Package org.moeaframework.core.operator.real

Class PCX

java.lang.Object
org.moeaframework.core.operator.real.MultiParentVariation
org.moeaframework.core.operator.real.PCX
All Implemented Interfaces:
Configurable, Variation
public class PCX extends MultiParentVariation
Parent-centric crossover (PCX) operator. PCX is a multiparent operator, allowing a user-defined number of parents and offspring. Offspring are clustered around the parents, as depicted in the figure below.

Example PCX operator distribution

References:

  1. Deb, K., Anand, A., and Joshi, D., "A Computationally Efficient Evolutionary Algorithm for Real-Parameter Optimization," Evolutionary Computation, 10(4):371-395, 2002.

  • Field Summary

    Fields inherited from class org.moeaframework.core.operator.real.MultiParentVariation

    numberOfOffspring, numberOfParents

  • Constructor Summary

    Constructors
    Constructor
    Description
    PCX()
    Constructs a PCX operator with default settings, taking 10 parents and producing 2 offspring.
    PCX(int numberOfParents, int numberOfOffspring)
    Constructs a PCX operator with the specified number of parents and offspring.
    PCX(int numberOfParents, int numberOfOffspring, double eta, double zeta)
    Constructs a PCX operator with the specified number of parents and offspring, and the specified values for sigma_eta and sigma_zeta.

  • Method Summary

    Modifier and Type
    Method
    Description
    Solution[]
    evolve(Solution[] parents)
    Evolves one or more parent solutions (specified by getArity) and produces one or more child solutions.
    double
    getEta()
    Returns the standard deviation of the normal distribution controlling the spread of solutions in the direction of the selected parent.
    String
    getName()
    Returns the name of this variation operator.
    double
    getZeta()
    Returns the standard deviation of the normal distribution controlling the spread of solutions in the directions defined by the remaining parents.
    protected Solution
    pcx(Solution[] parents)
    Returns one randomly-generated offspring produced by this operator using parents[parents.length-1] as the selected parent.
    void
    setEta(double eta)
    Sets the standard deviation of the normal distribution controlling the spread of solutions in the direction of the selected parent.
    void
    setZeta(double zeta)
    Sets the standard deviation of the normal distribution controlling the spread of solutions in the directions defined by the remaining parents.

    Methods inherited from class org.moeaframework.core.operator.real.MultiParentVariation

    getArity, getNumberOfOffspring, getNumberOfParents, setNumberOfOffspring, setNumberOfParents

    Methods inherited from class java.lang.Object

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

    Methods inherited from interface org.moeaframework.core.configuration.Configurable

    applyConfiguration, getConfiguration

  • Constructor Details

    • PCX

      public PCX()
      Constructs a PCX operator with default settings, taking 10 parents and producing 2 offspring. The eta and zeta parameters are set to 0.1, as suggested by Deb et al. (2002).

    • PCX

      public PCX(int numberOfParents, int numberOfOffspring)
      Constructs a PCX operator with the specified number of parents and offspring. The eta and zeta parameters are set to 0.1, as suggested by Deb et al. (2002).
      Parameters:
      numberOfParents - the number of parents required by this operator
      numberOfOffspring - the number of offspring produced by this operator

    • PCX

      public PCX(int numberOfParents, int numberOfOffspring, double eta, double zeta)
      Constructs a PCX operator with the specified number of parents and offspring, and the specified values for sigma_eta and sigma_zeta.
      Parameters:
      numberOfParents - the number of parents required by this operator
      numberOfOffspring - the number of offspring produced by this operator
      eta - the standard deviation of the normal distribution controlling the spread of solutions in the direction of the selected parent
      zeta - the standard deviation of the normal distribution controlling the spread of solutions in the directions defined by the remaining parents

  • Method Details

    • getName

      public String getName()
      Description copied from interface: Variation
      Returns the name of this variation operator. This name should also be used as the prefix for any parameters. As such, the name should only contain alphanumeric characters, avoid using whitespace and other symbols.
      Returns:
      the name of this variation operator

    • getEta

      public double getEta()
      Returns the standard deviation of the normal distribution controlling the spread of solutions in the direction of the selected parent.
      Returns:
      the standard deviation value

    • setEta

      public void setEta(double eta)
      Sets the standard deviation of the normal distribution controlling the spread of solutions in the direction of the selected parent. The default value is 0.1.
      Parameters:
      eta - the standard deviation value

    • getZeta

      public double getZeta()
      Returns the standard deviation of the normal distribution controlling the spread of solutions in the directions defined by the remaining parents.
      Returns:
      the standard deviation value

    • setZeta

      public void setZeta(double zeta)
      Sets the standard deviation of the normal distribution controlling the spread of solutions in the directions defined by the remaining parents. The default value is 0.1.
      Parameters:
      zeta - the standard deviation value

    • evolve

      public Solution[] evolve(Solution[] parents)
      Description copied from interface: Variation
      Evolves one or more parent solutions (specified by getArity) and produces one or more child solutions. By contract, the parents must not be modified. The copy constructor should be used to create copies of the parents with these copies subsequently modified.
      Parameters:
      parents - the array of parent solutions
      Returns:
      an array of child solutions

    • pcx

      protected Solution pcx(Solution[] parents)
      Returns one randomly-generated offspring produced by this operator using parents[parents.length-1] as the selected parent. Multiple invocations of this method with the same argument will produce offspring distributed about the selected parent.
      Parameters:
      parents - the parent solutions
      Returns:
      one randomly-generated offspring produced by this operator using parents[parents.length-1] as the selected parent