/**
*
* Copyright (c) 2005, European Commission project OneLab under contract 034819 (http://www.one-lab.org)
* All rights reserved.
* Redistribution and use in source and binary forms, with or
* without modification, are permitted provided that the following
* conditions are met:
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the distribution.
* - Neither the name of the University Catholique de Louvain - UCL
* nor the names of its contributors may be used to endorse or
* promote products derived from this software without specific prior
* written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* POSSIBILITY OF SUCH DAMAGE.
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/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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
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package org.apache.hadoop.util.bloom;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Random;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
/**
* Implements a <i>retouched Bloom filter</i>, as defined in the CoNEXT 2006 paper.
* <p>
* It allows the removal of selected false positives at the cost of introducing
* random false negatives, and with the benefit of eliminating some random false
* positives at the same time.
*
* <p>
* Originally created by
* <a href="http://www.one-lab.org">European Commission One-Lab Project 034819</a>.
*
* @see Filter The general behavior of a filter
* @see BloomFilter A Bloom filter
* @see RemoveScheme The different selective clearing algorithms
*
* @see <a href="http://www-rp.lip6.fr/site_npa/site_rp/_publications/740-rbf_cameraready.pdf">Retouched Bloom Filters: Allowing Networked Applications to Trade Off Selected False Positives Against False Negatives</a>
*/
@InterfaceAudience.Public
@InterfaceStability.Stable
public final class RetouchedBloomFilter extends BloomFilter
implements RemoveScheme {
/**
* KeyList vector (or ElementList Vector, as defined in the paper) of false positives.
*/
List<Key>[] fpVector;
/**
* KeyList vector of keys recorded in the filter.
*/
List<Key>[] keyVector;
/**
* Ratio vector.
*/
double[] ratio;
private Random rand;
/** Default constructor - use with readFields */
public RetouchedBloomFilter() {}
/**
* Constructor
* @param vectorSize The vector size of <i>this</i> filter.
* @param nbHash The number of hash function to consider.
* @param hashType type of the hashing function (see
* {@link org.apache.hadoop.util.hash.Hash}).
*/
public RetouchedBloomFilter(int vectorSize, int nbHash, int hashType) {
super(vectorSize, nbHash, hashType);
this.rand = null;
createVector();
}
@Override
public void add(Key key) {
if (key == null) {
throw new NullPointerException("key can not be null");
}
int[] h = hash.hash(key);
hash.clear();
for (int i = 0; i < nbHash; i++) {
bits.set(h[i]);
keyVector[h[i]].add(key);
}
}
/**
* Adds a false positive information to <i>this</i> retouched Bloom filter.
* <p>
* <b>Invariant</b>: if the false positive is <code>null</code>, nothing happens.
* @param key The false positive key to add.
*/
public void addFalsePositive(Key key) {
if (key == null) {
throw new NullPointerException("key can not be null");
}
int[] h = hash.hash(key);
hash.clear();
for (int i = 0; i < nbHash; i++) {
fpVector[h[i]].add(key);
}
}
/**
* Adds a collection of false positive information to <i>this</i> retouched Bloom filter.
* @param coll The collection of false positive.
*/
public void addFalsePositive(Collection<Key> coll) {
if (coll == null) {
throw new NullPointerException("Collection<Key> can not be null");
}
for (Key k : coll) {
addFalsePositive(k);
}
}
/**
* Adds a list of false positive information to <i>this</i> retouched Bloom filter.
* @param keys The list of false positive.
*/
public void addFalsePositive(List<Key> keys) {
if (keys == null) {
throw new NullPointerException("ArrayList<Key> can not be null");
}
for (Key k : keys) {
addFalsePositive(k);
}
}
/**
* Adds an array of false positive information to <i>this</i> retouched Bloom filter.
* @param keys The array of false positive.
*/
public void addFalsePositive(Key[] keys) {
if (keys == null) {
throw new NullPointerException("Key[] can not be null");
}
for (int i = 0; i < keys.length; i++) {
addFalsePositive(keys[i]);
}
}
/**
* Performs the selective clearing for a given key.
* @param k The false positive key to remove from <i>this</i> retouched Bloom filter.
* @param scheme The selective clearing scheme to apply.
*/
public void selectiveClearing(Key k, short scheme) {
if (k == null) {
throw new NullPointerException("Key can not be null");
}
if (!membershipTest(k)) {
throw new IllegalArgumentException("Key is not a member");
}
int index = 0;
int[] h = hash.hash(k);
switch(scheme) {
case RANDOM:
index = randomRemove();
break;
case MINIMUM_FN:
index = minimumFnRemove(h);
break;
case MAXIMUM_FP:
index = maximumFpRemove(h);
break;
case RATIO:
index = ratioRemove(h);
break;
default:
throw new AssertionError("Undefined selective clearing scheme");
}
clearBit(index);
}
private int randomRemove() {
if (rand == null) {
rand = new Random();
}
return rand.nextInt(nbHash);
}
/**
* Chooses the bit position that minimizes the number of false negative generated.
* @param h The different bit positions.
* @return The position that minimizes the number of false negative generated.
*/
private int minimumFnRemove(int[] h) {
int minIndex = Integer.MAX_VALUE;
double minValue = Double.MAX_VALUE;
for (int i = 0; i < nbHash; i++) {
double keyWeight = getWeight(keyVector[h[i]]);
if (keyWeight < minValue) {
minIndex = h[i];
minValue = keyWeight;
}
}
return minIndex;
}
/**
* Chooses the bit position that maximizes the number of false positive removed.
* @param h The different bit positions.
* @return The position that maximizes the number of false positive removed.
*/
private int maximumFpRemove(int[] h) {
int maxIndex = Integer.MIN_VALUE;
double maxValue = Double.MIN_VALUE;
for (int i = 0; i < nbHash; i++) {
double fpWeight = getWeight(fpVector[h[i]]);
if (fpWeight > maxValue) {
maxValue = fpWeight;
maxIndex = h[i];
}
}
return maxIndex;
}
/**
* Chooses the bit position that minimizes the number of false negative generated while maximizing.
* the number of false positive removed.
* @param h The different bit positions.
* @return The position that minimizes the number of false negative generated while maximizing.
*/
private int ratioRemove(int[] h) {
computeRatio();
int minIndex = Integer.MAX_VALUE;
double minValue = Double.MAX_VALUE;
for (int i = 0; i < nbHash; i++) {
if (ratio[h[i]] < minValue) {
minValue = ratio[h[i]];
minIndex = h[i];
}
}
return minIndex;
}
/**
* Clears a specified bit in the bit vector and keeps up-to-date the KeyList vectors.
* @param index The position of the bit to clear.
*/
private void clearBit(int index) {
if (index < 0 || index >= vectorSize) {
throw new ArrayIndexOutOfBoundsException(index);
}
List<Key> kl = keyVector[index];
List<Key> fpl = fpVector[index];
// update key list
int listSize = kl.size();
for (int i = 0; i < listSize && !kl.isEmpty(); i++) {
removeKey(kl.get(0), keyVector);
}
kl.clear();
keyVector[index].clear();
//update false positive list
listSize = fpl.size();
for (int i = 0; i < listSize && !fpl.isEmpty(); i++) {
removeKey(fpl.get(0), fpVector);
}
fpl.clear();
fpVector[index].clear();
//update ratio
ratio[index] = 0.0;
//update bit vector
bits.clear(index);
}
/**
* Removes a given key from <i>this</i> filer.
* @param k The key to remove.
* @param vector The counting vector associated to the key.
*/
private void removeKey(Key k, List<Key>[] vector) {
if (k == null) {
throw new NullPointerException("Key can not be null");
}
if (vector == null) {
throw new NullPointerException("ArrayList<Key>[] can not be null");
}
int[] h = hash.hash(k);
hash.clear();
for (int i = 0; i < nbHash; i++) {
vector[h[i]].remove(k);
}
}
/**
* Computes the ratio A/FP.
*/
private void computeRatio() {
for (int i = 0; i < vectorSize; i++) {
double keyWeight = getWeight(keyVector[i]);
double fpWeight = getWeight(fpVector[i]);
if (keyWeight > 0 && fpWeight > 0) {
ratio[i] = keyWeight / fpWeight;
}
}
}
private double getWeight(List<Key> keyList) {
double weight = 0.0;
for (Key k : keyList) {
weight += k.getWeight();
}
return weight;
}
/**
* Creates and initialises the various vectors.
*/
@SuppressWarnings("unchecked")
private void createVector() {
fpVector = new List[vectorSize];
keyVector = new List[vectorSize];
ratio = new double[vectorSize];
for (int i = 0; i < vectorSize; i++) {
fpVector[i] = Collections.synchronizedList(new ArrayList<Key>());
keyVector[i] = Collections.synchronizedList(new ArrayList<Key>());
ratio[i] = 0.0;
}
}
// Writable
@Override
public void write(DataOutput out) throws IOException {
super.write(out);
for (int i = 0; i < fpVector.length; i++) {
List<Key> list = fpVector[i];
out.writeInt(list.size());
for (Key k : list) {
k.write(out);
}
}
for (int i = 0; i < keyVector.length; i++) {
List<Key> list = keyVector[i];
out.writeInt(list.size());
for (Key k : list) {
k.write(out);
}
}
for (int i = 0; i < ratio.length; i++) {
out.writeDouble(ratio[i]);
}
}
@Override
public void readFields(DataInput in) throws IOException {
super.readFields(in);
createVector();
for (int i = 0; i < fpVector.length; i++) {
List<Key> list = fpVector[i];
int size = in.readInt();
for (int j = 0; j < size; j++) {
Key k = new Key();
k.readFields(in);
list.add(k);
}
}
for (int i = 0; i < keyVector.length; i++) {
List<Key> list = keyVector[i];
int size = in.readInt();
for (int j = 0; j < size; j++) {
Key k = new Key();
k.readFields(in);
list.add(k);
}
}
for (int i = 0; i < ratio.length; i++) {
ratio[i] = in.readDouble();
}
}
}