com.yahoo.sketches.hll

Class HllSketch

java.lang.Object

com.yahoo.sketches.hll.HllSketch

public class HllSketch
extends Object

Top-level class for the HLL family of sketches. Use the HllSketchBuilder to construct this class.

Author:

Kevin Lang

Constructor Summary

Constructors

Constructor and Description
HllSketch(Fields fields) Construct this class with the given Fields

Method Summary

Modifier and Type	Method and Description
HllSketch	asCompact() Returns this sketch in compact form
static HllSketchBuilder	builder() Returns an HllSketchBuilder
double	getEstimate() Gets the unique count estimate.
double	getLowerBound(double numStdDevs) Gets the lower bound with respect to the Estimate
Preamble	getPreamble() Gets the Preamble of this sketch
double	getUpperBound(double numStdDevs) Gets the upper bound with respect to the Estimate
protected double	inversePowerOf2Sum() The sum of the inverse powers of 2
int	numBuckets() Returns the number of configured buckets (k)
protected int	numBucketsAtZero()
protected void	setUpdateCallback(Fields.UpdateCallback updateCallback) Set the update callback.
byte[]	toByteArray() Serializes this sketch to a byte array
byte[]	toByteArrayNoPreamble() Serializes this sketch without the Preamble as a byte array
HllSketch	union(HllSketch that) Union this sketch with that one
void	update(byte[] data) Present this sketch with the given byte array.
void	update(double datum) Present this sketch with the given double (or float) datum.
void	update(int[] data) Present this sketch with the given integer array.
void	update(long datum) Present this sketch with a long.
void	update(long[] data) Present this sketch with the given long array.
void	update(String datum) Present this sketch with the given String.

Methods inherited from class java.lang.Object

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

Constructor Detail

HllSketch

public HllSketch(Fields fields)

Construct this class with the given Fields

Parameters:

fields - the given Fields

Method Detail

builder

public static HllSketchBuilder builder()

Returns an HllSketchBuilder

Returns:

an HllSketchBuilder

update

public void update(long datum)

Present this sketch with a long.

Parameters:

datum - The given long datum.

update

public void update(double datum)

Present this sketch with the given double (or float) datum. The double will be converted to a long using Double.doubleToLongBits(datum), which normalizes all NaN values to a single NaN representation. Plus and minus zero will be normalized to plus zero. The special floating-point values NaN and +/- Infinity are treated as distinct.

Parameters:

datum - The given double datum.

update

public void update(String datum)

Present this sketch with the given String. The string is converted to a byte array using UTF8 encoding. If the string is null or empty no update attempt is made and the method returns.

Parameters:

datum - The given String.

update

public void update(byte[] data)

Present this sketch with the given byte array. If the byte array is null or empty no update attempt is made and the method returns.

Parameters:

data - The given byte array.

update

public void update(int[] data)

Present this sketch with the given integer array. If the integer array is null or empty no update attempt is made and the method returns.

Parameters:

data - The given int array.

update

public void update(long[] data)

Present this sketch with the given long array. If the long array is null or empty no update attempt is made and the method returns.

Parameters:

data - The given long array.

getEstimate

public double getEstimate()

Gets the unique count estimate.

Returns:

the sketch's best estimate of the cardinality of the input stream.

getUpperBound

public double getUpperBound(double numStdDevs)

Gets the upper bound with respect to the Estimate

Parameters:

numStdDevs - the number of standard deviations from the Estimate

Returns:

the upper bound

getLowerBound

public double getLowerBound(double numStdDevs)

Gets the lower bound with respect to the Estimate

Parameters:

numStdDevs - the number of standard deviations from the Estimate

Returns:

the lower bound

union

public HllSketch union(HllSketch that)

Union this sketch with that one

Parameters:

that - the other sketch

Returns:

this sketch

toByteArray

public byte[] toByteArray()

Serializes this sketch to a byte array

Returns:

this sketch as a byte array

toByteArrayNoPreamble

public byte[] toByteArrayNoPreamble()

Serializes this sketch without the Preamble as a byte array

Returns:

this sketch without the Preamble as a byte array

asCompact

public HllSketch asCompact()

Returns this sketch in compact form

Returns:

this sketch in compact form

numBuckets

public int numBuckets()

Returns the number of configured buckets (k)

Returns:

the number of configured buckets (k)

getPreamble

public Preamble getPreamble()

Gets the Preamble of this sketch

Returns:

the Preamble of this sketch

setUpdateCallback

protected final void setUpdateCallback(Fields.UpdateCallback updateCallback)

Set the update callback. It is final so that it can not be overridden.

Parameters:

updateCallback - the update callback for the HllSketch to use when talking with its Fields

inversePowerOf2Sum

protected double inversePowerOf2Sum()

The sum of the inverse powers of 2

Returns:

the sum of the inverse powers of 2

numBucketsAtZero

protected int numBucketsAtZero()