Random

Data Structures
struct	bj_pcg32_t

Macros
#define	BJ_RAND_MAX   0x7FFF
#define	bj_uniform_real_distribution   bj_uniform_float_distribution
#define	bj_normal_real_distribution   bj_normal_float_distribution

Typedefs
typedef struct bj_pcg32_t	bj_pcg32
typedef uint32_t(*	bj_random_u32_fn_t) (void *state)

Functions
void	bj_srand (unsigned int seed)
int	bj_rand (void)
void	bj_seed_pcg32 (bj_pcg32 *generator, uint64_t seed, uint64_t seq)
uint32_t	bj_next_pcg32 (bj_pcg32 *generator)
void	bj_discard_pcg32 (bj_pcg32 *generator, uint64_t z)
uint32_t	bj_min_pcg32 (void)
uint32_t	bj_max_pcg32 (void)
static uint32_t	bj_pcg32_generator (void *state)
int32_t	bj_uniform_int32_distribution (bj_random_u32_fn_t next, void *state, int32_t low, int32_t high)
float	bj_uniform_float_distribution (bj_random_u32_fn_t next, void *state, float low, float high)
double	bj_uniform_double_distribution (bj_random_u32_fn_t next, void *state, double low, double high)
long double	bj_uniform_long_double_distribution (bj_random_u32_fn_t next, void *state, long double low, long double high)
int	bj_bernoulli_distribution (bj_random_u32_fn_t next, void *state, bj_real probability)
float	bj_normal_float_distribution (bj_random_u32_fn_t next, void *state, float mean, float standard_deviation)
double	bj_normal_double_distribution (bj_random_u32_fn_t next, void *state, double mean, double standard_deviation)
long double	bj_normal_long_double_distribution (bj_random_u32_fn_t next, void *state, long double mean, long double standard_deviation)

Detailed Description

Random number generation utilities.

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Data Structure Documentation

bj_pcg32_t

struct bj_pcg32_t

PCG32 generator state.

Data Fields
uint64_t	inc	Stream selector; odd recommended, 0 allowed.
uint64_t	state	Current internal state (updated each step).

Macro Definition Documentation

bj_normal_real_distribution

#define bj_normal_real_distribution   bj_normal_float_distribution

Alias to the real-typed normal distribution for the active precision.

Maps to:

• bj_normal_long_double_distribution if BJ_API_LONG_DOUBLE
• bj_normal_double_distribution if BJ_API_FLOAT64
• bj_normal_float_distribution otherwise

BJ_RAND_MAX

#define BJ_RAND_MAX   0x7FFF

Maximum value returned by bj_rand().

Matches the stdlib idea of RAND_MAX. Values from bj_rand() are distributed in [0, BJ_RAND_MAX].

bj_uniform_real_distribution

#define bj_uniform_real_distribution   bj_uniform_float_distribution

Alias to the real-typed uniform distribution for the active precision.

Maps to:

• bj_uniform_long_double_distribution if BJ_API_LONG_DOUBLE
• bj_uniform_double_distribution if BJ_API_FLOAT64
• bj_uniform_float_distribution otherwise

Typedef Documentation

bj_pcg32

typedef struct bj_pcg32_t bj_pcg32

Alias for bj_pcg32_t.

bj_random_u32_fn_t

typedef uint32_t(* bj_random_u32_fn_t) (void *state)

RNG callback type for generator-agnostic distributions.

Parameters

state

Opaque engine state pointer.

Returns

Next 32-bit pseudo-random value.

Function Documentation

bj_bernoulli_distribution()

int bj_bernoulli_distribution	(	bj_random_u32_fn_t	next,
		void *	state,
		bj_real	probability )

Bernoulli(probability).

Parameters

next	RNG callback (e.g., bj_pcg32_generator).
state	Opaque engine state for next.
probability	Probability in [0,1].

Returns

1 with the given probability, else 0.

bj_discard_pcg32()

void bj_discard_pcg32	(	bj_pcg32 *	generator,
		uint64_t	z )

Advance the generator state by z steps.

Parameters

generator	Generator pointer (must not be NULL).
z	Number of steps to skip ahead.

bj_max_pcg32()

uint32_t bj_max_pcg32

(

void

)

Largest possible value returned by the generator.

Returns

Always 0xFFFFFFFF.

bj_min_pcg32()

uint32_t bj_min_pcg32

(

void

)

Smallest possible value returned by the generator.

Returns

Always 0.

bj_next_pcg32()

uint32_t bj_next_pcg32

(

bj_pcg32 *

generator

)

Advance the generator and return the next 32-bit value.

Parameters

generator

Generator pointer (must not be NULL).

Returns

Next 32-bit pseudo-random value.

bj_normal_double_distribution()

double bj_normal_double_distribution	(	bj_random_u32_fn_t	next,
		void *	state,
		double	mean,
		double	standard_deviation )

Normal double N(mean, standard_deviation^2).

Parameters

next	RNG callback (e.g., bj_pcg32_generator).
state	Opaque engine state for next.
mean	Mean.
standard_deviation	Standard deviation (>= 0).

Returns

double sample.

bj_normal_float_distribution()

float bj_normal_float_distribution	(	bj_random_u32_fn_t	next,
		void *	state,
		float	mean,
		float	standard_deviation )

Normal float N(mean, standard_deviation^2).

Parameters

next	RNG callback (e.g., bj_pcg32_generator).
state	Opaque engine state for next.
mean	Mean.
standard_deviation	Standard deviation (>= 0).

Returns

float sample.

bj_normal_long_double_distribution()

long double bj_normal_long_double_distribution	(	bj_random_u32_fn_t	next,
		void *	state,
		long double	mean,
		long double	standard_deviation )

Normal long double N(mean, standard_deviation^2).

Parameters

next	RNG callback (e.g., bj_pcg32_generator).
state	Opaque engine state for next.
mean	Mean.
standard_deviation	Standard deviation (>= 0).

Returns

long double sample.

bj_pcg32_generator()

uint32_t bj_pcg32_generator ( void * state )

inlinestatic

Adapter for distribution API (void* state).

Allows bj_pcg32 to be used with callbacks of type uint32_t (*)(void* state).

Parameters

state

Pointer to bj_pcg32.

Returns

Next 32-bit pseudo-random value.

bj_rand()

int bj_rand

(

void

)

Generate a pseudo-random integer in [0, BJ_RAND_MAX].

Linear congruential generator (LCG) using: X_{n+1} = (1103515245 * X_n + 12345) mod 2^31

Returns the high-order bits truncated to BJ_RAND_MAX range.

Returns

Integer in [0, BJ_RAND_MAX].

bj_seed_pcg32()

void bj_seed_pcg32	(	bj_pcg32 *	generator,
		uint64_t	seed,
		uint64_t	seq )

Set the generator state from seed and sequence.

Parameters

generator	Generator pointer (must not be NULL).
seed	Initial seed value.
seq	Stream selector (LSB forced to 1 internally).

bj_srand()

void bj_srand

(

unsigned int

seed

)

Seed the standard PRNG.

Parameters

seed	Seed value. Same seed reproduces the same sequence.

bj_uniform_double_distribution()

double bj_uniform_double_distribution	(	bj_random_u32_fn_t	next,
		void *	state,
		double	low,
		double	high )

Uniform double in [low, high).

Parameters

next	RNG callback (e.g., bj_pcg32_generator).
state	Opaque engine state for next.
low	Inclusive lower bound.
high	Exclusive upper bound.

Returns

double in [low, high).

bj_uniform_float_distribution()

float bj_uniform_float_distribution	(	bj_random_u32_fn_t	next,
		void *	state,
		float	low,
		float	high )

Uniform float in [low, high).

Parameters

next	RNG callback (e.g., bj_pcg32_generator).
state	Opaque engine state for next.
low	Inclusive lower bound.
high	Exclusive upper bound.

Returns

float in [low, high).

bj_uniform_int32_distribution()

int32_t bj_uniform_int32_distribution	(	bj_random_u32_fn_t	next,
		void *	state,
		int32_t	low,
		int32_t	high )

Uniform 32-bit integer in [low, high].

Parameters

next	RNG callback (e.g., bj_pcg32_generator).
state	Opaque engine state for next.
low	Inclusive lower bound.
high	Inclusive upper bound.

Returns

int32 in [low, high].

bj_uniform_long_double_distribution()

long double bj_uniform_long_double_distribution	(	bj_random_u32_fn_t	next,
		void *	state,
		long double	low,
		long double	high )

Uniform long double in [low, high).

Parameters

next	RNG callback (e.g., bj_pcg32_generator).
state	Opaque engine state for next.
low	Inclusive lower bound.
high	Exclusive upper bound.

Returns

long double in [low, high).