public static QuantileDigest merge(List<QuantileDigest> digests) {
if (digests.isEmpty()) {
throw new RuntimeException("Digests to be unioned should not be empty!");
}
QuantileDigest ret = digests.get(0);
for (int i = 1; i < digests.size(); i++) {
ret.merge(digests.get(i));
}
return ret;
}
private void rescaleToCommonLandmark(QuantileDigest one, QuantileDigest two) {
long nowInSeconds = TimeUnit.NANOSECONDS.toSeconds(ticker.read());
// 1. rescale this and other to common landmark
long targetLandmark = Math.max(one.landmarkInSeconds, two.landmarkInSeconds);
if (nowInSeconds - targetLandmark >= RESCALE_THRESHOLD_SECONDS) {
targetLandmark = nowInSeconds;
}
if (targetLandmark != one.landmarkInSeconds) {
one.rescale(targetLandmark);
}
if (targetLandmark != two.landmarkInSeconds) {
two.rescale(targetLandmark);
}
}
public static QuantileDigest deserialize(DataInput input) {
try {
double maxError = input.readDouble();
double alpha = input.readDouble();
QuantileDigest result = new QuantileDigest(maxError, alpha);
result.landmarkInSeconds = input.readLong();
result.min = input.readLong();
result.max = input.readLong();
result.totalNodeCount = input.readInt();
Deque<Node> stack = new ArrayDeque<>();
for (int i = 0; i < result.totalNodeCount; i++) {
int flags = input.readByte();
Node node = deserializeNode(input);
if ((flags & Flags.HAS_RIGHT) != 0) {
node.right = stack.pop();
}
if ((flags & Flags.HAS_LEFT) != 0) {
node.left = stack.pop();
}
stack.push(node);
result.weightedCount += node.weightedCount;
if (node.weightedCount >= ZERO_WEIGHT_THRESHOLD) {
result.nonZeroNodeCount++;
}
}
if (!stack.isEmpty()) {
Preconditions.checkArgument(
stack.size() == 1, "Tree is corrupted. Expected a single root node");
result.root = stack.pop();
}
return result;
} catch (IOException e) {
throw Throwables.propagate(e);
}
}
public static QuantileDigest build(DataInput buf) throws IOException {
return QuantileDigest.deserialize(buf);
}
@Override
public void writeExternal(ObjectOutput out) throws IOException {
holder.writeBytes(out);
}
public QuantileDigest(QuantileDigest quantileDigest) {
this(quantileDigest.getMaxError(), quantileDigest.getAlpha());
merge(quantileDigest);
}
