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
31template <class _RealType = double>
32class piecewise_constant_distribution {
33 static_assert(__libcpp_random_is_valid_realtype<_RealType>::value,
34 "RealType must be a supported floating-point type");
35
36public:
37 // types
38 typedef _RealType result_type;
39
40 class 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
82private:
83 param_type __p_;
84
85public:
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
144template <class _RealType>
145typename piecewise_constant_distribution<_RealType>::param_type&
146piecewise_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
159template <class _RealType>
160void 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
175template <class _RealType>
176piecewise_constant_distribution<_RealType>::param_type::param_type() : __b_(2), __densities_(1, 1.0), __areas_(1, 0.0) {
177 __b_[1] = 1;
178}
179
180template <class _RealType>
181template <class _InputIteratorB, class _InputIteratorW>
182piecewise_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
201template <class _RealType>
202template <class _UnaryOperation>
203piecewise_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
222template <class _RealType>
223template <class _UnaryOperation>
224piecewise_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
238template <class _RealType>
239template <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
248template <class _CharT, class _Traits, class _RT>
249_LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
250operator<<(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
271template <class _CharT, class _Traits, class _RT>
272_LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
273operator>>(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
305