--- a/src/java.base/share/classes/java/util/random/L32X64MixRandom.java Thu Aug 29 11:33:26 2019 -0300
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,335 +0,0 @@
-/*
- * Copyright (c) 2013, 2019, 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 java.util.random;
-
-import java.math.BigInteger;
-import java.util.concurrent.atomic.AtomicLong;
-import java.util.random.RandomGenerator.SplittableGenerator;
-import java.util.random.RandomSupport.AbstractSplittableGenerator;
-
-/**
- * A generator of uniform pseudorandom values applicable for use in
- * (among other contexts) isolated parallel computations that may
- * generate subtasks. Class {@link L32X64MixRandom} implements
- * interfaces {@link RandomGenerator} and {@link SplittableGenerator},
- * and therefore supports methods for producing pseudorandomly chosen
- * numbers of type {@code int}, {@code long}, {@code float}, and {@code double}
- * as well as creating new split-off {@link L32X64MixRandom} objects,
- * with similar usages as for class {@link java.util.SplittableRandom}.
- * <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>
- * {@link L32X64MixRandom} is a specific member of the LXM family of algorithms
- * for pseudorandom number generators. Every LXM generator consists of two
- * subgenerators; one is an LCG (Linear Congruential Generator) and the other is
- * an Xorshift generator. Each output of an LXM generator is the sum of one
- * output from each subgenerator, possibly processed by a final mixing function
- * (and {@link L32X64MixRandom} does use a mixing function).
- * <p>
- * The LCG subgenerator for {@link L32X64MixRandom} has an update step of the
- * form {@code s = m * s + a}, where {@code s}, {@code m}, and {@code a} are all
- * of type {@code int}; {@code s} is the mutable state, the multiplier {@code m}
- * is fixed (the same for all instances of {@link L32X64MixRandom}) and the addend
- * {@code a} is a parameter (a final field of the instance). The parameter
- * {@code a} is required to be odd (this allows the LCG to have the maximal
- * period, namely 2<sup>32</sup>); therefore there are 2<sup>31</sup> distinct choices
- * of parameter.
- * <p>
- * The Xorshift subgenerator for {@link L32X64MixRandom} is the {@code xoroshiro64} algorithm,
- * version 1.0 (parameters 26, 9, 13), without any final scrambler such as "+" or "**".
- * Its state consists of two {@code int} fields {@code x0} and {@code x1},
- * which can take on any values provided that they are not both zero.
- * The period of this subgenerator is 2<sup>64</sup>-1.
- * <p>
- * The mixing function for {@link L32X64MixRandom} is the "starstar" mixing function.
- * <p>
- * Because the periods 2<sup>32</sup> and 2<sup>64</sup>-1 of the two subgenerators
- * are relatively prime, the <em>period</em> of any single {@link L32X64MixRandom} object
- * (the length of the series of generated 32-bit values before it repeats) is the product
- * of the periods of the subgenerators, that is, 2<sup>32</sup>(2<sup>64</sup>-1),
- * which is just slightly smaller than 2<sup>96</sup>. Moreover, if two distinct
- * {@link L32X64MixRandom} objects have different {@code a} parameters, then their
- * cycles of produced values will be different.
- * <p>
- * The 32-bit values produced by the {@code nextInt()} method are exactly equidistributed.
- * For any specific instance of {@link L32X64MixRandom}, over the course of its cycle each
- * of the 2<sup>32</sup> possible {@code int} values will be produced 2<sup>64</sup>-1 times.
- * The values produced by the {@code nextFloat()} method are likewise exactly equidistributed.
- * <p>
- * In fact, the 32-bit values produced by the {@code nextInt()} method are 2-equidistributed.
- * To be precise: for any specific instance of {@link L32X64MixRandom}, consider
- * the (overlapping) length-2 subsequences of the cycle of 64-bit values produced by
- * {@code nextInt()} (assuming no other methods are called that would affect the state).
- * There are 2<sup>32</sup>(2<sup>64</sup>-1) such subsequences, and each subsequence,
- * which consists of 2 32-bit values, can have one of 2<sup>64</sup> values. Of those
- * 2<sup>64</sup> subsequence values, nearly all of them (2<sup>64</sup>-2<sup>32</sup>)
- * occur 2<sup>32</sup> times over the course of the entire cycle, and the other
- * 2<sup>32</sup> subsequence values occur only 2<sup>32</sup>-1 times. So the ratio
- * of the probability of getting one of the less common subsequence values and the
- * probability of getting one of the more common subsequence values is 1-2<sup>-32</sup>.
- * (Note that the set of 2<sup>32</sup> less-common subsequence values will differ from
- * one instance of {@link L32X64MixRandom} to another, as a function of the additive
- * parameter of the LCG.) As a consequence, the values produced by the {@code nextFloat()}
- * method are likewise 2-equidistributed, and the values produced by the {@code nextLong()}
- * and {@code nextDouble()} methods are equidistributed (but not 2-equidistributed).
- * <p>
- * Method {@link #split} constructs and returns a new {@link L32X64MixRandom}
- * instance that shares no mutable state with the current instance. However, with
- * very high probability, the values collectively generated by the two objects
- * have the same statistical properties as if the same quantity of values were
- * generated by a single thread using a single {@link L32X64MixRandom} object.
- * This is because, with high probability, distinct {@link L32X64MixRandom} objects
- * have distinct {@code a} parameters and therefore use distinct members of the
- * algorithmic family; and even if their {@code a} parameters are the same, with
- * very high probability they will traverse different parts of their common state
- * cycle.
- * <p>
- * As with {@link java.util.SplittableRandom}, instances of
- * {@link L32X64MixRandom} are <em>not</em> thread-safe.
- * They are designed to be split, not shared, across threads. For
- * example, a {@link java.util.concurrent.ForkJoinTask} fork/join-style
- * computation using random numbers might include a construction
- * of the form {@code new Subtask(someL32X64MixRandom.split()).fork()}.
- * <p>
- * This class provides additional methods for generating random
- * streams, that employ the above techniques when used in
- * {@code stream.parallel()} mode.
- * <p>
- * Instances of {@link L32X64MixRandom} 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 14
- */
-public final class L32X64MixRandom extends AbstractSplittableGenerator {
-
- /*
- * Implementation Overview.
- *
- * The split operation uses the current generator to choose four new 64-bit
- * int values that are then used to initialize the parameter `a` and the
- * state variables `s`, `x0`, and `x1` for a newly constructed generator.
- *
- * With high probability, no two generators so chosen
- * will have the same `a` parameter, and testing has indicated
- * that the values generated by two instances of {@link L32X64MixRandom}
- * will be (approximately) independent if have different values for `a`.
- *
- * The default (no-argument) constructor, in essence, uses
- * "defaultGen" to generate four new 32-bit values for the same
- * purpose. Multiple generators created in this way will certainly
- * differ in their `a` parameters. The defaultGen state must be accessed
- * in a thread-safe manner, so we use an AtomicLong to represent
- * this state. To bootstrap the defaultGen, we start off using a
- * seed based on current time unless the
- * java.util.secureRandomSeed property is set. This serves as a
- * slimmed-down (and insecure) variant of SecureRandom that also
- * avoids stalls that may occur when using /dev/random.
- *
- * 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 defaultGen = new AtomicLong(RandomSupport.initialSeed());
-
- /*
- * The period of this generator, which is (2**64 - 1) * 2**32.
- */
- private static final BigInteger PERIOD =
- BigInteger.ONE.shiftLeft(64).subtract(BigInteger.ONE).shiftLeft(32);
-
- /*
- * Multiplier used in the LCG portion of the algorithm, taken from
- * Pierre L'Ecuyer, Tables of linear congruential generators of
- * different sizes and good lattice structure, <em>Mathematics of
- * Computation</em> 68, 225 (January 1999), pages 249-260,
- * Table 4 (third multiplier for size 2<sup>32</sup>).
- */
-
- private static final int M = 32310901;
-
- /* ---------------- instance fields ---------------- */
-
- /**
- * The parameter that is used as an additive constant for the LCG.
- * Must be odd.
- */
- private final int a;
-
- /**
- * The per-instance state: s for the LCG; x0 and x1 for the xorshift.
- * At least one of x0 and x1 must be nonzero.
- */
- private int s, 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 a additive parameter for the LCG
- * @param s initial state for the LCG
- * @param x0 first word of the initial state for the xorshift generator
- * @param x1 second word of the initial state for the xorshift generator
- */
- public L32X64MixRandom(int a, int s, int x0, int x1) {
- // Force a to be odd.
- this.a = a | 1;
- this.s = s;
- // 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 = RandomSupport.mixMurmur32(s += RandomSupport.GOLDEN_RATIO_32);
- this.x1 = RandomSupport.mixMurmur32(s + RandomSupport.GOLDEN_RATIO_32);
- }
- }
-
- /**
- * Creates a new instance of {@link L32X64MixRandom} using the
- * specified {@code long} value as the initial seed. Instances of
- * {@link L32X64MixRandom} created with the same seed in the same
- * program generate identical sequences of values.
- *
- * @param seed the initial seed
- */
- public L32X64MixRandom(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 high half of the seed is hashed by mixMurmur32 to produce the `a` parameter.
- // The low half of the seed is hashed by mixMurmur32 to produce the initial `x0`,
- // which will then be used to produce the first generated value.
- // Then x1 is filled in as if by a SplitMix PRNG with
- // GOLDEN_RATIO_32 as the gamma value and Murmur32 as the mixer.
- this(RandomSupport.mixMurmur32((int)((seed ^= RandomSupport.SILVER_RATIO_64) >>> 32)),
- 1,
- RandomSupport.mixLea32((int)(seed)),
- RandomSupport.mixLea32((int)(seed) + RandomSupport.GOLDEN_RATIO_32));
- }
-
- /**
- * Creates a new instance of {@link L32X64MixRandom} 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 L32X64MixRandom() {
- // Using GOLDEN_RATIO_64 here gives us a good Weyl sequence of values.
- this(defaultGen.getAndAdd(RandomSupport.GOLDEN_RATIO_64));
- }
-
- /**
- * Creates a new instance of {@link L32X64MixRandom} using the specified array of
- * initial seed bytes. Instances of {@link L32X64MixRandom} created with the same
- * seed array in the same program execution generate identical sequences of values.
- *
- * @param seed the initial seed
- */
- public L32X64MixRandom(byte[] seed) {
- // Convert the seed to 4 int values, of which the last 2 are not all zero.
- int[] data = RandomSupport.convertSeedBytesToInts(seed, 4, 2);
- int a = data[0], s = data[1], x0 = data[2], x1 = data[3];
- // Force a to be odd.
- this.a = a | 1;
- this.s = s;
- this.x0 = x0;
- this.x1 = x1;
- }
-
- /* ---------------- public methods ---------------- */
-
- /**
- * Constructs and returns a new instance of {@link L32X64MixRandom} that shares no mutable state
- * with this instance. However, with very high probability, the set of values collectively
- * generated by the two objects has the same statistical properties as if same the quantity of
- * values were generated by a single thread using a single {@link L32X64MixRandom} object.
- * Either or both of the two objects may be further split using the {@code split} method, and
- * the same expected statistical properties apply to the entire set of generators constructed by
- * such recursive splitting.
- *
- * @param source a {@link SplittableGenerator} instance to be used instead of this one as
- * a source of pseudorandom bits used to initialize the state of the new ones.
- *
- * @return a new instance of {@link L32X64MixRandom}
- */
- public L32X64MixRandom split(SplittableGenerator source) {
- // Literally pick a new instance "at random".
- return new L32X64MixRandom(source.nextInt(), source.nextInt(),
- source.nextInt(), source.nextInt());
- }
-
- /**
- * Returns a pseudorandom {@code int} value.
- *
- * @return a pseudorandom {@code int} value
- */
- public int nextInt() {
- final int z = s + x0;
- s = M * s + a; // LCG
- int q0 = x0, q1 = x1;
- { // xoroshiro64
- q1 ^= q0;
- q0 = Integer.rotateLeft(q0, 26);
- q0 = q0 ^ q1 ^ (q1 << 9);
- q1 = Integer.rotateLeft(q1, 13);
- }
- x0 = q0; x1 = q1;
- return Integer.rotateLeft(z * 5, 7) * 9; // "starstar" mixing function
- }
-
- /**
- * Returns a pseudorandom {@code long} value.
- *
- * @return a pseudorandom {@code long} value
- */
- public long nextLong() {
- return ((long)(nextInt()) << 32) | nextInt();
- }
-
- public BigInteger period() {
- return PERIOD;
- }
-}