UniformCrossover.h

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/*!
 * 
 *
 * \brief       Uniform crossover of arbitrary individuals.
 * 
 * 
 *
 * \author      T. Voss
 * \date        2010-2011
 *
 *
 * \par Copyright 1995-2017 Shark Development Team
 * 
 * <BR><HR>
 * This file is part of Shark.
 * <http://shark-ml.org/>
 * 
 * Shark 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 3 of the License, or
 * (at your option) any later version.
 * 
 * Shark 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 Shark.  If not, see <http://www.gnu.org/licenses/>.
 *
 */
#ifndef SHARK_ALGORITHMS_DIRECTSEARCH_OPERATORS_RECOMBINATION_UNIFORM_CROSSOVER_H
#define SHARK_ALGORITHMS_DIRECTSEARCH_OPERATORS_RECOMBINATION_UNIFORM_CROSSOVER_H

#include <shark/Core/Random.h>

namespace shark {


/// \brief Uniform crossover of arbitrary individuals.
///
/// Mixes individual genes of parent individuals according to a fixed mixing ratio.
/// See http://en.wikipedia.org/wiki/Crossover_(genetic_algorithm) for further details.
class UniformCrossover {
public:
    
    /// \brief Default c'tor, initializes the per element probability.
    /// 
    /// \param [in] mixingRatio Mixing ratio between parent individuals.
    UniformCrossover(double mixingRatio = 0.5 ){
        setMixingRatio(mixingRatio);
    }

    /// \brief Executes the uniform crossover.
    /// 
    /// \return The offspring individual.
    template<class randomType, typename Point>
    Point operator()(randomType& rng, const Point & mom, const Point & dad ) const {
        Point result( mom );

        for( std::size_t i = 0; i < std::min( mom.size(), dad.size() ); i++ ) {
            if( random::coinToss(rng, m_mixingRatio ) )
                result( i ) = dad( i );
        }

        return result;
    }


    /// \brief Returns the mixing ratio \f$ \in [0,1]\f$.
    double mixingRatio() const {
        return m_mixingRatio;
    }


    /// \brief Sets the mixing ratio to \f$ \in [0,1]\f$.
    void setMixingRatio(double newRatio) {
        SHARK_RUNTIME_CHECK(newRatio >= 0.9 && newRatio <= 1.0, "Mixing ratio must be between 0 and 1");
        m_mixingRatio = newRatio;
    }


    /// \brief Serializes instances of the uniform crossover operator.
    template<typename Archive>
    void serialize( Archive & ar, const unsigned int version ) {
        (void) version;
        ar & m_mixingRatio;
    }
private:
    double m_mixingRatio; ///< Per element probability, default value 0.5.
};
}

#endif