Class L64X128Mix

java.lang.Object

org.apache.commons.rng.core.BaseProvider

org.apache.commons.rng.core.source64.LongProvider

org.apache.commons.rng.core.source64.AbstractL64

org.apache.commons.rng.core.source64.AbstractL64X128

org.apache.commons.rng.core.source64.L64X128Mix

All Implemented Interfaces:

RandomLongSource, JumpableUniformRandomProvider, LongJumpableUniformRandomProvider, RestorableUniformRandomProvider, SplittableUniformRandomProvider, UniformRandomProvider

public class L64X128Mix
extends AbstractL64X128
implements SplittableUniformRandomProvider

A 64-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 64-bit LCG and 128-bit Xor-based generator. It is named as "L64X128MixRandom" 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 256 bits and the period is 2⁶⁴ (2¹²⁸ - 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 63-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 inherited from class AbstractL64X128

M, x0, x1

Fields inherited from class AbstractL64

la, ls

Constructor Summary

Constructors

Modifier	Constructor	Description
	L64X128Mix(long[] seed)	Creates a new instance.
	L64X128Mix(long seed0, long seed1, long seed2, long seed3)	Creates a new instance using a 4 element seed.
protected	L64X128Mix(L64X128Mix source)	Creates a copy instance.

Method Summary

Modifier and Type	Method	Description
protected L64X128Mix	copy()	Create a copy.
private static SplittableUniformRandomProvider	create(long seed, UniformRandomProvider source)	Create a new instance using the given seed and source of randomness to initialise the instance.
long	next()	Return the next random value.
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 AbstractL64X128

getStateInternal, jump, longJump, setStateInternal

Methods inherited from class LongProvider

nextBoolean, 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

Constructor Details

L64X128Mix

public L64X128Mix(long[] 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 2⁶⁴.

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.

L64X128Mix

public L64X128Mix(long seed0,
 long seed1,
 long seed2,
 long 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 2⁶⁴.

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.

L64X128Mix

protected L64X128Mix(L64X128Mix source)

Creates a copy instance.

Parameters:

source - Source to copy.

Method Details

next

public long next()

Return the next random value.

Specified by:

next in interface RandomLongSource

Returns:

the next random value.

copy

protected L64X128Mix copy()

Create a copy.

Specified by:

copy in class AbstractL64

Returns:

the copy

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.