Package io.github.pr0methean.betterrandom.prng

Class XorShiftRandom

java.lang.Object

java.util.Random

io.github.pr0methean.betterrandom.prng.BaseRandom

io.github.pr0methean.betterrandom.prng.XorShiftRandom

All Implemented Interfaces:

ByteArrayReseedableRandom, EntropyCountingRandom, Java8CompatRandom, RepeatableRandom, Dumpable, Serializable

public class XorShiftRandom
extends BaseRandom

Very fast pseudo random number generator. See this page ( archive) for a description. This RNG has a period of about 2¹⁶⁰, which is not as long as the MersenneTwisterRandom but it is faster.

NOTE: Because instances of this class require 160-bit seeds, it is not possible to seed this RNG using the setSeed(long) method inherited from Random. Calls to this method will have no effect. Instead the seed must be set by a constructor.

Since:

1.2

Author:

Daniel Dyer

See Also:

Serialized Form

Field Summary

Fields inherited from class io.github.pr0methean.betterrandom.prng.BaseRandom

ENTROPY_OF_DOUBLE, ENTROPY_OF_FLOAT, entropyBits, lock, randomSeeder, seed, superConstructorFinished

Constructor Summary

Constructors

Constructor	Description
XorShiftRandom()	Creates a new RNG and seeds it using the DefaultSeedGenerator.
XorShiftRandom(byte[] seed)	Creates an RNG and seeds it with the specified seed data.
XorShiftRandom(SeedGenerator seedGenerator)	Seed the RNG using the provided seed generation strategy.

Method Summary

Modifier and Type	Method	Description
protected MoreObjects.ToStringHelper	addSubclassFields(MoreObjects.ToStringHelper original)	Adds the fields that were not inherited from BaseRandom to the given MoreObjects.ToStringHelper for dumping.
int	getNewSeedLength()	Returns the preferred length of a new byte-array seed.
byte[]	getSeed()	Returns the seed.
protected int	next(int bits)	Generates the next pseudorandom number.
void	setSeed(long seed)	Reseeds this PRNG using the DefaultSeedGenerator, since it needs a longer seed.
protected void	setSeedInternal(byte[] seed)	Sets the seed, and should be overridden to set other state that derives from the seed.

Methods inherited from class io.github.pr0methean.betterrandom.prng.BaseRandom

checkLength, creditEntropyForNewSeed, debitEntropy, doubles, doubles, doubles, doubles, dump, entropyOfInt, entropyOfLong, fallbackSetSeedIfInitialized, gaussians, gaussians, getEntropyBits, getRandomSeeder, initTransientFields, internalNextGaussian, ints, ints, ints, ints, lockForNextGaussian, longs, longs, longs, longs, needsReseedingEarly, nextBoolean, nextBytes, nextDouble, nextDouble, nextDouble, nextDoubleNoEntropyDebit, nextElement, nextElement, nextEnum, nextFloat, nextGaussian, nextInt, nextInt, nextInt, nextLong, nextLong, nextLong, nextLongNoEntropyDebit, preferSeedWithLong, setRandomSeeder, setSeed, supportsMultipleSeedLengths, unlockForNextGaussian, usesParallelStreams, withProbability, withProbabilityInternal

Methods inherited from class java.lang.Object

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

Constructor Detail

XorShiftRandom

public XorShiftRandom(byte[] seed)

Creates an RNG and seeds it with the specified seed data.

Parameters:

seed - 20 bytes of seed data used to initialize the RNG.

XorShiftRandom

public XorShiftRandom()
               throws SeedException

Creates a new RNG and seeds it using the DefaultSeedGenerator.

Throws:

SeedException - if the DefaultSeedGenerator fails to generate a seed.

XorShiftRandom

public XorShiftRandom(SeedGenerator seedGenerator)
               throws SeedException

Seed the RNG using the provided seed generation strategy.

Parameters:

seedGenerator - The seed generation strategy that will provide the seed value for this RNG.

Throws:

SeedException - if there is a problem generating a seed.

Method Detail

addSubclassFields

protected MoreObjects.ToStringHelper addSubclassFields(MoreObjects.ToStringHelper original)

Description copied from class: BaseRandom

Adds the fields that were not inherited from BaseRandom to the given MoreObjects.ToStringHelper for dumping.

Specified by:

addSubclassFields in class BaseRandom

Parameters:

original - a MoreObjects.ToStringHelper object.

Returns:

original with the fields not inherited from BaseRandom written to it.

setSeed

public void setSeed(long seed)

Reseeds this PRNG using the DefaultSeedGenerator, since it needs a longer seed.

Specified by:

setSeed in interface Java8CompatRandom

Overrides:

setSeed in class BaseRandom

Parameters:

seed - ignored

getSeed

public byte[] getSeed()

Description copied from interface: RepeatableRandom

Returns the seed.

Specified by:

getSeed in interface RepeatableRandom

Overrides:

getSeed in class BaseRandom

Returns:

The seed data used to initialize this pseudo-random number generator.

setSeedInternal

protected void setSeedInternal(byte[] seed)

Description copied from class: BaseRandom

Sets the seed, and should be overridden to set other state that derives from the seed. Called by BaseRandom.setSeed(byte[]), constructors, and readObject(ObjectInputStream). When called after initialization, the BaseRandom.lock is always held.

Overrides:

setSeedInternal in class BaseRandom

Parameters:

seed - The new seed.

next

protected int next(int bits)

Description copied from class: BaseRandom

Generates the next pseudorandom number. Called by all other random-number-generating methods. Should not debit the entropy count, since that's done by the calling methods according to the amount they actually output (see for example BaseRandom.withProbability(double), which uses 53 random bits but outputs only one, and thus debits only 1 bit of entropy).

Specified by:

next in class BaseRandom

getNewSeedLength

public int getNewSeedLength()

Description copied from interface: ByteArrayReseedableRandom

Returns the preferred length of a new byte-array seed. "Preferred" is implementation-defined when multiple seed lengths are supported, but should probably usually mean the longest one, since the longer the seed, the more random the output.

Specified by:

getNewSeedLength in interface ByteArrayReseedableRandom

Specified by:

getNewSeedLength in class BaseRandom

Returns:

The desired length of a new byte-array seed.