moeoFrontByFrontCrowdingDiversityAssignment.h

/* 
* <moeoFrontByFrontCrowdingDiversityAssignment.h>
* Copyright (C) DOLPHIN Project-Team, INRIA Futurs, 2006-2007
* (C) OPAC Team, LIFL, 2002-2007
*
* Arnaud Liefooghe
*
* This software is governed by the CeCILL license under French law and
* abiding by the rules of distribution of free software.  You can  use,
* modify and/ or redistribute the software under the terms of the CeCILL
* license as circulated by CEA, CNRS and INRIA at the following URL
* "http://www.cecill.info".
*
* As a counterpart to the access to the source code and  rights to copy,
* modify and redistribute granted by the license, users are provided only
* with a limited warranty  and the software's author,  the holder of the
* economic rights,  and the successive licensors  have only  limited liability.
*
* In this respect, the user's attention is drawn to the risks associated
* with loading,  using,  modifying and/or developing or reproducing the
* software by the user in light of its specific status of free software,
* that may mean  that it is complicated to manipulate,  and  that  also
* therefore means  that it is reserved for developers  and  experienced
* professionals having in-depth computer knowledge. Users are therefore
* encouraged to load and test the software's suitability as regards their
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* same conditions as regards security.
* The fact that you are presently reading this means that you have had
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*
* ParadisEO WebSite : http://paradiseo.gforge.inria.fr
* Contact: paradiseo-help@lists.gforge.inria.fr
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*/
//-----------------------------------------------------------------------------

#ifndef MOEOFRONTBYFRONTCROWDINGDIVERSITYASSIGNMENT_H_
#define MOEOFRONTBYFRONTCROWDINGDIVERSITYASSIGNMENT_H_

#include <diversity/moeoCrowdingDiversityAssignment.h>
#include <comparator/moeoFitnessThenDiversityComparator.h>

template < class MOEOT >
class moeoFrontByFrontCrowdingDiversityAssignment : public moeoCrowdingDiversityAssignment < MOEOT >
{
public:

    typedef typename MOEOT::ObjectiveVector ObjectiveVector;


    void updateByDeleting(eoPop < MOEOT > & _pop, ObjectiveVector & _objVec)
    {
        std::cout << "WARNING : updateByDeleting not implemented in moeoFrontByFrontCrowdingDistanceDiversityAssignment" << std::endl;
    }


private:

    using moeoCrowdingDiversityAssignment < MOEOT >::inf;
    using moeoCrowdingDiversityAssignment < MOEOT >::tiny;

    void setDistances (eoPop < MOEOT > & _pop)
    {
        unsigned int a,b;
        double min, max, distance;
        unsigned int nObjectives = MOEOT::ObjectiveVector::nObjectives();
        // set diversity to 0 for every individual
        for (unsigned int i=0; i<_pop.size(); i++)
        {
            _pop[i].diversity(0.0);
        }
        // sort the whole pop according to fitness values
        moeoFitnessThenDiversityComparator < MOEOT > fitnessComparator;
        std::sort(_pop.begin(), _pop.end(), fitnessComparator);
        // compute the crowding distance values for every individual "front" by "front" (front : from a to b)
        a = 0;                                  // the front starts at a
        while (a < _pop.size())
        {
            b = lastIndex(_pop,a);      // the front ends at b
            // if there is less than 2 individuals in the front...
            if ((b-a) < 2)
            {
                for (unsigned int i=a; i<=b; i++)
                {
                    _pop[i].diversity(inf());
                }
            }
            // else...
            else
            {
                // for each objective
                for (unsigned int obj=0; obj<nObjectives; obj++)
                {
                    // sort in the descending order using the values of the objective 'obj'
                    moeoOneObjectiveComparator < MOEOT > objComp(obj);
                    std::sort(_pop.begin()+a, _pop.begin()+b+1, objComp);
                    // min & max
                    min = _pop[b].objectiveVector()[obj];
                    max = _pop[a].objectiveVector()[obj];
                    // avoid extreme case
                    if (min == max)
                    {
                        min -= tiny();
                        max += tiny();
                    }
                    // set the diversity value to infiny for min and max
                    _pop[a].diversity(inf());
                    _pop[b].diversity(inf());
                    // set the diversity values for the other individuals
                    for (unsigned int i=a+1; i<b; i++)
                    {
                        distance = (_pop[i-1].objectiveVector()[obj] - _pop[i+1].objectiveVector()[obj]) / (max-min);
                        _pop[i].diversity(_pop[i].diversity() + distance);
                    }
                }
            }
            // go to the next front
            a = b+1;
        }
    }


    unsigned int lastIndex (eoPop < MOEOT > & _pop, unsigned int _start)
    {
        unsigned int i=_start;
        while ( (i<_pop.size()-1) && (_pop[i].fitness()==_pop[i+1].fitness()) )
        {
            i++;
        }
        return i;
    }

};

#endif /*MOEOFRONTBYFRONTCROWDINGDIVERSITYASSIGNMENT_H_*/

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