--- a/src/java.base/share/classes/java/util/L128X256MixRandom.java Thu Jun 27 16:46:44 2019 -0300
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,367 +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;
-
-import java.math.BigInteger;
-import java.util.concurrent.atomic.AtomicLong;
-
-/**
- * A generator of uniform pseudorandom values applicable for use in
- * (among other contexts) isolated parallel computations that may
- * generate subtasks. Class {@code L128X256MixRandom} implements
- * interfaces {@link java.util.Rng} and {@link java.util.SplittableRng},
- * 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 {@code L128X256MixRandom} 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>{@code L128X256MixRandom} 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 {@code L128X256MixRandom} does use a mixing function).
- *
- * <p>The LCG subgenerator for {@code L128X256MixRandom} has an update step of the
- * form {@code s = m * s + a}, where {@code s}, {@code m}, and {@code a} are all
- * 128-bit integers; {@code s} is the mutable state, the multiplier {@code m}
- * is fixed (the same for all instances of {@code L128X256MixRandom}}) 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>128</sup>); therefore there are 2<sup>127</sup> distinct choices
- * of parameter.
- *
- * <p>The Xorshift subgenerator for {@code L128X256MixRandom} is the {@code xoshiro256} algorithm,
- * version 1.0 (parameters 17, 45), without any final scrambler such as "+" or "**".
- * 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 subgenerator is 2<sup>256</sup>-1.
- *
- * <p> The mixing function for {@code L128X256MixRandom} is the 64-bit MurmurHash3 finalizer.
- *
- * <p> Because the periods 2<sup>128</sup> and 2<sup>256</sup>-1 of the two subgenerators
- * are relatively prime, the <em>period</em> of any single {@code L128X256MixRandom} object
- * (the length of the series of generated 64-bit values before it repeats) is the product
- * of the periods of the subgenerators, that is, 2<sup>128</sup>(2<sup>256</sup>-1),
- * which is just slightly smaller than 2<sup>384</sup>. Moreover, if two distinct
- * {@code L128X256MixRandom} objects have different {@code a} parameters, then their
- * cycles of produced values will be different.
- *
- * <p>The 64-bit values produced by the {@code nextLong()} method are exactly equidistributed.
- * For any specific instance of {@code L128X256MixRandom}, over the course of its cycle each
- * of the 2<sup>64</sup> possible {@code long} values will be produced 2<sup>256</sup>-1 times.
- * The values produced by the {@code nextInt()}, {@code nextFloat()}, and {@code nextDouble()}
- * methods are likewise exactly equidistributed.
- *
- * <p>In fact, the 64-bit values produced by the {@code nextLong()} method are exactly
- * 2-equidistributed. For any specific instance of {@code L128X256MixRandom}, consider
- * the (overlapping) length-2 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 2<sup>128</sup>(2<sup>256</sup>-1) such subsequences, and each subsequence,
- * which consists of 2 64-bit values, can have one of 2<sup>128</sup> values, and each
- * such value occurs 2<sup>256</sup>-1 times. The values produced by the {@code nextInt()},
- * {@code nextFloat()}, and {@code nextDouble()} methods are likewise exactly 2-equidistributed.
- *
- * <p>Moreover, the 64-bit values produced by the {@code nextLong()} method are 4-equidistributed.
- * To be precise: for any specific instance of {@code L128X256MixRandom}, 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 <sup>128</sup>(2<sup>256</sup>-1) such subsequences, and each subsequence,
- * which consists of 4 64-bit values, can have one of 2<sup>256</sup> values. Of those
- * 2<sup>256</sup> subsequence values, nearly all of them (2<sup>256</sup>-2<sup>128</sup>)
- * occur 2<sup>128</sup> times over the course of the entire cycle, and the other
- * 2<sup>128</sup> subsequence values occur only 2<sup>128</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>-128</sup>.
- * (Note that the set of 2<sup>128</sup> less-common subsequence values will differ from
- * one instance of {@code L128X256MixRandom} to another, as a function of the additive
- * parameter of the LCG.) The values produced by the {@code nextInt()}, {@code nextFloat()},
- * and {@code nextDouble()} methods are likewise 4-equidistributed.
- *
- * <p>Method {@link #split} constructs and returns a new {@code L128X256MixRandom}
- * 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 {@code L128X256MixRandom} object.
- * This is because, with high probability, distinct {@code L128X256MixRandom} 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
- * {@code L128X256MixRandom} 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(someL128X256MixRandom.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 {@code L128X256MixRandom} 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
- */
-public final class L128X256MixRandom extends AbstractSplittableRng {
-
- /*
- * Implementation Overview.
- *
- * The 128-bit parameter `a` is represented as two long fields `ah` and `al`.
- * The 128-bit state variable `s` is represented as two long fields `sh` and `sl`.
- *
- * The split operation uses the current generator to choose eight
- * new 64-bit long values that are then used to initialize the
- * parameters `ah` and `al` and the state variables `sh`, `sl`,
- * `x0`, `x1`, `x2`, and `x3` for a newly constructed generator.
- *
- * With extremely 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 {@code L128X256MixRandom}
- * will be (approximately) independent if have different values for `a`.
- *
- * The default (no-argument) constructor, in essence, uses
- * "defaultGen" to generate eight new 64-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(RngSupport.initialSeed());
-
- /*
- * The period of this generator, which is (2**256 - 1) * 2**128.
- */
- private static final BigInteger thePeriod =
- BigInteger.ONE.shiftLeft(256).subtract(BigInteger.ONE).shiftLeft(128);
-
- /*
- * The multiplier used in the LCG portion of the algorithm is 2**64 + m;
- * where m is 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 (first multiplier for size 2<sup>64</sup>).
- *
- * This is almost certainly not the best possible 128-bit multiplier
- * for an LCG, but it is sufficient for our purposes here; because
- * is is larger than 2**64, the 64-bit values produced by nextLong()
- * are exactly 2-equidistributed, and the fact that it is of the
- * form (2**64 + m) simplifies the code, given that we have only
- * 64-bit arithmetic to work with.
- */
-
- private static final long m = 2862933555777941757L;
-
- /* ---------------- instance fields ---------------- */
-
- /**
- * The parameter that is used as an additive constant for the LCG.
- * Must be odd.
- */
- private final long ah, al;
-
- /**
- * The per-instance state: sh and sl for the LCG; x0, x1, x2, and x3 for the xorshift.
- * At least one of the four fields x0, x1, x2, and x3 must be nonzero.
- */
- private long sh, sl, 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 ah high half of the additive parameter for the LCG
- * @param al low half of the additive parameter for the LCG
- * @param sh high half of the initial state for the LCG
- * @param sl low half of the 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
- * @param x2 third word of the initial state for the xorshift generator
- * @param x3 fourth word of the initial state for the xorshift generator
- */
- public L128X256MixRandom(long ah, long al, long sh, long sl, long x0, long x1, long x2, long x3) {
- // Force a to be odd.
- this.ah = ah;
- this.al = al | 1;
- this.sh = sh;
- this.sl = sl;
- 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 = RngSupport.mixStafford13(sh += RngSupport.GOLDEN_RATIO_64);
- this.x1 = RngSupport.mixStafford13(sh += RngSupport.GOLDEN_RATIO_64);
- this.x2 = RngSupport.mixStafford13(sh += RngSupport.GOLDEN_RATIO_64);
- this.x3 = RngSupport.mixStafford13(sh + RngSupport.GOLDEN_RATIO_64);
- }
- }
-
- /**
- * Creates a new instance of {@code L128X256MixRandom} using the
- * specified {@code long} value as the initial seed. Instances of
- * {@code L128X256MixRandom} created with the same seed in the same
- * program generate identical sequences of values.
- *
- * @param seed the initial seed
- */
- public L128X256MixRandom(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 seed is hashed by mixMurmur64 to produce the `a` parameter.
- // The seed is hashed by mixStafford13 to produce the initial `x0`,
- // which will then be used to produce the first generated value.
- // The other x values are filled in as if by a SplitMix PRNG with
- // GOLDEN_RATIO_64 as the gamma value and Stafford13 as the mixer.
- this(RngSupport.mixMurmur64(seed ^= RngSupport.SILVER_RATIO_64),
- RngSupport.mixMurmur64(seed += RngSupport.GOLDEN_RATIO_64),
- 0,
- 1,
- RngSupport.mixStafford13(seed),
- 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 L128X256MixRandom} 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 L128X256MixRandom() {
- // 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 L128X256MixRandom} using the specified array of
- * initial seed bytes. Instances of {@code L128X256MixRandom} created with the same
- * seed array in the same program execution generate identical sequences of values.
- *
- * @param seed the initial seed
- */
- public L128X256MixRandom(byte[] seed) {
- // Convert the seed to 6 long values, of which the last 4 are not all zero.
- long[] data = RngSupport.convertSeedBytesToLongs(seed, 6, 4);
- long ah = data[0], al = data[1], sh = data[2], sl = data[3], x0 = data[4], x1 = data[5], x2 = data[6], x3 = data[7];
- // Force a to be odd.
- this.ah = ah;
- this.al = al | 1;
- this.sh = sh;
- this.sl = sl;
- this.x0 = x0;
- this.x1 = x1;
- this.x2 = x2;
- this.x3 = x3;
- }
-
- /* ---------------- public methods ---------------- */
-
- /**
- * Constructs and returns a new instance of {@code L128X256MixRandom}
- * 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 {@code L128X256MixRandom} 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 {@code SplittableRng} 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 {@code L128X256MixRandom}
- */
- public L128X256MixRandom split(SplittableRng source) {
- // Literally pick a new instance "at random".
- return new L128X256MixRandom(source.nextLong(), source.nextLong(),
- source.nextLong(), source.nextLong(),
- source.nextLong(), source.nextLong(),
- source.nextLong(), source.nextLong());
- }
-
- /**
- * Returns a pseudorandom {@code long} value.
- *
- * @return a pseudorandom {@code long} value
- */
-
- public long nextLong() {
- final long z = sh + x0;
- // The LCG: in effect, s = ((1LL << 64) + m) * s + a, if only we had 128-bit arithmetic.
- final long u = m * sl;
- sh = (m * sh) + Math.multiplyHigh(m, sl) + sl + ah;
- sl = u + al;
- if (Long.compareUnsigned(sl, u) < 0) ++sh; // Handle the carry propagation from low half to high half.
- 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 RngSupport.mixLea64(z); // mixing function
- }
-
- public BigInteger period() { return thePeriod; }
-}