Package com.github.tommyettinger.random

Class ExtendoRandom

java.lang.Object

java.util.Random

com.github.tommyettinger.random.EnhancedRandom

com.github.tommyettinger.random.ExtendoRandom

All Implemented Interfaces:

Externalizable, Serializable, RandomGenerator

public final class ExtendoRandom
extends EnhancedRandom

A hash-on-counters RNG with a period of 2 to the 128. This is similar to OrbitalRandom, but has the option to have an arbitrary amount of extended stream values to change the stream in many ways.
Uses a unary hash (similar to DistinctRandom and FlowRandom), passing it a combination of the two different additive counters this has for its state. One counter is rotated before XORing with the other, which replaces a xorshift in the original. The first counter only adds the same large odd number at each step, but the second counter adds both a different large odd number and the result of BitConversion.countLeadingZeros(long) on the first state. This way of mixing the states means while the first counter on its own has a period of 2 to the 64, the second counter is very slightly offset from being in-sync with the first, and since it depends upon the first counter, its period is 2 to the 128.
Each extended stream/state value is added to the unary hash after each multiplication, with every extended state item added at two different points in the unary hash. The unary hash has more steps (all similar to MX3, but with addition for the extended states) if the extended state is larger.
With an extended state of one 0 value, this passes 128TB of PractRand testing with no anomalies.
In most regards, it should have similar statistical qualities to FlowRandom, except that it is guaranteed to produce each possible long value exactly (2 to the 64) times. Unlike DistinctRandom, it is not possible to figure out the current state given one output, and it would take an unknown amount of additional outputs to retrieve the current state exactly. It shares this quality with FlowRandom.

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

Constructor Summary

Constructors

Constructor	Description
ExtendoRandom()	Creates a new ExtendoRandom with a random state.
ExtendoRandom(long seed)	Creates a new ExtendoRandom with the given seed; all long values are permitted.
ExtendoRandom(long stateA, long stateB, long... extend)	Creates a new ExtendoRandom with the given two or more states; all long values are permitted for stateA, for stateB, and for each item of extend.

Method Summary

Modifier and Type	Method	Description
ExtendoRandom	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)
long[]	getExtendedState()
BigInteger	getMinimumPeriod()	2 to the 128.
long	getSelectedState(int selection)	Gets the state determined by selection, as-is.
long	getStateA()
long	getStateB()
int	getStateCount()	This generator has 2 long states plus the length of the extended seed, so this returns 2 + getExtendedState().
String	getTag()	Gets the tag used to identify this type of EnhancedRandom, as a String.
int	next(int bits)	Generates the next pseudorandom number with a specific maximum size in bits (not a max number).
long	nextLong()	Returns the next pseudorandom, uniformly distributed long value from this random number generator's sequence.
long	previousLong()	Optional; moves the state to its previous value and returns the previous long that would have been produced by EnhancedRandom.nextLong().
void	readExternal(ObjectInput in)	The object implements the readExternal method to restore its contents by calling the methods of DataInput for primitive types and readObject for objects, strings and arrays.
void	setExtendedState(long[] extend)
void	setSeed(long seed)	This initializes both states of the generator to different values; one is seed, the other is ~seed.
void	setSelectedState(int selection, long value)	Sets one of the states, determined by selection, to value, as-is.
void	setState(long stateA, long stateB)	Sets the state completely to the given two state variables.
void	setStateA(long stateA)	Sets the first part of the state.
void	setStateB(long stateB)	Sets the second part of the state.
ExtendoRandom	stringDeserialize(String data, com.github.tommyettinger.digital.Base base)	Given a String in the format produced by EnhancedRandom.stringSerialize(Base), and the same Base used by the serialization, this will attempt to set this EnhancedRandom object to match the state in the serialized data.
String	toString()

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

appendSerialized, appendSerialized, areEqual, fixGamma, fixGamma, lcm, mainlyGeneratesInt, 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, nextInt, nextLong, nextLong, nextSign, nextSignedInt, nextSignedInt, nextSignedLong, nextSignedLong, nextTriangular, nextTriangular, nextTriangular, nextTriangular, nextUnsignedInt, previousInt, probit, processSignedInt32, processUnsignedInt32, randomElement, randomElement, rateGamma, seedFromMath, setSeed, setSeed, setState, setState, setState, setState, setState, setState, setState, setState, setState, setState, setWith, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, shuffle, skip, 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

Constructor Details

ExtendoRandom

public ExtendoRandom()

Creates a new ExtendoRandom with a random state.

ExtendoRandom

public ExtendoRandom(long seed)

Creates a new ExtendoRandom 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

ExtendoRandom

public ExtendoRandom(long stateA,
 long stateB,
 long... extend)

Creates a new ExtendoRandom with the given two or more states; all long values are permitted for stateA, for stateB, and for each item of extend. States A and B are not changed during assignment. If extend is null or empty, a long array containing only 0 is used instead, otherwise it is copied exactly.

Parameters:

stateA - any long value

stateB - any long 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.

getMinimumPeriod

public BigInteger getMinimumPeriod()

2 to the 128.

Overrides:

getMinimumPeriod in class EnhancedRandom

Returns:

2 to the 128

getStateCount

public int getStateCount()

This generator has 2 long states plus the length of the extended seed, so this returns 2 + getExtendedState().

Overrides:

getStateCount in class EnhancedRandom

Returns:

2 (two) plus the length of getExtendedState()

getSelectedState

public long getSelectedState(int selection)

Gets the state determined by selection, as-is. Selections 0 (or any even number) and 1 (or any odd number) refer to states A and B.

Overrides:

getSelectedState in class EnhancedRandom

Parameters:

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

Returns:

the value of the selected state

setSelectedState

public void setSelectedState(int selection,
 long value)

Sets one of the states, determined by selection, to value, as-is. Selections 0 (or any even number) and 1 (or any odd number) refer to states A and B.

Overrides:

setSelectedState in class EnhancedRandom

Parameters:

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

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

setSeed

public void setSeed(long seed)

This initializes both states of the generator to different values; one is seed, the other is ~seed. (2 to the 64) possible initial generator states can be produced here. The initial states don't need to be randomized at all because of the structure of this generator (the hashing stage it does last is meant to make input patterns unrecognizable).

Specified by:

setSeed in class EnhancedRandom

Parameters:

seed - the initial seed; may be any long

getStateA

public long getStateA()

setStateA

public void setStateA(long stateA)

Sets the first part of the state.

Parameters:

stateA - can be any long

getStateB

public long getStateB()

setStateB

public void setStateB(long stateB)

Sets the second part of the state.

Parameters:

stateB - can be any long

getExtendedState

public long[] getExtendedState()

setExtendedState

public void setExtendedState(long[] extend)

setState

public void setState(long stateA,
 long stateB)

Sets the state completely to the given two state variables. This is the same as calling setStateA(long) and setStateB(long) as a group.

Overrides:

setState in class EnhancedRandom

Parameters:

stateA - the first state; can be any long

stateB - the second state; can be any long

nextLong

public long nextLong()

Description copied from class: EnhancedRandom

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

Specified by:

nextLong in class EnhancedRandom

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()

next

public int next(int bits)

Description copied from class: EnhancedRandom

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 EnhancedRandom.nextInt(int) instead. For some specific cases, this method is more efficient and less biased than EnhancedRandom.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 EnhancedRandom

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

copy

public ExtendoRandom 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.

stringDeserialize

public ExtendoRandom stringDeserialize(String data,
 com.github.tommyettinger.digital.Base base)

Given a String in the format produced by EnhancedRandom.stringSerialize(Base), and the same Base used by the serialization, this will attempt to set this EnhancedRandom object to match the state in the serialized data. This only works if this EnhancedRandom is the same implementation that was serialized, and also needs the Bases to be identical. Returns this EnhancedRandom, after possibly changing its state.

Overrides:

stringDeserialize in class EnhancedRandom

Parameters:

data - a String probably produced by EnhancedRandom.stringSerialize(Base)

base - which Base to use, from the "digital" library, such as Base.BASE10

Returns:

this, after setting its state

See Also:

• You can deserialize a serialized EnhancedRandom String to its correct type using Deserializer.

readExternal

public void readExternal(ObjectInput in)
                  throws IOException

The object implements the readExternal method to restore its contents by calling the methods of DataInput for primitive types and readObject for objects, strings and arrays. The readExternal method must read the values in the same sequence and with the same types as were written by writeExternal.

Specified by:

readExternal in interface Externalizable

Overrides:

readExternal in class EnhancedRandom

Parameters:

in - the stream to read data from in order to restore the object

Throws:

IOException - if I/O errors occur

equals

public boolean equals(Object o)

Overrides:

equals in class Object

toString

public String toString()

Overrides:

toString in class Object