Series of generated values pass the TestU01 BigCrush and PractRand test suites - * that measure independence and uniformity properties of random number generators, - * except that it does not pass the binary rank tests of PractRand, - * which fail due to the lowest bit being an LFSR; all other bits pass all tests. - * For this reason may be best for some purposes to use this generator to generate - * pseudorandom {@code int}, {@code float}, and {@code double} values but not - * {@code long} values. For the same reason, it may be best not to use the - * method {@code nextGaussian} or {@code nextExponential} with this generator. - * - *
The class {@code Xoroshiro128Plus} uses the {@code xoroshiro128} algorithm, - * version 1.0 (parameters 24, 16, 37), with the "+" scrambler - * (the returned value is the sum of the two state variables {@code x0} and {@code x1}). - * Its state consists of two {@code long} fields {@code x0} and {@code x1}, - * which can take on any values provided that they are not both zero. - * The period of this generator is 2128-1. - * - *
The 64-bit values produced by the {@code nextLong()} method are equidistributed. - * To be precise, over the course of the cycle of length 2128-1, - * each nonzero {@code long} value is generated 264 times, - * but the value 0 is generated only 264-1 times. - * The values produced by the {@code nextInt()}, {@code nextFloat()}, and {@code nextDouble()} - * methods are likewise equidistributed. - * - *
Instances {@code Xoroshiro128Plus} are not thread-safe. - * They are designed to be used so that each thread as its own instance. - * The methods {@link #jump} and {@link #leap} and {@link #jumps} and {@link #leaps} - * can be used to construct new instances of {@code Xoroshiro128Plus} that traverse - * other parts of the state cycle. - * - *
Instances of {@code Xoroshiro128Plus} are not cryptographically
- * secure. Consider instead using {@link java.security.SecureRandom}
- * in security-sensitive applications. Additionally,
- * default-constructed instances do not use a cryptographically random
- * seed unless the {@linkplain System#getProperty system property}
- * {@code java.util.secureRandomSeed} is set to {@code true}.
- *
- * @author Guy Steele
- * @author Doug Lea
- * @since 1.8
- */
-public final class Xoroshiro128Plus implements LeapableRng {
-
- /*
- * Implementation Overview.
- *
- * This is an implementation of the xoroshiro128+ algorithm written
- * in 2016 by David Blackman and Sebastiano Vigna (vigna@acm.org),
- * and updated with improved parameters in 2018.
- * See http://xoshiro.di.unimi.it and these two papers:
- *
- * Sebastiano Vigna. 2016. An Experimental Exploration of Marsaglia's
- * xorshift Generators, Scrambled. ACM Transactions on Mathematical
- * Software 42, 4, Article 30 (June 2016), 23 pages.
- * https://doi.org/10.1145/2845077
- *
- * David Blackman and Sebastiano Vigna. 2018. Scrambled Linear
- * Pseudorandom Number Generators. Computing Research Repository (CoRR).
- * http://arxiv.org/abs/1805.01407
- *
- * The jump operation moves the current generator forward by 2*64
- * steps; this has the same effect as calling nextLong() 2**64
- * times, but is much faster. Similarly, the leap operation moves
- * the current generator forward by 2*96 steps; this has the same
- * effect as calling nextLong() 2**96 times, but is much faster.
- * The copy method may be used to make a copy of the current
- * generator. Thus one may repeatedly and cumulatively copy and
- * jump to produce a sequence of generators whose states are well
- * spaced apart along the overall state cycle (indeed, the jumps()
- * and leaps() methods each produce a stream of such generators).
- * The generators can then be parceled out to other threads.
- *
- * File organization: First the non-public methods that constitute the
- * main algorithm, then the public methods. Note that many methods are
- * defined by classes {@code AbstractJumpableRng} and {@code AbstractRng}.
- */
-
- /* ---------------- static fields ---------------- */
-
- /**
- * The seed generator for default constructors.
- */
- private static final AtomicLong defaultGen = new AtomicLong(RngSupport.initialSeed());
-
- /*
- * The period of this generator, which is 2**128 - 1.
- */
- private static final BigInteger thePeriod =
- BigInteger.ONE.shiftLeft(128).subtract(BigInteger.ONE);
-
- /* ---------------- instance fields ---------------- */
-
- /**
- * The per-instance state.
- * At least one of the two fields x0 and x1 must be nonzero.
- */
- private long x0, x1;
-
- /* ---------------- constructors ---------------- */
-
- /**
- * Basic constructor that initializes all fields from parameters.
- * It then adjusts the field values if necessary to ensure that
- * all constraints on the values of fields are met.
- *
- * @param x0 first word of the initial state
- * @param x1 second word of the initial state
- */
- public Xoroshiro128Plus(long x0, long x1) {
- this.x0 = x0;
- this.x1 = x1;
- // If x0 and x1 are both zero, we must choose nonzero values.
- if ((x0 | x1) == 0) {
- // At least one of the two values generated here will be nonzero.
- this.x0 = RngSupport.mixStafford13(x0 += RngSupport.GOLDEN_RATIO_64);
- this.x1 = (x0 += RngSupport.GOLDEN_RATIO_64);
- }
- }
-
- /**
- * Creates a new instance of {@code Xoroshiro128Plus} using the
- * specified {@code long} value as the initial seed. Instances of
- * {@code Xoroshiro128Plus} created with the same seed in the same
- * program generate identical sequences of values.
- *
- * @param seed the initial seed
- */
- public Xoroshiro128Plus(long seed) {
- // Using a value with irregularly spaced 1-bits to xor the seed
- // argument tends to improve "pedestrian" seeds such as 0 or
- // other small integers. We may as well use SILVER_RATIO_64.
- //
- // The x values are then filled in as if by a SplitMix PRNG with
- // GOLDEN_RATIO_64 as the gamma value and Stafford13 as the mixer.
- this(RngSupport.mixStafford13(seed ^= RngSupport.SILVER_RATIO_64),
- RngSupport.mixStafford13(seed + RngSupport.GOLDEN_RATIO_64));
- }
-
- /**
- * Creates a new instance of {@code Xoroshiro128Plus} that is likely to
- * generate sequences of values that are statistically independent
- * of those of any other instances in the current program execution,
- * but may, and typically does, vary across program invocations.
- */
- public Xoroshiro128Plus() {
- // Using GOLDEN_RATIO_64 here gives us a good Weyl sequence of values.
- this(defaultGen.getAndAdd(RngSupport.GOLDEN_RATIO_64));
- }
-
- /**
- * Creates a new instance of {@code Xoroshiro128Plus} using the specified array of
- * initial seed bytes. Instances of {@code Xoroshiro128Plus} created with the same
- * seed array in the same program execution generate identical sequences of values.
- *
- * @param seed the initial seed
- */
- public Xoroshiro128Plus(byte[] seed) {
- // Convert the seed to 2 long values, which are not both zero.
- long[] data = RngSupport.convertSeedBytesToLongs(seed, 2, 2);
- long x0 = data[0], x1 = data[1];
- this.x0 = x0;
- this.x1 = x1;
- }
-
- /* ---------------- public methods ---------------- */
-
- public Xoroshiro128Plus copy() { return new Xoroshiro128Plus(x0, x1); }
-
-/*
-
-To the extent possible under law, the author has dedicated all copyright
-and related and neighboring rights to this software to the public domain
-worldwide. This software is distributed without any warranty.
-
-See