org.apache.hadoop.hbase.util

Class RollingStatCalculator

java.lang.Object

org.apache.hadoop.hbase.util.RollingStatCalculator

@InterfaceAudience.Private
public class RollingStatCalculator
extends Object

This class maintains mean and variation for any sequence of input provided to it. It is initialized with number of rolling periods which basically means the number of past inputs whose data will be considered to maintain mean and variation. It will use O(N) memory to maintain these statistics, where N is number of look up periods it was initialized with. If zero is passed during initialization then it will maintain mean and variance from the start. It will use O(1) memory only. But note that since it will maintain mean / variance from the start the statistics may behave like constants and may ignore short trends. All operations are O(1) except the initialization which is O(N).

Field Summary

Fields

Modifier and Type	Field and Description
private int	currentIndexPosition
private double	currentSqrSum
private double	currentSum
private long[]	dataValues
private long	numberOfDataValues
private int	rollingPeriod

Constructor Summary

Constructors

Constructor and Description
RollingStatCalculator(int rollingPeriod) Creates a RollingStatCalculator with given number of rolling periods.

Method Summary

Modifier and Type	Method and Description
private long[]	fillWithZeros(int size)
double	getDeviation()
double	getMean()
void	insertDataValue(long data) Inserts given data value to array of data values to be considered for statistics calculation
private void	removeData(long data) Update the statistics after removing the given data value

Methods inherited from class java.lang.Object

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

Field Detail

currentSum

private double currentSum

currentSqrSum

private double currentSqrSum

numberOfDataValues

private long numberOfDataValues

rollingPeriod

private int rollingPeriod

currentIndexPosition

private int currentIndexPosition

dataValues

private long[] dataValues

Constructor Detail

RollingStatCalculator

public RollingStatCalculator(int rollingPeriod)

Creates a RollingStatCalculator with given number of rolling periods.

Parameters:

rollingPeriod -

Method Detail

insertDataValue

public void insertDataValue(long data)

Inserts given data value to array of data values to be considered for statistics calculation

Parameters:

data -

removeData

private void removeData(long data)

Update the statistics after removing the given data value

Parameters:

data -

getMean

public double getMean()

Returns:

mean of the data values that are in the current list of data values

getDeviation

public double getDeviation()

Returns:

deviation of the data values that are in the current list of data values

fillWithZeros

private long[] fillWithZeros(int size)

Parameters:

size -

Returns:

an array of given size initialized with zeros