Series of generated values pass the TestU01 BigCrush and PractRand test suites + *
+ * Series of generated values pass the TestU01 BigCrush and PractRand test suites * that measure independence and uniformity properties of random number generators. * (Most recently validated with * version 1.2.3 of TestU01 @@ -47,21 +48,21 @@ * These tests validate only the methods for certain * types and ranges, but similar properties are expected to hold, at * least approximately, for others as well. - * - *
The class {@code Xoshiro256StarStar} uses the {@code xoshiro256} algorithm, + *
+ * The class {@link Xoshiro256StarStar} uses the {@code xoshiro256} algorithm, * version 1.0 (parameters 17, 45), with the "**" scrambler (a mixing function). * Its state consists of four {@code long} fields {@code x0}, {@code x1}, {@code x2}, * and {@code x3}, which can take on any values provided that they are not all zero. * The period of this generator is 2256-1. - * - *
The 64-bit values produced by the {@code nextLong()} method are equidistributed. + *
+ * The 64-bit values produced by the {@code nextLong()} method are equidistributed. * To be precise, over the course of the cycle of length 2256-1, * each nonzero {@code long} value is generated 2192 times, * but the value 0 is generated only 2192-1 times. * The values produced by the {@code nextInt()}, {@code nextFloat()}, and {@code nextDouble()} * methods are likewise equidistributed. - * - *
In fact, the 64-bit values produced by the {@code nextLong()} method are 4-equidistributed. + *
+ * In fact, the 64-bit values produced by the {@code nextLong()} method are 4-equidistributed. * To be precise: consider the (overlapping) length-4 subsequences of the cycle of 64-bit * values produced by {@code nextLong()} (assuming no other methods are called that would * affect the state). There are 2256-1 such subsequences, and each subsequence, @@ -72,24 +73,23 @@ * methods are likewise 4-equidistributed, but note that that the subsequence (0, 0, 0, 0) * can also appear (but occurring somewhat less frequently than all other subsequences), * because the values produced by those methods have fewer than 64 randomly chosen bits. - * - *
Instances {@code Xoshiro256StarStar} are not thread-safe. + *
+ * Instances {@link Xoshiro256StarStar} 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 Xoshiro256StarStar} that traverse + * can be used to construct new instances of {@link Xoshiro256StarStar} that traverse * other parts of the state cycle. - * - *
Instances of {@code Xoshiro256StarStar} are not cryptographically + *
+ * Instances of {@link Xoshiro256StarStar} 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 - * @since 1.9 + * @since 14 */ -public final class Xoshiro256StarStar implements LeapableRng { +public final class Xoshiro256StarStar implements LeapableRNG { /* * Implementation Overview. @@ -128,13 +128,13 @@ /** * The seed generator for default constructors. */ - private static final AtomicLong defaultGen = new AtomicLong(RngSupport.initialSeed()); + private static final AtomicLong DEFAULT_GEN = new AtomicLong(RNGSupport.initialSeed()); /* * The period of this generator, which is 2**256 - 1. */ - private static final BigInteger thePeriod = - BigInteger.ONE.shiftLeft(256).subtract(BigInteger.ONE); + private static final BigInteger PERIOD = + BigInteger.ONE.shiftLeft(256).subtract(BigInteger.ONE); /* ---------------- instance fields ---------------- */ @@ -157,63 +157,63 @@ * @param x3 fourth word of the initial state */ public Xoshiro256StarStar(long x0, long x1, long x2, long x3) { - this.x0 = x0; + this.x0 = x0; this.x1 = x1; this.x2 = x2; this.x3 = x3; - // If x0, x1, x2, and x3 are all zero, we must choose nonzero values. + // If x0, x1, x2, and x3 are all zero, we must choose nonzero values. if ((x0 | x1 | x2 | x3) == 0) { - // At least three of the four values generated here will be nonzero. - this.x0 = RngSupport.mixStafford13(x0 += RngSupport.GOLDEN_RATIO_64); - this.x1 = (x0 += RngSupport.GOLDEN_RATIO_64); - this.x2 = (x0 += RngSupport.GOLDEN_RATIO_64); - this.x3 = (x0 += RngSupport.GOLDEN_RATIO_64); - } + // At least three of the four values generated here will be nonzero. + this.x0 = RNGSupport.mixStafford13(x0 += RNGSupport.GOLDEN_RATIO_64); + this.x1 = (x0 += RNGSupport.GOLDEN_RATIO_64); + this.x2 = (x0 += RNGSupport.GOLDEN_RATIO_64); + this.x3 = (x0 += RNGSupport.GOLDEN_RATIO_64); + } } /** - * Creates a new instance of {@code Xoshiro256StarStar} using the + * Creates a new instance of {@link Xoshiro256StarStar} using the * specified {@code long} value as the initial seed. Instances of - * {@code Xoshiro256StarStar} created with the same seed in the same + * {@link Xoshiro256StarStar} created with the same seed in the same * program generate identical sequences of values. * * @param seed the initial seed */ public Xoshiro256StarStar(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), - RngSupport.mixStafford13(seed += RngSupport.GOLDEN_RATIO_64), - RngSupport.mixStafford13(seed + RngSupport.GOLDEN_RATIO_64)); + // 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), + RNGSupport.mixStafford13(seed += RNGSupport.GOLDEN_RATIO_64), + RNGSupport.mixStafford13(seed + RNGSupport.GOLDEN_RATIO_64)); } /** - * Creates a new instance of {@code Xoshiro256StarStar} that is likely to + * Creates a new instance of {@link Xoshiro256StarStar} 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 Xoshiro256StarStar() { - // Using GOLDEN_RATIO_64 here gives us a good Weyl sequence of values. - this(defaultGen.getAndAdd(RngSupport.GOLDEN_RATIO_64)); + // Using GOLDEN_RATIO_64 here gives us a good Weyl sequence of values. + this(DEFAULT_GEN.getAndAdd(RNGSupport.GOLDEN_RATIO_64)); } /** - * Creates a new instance of {@code Xoshiro256StarStar} using the specified array of - * initial seed bytes. Instances of {@code Xoshiro256StarStar} created with the same + * Creates a new instance of {@link Xoshiro256StarStar} using the specified array of + * initial seed bytes. Instances of {@link Xoshiro256StarStar} created with the same * seed array in the same program execution generate identical sequences of values. * * @param seed the initial seed */ public Xoshiro256StarStar(byte[] seed) { - // Convert the seed to 4 long values, which are not all zero. - long[] data = RngSupport.convertSeedBytesToLongs(seed, 4, 4); - long x0 = data[0], x1 = data[1], x2 = data[2], x3 = data[3]; + // Convert the seed to 4 long values, which are not all zero. + long[] data = RNGSupport.convertSeedBytesToLongs(seed, 4, 4); + long x0 = data[0], x1 = data[1], x2 = data[2], x3 = data[3]; this.x0 = x0; this.x1 = x1; this.x2 = x2; @@ -222,64 +222,75 @@ /* ---------------- public methods ---------------- */ - public Xoshiro256StarStar copy() { return new Xoshiro256StarStar(x0, x1, x2, x3); } + public Xoshiro256StarStar copy() { + return new Xoshiro256StarStar(x0, x1, x2, x3); + } /** * Returns a pseudorandom {@code long} value. * * @return a pseudorandom {@code long} value */ - - public long nextLong() { - final long z = x0; - long q0 = x0, q1 = x1, q2 = x2, q3 = x3; - { long t = q1 << 17; q2 ^= q0; q3 ^= q1; q1 ^= q2; q0 ^= q3; q2 ^= t; q3 = Long.rotateLeft(q3, 45); } // xoshiro256 1.0 - x0 = q0; x1 = q1; x2 = q2; x3 = q3; - return Long.rotateLeft(z * 5, 7) * 9; // "starstar" mixing function + public long nextLong() { + final long z = x0; + long q0 = x0, q1 = x1, q2 = x2, q3 = x3; + { long t = q1 << 17; q2 ^= q0; q3 ^= q1; q1 ^= q2; q0 ^= q3; q2 ^= t; q3 = Long.rotateLeft(q3, 45); } // xoshiro256 1.0 + x0 = q0; x1 = q1; x2 = q2; x3 = q3; + return Long.rotateLeft(z * 5, 7) * 9; // "starstar" mixing function } - public BigInteger period() { return thePeriod; } + public BigInteger period() { + return PERIOD; + } - - public double defaultJumpDistance() { return 0x1.0p64; } - public double defaultLeapDistance() { return 0x1.0p96; } + public double defaultJumpDistance() { + return 0x1.0p64; + } + + public double defaultLeapDistance() { + return 0x1.0p96; + } private static final long[] JUMP_TABLE = { - 0x180ec6d33cfd0abaL, 0xd5a61266f0c9392cL, 0xa9582618e03fc9aaL, 0x39abdc4529b1661cL }; - + 0x180ec6d33cfd0abaL, 0xd5a61266f0c9392cL, 0xa9582618e03fc9aaL, 0x39abdc4529b1661cL }; + private static final long[] LEAP_TABLE = { - 0x76e15d3efefdcbbfL, 0xc5004e441c522fb3L, 0x77710069854ee241L, 0x39109bb02acbe635L }; - -/* This is the jump function for the generator. It is equivalent - to 2**128 calls to next(); it can be used to generate 2**128 - non-overlapping subsequences for parallel computations. */ + 0x76e15d3efefdcbbfL, 0xc5004e441c522fb3L, 0x77710069854ee241L, 0x39109bb02acbe635L }; - public void jump() { jumpAlgorithm(JUMP_TABLE); } - -/* This is the long-jump function for the generator. It is equivalent to - 2**192 calls to next(); it can be used to generate 2**64 starting points, - from each of which jump() will generate 2**64 non-overlapping - subsequences for parallel distributed computations. */ + /** + * This is the jump function for the generator. It is equivalent to 2**128 calls to next(); it + * can be used to generate 2**128 non-overlapping subsequences for parallel computations. + */ + public void jump() { + jumpAlgorithm(JUMP_TABLE); + } - public void leap() { jumpAlgorithm(LEAP_TABLE); } + /** + * This is the long-jump function for the generator. It is equivalent to 2**192 calls to next(); + * it can be used to generate 2**64 starting points, from each of which jump() will generate + * 2**64 non-overlapping subsequences for parallel distributed computations. + */ + public void leap() { + jumpAlgorithm(LEAP_TABLE); + } private void jumpAlgorithm(long[] table) { - long s0 = 0, s1 = 0, s2 = 0, s3 = 0; - for (int i = 0; i < table.length; i++) { - for (int b = 0; b < 64; b++) { - if ((table[i] & (1L << b)) != 0) { - s0 ^= x0; - s1 ^= x1; - s2 ^= x2; - s3 ^= x3; - } - nextLong(); - } - x0 = s0; - x1 = s1; - x2 = s2; - x3 = s3; - } + long s0 = 0, s1 = 0, s2 = 0, s3 = 0; + for (int i = 0; i < table.length; i++) { + for (int b = 0; b < 64; b++) { + if ((table[i] & (1L << b)) != 0) { + s0 ^= x0; + s1 ^= x1; + s2 ^= x2; + s3 ^= x3; + } + nextLong(); + } + x0 = s0; + x1 = s1; + x2 = s2; + x3 = s3; + } } }