Package repast.simphony.parameter.optimizer

Class HillClimber

java.lang.Object

repast.simphony.parameter.optimizer.HillClimber

All Implemented Interfaces:

AdvancementChooser

Direct Known Subclasses:

AnnealingAdvancementChooser

public class HillClimber
extends Object
implements AdvancementChooser

This is a simple advancement algorithm that will perform a Hill Climbing traversal of the space.

Author:

Jerry Vos

See Also:

chooseAdvancement(repast.simphony.parameter.ParameterSetter, AdvanceType, double)

Field Summary

Fields

Modifier and Type	Field	Description
protected double	centerValue
protected boolean	checkingLocal
protected boolean	forwardValid
protected double	forwardValue
protected ParameterSetter	lastSetter
protected double	lastValue

Constructor Summary

Constructors

Constructor	Description
HillClimber()	Constructs the climber.

Method Summary

Modifier and Type	Method	Description
AdvanceType	chooseAdvancement(ParameterSetter setter, AdvanceType lastType, double runResult)	This performs the hill climbing algorithm.
boolean	shouldRevert(double runResult)	Returns true when the previous run's value was greater than runResult or when we're exploring the local space to figure out which direction to go.

Methods inherited from class java.lang.Object

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

Field Detail

lastValue

protected double lastValue

checkingLocal

protected boolean checkingLocal

forwardValid

protected boolean forwardValid

forwardValue

protected double forwardValue

centerValue

protected double centerValue

lastSetter

protected ParameterSetter lastSetter

Constructor Detail

HillClimber

public HillClimber()

Constructs the climber.

Method Detail

chooseAdvancement

public AdvanceType chooseAdvancement(ParameterSetter setter,
                                     AdvanceType lastType,
                                     double runResult)

This performs the hill climbing algorithm. In the best case it will traverse the space by (assuming we've just chosen a new parameter):

• Explore the local space to find which direction to follow. It first will explore to the right (FORWARD) of the current position, then to the left (BACKWARD).
• Next it will move whichever direction is best of left, right, and the neither (if we're at a peak). If we're on a peak it will return AdvanceType.SWITCH.

Because of the implementation, this may result in a single spot being executed multiple times in order. Also, this handles the border cases where it cannot move forwards or backwards (but wishes to) by switching.

Specified by:

chooseAdvancement in interface AdvancementChooser

Parameters:

setter - the current setter

lastType - the last executed parameter command

runResult - the last run's value

Returns:

the action to perform

shouldRevert

public boolean shouldRevert(double runResult)

Returns true when the previous run's value was greater than runResult or when we're exploring the local space to figure out which direction to go.

Specified by:

shouldRevert in interface AdvancementChooser

Parameters:

runResult - the result of the previous run

Returns:

if we should revert to the previous space