/*
|
|
* Copyright (C) 2023 Christopher J. Howard
|
|
*
|
|
* This file is part of Antkeeper source code.
|
|
*
|
|
* Antkeeper source code 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, either version 3 of the License, or
|
|
* (at your option) any later version.
|
|
*
|
|
* Antkeeper source code 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 Antkeeper source code. If not, see <http://www.gnu.org/licenses/>.
|
|
*/
|
|
|
|
#ifndef ANTKEEPER_MATH_HASH_PCG_HPP
|
|
#define ANTKEEPER_MATH_HASH_PCG_HPP
|
|
|
|
#include "math/vector.hpp"
|
|
#include "math/hash/make-uint.hpp"
|
|
#include <cstdint>
|
|
#include <type_traits>
|
|
|
|
namespace math {
|
|
namespace hash {
|
|
|
|
/// @private
|
|
template <class T>
|
|
constexpr T pcg_multiplier = 0;
|
|
template <>
|
|
constexpr std::uint8_t pcg_multiplier<std::uint8_t> = 141U;
|
|
template <>
|
|
constexpr std::uint16_t pcg_multiplier<std::uint16_t> = 12829U;
|
|
template <>
|
|
constexpr std::uint32_t pcg_multiplier<std::uint32_t> = 747796405UL;
|
|
template <>
|
|
constexpr std::uint64_t pcg_multiplier<std::uint64_t> = 6364136223846793005ULL;
|
|
|
|
/// @private
|
|
template <class T>
|
|
constexpr T pcg_increment = 0;
|
|
template <>
|
|
constexpr std::uint8_t pcg_increment<std::uint8_t> = 77U;
|
|
template <>
|
|
constexpr std::uint16_t pcg_increment<std::uint16_t> = 47989U;
|
|
template <>
|
|
constexpr std::uint32_t pcg_increment<std::uint32_t> = 2891336453UL;
|
|
template <>
|
|
constexpr std::uint64_t pcg_increment<std::uint64_t> = 1442695040888963407ULL;
|
|
|
|
/// @private
|
|
template <class T>
|
|
constexpr T mcg_multiplier = 0;
|
|
template <>
|
|
constexpr std::uint8_t mcg_multiplier<std::uint8_t> = 217U;
|
|
template <>
|
|
constexpr std::uint16_t mcg_multiplier<std::uint16_t> = 62169U;
|
|
template <>
|
|
constexpr std::uint32_t mcg_multiplier<std::uint32_t> = 277803737UL;
|
|
template <>
|
|
constexpr std::uint64_t mcg_multiplier<std::uint64_t> = 12605985483714917081ULL;
|
|
|
|
/// @private
|
|
template <class T>
|
|
[[nodiscard]] constexpr T pcg_uint(T x) noexcept
|
|
{
|
|
static_assert(std::is_integral<T>::value && std::is_unsigned<T>::value);
|
|
static_assert(sizeof(T) <= 8);
|
|
|
|
x = x * pcg_multiplier<T> + pcg_increment<T>;
|
|
x = (x ^ (x >> ((x >> ((sizeof(T) * 8) - (sizeof(T) + 1))) + (sizeof(T) + 1)))) * mcg_multiplier<T>;
|
|
return x ^ (x >> ((sizeof(T) * 16 + 2) / 3));
|
|
}
|
|
|
|
/// @private
|
|
template <class T>
|
|
[[nodiscard]] inline constexpr vector<T, 1> pcg_uvec1(vector<T, 1> x) noexcept
|
|
{
|
|
static_assert(std::is_integral<T>::value && std::is_unsigned<T>::value);
|
|
static_assert(sizeof(T) <= 8);
|
|
|
|
x[0] = T(x[0]);
|
|
|
|
return x;
|
|
}
|
|
|
|
/// @private
|
|
template <class T>
|
|
[[nodiscard]] constexpr vector<T, 2> pcg_uvec2(vector<T, 2> x) noexcept
|
|
{
|
|
static_assert(std::is_integral<T>::value && std::is_unsigned<T>::value);
|
|
static_assert(sizeof(T) <= 8);
|
|
|
|
x = x * pcg_multiplier<T> + pcg_increment<T>;
|
|
|
|
x[0] += x[1] * pcg_multiplier<T>;
|
|
x[1] += x[0] * pcg_multiplier<T>;
|
|
|
|
x[0] ^= x[0] >> (sizeof(T) * 4);
|
|
x[1] ^= x[1] >> (sizeof(T) * 4);
|
|
|
|
x[0] += x[1] * pcg_multiplier<T>;
|
|
x[1] += x[0] * pcg_multiplier<T>;
|
|
|
|
x[0] ^= x[0] >> (sizeof(T) * 4);
|
|
x[1] ^= x[1] >> (sizeof(T) * 4);
|
|
|
|
return x;
|
|
}
|
|
|
|
/// @private
|
|
template <class T>
|
|
[[nodiscard]] constexpr vector<T, 3> pcg_uvec3(vector<T, 3> x) noexcept
|
|
{
|
|
static_assert(std::is_integral<T>::value && std::is_unsigned<T>::value);
|
|
static_assert(sizeof(T) <= 8);
|
|
|
|
x = x * pcg_multiplier<T> + pcg_increment<T>;
|
|
|
|
x[0] += x[1] * x[2];
|
|
x[1] += x[2] * x[0];
|
|
x[2] += x[0] * x[1];
|
|
|
|
x[0] ^= x[0] >> (sizeof(T) * 4);
|
|
x[1] ^= x[1] >> (sizeof(T) * 4);
|
|
x[2] ^= x[2] >> (sizeof(T) * 4);
|
|
|
|
x[0] += x[1] * x[2];
|
|
x[1] += x[2] * x[0];
|
|
x[2] += x[0] * x[1];
|
|
|
|
return x;
|
|
}
|
|
|
|
/// @private
|
|
template <class T>
|
|
[[nodiscard]] constexpr vector<T, 4> pcg_uvec4(vector<T, 4> x) noexcept
|
|
{
|
|
static_assert(std::is_integral<T>::value && std::is_unsigned<T>::value);
|
|
static_assert(sizeof(T) <= 8);
|
|
|
|
x = x * pcg_multiplier<T> + pcg_increment<T>;
|
|
|
|
x[0] += x[1] * x[3];
|
|
x[1] += x[2] * x[0];
|
|
x[2] += x[0] * x[1];
|
|
x[3] += x[1] * x[2];
|
|
|
|
x[0] ^= x[0] >> (sizeof(T) * 4);
|
|
x[1] ^= x[1] >> (sizeof(T) * 4);
|
|
x[2] ^= x[2] >> (sizeof(T) * 4);
|
|
x[3] ^= x[3] >> (sizeof(T) * 4);
|
|
|
|
x[0] += x[1] * x[3];
|
|
x[1] += x[2] * x[0];
|
|
x[2] += x[0] * x[1];
|
|
x[3] += x[1] * x[2];
|
|
|
|
return x;
|
|
}
|
|
|
|
/**
|
|
* PCG hash function.
|
|
*
|
|
* @param x Input value.
|
|
*
|
|
* @return Unsigned pseudorandom output value.
|
|
*
|
|
* @warning Floating point and signed input values will be converted to unsigned integers via `static_cast`.
|
|
* @warning Vectors with more than 4 elements are not supported.
|
|
*
|
|
* @see https://en.wikipedia.org/wiki/Permuted_congruential_generator
|
|
* @see O'Neill, M.E. (2014). PCG : A Family of Simple Fast Space-Efficient Statistically Good Algorithms for Random Number Generation.
|
|
* @see Mark Jarzynski and Marc Olano, Hash Functions for GPU Rendering, Journal of Computer Graphics Techniques (JCGT), vol. 9, no. 3, 21-38, 2020.
|
|
*/
|
|
/// @{
|
|
[[nodiscard]] inline constexpr std::uint8_t pcg(std::uint8_t x) noexcept
|
|
{
|
|
return pcg_uint<std::uint8_t>(x);
|
|
}
|
|
|
|
[[nodiscard]] inline constexpr std::uint16_t pcg(std::uint16_t x) noexcept
|
|
{
|
|
return pcg_uint<std::uint16_t>(x);
|
|
}
|
|
|
|
[[nodiscard]] inline constexpr std::uint32_t pcg(std::uint32_t x) noexcept
|
|
{
|
|
return pcg_uint<std::uint32_t>(x);
|
|
}
|
|
|
|
[[nodiscard]] inline constexpr std::uint64_t pcg(std::uint64_t x) noexcept
|
|
{
|
|
return pcg_uint<std::uint64_t>(x);
|
|
}
|
|
|
|
[[nodiscard]] inline constexpr std::uint8_t pcg(std::int8_t x) noexcept
|
|
{
|
|
return pcg_uint<std::uint8_t>(static_cast<std::uint8_t>(x));
|
|
}
|
|
|
|
[[nodiscard]] inline constexpr std::uint16_t pcg(std::int16_t x) noexcept
|
|
{
|
|
return pcg_uint<std::uint16_t>(static_cast<std::uint16_t>(x));
|
|
}
|
|
|
|
[[nodiscard]] inline constexpr std::uint32_t pcg(std::int32_t x) noexcept
|
|
{
|
|
return pcg_uint<std::uint32_t>(static_cast<std::uint32_t>(x));
|
|
}
|
|
|
|
[[nodiscard]] inline constexpr std::uint64_t pcg(std::int64_t x) noexcept
|
|
{
|
|
return pcg_uint<std::uint64_t>(static_cast<std::uint64_t>(x));
|
|
}
|
|
|
|
[[nodiscard]] inline constexpr std::uint32_t pcg(float x) noexcept
|
|
{
|
|
return pcg_uint<std::uint32_t>(static_cast<std::uint32_t>(x));
|
|
}
|
|
|
|
[[nodiscard]] inline constexpr std::uint64_t pcg(double x) noexcept
|
|
{
|
|
return pcg_uint<std::uint64_t>(static_cast<std::uint64_t>(x));
|
|
}
|
|
|
|
template <class T, std::size_t N>
|
|
[[nodiscard]] inline constexpr vector<make_uint_t<T>, N> pcg(const vector<T, N>& x) noexcept
|
|
{
|
|
static_assert(N > 0 && N < 5, "PCG hash only supports vectors with 1-4 elements.");
|
|
|
|
if constexpr (N == 1)
|
|
return pcg_uvec1<make_uint_t<T>>(vector<make_uint_t<T>, N>(x));
|
|
else if constexpr (N == 2)
|
|
return pcg_uvec2<make_uint_t<T>>(vector<make_uint_t<T>, N>(x));
|
|
else if constexpr (N == 3)
|
|
return pcg_uvec3<make_uint_t<T>>(vector<make_uint_t<T>, N>(x));
|
|
else
|
|
return pcg_uvec4<make_uint_t<T>>(vector<make_uint_t<T>, N>(x));
|
|
}
|
|
/// @}
|
|
|
|
} // namespace hash
|
|
} // namespace math
|
|
|
|
#endif // ANTKEEPER_MATH_HASH_PCG_HPP
|