ZDT4.h

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//===========================================================================
/*!
 * 
 *
 * \brief       Multi-objective optimization benchmark function ZDT4
 * 
 * The function is described in
 * 
 * Eckart Zitzler, Kalyanmoy Deb, and Lothar Thiele. Comparison of
 * Multiobjective Evolutionary Algorithms: Empirical
 * Results. Evolutionary Computation 8(2):173-195, 2000
 * 
 * 
 *
 * \author      -
 * \date        -
 *
 *
 * \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_OBJECTIVEFUNCTIONS_BENCHMARK_ZDT4_H
#define SHARK_OBJECTIVEFUNCTIONS_BENCHMARK_ZDT4_H

#include <shark/ObjectiveFunctions/AbstractObjectiveFunction.h>
#include <shark/ObjectiveFunctions/BoxConstraintHandler.h>

namespace shark {
/*! \brief Multi-objective optimization benchmark function ZDT4
*
*  The function is described in
*  This function is highly multimodal
*
*  Eckart Zitzler, Kalyanmoy Deb, and Lothar Thiele. Comparison of
*  Multiobjective Evolutionary Algorithms: Empirical
*  Results. Evolutionary Computation 8(2):173-195, 2000
*/
struct ZDT4 : public MultiObjectiveFunction
{

    ZDT4(std::size_t numVariables = 1) {
        announceConstraintHandler(&m_handler);
        setNumberOfVariables(numVariables);
    }

    /// \brief From INameable: return the class name.
    std::string name() const
    { return "ZDT4"; }

    std::size_t numberOfObjectives()const{
        return 2;
    }
    
    std::size_t numberOfVariables()const{
        return m_handler.dimensions();
    }
    
    bool hasScalableDimensionality()const{
        return true;
    }

    /// \brief Adjusts the number of variables if the function is scalable.
    /// \param [in] numberOfVariables The new dimension.
    void setNumberOfVariables( std::size_t numberOfVariables ){
        RealVector lower(numberOfVariables,-5);
        RealVector upper(numberOfVariables,5);
        lower(0) = 0;
        upper(0) = 1;
        m_handler.setBounds(lower,upper);
    }

    ResultType eval( const SearchPointType & x ) const {
        m_evaluationCounter++;

        ResultType value( 2 );

        value[0] = x( 0 );

        double sum = 0.0;
        for (unsigned i = 1; i < numberOfVariables(); i++)
            sum +=sqr(x( i )) - (10.0 * cos(4 * M_PI * x(i) ) );

        double g = 1.0 + (10.0 * (numberOfVariables() - 1.0)) + sum;
        double h = 1.0 - std::sqrt(x(0) / g);

        value[1] = g * h;

        return value;
    }

private:
    BoxConstraintHandler<SearchPointType> m_handler;
};

}
#endif