com.hazelcast.cardinality.impl.hyperloglog.impl

Class SparseHyperLogLogEncoder

java.lang.Object

com.hazelcast.cardinality.impl.hyperloglog.impl.SparseHyperLogLogEncoder

All Implemented Interfaces:

HyperLogLogEncoder, DataSerializable, IdentifiedDataSerializable, Versioned

public class SparseHyperLogLogEncoder
extends Object
implements HyperLogLogEncoder, Versioned

1. http://static.googleusercontent.com/media/research.google.com/en//pubs/archive/40671.pdf

The implementation is using a fixed p' = 25 which according to [1] provides very high accuracy for the range of cardinalities where the sparse representation is used.

Constructor Summary

Constructors

Constructor and Description
SparseHyperLogLogEncoder()

Method Summary

Modifier and Type	Method and Description
boolean	add(long hash) Aggregates the hash value in the HyperLogLog registers, and returns a hint if the operation might have affected the cardinality, it is just a hint, and it relies to the respective implementation.
long	estimate() Computes a new estimate for the current status of the registers.
com.hazelcast.cardinality.impl.hyperloglog.impl.HyperLogLogEncoding	getEncodingType() Returns the encoding type of this instance; see: HyperLogLogEncoding
int	getFactoryId() Returns DataSerializableFactory factory ID for this class.
int	getId() Returns type identifier for this class.
int	getMemoryFootprint() Returns the size in memory occupied (in bytes) for this implementation of HyperLogLog.
void	init(int p, com.hazelcast.cardinality.impl.hyperloglog.impl.SparseHyperLogLogEncoder.VariableLengthDiffArray register)
HyperLogLogEncoder	merge(HyperLogLogEncoder encoder) Merge the two HyperLogLog structures in one.
void	readData(ObjectDataInput in) Reads fields from the input stream
void	writeData(ObjectDataOutput out) Writes object fields to output stream

Methods inherited from class java.lang.Object

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

Constructor Detail

SparseHyperLogLogEncoder

public SparseHyperLogLogEncoder()

Method Detail

init

public void init(int p,
                 com.hazelcast.cardinality.impl.hyperloglog.impl.SparseHyperLogLogEncoder.VariableLengthDiffArray register)

add

public boolean add(long hash)

Description copied from interface: HyperLogLogEncoder

Aggregates the hash value in the HyperLogLog registers, and returns a hint if the operation might have affected the cardinality, it is just a hint, and it relies to the respective implementation.

Specified by:

add in interface HyperLogLogEncoder

Parameters:

hash - the value to aggregate

Returns:

boolean hint, if the latest operation might have affected the cardinality.

estimate

public long estimate()

Description copied from interface: HyperLogLogEncoder

Computes a new estimate for the current status of the registers.

Specified by:

estimate in interface HyperLogLogEncoder

Returns:

a cardinality estimation.

merge

public HyperLogLogEncoder merge(HyperLogLogEncoder encoder)

Description copied from interface: HyperLogLogEncoder

Merge the two HyperLogLog structures in one. Estimations from both are taken into consideration and the unified estimate should be similar to the distinct union set of the two.

Specified by:

merge in interface HyperLogLogEncoder

Parameters:

encoder - The second HLL to be merged into this one

Returns:

HyperLogLogEncoder the union

getFactoryId

public int getFactoryId()

Description copied from interface: IdentifiedDataSerializable

Returns DataSerializableFactory factory ID for this class.

Specified by:

getFactoryId in interface IdentifiedDataSerializable

Returns:

factory ID

getId

public int getId()

Description copied from interface: IdentifiedDataSerializable

Returns type identifier for this class. It should be unique per DataSerializableFactory.

Specified by:

getId in interface IdentifiedDataSerializable

Returns:

type ID

writeData

public void writeData(ObjectDataOutput out)
               throws IOException

Description copied from interface: DataSerializable

Writes object fields to output stream

Specified by:

writeData in interface DataSerializable

Parameters:

out - output

Throws:

IOException - if an I/O error occurs. In particular, an IOException may be thrown if the output stream has been closed.

readData

public void readData(ObjectDataInput in)
              throws IOException

Description copied from interface: DataSerializable

Reads fields from the input stream

Specified by:

readData in interface DataSerializable

Parameters:

in - input

Throws:

IOException - if an I/O error occurs. In particular, an IOException may be thrown if the input stream has been closed.

getEncodingType

public com.hazelcast.cardinality.impl.hyperloglog.impl.HyperLogLogEncoding getEncodingType()

Description copied from interface: HyperLogLogEncoder

Returns the encoding type of this instance; see: HyperLogLogEncoding

Specified by:

getEncodingType in interface HyperLogLogEncoder

Returns:

HyperLogLogEncoding

getMemoryFootprint

public int getMemoryFootprint()

Description copied from interface: HyperLogLogEncoder

Returns the size in memory occupied (in bytes) for this implementation of HyperLogLog.

Specified by:

getMemoryFootprint in interface HyperLogLogEncoder

Returns:

the size in memory.