308 lines
12 KiB
Java
308 lines
12 KiB
Java
|
/*
|
||
|
|
* 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 (vigna@acm.org).
|
||
|
|
*
|
||
|
|
* 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;
|
||
|
|
}
|
||
|
|
|
||
|
|
}
|