protected void continueAttemptToSplit()

in samoa-api/src/main/java/org/apache/samoa/learners/classifiers/trees/ModelAggregatorProcessor.java [472:535]
47 lines of code
12 McCabe index (conditional complexity)

  protected void continueAttemptToSplit(ActiveLearningNode activeLearningNode, FoundNode foundNode) {
    AttributeSplitSuggestion bestSuggestion = activeLearningNode.getDistributedBestSuggestion();
    AttributeSplitSuggestion secondBestSuggestion = activeLearningNode.getDistributedSecondBestSuggestion();

    // compare with null split
    double[] preSplitDist = activeLearningNode.getObservedClassDistribution();
    AttributeSplitSuggestion nullSplit = new AttributeSplitSuggestion(null, new double[0][],
        this.splitCriterion.getMeritOfSplit(preSplitDist, new double[][] { preSplitDist }));

    if ((bestSuggestion == null) || (nullSplit.compareTo(bestSuggestion) > 0)) {
      secondBestSuggestion = bestSuggestion;
      bestSuggestion = nullSplit;
    } else {
      if ((secondBestSuggestion == null) || (nullSplit.compareTo(secondBestSuggestion) > 0)) {
        secondBestSuggestion = nullSplit;
      }
    }

    boolean shouldSplit = false;

    if (secondBestSuggestion == null) {
      shouldSplit = true;
    } else {
      double hoeffdingBound = computeHoeffdingBound(
          this.splitCriterion.getRangeOfMerit(activeLearningNode.getObservedClassDistribution()), this.splitConfidence,
          activeLearningNode.getWeightSeen());

      if ((bestSuggestion.merit - secondBestSuggestion.merit > hoeffdingBound) || (hoeffdingBound < tieThreshold)) {
        shouldSplit = true;
      }
      // TODO: add poor attributes removal
    }

    SplitNode parent = foundNode.getParent();
    int parentBranch = foundNode.getParentBranch();

    // split if the Hoeffding bound condition is satisfied
    if (shouldSplit) {

      if (bestSuggestion.splitTest != null) {
        SplitNode newSplit = new SplitNode(bestSuggestion.splitTest, activeLearningNode.getObservedClassDistribution());

        for (int i = 0; i < bestSuggestion.numSplits(); i++) {
          Node newChild = newLearningNode(bestSuggestion.resultingClassDistributionFromSplit(i), this.parallelismHint);
          newSplit.setChild(i, newChild);
        }

        this.activeLeafNodeCount--;
        this.decisionNodeCount++;
        this.activeLeafNodeCount += bestSuggestion.numSplits();

        if (parent == null) {
          this.treeRoot = newSplit;
        } else {
          parent.setChild(parentBranch, newSplit);
        }
      }
      // TODO: add check on the model's memory size
    }

    // housekeeping
    activeLearningNode.endSplitting();
    activeLearningNode.setWeightSeenAtLastSplitEvaluation(activeLearningNode.getWeightSeen());
  }