DENSEA.java

//  DENSEA.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.metaheuristics.densea;

import jmetal.core.*;
import jmetal.util.Distance;
import jmetal.util.JMException;
import jmetal.util.Ranking;
import jmetal.util.comparators.CrowdingComparator;
import jmetal.util.comparators.EqualSolutions;

import java.util.Comparator;

/**
 * Class implementing the DENSEA algorithm.
 */
public class DENSEA extends Algorithm{

  /* Create a new instance of DENSEA algorithm */
  public DENSEA(Problem problem) {
    super (problem) ;
  }

  //Implements the Densea delete duplicate elements
  public void deleteDuplicates(SolutionSet population) {
    Comparator equalIndividuals = new EqualSolutions();
    for (int i = 0; i < population.size()/2; i++) {
      for (int j = i+1; j < population.size()/2; j++) {
        int flag = equalIndividuals.compare(population.get(i),population.get(j));
        if (flag == 0) {
          Solution aux = population.get(j);
          population.replace(j,population.get((population.size()/2)+j));
          population.replace((population.size()/2)+j,aux);          
        }
      }
    }
  }

  /* Execute the algorithm */
  public SolutionSet execute() throws JMException, ClassNotFoundException {
    int populationSize, maxEvaluations, evaluations               ;
    SolutionSet population, offspringPopulation, union            ;
    Operator mutationOperator,crossoverOperator,selectionOperator ;
    Distance distance    = new Distance()                         ;               

    //Read the params
    populationSize    = ((Integer)this.getInputParameter("populationSize")).intValue();
    maxEvaluations    = ((Integer)this.getInputParameter("maxEvaluations")).intValue();                

    //Init the variables
    population        = new SolutionSet(populationSize);        
    evaluations       = 0;                

    //Read the operators
    mutationOperator  = this.operators_.get("mutation");
    crossoverOperator = this.operators_.get("crossover");
    selectionOperator = this.operators_.get("selection");  

    //-> Create the initial population
    Solution newIndividual;
    for (int i = 0; i < populationSize; i++) {
      newIndividual = new Solution(problem_);                    
      problem_.evaluate(newIndividual);            
      problem_.evaluateConstraints(newIndividual);
      evaluations++;
      population.add(newIndividual);
    } //for       
    //<-

    Ranking r;

    while (evaluations < maxEvaluations) {
      SolutionSet P3 = new SolutionSet(populationSize);
      for (int i = 0; i < populationSize/2; i++) {
        Solution [] parents = new Solution[2];
        Solution [] offSpring;
        parents[0] = (Solution)selectionOperator.execute(population);
        parents[1] = (Solution)selectionOperator.execute(population);
        offSpring = (Solution [])crossoverOperator.execute(parents);
        mutationOperator.execute(offSpring[0]);
        problem_.evaluate(offSpring[0]);
        problem_.evaluateConstraints(offSpring[0]);
        evaluations++;
        mutationOperator.execute(offSpring[1]);
        problem_.evaluate(offSpring[1]);
        problem_.evaluateConstraints(offSpring[1]);
        evaluations++;
        P3.add(offSpring[0]);
        P3.add(offSpring[1]);
      }

      r = new Ranking(P3);
      for (int i = 0; i < r.getNumberOfSubfronts();i++) {
        distance.crowdingDistanceAssignment(r.getSubfront(i),problem_.getNumberOfObjectives());
      }
      P3.sort(new CrowdingComparator());

     
      population.sort(new CrowdingComparator());
      //deleteDuplicates(population);
      //deleteDuplicates(P3);
      SolutionSet auxiliar = new SolutionSet(populationSize);
      for (int i = 0; i < (populationSize/2);i++) {
        auxiliar.add(population.get(i));
      }

      for (int j = 0; j < (populationSize/2);j++) {
        auxiliar.add(population.get(j));
      }

      population = auxiliar;

      r = new Ranking(population);
      for (int i = 0; i < r.getNumberOfSubfronts();i++) {
        distance.crowdingDistanceAssignment(r.getSubfront(i),problem_.getNumberOfObjectives());
      }
    }
    r = new Ranking(population);
    return r.getSubfront(0);
  }
}