java.lang.Object
- java.util.Random
- - io.github.pr0methean.betterrandom.prng.BaseRandom
  - - io.github.pr0methean.betterrandom.prng.Pcg128Random

All Implemented Interfaces:

ByteArrayReseedableRandom, EntropyCountingRandom, Java8CompatRandom, RepeatableRandom, SeekableRandom, Dumpable, Serializable
```
public class Pcg128Random
extends BaseRandom
implements SeekableRandom
```
From the original description, "PCG is a family of simple fast space-efficient statistically good algorithms for random number generation. Unlike many general-purpose RNGs, they are also hard to predict." This is a Java port of the "XSH RR 128/64" generator presented at http://www.pcg-random.org/. Period is 2¹²⁶ bits. This PRNG is seekable.
Sharing a single instance across threads that are frequently using it concurrently isn't recommended, unless memory is too constrained to use with a ThreadLocalRandomWrapper.

Author:

M.E. O'Neill (algorithm and C++ implementation), Chris Hennick (Java port)

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
`Pcg128Random()`	Creates a new PRNG with a seed from the `DefaultSeedGenerator`.
`Pcg128Random(byte[] seed)`	Creates a new PRNG with the provided seed.
`Pcg128Random(SeedGenerator seedGenerator)`	Creates a new PRNG with a seed from the provided `SeedGenerator`.

Method Summary

All Methods Instance Methods Concrete Methods
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.
`void`	`advance(long delta)`	Advances the generator forward `delta` steps, but does so in logarithmic time.
`void`	`advance(long highDelta, long lowDelta)`	Advances the generator forward `highDelta << 64 + lowDelta` steps, but does so in logarithmic time.
`int`	`getNewSeedLength()`	Returns the preferred length of a new byte-array seed.
`protected void`	`initTransientFields()`	Called in constructor and readObject to initialize transient fields.
`protected int`	`next(int bits)`	Generates the next pseudorandom number.
`protected double`	`nextDoubleNoEntropyDebit()`	Returns the next random `double` between 0.0 (inclusive) and 1.0 (exclusive), but does not debit entropy.
`protected long`	`nextLongNoEntropyDebit()`	Returns the next random `long`, but does not debit entropy.
`void`	`setSeed(long seed)`	Sets the seed of this random number generator using a single long seed, if this implementation supports that.
`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, getSeed, internalNextGaussian, ints, ints, ints, ints, lockForNextGaussian, longs, longs, longs, longs, needsReseedingEarly, nextBoolean, nextBytes, nextDouble, nextDouble, nextDouble, nextElement, nextElement, nextEnum, nextFloat, nextGaussian, nextInt, nextInt, nextInt, nextLong, nextLong, nextLong, 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

Methods inherited from interface io.github.pr0methean.betterrandom.RepeatableRandom
getSeed

- Constructor Detail
  - Pcg128Random
```
public Pcg128Random()
```
    Creates a new PRNG with a seed from the DefaultSeedGenerator.
  - Pcg128Random
```
public Pcg128Random(SeedGenerator seedGenerator)
             throws SeedException
```
    Creates a new PRNG with a seed from the provided SeedGenerator.
    
    Parameters:
    
    seedGenerator - the seed generator that will generate the initial seed
    
    Throws:
    
    SeedException - if seedGenerator fails to generate a seed
  - Pcg128Random
```
public Pcg128Random(byte[] seed)
```
    Creates a new PRNG with the provided seed.
    
    Parameters:
    
    seed - the seed; must be exactly 16 bytes
- Method Detail
  - initTransientFields
```
protected void initTransientFields()
```
    Description copied from class: BaseRandom
    
    Called in constructor and readObject to initialize transient fields.
    
    Overrides:
    
    initTransientFields in class BaseRandom
  - setSeed
```
public void setSeed(long seed)
```
    Description copied from class: BaseRandom
    
    Sets the seed of this random number generator using a single long seed, if this implementation supports that. If it is capable of using 64 bits or less of seed data (i.e. if {@link #getNewSeedLength()} <= {@link Long#BYTES}), then this method shall replace the entire seed as Random.setSeed(long) does; otherwise, it shall either combine the input with the existing seed as SecureRandom.setSeed(long) does, or it shall generate a new seed using the DefaultSeedGenerator. The latter is a backward-compatibility measure and can be very slow.
    
    Specified by:
    
    setSeed in interface Java8CompatRandom
    
    Overrides:
    
    setSeed in class BaseRandom
  - nextDoubleNoEntropyDebit
```
protected double nextDoubleNoEntropyDebit()
```
    Description copied from class: BaseRandom
    
    Returns the next random double between 0.0 (inclusive) and 1.0 (exclusive), but does not debit entropy.
    
    Overrides:
    
    nextDoubleNoEntropyDebit in class BaseRandom
    
    Returns:
    
    a pseudorandom double.
  - advance
```
public void advance(long delta)
```
    Description copied from interface: SeekableRandom
    
    Advances the generator forward delta steps, but does so in logarithmic time.
    
    Specified by:
    
    advance in interface SeekableRandom
    
    Parameters:
    
    delta - the number of steps to advance; can be negative
  - advance
```
public void advance(long highDelta,
                    long lowDelta)
```
    Advances the generator forward highDelta << 64 + lowDelta steps, but does so in logarithmic time.
    
    Parameters:
    
    highDelta - high quadword of the distance to advance
    
    lowDelta - low quadword of the distance to advance
  - setSeedInternal
```
public 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
  - nextLongNoEntropyDebit
```
protected long nextLongNoEntropyDebit()
```
    Description copied from class: BaseRandom
    
    Returns the next random long, but does not debit entropy.
    
    Overrides:
    
    nextLongNoEntropyDebit in class BaseRandom
    
    Returns:
    
    a pseudorandom long with all possible values equally likely.
  - 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.
  - 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.

Class Pcg128Random

Field Summary

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

Constructor Summary

Method Summary

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

Methods inherited from class java.lang.Object

Methods inherited from interface io.github.pr0methean.betterrandom.RepeatableRandom

Constructor Detail

Pcg128Random

Pcg128Random

Pcg128Random

Method Detail

initTransientFields

setSeed

nextDoubleNoEntropyDebit

advance

advance

setSeedInternal

next

nextLongNoEntropyDebit

addSubclassFields

getNewSeedLength