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author | Martin Leitner-Ankerl <martin.ankerl@gmail.com> | 2022-06-10 08:49:35 +0200 |
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committer | Pieter Wuille <pieter@wuille.net> | 2023-01-30 18:12:21 -0500 |
commit | 5f05b27841af0bed1b6e7de5f46ffe33e5919e4d (patch) | |
tree | 63dc620d7d1c2e00eb61d37556ef39ea3cf5b8de /src/test/util/xoroshiro128plusplus.h | |
parent | 12ff72476ac0dbf8add736ad3fb5fad2eeab156c (diff) |
Add xoroshiro128++ PRNG
Xoroshiro128++ is a fast non-cryptographic random generator.
Reference implementation is available at https://prng.di.unimi.it/
Co-Authored-By: Pieter Wuille <pieter@wuille.net>
Diffstat (limited to 'src/test/util/xoroshiro128plusplus.h')
-rw-r--r-- | src/test/util/xoroshiro128plusplus.h | 71 |
1 files changed, 71 insertions, 0 deletions
diff --git a/src/test/util/xoroshiro128plusplus.h b/src/test/util/xoroshiro128plusplus.h new file mode 100644 index 0000000000..ac9f59b3f5 --- /dev/null +++ b/src/test/util/xoroshiro128plusplus.h @@ -0,0 +1,71 @@ +// Copyright (c) 2022 The Bitcoin Core developers +// Distributed under the MIT software license, see the accompanying +// file COPYING or http://www.opensource.org/licenses/mit-license.php. + +#ifndef BITCOIN_TEST_UTIL_XOROSHIRO128PLUSPLUS_H +#define BITCOIN_TEST_UTIL_XOROSHIRO128PLUSPLUS_H + +#include <cstdint> +#include <limits> + +/** xoroshiro128++ PRNG. Extremely fast, not appropriate for cryptographic purposes. + * + * Memory footprint is 128bit, period is 2^128 - 1. + * This class is not thread-safe. + * + * Reference implementation available at https://prng.di.unimi.it/xoroshiro128plusplus.c + * See https://prng.di.unimi.it/ + */ +class XoRoShiRo128PlusPlus +{ + uint64_t m_s0; + 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 + { + uint64_t z = (seedval += UINT64_C(0x9e3779b97f4a7c15)); + z = (z ^ (z >> 30U)) * UINT64_C(0xbf58476d1ce4e5b9); + z = (z ^ (z >> 27U)) * UINT64_C(0x94d049bb133111eb); + return z ^ (z >> 31U); + } + +public: + using result_type = uint64_t; + + constexpr explicit XoRoShiRo128PlusPlus(uint64_t seedval) noexcept + : 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 + // with exactly the same results. If you need a copy, call copy(). + XoRoShiRo128PlusPlus(const XoRoShiRo128PlusPlus&) = delete; + XoRoShiRo128PlusPlus& operator=(const XoRoShiRo128PlusPlus&) = delete; + + // allow moves + XoRoShiRo128PlusPlus(XoRoShiRo128PlusPlus&&) = default; + XoRoShiRo128PlusPlus& operator=(XoRoShiRo128PlusPlus&&) = default; + + ~XoRoShiRo128PlusPlus() = default; + + constexpr result_type operator()() noexcept + { + uint64_t s0 = m_s0, s1 = m_s1; + const uint64_t result = rotl(s0 + s1, 17) + s0; + s1 ^= s0; + m_s0 = rotl(s0, 49) ^ s1 ^ (s1 << 21); + m_s1 = rotl(s1, 28); + return result; + } + + static constexpr result_type min() noexcept { return std::numeric_limits<result_type>::min(); } + static constexpr result_type max() noexcept { return std::numeric_limits<result_type>::max(); } + static constexpr double entropy() noexcept { return 0.0; } +}; + +#endif // BITCOIN_TEST_UTIL_XOROSHIRO128PLUSPLUS_H |