Package it.unimi.dsi.util

Class XorShift1024StarPhiRandomGenerator

  • All Implemented Interfaces:
    Serializable, org.apache.commons.math3.random.RandomGenerator
    public class XorShift1024StarPhiRandomGenerator
extends org.apache.commons.math3.random.AbstractRandomGenerator
implements Serializable
    A fast, high-quality pseudorandom number generator that combines a long-period instance of George Marsaglia's Xorshift generators (described in “Xorshift RNGs”, Journal of Statistical Software, 8:1−6, 2003) with a multiplication. More information can be found at our PRNG page.

    By using the supplied jump() method it is possible to generate non-overlapping long sequences for parallel computations. This class provides also a split() method to support recursive parallel computations, in the spirit of SplittableRandom.

    Note that this is not a secure generator.

    See Also:
    it.unimi.dsi.util, Random, XorShift1024StarPhiRandom, Serialized Form

    • Constructor Detail

      • XorShift1024StarPhiRandomGenerator

        public XorShift1024StarPhiRandomGenerator()
        Creates a new generator seeded using Util.randomSeed().

      • XorShift1024StarPhiRandomGenerator

        public XorShift1024StarPhiRandomGenerator​(long seed)
        Creates a new generator using a given seed.
        Parameters:
        seed - a seed for the generator.

    • Method Detail

      • nextLong

        public long nextLong()
        Specified by:
        nextLong in interface org.apache.commons.math3.random.RandomGenerator
        Overrides:
        nextLong in class org.apache.commons.math3.random.AbstractRandomGenerator

      • nextInt

        public int nextInt()
        Specified by:
        nextInt in interface org.apache.commons.math3.random.RandomGenerator
        Overrides:
        nextInt in class org.apache.commons.math3.random.AbstractRandomGenerator

      • nextInt

        public int nextInt​(int n)
        Specified by:
        nextInt in interface org.apache.commons.math3.random.RandomGenerator
        Overrides:
        nextInt in class org.apache.commons.math3.random.AbstractRandomGenerator

      • nextLong

        public long nextLong​(long n)
        Returns a pseudorandom uniformly distributed long value between 0 (inclusive) and the specified value (exclusive), drawn from this random number generator's sequence. The algorithm used to generate the value guarantees that the result is uniform, provided that the sequence of 64-bit values produced by this generator is.
        Parameters:
        n - the positive bound on the random number to be returned.
        Returns:
        the next pseudorandom long value between 0 (inclusive) and n (exclusive).

      • nextDouble

        public double nextDouble()
        Specified by:
        nextDouble in interface org.apache.commons.math3.random.RandomGenerator
        Specified by:
        nextDouble in class org.apache.commons.math3.random.AbstractRandomGenerator

      • nextDoubleFast

        public double nextDoubleFast()
        Returns the next pseudorandom, uniformly distributed double value between 0.0 and 1.0 from this random number generator's sequence, using a fast multiplication-free method which, however, can provide only 52 significant bits.

        This method is faster than nextDouble(), but it can return only dyadic rationals of the form k / 2−52, instead of the standard k / 2−53.

        The only difference between the output of this method and that of nextDouble() is an additional least significant bit set in half of the returned values. For most applications, this difference is negligible.

        Returns:
        the next pseudorandom, uniformly distributed double value between 0.0 and 1.0 from this random number generator's sequence, using 52 significant bits only.

      • nextFloat

        public float nextFloat()
        Specified by:
        nextFloat in interface org.apache.commons.math3.random.RandomGenerator
        Overrides:
        nextFloat in class org.apache.commons.math3.random.AbstractRandomGenerator

      • nextBoolean

        public boolean nextBoolean()
        Specified by:
        nextBoolean in interface org.apache.commons.math3.random.RandomGenerator
        Overrides:
        nextBoolean in class org.apache.commons.math3.random.AbstractRandomGenerator

      • nextBytes

        public void nextBytes​(byte[] bytes)
        Specified by:
        nextBytes in interface org.apache.commons.math3.random.RandomGenerator
        Overrides:
        nextBytes in class org.apache.commons.math3.random.AbstractRandomGenerator

      • jump

        public void jump()
        The jump function for this generator. It is equivalent to 2512 calls to nextLong(); it can be used to generate 2512 non-overlapping subsequences for parallel computations.

      • split

        public XorShift1024StarPhiRandomGenerator split()
        Returns a new instance that shares no mutable state with this instance. The sequence generated by the new instance depends deterministically from the state of this instance, but the probability that the sequence generated by this instance and by the new instance overlap is negligible.
        Returns:
        the new instance.

      • setSeed

        public void setSeed​(long seed)
        Sets the seed of this generator.

        The argument will be used to seed a SplitMix64RandomGenerator, whose output will in turn be used to seed this generator. This approach makes “warmup” unnecessary, and makes the probability of starting from a state with a large fraction of bits set to zero astronomically small.

        Specified by:
        setSeed in interface org.apache.commons.math3.random.RandomGenerator
        Specified by:
        setSeed in class org.apache.commons.math3.random.AbstractRandomGenerator
        Parameters:
        seed - a seed for the generator.

      • setState

        public void setState​(long[] state,
                     int p)
        Sets the state of this generator.

        The internal state of the generator will be reset, and the state array filled with the provided array.

        Parameters:
        state - an array of 16 longs; at least one must be nonzero.
        p - the internal index.