Class PcgXshRr32

java.lang.Object

org.apache.commons.rng.core.BaseProvider

org.apache.commons.rng.core.source32.IntProvider

org.apache.commons.rng.core.source32.PcgXshRr32

All Implemented Interfaces:

RandomIntSource, RestorableUniformRandomProvider, UniformRandomProvider

public class PcgXshRr32
extends IntProvider

A Permuted Congruential Generator (PCG) that is composed of a 64-bit Linear Congruential Generator (LCG) combined with the XSH-RR (xorshift; random rotate) output transformation to create 32-bit output.

State size is 128 bits and the period is 2⁶⁴.

Note: Although the seed size is 128 bits, only the first 64 are effective: in effect, two seeds that only differ by the last 64 bits may produce highly correlated sequences.

Since:

1.3

See Also:

• PCG, A Family of Better Random Number Generators

Constructor Summary

Constructors

Constructor	Description
PcgXshRr32(long[] seed)	Creates a new instance.
PcgXshRr32(Long seed)	Creates a new instance using a default increment.

Method Summary

Modifier and Type	Method	Description
protected byte[]	getStateInternal()	Creates a snapshot of the RNG state.
int	next()	Return the next random value.
protected void	setStateInternal(byte[] s)	Resets the RNG to the given state.
protected int	transform(long x)	Transform the 64-bit state of the generator to a 32-bit output.

Methods inherited from class IntProvider

nextBoolean, nextBytes, nextBytes, nextDouble, nextInt, nextLong, resetCachedState

Methods inherited from class BaseProvider

checkIndex, checkStateSize, composeStateInternal, extendSeed, extendSeed, fillState, fillState, restoreState, saveState, splitStateInternal, toString

Methods inherited from class Object

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

Methods inherited from interface UniformRandomProvider

doubles, doubles, doubles, doubles, ints, ints, ints, ints, longs, longs, longs, longs, nextDouble, nextDouble, nextFloat, nextFloat, nextFloat, nextInt, nextInt, nextLong, nextLong

Constructor Details

PcgXshRr32

public PcgXshRr32(Long seed)

Creates a new instance using a default increment.

Parameters:

seed - Initial state.

Since:

1.4

PcgXshRr32

public PcgXshRr32(long[] seed)

Creates a new instance.

Note: Although the seed size is 128 bits, only the first 64 are effective: in effect, two seeds that only differ by the last 64 bits may produce highly correlated sequences.

Parameters:

seed - Initial seed. If the length is larger than 2, only the first 2 elements will be used; if smaller, the remaining elements will be automatically set.

The 1st element is used to set the LCG state. The 2nd element is used to set the LCG increment; the most significant bit is discarded by left shift and the increment is set to odd.

Method Details

transform

protected int transform(long x)

Transform the 64-bit state of the generator to a 32-bit output. The transformation function shall vary with respect to different generators.

Parameters:

x - State.

Returns:

the output

next

public int next()

Return the next random value.

Returns:

the next random value.

getStateInternal

protected byte[] getStateInternal()

Creates a snapshot of the RNG state.

Overrides:

getStateInternal in class IntProvider

Returns:

the internal state.

setStateInternal

protected void setStateInternal(byte[] s)

Resets the RNG to the given state.

Overrides:

setStateInternal in class IntProvider

Parameters:

s - State (previously obtained by a call to BaseProvider.getStateInternal()).

See Also:

• BaseProvider.checkStateSize(byte[],int)