rng.hpp File Reference

The random engine every generator library uses: xoshiro256** seeded through SplitMix64, with labelled child streams. More...

#include <array>
#include <bit>
#include <cstdint>
#include <limits>
#include <random>
#include <string_view>

Go to the source code of this file.

Classes
class	dasmig::core::splitmix64
	The SplitMix64 generator (Steele, Lea and Flood 2014). More...
class	dasmig::core::rng
	The core random engine: xoshiro256** (Blackman and Vigna 2018). More...

Functions
constexpr std::uint64_t	dasmig::core::splitmix64_mix (std::uint64_t z) noexcept
	The SplitMix64 output function (a bijection on 64-bit values).
constexpr std::uint64_t	dasmig::core::fnv1a64 (std::string_view text) noexcept
	64-bit FNV-1a hash of the bytes of a string.
constexpr std::uint64_t	dasmig::core::hash_combine (std::uint64_t hash, std::uint64_t value) noexcept
	Combine a hash with another 64-bit value, order-sensitively.

Detailed Description

The random engine every generator library uses: xoshiro256** seeded through SplitMix64, with labelled child streams.

Author

Diego Dasso Migotto (diegomigotto at hotmail dot com)

The algorithms are fixed and the output is part of the core's contract: a seed gives the same sequence on every compiler and platform. Changing any of them is a major version change.

Definition in file rng.hpp.

Function Documentation

fnv1a64()

constexpr std::uint64_t dasmig::core::fnv1a64 ( std::string_view  text )

constexprnoexcept

64-bit FNV-1a hash of the bytes of a string.

Labels are hashed as bytes, so pass UTF-8: a std::wstring label would hash differently on Windows (UTF-16) and elsewhere (UTF-32).

Parameters

text	Bytes to hash.

Returns

The hash.

Definition at line 66 of file rng.hpp.

hash_combine()

constexpr std::uint64_t dasmig::core::hash_combine ( std::uint64_t  hash, std::uint64_t  value  )

constexprnoexcept

Combine a hash with another 64-bit value, order-sensitively.

splitmix64_mix(hash ^ splitmix64_mix(value)), the same construction as rng::child_seed().

Parameters

hash	Running hash.
value	Value to fold in.

Returns

The combined hash.

Definition at line 85 of file rng.hpp.

splitmix64_mix()

constexpr std::uint64_t dasmig::core::splitmix64_mix ( std::uint64_t  z )

constexprnoexcept

The SplitMix64 output function (a bijection on 64-bit values).

Parameters

z	Input value.

Returns

The mixed value.

Definition at line 29 of file rng.hpp.