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 <__random/is_valid.h>
  15 #include <__random/uniform_real_distribution.h>
  16 #include <iosfwd>
  17 #include <numeric>
  18 #include <vector>
  19
  20 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  21 #  pragma GCC system_header
  22 #endif
  23
  24 _LIBCPP_PUSH_MACROS
  25 #include <__undef_macros>
  26
  27 _LIBCPP_BEGIN_NAMESPACE_STD
  28
  29 template<class _RealType = double>
  30 class _LIBCPP_TEMPLATE_VIS piecewise_constant_distribution
  31 {
  32 public:
  33     // types
  34     typedef _RealType result_type;
  35
  36     class _LIBCPP_TEMPLATE_VIS param_type
  37     {
  38         vector<result_type> __b_;
  39         vector<result_type> __densities_;
  40         vector<result_type> __areas_;
  41     public:
  42         typedef piecewise_constant_distribution distribution_type;
  43
  44         _LIBCPP_HIDE_FROM_ABI param_type();
  45         template<class _InputIteratorB, class _InputIteratorW>
  46         _LIBCPP_HIDE_FROM_ABI param_type(_InputIteratorB __f_b, _InputIteratorB __l_b,
  47                        _InputIteratorW __f_w);
  48 #ifndef _LIBCPP_CXX03_LANG
  49         template<class _UnaryOperation>
  50         _LIBCPP_HIDE_FROM_ABI param_type(initializer_list<result_type> __bl, _UnaryOperation __fw);
  51 #endif // _LIBCPP_CXX03_LANG
  52         template<class _UnaryOperation>
  53         _LIBCPP_HIDE_FROM_ABI param_type(size_t __nw, result_type __xmin, result_type __xmax,
  54                        _UnaryOperation __fw);
  55         _LIBCPP_HIDE_FROM_ABI param_type(param_type const&) = default;
  56         _LIBCPP_HIDE_FROM_ABI param_type & operator=(const param_type& __rhs);
  57
  58         _LIBCPP_INLINE_VISIBILITY
  59         vector<result_type> intervals() const {return __b_;}
  60         _LIBCPP_INLINE_VISIBILITY
  61         vector<result_type> densities() const {return __densities_;}
  62
  63         friend _LIBCPP_INLINE_VISIBILITY
  64             bool operator==(const param_type& __x, const param_type& __y)
  65             {return __x.__densities_ == __y.__densities_ && __x.__b_ == __y.__b_;}
  66         friend _LIBCPP_INLINE_VISIBILITY
  67             bool operator!=(const param_type& __x, const param_type& __y)
  68             {return !(__x == __y);}
  69
  70     private:
  71         _LIBCPP_HIDE_FROM_ABI void __init();
  72
  73         friend class piecewise_constant_distribution;
  74
  75         template <class _CharT, class _Traits, class _RT>
  76         friend
  77         basic_ostream<_CharT, _Traits>&
  78         operator<<(basic_ostream<_CharT, _Traits>& __os,
  79                    const piecewise_constant_distribution<_RT>& __x);
  80
  81         template <class _CharT, class _Traits, class _RT>
  82         friend
  83         basic_istream<_CharT, _Traits>&
  84         operator>>(basic_istream<_CharT, _Traits>& __is,
  85                    piecewise_constant_distribution<_RT>& __x);
  86     };
  87
  88 private:
  89     param_type __p_;
  90
  91 public:
  92     // constructor and reset functions
  93     _LIBCPP_INLINE_VISIBILITY
  94     piecewise_constant_distribution() {}
  95     template<class _InputIteratorB, class _InputIteratorW>
  96         _LIBCPP_INLINE_VISIBILITY
  97         piecewise_constant_distribution(_InputIteratorB __f_b,
  98                                         _InputIteratorB __l_b,
  99                                         _InputIteratorW __f_w)
 100         : __p_(__f_b, __l_b, __f_w) {}
 101
 102 #ifndef _LIBCPP_CXX03_LANG
 103     template<class _UnaryOperation>
 104         _LIBCPP_INLINE_VISIBILITY
 105         piecewise_constant_distribution(initializer_list<result_type> __bl,
 106                                         _UnaryOperation __fw)
 107         : __p_(__bl, __fw) {}
 108 #endif // _LIBCPP_CXX03_LANG
 109
 110     template<class _UnaryOperation>
 111         _LIBCPP_INLINE_VISIBILITY
 112         piecewise_constant_distribution(size_t __nw, result_type __xmin,
 113                                         result_type __xmax, _UnaryOperation __fw)
 114         : __p_(__nw, __xmin, __xmax, __fw) {}
 115
 116     _LIBCPP_INLINE_VISIBILITY
 117     explicit piecewise_constant_distribution(const param_type& __p)
 118         : __p_(__p) {}
 119
 120     _LIBCPP_INLINE_VISIBILITY
 121     void reset() {}
 122
 123     // generating functions
 124     template<class _URNG>
 125         _LIBCPP_INLINE_VISIBILITY
 126         result_type operator()(_URNG& __g)
 127         {return (*this)(__g, __p_);}
 128     template<class _URNG>
 129     _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g, const param_type& __p);
 130
 131     // property functions
 132     _LIBCPP_INLINE_VISIBILITY
 133     vector<result_type> intervals() const {return __p_.intervals();}
 134     _LIBCPP_INLINE_VISIBILITY
 135     vector<result_type> densities() const {return __p_.densities();}
 136
 137     _LIBCPP_INLINE_VISIBILITY
 138     param_type param() const {return __p_;}
 139     _LIBCPP_INLINE_VISIBILITY
 140     void param(const param_type& __p) {__p_ = __p;}
 141
 142     _LIBCPP_INLINE_VISIBILITY
 143     result_type min() const {return __p_.__b_.front();}
 144     _LIBCPP_INLINE_VISIBILITY
 145     result_type max() const {return __p_.__b_.back();}
 146
 147     friend _LIBCPP_INLINE_VISIBILITY
 148         bool operator==(const piecewise_constant_distribution& __x,
 149                         const piecewise_constant_distribution& __y)
 150         {return __x.__p_ == __y.__p_;}
 151     friend _LIBCPP_INLINE_VISIBILITY
 152         bool operator!=(const piecewise_constant_distribution& __x,
 153                            const piecewise_constant_distribution& __y)
 154         {return !(__x == __y);}
 155
 156     template <class _CharT, class _Traits, class _RT>
 157     friend
 158     basic_ostream<_CharT, _Traits>&
 159     operator<<(basic_ostream<_CharT, _Traits>& __os,
 160                const piecewise_constant_distribution<_RT>& __x);
 161
 162     template <class _CharT, class _Traits, class _RT>
 163     friend
 164     basic_istream<_CharT, _Traits>&
 165     operator>>(basic_istream<_CharT, _Traits>& __is,
 166                piecewise_constant_distribution<_RT>& __x);
 167 };
 168
 169 template<class _RealType>
 170 typename piecewise_constant_distribution<_RealType>::param_type &
 171 piecewise_constant_distribution<_RealType>::param_type::operator=
 172                                                        (const param_type& __rhs)
 173 {
 174 //  These can throw
 175     __b_.reserve        (__rhs.__b_.size ());
 176     __densities_.reserve(__rhs.__densities_.size());
 177     __areas_.reserve    (__rhs.__areas_.size());
 178
 179 //  These can not throw
 180     __b_         = __rhs.__b_;
 181     __densities_ = __rhs.__densities_;
 182     __areas_     =  __rhs.__areas_;
 183     return *this;
 184 }
 185
 186 template<class _RealType>
 187 void
 188 piecewise_constant_distribution<_RealType>::param_type::__init()
 189 {
 190     // __densities_ contains non-normalized areas
 191     result_type __total_area = _VSTD::accumulate(__densities_.begin(),
 192                                                 __densities_.end(),
 193                                                 result_type());
 194     for (size_t __i = 0; __i < __densities_.size(); ++__i)
 195         __densities_[__i] /= __total_area;
 196     // __densities_ contains normalized areas
 197     __areas_.assign(__densities_.size(), result_type());
 198     _VSTD::partial_sum(__densities_.begin(), __densities_.end() - 1,
 199                                                           __areas_.begin() + 1);
 200     // __areas_ contains partial sums of normalized areas: [0, __densities_ - 1]
 201     __densities_.back() = 1 - __areas_.back();  // correct round off error
 202     for (size_t __i = 0; __i < __densities_.size(); ++__i)
 203         __densities_[__i] /= (__b_[__i+1] - __b_[__i]);
 204     // __densities_ now contains __densities_
 205 }
 206
 207 template<class _RealType>
 208 piecewise_constant_distribution<_RealType>::param_type::param_type()
 209     : __b_(2),
 210       __densities_(1, 1.0),
 211       __areas_(1, 0.0)
 212 {
 213     __b_[1] = 1;
 214 }
 215
 216 template<class _RealType>
 217 template<class _InputIteratorB, class _InputIteratorW>
 218 piecewise_constant_distribution<_RealType>::param_type::param_type(
 219         _InputIteratorB __f_b, _InputIteratorB __l_b, _InputIteratorW __f_w)
 220     : __b_(__f_b, __l_b)
 221 {
 222     if (__b_.size() < 2)
 223     {
 224         __b_.resize(2);
 225         __b_[0] = 0;
 226         __b_[1] = 1;
 227         __densities_.assign(1, 1.0);
 228         __areas_.assign(1, 0.0);
 229     }
 230     else
 231     {
 232         __densities_.reserve(__b_.size() - 1);
 233         for (size_t __i = 0; __i < __b_.size() - 1; ++__i, ++__f_w)
 234             __densities_.push_back(*__f_w);
 235         __init();
 236     }
 237 }
 238
 239 #ifndef _LIBCPP_CXX03_LANG
 240
 241 template<class _RealType>
 242 template<class _UnaryOperation>
 243 piecewise_constant_distribution<_RealType>::param_type::param_type(
 244         initializer_list<result_type> __bl, _UnaryOperation __fw)
 245     : __b_(__bl.begin(), __bl.end())
 246 {
 247     if (__b_.size() < 2)
 248     {
 249         __b_.resize(2);
 250         __b_[0] = 0;
 251         __b_[1] = 1;
 252         __densities_.assign(1, 1.0);
 253         __areas_.assign(1, 0.0);
 254     }
 255     else
 256     {
 257         __densities_.reserve(__b_.size() - 1);
 258         for (size_t __i = 0; __i < __b_.size() - 1; ++__i)
 259             __densities_.push_back(__fw((__b_[__i+1] + __b_[__i])*.5));
 260         __init();
 261     }
 262 }
 263
 264 #endif // _LIBCPP_CXX03_LANG
 265
 266 template<class _RealType>
 267 template<class _UnaryOperation>
 268 piecewise_constant_distribution<_RealType>::param_type::param_type(
 269         size_t __nw, result_type __xmin, result_type __xmax, _UnaryOperation __fw)
 270     : __b_(__nw == 0 ? 2 : __nw + 1)
 271 {
 272     size_t __n = __b_.size() - 1;
 273     result_type __d = (__xmax - __xmin) / __n;
 274     __densities_.reserve(__n);
 275     for (size_t __i = 0; __i < __n; ++__i)
 276     {
 277         __b_[__i] = __xmin + __i * __d;
 278         __densities_.push_back(__fw(__b_[__i] + __d*.5));
 279     }
 280     __b_[__n] = __xmax;
 281     __init();
 282 }
 283
 284 template<class _RealType>
 285 template<class _URNG>
 286 _RealType
 287 piecewise_constant_distribution<_RealType>::operator()(_URNG& __g, const param_type& __p)
 288 {
 289     static_assert(__libcpp_random_is_valid_urng<_URNG>::value, "");
 290     typedef uniform_real_distribution<result_type> _Gen;
 291     result_type __u = _Gen()(__g);
 292     ptrdiff_t __k = _VSTD::upper_bound(__p.__areas_.begin(), __p.__areas_.end(),
 293                                       __u) - __p.__areas_.begin() - 1;
 294     return (__u - __p.__areas_[__k]) / __p.__densities_[__k] + __p.__b_[__k];
 295 }
 296
 297 template <class _CharT, class _Traits, class _RT>
 298 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
 299 operator<<(basic_ostream<_CharT, _Traits>& __os,
 300            const piecewise_constant_distribution<_RT>& __x)
 301 {
 302     __save_flags<_CharT, _Traits> __lx(__os);
 303     typedef basic_ostream<_CharT, _Traits> _OStream;
 304     __os.flags(_OStream::dec | _OStream::left | _OStream::fixed |
 305                _OStream::scientific);
 306     _CharT __sp = __os.widen(' ');
 307     __os.fill(__sp);
 308     size_t __n = __x.__p_.__b_.size();
 309     __os << __n;
 310     for (size_t __i = 0; __i < __n; ++__i)
 311         __os << __sp << __x.__p_.__b_[__i];
 312     __n = __x.__p_.__densities_.size();
 313     __os << __sp << __n;
 314     for (size_t __i = 0; __i < __n; ++__i)
 315         __os << __sp << __x.__p_.__densities_[__i];
 316     __n = __x.__p_.__areas_.size();
 317     __os << __sp << __n;
 318     for (size_t __i = 0; __i < __n; ++__i)
 319         __os << __sp << __x.__p_.__areas_[__i];
 320     return __os;
 321 }
 322
 323 template <class _CharT, class _Traits, class _RT>
 324 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
 325 operator>>(basic_istream<_CharT, _Traits>& __is,
 326            piecewise_constant_distribution<_RT>& __x)
 327 {
 328     typedef piecewise_constant_distribution<_RT> _Eng;
 329     typedef typename _Eng::result_type result_type;
 330     __save_flags<_CharT, _Traits> __lx(__is);
 331     typedef basic_istream<_CharT, _Traits> _Istream;
 332     __is.flags(_Istream::dec | _Istream::skipws);
 333     size_t __n;
 334     __is >> __n;
 335     vector<result_type> __b(__n);
 336     for (size_t __i = 0; __i < __n; ++__i)
 337         __is >> __b[__i];
 338     __is >> __n;
 339     vector<result_type> __densities(__n);
 340     for (size_t __i = 0; __i < __n; ++__i)
 341         __is >> __densities[__i];
 342     __is >> __n;
 343     vector<result_type> __areas(__n);
 344     for (size_t __i = 0; __i < __n; ++__i)
 345         __is >> __areas[__i];
 346     if (!__is.fail())
 347     {
 348         swap(__x.__p_.__b_, __b);
 349         swap(__x.__p_.__densities_, __densities);
 350         swap(__x.__p_.__areas_, __areas);
 351     }
 352     return __is;
 353 }
 354
 355 _LIBCPP_END_NAMESPACE_STD
 356
 357 _LIBCPP_POP_MACROS
 358
 359 #endif // _LIBCPP___RANDOM_PIECEWISE_CONSTANT_DISTRIBUTION_H