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HyperLogLog.add() have a return value. #59

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HyperLogLog.add() have a return value. #59

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4f5d02f
HyperLogLog.add() have a return value.
pocorall May 13, 2019
a06655d
properties of HyperLogLog become protected.
pocorall May 13, 2019
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15 changes: 9 additions & 6 deletions stats/src/main/java/com/facebook/stats/cardinality/HyperLogLog.java
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Original file line number Diff line number Diff line change
Expand Up @@ -28,12 +28,12 @@
*/
@NotThreadSafe
public class HyperLogLog {
private final byte[] buckets;
protected final byte[] buckets;

// The current sum of 1 / (1L << buckets[i]). Updated as new items are added and used for
// estimation
private double currentSum;
private int nonZeroBuckets = 0;
protected double currentSum;
protected int nonZeroBuckets = 0;

public HyperLogLog(int numberOfBuckets) {
Preconditions.checkArgument(
Expand Down Expand Up @@ -66,12 +66,13 @@ public HyperLogLog(int[] buckets) {
}
}

public void add(long value) {
/**
* @return true if the buckets are updated
*/
public boolean add(long value) {
BucketAndHash bucketAndHash = BucketAndHash.fromHash(computeHash(value), buckets.length);
int bucket = bucketAndHash.getBucket();

int lowestBitPosition = Long.numberOfTrailingZeros(bucketAndHash.getHash()) + 1;

int previous = buckets[bucket];

if (previous == 0) {
Expand All @@ -83,7 +84,9 @@ public void add(long value) {
currentSum += 1.0 / (1L << lowestBitPosition);

buckets[bucket] = (byte) lowestBitPosition;
return true;
}
return false;
}

public long estimate() {
Expand Down