Fast random numbers using a precomputed data table. More...

Inherits G3D::Random.

Classes
class	HemiUniformData
	Put the cosHemi and the uniform together so that when alternating between them we stay in cache. More...

class	SphereBitsData

Public Member Functions
	PrecomputedRandom (const HemiUniformData data1, const SphereBitsData data2, int dataSize, uint32 seed=0xF018A4D2)

	PrecomputedRandom (int dataSize, uint32 seed=0xF018A4D2)

	~PrecomputedRandom ()

virtual uint32	bits () override
	Each bit is random. More...

virtual void	cosHemi (float &x, float &y, float &z) override
	Returns 3D unit vectors distributed according to a cosine distribution about the z axis. More...

virtual void	cosPowHemi (const float k, float &x, float &y, float &z) override
	Returns 3D unit vectors distributed according to a cosine power distribution ( $\mbox{cos}^k \theta$ ) about the z-axis. More...

virtual void	cosSphere (float &x, float &y, float &z)
	Returns 3D unit vectors distributed according to a cosine distribution about the z-axis. More...

virtual float	gaussian (float mean, float variance)
	Normally distributed reals. More...

virtual void	hemi (float &x, float &y, float &z)
	Returns 3D unit vectors uniformly distributed on the hemisphere about the z-axis. More...

virtual int	integer (int min, int max)
	Uniform random integer on the range [min, max]. More...

virtual void	reset (uint32 seed=0xF018A4D2, bool threadsafe=true) override

virtual void	sphere (float &x, float &y, float &z) override
	Returns 3D unit vectors uniformly distributed on the sphere. More...

virtual float	uniform (float low, float high) override
	Uniform random float on the range [min, max]. More...

virtual float	uniform () override
	Uniform random float on the range [0, 1]. More...

Static Public Member Functions
static Random &	common ()
	A shared instance for when the performance and features but not consistency of the class are desired. More...

static Random &	threadCommon ()
	Returns a non-threadsafe Random instance initialized with a thread-ID based seed for the current thread. More...

Protected Types
enum	{ N = 624, M = 397, R = 31, U = 11, S = 7, T = 15, L = 18, A = 0x9908B0DF, B = 0x9D2C5680, C = 0xEFC60000 }
	Constants (important for the algorithm; do not modify) More...

Protected Member Functions
virtual void	generate ()
	Generate the next N ints, and store them for readback later. More...

Protected Attributes
int	index
	Index into state. More...

Spinlock	lock
	Prevents multiple overlapping calls to generate(). More...

bool	m_freeData
	If true, free m_hemiUniform and m_sphereBits in destructor. More...

const HemiUniformData *	m_hemiUniform
	Array of 2^n elements. More...

int	m_index

int	m_modMask
	2^n - 1; the AND mask for computing a fast modulo More...

const SphereBitsData *	m_sphereBits

bool	m_threadsafe

uint32 *	state
	State vector (these are the next N values that will be returned) More...

Detailed Description

Fast random numbers using a precomputed data table.

e.g., generates cosHemi about 13x faster than Random. This is useful for quickly generating seeded random numbers for reproducibility. G3D::Random takes a long time to seed; this is instantaneous (providing the precomputed data is already available.)

Not threadsafe.

Member Enumeration Documentation

◆ anonymous enum

anonymous enum

protectedinherited

Constants (important for the algorithm; do not modify)

Enumerator
N
M
R
U
S
T
L
A
B
C

Constructor & Destructor Documentation

◆ PrecomputedRandom() [1/2]

G3D::PrecomputedRandom::PrecomputedRandom	(	const HemiUniformData *	data1,
		const SphereBitsData *	data2,
		int	dataSize,
		uint32	seed = `0xF018A4D2`
	)

◆ PrecomputedRandom() [2/2]

G3D::PrecomputedRandom::PrecomputedRandom	(	int	dataSize,
		uint32	seed = `0xF018A4D2`
	)

Parameters

dataSize Number of random numbers that can be requested before periodicity. Must be a power of 2.

◆ ~PrecomputedRandom()

G3D::PrecomputedRandom::~PrecomputedRandom ( )

Member Function Documentation

◆ bits()

virtual uint32 G3D::PrecomputedRandom::bits ( )

overridevirtual

Each bit is random.

Subclasses can choose to override just this method and the other methods will all work automatically.

Reimplemented from G3D::Random.

◆ common()

static Random& G3D::Random::common ( )

staticinherited

A shared instance for when the performance and features but not consistency of the class are desired.

It is slightly (10%) faster to use a distinct instance than to use the common one.

Threadsafe.

Referenced by G3D::Array< G3D::AABox >::randomElement(), and G3D::Array< G3D::AABox >::randomize().

◆ cosHemi()

virtual void G3D::PrecomputedRandom::cosHemi	(	float &	x,
		float &	y,
		float &	z
	)

overridevirtual

Returns 3D unit vectors distributed according to a cosine distribution about the z axis.

Reimplemented from G3D::Random.

◆ cosPowHemi()

virtual void G3D::PrecomputedRandom::cosPowHemi	(	const float	k,
		float &	x,
		float &	y,
		float &	z
	)

overridevirtual

Returns 3D unit vectors distributed according to a cosine power distribution ( $\mbox{cos}^k \theta$ ) about the z-axis.

Reimplemented from G3D::Random.

◆ cosSphere()

virtual void G3D::Random::cosSphere	(	float &	x,
		float &	y,
		float &	z
	)

virtualinherited

Returns 3D unit vectors distributed according to a cosine distribution about the z-axis.

◆ gaussian()

virtual float G3D::Random::gaussian	(	float	mean,
		float	variance
	)

virtualinherited

Normally distributed reals.

◆ generate()

virtual void G3D::Random::generate ( )

protectedvirtualinherited

Generate the next N ints, and store them for readback later.

Called from bits()

◆ hemi()

virtual void G3D::Random::hemi	(	float &	x,
		float &	y,
		float &	z
	)

virtualinherited

Returns 3D unit vectors uniformly distributed on the hemisphere about the z-axis.

◆ integer()

virtual int G3D::Random::integer	(	int	min,
		int	max
	)

virtualinherited

Uniform random integer on the range [min, max].

Referenced by G3D::Array< G3D::AABox >::randomElement(), and G3D::Array< G3D::AABox >::randomize().

◆ reset()

virtual void G3D::PrecomputedRandom::reset	(	uint32	seed = `0xF018A4D2`,
		bool	threadsafe = `true`
	)

overridevirtual

Reimplemented from G3D::Random.

◆ sphere()

virtual void G3D::PrecomputedRandom::sphere	(	float &	x,
		float &	y,
		float &	z
	)

overridevirtual

Returns 3D unit vectors uniformly distributed on the sphere.

Reimplemented from G3D::Random.

◆ threadCommon()

static Random& G3D::Random::threadCommon ( )

staticinherited

Returns a non-threadsafe Random instance initialized with a thread-ID based seed for the current thread.

This will always return the same instance for the same thread. Calling this repeatedly with too many threads will consume resources.

Useful for efficiently and safely producing random numbers with Thread::runConcurrently.

◆ uniform() [1/2]

virtual float G3D::PrecomputedRandom::uniform	(	float	low,
		float	high
	)

overridevirtual

Uniform random float on the range [min, max].

Reimplemented from G3D::Random.

◆ uniform() [2/2]

virtual float G3D::PrecomputedRandom::uniform ( )

overridevirtual

Uniform random float on the range [0, 1].

Reimplemented from G3D::Random.

Member Data Documentation

◆ index

int G3D::Random::index

protectedinherited

Index into state.

◆ lock

Spinlock G3D::Random::lock

protectedinherited

Prevents multiple overlapping calls to generate().

◆ m_freeData

bool G3D::PrecomputedRandom::m_freeData

protected

If true, free m_hemiUniform and m_sphereBits in destructor.

◆ m_hemiUniform

const HemiUniformData* G3D::PrecomputedRandom::m_hemiUniform

protected

Array of 2^n elements.

◆ m_index

int G3D::PrecomputedRandom::m_index

protected

◆ m_modMask

int G3D::PrecomputedRandom::m_modMask

protected

2^n - 1; the AND mask for computing a fast modulo

◆ m_sphereBits

const SphereBitsData* G3D::PrecomputedRandom::m_sphereBits

protected

◆ m_threadsafe

bool G3D::Random::m_threadsafe

protectedinherited

◆ state

uint32* G3D::Random::state

protectedinherited

State vector (these are the next N values that will be returned)

Classes

Public Member Functions

Static Public Member Functions

Protected Types

Protected Member Functions

Protected Attributes

Detailed Description

Member Enumeration Documentation

◆ anonymous enum

Constructor & Destructor Documentation

◆ PrecomputedRandom() [1/2]

◆ PrecomputedRandom() [2/2]

◆ ~PrecomputedRandom()

Member Function Documentation

◆ bits()

◆ common()

◆ cosHemi()

◆ cosPowHemi()

◆ cosSphere()

◆ gaussian()

◆ generate()

◆ hemi()

◆ integer()

◆ reset()

◆ sphere()

◆ threadCommon()

◆ uniform() [1/2]

◆ uniform() [2/2]

Member Data Documentation

◆ index

◆ lock

◆ m_freeData

◆ m_hemiUniform

◆ m_index

◆ m_modMask

◆ m_sphereBits

◆ m_threadsafe

◆ state