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java.lang.Objectorg.apache.hadoop.util.bloom.Filter
org.apache.hadoop.util.bloom.DynamicBloomFilter
public class DynamicBloomFilter
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.
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 |
|---|
public DynamicBloomFilter()
public DynamicBloomFilter(int vectorSize,
int nbHash,
int hashType,
int nr)
Builds an empty Dynamic Bloom filter.
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 |
|---|
public void add(Key key)
Filter
add in class Filterkey - The key to add.public void and(Filter filter)
FilterInvariant: The result is assigned to this filter.
and in class Filterfilter - The filter to AND with.public boolean membershipTest(Key key)
Filter
membershipTest in class Filterkey - The key to test.
public void not()
FilterThe result is assigned to this filter.
not in class Filterpublic void or(Filter filter)
FilterInvariant: The result is assigned to this filter.
or in class Filterfilter - The filter to OR with.public void xor(Filter filter)
FilterInvariant: The result is assigned to this filter.
xor in class Filterfilter - The filter to XOR with.public String toString()
toString in class Object
public void write(DataOutput out)
throws IOException
Writableout.
write in interface Writablewrite in class Filterout - DataOuput to serialize this object into.
IOException
public void readFields(DataInput in)
throws IOException
Writablein.
For efficiency, implementations should attempt to re-use storage in the existing object where possible.
readFields in interface WritablereadFields in class Filterin - DataInput to deseriablize this object from.
IOException
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