Forest-fire rule (Drossel & Schwabl, 1992). More...

#include <tpl_ca_stochastic_rules.H>

Public Types
using	engine_type = Engine
	Underlying RNG engine type.

Public Member Functions
	Forest_Fire_Rule (const double p_growth, const double p_lightning, std::uint64_t master_seed=0)
	Build a forest-fire rule with the given probabilities.

double	p_growth () const noexcept

double	p_lightning () const noexcept

std::uint64_t	master_seed () const noexcept

void	set_master_seed (std::uint64_t s) noexcept
	Replace the master seed; takes effect on the next step.

template<typename State , std::size_t Rank>
State	operator() (const State &current, Neighbor_View< State > neighbours, const Cell_Context< Rank > &ctx) const
	Compute the next forest-fire state for cell `current`.

Private Attributes
double	p_growth_

double	p_lightning_

std::uint64_t	master_seed_

Detailed Description

template<typename Engine = std::mt19937_64>
class Aleph::CA::Forest_Fire_Rule< Engine >

Forest-fire rule (Drossel & Schwabl, 1992).

Transition (synchronous, neighbourhood-defined by the engine):

BURNING → EMPTY.
TREE → BURNING if at least one neighbour is BURNING, else BURNING with probability p_lightning, else stays TREE.
EMPTY → TREE with probability p_growth, else stays EMPTY.

Probabilities are sampled from a per-cell deterministic engine, so the trajectory only depends on master_seed, the initial frame and the chosen probabilities.

Template Parameters

Engine RNG engine; defaults to std::mt19937_64.

Definition at line 114 of file tpl_ca_stochastic_rules.H.

Member Typedef Documentation

◆ engine_type

template<typename Engine = std::mt19937_64>

using Aleph::CA::Forest_Fire_Rule< Engine >::engine_type = Engine

Underlying RNG engine type.

Definition at line 122 of file tpl_ca_stochastic_rules.H.

Constructor & Destructor Documentation

◆ Forest_Fire_Rule()

template<typename Engine = std::mt19937_64>

Aleph::CA::Forest_Fire_Rule< Engine >::Forest_Fire_Rule	(	const double	p_growth,
		const double	p_lightning,
		std::uint64_t	master_seed = `0`
	)

inline

Build a forest-fire rule with the given probabilities.

Parameters

[in]	p_growth	probability that an `EMPTY` cell grows a tree.
[in]	p_lightning	probability that a `TREE` ignites spontaneously when no neighbour is burning.
[in]	master_seed	master seed forwarded to `cell_seed()`.

Exceptions

std::domain_error if p_growth or p_lightning is not in [0, 1].

Definition at line 133 of file tpl_ca_stochastic_rules.H.

References ah_domain_error_if, Aleph::blossom_maximum_cardinality_matching(), Aleph::CA::Forest_Fire_Rule< Engine >::p_growth(), and Aleph::CA::Forest_Fire_Rule< Engine >::p_lightning().

Member Function Documentation

◆ master_seed()

template<typename Engine = std::mt19937_64>

std::uint64_t Aleph::CA::Forest_Fire_Rule< Engine >::master_seed ( ) const

inlinenoexcept

Returns: the master seed feeding the per-cell streams.

Definition at line 155 of file tpl_ca_stochastic_rules.H.

References Aleph::CA::Forest_Fire_Rule< Engine >::master_seed_.

◆ operator()()

template<typename Engine = std::mt19937_64>

template<typename State , std::size_t Rank>

State Aleph::CA::Forest_Fire_Rule< Engine >::operator()	(	const State &	current,
		Neighbor_View< State >	neighbours,
		const Cell_Context< Rank > &	ctx
	)		const