ZDT2.h
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1 //===========================================================================
2 /*!
3  *
4  *
5  * \brief Multi-objective optimization benchmark function ZDT2
6  *
7  * The function is described in
8  *
9  * Eckart Zitzler, Kalyanmoy Deb, and Lothar Thiele. Comparison of
10  * Multiobjective Evolutionary Algorithms: Empirical
11  * Results. Evolutionary Computation 8(2):173-195, 2000
12  *
13  *
14  *
15  * \author -
16  * \date -
17  *
18  *
19  * \par Copyright 1995-2017 Shark Development Team
20  *
21  * <BR><HR>
22  * This file is part of Shark.
23  * <http://shark-ml.org/>
24  *
25  * Shark is free software: you can redistribute it and/or modify
26  * it under the terms of the GNU Lesser General Public License as published
27  * by the Free Software Foundation, either version 3 of the License, or
28  * (at your option) any later version.
29  *
30  * Shark is distributed in the hope that it will be useful,
31  * but WITHOUT ANY WARRANTY; without even the implied warranty of
32  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
33  * GNU Lesser General Public License for more details.
34  *
35  * You should have received a copy of the GNU Lesser General Public License
36  * along with Shark. If not, see <http://www.gnu.org/licenses/>.
37  *
38  */
39 //===========================================================================
40 
41 #ifndef SHARK_OBJECTIVEFUNCTIONS_BENCHMARK_ZDT2_H
42 #define SHARK_OBJECTIVEFUNCTIONS_BENCHMARK_ZDT2_H
43 
44 #include <shark/ObjectiveFunctions/AbstractObjectiveFunction.h>
45 #include <shark/ObjectiveFunctions/BoxConstraintHandler.h>
46 
47 namespace shark {
48 /*! \brief Multi-objective optimization benchmark function ZDT2
49 *
50 * The function is described in
51 *
52 * Eckart Zitzler, Kalyanmoy Deb, and Lothar Thiele. Comparison of
53 * Multiobjective Evolutionary Algorithms: Empirical
54 * Results. Evolutionary Computation 8(2):173-195, 2000
55 */
56 struct ZDT2 : public MultiObjectiveFunction
57 {
58 
59  ZDT2(std::size_t numVariables = 0) : m_handler(numVariables,0,1) {
60  announceConstraintHandler(&m_handler);
61  }
62 
63  /// \brief From INameable: return the class name.
64  std::string name() const
65  { return "ZDT2"; }
66 
67  std::size_t numberOfObjectives()const{
68  return 2;
69  }
70 
71  std::size_t numberOfVariables()const{
72  return m_handler.dimensions();
73  }
74 
75  bool hasScalableDimensionality()const{
76  return true;
77  }
78 
79  /// \brief Adjusts the number of variables if the function is scalable.
80  /// \param [in] numberOfVariables The new dimension.
81  void setNumberOfVariables( std::size_t numberOfVariables ){
82  m_handler.setBounds(numberOfVariables,0,1);
83  }
84 
85  ResultType eval( const SearchPointType & x ) const {
86  m_evaluationCounter++;
87 
88  ResultType value( 2 );
89 
90  value[0] = x( 0 );
91 
92  double g = 1.0 + 9.0 *(sum(x)-x(0))/(numberOfVariables() - 1.0);
93  double h = 1.0 - sqr(x( 0 ) / g);
94 
95  value[1] = g * h;
96 
97  return( value );
98  }
99 
100 private:
101  BoxConstraintHandler<SearchPointType> m_handler;
102 };
103 
104 }
105 #endif