com.clearspring.analytics.stream.cardinality

Class LogLog

java.lang.Object

com.clearspring.analytics.stream.cardinality.LogLog

All Implemented Interfaces:

ICardinality

Direct Known Subclasses:

AdaptiveCounting

public class LogLog
extends Object
implements ICardinality

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	LogLog.Builder
protected static class	LogLog.LogLogMergeException

Field Summary

Fields

Modifier and Type	Field and Description
protected double	Ca
protected int	k
protected int	m
protected byte[]	M
protected static double[]	mAlpha Gamma function computed using SciLab ((gamma(-(m.^(-1))).* ( (1-2.^(m.^(-1)))./log(2) )).^(-m)).*m
protected int	Rsum

Constructor Summary

Constructors

Constructor and Description
LogLog(byte[] M)
LogLog(int k)

Method Summary

Methods

Modifier and Type	Method and Description
long	cardinality()
byte[]	getBytes()
ICardinality	merge(ICardinality... estimators) Merges estimators to produce a new estimator for the combined streams of this estimator and those passed as arguments.
static LogLog	mergeEstimators(LogLog... estimators) Merges estimators to produce an estimator for their combined streams
boolean	offer(Object o)
boolean	offerHashed(int hashedInt) Offer the value as a hashed long value
boolean	offerHashed(long hashedLong) Offer the value as a hashed long value
protected static int	rho(int x, int k) Computes the position of the first set bit of the last Integer.SIZE-k bits
int	sizeof()

Methods inherited from class java.lang.Object

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

Field Detail

mAlpha

protected static final double[] mAlpha

Gamma function computed using SciLab ((gamma(-(m.^(-1))).* ( (1-2.^(m.^(-1)))./log(2) )).^(-m)).*m

k

protected final int k

m

protected int m

Ca

protected double Ca

M

protected byte[] M

Rsum

protected int Rsum

Constructor Detail

LogLog

public LogLog(int k)

LogLog

public LogLog(byte[] M)

Method Detail

getBytes

public byte[] getBytes()

Specified by:

getBytes in interface ICardinality

Returns:

sizeof

public int sizeof()

Specified by:

sizeof in interface ICardinality

Returns:

size in bytes needed for serialization

cardinality

public long cardinality()

Specified by:

cardinality in interface ICardinality

Returns:

the number of unique elements in the stream or an estimate thereof

offerHashed

public boolean offerHashed(long hashedLong)

Description copied from interface: ICardinality

Offer the value as a hashed long value

Specified by:

offerHashed in interface ICardinality

Parameters:

hashedLong - - the hash of the item to offer to the estimator

Returns:

false if the value returned by cardinality() is unaffected by the appearance of hashedLong in the stream

offerHashed

public boolean offerHashed(int hashedInt)

Description copied from interface: ICardinality

Offer the value as a hashed long value

Specified by:

offerHashed in interface ICardinality

Parameters:

hashedInt - - the hash of the item to offer to the estimator

Returns:

false if the value returned by cardinality() is unaffected by the appearance of hashedInt in the stream

offer

public boolean offer(Object o)

Specified by:

offer in interface ICardinality

Parameters:

o - stream element

Returns:

false if the value returned by cardinality() is unaffected by the appearance of o in the stream.

rho

protected static int rho(int x,
      int k)

Computes the position of the first set bit of the last Integer.SIZE-k bits

Returns:

Integer.SIZE-k if the last k bits are all zero

merge

public ICardinality merge(ICardinality... estimators)
                   throws LogLog.LogLogMergeException

Description copied from interface: ICardinality

Merges estimators to produce a new estimator for the combined streams of this estimator and those passed as arguments. Nor this estimator nor the one passed as parameters are modified.

Specified by:

merge in interface ICardinality

Parameters:

estimators - Zero or more compatible estimators

Returns:

this if estimators is null or no arguments are passed

Throws:

LogLog.LogLogMergeException - if estimators are not mergeable (all estimators must be instances of LogLog of the same size)

mergeEstimators

public static LogLog mergeEstimators(LogLog... estimators)
                              throws LogLog.LogLogMergeException

Merges estimators to produce an estimator for their combined streams

Parameters:

estimators -

Returns:

merged estimator or null if no estimators were provided

Throws:

LogLog.LogLogMergeException - if estimators are not mergeable (all estimators must be the same size)