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// This file is part of AsmJit project <https://asmjit.com>
//
// See <asmjit/core.h> or LICENSE.md for license and copyright information
// SPDX-License-Identifier: Zlib
#ifndef TESTING_COMMONS_RANDOM_H_INCLUDED
#define TESTING_COMMONS_RANDOM_H_INCLUDED
#include <stdint.h>
#include <string.h>
namespace TestUtils {
namespace {
// A pseudo random number generator based on a paper by Sebastiano Vigna:
// http://vigna.di.unimi.it/ftp/papers/xorshiftplus.pdf
class Random {
public:
// Constants suggested as `23/18/5`.
static inline constexpr uint32_t kStep1_SHL = 23;
static inline constexpr uint32_t kStep2_SHR = 18;
static inline constexpr uint32_t kStep3_SHR = 5;
uint64_t _state[2];
inline explicit Random(uint64_t seed = 0) noexcept { reset(seed); }
inline Random(const Random& other) noexcept = default;
inline void reset(uint64_t seed = 0) noexcept {
// The number is arbitrary, it means nothing.
constexpr uint64_t kZeroSeed = 0x1F0A2BE71D163FA0u;
// Generate the state data by using splitmix64.
for (uint32_t i = 0; i < 2; i++) {
seed += 0x9E3779B97F4A7C15u;
uint64_t x = seed;
x = (x ^ (x >> 30)) * 0xBF58476D1CE4E5B9u;
x = (x ^ (x >> 27)) * 0x94D049BB133111EBu;
x = (x ^ (x >> 31));
_state[i] = x != 0 ? x : kZeroSeed;
}
}
inline uint32_t next_uint32() noexcept {
return uint32_t(next_uint64() >> 32);
}
inline uint64_t next_uint64() noexcept {
uint64_t x = _state[0];
uint64_t y = _state[1];
x ^= x << kStep1_SHL;
y ^= y >> kStep3_SHR;
x ^= x >> kStep2_SHR;
x ^= y;
_state[0] = y;
_state[1] = x;
return x + y;
}
inline double next_double() noexcept {
constexpr uint32_t kMantissaShift = 64 - 52;
constexpr uint64_t kExpMsk = 0x3FF0000000000000u;
uint64_t u = (next_uint64() >> kMantissaShift) | kExpMsk;
double d = 0.0;
memcpy(&d, &u, 8);
return d - 1.0;
}
};
} // {anonymous}
} // {TestUtils}
#endif // TESTING_COMMONS_RANDOM_H_INCLUDED
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