org.apache.commons.math3.random

Class BitsStreamGenerator

java.lang.Object

org.apache.commons.math3.random.BitsStreamGenerator

All Implemented Interfaces:

java.io.Serializable, RandomGenerator

Direct Known Subclasses:

AbstractWell, ISAACRandom, MersenneTwister

public abstract class BitsStreamGenerator
extends java.lang.Object
implements RandomGenerator, java.io.Serializable

Base class for random number generators that generates bits streams.

Since:

2.0

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
private double	nextGaussian Next gaussian.
private static long	serialVersionUID Serializable version identifier

Constructor Summary

Constructors

Constructor and Description
BitsStreamGenerator() Creates a new random number generator.

Method Summary

Methods

Modifier and Type	Method and Description
void	clear() Clears the cache used by the default implementation of nextGaussian.
protected abstract int	next(int bits) Generate next pseudorandom number.
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 array.
void	nextBytes(byte[] bytes, int start, int len) Generates random bytes and places them into a user-supplied array.
private void	nextBytesFill(byte[] bytes, int start, int len) Generates random bytes and places them into a user-supplied 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 long value between 0 (inclusive) and the specified value (exclusive), drawn from this random number generator's sequence.
abstract void	setSeed(int seed) Sets the seed of the underlying random number generator using an int seed.
abstract void	setSeed(int[] seed) Sets the seed of the underlying random number generator using an int array seed.
abstract void	setSeed(long seed) Sets the seed of the underlying random number generator using a long seed.

Methods inherited from class java.lang.Object

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

Field Detail

serialVersionUID

private static final long serialVersionUID

Serializable version identifier

See Also:

Constant Field Values

nextGaussian

private double nextGaussian

Next gaussian.

Constructor Detail

BitsStreamGenerator

public BitsStreamGenerator()

Creates a new random number generator.

Method Detail

setSeed

public abstract 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 abstract 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

setSeed

public abstract 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

next

protected abstract int next(int bits)

Generate next pseudorandom number.

This method is the core generation algorithm. It is used by all the public generation methods for the various primitive types nextBoolean(), nextBytes(byte[]), nextDouble(), nextFloat(), nextGaussian(), nextInt(), next(int) and nextLong().

Parameters:

bits - number of random bits to produce

Returns:

random bits generated

nextBoolean

public boolean nextBoolean()

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

Specified by:

nextBoolean in interface RandomGenerator

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.

Specified by:

nextDouble in interface RandomGenerator

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.

Specified by:

nextFloat in interface RandomGenerator

Returns:

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

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

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

nextInt

public int nextInt(int n)
            throws java.lang.IllegalArgumentException

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

This default implementation is copied from Apache Harmony java.util.Random (r929253).

Implementation notes:

• If n is a power of 2, this method returns (int) ((n * (long) next(31)) >> 31).
• If n is not a power of 2, what is returned is next(31) % n with next(31) values rejected (i.e. regenerated) until a value that is larger than the remainder of Integer.MAX_VALUE / n is generated. Rejection of this initial segment is necessary to ensure a uniform distribution.

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:

java.lang.IllegalArgumentException - if n is not positive.

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.

Specified by:

nextLong in interface RandomGenerator

Returns:

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

nextLong

public long nextLong(long n)
              throws java.lang.IllegalArgumentException

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

Parameters:

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

Returns:

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

Throws:

java.lang.IllegalArgumentException - if n is not positive.

clear

public void clear()

Clears the cache used by the default implementation of nextGaussian.

nextBytes

public void nextBytes(byte[] bytes)

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

The array is filled with bytes extracted from random integers. This implies that the number of random bytes generated may be larger than the length of the byte array.

Specified by:

nextBytes in interface RandomGenerator

Parameters:

bytes - Array in which to put the generated bytes. Cannot be null.

nextBytes

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

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

The array is filled with bytes extracted from random integers. This implies that the number of random bytes generated may be larger than the length of the byte array.

Parameters:

bytes - Array in which to put the generated bytes. Cannot be null.

start - Index at which to start inserting the generated bytes.

len - Number of bytes to insert.

Throws:

OutOfRangeException - if start < 0 or start >= bytes.length.

OutOfRangeException - if len < 0 or len > bytes.length - start.

nextBytesFill

private void nextBytesFill(byte[] bytes,
                 int start,
                 int len)

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

The array is filled with bytes extracted from random integers. This implies that the number of random bytes generated may be larger than the length of the byte array.

Parameters:

bytes - Array in which to put the generated bytes. Cannot be null.

start - Index at which to start inserting the generated bytes.

len - Number of bytes to insert.