112 lines
3.8 KiB
C++
112 lines
3.8 KiB
C++
/** -*- mode: c++; c-indent-level: 4; c++-member-init-indent: 8; comment-column: 35; -*-
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-----------------------------------------------------------------------------
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eoRanking.h
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(c) Maarten Keijzer, Marc Schoenauer, 2001
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with this library; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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Contact: todos@geneura.ugr.es, http://geneura.ugr.es
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Marc.Schoenauer@polytechnique.fr
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mkeijzer@dhi.dk
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*/
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//-----------------------------------------------------------------------------
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#ifndef eoRanking_h
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#define eoRanking_h
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#include "eoPerf2Worth.h"
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/** An instance of eoPerfFromWorth
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* COmputes the ranked fitness: fitnesses range in [m,M]
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* with m=2-pressure/popSize and M=pressure/popSize.
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* in between, the progression depstd::ends on exponent (linear if 1).
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*
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* @ingroup Selectors
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*/
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template <class EOT>
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class eoRanking : public eoPerf2Worth<EOT> // false: do not cache fitness
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{
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public:
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using eoPerf2Worth<EOT>::value;
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/* Ctor:
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@param _p selective pressure (in (1,2]
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@param _e exponent (1 == linear)
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*/
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eoRanking(double _p = 2.0, double _e = 1.0) : pressure(_p), exponent(_e)
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{
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assert(1 < pressure and exponent <= 2);
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}
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/* helper function: finds index in _pop of _eo, an EOT * */
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int lookfor(const EOT *_eo, const eoPop<EOT> &_pop)
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{
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typename eoPop<EOT>::const_iterator it;
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for (it = _pop.begin(); it < _pop.end(); it++)
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{
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if (_eo == &(*it))
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return it - _pop.begin();
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}
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throw eoException("Not found in eoLinearRanking");
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}
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/* COmputes the ranked fitness: fitnesses range in [m,M]
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with m=2-pressure/popSize and M=pressure/popSize.
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in between, the progression depstd::ends on exponent (linear if 1).
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*/
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virtual void operator()(const eoPop<EOT> &_pop)
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{
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std::vector<const EOT *> rank;
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_pop.sort(rank);
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unsigned pSize = _pop.size();
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unsigned int pSizeMinusOne = pSize - 1;
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if (pSize <= 1)
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throw eoPopSizeException(pSize, "cannot do ranking with population of size <= 1");
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// value() refers to the std::vector of worthes (we're in an eoParamvalue)
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value().resize(pSize);
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double beta = (2 - pressure) / pSize;
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if (exponent == 1.0) // no need for exponential then
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{
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double alpha = (2 * pressure - 2) / (pSize * pSizeMinusOne);
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for (unsigned i = 0; i < pSize; i++)
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{
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int which = lookfor(rank[i], _pop);
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value()[which] = alpha * (pSize - i) + beta; // worst -> 1/[P(P-1)/2]
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}
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}
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else // exponent != 1
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{
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double gamma = (2 * pressure - 2) / pSize;
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for (unsigned i = 0; i < pSize; i++)
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{
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int which = lookfor(rank[i], _pop);
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// value is in [0,1]
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double tmp = ((double)(pSize - i)) / pSize;
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// to the exponent, and back to [m,M]
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value()[which] = gamma * pow(tmp, exponent) + beta;
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}
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}
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}
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private:
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double pressure; // selective pressure
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double exponent;
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};
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#endif
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