| /* |
| * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| package jdk.random; |
| |
| import java.util.concurrent.atomic.AtomicLong; |
| import java.util.random.RandomGenerator; |
| import java.util.random.RandomGenerator.LeapableGenerator; |
| import jdk.internal.util.random.RandomSupport; |
| import jdk.internal.util.random.RandomSupport.RandomGeneratorProperties; |
| |
| /** |
| * A "jumpable and leapable" pseudorandom number generator (PRNG) whose period |
| * is roughly 2<sup>256</sup>. Class {@link Xoshiro256PlusPlus} implements |
| * interfaces {@link RandomGenerator} and {@link LeapableGenerator}, |
| * and therefore supports methods for producing pseudorandomly chosen |
| * values of type {@code int}, {@code long}, {@code float}, {@code double}, |
| * and {@code boolean} (and for producing streams of pseudorandomly chosen |
| * numbers of type {@code int}, {@code long}, and {@code double}), |
| * as well as methods for creating new {@link Xoshiro256PlusPlus} objects |
| * by moving forward either a large distance (2<sup>128</sup>) or a very large |
| * distance (2<sup>192</sup>) around the state cycle. |
| * <p> |
| * 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 |
| * <a href="http://simul.iro.umontreal.ca/testu01/tu01.html">version 1.2.3 of TestU01</a> |
| * and <a href="http://pracrand.sourceforge.net">version 0.90 of PractRand</a>. |
| * Note that TestU01 BigCrush was used to test not only values produced by the {@code nextLong()} |
| * method but also the result of bit-reversing each value produced by {@code nextLong()}.) |
| * 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. |
| * <p> |
| * The class {@link Xoshiro256PlusPlus} uses the {@code xoshiro256} algorithm, |
| * version 1.0 (parameters 17, 45), with the "++" scrambler that computes |
| * {@code Long.rotateLeft(s0 + s3, 23) + s0}. |
| * (See David Blackman and Sebastiano Vigna, "Scrambled Linear Pseudorandom |
| * Number Generators," ACM Transactions on Mathematical Software, 2021.) |
| * 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 2<sup>256</sup>-1. |
| * <p> |
| * The 64-bit values produced by the {@code nextLong()} method are equidistributed. |
| * To be precise, over the course of the cycle of length 2<sup>256</sup>-1, |
| * each nonzero {@code long} value is generated 2<sup>192</sup> times, |
| * but the value 0 is generated only 2<sup>192</sup>-1 times. |
| * The values produced by the {@code nextInt()}, {@code nextFloat()}, and {@code nextDouble()} |
| * methods are likewise equidistributed. |
| * Moreover, the 64-bit values produced by the {@code nextLong()} method are 3-equidistributed. |
| * <p> |
| * Instances {@link Xoshiro256PlusPlus} are <em>not</em> 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 {@link Xoshiro256PlusPlus} that traverse |
| * other parts of the state cycle. |
| * <p> |
| * Instances of {@link Xoshiro256PlusPlus} 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}. |
| * |
| * @since 17 |
| * |
| */ |
| @RandomGeneratorProperties( |
| name = "Xoshiro256PlusPlus", |
| group = "Xoshiro", |
| i = 256, j = 1, k = 0, |
| equidistribution = 3 |
| ) |
| public final class Xoshiro256PlusPlus implements LeapableGenerator { |
| |
| /* |
| * Implementation Overview. |
| * |
| * This is an implementation of the xoshiro256++ algorithm version 1.0, |
| * written in 2019 by David Blackman and Sebastiano Vigna ([email protected]). |
| * |
| * The jump operation moves the current generator forward by 2*128 |
| * steps; this has the same effect as calling nextLong() 2**128 |
| * times, but is much faster. Similarly, the leap operation moves |
| * the current generator forward by 2*192 steps; this has the same |
| * effect as calling nextLong() 2**192 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 static fields, then instance |
| * fields, then constructors, then instance methods. |
| */ |
| |
| /* ---------------- static fields ---------------- */ |
| |
| /** |
| * The seed generator for default constructors. |
| */ |
| private static final AtomicLong DEFAULT_GEN = new AtomicLong(RandomSupport.initialSeed()); |
| |
| /* ---------------- instance fields ---------------- */ |
| |
| /** |
| * The per-instance state. |
| * At least one of the four fields x0, x1, x2, and x3 must be nonzero. |
| */ |
| private long x0, x1, x2, x3; |
| |
| /* ---------------- 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 |
| * @param x2 third word of the initial state |
| * @param x3 fourth word of the initial state |
| */ |
| public Xoshiro256PlusPlus(long x0, long x1, long x2, long x3) { |
| 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 | x3) == 0) { |
| // At least three of the four values generated here will be nonzero. |
| this.x0 = RandomSupport.mixStafford13(x0 += RandomSupport.GOLDEN_RATIO_64); |
| this.x1 = (x0 += RandomSupport.GOLDEN_RATIO_64); |
| this.x2 = (x0 += RandomSupport.GOLDEN_RATIO_64); |
| this.x3 = (x0 += RandomSupport.GOLDEN_RATIO_64); |
| } |
| } |
| |
| /** |
| * Creates a new instance of {@link Xoshiro256PlusPlus} using the |
| * specified {@code long} value as the initial seed. Instances of |
| * {@link Xoshiro256PlusPlus} created with the same seed in the same |
| * program generate identical sequences of values. |
| * |
| * @param seed the initial seed |
| */ |
| public Xoshiro256PlusPlus(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(RandomSupport.mixStafford13(seed ^= RandomSupport.SILVER_RATIO_64), |
| RandomSupport.mixStafford13(seed += RandomSupport.GOLDEN_RATIO_64), |
| RandomSupport.mixStafford13(seed += RandomSupport.GOLDEN_RATIO_64), |
| RandomSupport.mixStafford13(seed + RandomSupport.GOLDEN_RATIO_64)); |
| } |
| |
| /** |
| * Creates a new instance of {@link Xoshiro256PlusPlus} 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 Xoshiro256PlusPlus() { |
| // Using GOLDEN_RATIO_64 here gives us a good Weyl sequence of values. |
| this(DEFAULT_GEN.getAndAdd(RandomSupport.GOLDEN_RATIO_64)); |
| } |
| |
| /** |
| * Creates a new instance of {@link Xoshiro256PlusPlus} using the specified array of |
| * initial seed bytes. Instances of {@link Xoshiro256PlusPlus} created with the same |
| * seed array in the same program execution generate identical sequences of values. |
| * |
| * @param seed the initial seed |
| */ |
| public Xoshiro256PlusPlus(byte[] seed) { |
| // Convert the seed to 4 long values, which are not all zero. |
| long[] data = RandomSupport.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; |
| this.x3 = x3; |
| } |
| |
| /* ---------------- public methods ---------------- */ |
| |
| public Xoshiro256PlusPlus copy() { |
| return new Xoshiro256PlusPlus(x0, x1, x2, x3); |
| } |
| |
| /* |
| * The following two comments are quoted from http://prng.di.unimi.it/xoshiro256plusplus.c |
| */ |
| |
| /* |
| * 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. |
| * <p> |
| * See http://creativecommons.org/publicdomain/zero/1.0/. |
| */ |
| |
| /* |
| * This is xoshiro256++ 1.0, one of our all-purpose, rock-solid generators. |
| * It has excellent (sub-ns) speed, a state (256 bits) that is large |
| * enough for any parallel application, and it passes all tests we are |
| * aware of. |
| * |
| * For generating just floating-point numbers, xoshiro256+ is even faster. |
| * |
| * The state must be seeded so that it is not everywhere zero. If you have |
| * a 64-bit seed, we suggest to seed a splitmix64 generator and use its |
| * output to fill s. |
| */ |
| |
| @Override |
| public long nextLong() { |
| // Compute the result based on current state information |
| // (this allows the computation to be overlapped with state update). |
| final long result = Long.rotateLeft(x0 + x3, 23) + x0; // "plusplus" scrambler |
| |
| long q0 = x0, q1 = x1, q2 = x2, q3 = x3; |
| { // xoshiro256 1.0 |
| long t = q1 << 17; |
| q2 ^= q0; |
| q3 ^= q1; |
| q1 ^= q2; |
| q0 ^= q3; |
| q2 ^= t; |
| q3 = Long.rotateLeft(q3, 45); |
| } |
| x0 = q0; x1 = q1; x2 = q2; x3 = q3; |
| return result; |
| } |
| |
| @Override |
| public double jumpDistance() { |
| return 0x1.0p128; |
| } |
| |
| @Override |
| public double leapDistance() { |
| return 0x1.0p192; |
| } |
| |
| private static final long[] JUMP_TABLE = { |
| 0x180ec6d33cfd0abaL, 0xd5a61266f0c9392cL, 0xa9582618e03fc9aaL, 0x39abdc4529b1661cL }; |
| |
| private static final long[] LEAP_TABLE = { |
| 0x76e15d3efefdcbbfL, 0xc5004e441c522fb3L, 0x77710069854ee241L, 0x39109bb02acbe635L }; |
| |
| @Override |
| public void jump() { |
| jumpAlgorithm(JUMP_TABLE); |
| } |
| |
| @Override |
| 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; |
| } |
| |
| } |
