RandomStreamBase
umontreal.iro.lecuyer.rng

Class RandomStreamBase

  • All Implemented Interfaces:
    Serializable, Cloneable, CloneableRandomStream, RandomStream
    Direct Known Subclasses:
    F2NL607, GenF2w32, LFSR113, LFSR258, MRG31k3p, MRG32k3a, MRG32k3aL, MT19937, RandRijndael, WELL1024, WELL512, WELL607


    public abstract class RandomStreamBaseextends Objectimplements CloneableRandomStream, Serializable
    This class provides a convenient foundation on which RNGs can be built. It implements all the methods which do not depend directly on the generator itself, but only on its output, which is to be defined by implementing the abstract method nextValue. In the present class, all methods returning random numbers directly or indirectly (nextDouble, nextArrayOfDouble, nextInt and nextArrayOfInt) call nextValue. Thus, to define a subclass that implements a RNG, it suffices to implement nextValue, in addition to the reset... and toString methods. Of course, the other methods may also be overridden for improved efficiency.

    If the nextValue already generates numbers with a precision of 53-bits or higher, then nextDouble can be overridden to improve the performance. The mechanism for increasing the precision assumes that nextValue returns at least 29 bits of precision, in which case the higher precision numbers will have roughly 52 bits of precision. This mechanism was designed primarily for RNGs that return numbers with around 30 to 32 bits of precision.

    RandomStreamBase and its subclasses are implementing the Serializable interface. Each class has a serial number wich represent the class version. For instance 70510 means that the last change was the 10th May 2007.

    See Also:
    Serialized Form
    • Constructor Summary

      Constructors 
      Constructor and Description
      RandomStreamBase() 
    • Method Summary

      Methods 
      Modifier and TypeMethod and Description
      RandomStreamBaseclone()
      Clones the current generator and return its copy.
      StringformatState()
      Deprecated. 
      StringformatStateFull()
      Deprecated. 
      voidincreasedPrecision(boolean incp)
      After calling this method with incp = true, each call to the RNG (direct or indirect) for this stream will return a uniform random number with more bits of precision than what is returned by nextValue, and will advance the state of the stream by 2 steps instead of 1 (i.e., nextValue will be called twice for each random number).
      voidnextArrayOfDouble(double[] u, int start, int n)
      Calls nextDouble n times to fill the array u.
      voidnextArrayOfInt(int i, int j, int[] u, int start, int n)
      Calls nextInt n times to fill the array u.
      doublenextDouble()
      Returns a uniform random number between 0 and 1 from the stream.
      intnextInt(int i, int j)
      Calls nextDouble once to create one integer between i and j.
      abstract voidresetNextSubstream()
      Reinitializes the stream to the beginning of its next substream: Ng is computed, and Cg and Bg are set to Ng.
      abstract voidresetStartStream()
      Reinitializes the stream to its initial state Ig: Cg and Bg are set to Ig.
      abstract voidresetStartSubstream()
      Reinitializes the stream to the beginning of its current substream: Cg is set to Bg.
      abstract StringtoString()
      Returns a string containing the current state of this stream.
    • Constructor Detail

      • RandomStreamBase

        public RandomStreamBase()
    • Method Detail

      • resetStartStream

        public abstract void resetStartStream()
        Description copied from interface: RandomStream
        Reinitializes the stream to its initial state Ig: Cg and Bg are set to Ig.
        Specified by:
        resetStartStream in interface RandomStream
      • resetStartSubstream

        public abstract void resetStartSubstream()
        Description copied from interface: RandomStream
        Reinitializes the stream to the beginning of its current substream: Cg is set to Bg.
        Specified by:
        resetStartSubstream in interface RandomStream
      • resetNextSubstream

        public abstract void resetNextSubstream()
        Description copied from interface: RandomStream
        Reinitializes the stream to the beginning of its next substream: Ng is computed, and Cg and Bg are set to Ng.
        Specified by:
        resetNextSubstream in interface RandomStream
      • toString

        public abstract String toString()
        Description copied from interface: RandomStream
        Returns a string containing the current state of this stream.
        Specified by:
        toString in interface RandomStream
        Overrides:
        toString in class Object
        Returns:
        the state of the generator formated as a string
      • increasedPrecision

        public void increasedPrecision(boolean incp)
        After calling this method with incp = true, each call to the RNG (direct or indirect) for this stream will return a uniform random number with more bits of precision than what is returned by nextValue, and will advance the state of the stream by 2 steps instead of 1 (i.e., nextValue will be called twice for each random number).

        More precisely, if s is a stream of a subclass of RandomStreamBase, when the precision has been increased, the instruction ``u = s.nextDouble()'', is equivalent to ``u = (s.nextValue() + s.nextValue()*fact) % 1.0'' where the constant fact is equal to 2-24. This also applies when calling nextDouble indirectly (e.g., via nextInt, etc.). By default, or if this method is called again with incp = false, each call to nextDouble for this stream advances the state by 1 step and returns the same number as nextValue.

        Parameters:
        incp - if the generator will be set to high precision mode
      • nextDouble

        public double nextDouble()
        Returns a uniform random number between 0 and 1 from the stream. Its behavior depends on the last call to increasedPrecision. The generators programmed in SSJ never return the values 0 or 1.
        Specified by:
        nextDouble in interface RandomStream
        Returns:
        a number in the interval (0,1)
      • nextArrayOfDouble

        public void nextArrayOfDouble(double[] u,                     int start,                     int n)
        Calls nextDouble n times to fill the array u.
        Specified by:
        nextArrayOfDouble in interface RandomStream
        Parameters:
        u - the array in which the numbers will be stored
        start - the first index of u to be used
        n - the number of random numbers to put in u
      • nextInt

        public int nextInt(int i,          int j)
        Calls nextDouble once to create one integer between i and j. This method always uses the highest order bits of the random number. It should be overridden if a faster implementation exists for the specific generator.
        Specified by:
        nextInt in interface RandomStream
        Parameters:
        i - the smallest possible returned integer
        j - the largest possible returned integer
        Returns:
        a random integer between i and j
      • nextArrayOfInt

        public void nextArrayOfInt(int i,                  int j,                  int[] u,                  int start,                  int n)
        Calls nextInt n times to fill the array u. This method should be overridden if a faster implementation exists for the specific generator.
        Specified by:
        nextArrayOfInt in interface RandomStream
        Parameters:
        i - the smallest possible integer to put in u
        j - the largest possible integer to put in u
        u - the array in which the numbers will be stored
        start - the first index of u to be used
        n - the number of random numbers to put in u
      • formatState

        @Deprecatedpublic String formatState()
        Deprecated. 
        Use the toString method.

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