// ZDT4.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 ZDT4
*/
public class ZDT4 extends Problem{
/**
* Constructor.
* Creates a default instance of problem ZDT4 (10 decision variables)
* @param solutionType The solution type must "Real", "BinaryReal, and "ArrayReal".
*/
public ZDT4(String solutionType) throws ClassNotFoundException {
this(solutionType, 10); // 10 variables by default
} // ZDT4
/**
* Creates a instance of problem ZDT4.
* @param numberOfVariables Number of variables.
* @param solutionType The solution type must "Real", "BinaryReal, and "ArrayReal".
*/
public ZDT4(String solutionType, Integer numberOfVariables) {
numberOfVariables_ = numberOfVariables;
numberOfObjectives_ = 2;
numberOfConstraints_= 0;
problemName_ = "ZDT4";
upperLimit_ = new double[numberOfVariables_];
lowerLimit_ = new double[numberOfVariables_];
lowerLimit_[0] = 0.0;
upperLimit_[0] = 1.0;
for (int var = 1; var < numberOfVariables_; var++){
lowerLimit_[var] = -5.0;
upperLimit_[var] = 5.0;
} //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) ;
}
} //ZDT4
/**
* Evaluates a solution
* @param solution The solution to evaluate
* @throws JMException
*/
public void evaluate(Solution solution) throws JMException {
XReal x = new XReal(solution) ;
double [] f = new double[numberOfObjectives_] ;
f[0] = x.getValue(0) ;
double g = this.evalG(x) ;
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 ZDT4 function G.
* @param x Solution
* @throws JMException
*/
public double evalG(XReal x) throws JMException{
double g = 0.0;
for (int var = 1; var < numberOfVariables_; var++)
g += Math.pow(x.getValue(var),2.0) +
- 10.0 * Math.cos(4.0*Math.PI*x.getValue(var));
double constante = 1.0 + 10.0*(numberOfVariables_ - 1);
return g + constante;
} // evalG
/**
* Returns the value of the ZDT4 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){
return 1.0 - Math.sqrt(f/g);
} // evalH
} // ZDT4