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Added ranking selection (eoRankingSelect) and (linear) fitness scaling in

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proportional selection (a completely different file, eoFitnessScalingSelect.h)
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evomarc 2001-01-25 16:13:15 +00:00
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eo/src/eoRankingSelect.h Normal file
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// -*- mode: c++; c-indent-level: 4; c++-member-init-indent: 8; comment-column: 35; -*-
//-----------------------------------------------------------------------------
// eoRankingSelect.h
// (c) GeNeura Team, 1998, Maarten Keijzer 2000, Marc Schoenauer 2001
/*
This library 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 2 of the License, or (at your option) any later version.
This library 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 library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
Contact: todos@geneura.ugr.es, http://geneura.ugr.es
Marc.Schoenauer@polytechnique.fr
mak@dhi.dk
*/
//-----------------------------------------------------------------------------
#ifndef eoRankingSelect_h
#define eoRankingSelect_h
//-----------------------------------------------------------------------------
#include <utils/eoRNG.h>
#include <utils/selectors.h>
#include <eoSelectOne.h>
//-----------------------------------------------------------------------------
/** eoRankingSelect: select an individual proportional to its rank
this is actually the linearRanking
*/
//-----------------------------------------------------------------------------
template <class EOT> class eoRankingSelect: public eoSelectOne<EOT>
{
public:
/** Ctor:
* @param _p the selective pressure, should be in [1,2] (2 is the default)
* @param _pop an optional population
*/
eoRankingSelect(double _p = 2.0, const eoPop<EOT>& _pop = eoPop<EOT>()):
pressure(_p), rank(0), rankFitness(0)
{
if (_pop.size() > 0)
{
setup(_pop);
}
}
// COmputes the coefficients of the linear transform uin such a way that
// Pselect(Best) == Pselect(sizePop) == pressure/sizePop
// Pselect(average) == 1.0/sizePop
// Pselect(Worst == Pselect(1 == (2-pressure)/sizePop
void setup(const eoPop<EOT>& _pop)
{
_pop.sort(rank);
unsigned pSize =_pop.size();
rankFitness.resize(pSize);
double alpha = (2*pressure-2)/(pSize*(pSize-1));
double beta = (2-pressure)/pSize;
for (unsigned i=0; i<pSize; i++)
{
rankFitness[i] = alpha*(pSize-1-i)+beta;
}
}
/** do the selection, call roulette_wheel on rankFitness
*/
const EOT& operator()(const eoPop<EOT>& _pop)
{
unsigned selected = rng.roulette_wheel(rankFitness);
return *(rank[selected]);
}
private :
double pressure;
vector<const EOT *> rank;
vector<double> rankFitness;
};
#endif