Package it.unimi.dsi.util

Class XoRoShiRo128PlusRandomGenerator

  • All Implemented Interfaces:
    Serializable, org.apache.commons.math3.random.RandomGenerator
    public class XoRoShiRo128PlusRandomGenerator
extends org.apache.commons.math3.random.AbstractRandomGenerator
implements Serializable
    A fast, high-quality pseudorandom number generator for floating-point generation. It has excellent speed, but its state space (128 bits) is large enough for mild parallelism only. It passes all tests we are aware of except for the four lower bits, which might fail linearity tests (and just those), so if low linear complexity is not considered an issue (as it is usually the case) it can be used to generate integer outputs, too; moreover, this generator has a very mild Hamming-weight dependency making our test fail after 8 TB of output; we believe this slight bias cannot affect any application. If you are concerned, use XoRoShiRo128StarStarRandomGenerator or XoShiRo256PlusRandomGenerator. More information can be found at our PRNG page.

    Warning: the constants used in this generator differ from the ones used in the 2016 version.

    If you need a general PRNG, use XoRoShiRo128StarStarRandomGenerator. If you can use more space, you might try XoShiRo256PlusRandomGenerator.

    By using the supplied jump() method it is possible to generate non-overlapping long sequences for parallel computations; longJump() makes it possible to create several starting points, each providing several non-overlapping sequences, for distributed 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.

    Version:
    1.0
    See Also:
    it.unimi.dsi.util, Random, XoRoShiRo128PlusRandom, Serialized Form

    • Constructor Detail

      • XoRoShiRo128PlusRandomGenerator

        protected XoRoShiRo128PlusRandomGenerator​(long s0,
                                          long s1)

      • XoRoShiRo128PlusRandomGenerator

        public XoRoShiRo128PlusRandomGenerator()
        Creates a new generator seeded using Util.randomSeed().

      • XoRoShiRo128PlusRandomGenerator

        public XoRoShiRo128PlusRandomGenerator​(long seed)
        Creates a new generator using a given seed.
        Parameters:
        seed - a seed for the generator.

    • Method Detail

      • copy

        public XoRoShiRo128PlusRandomGenerator copy()
        Returns a copy of this generator. The sequences produced by this generator and by the returned generator will be identical.

        This method is particularly useful in conjunction with the jump() method: by calling repeatedly jump().copy() over a generator it is possible to create several generators producing non-overlapping sequences.

        Returns:
        a copy of this generator.

      • 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. Before version 2.4.1, this was actually the standard implementation of nextDouble(), so you can use this method if you need to reproduce exactly results obtained using previous versions.

        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.
        Since:
        2.4.1

      • 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 XoRoShiRo128PlusRandomGenerator jump()
        The jump function for this generator. It is equivalent to 264 calls to nextLong(); it can be used to generate 264 non-overlapping subsequences for parallel computations.
        Returns:
        this generator.
        See Also:
        copy()

      • longJump

        public XoRoShiRo128PlusRandomGenerator longJump()
        The long-jump function for this generator. It is equivalent to 296 calls to nextLong(); it can be used to generate 232 starting points, from each of which jump() will generate 232 non-overlapping subsequences for parallel distributed computations.
        Returns:
        this generator.
        See Also:
        copy()

      • split

        public XoRoShiRo128PlusRandomGenerator 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 this generator.

      • setState

        public void setState​(long[] state)
        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 2 longs; at least one must be nonzero.

      • main

        public static void main​(String[] arg)