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/* SPDX-License-Identifier: BSL-1.0 OR BSD-3-Clause */
#ifndef MPT_RANDOM_ENGINE_HPP
#define MPT_RANDOM_ENGINE_HPP
#include "mpt/base/macros.hpp"
#include "mpt/base/namespace.hpp"
#include "mpt/random/seed.hpp"
#include <memory>
#include <random>
#include <cstddef>
namespace mpt {
inline namespace MPT_INLINE_NS {
template <typename Trng>
struct engine_traits {
typedef typename Trng::result_type result_type;
static MPT_CONSTEXPRINLINE int result_bits() {
return Trng::result_bits();
}
template <typename Trd>
static inline Trng make(Trd & rd) {
return Trng(rd);
}
};
// C++11 random does not provide any sane way to determine the amount of entropy
// required to seed a particular engine. VERY STUPID.
// List the ones we are likely to use.
template <>
struct engine_traits<std::mt19937> {
enum : std::size_t {
seed_bits = sizeof(std::mt19937::result_type) * 8 * std::mt19937::state_size
};
typedef std::mt19937 rng_type;
typedef rng_type::result_type result_type;
static MPT_CONSTEXPRINLINE int result_bits() {
return rng_type::word_size;
}
template <typename Trd>
static inline rng_type make(Trd & rd) {
std::unique_ptr<mpt::seed_seq_values<seed_bits / sizeof(unsigned int)>> values = std::make_unique<mpt::seed_seq_values<seed_bits / sizeof(unsigned int)>>(rd);
std::seed_seq seed(values->begin(), values->end());
return rng_type(seed);
}
};
template <>
struct engine_traits<std::mt19937_64> {
enum : std::size_t {
seed_bits = sizeof(std::mt19937_64::result_type) * 8 * std::mt19937_64::state_size
};
typedef std::mt19937_64 rng_type;
typedef rng_type::result_type result_type;
static MPT_CONSTEXPRINLINE int result_bits() {
return rng_type::word_size;
}
template <typename Trd>
static inline rng_type make(Trd & rd) {
std::unique_ptr<mpt::seed_seq_values<seed_bits / sizeof(unsigned int)>> values = std::make_unique<mpt::seed_seq_values<seed_bits / sizeof(unsigned int)>>(rd);
std::seed_seq seed(values->begin(), values->end());
return rng_type(seed);
}
};
template <>
struct engine_traits<std::ranlux24_base> {
enum : std::size_t {
seed_bits = std::ranlux24_base::word_size
};
typedef std::ranlux24_base rng_type;
typedef rng_type::result_type result_type;
static MPT_CONSTEXPRINLINE int result_bits() {
return rng_type::word_size;
}
template <typename Trd>
static inline rng_type make(Trd & rd) {
mpt::seed_seq_values<seed_bits / sizeof(unsigned int)> values(rd);
std::seed_seq seed(values.begin(), values.end());
return rng_type(seed);
}
};
template <>
struct engine_traits<std::ranlux48_base> {
enum : std::size_t {
seed_bits = std::ranlux48_base::word_size
};
typedef std::ranlux48_base rng_type;
typedef rng_type::result_type result_type;
static MPT_CONSTEXPRINLINE int result_bits() {
return rng_type::word_size;
}
template <typename Trd>
static inline rng_type make(Trd & rd) {
mpt::seed_seq_values<seed_bits / sizeof(unsigned int)> values(rd);
std::seed_seq seed(values.begin(), values.end());
return rng_type(seed);
}
};
template <>
struct engine_traits<std::ranlux24> {
enum : std::size_t {
seed_bits = std::ranlux24_base::word_size
};
typedef std::ranlux24 rng_type;
typedef rng_type::result_type result_type;
static MPT_CONSTEXPRINLINE int result_bits() {
return std::ranlux24_base::word_size;
}
template <typename Trd>
static inline rng_type make(Trd & rd) {
mpt::seed_seq_values<seed_bits / sizeof(unsigned int)> values(rd);
std::seed_seq seed(values.begin(), values.end());
return rng_type(seed);
}
};
template <>
struct engine_traits<std::ranlux48> {
enum : std::size_t {
seed_bits = std::ranlux48_base::word_size
};
typedef std::ranlux48 rng_type;
typedef rng_type::result_type result_type;
static MPT_CONSTEXPRINLINE int result_bits() {
return std::ranlux48_base::word_size;
}
template <typename Trd>
static inline rng_type make(Trd & rd) {
mpt::seed_seq_values<seed_bits / sizeof(unsigned int)> values(rd);
std::seed_seq seed(values.begin(), values.end());
return rng_type(seed);
}
};
template <typename Trng, typename Trd>
inline Trng make_prng(Trd & rd) {
return mpt::engine_traits<Trng>::make(rd);
}
} // namespace MPT_INLINE_NS
} // namespace mpt
#endif // MPT_RANDOM_ENGINE_HPP
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