32-bit PRNG (xorshift/xorwow) More...

#include "cgul_common.h"
#include "cgul_exception.h"
#include "cgul_int.h"

Include dependency graph for cgul_random_xorwow32.h:

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Typedefs
typedef typedefCGUL_BEGIN_C struct cgul_random_xorwow32 *	cgul_random_xorwow32_t

Functions
CGUL_EXPORT cgul_random_xorwow32_t	cgul_random_xorwow32__new (cgul_exception_t *cex)

CGUL_EXPORT cgul_random_xorwow32_t	cgul_random_xorwow32__new_from_seed (cgul_exception_t *cex, cgul_uint32_t seed)

CGUL_EXPORT cgul_random_xorwow32_t	cgul_random_xorwow32__new_from_seed_array (cgul_exception_t cex, cgul_uint32_t seeds)

CGUL_EXPORT void	cgul_random_xorwow32__delete (cgul_random_xorwow32_t r)

CGUL_EXPORT void	cgul_random_xorwow32__allocate_seed_array (cgul_exception_t cex, cgul_uint32_t v, unsigned int v_count)

CGUL_EXPORT cgul_uint32_t	cgul_random_xorwow32__next (cgul_exception_t *cex, cgul_random_xorwow32_t r)

CGUL_EXPORT cgul_uint32_t	cgul_random_xorwow32__next_in_range (cgul_exception_t *cex, cgul_random_xorwow32_t r, cgul_uint32_t range_max)

CGUL_EXPORT double	cgul_random_xorwow32__next_in_unit (cgul_exception_t *cex, cgul_random_xorwow32_t r)

Detailed Description

32-bit xorshift pseudo-random number generator. This PRNG has a period of (2^192 - 2^32). It is fast and only requires 20 bytes of state information. It is a good choice if cgul_random_cmwc32 cannot be used for some reason. One compelling reason for using this PRNG is that it is easier to seed because it has less state information than most of the other PRNGs. It gets its name from the xorwow() function in the following paper describing xorshift PRNGs:

    http://www.jstatsoft.org/v08/i14/paper

Author: Paul Serice

Typedef Documentation

§ cgul_random_xorwow32_t

typedef typedefCGUL_BEGIN_C struct cgul_random_xorwow32* cgul_random_xorwow32_t

Opaque pointer to a cgul_random_xorwow32 instance.

Function Documentation

§ cgul_random_xorwow32__new()

CGUL_EXPORT cgul_random_xorwow32_t cgul_random_xorwow32__new ( cgul_exception_t * cex )

This is a convenience function that creates a new cgul_random_xorwow32 object seeding it with the value returned by time(), i.e., the 32-bit seconds since the epoch. The caller is responsible for freeing the object by calling cgul_random_xorwow32__delete(). If memory cannot be allocated, NULL is returned, and an exception is thrown.

Parameters

[in,out] cex c-style exception

Returns: new cgul_random_xorwow32 instance

See also: cgul_random_xorwow32__new_from_seed(); cgul_random_xorwow32__new_from_seed_array()

Referenced by cgul_random_xorwow32_cxx::cgul_random_xorwow32_cxx().

§ cgul_random_xorwow32__new_from_seed()

CGUL_EXPORT cgul_random_xorwow32_t cgul_random_xorwow32__new_from_seed	(	cgul_exception_t *	cex,
		cgul_uint32_t	seed
	)

This is a convenience function that creates a new cgul_random_xorwow32 object seeding it with seed. The caller is responsible for freeing the object by calling cgul_random_xorwow32__delete(). If memory cannot be allocated, NULL is returned, and an exception is thrown.

Parameters

[in,out]	cex	c-style exception
[in]	seed	seed value

Returns: new cgul_random_xorwow32 instance

See also: cgul_random_xorwow32__new_from_seed_array()

Referenced by cgul_random_xorwow32_cxx::cgul_random_xorwow32_cxx().

§ cgul_random_xorwow32__new_from_seed_array()

CGUL_EXPORT cgul_random_xorwow32_t cgul_random_xorwow32__new_from_seed_array	(	cgul_exception_t *	cex,
		cgul_uint32_t *	seeds
	)

This is the correct way to create a new cgul_random_xorwow32 object by seeding it with the seeds array. It can be difficult, however, to acquire the requisite entropy to fill the entire array. The caller is responsible for freeing the object by calling cgul_random_xorwow32__delete(). If memory cannot be allocated or if all the seed values are zero, NULL is returned, and an exception is thrown.

The caller is responsible for making sure seeds has the correct number of elements. The easiest way to do this is by using cgul_random_xorwow32__allocate_seed_array() to allocate the array and get its size.

Parameters

[in,out]	cex	c-style exception
[in]	seeds	array of 32-bit values used to seed the PRNG

Returns: new cgul_random_xorwow32 instance

See also: cgul_random_xorwow32__allocate_seed_array()

Referenced by cgul_random_xorwow32_cxx::cgul_random_xorwow32_cxx().

§ cgul_random_xorwow32__delete()

CGUL_EXPORT void cgul_random_xorwow32__delete ( cgul_random_xorwow32_t r )

This method frees all internally allocated memory. Do not attempt to dereference r after calling this method.

Parameters

[in] r cgul_random_xorwow32 instance

Referenced by cgul_random_xorwow32_cxx::set_obj(), and cgul_random_xorwow32_cxx::~cgul_random_xorwow32_cxx().

§ cgul_random_xorwow32__allocate_seed_array()

CGUL_EXPORT void cgul_random_xorwow32__allocate_seed_array	(	cgul_exception_t *	cex,
		cgul_uint32_t **	v,
		unsigned int *	v_count
	)

This function allocates and returns an array of 32-bit seed values v where each element of the array is initialized to zero. The total number of 32-bit seed values in the array is returned in v_count. The caller should fill the array with true random values and create a new PRNG seeded with the values by calling cgul_random_xorwow32__new_from_seed_array(). The caller is responsible for calling free(*v). If an error occurs, an exception is thrown.

Parameters

[in,out]	cex	c-style exception
[out]	v	uninitialized array of 32-bit seed values
[out]	v_count	count of the number of 32-bit values in `v`

Referenced by cgul_random_xorwow32_cxx::allocate_seed_array().

§ cgul_random_xorwow32__next()

CGUL_EXPORT cgul_uint32_t cgul_random_xorwow32__next	(	cgul_exception_t *	cex,
		cgul_random_xorwow32_t	r
	)

Return the next element in the pseudo-random number sequence. The random numbers returned are 32 bits wide and should have a period of (2^192 - 2^32).

Parameters

[in]	cex	c-style exception
[in]	r	`cgul_random_xorwow32` instance

Returns: next element in the random number sequence

See also: cgul_random_xorwow32__next_in_range(); cgul_random_xorwow32__next_in_unit()

Referenced by cgul_random_xorwow32_cxx::next().

§ cgul_random_xorwow32__next_in_range()

CGUL_EXPORT cgul_uint32_t cgul_random_xorwow32__next_in_range	(	cgul_exception_t *	cex,
		cgul_random_xorwow32_t	r,
		cgul_uint32_t	range_max
	)

If the value returned by cgul_random_xorwow32__next() is not the exact range that is needed, this method can limit the return value to [0, range_max). If range_max is zero, an exception is thrown.

This function should avoid the very small round off error associated with just scaling the value returned by cgul_random_xorwow32__next_in_unit(); however, this function is much slower.

Parameters

[in,out]	cex	c-style exception
[in]	r	`cgul_random_xorwow32` instance
[in]	range_max	exclusive limit on the maximum value returned

Returns: next element in the random number sequence

Referenced by cgul_random_xorwow32_cxx::next_in_range().

§ cgul_random_xorwow32__next_in_unit()

CGUL_EXPORT double cgul_random_xorwow32__next_in_unit	(	cgul_exception_t *	cex,
		cgul_random_xorwow32_t	r
	)

Return the next element in the pseudo-random number sequence as type double on the range [0 - 1).

Parameters

[in]	cex	c-style exception
[in]	r	`cgul_random_xorwow32` instance

Returns: next element in the random number sequence

Referenced by cgul_random_xorwow32_cxx::next_in_unit().

Typedefs

Functions

Detailed Description

Typedef Documentation

§ cgul_random_xorwow32_t

Function Documentation

§ cgul_random_xorwow32__new()

§ cgul_random_xorwow32__new_from_seed()

§ cgul_random_xorwow32__new_from_seed_array()

§ cgul_random_xorwow32__delete()

§ cgul_random_xorwow32__allocate_seed_array()

§ cgul_random_xorwow32__next()

§ cgul_random_xorwow32__next_in_range()

§ cgul_random_xorwow32__next_in_unit()