libstdc++
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00001 // <experimental/algorithm> -*- C++ -*- 00002 00003 // Copyright (C) 2014-2015 Free Software Foundation, Inc. 00004 // 00005 // This file is part of the GNU ISO C++ Library. This library is free 00006 // software; you can redistribute it and/or modify it under the 00007 // terms of the GNU General Public License as published by the 00008 // Free Software Foundation; either version 3, or (at your option) 00009 // any later version. 00010 00011 // This library is distributed in the hope that it will be useful, 00012 // but WITHOUT ANY WARRANTY; without even the implied warranty of 00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 00014 // GNU General Public License for more details. 00015 00016 // Under Section 7 of GPL version 3, you are granted additional 00017 // permissions described in the GCC Runtime Library Exception, version 00018 // 3.1, as published by the Free Software Foundation. 00019 00020 // You should have received a copy of the GNU General Public License and 00021 // a copy of the GCC Runtime Library Exception along with this program; 00022 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 00023 // <http://www.gnu.org/licenses/>. 00024 00025 /** @file experimental/algorithm 00026 * This is a TS C++ Library header. 00027 */ 00028 00029 #ifndef _GLIBCXX_EXPERIMENTAL_ALGORITHM 00030 #define _GLIBCXX_EXPERIMENTAL_ALGORITHM 1 00031 00032 #pragma GCC system_header 00033 00034 #if __cplusplus <= 201103L 00035 # include <bits/c++14_warning.h> 00036 #else 00037 00038 #include <algorithm> 00039 #include <random> 00040 00041 namespace std _GLIBCXX_VISIBILITY(default) 00042 { 00043 namespace experimental 00044 { 00045 inline namespace fundamentals_v1 00046 { 00047 _GLIBCXX_BEGIN_NAMESPACE_VERSION 00048 00049 template<typename _ForwardIterator, typename _Searcher> 00050 inline _ForwardIterator 00051 search(_ForwardIterator __first, _ForwardIterator __last, 00052 const _Searcher& __searcher) 00053 { return __searcher(__first, __last); } 00054 00055 #define __cpp_lib_experimental_sample 201402 00056 00057 /// Reservoir sampling algorithm. 00058 template<typename _InputIterator, typename _RandomAccessIterator, 00059 typename _Size, typename _UniformRandomNumberGenerator> 00060 _RandomAccessIterator 00061 __sample(_InputIterator __first, _InputIterator __last, input_iterator_tag, 00062 _RandomAccessIterator __out, random_access_iterator_tag, 00063 _Size __n, _UniformRandomNumberGenerator&& __g) 00064 { 00065 using __distrib_type = std::uniform_int_distribution<_Size>; 00066 using __param_type = typename __distrib_type::param_type; 00067 __distrib_type __d{}; 00068 _Size __sample_sz = 0; 00069 while (__first != __last && __sample_sz != __n) 00070 __out[__sample_sz++] = *__first++; 00071 for (auto __pop_sz = __sample_sz; __first != __last; 00072 ++__first, ++__pop_sz) 00073 { 00074 const auto __k = __d(__g, __param_type{0, __pop_sz}); 00075 if (__k < __n) 00076 __out[__k] = *__first; 00077 } 00078 return __out + __sample_sz; 00079 } 00080 00081 /// Selection sampling algorithm. 00082 template<typename _ForwardIterator, typename _OutputIterator, typename _Cat, 00083 typename _Size, typename _UniformRandomNumberGenerator> 00084 _OutputIterator 00085 __sample(_ForwardIterator __first, _ForwardIterator __last, 00086 forward_iterator_tag, 00087 _OutputIterator __out, _Cat, 00088 _Size __n, _UniformRandomNumberGenerator&& __g) 00089 { 00090 using __distrib_type = std::uniform_int_distribution<_Size>; 00091 using __param_type = typename __distrib_type::param_type; 00092 __distrib_type __d{}; 00093 _Size __unsampled_sz = std::distance(__first, __last); 00094 for (__n = std::min(__n, __unsampled_sz); __n != 0; ++__first) 00095 if (__d(__g, __param_type{0, --__unsampled_sz}) < __n) 00096 { 00097 *__out++ = *__first; 00098 --__n; 00099 } 00100 return __out; 00101 } 00102 00103 /// Take a random sample from a population. 00104 template<typename _PopulationIterator, typename _SampleIterator, 00105 typename _Distance, typename _UniformRandomNumberGenerator> 00106 _SampleIterator 00107 sample(_PopulationIterator __first, _PopulationIterator __last, 00108 _SampleIterator __out, _Distance __n, 00109 _UniformRandomNumberGenerator&& __g) 00110 { 00111 using __pop_cat = typename 00112 std::iterator_traits<_PopulationIterator>::iterator_category; 00113 using __samp_cat = typename 00114 std::iterator_traits<_SampleIterator>::iterator_category; 00115 00116 static_assert( 00117 __or_<is_convertible<__pop_cat, forward_iterator_tag>, 00118 is_convertible<__samp_cat, random_access_iterator_tag>>::value, 00119 "output range must use a RandomAccessIterator when input range" 00120 " does not meet the ForwardIterator requirements"); 00121 00122 static_assert(is_integral<_Distance>::value, 00123 "sample size must be an integer type"); 00124 00125 return std::experimental::__sample( 00126 __first, __last, __pop_cat{}, __out, __samp_cat{}, 00127 __n, std::forward<_UniformRandomNumberGenerator>(__g)); 00128 } 00129 00130 _GLIBCXX_END_NAMESPACE_VERSION 00131 } // namespace fundamentals_v1 00132 } // namespace experimental 00133 } // namespace std 00134 00135 #endif // C++14 00136 00137 #endif // _GLIBCXX_EXPERIMENTAL_ALGORITHM