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
29template <class _RealType = double>
30class _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
34public:
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
58 _LIBCPP_HIDE_FROM_ABI vector<result_type> intervals() const { return __b_; }
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
80private:
81 param_type __p_;
82
83public:
84 // constructor and reset functions
85 _LIBCPP_HIDE_FROM_ABI piecewise_constant_distribution() {}
86 template <class _InputIteratorB, class _InputIteratorW>
87 _LIBCPP_HIDE_FROM_ABI
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>
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
99 piecewise_constant_distribution(size_t __nw, result_type __xmin, result_type __xmax, _UnaryOperation __fw)
100 : __p_(__nw, __xmin, __xmax, __fw) {}
101
102 _LIBCPP_HIDE_FROM_ABI explicit piecewise_constant_distribution(const param_type& __p) : __p_(__p) {}
103
104 _LIBCPP_HIDE_FROM_ABI void reset() {}
105
106 // generating functions
107 template <class _URNG>
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
115 _LIBCPP_HIDE_FROM_ABI vector<result_type> intervals() const { return __p_.intervals(); }
116 _LIBCPP_HIDE_FROM_ABI vector<result_type> densities() const { return __p_.densities(); }
117
118 _LIBCPP_HIDE_FROM_ABI param_type param() const { return __p_; }
119 _LIBCPP_HIDE_FROM_ABI void param(const param_type& __p) { __p_ = __p; }
120
121 _LIBCPP_HIDE_FROM_ABI result_type min() const { return __p_.__b_.front(); }
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
142template <class _RealType>
143typename piecewise_constant_distribution<_RealType>::param_type&
144piecewise_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
157template <class _RealType>
158void 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
173template <class _RealType>
174piecewise_constant_distribution<_RealType>::param_type::param_type() : __b_(2), __densities_(1, 1.0), __areas_(1, 0.0) {
175 __b_[1] = 1;
176}
177
178template <class _RealType>
179template <class _InputIteratorB, class _InputIteratorW>
180piecewise_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
199template <class _RealType>
200template <class _UnaryOperation>
201piecewise_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
220template <class _RealType>
221template <class _UnaryOperation>
222piecewise_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
236template <class _RealType>
237template <class _URNG>
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
246template <class _CharT, class _Traits, class _RT>
247_LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
248operator<<(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
269template <class _CharT, class _Traits, class _RT>
270_LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
271operator>>(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