public void continueAttemptToSplit()

in samoa-api/src/main/java/org/apache/samoa/learners/classifiers/ensemble/BoostMAProcessor.java [169:241]
54 lines of code
15 McCabe index (conditional complexity)

  public void continueAttemptToSplit(ActiveLearningNode bvhtActiveLearningNode, FoundNode foundNode) {
    BoostVHTActiveLearningNode bVHTActiveLearningNode = (BoostVHTActiveLearningNode)bvhtActiveLearningNode;
    AttributeSplitSuggestion bestSuggestion = bVHTActiveLearningNode.getDistributedBestSuggestion();
    AttributeSplitSuggestion secondBestSuggestion = bVHTActiveLearningNode.getDistributedSecondBestSuggestion();

    // compare with null split
    double[] preSplitDist = bVHTActiveLearningNode.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(bVHTActiveLearningNode.getObservedClassDistribution()), this.splitConfidence,
              bVHTActiveLearningNode.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) { // TODO: What happens when bestSuggestion is null? -> Deactivate node?
        SplitNode newSplit = new SplitNode(bestSuggestion.splitTest, bVHTActiveLearningNode.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);
        }
        //if keep w buffer
        if (splittingOption == SplittingOption.KEEP && this.maxBufferSize > 0) {
          Queue<Instance> buffer = bVHTActiveLearningNode.getBuffer();
//          logger.debug("node: {}. split is happening, there are {} items in buffer", activeLearningNode.getId(), buffer.size());
          while (!buffer.isEmpty()) {
            this.trainOnInstanceImpl(buffer.poll());
          }
        }
      }
      // TODO: add check on the model's memory size
    }

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