Infinity::Engine::LognormalDistribution< RealType > Class Template Reference

Platform-independent lognormal distribution. More...

#include <PRNGDistribution.hpp>

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

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

Public Member Functions
	LognormalDistribution ()
	Default constructor. Creates Lognormal(0, 1) distribution.
	LognormalDistribution (RealType m, RealType s=RealType(1))
	Constructs a lognormal distribution with specified parameters.
	LognormalDistribution (const param_type &param)
	Constructs from a parameter set.
void	reset ()
	Resets the distribution state.
RealType	m () const
	Gets the mean parameter of underlying normal distribution.
RealType	s () const
	Gets the standard deviation parameter of underlying normal distribution.
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 (approaches 0).
result_type	max () const
	Gets the theoretical maximum value (positive infinity).
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 &p)
	Generates the next random value using provided parameters.

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

Detailed Description

template<typename RealType = double>
class Infinity::Engine::LognormalDistribution< RealType >

Platform-independent lognormal distribution.

Produces values according to a lognormal distribution, where the logarithm of the values follows a normal distribution. Useful for modeling multiplicative processes and values that are naturally positive and right-skewed.

If X ~ Lognormal(m, s), then log(X) ~ Normal(m, s). This makes the lognormal distribution ideal for modeling quantities that result from multiplicative random effects, such as particle sizes, income distributions, species abundance, or compound growth processes.

Template Parameters

RealType

Floating point type (float or double)

Example usage:

PRNG rng(12345);
 
// Parameters: m (underlying normal mean), s (underlying normal stddev)
LognormalDistribution<float> sizes(2.0f, 0.5f);
 
// Generate particle sizes (always positive)
for (int i = 0; i < 100; ++i) {
    float size = sizes(rng);  // Returns positive value with right-skewed distribution
}
 
// Model compound growth with variability
LognormalDistribution<double> growth_factor(0.0, 0.2);
double multiplier = growth_factor(rng);  // Median ~1.0, always positive

Note

All generated values are strictly positive (> 0).

The distribution is right-skewed with a long tail toward larger values.

For Lognormal(m, s): median = exp(m), mode = exp(m - s²)

Member Typedef Documentation

result_type

template<typename RealType = double>

using Infinity::Engine::LognormalDistribution< RealType >::result_type = RealType

The type of values produced by the distribution.

Constructor & Destructor Documentation

LognormalDistribution() [1/3]

template<typename RealType = double>

Infinity::Engine::LognormalDistribution< RealType >::LognormalDistribution ( )

inline

Default constructor. Creates Lognormal(0, 1) distribution.

LognormalDistribution() [2/3]

template<typename RealType = double>

Infinity::Engine::LognormalDistribution< RealType >::LognormalDistribution ( RealType  m, RealType  s = RealType(1)  )

inlineexplicit

Constructs a lognormal distribution with specified parameters.

Parameters

m	Mean of underlying normal distribution
s	Standard deviation of underlying normal distribution

LognormalDistribution() [3/3]

template<typename RealType = double>

Infinity::Engine::LognormalDistribution< RealType >::LognormalDistribution ( const param_type &  param )

inlineexplicit

Constructs from a parameter set.

Parameters

param

The distribution parameters

Member Function Documentation

m()

template<typename RealType = double>

RealType Infinity::Engine::LognormalDistribution< RealType >::m ( ) const

inline

Gets the mean parameter of underlying normal distribution.

max()

template<typename RealType = double>

result_type Infinity::Engine::LognormalDistribution< RealType >::max ( ) const

inline

Gets the theoretical maximum value (positive infinity).

min()

template<typename RealType = double>

result_type Infinity::Engine::LognormalDistribution< RealType >::min ( ) const

inline

Gets the minimum value that can be generated (approaches 0).

operator()() [1/2]

template<typename RealType = double>

template<typename Generator >

result_type Infinity::Engine::LognormalDistribution< RealType >::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 positive random value from the lognormal distribution

operator()() [2/2]

template<typename RealType = double>

template<typename Generator >

result_type Infinity::Engine::LognormalDistribution< RealType >::operator() ( Generator &  g, const param_type &  p  )

inline

Generates the next random value using provided parameters.

Generates a value from the lognormal distribution by drawing from a normal distribution and exponentiating the result.

Template Parameters

Generator

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

Parameters

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

Returns

A positive random value from Lognormal(p.m(), p.s())

param() [1/2]

template<typename RealType = double>

param_type Infinity::Engine::LognormalDistribution< RealType >::param ( ) const

inline

Gets the current parameter set.

param() [2/2]

template<typename RealType = double>

void Infinity::Engine::LognormalDistribution< RealType >::param ( const param_type &  param )

inline

Sets new parameters for the distribution.

reset()

template<typename RealType = double>

void Infinity::Engine::LognormalDistribution< RealType >::reset ( )

inline

Resets the distribution state.

Resets the underlying normal distribution, discarding any cached values.

s()

template<typename RealType = double>

RealType Infinity::Engine::LognormalDistribution< RealType >::s ( ) const

inline

Gets the standard deviation parameter of underlying normal distribution.

Friends And Related Symbol Documentation

operator!=

template<typename RealType = double>

bool operator!= ( const LognormalDistribution< RealType > &  lhs, const LognormalDistribution< RealType > &  rhs  )

friend

operator==

template<typename RealType = double>

bool operator== ( const LognormalDistribution< RealType > &  lhs, const LognormalDistribution< RealType > &  rhs  )

friend