/*
* Copyright (c) 2008-2017, Hazelcast, Inc. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.hazelcast.cardinality.impl.hyperloglog;
import com.hazelcast.nio.serialization.IdentifiedDataSerializable;
/**
* HyperLogLog is a redundant and highly available distributed data-structure used for cardinality estimation
* purposes on unique items in significantly sized data cultures. HyperLogLog uses P^2 byte registers for storage
* and computation.
*
* HyperLogLog is an implementation of the two famous papers
* <ul>
* <li>http://algo.inria.fr/flajolet/Publications/FlFuGaMe07.pdf</li>
* <li>http://static.googleusercontent.com/media/research.google.com/en//pubs/archive/40671.pdf</li>
* </ul>
*
*/
public interface HyperLogLog extends IdentifiedDataSerializable {
/**
* Computes a new estimate for the current status of the registers.
* If it was previously estimated and never invalidated, then a cached version is used.
*
* @return previously cached estimation or a newly computed one.
*/
long estimate();
/**
* Aggregates the hash in the HyperLogLog registers.
*
* @param hash the value to aggregate
*/
void add(long hash);
/**
* Batch aggregation of hash values in the HyperLogLog registers.
*
* @param hashes the hash values array to aggregate
*/
void addAll(long[] hashes);
}