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// -*- 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>
// Basic random number facility, adapted from N3551:
namespace ceph::util {
inline namespace version_1_0_2 {
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)
{
std::random_device 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()
{
std::random_device 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;
std::random_device 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);
}
};
} // inline namespace version_*
} // namespace ceph::util
#endif
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