OpenJDK 1.23 · jdk.internal.random.L128X128MixRandom

A "splittable" pseudorandom number generator (PRNG) whose period is roughly 2²⁵⁶. Class L128X128MixRandom implements interfaces RandomGenerator and SplittableGenerator, and therefore supports methods for producing pseudorandomly chosen values of type int, long, float, double, and boolean (and for producing streams of pseudorandomly chosen numbers of type int, long, and double), as well as methods for creating new split-off L128X128MixRandom objects or streams of such objects.

The L128X128MixRandom algorithm is a specific member of the LXM family of algorithms for pseudorandom number generators; for more information, see the documentation for package jdk.random. Each instance of L128X128MixRandom has 256 bits of state plus one 128-bit instance-specific parameter.

If two instances of L128X128MixRandom are created with the same seed within the same program execution, and the same sequence of method calls is made for each, they will generate and return identical sequences of values.

As with java.util.SplittableRandom, instances of L128X128MixRandom are not thread-safe. They are designed to be split, not shared, across threads (see the split method). For example, a java.util.concurrent.ForkJoinTask fork/join-style computation using random numbers might include a construction of the form new Subtask(someL128X128MixRandom.split()).fork().

This class provides additional methods for generating random streams, that employ the above techniques when used in stream.parallel() mode.

Instances of L128X128MixRandom are not cryptographically secure. Consider instead using java.security.SecureRandom in security-sensitive applications. Additionally, default-constructed instances do not use a cryptographically random seed unless the system property java.util.secureRandomSeed is set to true.

Field Summary

Modifier and Type	Field and Description
private final long	ah The parameter that is used as an additive constant for the LCG.
private final long	al The parameter that is used as an additive constant for the LCG.
private static final AtomicLong	defaultGen The seed generator for default constructors.
private static final long	ML
private long	sh The per-instance state: sh and sl for the LCG; x0 and x1 for the XBG.
private long	sl The per-instance state: sh and sl for the LCG; x0 and x1 for the XBG.
private long	x0 The per-instance state: sh and sl for the LCG; x0 and x1 for the XBG.
private long	x1 The per-instance state: sh and sl for the LCG; x0 and x1 for the XBG.

Constructor Summary

Access	Constructor and Description
public	L128X128MixRandom(long high half of the additive parameter for the LCG ah, long low half of the additive parameter for the LCG al, long high half of the initial state for the LCG sh, long low half of the initial state for the LCG sl, long first word of the initial state for the XBG x0, long second word of the initial state for the XBG x1) Basic constructor that initializes all fields from parameters.
public	L128X128MixRandom(long the initial seed seed) Creates a new instance of `L128X128MixRandom` using the specified `long` value as the initial seed.
public	L128X128MixRandom() Creates a new instance of `L128X128MixRandom` that is likely to generate sequences of values that are statistically independent of those of any other instances in the current program execution, but may, and typically does, vary across program invocations.
public	L128X128MixRandom(byte[] the initial seed seed) Creates a new instance of `L128X128MixRandom` using the specified array of initial seed bytes.

Modifier and Type	Method and Description
public long	nextLong() Implements java.util.random.RandomGenerator.nextLong. Returns a pseudorandomly chosen `long` value.
public RandomGenerator.SplittableGenerator	split(RandomGenerator.SplittableGenerator source, long brine) Implements abstract jdk.internal.util.random.RandomSupport.AbstractSplittableWithBrineGenerator.split.

Field Detail

ah	back to summary
private final long ah The parameter that is used as an additive constant for the LCG. Must be odd (therefore al must be odd).

al	back to summary
private final long al The parameter that is used as an additive constant for the LCG. Must be odd (therefore al must be odd).

defaultGen	back to summary
private static final AtomicLong defaultGen The seed generator for default constructors.

ML	back to summary
private static final long ML

sh	back to summary
private long sh The per-instance state: sh and sl for the LCG; x0 and x1 for the XBG. At least one of x0 and x1 must be nonzero.

sl	back to summary
private long sl The per-instance state: sh and sl for the LCG; x0 and x1 for the XBG. At least one of x0 and x1 must be nonzero.

x0	back to summary
private long x0 The per-instance state: sh and sl for the LCG; x0 and x1 for the XBG. At least one of x0 and x1 must be nonzero.

x1	back to summary
private long x1 The per-instance state: sh and sl for the LCG; x0 and x1 for the XBG. At least one of x0 and x1 must be nonzero.

Constructor Detail

L128X128MixRandom	back to summary
public L128X128MixRandom(long ah, long al, long sh, long sl, long x0, long x1) Basic constructor that initializes all fields from parameters. It then adjusts the field values if necessary to ensure that all constraints on the values of fields are met. Parameters ah:long high half of the additive parameter for the LCG al:long low half of the additive parameter for the LCG sh:long high half of the initial state for the LCG sl:long low half of the initial state for the LCG x0:long first word of the initial state for the XBG x1:long second word of the initial state for the XBG

L128X128MixRandom

back to summary

public L128X128MixRandom(long ah, long al, long sh, long sl, long x0, long x1)

Basic constructor that initializes all fields from parameters. It then adjusts the field values if necessary to ensure that all constraints on the values of fields are met.

Parameters

ah:long: high half of the additive parameter for the LCG
al:long: low half of the additive parameter for the LCG
sh:long: high half of the initial state for the LCG
sl:long: low half of the initial state for the LCG
x0:long: first word of the initial state for the XBG
x1:long: second word of the initial state for the XBG

L128X128MixRandom back to summary

L128X128MixRandom	back to summary
public L128X128MixRandom(long seed) Creates a new instance of `L128X128MixRandom` using the specified `long` value as the initial seed. Instances of `L128X128MixRandom` created with the same seed in the same program generate identical sequences of values. Parameters seed:long the initial seed

public L128X128MixRandom(long seed)

Creates a new instance of L128X128MixRandom using the specified long value as the initial seed. Instances of L128X128MixRandom created with the same seed in the same program generate identical sequences of values.

Parameters

seed:long: the initial seed

L128X128MixRandom	back to summary
public L128X128MixRandom() Creates a new instance of `L128X128MixRandom` that is likely to generate sequences of values that are statistically independent of those of any other instances in the current program execution, but may, and typically does, vary across program invocations.

L128X128MixRandom back to summary

L128X128MixRandom	back to summary
public L128X128MixRandom(byte[] seed) Creates a new instance of `L128X128MixRandom` using the specified array of initial seed bytes. Instances of `L128X128MixRandom` created with the same seed array in the same program execution generate identical sequences of values. Parameters seed:byte[] the initial seed

public L128X128MixRandom(byte[] seed)

Creates a new instance of L128X128MixRandom using the specified array of initial seed bytes. Instances of L128X128MixRandom created with the same seed array in the same program execution generate identical sequences of values.

Parameters

seed:byte[]: the initial seed

public final Class L128X128MixRandom

Field Summary

Constructor Summary

Method Summary

Field Detail

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Method Detail