RandomSelection.java

//  RandomSelection.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.operators.selection;

import jmetal.core.Solution;
import jmetal.core.SolutionSet;
import jmetal.util.PseudoRandom;

import java.util.HashMap;

/**
 * This class implements a random selection operator used for selecting two
 * random parents
 */
public class RandomSelection extends Selection {
  public RandomSelection(HashMap<String, Object> parameters) {
  	super(parameters) ;
  }
  
  /**
  * Performs the operation
  * @param object Object representing a SolutionSet.
  * @return an object representing an array with the selected parents
  */
  public Object execute(Object object) {
    SolutionSet population = (SolutionSet)object;
    int pos1, pos2;
    pos1 = PseudoRandom.randInt(0,population.size()-1);
    pos2 = PseudoRandom.randInt(0,population.size()-1);
    while ((pos1 == pos2) && (population.size()>1)) {
      pos2 = PseudoRandom.randInt(0,population.size()-1);
    }
    
    Solution [] parents = new Solution[2];
    parents[0] = population.get(pos1);
    parents[1] = population.get(pos2);
    
    return parents;
  } // Execute     
} // RandomSelection