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