// ZDT2.java
//
// Author:
// Antonio J. Nebro <antonio@lcc.uma.es>
// Juan J. Durillo <durillo@lcc.uma.es>
//
// Copyright (c) 2011 Antonio J. Nebro, Juan J. Durillo
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
package jmetal.problems.ZDT;
import jmetal.core.Problem;
import jmetal.core.Solution;
import jmetal.encodings.solutionType.ArrayRealSolutionType;
import jmetal.encodings.solutionType.BinaryRealSolutionType;
import jmetal.encodings.solutionType.RealSolutionType;
import jmetal.util.JMException;
import jmetal.util.wrapper.XReal;
/**
* Class representing problem ZDT2
*/
public class ZDT2 extends Problem{
/**
* Constructor.
* Creates a default instance of problem ZDT2 (30 decision variables)
* @param solutionType The solution type must "Real", "BinaryReal, and "ArrayReal".
*/
public ZDT2(String solutionType) throws ClassNotFoundException {
this(solutionType, 30); // 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(String solutionType, Integer numberOfVariables) {
numberOfVariables_ = numberOfVariables;
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
if (solutionType.compareTo("BinaryReal") == 0)
solutionType_ = new BinaryRealSolutionType(this) ;
else if (solutionType.compareTo("Real") == 0)
solutionType_ = new RealSolutionType(this) ;
else if (solutionType.compareTo("ArrayReal") == 0)
solutionType_ = new ArrayRealSolutionType(this) ;
else {
System.out.println("Error: solution type " + solutionType + " invalid") ;
System.exit(-1) ;
}
} //ZDT2
/**
* Evaluates a solution
* @param solution The solution to evaluate
* @throws JMException
*/
public void evaluate(Solution solution) throws JMException {
XReal x = new XReal(solution) ;
double [] fx = new double[numberOfObjectives_] ;
fx[0] = x.getValue(0) ;
double g = this.evalG(x) ;
double h = this.evalH(fx[0],g) ;
fx[1] = h * g ;
solution.setObjective(0,fx[0]);
solution.setObjective(1,fx[1]);
} //evaluate
/**
* Returns the value of the ZDT2 function G.
* @param x Solution
* @throws JMException
*/
private double evalG(XReal x) throws JMException {
double g = 0.0;
for (int i = 1; i < x.getNumberOfDecisionVariables();i++)
g += x.getValue(i);
double constant = (9.0 / (numberOfVariables_-1));
g = constant * 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