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
360