Reproducible random-number support for stochastic CA rules (Phase 8). More...

#include <cstddef>
#include <cstdint>
#include <random>
#include <type_traits>
#include <ca-traits.H>

Include dependency graph for ca-rng.H:

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Classes
class	Aleph::CA::Per_Thread_RNG< Engine >
	Master seed dispenser for stochastic CA rules. More...

Namespaces
namespace	Aleph
	Main namespace for Aleph-w library functions.

namespace	Aleph::CA

Functions
constexpr std::uint64_t	Aleph::CA::splitmix64 (std::uint64_t x) noexcept
	64-bit SplitMix hash.

constexpr std::uint64_t	Aleph::CA::mix_seed (const std::uint64_t a, const std::uint64_t b) noexcept
	Combine two 64-bit values into a single deterministic hash.

template<std::size_t Rank>
constexpr std::uint64_t	Aleph::CA::cell_key_from_coord (const Coord_Vec< Rank > &c) noexcept
	Hash a cell coordinate into a stable 64-bit key.

template<std::size_t Rank>
constexpr std::uint64_t	Aleph::CA::cell_seed (const std::uint64_t master_seed, const std::size_t step, const Coord_Vec< Rank > &coord) noexcept
	Build a deterministic per-cell seed.

template<std::size_t Rank>
constexpr std::uint64_t	Aleph::CA::cell_seed (const std::uint64_t master_seed, const Cell_Context< Rank > &ctx) noexcept
	Build a deterministic per-cell seed from a `Cell_Context`.

constexpr std::uint64_t	Aleph::CA::thread_step_seed (const std::uint64_t master_seed, const std::size_t thread_id, const std::size_t step) noexcept
	Build a deterministic seed from `(master, thread_id, step)`.

template<typename Engine >
double	Aleph::CA::uniform_unit (Engine &eng)
	Map a 64-bit RNG output to a uniform value in `[0, 1)`.

template<typename Engine >
std::size_t	Aleph::CA::uniform_int (Engine &eng, const std::size_t lo, const std::size_t hi)
	Sample a uniform integer in `[lo, hi]` (inclusive).

Detailed Description

Reproducible random-number support for stochastic CA rules (Phase 8).

Provides:

splitmix64 / mix_seed — stateless 64-bit hashing primitives.
cell_key_from_coord<Rank>(coord) — deterministic 64-bit hash of a cell coordinate.
cell_seed(master, step, coord) — deterministic per-cell seed derived from (master_seed, step, coord). Same (master, step, coord) triple → same seed regardless of thread scheduling, partition layout or visiting order.
Per_Thread_RNG<Engine> — thin wrapper around a master seed that builds fresh PRNG instances on demand from (step, coord) or (thread_id, step) triples.
uniform_unit(eng) / uniform_int(eng, lo, hi) — small, portable distribution helpers that bypass std::uniform_real_distribution (whose bit pattern is implementation-defined and therefore unsuitable for bit-exact reproducibility across compilers).

All helpers live in Aleph::CA and are header-only.

Definition in file ca-rng.H.

Classes