ElitistSelection.h
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1 /*!
2  *
3  *
4  * \brief Elitist Selection Operator suitable for (mu,lambda) and (mu+lambda) selection
5  *
6  *
7  * \author O.Krause
8  * \date 2014
9  *
10  *
11  * \par Copyright 1995-2017 Shark Development Team
12  *
13  * <BR><HR>
14  * This file is part of Shark.
15  * <http://shark-ml.org/>
16  *
17  * Shark is free software: you can redistribute it and/or modify
18  * it under the terms of the GNU Lesser General Public License as published
19  * by the Free Software Foundation, either version 3 of the License, or
20  * (at your option) any later version.
21  *
22  * Shark is distributed in the hope that it will be useful,
23  * but WITHOUT ANY WARRANTY; without even the implied warranty of
24  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
25  * GNU Lesser General Public License for more details.
26  *
27  * You should have received a copy of the GNU Lesser General Public License
28  * along with Shark. If not, see <http://www.gnu.org/licenses/>.
29  *
30  */
31 #ifndef SHARK_ALGORITHMS_DIRECTSEARCH_OPERATORS_SELECTION_ELITIST_SELECTION_H
32 #define SHARK_ALGORITHMS_DIRECTSEARCH_OPERATORS_SELECTION_ELITIST_SELECTION_H
33 
34 #include <shark/LinAlg/Base.h>
35 #include <vector>
36 #include <numeric>
37 namespace shark {
38 
39 /// \brief Survival selection to find the next parent set
40 ///
41 /// Given a set of individuals, selects the mu best performing individuals.
42 /// The elements are ordered using the given Ordering Relation
43 template< typename Ordering >
45 
46  /// \brief Selects individuals from the range of individuals.
47  ///
48  /// \param [in] it Iterator pointing to the first valid parent individual.
49  /// \param [in] itE Iterator pointing to the first invalid parent individual.
50  /// \param [in] out Iterator pointing to the first valid element of the output range.
51  /// \param [in] outE Iterator pointing to the first invalid element of the output range.
52  template<typename InIterator,typename OutIterator>
53  void operator()(
54  InIterator it, InIterator itE,
55  OutIterator out, OutIterator outE
56  ){
57  std::size_t outputSize = std::distance( out, outE );
58  std::vector<InIterator> results = order(it, itE);
59  SHARK_RUNTIME_CHECK(results.size() > outputSize, "Input range must be bigger than output range");
60 
61  for(std::size_t i = 0; i != outputSize; ++i, ++out){
62  *out = *results[i];
63  }
64  }
65 
66  /// \brief Selects individuals from the range of individuals.
67  ///
68  /// Instead of using an output range, surviving individuals are marked as selected.
69  ///
70  /// \param [in] population The population where individuals are selected from
71  /// \param [in] mu number of individuals to select
72  template<typename Population>
73  void operator()(
74  Population& population,std::size_t mu
75  ){
76  SHARK_RUNTIME_CHECK(population.size() >= mu, "Population Size must be at least mu");
77 
78  typedef typename Population::iterator InIterator;
79  std::vector<InIterator> results = order(population.begin(),population.end());
80 
81  for(std::size_t i = 0; i != mu; ++i){
82  results[i]->select()=true;
83  }
84  for(std::size_t i = mu; i != results.size(); ++i){
85  results[i]->select() = false;
86  }
87  }
88 private:
89  /// Returns a sorted range of pairs indicating, how often every individual won.
90  /// The best individuals are in the back of the range.
91  template<class InIterator>
92  std::vector<InIterator> order(InIterator it, InIterator itE){
93  std::size_t size = std::distance( it, itE );
94  std::vector<InIterator > individuals(size);
95  std::iota(individuals.begin(),individuals.end(),it);
96  std::sort(
97  individuals.begin(),
98  individuals.end(),
99  [](InIterator lhs, InIterator rhs){
100  Ordering ordering;
101  return ordering(*lhs,*rhs);
102  }
103  );
104  return individuals;
105  }
106 };
107 
108 }
109 
110 #endif