[Paradiseo-help] Paradiseo-MOEO: diversity preservation

Romanas Puisa rpuisa at gmail.com
Jeu 22 Avr 13:13:11 CEST 2010


Hi,

Thanks for the clarification. As for your question: the individual are the
same in both search spaces, i.e. they are identical.

Cheers
Romas

On 21 April 2010 16:26, paradiseo-help <paradiseo-help at lists.gforge.inria.fr
> wrote:

> Hi,
>
> The replacement strategy is build with the fitness and the diversity
> assignment strategies. So they are called each generations.
>
> You can try IBEA or SPEA2 to see if you obtain the same results.
>
> Individuals are the same in objective space or in search space?
>
> Regards, paradiseo Team.
>
> Romanas Puisa a écrit :
>
>> Hi there,
>>
>> I'm using Paradiseo-MOEO for  constrained multiobjective optimisation. The
>> problem I have is that my population tends to become uniform (all or almost
>> all invididual are the same) from time to time during the search, probably
>> once local optima are reached.
>> I'm running NSGAII which uses
>> 'moeoFrontByFrontCrowdingDiversityAssignment' for diversity preservation.
>> There are surely also a possibility to use other methdos like the partent
>> class 'moeoCrowdingDiversityAssignment' instead. I've tried to do this (by
>> reimplementing NSGAII) but it does not seem helpful.
>>
>> I've looked at  the  NSGAII implementation, and in particualar at the
>> method
>>
>> virtual void operator ()  <
>> http://paradiseo.gforge.inria.fr/addon/paradiseo-moeo/doc/classmoeoNSGAII.html#60ba3ed4287efe81e1ff66b22e1d2e14>(eoPop
>> < MOEOT > &_pop)
>>
>>
>> 00133     {
>> 00134         eoPop < MOEOT > offspring, empty_pop;
>> 00135         popEval <
>> http://paradiseo.gforge.inria.fr/addon/paradiseo-moeo/doc/classmoeoNSGAII.html#2926b2c13fbf66aa34ca8bb2d1268df4>
>> (empty_pop, _pop);      // a first eval of _pop
>>
>>
>> 00136         // evaluate fitness and diversity
>> 00137         fitnessAssignment <
>> http://paradiseo.gforge.inria.fr/addon/paradiseo-moeo/doc/classmoeoNSGAII.html#20fd563da176b72275be7f843c4aac7f
>> >(_pop);
>>
>> 00138         diversityAssignment <
>> http://paradiseo.gforge.inria.fr/addon/paradiseo-moeo/doc/classmoeoNSGAII.html#4abf4583668c6f145f4dbb0a24d2dae0
>> >(_pop);
>>
>>
>> 00139         do
>> 00140         {
>> 00141             // generate offspring, worths are recalculated if
>> necessary
>>
>> 00142             breed <
>> http://paradiseo.gforge.inria.fr/addon/paradiseo-moeo/doc/classmoeoNSGAII.html#17954849435e579d74bf37ed7b9063fc>
>> (_pop, offspring);
>>
>> 00143             // eval of offspring
>> 00144             popEval <
>> http://paradiseo.gforge.inria.fr/addon/paradiseo-moeo/doc/classmoeoNSGAII.html#2926b2c13fbf66aa34ca8bb2d1268df4>
>> (_pop, offspring);
>>
>>
>> 00145             // after replace, the new pop is in _pop. Worths are
>> recalculated if necessary
>> 00146             replace <
>> http://paradiseo.gforge.inria.fr/addon/paradiseo-moeo/doc/classmoeoNSGAII.html#75bc4b735c5de2a6fc93b2f2b63c7251>
>> (_pop, offspring);
>>
>> 00147         }
>> 00148         while (continuator <
>> http://paradiseo.gforge.inria.fr/addon/paradiseo-moeo/doc/classmoeoNSGAII.html#7eb1e36631eebbe3216167b1077e3a53>
>> (_pop));
>>
>>
>> 00149     }
>>
>> of class 'moeoNSGAII' and found that the diversity assigment, function
>> 'diversityAssignment', is called only once, just before the main loop.
>> Perhaps there is a gap in my understanding of NSGAII, but I'd think that the
>> diversity should be maintained all the time, hence being included in the
>> main loop just after the evaluation, function popEval(). Am I correct? Could
>> you please clarify this? I'd also appreciate if you could point out possible
>> reasons of the population diversity shrinking problem I have.
>>
>> Thankful in advance,
>> romas
>>
>>
>>  ------------------------------------------------------------------------
>>
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>
>
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