org.apache.hadoop.util.bloom
Class DynamicBloomFilter

java.lang.Object
  org.apache.hadoop.util.bloom.Filter
      org.apache.hadoop.util.bloom.DynamicBloomFilter

All Implemented Interfaces:

Writable

public class DynamicBloomFilter
extends Filter

Implements a dynamic Bloom filter, as defined in the INFOCOM 2006 paper.

A dynamic Bloom filter (DBF) makes use of a s * m bit matrix but each of the s rows is a standard Bloom filter. The creation process of a DBF is iterative. At the start, the DBF is a 1 * m bit matrix, i.e., it is composed of a single standard Bloom filter. It assumes that nr elements are recorded in the initial bit vector, where nr <= n (n is the cardinality of the set A to record in the filter).

As the size of A grows during the execution of the application, several keys must be inserted in the DBF. When inserting a key into the DBF, one must first get an active Bloom filter in the matrix. A Bloom filter is active when the number of recorded keys, nr, is strictly less than the current cardinality of A, n. If an active Bloom filter is found, the key is inserted and nr is incremented by one. On the other hand, if there is no active Bloom filter, a new one is created (i.e., a new row is added to the matrix) according to the current size of A and the element is added in this new Bloom filter and the nr value of this new Bloom filter is set to one. A given key is said to belong to the DBF if the k positions are set to one in one of the matrix rows.

Originally created by European Commission One-Lab Project 034819.

See Also:

The general behavior of a filter, A Bloom filter, Theory and Network Applications of Dynamic Bloom Filters

Field Summary

Fields inherited from class org.apache.hadoop.util.bloom.Filter

hash, hashType, nbHash, vectorSize

Constructor Summary

DynamicBloomFilter()
Zero-args constructor for the serialization.

DynamicBloomFilter(int vectorSize, int nbHash, int hashType, int nr)
Constructor.

Method Summary

void	add(Key key) Adds a key to this filter.
void	and(Filter filter) Peforms a logical AND between this filter and a specified filter.
boolean	membershipTest(Key key) Determines wether a specified key belongs to this filter.
void	not() Performs a logical NOT on this filter.
void	or(Filter filter) Peforms a logical OR between this filter and a specified filter.
void	readFields(DataInput in) Deserialize the fields of this object from in.
String	toString()
void	write(DataOutput out) Serialize the fields of this object to out.
void	xor(Filter filter) Peforms a logical XOR between this filter and a specified filter.

Methods inherited from class org.apache.hadoop.util.bloom.Filter

add, add, add

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

DynamicBloomFilter

public DynamicBloomFilter()

Zero-args constructor for the serialization.

DynamicBloomFilter

public DynamicBloomFilter(int vectorSize,
                          int nbHash,
                          int hashType,
                          int nr)

Constructor.

Builds an empty Dynamic Bloom filter.

Parameters:

vectorSize - The number of bits in the vector.

nbHash - The number of hash function to consider.

hashType - type of the hashing function (see Hash).

nr - The threshold for the maximum number of keys to record in a dynamic Bloom filter row.

Method Detail

add

public void add(Key key)

Description copied from class: Filter

Adds a key to this filter.

Specified by:

add in class Filter

Parameters:

key - The key to add.

and

public void and(Filter filter)

Description copied from class: Filter

Peforms a logical AND between this filter and a specified filter.

Invariant: The result is assigned to this filter.

Specified by:

and in class Filter

Parameters:

filter - The filter to AND with.

membershipTest

public boolean membershipTest(Key key)

Description copied from class: Filter

Determines wether a specified key belongs to this filter.

Specified by:

membershipTest in class Filter

Parameters:

key - The key to test.

Returns:

boolean True if the specified key belongs to this filter. False otherwise.

not

public void not()

Description copied from class: Filter

Performs a logical NOT on this filter.

The result is assigned to this filter.

Specified by:

not in class Filter

or

public void or(Filter filter)

Description copied from class: Filter

Peforms a logical OR between this filter and a specified filter.

Invariant: The result is assigned to this filter.

Specified by:

or in class Filter

Parameters:

filter - The filter to OR with.

xor

public void xor(Filter filter)

Description copied from class: Filter

Peforms a logical XOR between this filter and a specified filter.

Invariant: The result is assigned to this filter.

Specified by:

xor in class Filter

Parameters:

filter - The filter to XOR with.

toString

public String toString()

Overrides:

toString in class Object

write

public void write(DataOutput out)
           throws IOException

Description copied from interface: Writable

Serialize the fields of this object to out.

Specified by:

write in interface Writable

Overrides:

write in class Filter

Parameters:

out - DataOuput to serialize this object into.

Throws:

IOException

readFields

public void readFields(DataInput in)
                throws IOException

Description copied from interface: Writable

Deserialize the fields of this object from in.

For efficiency, implementations should attempt to re-use storage in the existing object where possible.

Specified by:

readFields in interface Writable

Overrides:

readFields in class Filter

Parameters:

in - DataInput to deseriablize this object from.

Throws:

IOException