Package com.github.tommyettinger.random

Class Choo32Random

java.lang.Object

java.util.Random

com.github.tommyettinger.random.EnhancedRandom

com.github.tommyettinger.random.Enhanced32Random

com.github.tommyettinger.random.Choo32Random

All Implemented Interfaces:

Externalizable, Serializable, RandomGenerator

public class Choo32Random
extends Enhanced32Random

A random number generator that is optimized for performance on 32-bit machines and with Google Web Toolkit. This uses only add, subtract, (variable) bitwise-rotate, and XOR operations in its state transition, but also uses multiplication (via Math.imul() on GWT) and unsigned right shifts for its output-mixing step. It will usually be compiled out, but this does also use variable = variable + constant | 0; in order to force additions to counters on GWT to actually overflow as they do (and should) on desktop JVMs.
Choo32Random has a guaranteed minimum period of 2 to the 32, and is very likely to have a much longer period for almost all initial states. There are expected to be several (double-digit) relatively long sub-cycles that most states will be within, and relatively few sub-cycles nearing the smallest possible size (2 to the 32, or over 4 billion).
The algorithm used here has four states purely to exploit instruction-level parallelism; one state is a counter (this gives the guaranteed minimum period of 2 to the 32), and the others combine the values of the four states across three variables. It is possible to invert the generator given a full 128-bit state; this is vital for its period and quality. It is not possible to invert the generator given a known small number of outputs; the furthest you can get when inverting the output is to get the current sum of all four states.
This implements all optional methods in EnhancedRandom except EnhancedRandom.skip(long); it does implement previousLong() and previousInt() without using skip().
This uses part of an output mixer found using hash-prospector by TheIronBorn, and runs it on a combination of all four states.
This is called Choo32Random because it is choo-choo-chugging along at improving on the similar ChopRandom. It uses a simpler state transition than ChopRandom, but a more complex output mixer so that it can be used as a sequence of hashes of four values. ChopRandom doesn't actually perform any mixing, which means if you only produce one generation from many generators, that entire group of results will be based entirely on one initial state in each generator. Choo32Random does do some mixing, does it on a combination of all states, and does it on the state after it transitions to the next in the sequence, rather than before. This lets it be used as a hash of 1 to 4 int inputs to get a sequence of random numbers as output. It also means this is slower to generate sequences of results than ChopRandom, though the first result will be actually random with this, but will probably be very correlated with the initial state with ChopRandom.

See Also:

• Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from interface java.util.random.RandomGenerator

RandomGenerator.ArbitrarilyJumpableGenerator, RandomGenerator.JumpableGenerator, RandomGenerator.LeapableGenerator, RandomGenerator.SplittableGenerator, RandomGenerator.StreamableGenerator

Field Summary

Fields

Modifier and Type	Field	Description
protected int	stateA	The first state; can be any int.
protected int	stateB	The second state; can be any int.
protected int	stateC	The third state; can be any int.
protected int	stateD	The fourth state; can be any int.

Constructor Summary

Constructors

Constructor	Description
Choo32Random()	Creates a new Choo32Random with a random state.
Choo32Random(int seed)	Creates a new Choo32Random with the given seed; all long values are permitted.
Choo32Random(int stateA, int stateB, int stateC, int stateD)	Creates a new Choo32Random with the given four states; all int values are permitted.
Choo32Random(long seed)	Creates a new Choo32Random with the given seed; all long values are permitted.

Method Summary

Modifier and Type	Method	Description
Choo32Random	copy()	Creates a new EnhancedRandom with identical states to this one, so if the same EnhancedRandom methods are called on this object and its copy (in the same order), the same outputs will be produced.
boolean	equals(Object o)
BigInteger	getMinimumPeriod()	2 to the 32.
long	getSelectedState(int selection)	Gets the state determined by selection, as-is.
int	getStateA()
int	getStateB()
int	getStateC()
int	getStateCount()	This generator has 4 int states, so this returns 4.
int	getStateD()
String	getTag()	Gets the tag used to identify this type of EnhancedRandom, as a String.
boolean	mainlyGeneratesInt()	This generator mainly generates int values.
int	next(int bits)	Generates the next pseudorandom number with a specific maximum size in bits (not a max number).
int	nextInt()	Returns the next pseudorandom, uniformly distributed int value from this random number generator's sequence.
long	nextLong()	Returns the next pseudorandom, uniformly distributed long value from this random number generator's sequence.
int	previousInt()	Optional; moves the state to its previous value and returns the previous int that would have been produced by EnhancedRandom.nextInt().
long	previousLong()	Optional; moves the state to its previous value and returns the previous long that would have been produced by EnhancedRandom.nextLong().
void	setSeed(int seed)	This initializes all 4 states of the generator to random values based on the given seed.
void	setSeed(long seed)	This initializes all 4 states of the generator to random values based on the given seed.
void	setSelectedState(int selection, long value)	Sets one of the states, determined by selection, to the lower 32 bits of value, as-is.
void	setState(int stateA, int stateB, int stateC, int stateD)	Like the superclass method setState(long, long, long, long), but takes four int values instead of long.
void	setState(long stateA, long stateB, long stateC, long stateD)	Sets the state completely to the given four state variables, casting each to an int.
void	setStateA(int stateA)	Sets the first part of the state to the given int.
void	setStateB(int stateB)	Sets the second part of the state to the given int.
void	setStateC(int stateC)	Sets the third part of the state to the given int.
void	setStateD(int stateD)	Sets the fourth part of the state to the given int.
String	toString()

Methods inherited from class com.github.tommyettinger.random.Enhanced32Random

maxDoubleOf, maxFloatOf, maxIntOf, maxLongOf, minDoubleOf, minFloatOf, minIntOf, minLongOf, nextBoolean, nextBoolean, nextBytes, nextDouble, nextDouble, nextDouble, nextExclusiveDouble, nextExclusiveDouble, nextExclusiveDouble, nextExclusiveDoubleEquidistant, nextExclusiveFloat, nextExclusiveFloat, nextExclusiveFloat, nextExclusiveFloatEquidistant, nextExclusiveSignedDouble, nextExclusiveSignedFloat, nextExponential, nextFloat, nextFloat, nextFloat, nextGaussian, nextGaussian, nextGaussianFloat, nextGaussianFloat, nextInclusiveDouble, nextInclusiveDouble, nextInclusiveDouble, nextInclusiveFloat, nextInclusiveFloat, nextInclusiveFloat, nextInt, nextInt, nextLong, nextLong, nextSign, nextSignedInt, nextSignedInt, nextSignedLong, nextSignedLong, nextTriangular, nextTriangular, nextTriangular, nextTriangular, nextUnsignedInt, randomElement, randomElement, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle

Methods inherited from class com.github.tommyettinger.random.EnhancedRandom

appendSerialized, appendSerialized, areEqual, fixGamma, fixGamma, lcm, probit, processSignedInt32, processUnsignedInt32, rateGamma, readExternal, seedFromMath, setState, setState, setState, setState, setState, setState, setWith, skip, stringDeserialize, stringDeserialize, stringSerialize, stringSerialize, writeExternal

Methods inherited from class java.util.Random

doubles, doubles, doubles, doubles, from, ints, ints, ints, ints, longs, longs, longs, longs

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.random.RandomGenerator

isDeprecated

Field Details

stateA

protected int stateA

The first state; can be any int.

stateB

protected int stateB

The second state; can be any int.

stateC

protected int stateC

The third state; can be any int.

stateD

protected int stateD

The fourth state; can be any int.

Constructor Details

Choo32Random

public Choo32Random()

Creates a new Choo32Random with a random state.

Choo32Random

public Choo32Random(long seed)

Creates a new Choo32Random with the given seed; all long values are permitted. The seed will be passed to setSeed(long) to attempt to adequately distribute the seed randomly.

Parameters:

seed - any long value

Choo32Random

public Choo32Random(int seed)

Creates a new Choo32Random with the given seed; all long values are permitted. The seed will be passed to setSeed(int) to attempt to adequately distribute the seed randomly.

Parameters:

seed - any long value

Choo32Random

public Choo32Random(int stateA,
 int stateB,
 int stateC,
 int stateD)

Creates a new Choo32Random with the given four states; all int values are permitted. These states will be used verbatim.

Parameters:

stateA - any int value

stateB - any int value

stateC - any int value

stateD - any int value

Method Details

getTag

public String getTag()

Description copied from class: EnhancedRandom

Gets the tag used to identify this type of EnhancedRandom, as a String. This tag should be unique, and for uniformity purposes, all tags used in this library are 4 characters long. User-defined tags should have a different length.

Specified by:

getTag in class EnhancedRandom

Returns:

a unique String identifier for this type of EnhancedRandom; usually 4 chars long.

mainlyGeneratesInt

public boolean mainlyGeneratesInt()

This generator mainly generates int values.

Overrides:

mainlyGeneratesInt in class Enhanced32Random

Returns:

true

See Also:

• This is closely related to the minimum period length.

getMinimumPeriod

public BigInteger getMinimumPeriod()

2 to the 32.

Overrides:

getMinimumPeriod in class EnhancedRandom

Returns:

2 to the 32

getStateCount

public int getStateCount()

This generator has 4 int states, so this returns 4.

Overrides:

getStateCount in class EnhancedRandom

Returns:

4 (four)

getSelectedState

public long getSelectedState(int selection)

Gets the state determined by selection, as-is. The value for selection should be between 0 and 3, inclusive; if it is any other value this gets state D as if 3 was given.

Overrides:

getSelectedState in class EnhancedRandom

Parameters:

selection - used to select which state variable to get; generally 0, 1, 2, or 3

Returns:

the value of the selected state, which is an int that will be promoted to long

setSelectedState

public void setSelectedState(int selection,
 long value)

Sets one of the states, determined by selection, to the lower 32 bits of value, as-is. Selections 0, 1, 2, and 3 refer to states A, B, C, and D, and if the selection is anything else, this treats it as 3 and sets stateD. This always casts value to an int before using it.

Overrides:

setSelectedState in class EnhancedRandom

Parameters:

selection - used to select which state variable to set; generally 0, 1, 2, or 3

value - the exact value to use for the selected state, if valid

setSeed

public void setSeed(long seed)

This initializes all 4 states of the generator to random values based on the given seed. (2 to the 64) possible initial generator states can be produced here.

Specified by:

setSeed in class EnhancedRandom

Parameters:

seed - the initial seed; may be any long

setSeed

public void setSeed(int seed)

This initializes all 4 states of the generator to random values based on the given seed. (2 to the 32) possible initial generator states can be produced here.

Parameters:

seed - the initial seed; may be any long

getStateA

public int getStateA()

setStateA

public void setStateA(int stateA)

Sets the first part of the state to the given int.

Parameters:

stateA - can be any int

getStateB

public int getStateB()

setStateB

public void setStateB(int stateB)

Sets the second part of the state to the given int.

Parameters:

stateB - can be any int

getStateC

public int getStateC()

setStateC

public void setStateC(int stateC)

Sets the third part of the state to the given int.

Parameters:

stateC - can be any int

getStateD

public int getStateD()

setStateD

public void setStateD(int stateD)

Sets the fourth part of the state to the given int.

Parameters:

stateD - can be any int

setState

public void setState(long stateA,
 long stateB,
 long stateC,
 long stateD)

Sets the state completely to the given four state variables, casting each to an int. This is the same as calling setStateA(int), setStateB(int), setStateC(int), and setStateD(int) as a group.

Overrides:

setState in class EnhancedRandom

Parameters:

stateA - the first state; can be any long, but will be cast to an int before use

stateB - the second state; can be any long, but will be cast to an int before use

stateC - the third state; can be any long, but will be cast to an int before use

stateD - the fourth state; can be any long, but will be cast to an int before use

setState

public void setState(int stateA,
 int stateB,
 int stateC,
 int stateD)

Like the superclass method setState(long, long, long, long), but takes four int values instead of long. This can avoid creating longs on JS-targeting platforms, which tends to be quite slow.

Parameters:

stateA - the first state; can be any int

stateB - the second state; can be any int

stateC - the third state; can be any int

stateD - the fourth state; can be any int

nextLong

public long nextLong()

Description copied from class: Enhanced32Random

Returns the next pseudorandom, uniformly distributed long value from this random number generator's sequence. The general contract of nextLong is that one long value is pseudorandomly generated and returned.
The only methods that need to be implemented by this interface are this and EnhancedRandom.copy(), though other methods can be implemented as appropriate for generators that, for instance, natively produce ints rather than longs.

Specified by:

nextLong in interface RandomGenerator

Overrides:

nextLong in class Enhanced32Random

Returns:

the next pseudorandom, uniformly distributed long value from this random number generator's sequence

previousLong

public long previousLong()

Description copied from class: EnhancedRandom

Optional; moves the state to its previous value and returns the previous long that would have been produced by EnhancedRandom.nextLong(). This can be equivalent to calling EnhancedRandom.skip(long) with -1L, but not always; many generators can't efficiently skip long distances, but can step back by one value.
Generators that natively generate int results typically produce long values by generating an int for the high 32 bits and an int for the low 32 bits. When producing the previous long, the order the high and low bits are generated, such as by EnhancedRandom.previousInt(), should be reversed. Generators that natively produce long values usually don't need to implement EnhancedRandom.previousInt(), but those that produce int usually should implement it, and may optionally call previousInt() twice in this method.
If you know how to implement the reverse of a particular random number generator, it is recommended you do so here, rather than rely on skip(). This isn't always easy, but should always be possible for any decent PRNG (some historical PRNGs, such as the Middle-Square PRNG, cannot be reversed at all). If a generator cannot be reversed because multiple initial states can transition to the same subsequent state, it is known to have statistical problems that are not necessarily present in a generator that matches one initial state to one subsequent state.
The public implementation calls EnhancedRandom.skip(long) with -1L, and if skip() has not been implemented differently, then it will throw an UnsupportedOperationException.

Overrides:

previousLong in class EnhancedRandom

Returns:

the previous number this would have produced with EnhancedRandom.nextLong()

previousInt

public int previousInt()

Description copied from class: EnhancedRandom

Optional; moves the state to its previous value and returns the previous int that would have been produced by EnhancedRandom.nextInt(). This can be equivalent to calling EnhancedRandom.previousLong() and casting to int, but not always; generators that natively generate int results typically move the state once in nextInt() and twice in nextLong(), and should move the state back once here.
If EnhancedRandom.nextInt() is implemented using a call to EnhancedRandom.nextLong(), the implementation in this class is almost always sufficient and correct. If nextInt() changes state differently from nextLong(), then this should be implemented, if feasible, and EnhancedRandom.previousLong() can be implemented using this method. If you know how to implement the reverse of a particular random number generator, it is recommended you do so here, rather than rely on skip(). This isn't always easy, but should always be possible for any decent PRNG (some historical PRNGs, such as the Middle-Square PRNG, cannot be reversed at all). If a generator cannot be reversed because multiple initial states can transition to the same subsequent state, it is known to have statistical problems that are not necessarily present in a generator that matches one initial state to one subsequent state.
The public implementation calls EnhancedRandom.previousLong() and casts it to int, and if previousLong() and skip() have not been implemented differently, then it will throw an UnsupportedOperationException.

Overrides:

previousInt in class EnhancedRandom

Returns:

the previous number this would have produced with EnhancedRandom.nextInt()

next

public int next(int bits)

Description copied from class: Enhanced32Random

Generates the next pseudorandom number with a specific maximum size in bits (not a max number). If you want to get a random number in a range, you should usually use Enhanced32Random.nextInt(int) instead. For some specific cases, this method is more efficient and less biased than Enhanced32Random.nextInt(int). For bits values between 1 and 30, this should be similar in effect to nextInt(1 << bits); though it won't typically produce the same values, they will have the correct range. If bits is 31, this can return any non-negative int; note that nextInt(1 << 31) won't behave this way because 1 << 31 is negative. If bits is 32 (or 0), this can return any int.

The general contract of next is that it returns an int value and if the argument bits is between 1 and 32 (inclusive), then that many low-order bits of the returned value will be (approximately) independently chosen bit values, each of which is (approximately) equally likely to be 0 or 1.

Note that you can give this values for bits that are outside its expected range of 1 to 32, but the value used, as long as bits is positive, will effectively be bits % 32. As stated before, a value of 0 for bits is the same as a value of 32.

Overrides:

next in class Enhanced32Random

Parameters:

bits - the amount of random bits to request, from 1 to 32

Returns:

the next pseudorandom value from this random number generator's sequence

nextInt

public int nextInt()

Description copied from class: Enhanced32Random

Returns the next pseudorandom, uniformly distributed int value from this random number generator's sequence. The general contract of nextInt is that one int value is pseudorandomly generated and returned. All 2³² possible int values are produced with (approximately) equal probability.
In Enhanced32Random, this throws an UnsupportedOperationException because the concrete subclass must implement this.

Specified by:

nextInt in interface RandomGenerator

Overrides:

nextInt in class Enhanced32Random

Returns:

the next pseudorandom, uniformly distributed int value from this random number generator's sequence

copy

public Choo32Random copy()

Description copied from class: EnhancedRandom

Creates a new EnhancedRandom with identical states to this one, so if the same EnhancedRandom methods are called on this object and its copy (in the same order), the same outputs will be produced. This is not guaranteed to copy the inherited state of any parent class, so if you call methods that are only implemented by a superclass (like Random) and not this one, the results may differ.

Specified by:

copy in class EnhancedRandom

Returns:

a deep copy of this EnhancedRandom.

equals

public boolean equals(Object o)

Overrides:

equals in class Object

toString

public String toString()

Overrides:

toString in class Object