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Diffstat (limited to 'src/include/random.h')
| -rw-r--r-- | src/include/random.h | 301 |
1 files changed, 301 insertions, 0 deletions
diff --git a/src/include/random.h b/src/include/random.h new file mode 100644 index 000000000..f2e3e37bc --- /dev/null +++ b/src/include/random.h @@ -0,0 +1,301 @@ +// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*- +// vim: ts=8 sw=2 smarttab +/* + * Ceph - scalable distributed file system + * + * Copyright (C) 2017 SUSE LINUX GmbH + * + * This is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License version 2.1, as published by the Free Software + * Foundation. See file COPYING. + * +*/ + +#ifndef CEPH_RANDOM_H +#define CEPH_RANDOM_H 1 + +#include <mutex> +#include <random> +#include <type_traits> +#include <boost/optional.hpp> + +// Workaround for https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85494 +#ifdef __MINGW32__ +#include <boost/random/random_device.hpp> + +using random_device_t = boost::random::random_device; +#else +using random_device_t = std::random_device; +#endif + +// Basic random number facility (see N3551 for inspiration): +namespace ceph::util { + +inline namespace version_1_0_3 { + +namespace detail { + +template <typename T0, typename T1> +using larger_of = typename std::conditional< + sizeof(T0) >= sizeof(T1), + T0, T1> + ::type; + +// avoid mixing floating point and integers: +template <typename NumberT0, typename NumberT1> +using has_compatible_numeric_types = + std::disjunction< + std::conjunction< + std::is_floating_point<NumberT0>, std::is_floating_point<NumberT1> + >, + std::conjunction< + std::is_integral<NumberT0>, std::is_integral<NumberT1> + > + >; + + +// Select the larger of type compatible numeric types: +template <typename NumberT0, typename NumberT1> +using select_number_t = std::enable_if_t<detail::has_compatible_numeric_types<NumberT0, NumberT1>::value, + detail::larger_of<NumberT0, NumberT1>>; + +} // namespace detail + +namespace detail { + +// Choose default distribution for appropriate types: +template <typename NumberT, + bool IsIntegral> +struct select_distribution +{ + using type = std::uniform_int_distribution<NumberT>; +}; + +template <typename NumberT> +struct select_distribution<NumberT, false> +{ + using type = std::uniform_real_distribution<NumberT>; +}; + +template <typename NumberT> +using default_distribution = typename + select_distribution<NumberT, std::is_integral<NumberT>::value>::type; + +} // namespace detail + +namespace detail { + +template <typename EngineT> +EngineT& engine(); + +template <typename MutexT, typename EngineT, + typename SeedT = typename EngineT::result_type> +void randomize_rng(const SeedT seed, MutexT& m, EngineT& e) +{ + std::lock_guard<MutexT> lg(m); + e.seed(seed); +} + +template <typename MutexT, typename EngineT> +void randomize_rng(MutexT& m, EngineT& e) +{ + random_device_t rd; + + std::lock_guard<MutexT> lg(m); + e.seed(rd()); +} + +template <typename EngineT = std::default_random_engine, + typename SeedT = typename EngineT::result_type> +void randomize_rng(const SeedT n) +{ + detail::engine<EngineT>().seed(n); +} + +template <typename EngineT = std::default_random_engine> +void randomize_rng() +{ + random_device_t rd; + detail::engine<EngineT>().seed(rd()); +} + +template <typename EngineT> +EngineT& engine() +{ + thread_local boost::optional<EngineT> rng_engine; + + if (!rng_engine) { + rng_engine.emplace(EngineT()); + randomize_rng<EngineT>(); + } + + return *rng_engine; +} + +} // namespace detail + +namespace detail { + +template <typename NumberT, + typename DistributionT = detail::default_distribution<NumberT>, + typename EngineT> +NumberT generate_random_number(const NumberT min, const NumberT max, + EngineT& e) +{ + DistributionT d { min, max }; + + using param_type = typename DistributionT::param_type; + return d(e, param_type { min, max }); +} + +template <typename NumberT, + typename MutexT, + typename DistributionT = detail::default_distribution<NumberT>, + typename EngineT> +NumberT generate_random_number(const NumberT min, const NumberT max, + MutexT& m, EngineT& e) +{ + DistributionT d { min, max }; + + using param_type = typename DistributionT::param_type; + + std::lock_guard<MutexT> lg(m); + return d(e, param_type { min, max }); +} + +template <typename NumberT, + typename DistributionT = detail::default_distribution<NumberT>, + typename EngineT> +NumberT generate_random_number(const NumberT min, const NumberT max) +{ + return detail::generate_random_number<NumberT, DistributionT, EngineT> + (min, max, detail::engine<EngineT>()); +} + +template <typename MutexT, + typename EngineT, + typename NumberT = int, + typename DistributionT = detail::default_distribution<NumberT>> +NumberT generate_random_number(MutexT& m, EngineT& e) +{ + return detail::generate_random_number<NumberT, MutexT, DistributionT, EngineT> + (0, std::numeric_limits<NumberT>::max(), m, e); +} + +template <typename NumberT, typename MutexT, typename EngineT> +NumberT generate_random_number(const NumberT max, MutexT& m, EngineT& e) +{ + return generate_random_number<NumberT>(0, max, m, e); +} + +} // namespace detail + +template <typename EngineT = std::default_random_engine> +void randomize_rng() +{ + detail::randomize_rng<EngineT>(); +} + +template <typename NumberT = int, + typename DistributionT = detail::default_distribution<NumberT>, + typename EngineT = std::default_random_engine> +NumberT generate_random_number() +{ + return detail::generate_random_number<NumberT, DistributionT, EngineT> + (0, std::numeric_limits<NumberT>::max()); +} + +template <typename NumberT0, typename NumberT1, + typename NumberT = detail::select_number_t<NumberT0, NumberT1> + > +NumberT generate_random_number(const NumberT0 min, const NumberT1 max) +{ + return detail::generate_random_number<NumberT, + detail::default_distribution<NumberT>, + std::default_random_engine> + (static_cast<NumberT>(min), static_cast<NumberT>(max)); +} + +template <typename NumberT0, typename NumberT1, + typename DistributionT, + typename EngineT, + typename NumberT = detail::select_number_t<NumberT0, NumberT1> + > +NumberT generate_random_number(const NumberT min, const NumberT max, + EngineT& e) +{ + return detail::generate_random_number<NumberT, + DistributionT, + EngineT>(static_cast<NumberT>(min), static_cast<NumberT>(max), e); +} + +template <typename NumberT> +NumberT generate_random_number(const NumberT max) +{ + return generate_random_number<NumberT>(0, max); +} + +// Function object: +template <typename NumberT> +class random_number_generator final +{ + std::mutex l; + random_device_t rd; + std::default_random_engine e; + + using seed_type = typename decltype(e)::result_type; + + public: + using number_type = NumberT; + using random_engine_type = decltype(e); + using random_device_type = decltype(rd); + + public: + random_device_type& random_device() noexcept { return rd; } + random_engine_type& random_engine() noexcept { return e; } + + public: + random_number_generator() { + detail::randomize_rng(l, e); + } + + explicit random_number_generator(const seed_type seed) { + detail::randomize_rng(seed, l, e); + } + + random_number_generator(random_number_generator&& rhs) + : e(std::move(rhs.e)) + {} + + public: + random_number_generator(const random_number_generator&) = delete; + random_number_generator& operator=(const random_number_generator&) = delete; + + public: + NumberT operator()() { + return detail::generate_random_number(l, e); + } + + NumberT operator()(const NumberT max) { + return detail::generate_random_number<NumberT>(max, l, e); + } + + NumberT operator()(const NumberT min, const NumberT max) { + return detail::generate_random_number<NumberT>(min, max, l, e); + } + + public: + void seed(const seed_type n) { + detail::randomize_rng(n, l, e); + } +}; + +template <typename NumberT> +random_number_generator(const NumberT max) -> random_number_generator<NumberT>; + +} // inline namespace version_* + +} // namespace ceph::util + +#endif |