com.bigdata.util.concurrent

Class MovingAverageTask

java.lang.Object

com.bigdata.util.concurrent.MovingAverageTask

All Implemented Interfaces:

Runnable

Direct Known Subclasses:

DeltaMovingAverageTask, QueueSizeMovingAverageTask

public class MovingAverageTask
extends Object
implements Runnable

Class tracks a the moving average of some sampled datum.

Version:

$Id$

Author:

Bryan Thompson

Field Summary

Fields

Modifier and Type	Field and Description
protected double	average The moving average.
static double	DEFAULT_WEIGHT The recommended default weight.
protected static org.apache.log4j.Logger	log
protected String	name The label used in log messages.
protected long	nsamples #of samples taken so far.
protected Callable<? extends Number>	sampleTask Used to sample whatever is being measured.
protected double	w The weight used to compute the moving average.

Constructor Summary

Constructors

Constructor and Description
MovingAverageTask(String name, Callable<? extends Number> sampleTask)
MovingAverageTask(String name, Callable<? extends Number> sampleTask, double w) Core impl.

Method Summary

Methods

Modifier and Type	Method and Description
double	getMovingAverage() The current value of the moving average.
protected static double	getMovingAverage(double avg, double q, double w) Compute a moving average: (1 - w) * avg + w * q
long	getSampleCount() #of samples taken so far.
double	getWeight() The weight used to compute the moving average.
void	run() Note: don't throw anything from here or it will cause the task to no longer be run!

Methods inherited from class java.lang.Object

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

Field Detail

log

protected static final org.apache.log4j.Logger log

name

protected final String name

The label used in log messages.

sampleTask

protected final Callable<? extends Number> sampleTask

Used to sample whatever is being measured.

w

protected final double w

The weight used to compute the moving average.

nsamples

protected long nsamples

#of samples taken so far.

average

protected double average

The moving average.

DEFAULT_WEIGHT

public static final double DEFAULT_WEIGHT

The recommended default weight.

See Also:

Constant Field Values

Constructor Detail

MovingAverageTask

public MovingAverageTask(String name,
                 Callable<? extends Number> sampleTask)

Parameters:

name - The label for log messages.

sampleTask - Task that returns a sampled value.

MovingAverageTask

public MovingAverageTask(String name,
                 Callable<? extends Number> sampleTask,
                 double w)

Core impl.

Parameters:

name - The label for log messages.

queue - Task that returns a sampled value.

w - The weight to be used by getMovingAverage(double, double, double)

Method Detail

getMovingAverage

public double getMovingAverage()

The current value of the moving average.

getWeight

public double getWeight()

The weight used to compute the moving average.

getSampleCount

public long getSampleCount()

#of samples taken so far.

getMovingAverage

protected static final double getMovingAverage(double avg,
                      double q,
                      double w)

Compute a moving average: (1 - w) * avg + w * q

Parameters:

avg - The previous average and initially zero (0.0).

q - The current value (e.g., the instantaneous measurement of the #of active tasks plus the length of the queue).

w - The weight for the moving average in (0:1). Values around .2 seem appropriate.

Returns:

The updated moving average.

run

public void run()

Note: don't throw anything from here or it will cause the task to no longer be run!

Specified by:

run in interface Runnable