Package org.hipparchus.random

Class ISAACRandom

  • All Implemented Interfaces:
    Serializable, RandomGenerator
    public class ISAACRandom
extends Object
implements Serializable
    A fast cryptographic pseudo-random number generator.

    ISAAC (Indirection, Shift, Accumulate, Add, and Count) generates 32-bit random numbers. ISAAC has been designed to be cryptographically secure and is inspired by RC4. Cycles are guaranteed to be at least 240 values long, and they are 28295 values long on average. The results are uniformly distributed, unbiased, and unpredictable unless you know the seed.

    This code is based (with minor changes and improvements) on the original implementation of the algorithm by Bob Jenkins.

    See Also:
    ISAAC: a fast cryptographic pseudo-random number generator, Serialized Form

    • Constructor Summary

      Constructors 
      Constructor Description
      ISAACRandom()
      Creates a new ISAAC random number generator.
      ISAACRandom​(int[] seed)
      Creates a new ISAAC random number generator using an int array seed.
      ISAACRandom​(long seed)
      Creates a new ISAAC 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)
      Sets the seed of the underlying random number generator using an int seed.
      void setSeed​(int[] seed)
      Sets the seed of the underlying random number generator using an int array seed.
      void setSeed​(long seed)
      Sets the seed of the underlying random number generator using a long seed.
      String toString()

    • Constructor Detail

      • ISAACRandom

        public ISAACRandom()
        Creates a new ISAAC random number generator.
        The instance is initialized using a combination of the current time and system hash code of the instance as the seed.

      • ISAACRandom

        public ISAACRandom​(long seed)
        Creates a new ISAAC random number generator using a single long seed.
        Parameters:
        seed - Initial seed.

      • ISAACRandom

        public ISAACRandom​(int[] seed)
        Creates a new ISAAC random number generator using an int array seed.
        Parameters:
        seed - Initial seed. If null, the seed will be related to the current time.

    • Method Detail

      • setSeed

        public void setSeed​(int[] seed)
        Sets the seed of the underlying random number generator using an int array 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()
        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​(int seed)
        Sets the seed of the underlying random number generator using an int seed.

        Sequences of values generated starting with the same seeds should be identical.

        Specified by:
        setSeed in interface RandomGenerator
        Parameters:
        seed - the seed value

      • 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.