zdt2.java

这是多目标进化算法包

/**
 * ZDT2.java
 *
 * @author Antonio J. Nebro
 * @author Juan J. Durillo
 * @version 1.0
 */

package jmetal.problems.ZDT;

import jmetal.base.*;
import jmetal.base.Configuration.SolutionType_;
import jmetal.base.Configuration.VariableType_;
import jmetal.util.JMException;

/**
 *  Class representing problem ZDT2
 */
public class ZDT2 extends Problem{
      
 /** 
  * Constructor.
  * Creates a default instance of  problem ZDT2 (30 decision variables)
  * @param representation The solution type must "Real" or "BinaryReal".
  */
  public ZDT2(String representation) {
    this(30,representation); // 30 variables by default
  } // ZDT2

  
 /** 
  * Constructor.
  * Creates a new ZDT2 problem instance.
  * @param numberOfVariables Number of variables
  * @param solutionType The solution type must "Real" or "BinaryReal".
  */
  public ZDT2(Integer numberOfVariables, String solutionType) {
    numberOfVariables_  = numberOfVariables.intValue();
    numberOfObjectives_ =  2;
    numberOfConstraints_=  0;
    problemName_        = "ZDT2";

    upperLimit_ = new double[numberOfVariables_];
    lowerLimit_ = new double[numberOfVariables_];

    for (int var = 0; var < numberOfVariables_; var++){
      lowerLimit_[var] = 0.0;
      upperLimit_[var] = 1.0;
    } //for

    solutionType_ = Enum.valueOf(SolutionType_.class, solutionType) ; 
    
    // All the variables are of the same type, so the solutionType name is the
    // same than the variableType name
    variableType_ = new VariableType_[numberOfVariables_];
    for (int var = 0; var < numberOfVariables_; var++){
      variableType_[var] = Enum.valueOf(VariableType_.class, solutionType) ;    
    } // for
  } //ZDT2
  
  /** 
  * Evaluates a solution 
  * @param solution The solution to evaluate
   * @throws JMException 
  */    
  public void evaluate(Solution solution) throws JMException {
    DecisionVariables decisionVariables  = solution.getDecisionVariables();
        
    double [] f = new double[numberOfObjectives_] ;
    f[0]        = decisionVariables.variables_[0].getValue()     ;
    double g    = this.evalG(decisionVariables)                 ;
    double h    = this.evalH(f[0],g)              ;
    f[1]        = h * g                           ;
        
    solution.setObjective(0,f[0]);
    solution.setObjective(1,f[1]);
  } //evaluate
  
  /**
   * Returns the value of the ZDT2 function G.
   * @param decisionVariables The decision variables of the solution to 
   * evaluate.
   * @throws JMException 
   */  
  private double evalG(DecisionVariables decisionVariables) throws JMException {
    double g = 0.0;        
    for (int i = 1; i < decisionVariables.size();i++)
      g += decisionVariables.variables_[i].getValue();
    double constante = (9.0 / (numberOfVariables_-1));
    g = constante * g;
    g = g + 1.0;
    return g;        
  } //evalG
    
  /**
   * Returns the value of the ZDT2 function H.
   * @param f First argument of the function H.
   * @param g Second argument of the function H.
   */
  public double evalH(double f, double g) {
    double h = 0.0;
    h = 1.0 - java.lang.Math.pow(f/g,2.0);
    return h;        
  } // evalH
} //ZDT2