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random: modernize XoRoShiRo128PlusPlus a bit

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Make use of C++20 functions in XoRoShiRo128PlusPlus.
This commit is contained in:
Pieter Wuille 2024-03-10 14:29:28 -04:00
parent ddb7d26cfd
commit 8924f5120f
1 changed files with 9 additions and 17 deletions
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26
src/test/util/xoroshiro128plusplus.h
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@ -5,6 +5,7 @@
#ifndef BITCOIN_TEST_UTIL_XOROSHIRO128PLUSPLUS_H #ifndef BITCOIN_TEST_UTIL_XOROSHIRO128PLUSPLUS_H
#define BITCOIN_TEST_UTIL_XOROSHIRO128PLUSPLUS_H #define BITCOIN_TEST_UTIL_XOROSHIRO128PLUSPLUS_H
#include <bit>
#include <cstdint> #include <cstdint>
#include <limits> #include <limits>
@ -21,26 +22,19 @@ class XoRoShiRo128PlusPlus
uint64_t m_s0; uint64_t m_s0;
uint64_t m_s1; uint64_t m_s1;
[[nodiscard]] constexpr static uint64_t rotl(uint64_t x, int n)
{
return (x << n) | (x >> (64 - n));
}
[[nodiscard]] constexpr static uint64_t SplitMix64(uint64_t& seedval) noexcept [[nodiscard]] constexpr static uint64_t SplitMix64(uint64_t& seedval) noexcept
{ {
uint64_t z = (seedval += UINT64_C(0x9e3779b97f4a7c15)); uint64_t z = (seedval += 0x9e3779b97f4a7c15);
z = (z ^ (z >> 30U)) * UINT64_C(0xbf58476d1ce4e5b9); z = (z ^ (z >> 30)) * 0xbf58476d1ce4e5b9;
z = (z ^ (z >> 27U)) * UINT64_C(0x94d049bb133111eb); z = (z ^ (z >> 27)) * 0x94d049bb133111eb;
return z ^ (z >> 31U); return z ^ (z >> 31);
} }
public: public:
using result_type = uint64_t; using result_type = uint64_t;
constexpr explicit XoRoShiRo128PlusPlus(uint64_t seedval) noexcept constexpr explicit XoRoShiRo128PlusPlus(uint64_t seedval) noexcept
: m_s0(SplitMix64(seedval)), m_s1(SplitMix64(seedval)) : m_s0(SplitMix64(seedval)), m_s1(SplitMix64(seedval)) {}
{
}
// no copy - that is dangerous, we don't want accidentally copy the RNG and then have two streams // no copy - that is dangerous, we don't want accidentally copy the RNG and then have two streams
// with exactly the same results. If you need a copy, call copy(). // with exactly the same results. If you need a copy, call copy().
@ -51,15 +45,13 @@ public:
XoRoShiRo128PlusPlus(XoRoShiRo128PlusPlus&&) = default; XoRoShiRo128PlusPlus(XoRoShiRo128PlusPlus&&) = default;
XoRoShiRo128PlusPlus& operator=(XoRoShiRo128PlusPlus&&) = default; XoRoShiRo128PlusPlus& operator=(XoRoShiRo128PlusPlus&&) = default;
~XoRoShiRo128PlusPlus() = default;
constexpr result_type operator()() noexcept constexpr result_type operator()() noexcept
{ {
uint64_t s0 = m_s0, s1 = m_s1; uint64_t s0 = m_s0, s1 = m_s1;
const uint64_t result = rotl(s0 + s1, 17) + s0; const uint64_t result = std::rotl(s0 + s1, 17) + s0;
s1 ^= s0; s1 ^= s0;
m_s0 = rotl(s0, 49) ^ s1 ^ (s1 << 21); m_s0 = std::rotl(s0, 49) ^ s1 ^ (s1 << 21);
m_s1 = rotl(s1, 28); m_s1 = std::rotl(s1, 28);
return result; return result;
} }