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

//-----------------------------------------------------------------------------
// eoLottery.h
//   Implements the lottery procedure for selection
// (c) GeNeura Team, 1998 - Marc Schoenauer, 2000
/* 
    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
 */
//-----------------------------------------------------------------------------

#ifndef eoLottery_h
#define eoLottery_h

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

#include <functional>  // 
#include <numeric>     // accumulate
#include "eoPopOps.h"
#include "eoRNG.h"

//-----------------------------------------------------------------------------
/// eoLottery: a selection method.
/// requires EOT::Fitness to be float castable
//-----------------------------------------------------------------------------

template<class EOT> class eoLottery: public eoBinPopOp<EOT>
{
 public:
  /// (Default) Constructor.
  eoLottery(const double & _rate = 1.0): rate(_rate) {}
  
    /** actually selects individuals from pop and put them into breeders
     *  until breeders has the right size: rate*pop.size()
     *  BUT what happens if breeders is already too big?
     */
  void operator()( eoPop<EOT>& pop, eoPop<EOT>& breeders) 
    {
      // scores of chromosomes
      vector<double> score(pop.size());

      // calculates total scores for chromosomes
      double total = 0;
      for (unsigned i = 0; i < pop.size(); i++) {
	score[i] = static_cast<double>(pop[i].fitness()); 
	total += score[i];
      }

      // number of offspring needed
      int target = (int)rint(rate * pop.size());

      // test of consistency
      if (breeders.size() >= target) {
	  throw("Problem in eoLottery: already too many offspring");
      }

      // selection of chromosomes
      while (breeders.size() < target) {
	  unsigned indloc = rng.roulette_wheel(score, total);
	  breeders.push_back(pop[indloc]);
      }
    }

    /// accessor to private rate
    double Rate() {return rate;}

  /** @name Methods from eoObject	*/
  //@{
  /** readFrom and printOn inherited from eoMerge */
  
  /** Inherited from eoObject. Returns the class name.
      @see eoObject
  */
  virtual string className() const {return "eoLottery";};
  //@}
  
 private:
  double rate;  // selection rate
};

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

#endif eoLottery_h