syten::Random Namespace Reference

The random number generation engine generation subsystem. More...

Typedefs
using	Engine = std::mt19937_64
	The engine type returned by genEngine() below. More...
using	Result = typename Engine::result_type
	The type of the results generated by engines from genEngine() as well as the seed type used to initialise the engine-generation engine. More...

Functions
void	disableReproducible ()
	Sets the global seed to zero, causing non-reproducible generation of random number engines by genEngine(). More...
Engine	genEngine ()
	Returns a random number generation engine. More...
Result	genValue ()
	Generates a single value from the internal LCG, mainly useful for debugging. More...
Result const &	getSeed ()
	Returns the seed used by the internal LCG. More...
Result	initReproducible (Result const seed_=0)
	Initialises the global generating random number engine. More...
bool	isReproducible ()
	Returns true if the global seed is non-zero and no threading is used. More...

Variables
std::linear_congruential_engine< Result, 6364136223846793005ULL, 1442695040888963407ULL, 18446744073709551615ULL >	engine {std::random_device()()}
	Engine used to generate seeds for genEngine() below. More...
std::mutex	mtx_engine
	Mutex protecting genEngine (and engine) below if seed is non-zero. More...
Result	seed {0}
	global seed, if zero, none was set and genEngine() is non-deterministic More...

Detailed Description

The random number generation engine generation subsystem.

The idea is as follows:

• genEngine() creates a new random number generation engine of type Random::Engine.

If Random::seed is zero, it acquires a non-deterministic seed to initialise the engine it returns. If Random::seed is non-zero, it locks a mutex and uses the next result from a global random number generation engine to initialise the new engine. It then returns that new engine.

• Random:seed is initialised by a call to Random::initReproducible(), either by the argument to that call or from a non-deterministic hardware source. initReproducible() returns that seed.
• Random::isReproducible() returns true if the random subsystem is in a somewhat deterministic state right now. It cannot check what you did before or what you’re going to do later, only that
• a global seed is set, i.e. a global engine is generating the seeds for the individual engines returned by genEngine()
• and all Threading::*Num values are set to 1, i.e. no threading takes place.
• Random::disableReproducible() sets Random::seed to zero. Afterwards, non-deterministic random values will be used for initialisation of the engines returned by genEngine().