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random_romu_32
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/*
Copyright (C) 2018-2024 Geoffrey Daniels. https://gpdaniels.com/
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, version 3 of the License only.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
#pragma once
#ifndef GTL_RANDOM_RANDOM_ROMU_32_HPP
#define GTL_RANDOM_RANDOM_ROMU_32_HPP
// Summary: Romu 32 bit pseudo-random number generator.
#ifndef NDEBUG
# if defined(_MSC_VER)
# define __builtin_trap() __debugbreak()
# endif
/// @brief A simple assert macro to break the program if the random_romu_32 is misused.
# define GTL_RANDOM_ROMU_32_ASSERT(ASSERTION, MESSAGE) static_cast<void>((ASSERTION) || (__builtin_trap(), 0))
#else
/// @brief At release time the assert macro is implemented as a nop.
# define GTL_RANDOM_ROMU_32_ASSERT(ASSERTION, MESSAGE) static_cast<void>(0)
#endif
namespace gtl {
class random_romu_32 final {
private:
unsigned int state[4];
private:
constexpr static unsigned int rotate_left(unsigned int value, unsigned int shift) {
constexpr const unsigned int mask = (8 * sizeof(unsigned int) - 1);
shift &= mask;
return (value << shift) | (value >> ((static_cast<unsigned int>(-static_cast<signed int>(shift))) & mask));
}
public:
/// @brief Defaulted destructor.
~random_romu_32() = default;
/// @brief Empty constructor.
random_romu_32()
: state{ 0x834E78E9u, 0x5C964FABu, 0xD33C9B5Du, 0xAE9B49BBu } {
}
/// @brief Defaulted copy constructor.
random_romu_32(const random_romu_32&) = default;
/// @brief Defaulted move constructor.
random_romu_32(random_romu_32&&) = default;
/// @brief Defaulted copy assignment.
random_romu_32& operator=(const random_romu_32&) = default;
/// @brief Defaulted move assignment.
random_romu_32& operator=(random_romu_32&&) = default;
/// @brief Constructor with 32 bit seed.
/// @param seed_value Seed value used to initialise the state.
random_romu_32(unsigned int seed_value) {
this->seed(seed_value);
}
/// @brief Constructor using four 32 bit values as seed.
/// @param seed_value_0 Seed value used to initialise part of the state.
/// @param seed_value_1 Seed value used to initialise part of the state.
/// @param seed_value_2 Seed value used to initialise part of the state.
/// @param seed_value_3 Seed value used to initialise part of the state.
random_romu_32(unsigned int seed_value_0, unsigned int seed_value_1, unsigned int seed_value_2, unsigned int seed_value_3) {
this->seed(seed_value_0, seed_value_1, seed_value_2, seed_value_3);
}
/// @brief Initialise the state from a 32 bit seed.
/// @param seed_value Seed value used to initialise the state.
void seed(unsigned int seed_value) {
this->state[0] = seed_value ^ 0x55555555u;
this->state[1] = seed_value ^ 0x33333333u;
this->state[2] = seed_value ^ 0x0F0F0F0Fu;
this->state[3] = seed_value ^ 0x00FF00FFu;
}
/// @brief Initialise the state from four 32 bit values as seed.
/// @param seed_value_0 Seed value used to initialise part of the state.
/// @param seed_value_1 Seed value used to initialise part of the state.
/// @param seed_value_2 Seed value used to initialise part of the state.
/// @param seed_value_3 Seed value used to initialise part of the state.
void seed(unsigned int seed_value_0, unsigned int seed_value_1, unsigned int seed_value_2, unsigned int seed_value_3) {
this->state[0] = seed_value_0;
this->state[1] = seed_value_1;
this->state[2] = seed_value_2;
this->state[3] = seed_value_3;
}
/// @brief Get the next random number from the generator_type.
/// @return A pseudo-random number.
unsigned int get_random_raw() {
const unsigned int wp = this->state[0];
const unsigned int xp = this->state[1];
const unsigned int yp = this->state[2];
const unsigned int zp = this->state[3];
this->state[0] = 3323815723u * zp;
this->state[1] = zp + rotate_left(wp, 26);
this->state[2] = yp - xp;
this->state[3] = yp + wp;
this->state[3] = rotate_left(this->state[3], 9);
return xp;
}
public:
/// @brief Get a random number in the open interval 0 < value < 1.
/// @return A pseudo-random number.
double get_random_exclusive() {
return (static_cast<double>(this->get_random_raw()) + 0.5) * (1.0 / static_cast<double>(1ull << 32));
}
/// @brief Get a random number in the half-open interval 0 <= value < 1.
/// @return A pseudo-random number.
double get_random_exclusive_top() {
return static_cast<double>(this->get_random_raw()) * (1.0 / static_cast<double>(1ull << 32));
}
/// @brief Get a random number in the closed interval 0 <= value <= 1.
/// @return A pseudo-random number.
double get_random_inclusive() {
return static_cast<double>(this->get_random_raw()) * (1.0 / static_cast<double>((1ull << 32) - 1));
}
/// @brief Get a random number between two bounds.
/// @param inclusive_min Minimum number that can be returned.
/// @param inclusive_max Max number than can be returned.
/// @return A pseudo-random number.
unsigned int get_random(unsigned int inclusive_min, unsigned int inclusive_max) {
GTL_RANDOM_ROMU_32_ASSERT(inclusive_min < inclusive_max, "Minimum bound must be lower than maximum bound.");
return (this->get_random_raw() % (1 + inclusive_max - inclusive_min)) + inclusive_min;
}
/// @brief Get a random number between two bounds.
/// @param inclusive_min Minimum number that can be returned.
/// @param inclusive_max Max number than can be returned.
/// @return A pseudo-random number.
double get_random(double inclusive_min, double inclusive_max) {
GTL_RANDOM_ROMU_32_ASSERT(inclusive_min < inclusive_max, "Minimum bound must be lower than maximum bound.");
return (this->get_random_inclusive() * (inclusive_max - inclusive_min)) + inclusive_min;
}
};
}
#undef GTL_RANDOM_ROMU_32_ASSERT
#endif // GTL_RANDOM_RANDOM_ROMU_32_HPP