Class L32X64Mix

java.lang.Object

org.apache.commons.rng.core.BaseProvider

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

org.apache.commons.rng.core.source32.L32X64Mix

All Implemented Interfaces:

RandomIntSource, JumpableUniformRandomProvider, LongJumpableUniformRandomProvider, RestorableUniformRandomProvider, SplittableUniformRandomProvider, UniformRandomProvider

public final class L32X64Mix
extends IntProvider
implements LongJumpableUniformRandomProvider, SplittableUniformRandomProvider

A 32-bit all purpose generator.

This is a member of the LXM family of generators: L=Linear congruential generator; X=Xor based generator; and M=Mix. This member uses a 32-bit LCG and 64-bit Xor-based generator. It is named as "L32X64MixRandom" in the java.util.random package introduced in JDK 17; the LXM family is described in further detail in:

Steele and Vigna (2021) LXM: better splittable pseudorandom number generators (and almost as fast). Proceedings of the ACM on Programming Languages, Volume 5, Article 148, pp 1–31.

Memory footprint is 128 bits and the period is 2³² (2⁶⁴ - 1).

This generator implements LongJumpableUniformRandomProvider. In addition instances created with a different additive parameter for the LCG are robust against accidental correlation in a multi-threaded setting. The additive parameters must be different in the most significant 31-bits.

This generator implements SplittableUniformRandomProvider. The stream of generators created using the splits methods support parallelisation and are robust against accidental correlation by using unique values for the additive parameter for each instance in the same stream. The primitive streaming methods support parallelisation but with no assurances of accidental correlation; each thread uses a new instance with a randomly initialised state.

Since:

1.5

See Also:

• Steele & Vigna (2021) Proc. ACM Programming Languages 5, 1-31
• JDK 17 java.util.random javadoc

Field Summary

Fields

Modifier and Type	Field	Description
private int	la	Per-instance LCG additive parameter (must be odd).
private int	ls	State of the LCG generator.
private static final int	M	LCG multiplier.
private static final int	SEED_SIZE	Size of the state vector.
private int	x0	State 0 of the XBG generator.
private int	x1	State 1 of the XBG generator.

Constructor Summary

Constructors

Modifier	Constructor	Description
	L32X64Mix(int[] seed)	Creates a new instance.
	L32X64Mix(int seed0, int seed1, int seed2, int seed3)	Creates a new instance using a 4 element seed.
private	L32X64Mix(L32X64Mix source)	Creates a copy instance.

Method Summary

Modifier and Type	Method	Description
private static SplittableUniformRandomProvider	create(long seed, UniformRandomProvider source)	Create a new instance using the given seed and source of randomness to initialise the instance.
protected byte[]	getStateInternal()	Creates a snapshot of the RNG state.
UniformRandomProvider	jump()	Creates a copy of the UniformRandomProvider and then retreats the state of the current instance.
JumpableUniformRandomProvider	longJump()	Creates a copy of the UniformRandomProvider and then retreats the state of the current instance.
int	next()	Return the next random value.
private void	setState(int[] state)	Copies the state into the generator state.
protected void	setStateInternal(byte[] s)	Resets the RNG to the given state.
SplittableUniformRandomProvider	split(UniformRandomProvider source)	Creates a new random generator, split off from this one, that implements the SplittableUniformRandomProvider interface.
Stream<SplittableUniformRandomProvider>	splits(long streamSize, SplittableUniformRandomProvider source)	Returns a stream producing the given streamSize number of new random generators, each of which implements the SplittableUniformRandomProvider interface.

Methods inherited from class IntProvider

nextBoolean, nextBytes, nextBytes, nextBytesFill, 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 JumpableUniformRandomProvider

jumps, jumps

Methods inherited from interface LongJumpableUniformRandomProvider

longJumps, longJumps

Methods inherited from interface SplittableUniformRandomProvider

doubles, doubles, doubles, doubles, ints, ints, ints, ints, longs, longs, longs, longs, split, splits, splits, splits

Methods inherited from interface UniformRandomProvider

nextBoolean, nextBytes, nextBytes, nextDouble, nextDouble, nextDouble, nextFloat, nextFloat, nextFloat, nextInt, nextInt, nextInt, nextLong, nextLong, nextLong

Field Details

M

private static final int M

LCG multiplier.

See Also:

• Constant Field Values

SEED_SIZE

private static final int SEED_SIZE

Size of the state vector.

See Also:

• Constant Field Values

la

private int la

Per-instance LCG additive parameter (must be odd). Cannot be final to support RestorableUniformRandomProvider.

ls

private int ls

State of the LCG generator.

x0

private int x0

State 0 of the XBG generator.

x1

private int x1

State 1 of the XBG generator.

Constructor Details

L32X64Mix

public L32X64Mix(int[] seed)

Creates a new instance.

Parameters:

seed - Initial seed. If the length is larger than 4, only the first 4 elements will be used; if smaller, the remaining elements will be automatically set. A seed containing all zeros in the last two elements will create a non-functional XBG sub-generator and a low quality output with a period of 2³².

The 1st element is used to set the LCG increment; the least significant bit is set to odd to ensure a full period LCG. The 2nd element is used to set the LCG state.

L32X64Mix

public L32X64Mix(int seed0,
 int seed1,
 int seed2,
 int seed3)

Creates a new instance using a 4 element seed. A seed containing all zeros in the last two elements will create a non-functional XBG sub-generator and a low quality output with a period of 2³².

The 1st element is used to set the LCG increment; the least significant bit is set to odd to ensure a full period LCG. The 2nd element is used to set the LCG state.

Parameters:

seed0 - Initial seed element 0.

seed1 - Initial seed element 1.

seed2 - Initial seed element 2.

seed3 - Initial seed element 3.

L32X64Mix

private L32X64Mix(L32X64Mix source)

Creates a copy instance.

Parameters:

source - Source to copy.

Method Details

setState

private void setState(int[] state)

Copies the state into the generator state.

Parameters:

state - the new state

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)

next

public int next()

Return the next random value.

Specified by:

next in interface RandomIntSource

Returns:

the next random value.

jump

public UniformRandomProvider jump()

Creates a copy of the UniformRandomProvider and then retreats the state of the current instance. The copy is returned.

The jump is performed by advancing the state of the LCG sub-generator by 1 cycle. The XBG state is unchanged. The jump size is the equivalent of moving the state backwards by (2⁶⁴ - 1) positions. It can provide up to 2³² non-overlapping subsequences.

Specified by:

jump in interface JumpableUniformRandomProvider

Returns:

A copy of the current state.

longJump

public JumpableUniformRandomProvider longJump()

Creates a copy of the UniformRandomProvider and then retreats the state of the current instance. The copy is returned.

The jump is performed by advancing the state of the LCG sub-generator by 2¹⁶ cycles. The XBG state is unchanged. The jump size is the equivalent of moving the state backwards by 2¹⁶ (2⁶⁴ - 1) positions. It can provide up to 2¹⁶ non-overlapping subsequences of length 2¹⁶ (2⁶⁴ - 1); each subsequence can provide up to 2¹⁶ non-overlapping subsequences of length (2⁶⁴ - 1) using the jump() method.

Specified by:

longJump in interface LongJumpableUniformRandomProvider

Returns:

A copy of the current state.

split

public SplittableUniformRandomProvider split(UniformRandomProvider source)

Creates a new random generator, split off from this one, that implements the SplittableUniformRandomProvider interface.

Specified by:

split in interface SplittableUniformRandomProvider

Parameters:

source - A source of randomness used to initialise the new instance.

Returns:

A new instance.

splits

public Stream<SplittableUniformRandomProvider> splits(long streamSize,
 SplittableUniformRandomProvider source)

Returns a stream producing the given streamSize number of new random generators, each of which implements the SplittableUniformRandomProvider interface.

Specified by:

splits in interface SplittableUniformRandomProvider

Parameters:

streamSize - Number of objects to generate.

source - A source of randomness used to initialise the new instances; this may be split to provide a source of randomness across a parallel stream.

Returns:

a stream of random generators; the stream is limited to the given streamSize.

create

private static SplittableUniformRandomProvider create(long seed,
 UniformRandomProvider source)

Create a new instance using the given seed and source of randomness to initialise the instance.

Parameters:

seed - Seed used to initialise the instance.

source - Source of randomness used to initialise the instance.

Returns:

A new instance.