//  SolutionComparator.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.util.comparators;

import jmetal.core.Solution;
import jmetal.util.Configuration;
import jmetal.util.Distance;
import jmetal.util.JMException;

import java.util.Comparator;

/**
 * This class implements a <code>Comparator</code> (a method for comparing
 * <code>Solution</code> objects) based on the values of the variables.
 */
public class SolutionComparator implements Comparator {
   
  /**
   * Establishes a value of allowed dissimilarity
   */
  private static final double EPSILON  = 1e-10;    
        
  /**
   * Compares two solutions.
   * @param o1 Object representing the first <code>Solution</code>. 
   * @param o2 Object representing the second <code>Solution</code>.
   * @return 0, if both solutions are equals with a certain dissimilarity, -1
   * otherwise.
   * @throws JMException 
   * @throws JMException 
   */
  public int compare(Object o1, Object o2) {
    Solution solution1, solution2;        
    solution1 = (Solution)o1;
    solution2 = (Solution)o2;
        
    if ((solution1.getDecisionVariables() != null) && (solution2.getDecisionVariables()!= null))
      if (solution1.numberOfVariables() != solution2.numberOfVariables())
        return -1;

    try {
      if ((new Distance()).distanceBetweenSolutions(solution1,solution2) < EPSILON)
        return 0;
    } catch (JMException e) {
      Configuration.logger_.severe("SolutionComparator.compare: JMException ") ; 
    }
                
    return -1;
  } // compare
} // SolutionComparator