org.apache.datasketches.tuple

Class Sketch<S extends Summary>

java.lang.Object

org.apache.datasketches.tuple.Sketch<S>

Type Parameters:

S - Type of Summary

Direct Known Subclasses:

CompactSketch, UpdatableSketch

public abstract class Sketch<S extends Summary>
extends Object

This is an equivalent to org.apache.datasketches.theta.Sketch with addition of a user-defined Summary object associated with every unique entry in the sketch.

Field Summary

Fields

Modifier and Type	Field and Description
protected static byte	PREAMBLE_LONGS

Method Summary

Modifier and Type	Method and Description
double	getEstimate() Estimates the cardinality of the set (number of unique values presented to the sketch)
double	getEstimate(int numSubsetEntries) Gets the estimate of the true distinct population of subset tuples represented by the count of entries in a subset of the total retained entries of the sketch.
double	getLowerBound(int numStdDev) Gets the approximate lower error bound given the specified number of Standard Deviations.
double	getLowerBound(int numStdDev, int numSubsetEntries) Gets the estimate of the lower bound of the true distinct population represented by the count of entries in a subset of the total retained entries of the sketch.
abstract int	getRetainedEntries()
double	getTheta() Gets the value of theta as a double between zero and one
long	getThetaLong() Returns Theta as a long
double	getUpperBound(int numStdDev) Gets the approximate upper error bound given the specified number of Standard Deviations.
double	getUpperBound(int numStdDev, int numSubsetEntries) Gets the estimate of the upper bound of the true distinct population represented by the count of entries in a subset of the total retained entries of the sketch.
boolean	isEmpty() See Empty
boolean	isEstimationMode() Returns true if the sketch is Estimation Mode (as opposed to Exact Mode).
SketchIterator<S>	iterator() Returns a SketchIterator
abstract byte[]	toByteArray() This is to serialize an instance to a byte array.
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

PREAMBLE_LONGS

protected static final byte PREAMBLE_LONGS

See Also:

Constant Field Values

Method Detail

getEstimate

public double getEstimate()

Estimates the cardinality of the set (number of unique values presented to the sketch)

Returns:

best estimate of the number of unique values

getUpperBound

public double getUpperBound(int numStdDev)

Gets the approximate upper error bound given the specified number of Standard Deviations. This will return getEstimate() if isEmpty() is true.

Parameters:

numStdDev - See Number of Standard Deviations

Returns:

the upper bound.

getLowerBound

public double getLowerBound(int numStdDev)

Gets the approximate lower error bound given the specified number of Standard Deviations. This will return getEstimate() if isEmpty() is true.

Parameters:

numStdDev - See Number of Standard Deviations

Returns:

the lower bound.

getEstimate

public double getEstimate(int numSubsetEntries)

Gets the estimate of the true distinct population of subset tuples represented by the count of entries in a subset of the total retained entries of the sketch.

Parameters:

numSubsetEntries - number of entries for a chosen subset of the sketch.

Returns:

the estimate of the true distinct population of subset tuples represented by the count of entries in a subset of the total retained entries of the sketch.

getLowerBound

public double getLowerBound(int numStdDev,
                            int numSubsetEntries)

Gets the estimate of the lower bound of the true distinct population represented by the count of entries in a subset of the total retained entries of the sketch.

Parameters:

numStdDev - See Number of Standard Deviations

numSubsetEntries - number of entries for a chosen subset of the sketch.

Returns:

the estimate of the lower bound of the true distinct population represented by the count of entries in a subset of the total retained entries of the sketch.

getUpperBound

public double getUpperBound(int numStdDev,
                            int numSubsetEntries)

Gets the estimate of the upper bound of the true distinct population represented by the count of entries in a subset of the total retained entries of the sketch.

Parameters:

numStdDev - See Number of Standard Deviations

numSubsetEntries - number of entries for a chosen subset of the sketch.

Returns:

the estimate of the upper bound of the true distinct population represented by the count of entries in a subset of the total retained entries of the sketch.

isEmpty

public boolean isEmpty()

See Empty

Returns:

true if empty.

isEstimationMode

public boolean isEstimationMode()

Returns true if the sketch is Estimation Mode (as opposed to Exact Mode). This is true if theta < 1.0 AND isEmpty() is false.

Returns:

true if the sketch is in estimation mode.

getRetainedEntries

public abstract int getRetainedEntries()

Returns:

number of retained entries

getTheta

public double getTheta()

Gets the value of theta as a double between zero and one

Returns:

the value of theta as a double

toByteArray

public abstract byte[] toByteArray()

This is to serialize an instance to a byte array.

Returns:

serialized representation of the sketch

iterator

public SketchIterator<S> iterator()

Returns a SketchIterator

Returns:

a SketchIterator

getThetaLong

public long getThetaLong()

Returns Theta as a long

Returns:

Theta as a long

toString

public String toString()

Overrides:

toString in class Object