Package org.apache.commons.rng.sampling.distribution

Class FastLoadedDiceRollerDiscreteSampler.FLDRSampler

java.lang.Object

org.apache.commons.rng.sampling.distribution.FastLoadedDiceRollerDiscreteSampler

org.apache.commons.rng.sampling.distribution.FastLoadedDiceRollerDiscreteSampler.FLDRSampler

All Implemented Interfaces:

DiscreteSampler, SharedStateDiscreteSampler, SharedStateSampler<SharedStateDiscreteSampler>

Enclosing class:

FastLoadedDiceRollerDiscreteSampler

private static final class FastLoadedDiceRollerDiscreteSampler.FLDRSampler
extends FastLoadedDiceRollerDiscreteSampler

Class to implement the FLDR sample algorithm.

Field Summary

Fields

Modifier and Type	Field	Description
private int	booleanSource	Provides a bit source for booleans.
private static final int	EMPTY_BOOL_SOURCE	Empty boolean source.
private final int[]	h	Number of leaf nodes at each level.
private final int	k	Number of levels in the discrete distribution generating (DDG) tree.
private final int[]	lH	Stores the leaf node labels in increasing order.
private final int	n	Number of categories.
private final UniformRandomProvider	rng	Underlying source of randomness.

Constructor Summary

Constructors

Modifier	Constructor	Description
(package private)	FLDRSampler(UniformRandomProvider rng, int n, int k, int[] h, int[] lH)	Creates a sampler.
private	FLDRSampler(UniformRandomProvider rng, FastLoadedDiceRollerDiscreteSampler.FLDRSampler source)	Creates a copy with a new source of randomness.

Method Summary

Modifier and Type	Method	Description
private int	flip()	Provides a source of boolean bits.
int	sample()	Creates an int sample.
String	toString()
FastLoadedDiceRollerDiscreteSampler	withUniformRandomProvider(UniformRandomProvider rng)	Create a new instance of the sampler with the same underlying state using the given uniform random provider as the source of randomness.

Methods inherited from class org.apache.commons.rng.sampling.distribution.FastLoadedDiceRollerDiscreteSampler

checkArraySize, indexOfNonZero, of, of, of

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.apache.commons.rng.sampling.distribution.DiscreteSampler

samples, samples

Field Details

EMPTY_BOOL_SOURCE

private static final int EMPTY_BOOL_SOURCE

Empty boolean source. This is the location of the sign-bit after 31 right shifts on the boolean source.

See Also:

• Constant Field Values

rng

private final UniformRandomProvider rng

Underlying source of randomness.

n

private final int n

Number of categories.

k

private final int k

Number of levels in the discrete distribution generating (DDG) tree. Equal to ceil(log2(m)) where m is the sum of observations.

h

private final int[] h

Number of leaf nodes at each level.

lH

private final int[] lH

Stores the leaf node labels in increasing order. Named H in the FLDR paper.

booleanSource

private int booleanSource

Provides a bit source for booleans.

A cached value from a call to UniformRandomProvider.nextInt().

Only stores 31-bits when full as 1 bit has already been consumed. The sign bit is a flag that shifts down so the source eventually equals 1 when all bits are consumed and will trigger a refill.

Constructor Details

FLDRSampler

FLDRSampler(UniformRandomProvider rng,
 int n,
 int k,
 int[] h,
 int[] lH)

Creates a sampler.

The input parameters are not validated and must be correctly computed tables.

Parameters:

rng - Generator of uniformly distributed random numbers.

n - Number of categories

k - Number of levels in the discrete distribution generating (DDG) tree. Equal to ceil(log2(m)) where m is the sum of observations.

h - Number of leaf nodes at each level.

lH - Stores the leaf node labels in increasing order.

FLDRSampler

private FLDRSampler(UniformRandomProvider rng,
 FastLoadedDiceRollerDiscreteSampler.FLDRSampler source)

Creates a copy with a new source of randomness.

Parameters:

rng - Generator of uniformly distributed random numbers.

source - Source to copy.

Method Details

sample

public int sample()

Creates an int sample.

Returns:

a sample.

flip

private int flip()

Provides a source of boolean bits.

Note: This replicates the boolean cache functionality of o.a.c.rng.core.source32.IntProvider. The method has been simplified to return an int value rather than a boolean.

Returns:

the bit (0 or 1)

toString

public String toString()

Overrides:

toString in class Object

withUniformRandomProvider

public FastLoadedDiceRollerDiscreteSampler withUniformRandomProvider(UniformRandomProvider rng)

Create a new instance of the sampler with the same underlying state using the given uniform random provider as the source of randomness.

Specified by:

withUniformRandomProvider in interface SharedStateSampler<SharedStateDiscreteSampler>

Specified by:

withUniformRandomProvider in class FastLoadedDiceRollerDiscreteSampler

Parameters:

rng - Generator of uniformly distributed random numbers.

Returns:

the sampler