b6c8d1986c
git-svn-id: svn://scm.gforge.inria.fr/svnroot/paradiseo@375 331e1502-861f-0410-8da2-ba01fb791d7f
133 lines
5 KiB
C++
133 lines
5 KiB
C++
// -*- mode: c++; c-indent-level: 4; c++-member-init-indent: 8; comment-column: 35; -*-
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//-----------------------------------------------------------------------------
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// moeoFrontByFrontCrowdingDistanceDiversityAssignment.h
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// (c) OPAC Team (LIFL), Dolphin Project (INRIA), 2007
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/*
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This library...
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Contact: paradiseo-help@lists.gforge.inria.fr, http://paradiseo.gforge.inria.fr
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*/
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//-----------------------------------------------------------------------------
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#ifndef MOEOFRONTBYFRONTCROWDINGDISTANCEDIVERSITYASSIGNMENT_H_
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#define MOEOFRONTBYFRONTCROWDINGDISTANCEDIVERSITYASSIGNMENT_H_
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#include <diversity/moeoCrowdingDistanceDiversityAssignment.h>
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#include <comparator/moeoFitnessThenDiversityComparator.h>
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/**
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* Diversity assignment sheme based on crowding distance proposed in:
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* 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).
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* Tis strategy assigns diversity values FRONT BY FRONT. It is, for instance, used in NSGA-II.
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*/
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template < class MOEOT >
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class moeoFrontByFrontCrowdingDistanceDiversityAssignment : public moeoCrowdingDistanceDiversityAssignment < MOEOT >
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{
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public:
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/** the objective vector type of the solutions */
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typedef typename MOEOT::ObjectiveVector ObjectiveVector;
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/**
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* @warning NOT IMPLEMENTED, DO NOTHING !
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* Updates the diversity values of the whole population _pop by taking the deletion of the objective vector _objVec into account.
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* @param _pop the population
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* @param _objVec the objective vector
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* @warning NOT IMPLEMENTED, DO NOTHING !
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*/
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void updateByDeleting(eoPop < MOEOT > & _pop, ObjectiveVector & _objVec)
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{
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std::cout << "WARNING : updateByDeleting not implemented in moeoFrontByFrontCrowdingDistanceDiversityAssignment" << std::endl;
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}
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private:
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using moeoCrowdingDistanceDiversityAssignment < MOEOT >::inf;
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using moeoCrowdingDistanceDiversityAssignment < MOEOT >::tiny;
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/**
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* Sets the distance values
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* @param _pop the population
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*/
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void setDistances (eoPop < MOEOT > & _pop)
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{
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unsigned int a,b;
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double min, max, distance;
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unsigned int nObjectives = MOEOT::ObjectiveVector::nObjectives();
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// set diversity to 0 for every individual
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for (unsigned int i=0; i<_pop.size(); i++)
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{
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_pop[i].diversity(0.0);
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}
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// sort the whole pop according to fitness values
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moeoFitnessThenDiversityComparator < MOEOT > fitnessComparator;
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std::sort(_pop.begin(), _pop.end(), fitnessComparator);
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// compute the crowding distance values for every individual "front" by "front" (front : from a to b)
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a = 0; // the front starts at a
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while (a < _pop.size())
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{
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b = lastIndex(_pop,a); // the front ends at b
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// if there is less than 2 individuals in the front...
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if ((b-a) < 2)
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{
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for (unsigned int i=a; i<=b; i++)
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{
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_pop[i].diversity(inf());
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}
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}
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// else...
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else
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{
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// for each objective
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for (unsigned int obj=0; obj<nObjectives; obj++)
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{
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// sort in the descending order using the values of the objective 'obj'
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moeoOneObjectiveComparator < MOEOT > objComp(obj);
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std::sort(_pop.begin()+a, _pop.begin()+b+1, objComp);
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// min & max
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min = _pop[b].objectiveVector()[obj];
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max = _pop[a].objectiveVector()[obj];
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// avoid extreme case
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if (min == max)
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{
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min -= tiny();
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max += tiny();
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}
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// set the diversity value to infiny for min and max
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_pop[a].diversity(inf());
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_pop[b].diversity(inf());
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// set the diversity values for the other individuals
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for (unsigned int i=a+1; i<b; i++)
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{
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distance = (_pop[i-1].objectiveVector()[obj] - _pop[i+1].objectiveVector()[obj]) / (max-min);
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_pop[i].diversity(_pop[i].diversity() + distance);
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}
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}
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}
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// go to the next front
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a = b+1;
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}
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}
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/**
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* Returns the index of the last individual having the same fitness value than _pop[_start]
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* @param _pop the population
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* @param _start the index to start from
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*/
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unsigned int lastIndex (eoPop < MOEOT > & _pop, unsigned int _start)
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{
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unsigned int i=_start;
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while ( (i<_pop.size()-1) && (_pop[i].fitness()==_pop[i+1].fitness()) )
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{
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i++;
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}
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return i;
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}
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};
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#endif /*MOEOFRONTBYFRONTCROWDINGDISTANCEDIVERSITYASSIGNMENT_H_*/
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