com.github.benmanes.caffeine.cache.simulator.admission.countmin4

Class CountMin4

java.lang.Object

com.github.benmanes.caffeine.cache.simulator.admission.countmin4.CountMin4

All Implemented Interfaces:

Frequency

Direct Known Subclasses:

ClimberResetCountMin4, IncrementalResetCountMin4, PeriodicResetCountMin4

public abstract class CountMin4
extends Object
implements Frequency

A probabilistic multiset for estimating the popularity of an element within a time window. The maximum frequency of an element is limited to 15 (4-bits) and extensions provide the aging process.

Field Summary

Fields

Modifier and Type	Field and Description
protected boolean	conservative
protected int	step
protected long[]	table
protected int	tableMask

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	CountMin4(Config config) Creates a frequency sketch that can accurately estimate the popularity of elements given the maximum size of the cache.

Method Summary

Modifier and Type	Method and Description
protected void	ensureCapacity(long maximumSize) Increases the capacity of this FrequencySketch instance, if necessary, to ensure that it can accurately estimate the popularity of elements given the maximum size of the cache.
int	frequency(long e) Returns the estimated number of occurrences of an element, up to the maximum (15).
void	increment(long e) Increments the popularity of the element if it does not exceed the maximum (15).
protected void	tryReset(boolean added) Performs the aging process after an addition to allow old entries to fade away.

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.github.benmanes.caffeine.cache.simulator.admission.Frequency

reportMiss

Field Detail

conservative

protected final boolean conservative

tableMask

protected int tableMask

table

protected long[] table

step

protected int step

Constructor Detail

CountMin4

protected CountMin4(Config config)

Creates a frequency sketch that can accurately estimate the popularity of elements given the maximum size of the cache.

Method Detail

ensureCapacity

protected void ensureCapacity(long maximumSize)

Increases the capacity of this FrequencySketch instance, if necessary, to ensure that it can accurately estimate the popularity of elements given the maximum size of the cache. This operation forgets all previous counts when resizing.

Parameters:

maximumSize - the maximum size of the cache

frequency

public int frequency(long e)

Returns the estimated number of occurrences of an element, up to the maximum (15).

Specified by:

frequency in interface Frequency

Parameters:

e - the element to count occurrences of

Returns:

the estimated number of occurrences of the element; possibly zero but never negative

increment

public void increment(long e)

Increments the popularity of the element if it does not exceed the maximum (15). The popularity of all elements will be periodically down sampled when the observed events exceeds a threshold. This process provides a frequency aging to allow expired long term entries to fade away.

Specified by:

increment in interface Frequency

Parameters:

e - the element to add

tryReset

protected void tryReset(boolean added)

Performs the aging process after an addition to allow old entries to fade away.