private Node merge(Node node, Node other) {
if (node == null) {
return copyRecursive(other);
} else if (other == null) {
return node;
} else if (!inSameSubtree(node.bits, other.bits, Math.max(node.level, other.level))) {
return makeSiblings(node, copyRecursive(other));
} else if (node.level > other.level) {
long branch = other.bits & node.getBranchMask();
if (branch == 0) {
node.left = merge(node.left, other);
} else {
node.right = merge(node.right, other);
}
return node;
} else if (node.level < other.level) {
Node result = createNode(other.bits, other.level, other.weightedCount);
long branch = node.bits & other.getBranchMask();
if (branch == 0) {
result.left = merge(node, other.left);
result.right = copyRecursive(other.right);
} else {
result.left = copyRecursive(other.left);
result.right = merge(node, other.right);
}
return result;
}
// else, they must be at the same level and on the same path, so just bump the counts
double oldWeight = node.weightedCount;
weightedCount += other.weightedCount;
node.weightedCount = node.weightedCount + other.weightedCount;
node.left = merge(node.left, other.left);
node.right = merge(node.right, other.right);
if (oldWeight < ZERO_WEIGHT_THRESHOLD && node.weightedCount >= ZERO_WEIGHT_THRESHOLD) {
nonZeroNodeCount++;
}
return node;
}
private Node makeSiblings(Node node, Node sibling) {
int parentLevel = MAX_BITS - Long.numberOfLeadingZeros(node.bits ^ sibling.bits);
Node parent = createNode(node.bits, parentLevel, 0);
// the branch is given by the bit at the level one below parent
long branch = sibling.bits & parent.getBranchMask();
if (branch == 0) {
parent.left = sibling;
parent.right = node;
} else {
parent.left = node;
parent.right = sibling;
}
return parent;
}
private void insert(long bits, double weight) {
long lastBranch = 0;
Node parent = null;
Node current = root;
while (true) {
if (current == null) {
setChild(parent, lastBranch, createLeaf(bits, weight));
return;
} else if (!inSameSubtree(bits, current.bits, current.level)) {
// if bits and node.bits are not in the same branch given node's level,
// insert a parent above them at the point at which branches diverge
setChild(parent, lastBranch, makeSiblings(current, createLeaf(bits, weight)));
return;
} else if (current.level == 0 && current.bits == bits) {
// found the node
double oldWeight = current.weightedCount;
current.weightedCount += weight;
if (current.weightedCount >= ZERO_WEIGHT_THRESHOLD && oldWeight < ZERO_WEIGHT_THRESHOLD) {
++nonZeroNodeCount;
}
weightedCount += weight;
return;
}
// we're on the correct branch of the tree and we haven't reached a leaf, so keep going down
long branch = bits & current.getBranchMask();
parent = current;
lastBranch = branch;
if (branch == 0) {
current = current.left;
} else {
current = current.right;
}
}
}