Package org.uma.jmetal.operator.crossover.impl

Class BLXAlphaBetaCrossover

java.lang.Object

org.uma.jmetal.operator.crossover.impl.BLXAlphaBetaCrossover

All Implemented Interfaces:

Serializable, CrossoverOperator<DoubleSolution>, Operator<List<DoubleSolution>,List<DoubleSolution>>

public class BLXAlphaBetaCrossover
extends Object
implements CrossoverOperator<DoubleSolution>

This class implements the BLX-αβ crossover operator for real-valued solutions. The BLX-αβ crossover creates offspring that are randomly selected from intervals that extend beyond the parent values, controlled by parameters α and β.

Reference: Eshelman, L. J., invalid input: '&' Schaffer, J. D. (1993). Real-coded genetic algorithms and interval-schemata. Foundations of genetic algorithms, 2, 187-202.

Parameter recommendations:

• α (alpha): Controls the exploration range below the smaller parent value. Typical values are in the range [0.0, 1.0]. A value of 0.0 means no exploration below the smaller parent, while 1.0 allows exploration equal to the distance between parents below the smaller parent.
• β (beta): Controls the exploration range above the larger parent value. Typical values are in the range [0.0, 1.0]. A value of 0.0 means no exploration above the larger parent, while 1.0 allows exploration equal to the distance between parents above the larger parent.

Note: Both α and β must be non-negative values. Setting both to 0.0 results in a crossover that only generates values strictly between the parent values.

Author:

Antonio J. Nebro

See Also:

• Serialized Form

Field Summary

Fields

Modifier and Type	Field	Description
static final double	DEFAULT_ALPHA
static final double	DEFAULT_BETA

Constructor Summary

Constructors

Constructor	Description
BLXAlphaBetaCrossover(double crossoverProbability)	Constructor with default alpha and beta values
BLXAlphaBetaCrossover(double crossoverProbability, double alpha, double beta)	Constructor with default random generator
BLXAlphaBetaCrossover(double crossoverProbability, double alpha, double beta, RepairDoubleSolution solutionRepair)	Constructor with default solution repair strategy
BLXAlphaBetaCrossover(double crossoverProbability, double alpha, double beta, RepairDoubleSolution solutionRepair, RandomGenerator<Double> randomGenerator)	Constructor with custom random generator and solution repair strategy

Method Summary

Modifier and Type	Method	Description
double	crossoverProbability()
List<DoubleSolution>	execute(List<DoubleSolution> solutions)
double	getAlpha()
double	getBeta()
int	numberOfGeneratedChildren()
int	numberOfRequiredParents()

Methods inherited from class java.lang.Object

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

Field Details

DEFAULT_ALPHA

public static final double DEFAULT_ALPHA

See Also:

• Constant Field Values

DEFAULT_BETA

public static final double DEFAULT_BETA

See Also:

• Constant Field Values

Constructor Details

BLXAlphaBetaCrossover

public BLXAlphaBetaCrossover(double crossoverProbability)

Constructor with default alpha and beta values

Parameters:

crossoverProbability -

BLXAlphaBetaCrossover

public BLXAlphaBetaCrossover(double crossoverProbability,
 double alpha,
 double beta)

Constructor with default random generator

Parameters:

crossoverProbability - Crossover probability (must be in [0,1])

alpha - Controls exploration below parents (must be >= 0, typical [0,1])

beta - Controls exploration above parents (must be >= 0, typical [0,1])

BLXAlphaBetaCrossover

public BLXAlphaBetaCrossover(double crossoverProbability,
 double alpha,
 double beta,
 RepairDoubleSolution solutionRepair)

Constructor with default solution repair strategy

Parameters:

crossoverProbability - Crossover probability (must be in [0,1])

alpha - Controls exploration below parents (must be >= 0, typical [0,1])

beta - Controls exploration above parents (must be >= 0, typical [0,1])

solutionRepair - Strategy for repairing solutions

BLXAlphaBetaCrossover

public BLXAlphaBetaCrossover(double crossoverProbability,
 double alpha,
 double beta,
 RepairDoubleSolution solutionRepair,
 RandomGenerator<Double> randomGenerator)

Constructor with custom random generator and solution repair strategy

Parameters:

crossoverProbability - Crossover probability (must be in [0,1])

alpha - Controls exploration below parents (must be >= 0, typical [0,1])

beta - Controls exploration above parents (must be >= 0, typical [0,1])

solutionRepair - Strategy for repairing solutions

randomGenerator - Custom random number generator

Method Details

execute

public List<DoubleSolution> execute(List<DoubleSolution> solutions)

Specified by:

execute in interface Operator<List<DoubleSolution>,List<DoubleSolution>>

Parameters:

solutions - The data to process

crossoverProbability

public double crossoverProbability()

Specified by:

crossoverProbability in interface CrossoverOperator<DoubleSolution>

numberOfRequiredParents

public int numberOfRequiredParents()

Specified by:

numberOfRequiredParents in interface CrossoverOperator<DoubleSolution>

numberOfGeneratedChildren

public int numberOfGeneratedChildren()

Specified by:

numberOfGeneratedChildren in interface CrossoverOperator<DoubleSolution>

getAlpha

public double getAlpha()

Returns:

The alpha parameter value (exploration below parents)

getBeta

public double getBeta()

Returns:

The beta parameter value (exploration above parents)