mTSP.java

//  MOTSP.java
//
//  Author:
//       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;

import jmetal.core.Problem;
import jmetal.core.Solution;
import jmetal.encodings.solutionType.PermutationSolutionType;
import jmetal.encodings.variable.Permutation;

import java.io.*;

/**
 * Class representing a multi-objective TSP (Traveling Salesman Problem) problem.
 * This class is tested with two objectives and the KROA150 and KROB150 
 * instances of TSPLIB
 */
public class mTSP extends Problem {

  public int         numberOfCities_ ; 
  public double [][] distanceMatrix_ ;
  public double [][] costMatrix_;

  
 /**
  * Creates a new mTSP problem instance. It accepts data files from TSPLIB
  */
  public mTSP(String solutionType,
              String file_distances,
              String file_cost) throws IOException {
    numberOfVariables_  = 1;
    numberOfObjectives_ = 2;
    numberOfConstraints_= 0;
    problemName_        = "mTSP";
             
    //variableType_ = new Class[numberOfVariables_] ;
    length_       = new int[numberOfVariables_];
    
    //variableType_[0] = Class.forName("jmetal.base.encodings.variable.Permutation") ;
    
    distanceMatrix_ = readProblem(file_distances) ;
    costMatrix_     = readProblem(file_cost);
    System.out.println(numberOfCities_) ;
    length_      [0] = numberOfCities_ ;
    if (solutionType.compareTo("Permutation") == 0)
    	solutionType_ = new PermutationSolutionType(this) ;
    else {
    	System.out.println("Error: solution type " + solutionType + " invalid") ;
    	System.exit(-1) ;
    }
  } // mTSP
    
 /** 
  * Evaluates a solution 
  * @param solution The solution to evaluate
  */      
  public void evaluate(Solution solution) {
    double fitness1   ;
    double fitness2   ;
    
    fitness1   = 0.0 ;
    fitness2   = 0.0 ;

    for (int i = 0; i < (numberOfCities_ - 1); i++) {
      int x ; 
      int y ;
      
      x = ((Permutation)solution.getDecisionVariables()[0]).vector_[i] ;
      y = ((Permutation)solution.getDecisionVariables()[0]).vector_[i+1] ;
//  cout << "I : " << i << ", x = " << x << ", y = " << y << endl ;    
      fitness1 += distanceMatrix_[x][y] ;
      fitness2 += costMatrix_[x][y];
    } // for
    int firstCity ;
    int lastCity  ;
    
    firstCity = ((Permutation)solution.getDecisionVariables()[0]).vector_[0] ;
    lastCity  = ((Permutation)solution.getDecisionVariables()[0]).vector_[numberOfCities_ - 1] ;
    fitness1 += distanceMatrix_[firstCity][lastCity] ;
    fitness2 += costMatrix_[firstCity][lastCity];
    
    solution.setObjective(0, fitness1);            
    solution.setObjective(1, fitness2);
  } // evaluate


  public double [][] readProblem(String file) throws
          IOException {
    double [][] matrix = null;
    Reader inputFile = new BufferedReader(
                       new InputStreamReader(
                       new FileInputStream(file)));

    StreamTokenizer token = new StreamTokenizer(inputFile);
    try {
      boolean found ;
      found = false ;
      
      token.nextToken();
      while(!found) {
        if ((token.sval != null) && ((token.sval.compareTo("DIMENSION") == 0)))
          found = true ;
        else
          token.nextToken() ;
      } // while

      token.nextToken() ;
      token.nextToken() ;
      
      numberOfCities_ =  (int)token.nval ;

      matrix = new double[numberOfCities_][numberOfCities_] ;

      // Find the string SECTION  
      found = false ;
      token.nextToken();
      while(!found) {
        if ((token.sval != null) &&
           ((token.sval.compareTo("SECTION") == 0)))
          found = true ;
        else
          token.nextToken() ;
      } // while

    // Read the data

      double [] c = new double[2*numberOfCities_] ;

      for (int i = 0; i < numberOfCities_; i++) {
        token.nextToken() ;
        int j = (int)token.nval ;

        token.nextToken() ;
        c[2*(j-1)] = token.nval ;
        token.nextToken() ;
        c[2*(j-1)+1] = token.nval ;
      } // for

      double dist ;
      for (int k = 0; k < numberOfCities_; k++) {
        matrix[k][k] = 0;
        for (int j = k + 1; j < numberOfCities_; j++) {
          dist = Math.sqrt(Math.pow((c[k*2]-c[j*2]),2.0) +
              Math.pow((c[k*2+1]-c[j*2+1]), 2));
          dist = (int)(dist + .5);
          matrix[k][j] = dist;
          matrix[j][k] = dist;
        } // for
      } // for
    } // try
    catch (Exception e) { 
      System.err.println ("TSP.readProblem(): error when reading data file "+e);
      System.exit(1);
    } // catch
    return matrix;
  } // readProblem
} // mTSP