Package org.hipparchus.random

Class MersenneTwister

java.lang.Object

org.hipparchus.random.MersenneTwister

All Implemented Interfaces:

Serializable, RandomGenerator

public class MersenneTwister
extends Object
implements Serializable

This class implements a powerful pseudo-random number generator developed by Makoto Matsumoto and Takuji Nishimura during 1996-1997.

Caveat: It is recommended to use one of WELL generators rather than the MersenneTwister generator (see this paper for more information).

This generator features an extremely long period (2¹⁹⁹³⁷-1) and 623-dimensional equidistribution up to 32 bits accuracy. The home page for this generator is located at http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html.

This generator is described in a paper by Makoto Matsumoto and Takuji Nishimura in 1998: Mersenne Twister: A 623-Dimensionally Equidistributed Uniform Pseudo-Random Number Generator, ACM Transactions on Modeling and Computer Simulation, Vol. 8, No. 1, January 1998, pp 3--30.

This class is mainly a Java port of the 2002-01-26 version of the generator written in C by Makoto Matsumoto and Takuji Nishimura. Here is their original copyright:

Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji Nishimura, All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
3. The names of its contributors may not be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

See Also:

• Serialized Form

Constructor Summary

Constructors

Constructor	Description
MersenneTwister()	Creates a new random number generator.
MersenneTwister(int seed)	Creates a new random number generator using a single int seed.
MersenneTwister(int[] seed)	Creates a new random number generator using an int array seed.
MersenneTwister(long seed)	Creates a new 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)	Reinitialize the generator as if just built with the given int seed.
void	setSeed(int[] seed)	Reinitialize the generator as if just built with the given 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

MersenneTwister

public MersenneTwister()

Creates a new random number generator.

The instance is initialized using the current time plus the system identity hash code of this instance as the seed.

MersenneTwister

public MersenneTwister(int seed)

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

Parameters:

seed - the initial seed (32 bits integer)

MersenneTwister

public MersenneTwister(int[] seed)

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

Parameters:

seed - the initial seed (32 bits integers array), if null the seed of the generator will be related to the current time

MersenneTwister

public MersenneTwister(long seed)

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

Parameters:

seed - the initial seed (64 bits integer)

Method Details

setSeed

public void setSeed(int seed)

Reinitialize the generator as if just built with the given int seed.

The state of the generator is exactly the same as a new generator built with the same seed.

Specified by:

setSeed in interface RandomGenerator

Parameters:

seed - the initial seed (32 bits integer)

setSeed

public void setSeed(int[] seed)

Reinitialize the generator as if just built with the given int array seed.

The state of the generator is exactly the same as a new generator built with the same seed.

Specified by:

setSeed in interface RandomGenerator

Parameters:

seed - the initial seed (32 bits integers array), if null the seed of the generator will be the current system time plus the system identity hash code of this instance

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(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