Package org.hipparchus.random

Class 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

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      protected void clearCache()
      Clears the cache used by the default implementation of 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()

    • Constructor Detail

      • 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 Detail

      • 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 nextGaussian.