Package org.hipparchus.random

Class ISAACRandom

java.lang.Object

org.hipparchus.random.ISAACRandom

All Implemented Interfaces:

Serializable, RandomGenerator

public class ISAACRandom
extends Object
implements Serializable

A fast cryptographic pseudo-random number generator.

ISAAC (Indirection, Shift, Accumulate, Add, and Count) generates 32-bit random numbers. ISAAC has been designed to be cryptographically secure and is inspired by RC4. Cycles are guaranteed to be at least 2⁴⁰ values long, and they are 2⁸²⁹⁵ values long on average. The results are uniformly distributed, unbiased, and unpredictable unless you know the seed.

This code is based (with minor changes and improvements) on the original implementation of the algorithm by Bob Jenkins.

See Also:

• ISAAC: a fast cryptographic pseudo-random number generator
• Serialized Form

Constructor Summary

Constructors

Constructor	Description
ISAACRandom()	Creates a new ISAAC random number generator.
ISAACRandom(int[] seed)	Creates a new ISAAC random number generator using an int array seed.
ISAACRandom(long seed)	Creates a new ISAAC random number generator using a single long seed.

Method Summary

Modifier and Type	Method	Description
protected void	clearCache()	Clears the cache used by the default implementation of RandomGenerator.nextGaussian().
boolean	nextBoolean()	Returns the next pseudorandom, 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.
void	nextBytes(byte[] bytes, int start, int len)	Generates random bytes and places them into a user-supplied byte array.
double	nextDouble()	Returns the next pseudorandom, uniformly distributed double value between 0.0 and 1.0 from this random number generator's sequence.
float	nextFloat()	Returns the next pseudorandom, uniformly distributed float value between 0.0 and 1.0 from this random number generator's sequence.
double	nextGaussian()	Returns the next pseudorandom, Gaussian ("normally") distributed double value with mean 0.0 and standard deviation 1.0 from this random number generator's sequence.
int	nextInt()	Returns the next pseudorandom, uniformly distributed int value from this random number generator's sequence.
int	nextInt(int n)	Returns a pseudorandom, 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 pseudorandom, uniformly distributed long value from this random number generator's sequence.
long	nextLong(long n)	Returns a pseudorandom, uniformly distributed int value between 0 (inclusive) and the specified value (exclusive), drawn from this random number generator's sequence.
void	setSeed(int seed)	Sets the seed of the underlying random number generator using an int seed.
void	setSeed(int[] seed)	Sets the seed of the underlying random number generator using an int array seed.
void	setSeed(long seed)	Sets the seed of the underlying random number generator using a long seed.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Details

ISAACRandom

public ISAACRandom()

Creates a new ISAAC random number generator.
The instance is initialized using a combination of the current time and system hash code of the instance as the seed.

ISAACRandom

public ISAACRandom(long seed)

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

Parameters:

seed - Initial seed.

ISAACRandom

public ISAACRandom(int[] seed)

Creates a new ISAAC random number generator using an int array seed.

Parameters:

seed - Initial seed. If null, the seed will be related to the current time.

Method Details

setSeed

public void setSeed(int[] seed)

Sets the seed of the underlying random number generator using an int array seed.

Sequences of values generated starting with the same seeds should be identical.

Specified by:

setSeed in interface RandomGenerator

Parameters:

seed - the seed value

nextInt

public int nextInt()

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

All 2³² possible int values should be produced with (approximately) equal probability.

Specified by:

nextInt in interface RandomGenerator

Returns:

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

nextBoolean

public boolean nextBoolean()

Returns the next pseudorandom, uniformly distributed boolean value from this random number generator's sequence.

Returns:

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

nextDouble

public double nextDouble()

Returns the next pseudorandom, uniformly distributed double value between 0.0 and 1.0 from this random number generator's sequence.

Returns:

the next pseudorandom, uniformly distributed double value between 0.0 and 1.0 from this random number generator's sequence

nextFloat

public float nextFloat()

Returns the next pseudorandom, uniformly distributed float value between 0.0 and 1.0 from this random number generator's sequence.

Returns:

the next pseudorandom, uniformly distributed float value between 0.0 and 1.0 from this random number generator's sequence

nextLong

public long nextLong()

Returns the next pseudorandom, uniformly distributed long value from this random number generator's sequence. All 2⁶⁴ possible long values should be produced with (approximately) equal probability.

Returns:

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

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.

Parameters:

bytes - the non-null byte array in which to put the random bytes

nextBytes

public void nextBytes(byte[] bytes,
 int start,
 int len)

Generates random bytes and places them into a user-supplied byte array.

Parameters:

bytes - the non-null byte array in which to put the random bytes

start - the starting index for inserting the generated bytes into the array

len - the number of bytes to generate

setSeed

public void setSeed(int seed)

Sets the seed of the underlying random number generator using an int seed.

Sequences of values generated starting with the same seeds should be identical.

Specified by:

setSeed in interface RandomGenerator

Parameters:

seed - the seed value

setSeed

public void setSeed(long seed)

Sets the seed of the underlying random number generator using a long seed.

Sequences of values generated starting with the same seeds should be identical.

Specified by:

setSeed in interface RandomGenerator

Parameters:

seed - the seed value

nextInt

public int nextInt(int n)
            throws IllegalArgumentException

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

Specified by:

nextInt in interface RandomGenerator

Parameters:

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

Returns:

a pseudorandom, uniformly distributed int value between 0 (inclusive) and n (exclusive).

Throws:

IllegalArgumentException - if n is not positive.

nextLong

public long nextLong(long n)

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

Specified by:

nextLong in interface RandomGenerator

Parameters:

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

Returns:

a pseudorandom, uniformly distributed int value between 0 (inclusive) and n (exclusive).

nextGaussian

public double nextGaussian()

Returns the next pseudorandom, Gaussian ("normally") distributed double value with mean 0.0 and standard deviation 1.0 from this random number generator's sequence.

Specified by:

nextGaussian in interface RandomGenerator

Returns:

the next pseudorandom, Gaussian ("normally") distributed double value with mean 0.0 and standard deviation 1.0 from this random number generator's sequence

clearCache

protected void clearCache()

Clears the cache used by the default implementation of RandomGenerator.nextGaussian().

toString

public String toString()

Overrides:

toString in class Object