libcxx/include/__random/piecewise_constant_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_PIECEWISE_CONSTANT_DISTRIBUTION_H
  10 #define _LIBCPP___RANDOM_PIECEWISE_CONSTANT_DISTRIBUTION_H
  11
  12 #include <__algorithm/upper_bound.h>
  13 #include <__config>
  14 #include <__cstddef/ptrdiff_t.h>
  15 #include <__random/is_valid.h>
  16 #include <__random/uniform_real_distribution.h>
  17 #include <__vector/vector.h>
  18 #include <initializer_list>
  19 #include <iosfwd>
  20 #include <numeric>
  21
  22 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  23 #  pragma GCC system_header
  24 #endif
  25
  26 _LIBCPP_PUSH_MACROS
  27 #include <__undef_macros>
  28
  29 _LIBCPP_BEGIN_NAMESPACE_STD
  30
  31 template <class _RealType = double>
  32 class _LIBCPP_TEMPLATE_VIS piecewise_constant_distribution {
  33   static_assert(__libcpp_random_is_valid_realtype<_RealType>::value,
  34                 "RealType must be a supported floating-point type");
  35
  36 public:
  37   // types
  38   typedef _RealType result_type;
  39
  40   class _LIBCPP_TEMPLATE_VIS param_type {
  41     vector<result_type> __b_;
  42     vector<result_type> __densities_;
  43     vector<result_type> __areas_;
  44
  45   public:
  46     typedef piecewise_constant_distribution distribution_type;
  47
  48     _LIBCPP_HIDE_FROM_ABI param_type();
  49     template <class _InputIteratorB, class _InputIteratorW>
  50     _LIBCPP_HIDE_FROM_ABI param_type(_InputIteratorB __f_b, _InputIteratorB __l_b, _InputIteratorW __f_w);
  51 #ifndef _LIBCPP_CXX03_LANG
  52     template <class _UnaryOperation>
  53     _LIBCPP_HIDE_FROM_ABI param_type(initializer_list<result_type> __bl, _UnaryOperation __fw);
  54 #endif // _LIBCPP_CXX03_LANG
  55     template <class _UnaryOperation>
  56     _LIBCPP_HIDE_FROM_ABI param_type(size_t __nw, result_type __xmin, result_type __xmax, _UnaryOperation __fw);
  57     _LIBCPP_HIDE_FROM_ABI param_type(param_type const&) = default;
  58     _LIBCPP_HIDE_FROM_ABI param_type& operator=(const param_type& __rhs);
  59
  60     _LIBCPP_HIDE_FROM_ABI vector<result_type> intervals() const { return __b_; }
  61     _LIBCPP_HIDE_FROM_ABI vector<result_type> densities() const { return __densities_; }
  62
  63     friend _LIBCPP_HIDE_FROM_ABI bool operator==(const param_type& __x, const param_type& __y) {
  64       return __x.__densities_ == __y.__densities_ && __x.__b_ == __y.__b_;
  65     }
  66     friend _LIBCPP_HIDE_FROM_ABI bool operator!=(const param_type& __x, const param_type& __y) { return !(__x == __y); }
  67
  68   private:
  69     _LIBCPP_HIDE_FROM_ABI void __init();
  70
  71     friend class piecewise_constant_distribution;
  72
  73     template <class _CharT, class _Traits, class _RT>
  74     friend basic_ostream<_CharT, _Traits>&
  75     operator<<(basic_ostream<_CharT, _Traits>& __os, const piecewise_constant_distribution<_RT>& __x);
  76
  77     template <class _CharT, class _Traits, class _RT>
  78     friend basic_istream<_CharT, _Traits>&
  79     operator>>(basic_istream<_CharT, _Traits>& __is, piecewise_constant_distribution<_RT>& __x);
  80   };
  81
  82 private:
  83   param_type __p_;
  84
  85 public:
  86   // constructor and reset functions
  87   _LIBCPP_HIDE_FROM_ABI piecewise_constant_distribution() {}
  88   template <class _InputIteratorB, class _InputIteratorW>
  89   _LIBCPP_HIDE_FROM_ABI
  90   piecewise_constant_distribution(_InputIteratorB __f_b, _InputIteratorB __l_b, _InputIteratorW __f_w)
  91       : __p_(__f_b, __l_b, __f_w) {}
  92
  93 #ifndef _LIBCPP_CXX03_LANG
  94   template <class _UnaryOperation>
  95   _LIBCPP_HIDE_FROM_ABI piecewise_constant_distribution(initializer_list<result_type> __bl, _UnaryOperation __fw)
  96       : __p_(__bl, __fw) {}
  97 #endif // _LIBCPP_CXX03_LANG
  98
  99   template <class _UnaryOperation>
 100   _LIBCPP_HIDE_FROM_ABI
 101   piecewise_constant_distribution(size_t __nw, result_type __xmin, result_type __xmax, _UnaryOperation __fw)
 102       : __p_(__nw, __xmin, __xmax, __fw) {}
 103
 104   _LIBCPP_HIDE_FROM_ABI explicit piecewise_constant_distribution(const param_type& __p) : __p_(__p) {}
 105
 106   _LIBCPP_HIDE_FROM_ABI void reset() {}
 107
 108   // generating functions
 109   template <class _URNG>
 110   _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g) {
 111     return (*this)(__g, __p_);
 112   }
 113   template <class _URNG>
 114   _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g, const param_type& __p);
 115
 116   // property functions
 117   _LIBCPP_HIDE_FROM_ABI vector<result_type> intervals() const { return __p_.intervals(); }
 118   _LIBCPP_HIDE_FROM_ABI vector<result_type> densities() const { return __p_.densities(); }
 119
 120   _LIBCPP_HIDE_FROM_ABI param_type param() const { return __p_; }
 121   _LIBCPP_HIDE_FROM_ABI void param(const param_type& __p) { __p_ = __p; }
 122
 123   _LIBCPP_HIDE_FROM_ABI result_type min() const { return __p_.__b_.front(); }
 124   _LIBCPP_HIDE_FROM_ABI result_type max() const { return __p_.__b_.back(); }
 125
 126   friend _LIBCPP_HIDE_FROM_ABI bool
 127   operator==(const piecewise_constant_distribution& __x, const piecewise_constant_distribution& __y) {
 128     return __x.__p_ == __y.__p_;
 129   }
 130   friend _LIBCPP_HIDE_FROM_ABI bool
 131   operator!=(const piecewise_constant_distribution& __x, const piecewise_constant_distribution& __y) {
 132     return !(__x == __y);
 133   }
 134
 135   template <class _CharT, class _Traits, class _RT>
 136   friend basic_ostream<_CharT, _Traits>&
 137   operator<<(basic_ostream<_CharT, _Traits>& __os, const piecewise_constant_distribution<_RT>& __x);
 138
 139   template <class _CharT, class _Traits, class _RT>
 140   friend basic_istream<_CharT, _Traits>&
 141   operator>>(basic_istream<_CharT, _Traits>& __is, piecewise_constant_distribution<_RT>& __x);
 142 };
 143
 144 template <class _RealType>
 145 typename piecewise_constant_distribution<_RealType>::param_type&
 146 piecewise_constant_distribution<_RealType>::param_type::operator=(const param_type& __rhs) {
 147   //  These can throw
 148   __b_.reserve(__rhs.__b_.size());
 149   __densities_.reserve(__rhs.__densities_.size());
 150   __areas_.reserve(__rhs.__areas_.size());
 151
 152   //  These can not throw
 153   __b_         = __rhs.__b_;
 154   __densities_ = __rhs.__densities_;
 155   __areas_     = __rhs.__areas_;
 156   return *this;
 157 }
 158
 159 template <class _RealType>
 160 void piecewise_constant_distribution<_RealType>::param_type::__init() {
 161   // __densities_ contains non-normalized areas
 162   result_type __total_area = std::accumulate(__densities_.begin(), __densities_.end(), result_type());
 163   for (size_t __i = 0; __i < __densities_.size(); ++__i)
 164     __densities_[__i] /= __total_area;
 165   // __densities_ contains normalized areas
 166   __areas_.assign(__densities_.size(), result_type());
 167   std::partial_sum(__densities_.begin(), __densities_.end() - 1, __areas_.begin() + 1);
 168   // __areas_ contains partial sums of normalized areas: [0, __densities_ - 1]
 169   __densities_.back() = 1 - __areas_.back(); // correct round off error
 170   for (size_t __i = 0; __i < __densities_.size(); ++__i)
 171     __densities_[__i] /= (__b_[__i + 1] - __b_[__i]);
 172   // __densities_ now contains __densities_
 173 }
 174
 175 template <class _RealType>
 176 piecewise_constant_distribution<_RealType>::param_type::param_type() : __b_(2), __densities_(1, 1.0), __areas_(1, 0.0) {
 177   __b_[1] = 1;
 178 }
 179
 180 template <class _RealType>
 181 template <class _InputIteratorB, class _InputIteratorW>
 182 piecewise_constant_distribution<_RealType>::param_type::param_type(
 183     _InputIteratorB __f_b, _InputIteratorB __l_b, _InputIteratorW __f_w)
 184     : __b_(__f_b, __l_b) {
 185   if (__b_.size() < 2) {
 186     __b_.resize(2);
 187     __b_[0] = 0;
 188     __b_[1] = 1;
 189     __densities_.assign(1, 1.0);
 190     __areas_.assign(1, 0.0);
 191   } else {
 192     __densities_.reserve(__b_.size() - 1);
 193     for (size_t __i = 0; __i < __b_.size() - 1; ++__i, ++__f_w)
 194       __densities_.push_back(*__f_w);
 195     __init();
 196   }
 197 }
 198
 199 #ifndef _LIBCPP_CXX03_LANG
 200
 201 template <class _RealType>
 202 template <class _UnaryOperation>
 203 piecewise_constant_distribution<_RealType>::param_type::param_type(
 204     initializer_list<result_type> __bl, _UnaryOperation __fw)
 205     : __b_(__bl.begin(), __bl.end()) {
 206   if (__b_.size() < 2) {
 207     __b_.resize(2);
 208     __b_[0] = 0;
 209     __b_[1] = 1;
 210     __densities_.assign(1, 1.0);
 211     __areas_.assign(1, 0.0);
 212   } else {
 213     __densities_.reserve(__b_.size() - 1);
 214     for (size_t __i = 0; __i < __b_.size() - 1; ++__i)
 215       __densities_.push_back(__fw((__b_[__i + 1] + __b_[__i]) * .5));
 216     __init();
 217   }
 218 }
 219
 220 #endif // _LIBCPP_CXX03_LANG
 221
 222 template <class _RealType>
 223 template <class _UnaryOperation>
 224 piecewise_constant_distribution<_RealType>::param_type::param_type(
 225     size_t __nw, result_type __xmin, result_type __xmax, _UnaryOperation __fw)
 226     : __b_(__nw == 0 ? 2 : __nw + 1) {
 227   size_t __n      = __b_.size() - 1;
 228   result_type __d = (__xmax - __xmin) / __n;
 229   __densities_.reserve(__n);
 230   for (size_t __i = 0; __i < __n; ++__i) {
 231     __b_[__i] = __xmin + __i * __d;
 232     __densities_.push_back(__fw(__b_[__i] + __d * .5));
 233   }
 234   __b_[__n] = __xmax;
 235   __init();
 236 }
 237
 238 template <class _RealType>
 239 template <class _URNG>
 240 _RealType piecewise_constant_distribution<_RealType>::operator()(_URNG& __g, const param_type& __p) {
 241   static_assert(__libcpp_random_is_valid_urng<_URNG>::value, "");
 242   typedef uniform_real_distribution<result_type> _Gen;
 243   result_type __u = _Gen()(__g);
 244   ptrdiff_t __k   = std::upper_bound(__p.__areas_.begin(), __p.__areas_.end(), __u) - __p.__areas_.begin() - 1;
 245   return (__u - __p.__areas_[__k]) / __p.__densities_[__k] + __p.__b_[__k];
 246 }
 247
 248 template <class _CharT, class _Traits, class _RT>
 249 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
 250 operator<<(basic_ostream<_CharT, _Traits>& __os, const piecewise_constant_distribution<_RT>& __x) {
 251   __save_flags<_CharT, _Traits> __lx(__os);
 252   typedef basic_ostream<_CharT, _Traits> _OStream;
 253   __os.flags(_OStream::dec | _OStream::left | _OStream::fixed | _OStream::scientific);
 254   _CharT __sp = __os.widen(' ');
 255   __os.fill(__sp);
 256   size_t __n = __x.__p_.__b_.size();
 257   __os << __n;
 258   for (size_t __i = 0; __i < __n; ++__i)
 259     __os << __sp << __x.__p_.__b_[__i];
 260   __n = __x.__p_.__densities_.size();
 261   __os << __sp << __n;
 262   for (size_t __i = 0; __i < __n; ++__i)
 263     __os << __sp << __x.__p_.__densities_[__i];
 264   __n = __x.__p_.__areas_.size();
 265   __os << __sp << __n;
 266   for (size_t __i = 0; __i < __n; ++__i)
 267     __os << __sp << __x.__p_.__areas_[__i];
 268   return __os;
 269 }
 270
 271 template <class _CharT, class _Traits, class _RT>
 272 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
 273 operator>>(basic_istream<_CharT, _Traits>& __is, piecewise_constant_distribution<_RT>& __x) {
 274   typedef piecewise_constant_distribution<_RT> _Eng;
 275   typedef typename _Eng::result_type result_type;
 276   __save_flags<_CharT, _Traits> __lx(__is);
 277   typedef basic_istream<_CharT, _Traits> _Istream;
 278   __is.flags(_Istream::dec | _Istream::skipws);
 279   size_t __n;
 280   __is >> __n;
 281   vector<result_type> __b(__n);
 282   for (size_t __i = 0; __i < __n; ++__i)
 283     __is >> __b[__i];
 284   __is >> __n;
 285   vector<result_type> __densities(__n);
 286   for (size_t __i = 0; __i < __n; ++__i)
 287     __is >> __densities[__i];
 288   __is >> __n;
 289   vector<result_type> __areas(__n);
 290   for (size_t __i = 0; __i < __n; ++__i)
 291     __is >> __areas[__i];
 292   if (!__is.fail()) {
 293     swap(__x.__p_.__b_, __b);
 294     swap(__x.__p_.__densities_, __densities);
 295     swap(__x.__p_.__areas_, __areas);
 296   }
 297   return __is;
 298 }
 299
 300 _LIBCPP_END_NAMESPACE_STD
 301
 302 _LIBCPP_POP_MACROS
 303
 304 #endif // _LIBCPP___RANDOM_PIECEWISE_CONSTANT_DISTRIBUTION_H