Class MersenneTwister

  • All Implemented Interfaces:
    RandomIntSource, RestorableUniformRandomProvider, UniformRandomProvider

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

    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:

    Mersenne Twister licence
    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.
    Since:
    1.0
    See Also:
    Mersenne Twister (Wikipedia)
    • Field Detail

      • INT_MASK_LONG

        private static final long INT_MASK_LONG
        Mask 32 most significant bits.
        See Also:
        Constant Field Values
      • UPPER_MASK_LONG

        private static final long UPPER_MASK_LONG
        Most significant w-r bits.
        See Also:
        Constant Field Values
      • LOWER_MASK_LONG

        private static final long LOWER_MASK_LONG
        Least significant r bits.
        See Also:
        Constant Field Values
      • UPPER_MASK

        private static final int UPPER_MASK
        Most significant w-r bits.
        See Also:
        Constant Field Values
      • LOWER_MASK

        private static final int LOWER_MASK
        Least significant r bits.
        See Also:
        Constant Field Values
      • MAG01

        private static final int[] MAG01
        X * MATRIX_A for X = {0, 1}.
      • mt

        private final int[] mt
        Bytes pool.
      • mti

        private int mti
        Current index in the bytes pool.
    • Constructor Detail

      • MersenneTwister

        public MersenneTwister​(int[] seed)
        Creates a new random number generator.
        Parameters:
        seed - Initial seed.
    • Method Detail

      • getStateInternal

        protected byte[] getStateInternal()
        Creates a snapshot of the RNG state.
        Overrides:
        getStateInternal in class IntProvider
        Returns:
        the internal state.
      • setSeedInternal

        private void setSeedInternal​(int[] seed)
        Initializes the generator with the given seed.
        Parameters:
        seed - Initial seed.
      • fillStateMersenneTwister

        private static void fillStateMersenneTwister​(int[] state,
                                                     int[] inputSeed)
        Utility for wholly filling a state array with non-zero bytes, even if the seed has a smaller size. The procedure is the one defined by the standard implementation of the algorithm.
        Parameters:
        state - State to be filled (must be allocated).
        inputSeed - Seed (cannot be null).
      • initializeState

        private static void initializeState​(int[] state)
        Fill the state using a defined pseudo-random sequence.
        Parameters:
        state - State to be filled (must be allocated).
      • mixSeedAndState

        private static int mixSeedAndState​(int[] state,
                                           int[] seed)
        Mix the seed into the state using a non-linear combination. The procedure uses k steps where k = max(state.length, seed.length). If the seed is smaller than the state it is wrapped to obtain enough values. If the seed is larger than the state then the procedure visits entries in the state multiple times.

        Returns the index immediately after the most recently visited position in the state array.

        Parameters:
        state - State to be filled (must be allocated).
        seed - Seed (must be at least length 1).
        Returns:
        the next index
      • mixState

        private static void mixState​(int[] state,
                                     int startIndex)
        Mix each position of the state using a non-linear combination. The procedure starts from the specified index in the state array and wraps iteration through the array if required.
        Parameters:
        state - State to be filled (must be allocated).
        startIndex - The index to begin within the state array.
      • next

        public int next()
        Return the next random value.
        Returns:
        the next random value.