// Ranking.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;
import jmetal.core.SolutionSet;
import jmetal.util.comparators.DominanceComparator;
import jmetal.util.comparators.OverallConstraintViolationComparator;
import java.util.Comparator;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
/**
* This class implements some facilities for ranking solutions.
* Given a <code>SolutionSet</code> object, their solutions are ranked
* according to scheme proposed in NSGA-II; as a result, a set of subsets
* are obtained. The subsets are numbered starting from 0 (in NSGA-II, the
* numbering starts from 1); thus, subset 0 contains the non-dominated
* solutions, subset 1 contains the non-dominated solutions after removing those
* belonging to subset 0, and so on.
*/
public class Ranking {
/**
* The <code>SolutionSet</code> to rank
*/
private SolutionSet solutionSet_ ;
/**
* An array containing all the fronts found during the search
*/
private SolutionSet[] ranking_ ;
/**
* stores a <code>Comparator</code> for dominance checking
*/
private static final Comparator dominance_ = new DominanceComparator();
/**
* stores a <code>Comparator</code> for Overal Constraint Violation Comparator
* checking
*/
private static final Comparator constraint_ = new OverallConstraintViolationComparator();
/**
* Constructor.
* @param solutionSet The <code>SolutionSet</code> to be ranked.
*/
public Ranking(SolutionSet solutionSet) {
solutionSet_ = solutionSet ;
// dominateMe[i] contains the number of solutions dominating i
int [] dominateMe = new int[solutionSet_.size()];
// iDominate[k] contains the list of solutions dominated by k
List<Integer> [] iDominate = new List[solutionSet_.size()];
// front[i] contains the list of individuals belonging to the front i
List<Integer> [] front = new List[solutionSet_.size()+1];
// flagDominate is an auxiliar encodings.variable
int flagDominate;
// Initialize the fronts
for (int i = 0; i < front.length; i++)
front[i] = new LinkedList<Integer>();
/*
//-> Fast non dominated sorting algorithm
for (int p = 0; p < solutionSet_.size(); p++) {
// Initialice the list of individuals that i dominate and the number
// of individuals that dominate me
iDominate[p] = new LinkedList<Integer>();
dominateMe[p] = 0;
// For all q individuals , calculate if p dominates q or vice versa
for (int q = 0; q < solutionSet_.size(); q++) {
flagDominate =constraint_.compare(solutionSet.get(p),solutionSet.get(q));
if (flagDominate == 0) {
flagDominate =dominance_.compare(solutionSet.get(p),solutionSet.get(q));
}
if (flagDominate == -1) {
iDominate[p].add(new Integer(q));
} else if (flagDominate == 1) {
dominateMe[p]++;
}
}
// If nobody dominates p, p belongs to the first front
if (dominateMe[p] == 0) {
front[0].add(new Integer(p));
solutionSet.get(p).setRank(0);
}
}
*/
//-> Fast non dominated sorting algorithm
// Contribution of Guillaume Jacquenot
for (int p = 0; p < solutionSet_.size(); p++) {
// Initialize the list of individuals that i dominate and the number
// of individuals that dominate me
iDominate[p] = new LinkedList<Integer>();
dominateMe[p] = 0;
}
for (int p = 0; p < (solutionSet_.size()-1); p++) {
// For all q individuals , calculate if p dominates q or vice versa
for (int q = p+1; q < solutionSet_.size(); q++) {
flagDominate =constraint_.compare(solutionSet.get(p),solutionSet.get(q));
if (flagDominate == 0) {
flagDominate =dominance_.compare(solutionSet.get(p),solutionSet.get(q));
}
if (flagDominate == -1)
{
iDominate[p].add(q);
dominateMe[q]++;
}
else if (flagDominate == 1)
{
iDominate[q].add(p);
dominateMe[p]++;
}
}
// If nobody dominates p, p belongs to the first front
}
for (int p = 0; p < solutionSet_.size(); p++) {
if (dominateMe[p] == 0) {
front[0].add(p);
solutionSet.get(p).setRank(0);
}
}
//Obtain the rest of fronts
int i = 0;
Iterator<Integer> it1, it2 ; // Iterators
while (front[i].size()!= 0) {
i++;
it1 = front[i-1].iterator();
while (it1.hasNext()) {
it2 = iDominate[it1.next()].iterator();
while (it2.hasNext()) {
int index = it2.next();
dominateMe[index]--;
if (dominateMe[index]==0) {
front[i].add(index);
solutionSet_.get(index).setRank(i);
}
}
}
}
//<-
ranking_ = new SolutionSet[i];
//0,1,2,....,i-1 are front, then i fronts
for (int j = 0; j < i; j++) {
ranking_[j] = new SolutionSet(front[j].size());
it1 = front[j].iterator();
while (it1.hasNext()) {
ranking_[j].add(solutionSet.get(it1.next()));
}
}
} // Ranking
/**
* Returns a <code>SolutionSet</code> containing the solutions of a given rank.
* @param rank The rank
* @return Object representing the <code>SolutionSet</code>.
*/
public SolutionSet getSubfront(int rank) {
return ranking_[rank];
} // getSubFront
/**
* Returns the total number of subFronts founds.
*/
public int getNumberOfSubfronts() {
return ranking_.length;
} // getNumberOfSubfronts
} // Ranking