libcxx/include/__random/discrete_distribution.h

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef _LIBCPP___RANDOM_DISCRETE_DISTRIBUTION_H
  10 #define _LIBCPP___RANDOM_DISCRETE_DISTRIBUTION_H
  11
  12 #include <__algorithm/upper_bound.h>
  13 #include <__config>
  14 #include <__random/is_valid.h>
  15 #include <__random/uniform_real_distribution.h>
  16 #include <__vector/vector.h>
  17 #include <initializer_list>
  18 #include <iosfwd>
  19 #include <numeric>
  20
  21 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  22 #  pragma GCC system_header
  23 #endif
  24
  25 _LIBCPP_PUSH_MACROS
  26 #include <__undef_macros>
  27
  28 _LIBCPP_BEGIN_NAMESPACE_STD
  29
  30 template <class _IntType = int>
  31 class _LIBCPP_TEMPLATE_VIS discrete_distribution {
  32   static_assert(__libcpp_random_is_valid_inttype<_IntType>::value, "IntType must be a supported integer type");
  33
  34 public:
  35   // types
  36   typedef _IntType result_type;
  37
  38   class _LIBCPP_TEMPLATE_VIS param_type {
  39     vector<double> __p_;
  40
  41   public:
  42     typedef discrete_distribution distribution_type;
  43
  44     _LIBCPP_HIDE_FROM_ABI param_type() {}
  45     template <class _InputIterator>
  46     _LIBCPP_HIDE_FROM_ABI param_type(_InputIterator __f, _InputIterator __l) : __p_(__f, __l) {
  47       __init();
  48     }
  49 #ifndef _LIBCPP_CXX03_LANG
  50     _LIBCPP_HIDE_FROM_ABI param_type(initializer_list<double> __wl) : __p_(__wl.begin(), __wl.end()) { __init(); }
  51 #endif // _LIBCPP_CXX03_LANG
  52     template <class _UnaryOperation>
  53     _LIBCPP_HIDE_FROM_ABI param_type(size_t __nw, double __xmin, double __xmax, _UnaryOperation __fw);
  54
  55     _LIBCPP_HIDE_FROM_ABI vector<double> probabilities() const;
  56
  57     friend _LIBCPP_HIDE_FROM_ABI bool operator==(const param_type& __x, const param_type& __y) {
  58       return __x.__p_ == __y.__p_;
  59     }
  60     friend _LIBCPP_HIDE_FROM_ABI bool operator!=(const param_type& __x, const param_type& __y) { return !(__x == __y); }
  61
  62   private:
  63     _LIBCPP_HIDE_FROM_ABI void __init();
  64
  65     friend class discrete_distribution;
  66
  67     template <class _CharT, class _Traits, class _IT>
  68     friend basic_ostream<_CharT, _Traits>&
  69     operator<<(basic_ostream<_CharT, _Traits>& __os, const discrete_distribution<_IT>& __x);
  70
  71     template <class _CharT, class _Traits, class _IT>
  72     friend basic_istream<_CharT, _Traits>&
  73     operator>>(basic_istream<_CharT, _Traits>& __is, discrete_distribution<_IT>& __x);
  74   };
  75
  76 private:
  77   param_type __p_;
  78
  79 public:
  80   // constructor and reset functions
  81   _LIBCPP_HIDE_FROM_ABI discrete_distribution() {}
  82   template <class _InputIterator>
  83   _LIBCPP_HIDE_FROM_ABI discrete_distribution(_InputIterator __f, _InputIterator __l) : __p_(__f, __l) {}
  84 #ifndef _LIBCPP_CXX03_LANG
  85   _LIBCPP_HIDE_FROM_ABI discrete_distribution(initializer_list<double> __wl) : __p_(__wl) {}
  86 #endif // _LIBCPP_CXX03_LANG
  87   template <class _UnaryOperation>
  88   _LIBCPP_HIDE_FROM_ABI discrete_distribution(size_t __nw, double __xmin, double __xmax, _UnaryOperation __fw)
  89       : __p_(__nw, __xmin, __xmax, __fw) {}
  90   _LIBCPP_HIDE_FROM_ABI explicit discrete_distribution(const param_type& __p) : __p_(__p) {}
  91   _LIBCPP_HIDE_FROM_ABI void reset() {}
  92
  93   // generating functions
  94   template <class _URNG>
  95   _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g) {
  96     return (*this)(__g, __p_);
  97   }
  98   template <class _URNG>
  99   _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g, const param_type& __p);
 100
 101   // property functions
 102   _LIBCPP_HIDE_FROM_ABI vector<double> probabilities() const { return __p_.probabilities(); }
 103
 104   _LIBCPP_HIDE_FROM_ABI param_type param() const { return __p_; }
 105   _LIBCPP_HIDE_FROM_ABI void param(const param_type& __p) { __p_ = __p; }
 106
 107   _LIBCPP_HIDE_FROM_ABI result_type min() const { return 0; }
 108   _LIBCPP_HIDE_FROM_ABI result_type max() const { return __p_.__p_.size(); }
 109
 110   friend _LIBCPP_HIDE_FROM_ABI bool operator==(const discrete_distribution& __x, const discrete_distribution& __y) {
 111     return __x.__p_ == __y.__p_;
 112   }
 113   friend _LIBCPP_HIDE_FROM_ABI bool operator!=(const discrete_distribution& __x, const discrete_distribution& __y) {
 114     return !(__x == __y);
 115   }
 116
 117   template <class _CharT, class _Traits, class _IT>
 118   friend basic_ostream<_CharT, _Traits>&
 119   operator<<(basic_ostream<_CharT, _Traits>& __os, const discrete_distribution<_IT>& __x);
 120
 121   template <class _CharT, class _Traits, class _IT>
 122   friend basic_istream<_CharT, _Traits>&
 123   operator>>(basic_istream<_CharT, _Traits>& __is, discrete_distribution<_IT>& __x);
 124 };
 125
 126 template <class _IntType>
 127 template <class _UnaryOperation>
 128 discrete_distribution<_IntType>::param_type::param_type(
 129     size_t __nw, double __xmin, double __xmax, _UnaryOperation __fw) {
 130   if (__nw > 1) {
 131     __p_.reserve(__nw - 1);
 132     double __d  = (__xmax - __xmin) / __nw;
 133     double __d2 = __d / 2;
 134     for (size_t __k = 0; __k < __nw; ++__k)
 135       __p_.push_back(__fw(__xmin + __k * __d + __d2));
 136     __init();
 137   }
 138 }
 139
 140 template <class _IntType>
 141 void discrete_distribution<_IntType>::param_type::__init() {
 142   if (!__p_.empty()) {
 143     if (__p_.size() > 1) {
 144       double __s = std::accumulate(__p_.begin(), __p_.end(), 0.0);
 145       for (vector<double>::iterator __i = __p_.begin(), __e = __p_.end(); __i < __e; ++__i)
 146         *__i /= __s;
 147       vector<double> __t(__p_.size() - 1);
 148       std::partial_sum(__p_.begin(), __p_.end() - 1, __t.begin());
 149       swap(__p_, __t);
 150     } else {
 151       __p_.clear();
 152       __p_.shrink_to_fit();
 153     }
 154   }
 155 }
 156
 157 template <class _IntType>
 158 vector<double> discrete_distribution<_IntType>::param_type::probabilities() const {
 159   size_t __n = __p_.size();
 160   vector<double> __p(__n + 1);
 161   std::adjacent_difference(__p_.begin(), __p_.end(), __p.begin());
 162   if (__n > 0)
 163     __p[__n] = 1 - __p_[__n - 1];
 164   else
 165     __p[0] = 1;
 166   return __p;
 167 }
 168
 169 template <class _IntType>
 170 template <class _URNG>
 171 _IntType discrete_distribution<_IntType>::operator()(_URNG& __g, const param_type& __p) {
 172   static_assert(__libcpp_random_is_valid_urng<_URNG>::value, "");
 173   uniform_real_distribution<double> __gen;
 174   return static_cast<_IntType>(std::upper_bound(__p.__p_.begin(), __p.__p_.end(), __gen(__g)) - __p.__p_.begin());
 175 }
 176
 177 template <class _CharT, class _Traits, class _IT>
 178 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
 179 operator<<(basic_ostream<_CharT, _Traits>& __os, const discrete_distribution<_IT>& __x) {
 180   __save_flags<_CharT, _Traits> __lx(__os);
 181   typedef basic_ostream<_CharT, _Traits> _OStream;
 182   __os.flags(_OStream::dec | _OStream::left | _OStream::fixed | _OStream::scientific);
 183   _CharT __sp = __os.widen(' ');
 184   __os.fill(__sp);
 185   size_t __n = __x.__p_.__p_.size();
 186   __os << __n;
 187   for (size_t __i = 0; __i < __n; ++__i)
 188     __os << __sp << __x.__p_.__p_[__i];
 189   return __os;
 190 }
 191
 192 template <class _CharT, class _Traits, class _IT>
 193 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
 194 operator>>(basic_istream<_CharT, _Traits>& __is, discrete_distribution<_IT>& __x) {
 195   __save_flags<_CharT, _Traits> __lx(__is);
 196   typedef basic_istream<_CharT, _Traits> _Istream;
 197   __is.flags(_Istream::dec | _Istream::skipws);
 198   size_t __n;
 199   __is >> __n;
 200   vector<double> __p(__n);
 201   for (size_t __i = 0; __i < __n; ++__i)
 202     __is >> __p[__i];
 203   if (!__is.fail())
 204     swap(__x.__p_.__p_, __p);
 205   return __is;
 206 }
 207
 208 _LIBCPP_END_NAMESPACE_STD
 209
 210 _LIBCPP_POP_MACROS
 211
 212 #endif // _LIBCPP___RANDOM_DISCRETE_DISTRIBUTION_H