Infinity::Engine::UniformIntDistribution< IntType > Class Template Reference

Platform-independent uniform integer distribution. More...

#include <PRNGDistribution.hpp>

Classes
struct	param_type
	Parameter set for the distribution. More...

Public Types
using	result_type = IntType
	The type of values produced by the distribution.

Public Member Functions
	UniformIntDistribution ()
	Default constructor. Creates a uniform distribution over [0, IntType::max()].
	UniformIntDistribution (IntType a, IntType b=std::numeric_limits< IntType >::max())
	Constructs a uniform distribution with specified bounds.
	UniformIntDistribution (const param_type &param)
	Constructs from a parameter set.
void	reset ()
	Resets the distribution state.
IntType	a () const
	Gets the lower bound of the distribution range.
IntType	b () const
	Gets the upper bound of the distribution range.
param_type	param () const
	Gets the current parameter set.
void	param (const param_type &param)
	Sets new parameters for the distribution.
result_type	min () const
	Gets the minimum value that can be generated (inclusive).
result_type	max () const
	Gets the maximum value that can be generated (inclusive).
template<typename Generator >
result_type	operator() (Generator &g)
	Generates the next random value using stored parameters.
template<typename Generator >
result_type	operator() (Generator &g, const param_type &param)
	Generates the next random value using provided parameters.

Friends
bool	operator== (const UniformIntDistribution &lhs, const UniformIntDistribution &rhs)
bool	operator!= (const UniformIntDistribution &lhs, const UniformIntDistribution &rhs)

Detailed Description

template<typename IntType = int>
class Infinity::Engine::UniformIntDistribution< IntType >

Platform-independent uniform integer distribution.

Produces integer values uniformly distributed over a specified range [a, b] (inclusive). Uses Lemire's algorithm for fast, unbiased bounded random integers, which is both faster and more portable than the rejection sampling used by some standard library implementations.

This implementation guarantees identical results across all platforms when given the same PRNG seed, making it ideal for procedural generation that must be reproducible across different systems.

Template Parameters

IntType

Integer type (signed or unsigned)

Example usage:

PRNG rng(12345);
UniformIntDistribution<int> dice(1, 6);
 
int roll = dice(rng);  // Random int from 1 to 6 inclusive
 
// Generate grid coordinates
UniformIntDistribution<int> coord_dist(0, 99);
int x = coord_dist(rng);
int y = coord_dist(rng);
 
// Works with unsigned types too
UniformIntDistribution<uint32_t> id_gen(1000, 9999);
uint32_t id = id_gen(rng);

Note

Both bounds are inclusive; values are in [a, b], not [a, b).

Lemire's algorithm ensures perfect uniformity even when the range doesn't divide evenly into the generator's period.

Member Typedef Documentation

result_type

template<typename IntType = int>

using Infinity::Engine::UniformIntDistribution< IntType >::result_type = IntType

The type of values produced by the distribution.

Constructor & Destructor Documentation

UniformIntDistribution() [1/3]

template<typename IntType = int>

Infinity::Engine::UniformIntDistribution< IntType >::UniformIntDistribution ( )

inline

Default constructor. Creates a uniform distribution over [0, IntType::max()].

UniformIntDistribution() [2/3]

template<typename IntType = int>

Infinity::Engine::UniformIntDistribution< IntType >::UniformIntDistribution ( IntType  a, IntType  b = std::numeric_limits<IntType>::max()  )

inlineexplicit

Constructs a uniform distribution with specified bounds.

Parameters

a	Lower bound (inclusive)
b	Upper bound (inclusive)

UniformIntDistribution() [3/3]

template<typename IntType = int>

Infinity::Engine::UniformIntDistribution< IntType >::UniformIntDistribution ( const param_type &  param )

inlineexplicit

Constructs from a parameter set.

Parameters

param

The distribution parameters

Member Function Documentation

a()

template<typename IntType = int>

IntType Infinity::Engine::UniformIntDistribution< IntType >::a ( ) const

inline

Gets the lower bound of the distribution range.

b()

template<typename IntType = int>

IntType Infinity::Engine::UniformIntDistribution< IntType >::b ( ) const

inline

Gets the upper bound of the distribution range.

max()

template<typename IntType = int>

result_type Infinity::Engine::UniformIntDistribution< IntType >::max ( ) const

inline

Gets the maximum value that can be generated (inclusive).

min()

template<typename IntType = int>

result_type Infinity::Engine::UniformIntDistribution< IntType >::min ( ) const

inline

Gets the minimum value that can be generated (inclusive).

operator()() [1/2]

template<typename IntType = int>

template<typename Generator >

result_type Infinity::Engine::UniformIntDistribution< IntType >::operator() ( Generator &  g )

inline

Generates the next random value using stored parameters.

Template Parameters

Generator

The random number generator type (e.g., PRNG)

Parameters

g	The random number generator

Returns

A random value uniformly distributed in [a, b] (inclusive)

operator()() [2/2]

template<typename IntType = int>

template<typename Generator >

result_type Infinity::Engine::UniformIntDistribution< IntType >::operator() ( Generator &  g, const param_type &  param  )

inline

Generates the next random value using provided parameters.

Uses Lemire's nearly divisionless algorithm for fast, unbiased random integers. This method is faster than rejection sampling and produces perfectly uniform results even when the range doesn't divide evenly into 2^32.

The algorithm works by:

1. Fast path for power-of-2 ranges using simple bit masking
2. General path using 64-bit multiplication and rejection sampling only when needed

Template Parameters

Generator

The random number generator type (e.g., PRNG)

Parameters

g	The random number generator
param	The distribution parameters to use for this generation

Returns

A random value uniformly distributed in [param.a(), param.b()] (inclusive)

param() [1/2]

template<typename IntType = int>

param_type Infinity::Engine::UniformIntDistribution< IntType >::param ( ) const

inline

Gets the current parameter set.

param() [2/2]

template<typename IntType = int>

void Infinity::Engine::UniformIntDistribution< IntType >::param ( const param_type &  param )

inline

Sets new parameters for the distribution.

reset()

template<typename IntType = int>

void Infinity::Engine::UniformIntDistribution< IntType >::reset ( )

inline

Resets the distribution state.

No-op for uniform distributions as they maintain no internal state between generations.

Friends And Related Symbol Documentation

operator!=

template<typename IntType = int>

bool operator!= ( const UniformIntDistribution< IntType > &  lhs, const UniformIntDistribution< IntType > &  rhs  )

friend

operator==

template<typename IntType = int>

bool operator== ( const UniformIntDistribution< IntType > &  lhs, const UniformIntDistribution< IntType > &  rhs  )

friend