Introduction

prng_xoshiro is a constexpr-friendly pseudorandom number generator implementing the xoshiro256++ algorithm, designed by David Blackman and Sebastiano Vigna. It is intended for use in property-based tests that need reproducible pseudorandom sequences.

The generator satisfies the C++ UniformRandomBitGenerator named requirement, so it can be used with standard library distributions and algorithms that accept a URBG.

Usage

Basic Usage

Construct a generator with a seed and call it to produce 64-bit pseudorandom values:

auto rng = arene::base::testing::prng_xoshiro{std::uint64_t{42}};
 
auto const first = rng();
auto const second = rng();

Use With Standard Distributions

The generator satisfies UniformRandomBitGenerator, so it works with standard library distributions:

auto rng = arene::base::testing::prng_xoshiro{std::uint64_t{99}};
auto dist = std::uniform_int_distribution<int>{0, 100};
 
auto const value = dist(rng);

Use With Arene Base's Distributions

Arene Base also provides its own typed distributions which can be used in a similar way to the standard ones, with some additional features and limitations:

auto rng = arene::base::testing::prng_xoshiro{std::uint64_t{99}};
auto dist = arene::base::testing::bitwise_uniform_distribution<int>{};
 
auto const value = dist(rng);

See Typed Distributions for details on Arene Base's distributions.

Seeding

A single 64-bit seed is expanded into the full 256-bit internal state using the SplitMix64 generator. This ensures the internal state is never all-zero (the only disallowed state) for any seed value.

Different seeds produce different sequences. The same seed always produces the same sequence across all platforms.

Limitations

prng_xoshiro is not cryptographically secure. It must not be used for security-sensitive purposes.
This PRNG is currently limited to test code only.