presto-main/src/main/java/io/prestosql/operator/aggregation/ApproximateCountDistinctAggregation.java/ApproximateCountDistinctAggregation/log2Ceiling
class ApproximateCountDistinctAggregation:    private static int log2Ceiling(int value)
    {
        return Integer.highestOneBit(value - 1) << 1;
    }