com.badlogic.gdx.math

Class RandomXS128

java.lang.Object

java.util.Random

com.badlogic.gdx.math.RandomXS128

All Implemented Interfaces:

Serializable

public class RandomXS128
extends Random

This class implements the xorshift128+ algorithm that is a very fast, top-quality 64-bit pseudo-random number generator. The quality of this PRNG is much higher than Random's, and its cycle length is 2¹²⁸ − 1, which is more than enough for any single-thread application. More details and algorithms can be found here.

Instances of RandomXS128 are not thread-safe.

Author:

Inferno, davebaol

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
RandomXS128() Creates a new random number generator.
RandomXS128(long seed) Creates a new random number generator using a single long seed.
RandomXS128(long seed0, long seed1) Creates a new random number generator using two long seeds.

Method Summary

Methods

Modifier and Type	Method and Description
long	getState(int seed) Returns the internal seeds to allow state saving.
boolean	nextBoolean() Returns a pseudo-random, uniformly distributed boolean value from this random number generator's sequence.
void	nextBytes(byte[] bytes) Generates random bytes and places them into a user-supplied byte array.
double	nextDouble() Returns a pseudo-random, uniformly distributed double value between 0.0 and 1.0from this random number generator's sequence.
float	nextFloat() Returns a pseudo-random, uniformly distributed float value between 0.0 and 1.0 from this random number generator's sequence.
int	nextInt() Returns the next pseudo-random, uniformly distributed int value from this random number generator's sequence.
int	nextInt(int n) Returns a pseudo-random, uniformly distributed int value between 0 (inclusive) and the specified value (exclusive), drawn from this random number generator's sequence.
long	nextLong() Returns the next pseudo-random, uniformly distributed long value from this random number generator's sequence.
long	nextLong(long n) Returns a pseudo-random, uniformly distributed long value between 0 (inclusive) and the specified value (exclusive), drawn from this random number generator's sequence.
void	setSeed(long seed) Sets the internal seed of this generator based on the given long value.
void	setState(long seed0, long seed1) Sets the internal state of this generator.

Methods inherited from class java.util.Random

nextGaussian

Methods inherited from class java.lang.Object

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

Constructor Detail

RandomXS128

public RandomXS128()

Creates a new random number generator. This constructor sets the seed of the random number generator to a value very likely to be distinct from any other invocation of this constructor.

This implementation creates a Random instance to generate the initial seed.

RandomXS128

public RandomXS128(long seed)

Creates a new random number generator using a single long seed.

Parameters:

seed - the initial seed

RandomXS128

public RandomXS128(long seed0,
           long seed1)

Creates a new random number generator using two long seeds.

Parameters:

seed0 - the first part of the initial seed

seed1 - the second part of the initial seed

Method Detail

nextLong

public long nextLong()

Returns the next pseudo-random, uniformly distributed long value from this random number generator's sequence.

Subclasses should override this, as this is used by all other methods.

Overrides:

nextLong in class Random

nextInt

public int nextInt()

Returns the next pseudo-random, uniformly distributed int value from this random number generator's sequence.

This implementation uses nextLong() internally.

Overrides:

nextInt in class Random

nextInt

public int nextInt(int n)

Returns a pseudo-random, uniformly distributed int value between 0 (inclusive) and the specified value (exclusive), drawn from this random number generator's sequence.

This implementation uses nextLong() internally.

Overrides:

nextInt in class Random

Parameters:

n - the positive bound on the random number to be returned.

Returns:

the next pseudo-random int value between 0 (inclusive) and n (exclusive).

nextLong

public long nextLong(long n)

Returns a pseudo-random, uniformly distributed long value between 0 (inclusive) and the specified value (exclusive), drawn from this random number generator's sequence. The algorithm used to generate the value guarantees that the result is uniform, provided that the sequence of 64-bit values produced by this generator is.

This implementation uses nextLong() internally.

Parameters:

n - the positive bound on the random number to be returned.

Returns:

the next pseudo-random long value between 0 (inclusive) and n (exclusive).

nextDouble

public double nextDouble()

Returns a pseudo-random, uniformly distributed double value between 0.0 and 1.0from this random number generator's sequence.

This implementation uses nextLong() internally.

Overrides:

nextDouble in class Random

nextFloat

public float nextFloat()

Returns a pseudo-random, uniformly distributed float value between 0.0 and 1.0 from this random number generator's sequence.

This implementation uses nextLong() internally.

Overrides:

nextFloat in class Random

nextBoolean

public boolean nextBoolean()

Returns a pseudo-random, uniformly distributed boolean value from this random number generator's sequence.

This implementation uses nextLong() internally.

Overrides:

nextBoolean in class Random

nextBytes

public void nextBytes(byte[] bytes)

Generates random bytes and places them into a user-supplied byte array. The number of random bytes produced is equal to the length of the byte array.

This implementation uses nextLong() internally.

Overrides:

nextBytes in class Random

setSeed

public void setSeed(long seed)

Sets the internal seed of this generator based on the given long value.

The given seed is passed twice through an hash function. This way, if the user passes a small value we avoid the short irregular transient associated with states having a very small number of bits set.

Overrides:

setSeed in class Random

Parameters:

seed - a nonzero seed for this generator (if zero, the generator will be seeded with Long.MIN_VALUE).

setState

public void setState(long seed0,
            long seed1)

Sets the internal state of this generator.

Parameters:

seed0 - the first part of the internal state

seed1 - the second part of the internal state

getState

public long getState(int seed)

Returns the internal seeds to allow state saving.

Parameters:

seed - muse be 0 or 1, designating which of the 2 long seeds to return

Returns:

the internal seed that can be used in setState