ExtractParetoFront.java

//  ExtractParetoFront.java
//
//  Author:
//       Juan J. Durillo <durillo@lcc.uma.es>
//
//  Copyright (c) 2012 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;

import java.io.*;
import java.util.*;

/**
 *  This class extract the Pareto front among a set of dominated and 
 *  non-dominated solutions
 */

public class ExtractParetoFront {

	String fileName_; 
	int dimensions_;
	List<Point> points_ = new LinkedList<Point>();

	private class Point {
		double [] vector_; 

		public Point (double [] vector) {
			vector_ = vector;
		}

		public Point (int size) {
			vector_ = new double[size];
			for (int i = 0; i < size; i++)
				vector_[i] = 0.0f;
		}            

	}

	/**
	 * @author Juan J. Durillo
	 * Creates a new instance
	 * @param name: the name of the file
	 */
	public ExtractParetoFront(String name, int dimensions) {
		fileName_ = name;
		dimensions_ = dimensions;
		loadInstance();
	} // ReadInstance


	/**
	 * Read the points instance from file 
	 */
	public void loadInstance()  {

		try {
			File archivo = new File(fileName_);
			FileReader fr = null;
			BufferedReader br = null;        
			fr = new FileReader (archivo);
			br = new BufferedReader(fr);

			// File reading
			String line;
			int lineCnt = 0;
			line = br.readLine(); // reading the first line (special case)     

			while (line!=null) {
				StringTokenizer st = new StringTokenizer(line);
				try {
					Point auxPoint = new Point(dimensions_);
					for (int i = 0; i < dimensions_; i++) {
						auxPoint.vector_[i] = new Double(st.nextToken());
					}

					add(auxPoint);

					line = br.readLine();
					lineCnt++;
				} catch (NumberFormatException e) {
					System.err.println("Number in a wrong format in line "+lineCnt);
					System.err.println(line);
					line = br.readLine();
					lineCnt++;
				} catch (NoSuchElementException e2) {
					System.err.println("Line "+lineCnt+" does not have the right number of objectives");
					System.err.println(line);
					line = br.readLine();
					lineCnt++;
				}
			}
			br.close();
		} catch (FileNotFoundException e3) {
			System.err.println("The file " + fileName_+ " has not been found in your file system");
		}  catch (IOException e3) {
			System.err.println("The file " + fileName_+ " has not been found in your file system");
		}

	} // loadInstance


	public void add(Point point) {
		Iterator<Point> iterator = points_.iterator();


		while (iterator.hasNext()){
			Point auxPoint = iterator.next();
			int flag = compare(point,auxPoint);

			if (flag == -1) {  // A solution in the list is dominated by the new one
				iterator.remove();

			} else if (flag == 1) { // The solution is dominated
				return;
			}        
		} // while
		points_.add(point);

	} // add                   


	public int compare(Point one, Point two) {
		int flag1 = 0, flag2 = 0;
		for (int i = 0; i < dimensions_; i++) {
			if (one.vector_[i] < two.vector_[i])
				flag1 = 1;

			if (one.vector_[i] > two.vector_[i])
				flag2 = 1;
		}

		if (flag1 > flag2) // one dominates
		return -1;

		if (flag2 > flag1) // two dominates
			return 1;

		return 0; // both are non dominated
	}


	public void writeParetoFront() {
		try {    
			/* Open the file */
			FileOutputStream fos   = new FileOutputStream(fileName_+".pf") ;
			OutputStreamWriter osw = new OutputStreamWriter(fos)    ;
			BufferedWriter bw      = new BufferedWriter(osw)        ;

      for (Point auxPoint : points_) {
        String aux = "";

        for (int i = 0; i < auxPoint.vector_.length; i++) {
          aux += auxPoint.vector_[i] + " ";

        }
        bw.write(aux);
        bw.newLine();
      }

			/* Close the file */
			bw.close();
		}catch (IOException e) {        
			e.printStackTrace();
		}       
	}

	public static void main(String [] args) {
		if (args.length != 2) {
			System.out.println("Wrong number of arguments: ");
			System.out.println("Sintaxt: java ExtractParetoFront <file> <dimensions>");
			System.out.println("\t<file> is a file containing points");
			System.out.println("\t<dimensions> represents the number of dimensions of the problem");
			System.exit(-1) ;
		}

		ExtractParetoFront epf = new ExtractParetoFront(args[0], new Integer(args[1]));

		epf.writeParetoFront();
	}
}