Package com.yahoo.searchlib.aggregation.hll

Class HyperLogLogEstimator

java.lang.Object

com.yahoo.searchlib.aggregation.hll.HyperLogLogEstimator

All Implemented Interfaces:

UniqueCountEstimator<Sketch<?>>

public class HyperLogLogEstimator
extends Object
implements UniqueCountEstimator<Sketch<?>>

Implementation of the result computation phase of the HyperLogLog algorithm. Based on the pseudo code from: http://www.dmtcs.org/dmtcs-ojs/index.php/proceedings/article/viewArticle/914

Author:

bjorncs

Constructor Summary

Constructors

Constructor	Description
HyperLogLogEstimator()	Creates the estimator with the default precision (HyperLogLog.DEFAULT_PRECISION.
HyperLogLogEstimator(int precision)	Creates the estimator for a given precision.

Method Summary

Modifier and Type	Method	Description
long	estimateCount(Sketch<?> sketch)	Estimates the number of unique elements.

Methods inherited from class java.lang.Object

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

Constructor Details

HyperLogLogEstimator

public HyperLogLogEstimator(int precision)

Creates the estimator for a given precision. The resulting memory consumption is the exponential to the precision.

Parameters:

precision - The precision parameter as defined in HLL algorithm.

HyperLogLogEstimator

public HyperLogLogEstimator()

Creates the estimator with the default precision (HyperLogLog.DEFAULT_PRECISION.

Method Details

estimateCount

public long estimateCount(Sketch<?> sketch)

Estimates the number of unique elements.

Specified by:

estimateCount in interface UniqueCountEstimator<Sketch<?>>

Parameters:

sketch - A sketch populated with values from the aggregation phase of HLL.

Returns:

The estimated number of unique elements.