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1 | // -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*- |
2 | // vim: ts=8 sw=2 smarttab | |
3 | /* | |
4 | * Ceph - scalable distributed file system | |
5 | * | |
6 | * Copyright (C) 2017 SUSE LINUX GmbH | |
7 | * | |
8 | * This is free software; you can redistribute it and/or | |
9 | * modify it under the terms of the GNU Lesser General Public | |
10 | * License version 2.1, as published by the Free Software | |
11 | * Foundation. See file COPYING. | |
12 | * | |
13 | */ | |
14 | ||
15 | #ifndef CEPH_RANDOM_H | |
16 | #define CEPH_RANDOM_H 1 | |
17 | ||
18 | #include <mutex> | |
19 | #include <random> | |
20 | #include <type_traits> | |
21 | #include <boost/optional.hpp> | |
22 | ||
9f95a23c | 23 | // Basic random number facility (see N3551 for inspiration): |
11fdf7f2 TL |
24 | namespace ceph::util { |
25 | ||
9f95a23c | 26 | inline namespace version_1_0_3 { |
11fdf7f2 TL |
27 | |
28 | namespace detail { | |
29 | ||
30 | template <typename T0, typename T1> | |
31 | using larger_of = typename std::conditional< | |
32 | sizeof(T0) >= sizeof(T1), | |
33 | T0, T1> | |
34 | ::type; | |
35 | ||
36 | // avoid mixing floating point and integers: | |
37 | template <typename NumberT0, typename NumberT1> | |
38 | using has_compatible_numeric_types = | |
39 | std::disjunction< | |
40 | std::conjunction< | |
41 | std::is_floating_point<NumberT0>, std::is_floating_point<NumberT1> | |
42 | >, | |
43 | std::conjunction< | |
44 | std::is_integral<NumberT0>, std::is_integral<NumberT1> | |
45 | > | |
46 | >; | |
47 | ||
48 | ||
49 | // Select the larger of type compatible numeric types: | |
50 | template <typename NumberT0, typename NumberT1> | |
51 | using select_number_t = std::enable_if_t<detail::has_compatible_numeric_types<NumberT0, NumberT1>::value, | |
52 | detail::larger_of<NumberT0, NumberT1>>; | |
53 | ||
54 | } // namespace detail | |
55 | ||
56 | namespace detail { | |
57 | ||
58 | // Choose default distribution for appropriate types: | |
59 | template <typename NumberT, | |
60 | bool IsIntegral> | |
61 | struct select_distribution | |
62 | { | |
63 | using type = std::uniform_int_distribution<NumberT>; | |
64 | }; | |
65 | ||
66 | template <typename NumberT> | |
67 | struct select_distribution<NumberT, false> | |
68 | { | |
69 | using type = std::uniform_real_distribution<NumberT>; | |
70 | }; | |
71 | ||
72 | template <typename NumberT> | |
73 | using default_distribution = typename | |
74 | select_distribution<NumberT, std::is_integral<NumberT>::value>::type; | |
75 | ||
76 | } // namespace detail | |
77 | ||
78 | namespace detail { | |
79 | ||
80 | template <typename EngineT> | |
81 | EngineT& engine(); | |
82 | ||
83 | template <typename MutexT, typename EngineT, | |
84 | typename SeedT = typename EngineT::result_type> | |
85 | void randomize_rng(const SeedT seed, MutexT& m, EngineT& e) | |
86 | { | |
87 | std::lock_guard<MutexT> lg(m); | |
88 | e.seed(seed); | |
89 | } | |
90 | ||
91 | template <typename MutexT, typename EngineT> | |
92 | void randomize_rng(MutexT& m, EngineT& e) | |
93 | { | |
94 | std::random_device rd; | |
95 | ||
96 | std::lock_guard<MutexT> lg(m); | |
97 | e.seed(rd()); | |
98 | } | |
99 | ||
100 | template <typename EngineT = std::default_random_engine, | |
101 | typename SeedT = typename EngineT::result_type> | |
102 | void randomize_rng(const SeedT n) | |
103 | { | |
104 | detail::engine<EngineT>().seed(n); | |
105 | } | |
106 | ||
107 | template <typename EngineT = std::default_random_engine> | |
108 | void randomize_rng() | |
109 | { | |
110 | std::random_device rd; | |
111 | detail::engine<EngineT>().seed(rd()); | |
112 | } | |
113 | ||
114 | template <typename EngineT> | |
115 | EngineT& engine() | |
116 | { | |
117 | thread_local boost::optional<EngineT> rng_engine; | |
118 | ||
119 | if (!rng_engine) { | |
120 | rng_engine.emplace(EngineT()); | |
121 | randomize_rng<EngineT>(); | |
122 | } | |
123 | ||
124 | return *rng_engine; | |
125 | } | |
126 | ||
127 | } // namespace detail | |
128 | ||
129 | namespace detail { | |
130 | ||
131 | template <typename NumberT, | |
132 | typename DistributionT = detail::default_distribution<NumberT>, | |
133 | typename EngineT> | |
134 | NumberT generate_random_number(const NumberT min, const NumberT max, | |
135 | EngineT& e) | |
136 | { | |
137 | DistributionT d { min, max }; | |
138 | ||
139 | using param_type = typename DistributionT::param_type; | |
140 | return d(e, param_type { min, max }); | |
141 | } | |
142 | ||
143 | template <typename NumberT, | |
144 | typename MutexT, | |
145 | typename DistributionT = detail::default_distribution<NumberT>, | |
146 | typename EngineT> | |
147 | NumberT generate_random_number(const NumberT min, const NumberT max, | |
148 | MutexT& m, EngineT& e) | |
149 | { | |
150 | DistributionT d { min, max }; | |
151 | ||
152 | using param_type = typename DistributionT::param_type; | |
153 | ||
154 | std::lock_guard<MutexT> lg(m); | |
155 | return d(e, param_type { min, max }); | |
156 | } | |
157 | ||
158 | template <typename NumberT, | |
159 | typename DistributionT = detail::default_distribution<NumberT>, | |
160 | typename EngineT> | |
161 | NumberT generate_random_number(const NumberT min, const NumberT max) | |
162 | { | |
163 | return detail::generate_random_number<NumberT, DistributionT, EngineT> | |
164 | (min, max, detail::engine<EngineT>()); | |
165 | } | |
166 | ||
167 | template <typename MutexT, | |
168 | typename EngineT, | |
169 | typename NumberT = int, | |
170 | typename DistributionT = detail::default_distribution<NumberT>> | |
171 | NumberT generate_random_number(MutexT& m, EngineT& e) | |
172 | { | |
173 | return detail::generate_random_number<NumberT, MutexT, DistributionT, EngineT> | |
174 | (0, std::numeric_limits<NumberT>::max(), m, e); | |
175 | } | |
176 | ||
177 | template <typename NumberT, typename MutexT, typename EngineT> | |
178 | NumberT generate_random_number(const NumberT max, MutexT& m, EngineT& e) | |
179 | { | |
180 | return generate_random_number<NumberT>(0, max, m, e); | |
181 | } | |
182 | ||
183 | } // namespace detail | |
184 | ||
185 | template <typename EngineT = std::default_random_engine> | |
186 | void randomize_rng() | |
187 | { | |
188 | detail::randomize_rng<EngineT>(); | |
189 | } | |
190 | ||
191 | template <typename NumberT = int, | |
192 | typename DistributionT = detail::default_distribution<NumberT>, | |
193 | typename EngineT = std::default_random_engine> | |
194 | NumberT generate_random_number() | |
195 | { | |
196 | return detail::generate_random_number<NumberT, DistributionT, EngineT> | |
197 | (0, std::numeric_limits<NumberT>::max()); | |
198 | } | |
199 | ||
200 | template <typename NumberT0, typename NumberT1, | |
201 | typename NumberT = detail::select_number_t<NumberT0, NumberT1> | |
202 | > | |
203 | NumberT generate_random_number(const NumberT0 min, const NumberT1 max) | |
204 | { | |
205 | return detail::generate_random_number<NumberT, | |
206 | detail::default_distribution<NumberT>, | |
207 | std::default_random_engine> | |
208 | (static_cast<NumberT>(min), static_cast<NumberT>(max)); | |
209 | } | |
210 | ||
211 | template <typename NumberT0, typename NumberT1, | |
212 | typename DistributionT, | |
213 | typename EngineT, | |
214 | typename NumberT = detail::select_number_t<NumberT0, NumberT1> | |
215 | > | |
216 | NumberT generate_random_number(const NumberT min, const NumberT max, | |
217 | EngineT& e) | |
218 | { | |
219 | return detail::generate_random_number<NumberT, | |
220 | DistributionT, | |
221 | EngineT>(static_cast<NumberT>(min), static_cast<NumberT>(max), e); | |
222 | } | |
223 | ||
224 | template <typename NumberT> | |
225 | NumberT generate_random_number(const NumberT max) | |
226 | { | |
227 | return generate_random_number<NumberT>(0, max); | |
228 | } | |
229 | ||
230 | // Function object: | |
231 | template <typename NumberT> | |
232 | class random_number_generator final | |
233 | { | |
234 | std::mutex l; | |
235 | std::random_device rd; | |
236 | std::default_random_engine e; | |
237 | ||
238 | using seed_type = typename decltype(e)::result_type; | |
239 | ||
240 | public: | |
241 | using number_type = NumberT; | |
242 | using random_engine_type = decltype(e); | |
243 | using random_device_type = decltype(rd); | |
244 | ||
245 | public: | |
246 | random_device_type& random_device() noexcept { return rd; } | |
247 | random_engine_type& random_engine() noexcept { return e; } | |
248 | ||
249 | public: | |
250 | random_number_generator() { | |
251 | detail::randomize_rng(l, e); | |
252 | } | |
253 | ||
254 | explicit random_number_generator(const seed_type seed) { | |
255 | detail::randomize_rng(seed, l, e); | |
256 | } | |
257 | ||
258 | random_number_generator(random_number_generator&& rhs) | |
259 | : e(std::move(rhs.e)) | |
260 | {} | |
261 | ||
262 | public: | |
263 | random_number_generator(const random_number_generator&) = delete; | |
264 | random_number_generator& operator=(const random_number_generator&) = delete; | |
265 | ||
266 | public: | |
267 | NumberT operator()() { | |
268 | return detail::generate_random_number(l, e); | |
269 | } | |
270 | ||
271 | NumberT operator()(const NumberT max) { | |
272 | return detail::generate_random_number<NumberT>(max, l, e); | |
273 | } | |
274 | ||
275 | NumberT operator()(const NumberT min, const NumberT max) { | |
276 | return detail::generate_random_number<NumberT>(min, max, l, e); | |
277 | } | |
278 | ||
279 | public: | |
280 | void seed(const seed_type n) { | |
281 | detail::randomize_rng(n, l, e); | |
282 | } | |
283 | }; | |
284 | ||
9f95a23c TL |
285 | template <typename NumberT> |
286 | random_number_generator(const NumberT max) -> random_number_generator<NumberT>; | |
287 | ||
11fdf7f2 TL |
288 | } // inline namespace version_* |
289 | ||
290 | } // namespace ceph::util | |
291 | ||
292 | #endif |