ppforest2::stats::Uniform Class Reference

Discrete uniform random integer generator over [min, max]. More...

#include <Uniform.hpp>

Public Member Functions
	Uniform (int min, int max)
	Construct a uniform integer generator over [min, max].
std::vector< int >	distinct (int count, RNG &rng)
	Sample without replacement from [min, max].
std::vector< int >	operator() (int count, RNG &rng) const
	Generate multiple uniform random integers (with replacement).
int	operator() (RNG &rng) const
	Generate a single uniform random integer in [min, max].

Detailed Description

Discrete uniform random integer generator over [min, max].

All random integers are produced via Lemire's nearly-divisionless method, which replaces the classical modulo reduction with a multiply-and-shift, falling back to rejection sampling only when needed to eliminate bias. This is both faster and provably unbiased.

The distinct() method builds on this by performing a Fisher-Yates (Knuth) shuffle to sample without replacement — the foundation of bootstrap sampling and random variable selection in forests.

Note

This class is used instead of std::uniform_int_distribution to guarantee identical output across compilers and platforms.

See also

https://arxiv.org/abs/1805.10941

Constructor & Destructor Documentation

Uniform()

ppforest2::stats::Uniform::Uniform	(	int	min,
		int	max )

Construct a uniform integer generator over [min, max].

Parameters

min	Inclusive lower bound (must be ≥ 0).
max	Inclusive upper bound (must be ≥ min).

Member Function Documentation

distinct()

std::vector< int > ppforest2::stats::Uniform::distinct	(	int	count,
		RNG &	rng )

Sample without replacement from [min, max].

Implements the Fisher-Yates (Knuth) shuffle: fills a vector with [min, max], shuffles it using gen_lemire() for each swap, and returns the first count elements. The result is a uniformly distributed subset of size count with no repeats.

This is the method used by vars::Uniform and bootstrap sampling, ensuring reproducible variable selection across platforms.

Parameters

count	Number of distinct integers to draw (≤ range size).
rng	Random number generator (pcg32).

Returns

Vector of count distinct integers from [min, max].

operator()() [1/2]

std::vector< int > ppforest2::stats::Uniform::operator()	(	int	count,
		RNG &	rng ) const

Generate multiple uniform random integers (with replacement).

Parameters

count	Number of samples to generate.
rng	Random number generator (pcg32).

Returns

Vector of count i.i.d. integers from [min, max].

operator()() [2/2]

int ppforest2::stats::Uniform::operator()

(

RNG &

rng

)

const

Generate a single uniform random integer in [min, max].

Parameters

rng	Random number generator (pcg32).

Returns

Uniformly distributed integer in [min, max].

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The documentation for this class was generated from the following file:

• core/src/stats/Uniform.hpp