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         param_type();
45         template<class _InputIteratorB, class _InputIteratorW>
46             param_type(_InputIteratorB __f_b, _InputIteratorB __l_b,
47                        _InputIteratorW __f_w);
48 #ifndef _LIBCPP_CXX03_LANG
49         template<class _UnaryOperation>
50             param_type(initializer_list<result_type> __bl, _UnaryOperation __fw);
51 #endif // _LIBCPP_CXX03_LANG
52         template<class _UnaryOperation>
53             param_type(size_t __nw, result_type __xmin, result_type __xmax,
54                        _UnaryOperation __fw);
55         param_type(param_type const&) = default;
56         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         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> result_type operator()(_URNG& __g, const param_type& __p);
129 
130     // property functions
131     _LIBCPP_INLINE_VISIBILITY
132     vector<result_type> intervals() const {return __p_.intervals();}
133     _LIBCPP_INLINE_VISIBILITY
134     vector<result_type> densities() const {return __p_.densities();}
135 
136     _LIBCPP_INLINE_VISIBILITY
137     param_type param() const {return __p_;}
138     _LIBCPP_INLINE_VISIBILITY
139     void param(const param_type& __p) {__p_ = __p;}
140 
141     _LIBCPP_INLINE_VISIBILITY
142     result_type min() const {return __p_.__b_.front();}
143     _LIBCPP_INLINE_VISIBILITY
144     result_type max() const {return __p_.__b_.back();}
145 
146     friend _LIBCPP_INLINE_VISIBILITY
147         bool operator==(const piecewise_constant_distribution& __x,
148                         const piecewise_constant_distribution& __y)
149         {return __x.__p_ == __y.__p_;}
150     friend _LIBCPP_INLINE_VISIBILITY
151         bool operator!=(const piecewise_constant_distribution& __x,
152                            const piecewise_constant_distribution& __y)
153         {return !(__x == __y);}
154 
155     template <class _CharT, class _Traits, class _RT>
156     friend
157     basic_ostream<_CharT, _Traits>&
158     operator<<(basic_ostream<_CharT, _Traits>& __os,
159                const piecewise_constant_distribution<_RT>& __x);
160 
161     template <class _CharT, class _Traits, class _RT>
162     friend
163     basic_istream<_CharT, _Traits>&
164     operator>>(basic_istream<_CharT, _Traits>& __is,
165                piecewise_constant_distribution<_RT>& __x);
166 };
167 
168 template<class _RealType>
169 typename piecewise_constant_distribution<_RealType>::param_type &
170 piecewise_constant_distribution<_RealType>::param_type::operator=
171                                                        (const param_type& __rhs)
172 {
173 //  These can throw
174     __b_.reserve        (__rhs.__b_.size ());
175     __densities_.reserve(__rhs.__densities_.size());
176     __areas_.reserve    (__rhs.__areas_.size());
177 
178 //  These can not throw
179     __b_         = __rhs.__b_;
180     __densities_ = __rhs.__densities_;
181     __areas_     =  __rhs.__areas_;
182     return *this;
183 }
184 
185 template<class _RealType>
186 void
187 piecewise_constant_distribution<_RealType>::param_type::__init()
188 {
189     // __densities_ contains non-normalized areas
190     result_type __total_area = _VSTD::accumulate(__densities_.begin(),
191                                                 __densities_.end(),
192                                                 result_type());
193     for (size_t __i = 0; __i < __densities_.size(); ++__i)
194         __densities_[__i] /= __total_area;
195     // __densities_ contains normalized areas
196     __areas_.assign(__densities_.size(), result_type());
197     _VSTD::partial_sum(__densities_.begin(), __densities_.end() - 1,
198                                                           __areas_.begin() + 1);
199     // __areas_ contains partial sums of normalized areas: [0, __densities_ - 1]
200     __densities_.back() = 1 - __areas_.back();  // correct round off error
201     for (size_t __i = 0; __i < __densities_.size(); ++__i)
202         __densities_[__i] /= (__b_[__i+1] - __b_[__i]);
203     // __densities_ now contains __densities_
204 }
205 
206 template<class _RealType>
207 piecewise_constant_distribution<_RealType>::param_type::param_type()
208     : __b_(2),
209       __densities_(1, 1.0),
210       __areas_(1, 0.0)
211 {
212     __b_[1] = 1;
213 }
214 
215 template<class _RealType>
216 template<class _InputIteratorB, class _InputIteratorW>
217 piecewise_constant_distribution<_RealType>::param_type::param_type(
218         _InputIteratorB __f_b, _InputIteratorB __l_b, _InputIteratorW __f_w)
219     : __b_(__f_b, __l_b)
220 {
221     if (__b_.size() < 2)
222     {
223         __b_.resize(2);
224         __b_[0] = 0;
225         __b_[1] = 1;
226         __densities_.assign(1, 1.0);
227         __areas_.assign(1, 0.0);
228     }
229     else
230     {
231         __densities_.reserve(__b_.size() - 1);
232         for (size_t __i = 0; __i < __b_.size() - 1; ++__i, ++__f_w)
233             __densities_.push_back(*__f_w);
234         __init();
235     }
236 }
237 
238 #ifndef _LIBCPP_CXX03_LANG
239 
240 template<class _RealType>
241 template<class _UnaryOperation>
242 piecewise_constant_distribution<_RealType>::param_type::param_type(
243         initializer_list<result_type> __bl, _UnaryOperation __fw)
244     : __b_(__bl.begin(), __bl.end())
245 {
246     if (__b_.size() < 2)
247     {
248         __b_.resize(2);
249         __b_[0] = 0;
250         __b_[1] = 1;
251         __densities_.assign(1, 1.0);
252         __areas_.assign(1, 0.0);
253     }
254     else
255     {
256         __densities_.reserve(__b_.size() - 1);
257         for (size_t __i = 0; __i < __b_.size() - 1; ++__i)
258             __densities_.push_back(__fw((__b_[__i+1] + __b_[__i])*.5));
259         __init();
260     }
261 }
262 
263 #endif // _LIBCPP_CXX03_LANG
264 
265 template<class _RealType>
266 template<class _UnaryOperation>
267 piecewise_constant_distribution<_RealType>::param_type::param_type(
268         size_t __nw, result_type __xmin, result_type __xmax, _UnaryOperation __fw)
269     : __b_(__nw == 0 ? 2 : __nw + 1)
270 {
271     size_t __n = __b_.size() - 1;
272     result_type __d = (__xmax - __xmin) / __n;
273     __densities_.reserve(__n);
274     for (size_t __i = 0; __i < __n; ++__i)
275     {
276         __b_[__i] = __xmin + __i * __d;
277         __densities_.push_back(__fw(__b_[__i] + __d*.5));
278     }
279     __b_[__n] = __xmax;
280     __init();
281 }
282 
283 template<class _RealType>
284 template<class _URNG>
285 _RealType
286 piecewise_constant_distribution<_RealType>::operator()(_URNG& __g, const param_type& __p)
287 {
288     static_assert(__libcpp_random_is_valid_urng<_URNG>::value, "");
289     typedef uniform_real_distribution<result_type> _Gen;
290     result_type __u = _Gen()(__g);
291     ptrdiff_t __k = _VSTD::upper_bound(__p.__areas_.begin(), __p.__areas_.end(),
292                                       __u) - __p.__areas_.begin() - 1;
293     return (__u - __p.__areas_[__k]) / __p.__densities_[__k] + __p.__b_[__k];
294 }
295 
296 template <class _CharT, class _Traits, class _RT>
297 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
298 operator<<(basic_ostream<_CharT, _Traits>& __os,
299            const piecewise_constant_distribution<_RT>& __x)
300 {
301     __save_flags<_CharT, _Traits> __lx(__os);
302     typedef basic_ostream<_CharT, _Traits> _OStream;
303     __os.flags(_OStream::dec | _OStream::left | _OStream::fixed |
304                _OStream::scientific);
305     _CharT __sp = __os.widen(' ');
306     __os.fill(__sp);
307     size_t __n = __x.__p_.__b_.size();
308     __os << __n;
309     for (size_t __i = 0; __i < __n; ++__i)
310         __os << __sp << __x.__p_.__b_[__i];
311     __n = __x.__p_.__densities_.size();
312     __os << __sp << __n;
313     for (size_t __i = 0; __i < __n; ++__i)
314         __os << __sp << __x.__p_.__densities_[__i];
315     __n = __x.__p_.__areas_.size();
316     __os << __sp << __n;
317     for (size_t __i = 0; __i < __n; ++__i)
318         __os << __sp << __x.__p_.__areas_[__i];
319     return __os;
320 }
321 
322 template <class _CharT, class _Traits, class _RT>
323 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
324 operator>>(basic_istream<_CharT, _Traits>& __is,
325            piecewise_constant_distribution<_RT>& __x)
326 {
327     typedef piecewise_constant_distribution<_RT> _Eng;
328     typedef typename _Eng::result_type result_type;
329     __save_flags<_CharT, _Traits> __lx(__is);
330     typedef basic_istream<_CharT, _Traits> _Istream;
331     __is.flags(_Istream::dec | _Istream::skipws);
332     size_t __n;
333     __is >> __n;
334     vector<result_type> __b(__n);
335     for (size_t __i = 0; __i < __n; ++__i)
336         __is >> __b[__i];
337     __is >> __n;
338     vector<result_type> __densities(__n);
339     for (size_t __i = 0; __i < __n; ++__i)
340         __is >> __densities[__i];
341     __is >> __n;
342     vector<result_type> __areas(__n);
343     for (size_t __i = 0; __i < __n; ++__i)
344         __is >> __areas[__i];
345     if (!__is.fail())
346     {
347         swap(__x.__p_.__b_, __b);
348         swap(__x.__p_.__densities_, __densities);
349         swap(__x.__p_.__areas_, __areas);
350     }
351     return __is;
352 }
353 
354 _LIBCPP_END_NAMESPACE_STD
355 
356 _LIBCPP_POP_MACROS
357 
358 #endif // _LIBCPP___RANDOM_PIECEWISE_CONSTANT_DISTRIBUTION_H
359