//  Griewank.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.singleObjective;

import jmetal.core.Problem;
import jmetal.core.Solution;
import jmetal.core.Variable;
import jmetal.encodings.solutionType.BinaryRealSolutionType;
import jmetal.encodings.solutionType.RealSolutionType;
import jmetal.util.JMException;

/**
 * Class representing problem Griewank
 */

public class Griewank extends Problem {
  /** 
   * Constructor
   * Creates a default instance of the Griewank problem
   * @param numberOfVariables Number of variables of the problem 
   * @param solutionType The solution type must "Real" or "BinaryReal". 
   */
  public Griewank(String solutionType, Integer numberOfVariables) {
    numberOfVariables_   = numberOfVariables;
    numberOfObjectives_  = 1;
    numberOfConstraints_ = 0;
    problemName_         = "Sphere";
        
    upperLimit_ = new double[numberOfVariables_];
    lowerLimit_ = new double[numberOfVariables_];
    for (int var = 0; var < numberOfVariables_; var++){
      lowerLimit_[var] = -600.0;
      upperLimit_[var] = 600.0;
    } // for
        
    if (solutionType.compareTo("BinaryReal") == 0)
    	solutionType_ = new BinaryRealSolutionType(this) ;
    else if (solutionType.compareTo("Real") == 0)
    	solutionType_ = new RealSolutionType(this) ;
    else {
    	System.out.println("Error: solution type " + solutionType + " invalid") ;
    	System.exit(-1) ;
    }  
  } // Griewank
    
  /** 
  * Evaluates a solution 
  * @param solution The solution to evaluate
   * @throws JMException 
  */        
  public void evaluate(Solution solution) throws JMException {
    Variable[] decisionVariables  = solution.getDecisionVariables();

    double sum  = 0.0    ;
    double mult = 1.0    ;
    double d    = 4000.0 ;
    for (int var = 0; var < numberOfVariables_; var++) {
      sum += decisionVariables[var].getValue() * 
             decisionVariables[var].getValue() ;    
      mult *= Math.cos(decisionVariables[var].getValue()/Math.sqrt(var+1)) ;    
    }        

    solution.setObjective(0, 1.0/d * sum - mult + 1.0) ;
  } // evaluate
} // Griewank