FourBarTruss.java

//  FourBarTruss.java
//
//  Author:
//       Antonio J. Nebro <antonio@lcc.uma.es>
//
//  Copyright (c) 2012 Antonio J. Nebro
//
//  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 org.uma.jmetal.problem.multiobjective;

import org.uma.jmetal.problem.impl.AbstractDoubleProblem;
import org.uma.jmetal.solution.DoubleSolution;

import java.util.ArrayList;
import java.util.List;

/**
 * Class representing problem FourBarTruss
 *
 * 	Measures:
 * 	f = 10kN
 *  e = 200000 kN/cm2
 *  l = 200 cm
 *  sigma = 10kN/cm2
 */
@SuppressWarnings("serial")
public class FourBarTruss extends AbstractDoubleProblem {
	private double f = 10   ;
  private double e = 200000;
  private double l = 200  ;
  private double sigma = 10 ;
	
  /**
   * Constructor
   * Creates a default instance of the FourBarTruss problem
   */
  public FourBarTruss() {
    setNumberOfVariables(4);
    setNumberOfObjectives(2);
    setNumberOfConstraints(0);
    setName("FourBarTruss");

    List<Double> lowerLimit = new ArrayList<>(getNumberOfVariables()) ;
    List<Double> upperLimit = new ArrayList<>(getNumberOfVariables()) ;

    lowerLimit.add(f / sigma) ;
    lowerLimit.add(Math.sqrt(2.0)*(f / sigma));
    lowerLimit.add(lowerLimit.get(1)) ;
    lowerLimit.add(lowerLimit.get(0)) ;

    upperLimit.add(3*(f / sigma)) ;
    upperLimit.add(upperLimit.get(0)) ;
    upperLimit.add(upperLimit.get(0)) ;
    upperLimit.add(upperLimit.get(0)) ;

    setLowerLimit(lowerLimit);
    setUpperLimit(upperLimit);
  }

  /** Evaluate() method */
  @Override
  public void evaluate(DoubleSolution solution) {
    double [] fx = new double[2] ;
    double [] x = new double[getNumberOfVariables()] ;
    for (int i = 0 ; i < getNumberOfVariables(); i++)
    	x[i] = solution.getVariableValue(i) ;
    
    fx[0] = l *(2*x[0]+ Math.sqrt(2.0)*x[1]+ Math.sqrt(x[2])+x[3]) ;
    fx[1] = (f * l / e)*(2/x[0] + 2*Math.sqrt(2)/x[1] - 2*Math.sqrt(2)/x[2] + 2/x[3]);
    
    solution.setObjective(0,fx[0]);
    solution.setObjective(1,fx[1]);
  }
}