomes.
/// </param>
/// <param name="tree">
/// The tree.
/// </param>
/// <param name="currentNodeAndFixations">
/// The current node and feature fixations.
/// </param>
/// <param name="parentToCheck">
/// The parent to check.
/// </param>
/// <param name="indexSetsForCategoricalFeaturesInDoubleRepresentation">
/// The index sets for categorical features in double representation.
/// </param>
/// <param name="queue">
/// The queue of open nodes to traverse.
/// If the <paramref name="parentToCheck"/> can continue (i.e. the current node's feature is not fixed to the 'other'
/// parent),
/// the child node that is visited by <paramref name="parentToCheck"/> will be added (and fixed to the
/// <paramref name="parentToCheck"/>).
/// </param>
private static void AddTreeNodeAndFixationsIfParentCanContinue(
ParentGenomesConverted parents,
GenomePredictionTree tree,
TreeNodeAndFixations currentNodeAndFixations,
TargetLeafGenomeFixation parentToCheck,
Dictionary <int, HashSet <int> > indexSetsForCategoricalFeaturesInDoubleRepresentation,
List <TreeNodeAndFixations> queue)
{
var canParentToCheckContinue = CheckIfGenomeCanContinueAlone(currentNodeAndFixations, parentToCheck);
if (!canParentToCheckContinue)
{
return;
}
var currentParent = parents.GetParentToFollow(parentToCheck);
var currentNode = currentNodeAndFixations.CurrentNode;
var parentGoesLeft = CheckIfParentGoesLeft(currentParent, currentNode);
var nextNodeInPath = tree.Nodes[parentGoesLeft ? currentNode.LeftIndex : currentNode.RightIndex];
var competitiveChildNodeAndFixation = new TreeNodeAndFixations(
nextNodeInPath,
currentNodeAndFixations.FixedIndicesInDoubleRepresentation);
// now add fixation
if (!indexSetsForCategoricalFeaturesInDoubleRepresentation.ContainsKey(currentNode.FeatureIndex))
{
competitiveChildNodeAndFixation.FixedIndicesInDoubleRepresentation[currentNode.FeatureIndex] = parentToCheck;
}
else
{
// fix all columns of a feature, when one of them is used for a split.
var allFeatureIndices = indexSetsForCategoricalFeaturesInDoubleRepresentation[currentNode.FeatureIndex];
foreach (var categoricalFeatureIndex in allFeatureIndices)
{
competitiveChildNodeAndFixation.FixedIndicesInDoubleRepresentation[categoricalFeatureIndex] = parentToCheck;
}
}
queue.Add(competitiveChildNodeAndFixation);
}
/// <summary>
/// Checks if parent can continue alone.
/// I.e. the current node's split feature index is not fixed to the 'other' parent.
/// </summary>
/// <param name="currentNodeAndFixations">
/// The current node and fixations.
/// </param>
/// <param name="parentToCheck">
/// The parent to check.
/// </param>
/// <returns>
/// <c>True</c>, iff the current node's split feature index is not fixed to the 'other' parent.
/// </returns>
private static bool CheckIfGenomeCanContinueAlone(TreeNodeAndFixations currentNodeAndFixations, TargetLeafGenomeFixation parentToCheck)
{
var currentFeatureIndex = currentNodeAndFixations.CurrentNode.FeatureIndex;
return(!IsFixedToDifferentGenome(currentFeatureIndex, parentToCheck, currentNodeAndFixations.FixedIndicesInDoubleRepresentation));
}
/// <summary>
/// Initializes a new instance of the <see cref="TreeNodeAndFixations"/> class.
/// Simple copy constructor.
/// </summary>
/// <param name="source">
/// The source to copy from.
/// Must not be null.
/// </param>
private TreeNodeAndFixations(TreeNodeAndFixations source)
: this(source.CurrentNode, source.FixedIndicesInDoubleRepresentation)
{
}
