squidpony.squidmath

Class DistinctRNG

java.lang.Object

squidpony.squidmath.DistinctRNG

All Implemented Interfaces:

java.io.Serializable, RandomnessSource, SkippingRandomness, StatefulRandomness

public class DistinctRNG
extends java.lang.Object
implements StatefulRandomness, SkippingRandomness, java.io.Serializable

A StatefulRandomness with one long state; calling nextLong() will produce every long exactly once before repeating. This has been backported from jdkgdxds, which got this from SquidSquad originally. It is extremely similar to LightRNG, but uses a different mixing/unary-hash function -- where LightRNG uses a variant on MurmurHash3's mixer called Variant 13, this uses Pelle Evensen's Moremur mixer, which performs at the same (high) speed but has somewhat higher quality. This generator has a period of exactly 2 to the 64. It is a rather fast generator, particularly on Java 8 and/or OpenJ9. It has passed 64TB of PractRand testing with no anomalies. This is also a SkippingRandomness.
Created by Tommy Ettinger on 7/13/2021.

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
long	state Can be any long value.

Constructor Summary

Constructors

Constructor and Description
DistinctRNG() Creates a new generator seeded using Math.random.
DistinctRNG(long seed)

Method Summary

Modifier and Type	Method and Description
DistinctRNG	copy() Produces a copy of this RandomnessSource that, if next() and/or nextLong() are called on this object and the copy, both will generate the same sequence of random numbers from the point copy() was called.
boolean	equals(java.lang.Object o)
long	getState() Get the current internal state of the StatefulRandomness as a long.
int	hashCode()
int	next(int bits) Using this method, any algorithm that might use the built-in Java Random can interface with this randomness source.
long	nextLong() Using this method, any algorithm that needs to efficiently generate more than 32 bits of random data can interface with this randomness source.
void	setSeed(long seed) This initializes the 1 state of the generator to random values based on the given seed.
void	setState(long state) Set the current internal state of this StatefulRandomness with a long.
long	skip(long advance) Advances or rolls back the SkippingRandomness' state without actually generating each number.
java.lang.String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

state

public long state

Can be any long value.

Constructor Detail

DistinctRNG

public DistinctRNG()

Creates a new generator seeded using Math.random.

DistinctRNG

public DistinctRNG(long seed)

Method Detail

setSeed

public void setSeed(long seed)

This initializes the 1 state of the generator to random values based on the given seed. (2 to the 64) possible initial generator states can be produced here, all with a different first value returned by nextLong() (because stateA is guaranteed to be different for every different seed).

Parameters:

seed - the initial seed; may be any long

getState

public long getState()

Description copied from interface: StatefulRandomness

Get the current internal state of the StatefulRandomness as a long.

Specified by:

getState in interface StatefulRandomness

Returns:

the current internal state of this object.

setState

public void setState(long state)

Description copied from interface: StatefulRandomness

Set the current internal state of this StatefulRandomness with a long.

Specified by:

setState in interface StatefulRandomness

Parameters:

state - a 64-bit long. You should avoid passing 0, even though some implementations can handle that.

next

public int next(int bits)

Using this method, any algorithm that might use the built-in Java Random can interface with this randomness source.

Specified by:

next in interface RandomnessSource

Parameters:

bits - the number of bits to be returned

Returns:

the integer containing the appropriate number of bits

nextLong

public long nextLong()

Using this method, any algorithm that needs to efficiently generate more than 32 bits of random data can interface with this randomness source.

Get a random long between Long.MIN_VALUE and Long.MAX_VALUE (both inclusive).

Specified by:

nextLong in interface RandomnessSource

Returns:

a random long between Long.MIN_VALUE and Long.MAX_VALUE (both inclusive)

skip

public long skip(long advance)

Description copied from interface: SkippingRandomness

Advances or rolls back the SkippingRandomness' state without actually generating each number. Skips forward or backward a number of steps specified by advance, where a step is equal to one call to RandomnessSource.nextLong(), and returns the random number produced at that step. Negative numbers can be used to step backward, or 0 can be given to get the most-recently-generated long from RandomnessSource.nextLong().

Specified by:

skip in interface SkippingRandomness

Parameters:

advance - Number of future generations to skip over; can be negative to backtrack, 0 gets the most-recently-generated number

Returns:

the random long generated after skipping forward or backwards by advance numbers

copy

public DistinctRNG copy()

Produces a copy of this RandomnessSource that, if next() and/or nextLong() are called on this object and the copy, both will generate the same sequence of random numbers from the point copy() was called. This just need to copy the state so it isn't shared, usually, and produce a new value with the same exact state.

Specified by:

copy in interface RandomnessSource

Specified by:

copy in interface StatefulRandomness

Returns:

a copy of this RandomnessSource

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

equals

public boolean equals(java.lang.Object o)

Overrides:

equals in class java.lang.Object

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object