eomerge.h

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

//-----------------------------------------------------------------------------
// eoMerge.h
//   Base class for elitist-merging classes
// (c) GeNeura Team, 1998
/* 
   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: [e-mail], http://geneura.ugr.es
 */
//-----------------------------------------------------------------------------

#ifndef eoMerge_h
#define eoMerge_h

//-----------------------------------------------------------------------------

#include <stdexcept>

// EO includes
#include <eoPop.h>     // eoPop
#include <eoFunctor.h>  // eoMerge

/**
 * eoMerge: Base class for elitist replacement algorithms. 
 * Merges the old population (first argument), with the new generation
 *
 * Its signature is exactly
 * that of the selection base eoSelect, but its purpose is to merge the 
 * two populations into one (the second argument).
 * Note that the algorithms assume that the second argument denotes the 
 * next generation.
*/

template<class Chrom> class eoMerge: public eoBF<const eoPop<Chrom>&, eoPop<Chrom>&, void>
{};

/**
Straightforward elitism class, specify the number of individuals to copy
into new geneneration or the rate w.r.t. pop size
*/
template <class EOT> class eoElitism : public eoMerge<EOT>
{
public :
  eoElitism(double  _rate, bool _interpret_as_rate = true):
    rate(0), combien(0)
  {
    if (_interpret_as_rate)
      {
	if ( (_rate<0) || (_rate>1) )
	  throw std::logic_error("eoElitism: rate shoud be in [0,1]");
	rate = _rate;
      }
    else
      {
	if (_rate<0)
	  throw std::logic_error("Negative number of offspring in eoElitism!");
	combien = (unsigned int)_rate;
	if (combien != _rate)
	  std::cout << "Warning: Number of guys to merge in eoElitism was rounded";
      }
  }
  
  void operator()(const eoPop<EOT>& _pop, eoPop<EOT>& _offspring)
  {
    if ((combien == 0) && (rate == 0.0))
      return;
    unsigned combienLocal;
    if (combien == 0)	   // rate is specified
      combienLocal = (unsigned int) (rate * _pop.size());
    else
      combienLocal = combien;
    
    if (combienLocal > _pop.size())
      throw std::logic_error("Elite larger than population");
    
    std::vector<const EOT*> result;
    _pop.nth_element(combienLocal, result);
    
    for (size_t i = 0; i < result.size(); ++i)
      {
	_offspring.push_back(*result[i]);
      }
  }
  
private :
  double rate;
  unsigned combien;
};

/**
No elite
*/
template <class EOT> class eoNoElitism : public eoElitism<EOT>
{
    public :
        eoNoElitism() : eoElitism<EOT>(0) {}
};

/**
Very elitist class, copies entire population into next gen
*/
template <class EOT> class eoPlus : public eoMerge<EOT>
{
    public :
        void operator()(const eoPop<EOT>& _pop, eoPop<EOT>& _offspring)
        {
            _offspring.reserve(_offspring.size() + _pop.size());

            for (size_t i = 0; i < _pop.size(); ++i)
            {
                _offspring.push_back(_pop[i]);
            }
        }

    private :
};

//-----------------------------------------------------------------------------

#endif