LFSR258
umontreal.iro.lecuyer.rng

Class LFSR258

  • All Implemented Interfaces:
    Serializable, Cloneable, CloneableRandomStream, RandomStream


    public class LFSR258extends RandomStreamBase
    Extends RandomStreamBase using a 64-bit composite linear feedback shift register (LFSR) (or Tausworthe) RNG as defined in. This generator is the LFSR258 proposed in. It has five components combined by a bitwise xor. Its period length is approximatively 2^258 . The values of V, W and Z are 2100, 2100 and 2200 respectively (see RandomStream for their definition). The seed of the RNG, and the state of a stream at any given step, are five-dimensional vectors of 32-bit integers. The default initial seed of the RNG is (1234567890, 1234567890, 1234567890, 1234567890, 1234567890). The nextValue method returns numbers with 53 bits of precision. This generator is fast for 64-bit machines.
    See Also:
    Serialized Form
    • Constructor Detail

      • LFSR258

        public LFSR258()
        Constructs a new stream.
      • LFSR258

        public LFSR258(String name)
        Constructs a new stream with the identifier name.
        Parameters:
        name - name of the stream
    • Method Detail

      • setPackageSeed

        public static void setPackageSeed(long[] seed)
        Sets the initial seed for the class LFSR258 to the five integers of array seed[0..4]. This will be the initial state (or seed) of the next created stream. The default seed for the first stream is (1234567890, 1234567890, 1234567890, 1234567890, 1234567890). The first, second, third, fourth and fifth integers of seed must be either negative, or greater than or equal to 2, 512, 4096, 131072 and 8388608 respectively.
        Parameters:
        seed - array of 5 elements representing the seed
      • setSeed

        public void setSeed(long[] seed)
        This method is discouraged for normal use. Initializes the stream at the beginning of a stream with the initial seed seed[0..4]. The seed must satisfy the same conditions as in setPackageSeed. This method only affects the specified stream; the others are not modified, so the beginning of the streams will not be spaced Z values apart. For this reason, this method should only be used in very exceptional cases; proper use of the reset... methods and of the stream constructor is preferable.
        Parameters:
        seed - array of 5 elements representing the seed
      • getState

        public long[] getState()
        Returns the current state of the stream, represented as an array of five integers.
        Returns:
        the current state of the stream
      • nextInt

        public int nextInt(int i,          int j)
        Description copied from class: RandomStreamBase
        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
        Overrides:
        nextInt in class RandomStreamBase
        Parameters:
        i - the smallest possible returned integer
        j - the largest possible returned integer
        Returns:
        a random integer between i and j

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