// -*- mode: c++; c-indent-level: 4; c++-member-init-indent: 8; comment-column: 35; -*-

//-----------------------------------------------------------------------------
// moeoCrowdingDistanceDiversityAssignment.h
// (c) OPAC Team (LIFL), Dolphin Project (INRIA), 2007
/*
    This library...

    Contact: paradiseo-help@lists.gforge.inria.fr, http://paradiseo.gforge.inria.fr
 */
//-----------------------------------------------------------------------------

#ifndef MOEOCROWDINGDISTANCEDIVERSITYASSIGNMENT_H_
#define MOEOCROWDINGDISTANCEDIVERSITYASSIGNMENT_H_

#include <eoPop.h>
#include <moeoComparator.h>
#include <moeoDiversityAssignment.h>

/**
 * Diversity assignment sheme based on crowding distance proposed in:
 * K. Deb, A. Pratap, S. Agarwal, T. Meyarivan, "A Fast and Elitist Multi-Objective Genetic Algorithm: NSGA-II", IEEE Transactions on Evolutionary Computation, vol. 6, no. 2 (2002).
 * This strategy is, for instance, used in NSGA-II.
 */
template < class MOEOT >
class moeoCrowdingDistanceDiversityAssignment : public moeoDiversityAssignment < MOEOT >
{
public:

    /** the objective vector type of the solutions */
    typedef typename MOEOT::ObjectiveVector ObjectiveVector;


    /**
     * Returns a big value (regarded as infinite)
     */
    double inf() const
    {
        return std::numeric_limits<double>::max();
    }


    /**
     * Computes diversity values for every solution contained in the population _pop
     * @param _pop the population
     */
    void operator()(eoPop < MOEOT > & _pop)
    {
        if (_pop.size() <= 2)
        {
            for (unsigned i=0; i<_pop.size(); i++)
            {
                _pop[i].diversity(inf());
            }
        }
        else
        {
            setDistances(_pop);
        }
    }


    /**
     * @warning NOT IMPLEMENTED, DO NOTHING !
     * Updates the diversity values of the whole population _pop by taking the deletion of the objective vector _objVec into account.
     * @param _pop the population
     * @param _objVec the objective vector
     * @warning NOT IMPLEMENTED, DO NOTHING !
     */
    void updateByDeleting(eoPop < MOEOT > & _pop, ObjectiveVector & _objVec)
    {
        cout << "WARNING : updateByDeleting not implemented in moeoCrowdingDiversityAssignment" << endl;
    }


private:

    /**
     * Sets the distance values
     * @param _pop the population
     */
    void setDistances (eoPop < MOEOT > & _pop)
    {
        double min, max, distance;
        unsigned nObjectives = MOEOT::ObjectiveVector::nObjectives();
        // set diversity to 0
        for (unsigned i=0; i<_pop.size(); i++)
        {
            _pop[i].diversity(0);
        }
        // for each objective
        for (unsigned obj=0; obj<nObjectives; obj++)
        {
            // comparator
            moeoOneObjectiveComparator < MOEOT > comp(obj);
            // sort
            std::sort(_pop.begin(), _pop.end(), comp);
            // min & max
            min = _pop[0].objectiveVector()[obj];
            max = _pop[_pop.size()-1].objectiveVector()[obj];
            // set the diversity value to infiny for min and max
            _pop[0].diversity(inf());
            _pop[_pop.size()-1].diversity(inf());
            for (unsigned i=1; i<_pop.size()-1; i++)
            {
                distance = (_pop[i+1].objectiveVector()[obj] - _pop[i-1].objectiveVector()[obj]) / (max-min);
                _pop[i].diversity(_pop[i].diversity() + distance);
            }
        }
    }

};

#endif /*MOEOCROWDINGDISTANCEDIVERSITYASSIGNMENT_H_*/