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/* |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain, as explained at |
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* http://creativecommons.org/publicdomain/zero/1.0/ |
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*/ |
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|
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package java.util.concurrent; |
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|
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import java.io.ObjectStreamField; |
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import java.util.Random; |
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import java.util.Spliterator; |
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import java.util.concurrent.atomic.AtomicInteger; |
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import java.util.concurrent.atomic.AtomicLong; |
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import java.util.function.DoubleConsumer; |
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import java.util.function.IntConsumer; |
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import java.util.function.LongConsumer; |
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import java.util.stream.DoubleStream; |
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import java.util.stream.IntStream; |
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import java.util.stream.LongStream; |
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import java.util.stream.StreamSupport; |
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|
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/** |
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* A random number generator isolated to the current thread. Like the |
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* global {@link java.util.Random} generator used by the {@link |
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* java.lang.Math} class, a {@code ThreadLocalRandom} is initialized |
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* with an internally generated seed that may not otherwise be |
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* modified. When applicable, use of {@code ThreadLocalRandom} rather |
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* than shared {@code Random} objects in concurrent programs will |
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* typically encounter much less overhead and contention. Use of |
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* {@code ThreadLocalRandom} is particularly appropriate when multiple |
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* tasks (for example, each a {@link ForkJoinTask}) use random numbers |
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* in parallel in thread pools. |
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* |
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* <p>Usages of this class should typically be of the form: |
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* {@code ThreadLocalRandom.current().nextX(...)} (where |
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* {@code X} is {@code Int}, {@code Long}, etc). |
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* When all usages are of this form, it is never possible to |
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* accidently share a {@code ThreadLocalRandom} across multiple threads. |
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* |
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* <p>This class also provides additional commonly used bounded random |
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* generation methods. |
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* |
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* <p>Instances of {@code ThreadLocalRandom} are not cryptographically |
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* secure. Consider instead using {@link java.security.SecureRandom} |
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* in security-sensitive applications. Additionally, |
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* default-constructed instances do not use a cryptographically random |
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* seed unless the {@linkplain System#getProperty system property} |
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* {@code java.util.secureRandomSeed} is set to {@code true}. |
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* |
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* @since 1.7 |
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* @author Doug Lea |
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*/ |
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public class ThreadLocalRandom extends Random { |
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/* |
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* This class implements the java.util.Random API (and subclasses |
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* Random) using a single static instance that accesses random |
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* number state held in class Thread (primarily, field |
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* threadLocalRandomSeed). In doing so, it also provides a home |
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* for managing package-private utilities that rely on exactly the |
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* same state as needed to maintain the ThreadLocalRandom |
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* instances. We leverage the need for an initialization flag |
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* field to also use it as a "probe" -- a self-adjusting thread |
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* hash used for contention avoidance, as well as a secondary |
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* simpler (xorShift) random seed that is conservatively used to |
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* avoid otherwise surprising users by hijacking the |
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* ThreadLocalRandom sequence. The dual use is a marriage of |
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* convenience, but is a simple and efficient way of reducing |
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* application-level overhead and footprint of most concurrent |
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* programs. |
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* |
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* Even though this class subclasses java.util.Random, it uses the |
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* same basic algorithm as java.util.SplittableRandom. (See its |
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* internal documentation for explanations, which are not repeated |
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* here.) Because ThreadLocalRandoms are not splittable |
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* though, we use only a single 64bit gamma. |
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* |
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* Because this class is in a different package than class Thread, |
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* field access methods use Unsafe to bypass access control rules. |
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* To conform to the requirements of the Random superclass |
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* constructor, the common static ThreadLocalRandom maintains an |
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* "initialized" field for the sake of rejecting user calls to |
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* setSeed while still allowing a call from constructor. Note |
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* that serialization is completely unnecessary because there is |
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* only a static singleton. But we generate a serial form |
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* containing "rnd" and "initialized" fields to ensure |
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* compatibility across versions. |
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* |
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* Implementations of non-core methods are mostly the same as in |
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* SplittableRandom, that were in part derived from a previous |
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* version of this class. |
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* |
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* The nextLocalGaussian ThreadLocal supports the very rarely used |
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* nextGaussian method by providing a holder for the second of a |
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* pair of them. As is true for the base class version of this |
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* method, this time/space tradeoff is probably never worthwhile, |
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* but we provide identical statistical properties. |
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*/ |
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|
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private static long mix64(long z) { |
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z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL; |
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z = (z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L; |
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return z ^ (z >>> 33); |
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} |
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|
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private static int mix32(long z) { |
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z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL; |
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return (int)(((z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L) >>> 32); |
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} |
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|
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/** |
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* Field used only during singleton initialization. |
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* True when constructor completes. |
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*/ |
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boolean initialized; |
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|
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/** Constructor used only for static singleton */ |
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private ThreadLocalRandom() { |
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initialized = true; // false during super() call |
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} |
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|
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/** |
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* Initialize Thread fields for the current thread. Called only |
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* when Thread.threadLocalRandomProbe is zero, indicating that a |
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* thread local seed value needs to be generated. Note that even |
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* though the initialization is purely thread-local, we need to |
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* rely on (static) atomic generators to initialize the values. |
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*/ |
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static final void localInit() { |
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int p = probeGenerator.addAndGet(PROBE_INCREMENT); |
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int probe = (p == 0) ? 1 : p; // skip 0 |
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long seed = mix64(seeder.getAndAdd(SEEDER_INCREMENT)); |
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Thread t = Thread.currentThread(); |
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U.putLong(t, SEED, seed); |
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U.putInt(t, PROBE, probe); |
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} |
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|
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/** |
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* Returns the current thread's {@code ThreadLocalRandom}. |
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* |
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* @return the current thread's {@code ThreadLocalRandom} |
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*/ |
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public static ThreadLocalRandom current() { |
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if (U.getInt(Thread.currentThread(), PROBE) == 0) |
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localInit(); |
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return instance; |
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} |
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|
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/** |
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* Throws {@code UnsupportedOperationException}. Setting seeds in |
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* this generator is not supported. |
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* |
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* @throws UnsupportedOperationException always |
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*/ |
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public void setSeed(long seed) { |
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// only allow call from super() constructor |
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if (initialized) |
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throw new UnsupportedOperationException(); |
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} |
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|
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final long nextSeed() { |
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Thread t; long r; // read and update per-thread seed |
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U.putLong(t = Thread.currentThread(), SEED, |
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r = U.getLong(t, SEED) + GAMMA); |
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return r; |
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} |
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|
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// We must define this, but never use it. |
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protected int next(int bits) { |
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return (int)(mix64(nextSeed()) >>> (64 - bits)); |
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} |
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|
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/** |
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* The form of nextLong used by LongStream Spliterators. If |
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* origin is greater than bound, acts as unbounded form of |
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* nextLong, else as bounded form. |
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* |
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* @param origin the least value, unless greater than bound |
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* @param bound the upper bound (exclusive), must not equal origin |
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* @return a pseudorandom value |
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*/ |
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final long internalNextLong(long origin, long bound) { |
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long r = mix64(nextSeed()); |
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if (origin < bound) { |
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long n = bound - origin, m = n - 1; |
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if ((n & m) == 0L) // power of two |
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r = (r & m) + origin; |
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else if (n > 0L) { // reject over-represented candidates |
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for (long u = r >>> 1; // ensure nonnegative |
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u + m - (r = u % n) < 0L; // rejection check |
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u = mix64(nextSeed()) >>> 1) // retry |
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; |
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r += origin; |
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} |
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else { // range not representable as long |
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while (r < origin || r >= bound) |
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r = mix64(nextSeed()); |
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} |
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} |
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return r; |
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} |
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|
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/** |
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* The form of nextInt used by IntStream Spliterators. |
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* Exactly the same as long version, except for types. |
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* |
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* @param origin the least value, unless greater than bound |
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* @param bound the upper bound (exclusive), must not equal origin |
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* @return a pseudorandom value |
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*/ |
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final int internalNextInt(int origin, int bound) { |
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int r = mix32(nextSeed()); |
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if (origin < bound) { |
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int n = bound - origin, m = n - 1; |
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if ((n & m) == 0) |
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r = (r & m) + origin; |
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else if (n > 0) { |
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for (int u = r >>> 1; |
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u + m - (r = u % n) < 0; |
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u = mix32(nextSeed()) >>> 1) |
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; |
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r += origin; |
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} |
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else { |
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while (r < origin || r >= bound) |
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r = mix32(nextSeed()); |
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} |
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} |
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return r; |
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} |
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|
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/** |
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* The form of nextDouble used by DoubleStream Spliterators. |
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* |
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* @param origin the least value, unless greater than bound |
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* @param bound the upper bound (exclusive), must not equal origin |
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* @return a pseudorandom value |
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*/ |
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final double internalNextDouble(double origin, double bound) { |
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double r = (nextLong() >>> 11) * DOUBLE_UNIT; |
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if (origin < bound) { |
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r = r * (bound - origin) + origin; |
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if (r >= bound) // correct for rounding |
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r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1); |
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} |
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return r; |
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} |
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|
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/** |
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* Returns a pseudorandom {@code int} value. |
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* |
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* @return a pseudorandom {@code int} value |
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*/ |
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public int nextInt() { |
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return mix32(nextSeed()); |
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} |
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|
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/** |
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* Returns a pseudorandom {@code int} value between zero (inclusive) |
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* and the specified bound (exclusive). |
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* |
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* @param bound the upper bound (exclusive). Must be positive. |
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* @return a pseudorandom {@code int} value between zero |
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* (inclusive) and the bound (exclusive) |
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* @throws IllegalArgumentException if {@code bound} is not positive |
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*/ |
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public int nextInt(int bound) { |
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if (bound <= 0) |
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throw new IllegalArgumentException(BAD_BOUND); |
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int r = mix32(nextSeed()); |
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int m = bound - 1; |
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if ((bound & m) == 0) // power of two |
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r &= m; |
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else { // reject over-represented candidates |
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for (int u = r >>> 1; |
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u + m - (r = u % bound) < 0; |
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u = mix32(nextSeed()) >>> 1) |
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; |
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} |
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return r; |
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} |
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|
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/** |
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* Returns a pseudorandom {@code int} value between the specified |
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* origin (inclusive) and the specified bound (exclusive). |
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* |
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* @param origin the least value returned |
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* @param bound the upper bound (exclusive) |
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* @return a pseudorandom {@code int} value between the origin |
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* (inclusive) and the bound (exclusive) |
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* @throws IllegalArgumentException if {@code origin} is greater than |
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* or equal to {@code bound} |
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*/ |
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public int nextInt(int origin, int bound) { |
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if (origin >= bound) |
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throw new IllegalArgumentException(BAD_RANGE); |
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return internalNextInt(origin, bound); |
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} |
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|
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/** |
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* Returns a pseudorandom {@code long} value. |
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* |
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* @return a pseudorandom {@code long} value |
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*/ |
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public long nextLong() { |
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return mix64(nextSeed()); |
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} |
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|
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/** |
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* Returns a pseudorandom {@code long} value between zero (inclusive) |
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* and the specified bound (exclusive). |
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* |
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* @param bound the upper bound (exclusive). Must be positive. |
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* @return a pseudorandom {@code long} value between zero |
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* (inclusive) and the bound (exclusive) |
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* @throws IllegalArgumentException if {@code bound} is not positive |
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*/ |
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public long nextLong(long bound) { |
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if (bound <= 0) |
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throw new IllegalArgumentException(BAD_BOUND); |
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long r = mix64(nextSeed()); |
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long m = bound - 1; |
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if ((bound & m) == 0L) // power of two |
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r &= m; |
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else { // reject over-represented candidates |
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for (long u = r >>> 1; |
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u + m - (r = u % bound) < 0L; |
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u = mix64(nextSeed()) >>> 1) |
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; |
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} |
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return r; |
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} |
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|
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/** |
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* Returns a pseudorandom {@code long} value between the specified |
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* origin (inclusive) and the specified bound (exclusive). |
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* |
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* @param origin the least value returned |
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* @param bound the upper bound (exclusive) |
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* @return a pseudorandom {@code long} value between the origin |
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* (inclusive) and the bound (exclusive) |
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* @throws IllegalArgumentException if {@code origin} is greater than |
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* or equal to {@code bound} |
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*/ |
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public long nextLong(long origin, long bound) { |
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if (origin >= bound) |
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throw new IllegalArgumentException(BAD_RANGE); |
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return internalNextLong(origin, bound); |
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} |
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|
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/** |
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* Returns a pseudorandom {@code double} value between zero |
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* (inclusive) and one (exclusive). |
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* |
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* @return a pseudorandom {@code double} value between zero |
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* (inclusive) and one (exclusive) |
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*/ |
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public double nextDouble() { |
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return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT; |
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} |
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|
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/** |
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* Returns a pseudorandom {@code double} value between 0.0 |
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* (inclusive) and the specified bound (exclusive). |
364 |
* |
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* @param bound the upper bound (exclusive). Must be positive. |
366 |
* @return a pseudorandom {@code double} value between zero |
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* (inclusive) and the bound (exclusive) |
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* @throws IllegalArgumentException if {@code bound} is not positive |
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*/ |
370 |
public double nextDouble(double bound) { |
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if (!(bound > 0.0)) |
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throw new IllegalArgumentException(BAD_BOUND); |
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double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound; |
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return (result < bound) ? result : // correct for rounding |
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Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1); |
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} |
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|
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/** |
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* Returns a pseudorandom {@code double} value between the specified |
380 |
* origin (inclusive) and bound (exclusive). |
381 |
* |
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* @param origin the least value returned |
383 |
* @param bound the upper bound (exclusive) |
384 |
* @return a pseudorandom {@code double} value between the origin |
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* (inclusive) and the bound (exclusive) |
386 |
* @throws IllegalArgumentException if {@code origin} is greater than |
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* or equal to {@code bound} |
388 |
*/ |
389 |
public double nextDouble(double origin, double bound) { |
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if (!(origin < bound)) |
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throw new IllegalArgumentException(BAD_RANGE); |
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return internalNextDouble(origin, bound); |
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} |
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|
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/** |
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* Returns a pseudorandom {@code boolean} value. |
397 |
* |
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* @return a pseudorandom {@code boolean} value |
399 |
*/ |
400 |
public boolean nextBoolean() { |
401 |
return mix32(nextSeed()) < 0; |
402 |
} |
403 |
|
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/** |
405 |
* Returns a pseudorandom {@code float} value between zero |
406 |
* (inclusive) and one (exclusive). |
407 |
* |
408 |
* @return a pseudorandom {@code float} value between zero |
409 |
* (inclusive) and one (exclusive) |
410 |
*/ |
411 |
public float nextFloat() { |
412 |
return (mix32(nextSeed()) >>> 8) * FLOAT_UNIT; |
413 |
} |
414 |
|
415 |
public double nextGaussian() { |
416 |
// Use nextLocalGaussian instead of nextGaussian field |
417 |
Double d = nextLocalGaussian.get(); |
418 |
if (d != null) { |
419 |
nextLocalGaussian.set(null); |
420 |
return d.doubleValue(); |
421 |
} |
422 |
double v1, v2, s; |
423 |
do { |
424 |
v1 = 2 * nextDouble() - 1; // between -1 and 1 |
425 |
v2 = 2 * nextDouble() - 1; // between -1 and 1 |
426 |
s = v1 * v1 + v2 * v2; |
427 |
} while (s >= 1 || s == 0); |
428 |
double multiplier = StrictMath.sqrt(-2 * StrictMath.log(s)/s); |
429 |
nextLocalGaussian.set(Double.valueOf(v2 * multiplier)); |
430 |
return v1 * multiplier; |
431 |
} |
432 |
|
433 |
// stream methods, coded in a way intended to better isolate for |
434 |
// maintenance purposes the small differences across forms. |
435 |
|
436 |
/** |
437 |
* Returns a stream producing the given {@code streamSize} number of |
438 |
* pseudorandom {@code int} values. |
439 |
* |
440 |
* @param streamSize the number of values to generate |
441 |
* @return a stream of pseudorandom {@code int} values |
442 |
* @throws IllegalArgumentException if {@code streamSize} is |
443 |
* less than zero |
444 |
* @since 1.8 |
445 |
*/ |
446 |
public IntStream ints(long streamSize) { |
447 |
if (streamSize < 0L) |
448 |
throw new IllegalArgumentException(BAD_SIZE); |
449 |
return StreamSupport.intStream |
450 |
(new RandomIntsSpliterator |
451 |
(0L, streamSize, Integer.MAX_VALUE, 0), |
452 |
false); |
453 |
} |
454 |
|
455 |
/** |
456 |
* Returns an effectively unlimited stream of pseudorandom {@code int} |
457 |
* values. |
458 |
* |
459 |
* @implNote This method is implemented to be equivalent to {@code |
460 |
* ints(Long.MAX_VALUE)}. |
461 |
* |
462 |
* @return a stream of pseudorandom {@code int} values |
463 |
* @since 1.8 |
464 |
*/ |
465 |
public IntStream ints() { |
466 |
return StreamSupport.intStream |
467 |
(new RandomIntsSpliterator |
468 |
(0L, Long.MAX_VALUE, Integer.MAX_VALUE, 0), |
469 |
false); |
470 |
} |
471 |
|
472 |
/** |
473 |
* Returns a stream producing the given {@code streamSize} number |
474 |
* of pseudorandom {@code int} values, each conforming to the given |
475 |
* origin (inclusive) and bound (exclusive). |
476 |
* |
477 |
* @param streamSize the number of values to generate |
478 |
* @param randomNumberOrigin the origin (inclusive) of each random value |
479 |
* @param randomNumberBound the bound (exclusive) of each random value |
480 |
* @return a stream of pseudorandom {@code int} values, |
481 |
* each with the given origin (inclusive) and bound (exclusive) |
482 |
* @throws IllegalArgumentException if {@code streamSize} is |
483 |
* less than zero, or {@code randomNumberOrigin} |
484 |
* is greater than or equal to {@code randomNumberBound} |
485 |
* @since 1.8 |
486 |
*/ |
487 |
public IntStream ints(long streamSize, int randomNumberOrigin, |
488 |
int randomNumberBound) { |
489 |
if (streamSize < 0L) |
490 |
throw new IllegalArgumentException(BAD_SIZE); |
491 |
if (randomNumberOrigin >= randomNumberBound) |
492 |
throw new IllegalArgumentException(BAD_RANGE); |
493 |
return StreamSupport.intStream |
494 |
(new RandomIntsSpliterator |
495 |
(0L, streamSize, randomNumberOrigin, randomNumberBound), |
496 |
false); |
497 |
} |
498 |
|
499 |
/** |
500 |
* Returns an effectively unlimited stream of pseudorandom {@code |
501 |
* int} values, each conforming to the given origin (inclusive) and bound |
502 |
* (exclusive). |
503 |
* |
504 |
* @implNote This method is implemented to be equivalent to {@code |
505 |
* ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. |
506 |
* |
507 |
* @param randomNumberOrigin the origin (inclusive) of each random value |
508 |
* @param randomNumberBound the bound (exclusive) of each random value |
509 |
* @return a stream of pseudorandom {@code int} values, |
510 |
* each with the given origin (inclusive) and bound (exclusive) |
511 |
* @throws IllegalArgumentException if {@code randomNumberOrigin} |
512 |
* is greater than or equal to {@code randomNumberBound} |
513 |
* @since 1.8 |
514 |
*/ |
515 |
public IntStream ints(int randomNumberOrigin, int randomNumberBound) { |
516 |
if (randomNumberOrigin >= randomNumberBound) |
517 |
throw new IllegalArgumentException(BAD_RANGE); |
518 |
return StreamSupport.intStream |
519 |
(new RandomIntsSpliterator |
520 |
(0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), |
521 |
false); |
522 |
} |
523 |
|
524 |
/** |
525 |
* Returns a stream producing the given {@code streamSize} number of |
526 |
* pseudorandom {@code long} values. |
527 |
* |
528 |
* @param streamSize the number of values to generate |
529 |
* @return a stream of pseudorandom {@code long} values |
530 |
* @throws IllegalArgumentException if {@code streamSize} is |
531 |
* less than zero |
532 |
* @since 1.8 |
533 |
*/ |
534 |
public LongStream longs(long streamSize) { |
535 |
if (streamSize < 0L) |
536 |
throw new IllegalArgumentException(BAD_SIZE); |
537 |
return StreamSupport.longStream |
538 |
(new RandomLongsSpliterator |
539 |
(0L, streamSize, Long.MAX_VALUE, 0L), |
540 |
false); |
541 |
} |
542 |
|
543 |
/** |
544 |
* Returns an effectively unlimited stream of pseudorandom {@code long} |
545 |
* values. |
546 |
* |
547 |
* @implNote This method is implemented to be equivalent to {@code |
548 |
* longs(Long.MAX_VALUE)}. |
549 |
* |
550 |
* @return a stream of pseudorandom {@code long} values |
551 |
* @since 1.8 |
552 |
*/ |
553 |
public LongStream longs() { |
554 |
return StreamSupport.longStream |
555 |
(new RandomLongsSpliterator |
556 |
(0L, Long.MAX_VALUE, Long.MAX_VALUE, 0L), |
557 |
false); |
558 |
} |
559 |
|
560 |
/** |
561 |
* Returns a stream producing the given {@code streamSize} number of |
562 |
* pseudorandom {@code long}, each conforming to the given origin |
563 |
* (inclusive) and bound (exclusive). |
564 |
* |
565 |
* @param streamSize the number of values to generate |
566 |
* @param randomNumberOrigin the origin (inclusive) of each random value |
567 |
* @param randomNumberBound the bound (exclusive) of each random value |
568 |
* @return a stream of pseudorandom {@code long} values, |
569 |
* each with the given origin (inclusive) and bound (exclusive) |
570 |
* @throws IllegalArgumentException if {@code streamSize} is |
571 |
* less than zero, or {@code randomNumberOrigin} |
572 |
* is greater than or equal to {@code randomNumberBound} |
573 |
* @since 1.8 |
574 |
*/ |
575 |
public LongStream longs(long streamSize, long randomNumberOrigin, |
576 |
long randomNumberBound) { |
577 |
if (streamSize < 0L) |
578 |
throw new IllegalArgumentException(BAD_SIZE); |
579 |
if (randomNumberOrigin >= randomNumberBound) |
580 |
throw new IllegalArgumentException(BAD_RANGE); |
581 |
return StreamSupport.longStream |
582 |
(new RandomLongsSpliterator |
583 |
(0L, streamSize, randomNumberOrigin, randomNumberBound), |
584 |
false); |
585 |
} |
586 |
|
587 |
/** |
588 |
* Returns an effectively unlimited stream of pseudorandom {@code |
589 |
* long} values, each conforming to the given origin (inclusive) and bound |
590 |
* (exclusive). |
591 |
* |
592 |
* @implNote This method is implemented to be equivalent to {@code |
593 |
* longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. |
594 |
* |
595 |
* @param randomNumberOrigin the origin (inclusive) of each random value |
596 |
* @param randomNumberBound the bound (exclusive) of each random value |
597 |
* @return a stream of pseudorandom {@code long} values, |
598 |
* each with the given origin (inclusive) and bound (exclusive) |
599 |
* @throws IllegalArgumentException if {@code randomNumberOrigin} |
600 |
* is greater than or equal to {@code randomNumberBound} |
601 |
* @since 1.8 |
602 |
*/ |
603 |
public LongStream longs(long randomNumberOrigin, long randomNumberBound) { |
604 |
if (randomNumberOrigin >= randomNumberBound) |
605 |
throw new IllegalArgumentException(BAD_RANGE); |
606 |
return StreamSupport.longStream |
607 |
(new RandomLongsSpliterator |
608 |
(0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), |
609 |
false); |
610 |
} |
611 |
|
612 |
/** |
613 |
* Returns a stream producing the given {@code streamSize} number of |
614 |
* pseudorandom {@code double} values, each between zero |
615 |
* (inclusive) and one (exclusive). |
616 |
* |
617 |
* @param streamSize the number of values to generate |
618 |
* @return a stream of {@code double} values |
619 |
* @throws IllegalArgumentException if {@code streamSize} is |
620 |
* less than zero |
621 |
* @since 1.8 |
622 |
*/ |
623 |
public DoubleStream doubles(long streamSize) { |
624 |
if (streamSize < 0L) |
625 |
throw new IllegalArgumentException(BAD_SIZE); |
626 |
return StreamSupport.doubleStream |
627 |
(new RandomDoublesSpliterator |
628 |
(0L, streamSize, Double.MAX_VALUE, 0.0), |
629 |
false); |
630 |
} |
631 |
|
632 |
/** |
633 |
* Returns an effectively unlimited stream of pseudorandom {@code |
634 |
* double} values, each between zero (inclusive) and one |
635 |
* (exclusive). |
636 |
* |
637 |
* @implNote This method is implemented to be equivalent to {@code |
638 |
* doubles(Long.MAX_VALUE)}. |
639 |
* |
640 |
* @return a stream of pseudorandom {@code double} values |
641 |
* @since 1.8 |
642 |
*/ |
643 |
public DoubleStream doubles() { |
644 |
return StreamSupport.doubleStream |
645 |
(new RandomDoublesSpliterator |
646 |
(0L, Long.MAX_VALUE, Double.MAX_VALUE, 0.0), |
647 |
false); |
648 |
} |
649 |
|
650 |
/** |
651 |
* Returns a stream producing the given {@code streamSize} number of |
652 |
* pseudorandom {@code double} values, each conforming to the given origin |
653 |
* (inclusive) and bound (exclusive). |
654 |
* |
655 |
* @param streamSize the number of values to generate |
656 |
* @param randomNumberOrigin the origin (inclusive) of each random value |
657 |
* @param randomNumberBound the bound (exclusive) of each random value |
658 |
* @return a stream of pseudorandom {@code double} values, |
659 |
* each with the given origin (inclusive) and bound (exclusive) |
660 |
* @throws IllegalArgumentException if {@code streamSize} is |
661 |
* less than zero, or {@code randomNumberOrigin} |
662 |
* is greater than or equal to {@code randomNumberBound} |
663 |
* @since 1.8 |
664 |
*/ |
665 |
public DoubleStream doubles(long streamSize, double randomNumberOrigin, |
666 |
double randomNumberBound) { |
667 |
if (streamSize < 0L) |
668 |
throw new IllegalArgumentException(BAD_SIZE); |
669 |
if (!(randomNumberOrigin < randomNumberBound)) |
670 |
throw new IllegalArgumentException(BAD_RANGE); |
671 |
return StreamSupport.doubleStream |
672 |
(new RandomDoublesSpliterator |
673 |
(0L, streamSize, randomNumberOrigin, randomNumberBound), |
674 |
false); |
675 |
} |
676 |
|
677 |
/** |
678 |
* Returns an effectively unlimited stream of pseudorandom {@code |
679 |
* double} values, each conforming to the given origin (inclusive) and bound |
680 |
* (exclusive). |
681 |
* |
682 |
* @implNote This method is implemented to be equivalent to {@code |
683 |
* doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. |
684 |
* |
685 |
* @param randomNumberOrigin the origin (inclusive) of each random value |
686 |
* @param randomNumberBound the bound (exclusive) of each random value |
687 |
* @return a stream of pseudorandom {@code double} values, |
688 |
* each with the given origin (inclusive) and bound (exclusive) |
689 |
* @throws IllegalArgumentException if {@code randomNumberOrigin} |
690 |
* is greater than or equal to {@code randomNumberBound} |
691 |
* @since 1.8 |
692 |
*/ |
693 |
public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) { |
694 |
if (!(randomNumberOrigin < randomNumberBound)) |
695 |
throw new IllegalArgumentException(BAD_RANGE); |
696 |
return StreamSupport.doubleStream |
697 |
(new RandomDoublesSpliterator |
698 |
(0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), |
699 |
false); |
700 |
} |
701 |
|
702 |
/** |
703 |
* Spliterator for int streams. We multiplex the four int |
704 |
* versions into one class by treating a bound less than origin as |
705 |
* unbounded, and also by treating "infinite" as equivalent to |
706 |
* Long.MAX_VALUE. For splits, it uses the standard divide-by-two |
707 |
* approach. The long and double versions of this class are |
708 |
* identical except for types. |
709 |
*/ |
710 |
private static final class RandomIntsSpliterator |
711 |
implements Spliterator.OfInt { |
712 |
long index; |
713 |
final long fence; |
714 |
final int origin; |
715 |
final int bound; |
716 |
RandomIntsSpliterator(long index, long fence, |
717 |
int origin, int bound) { |
718 |
this.index = index; this.fence = fence; |
719 |
this.origin = origin; this.bound = bound; |
720 |
} |
721 |
|
722 |
public RandomIntsSpliterator trySplit() { |
723 |
long i = index, m = (i + fence) >>> 1; |
724 |
return (m <= i) ? null : |
725 |
new RandomIntsSpliterator(i, index = m, origin, bound); |
726 |
} |
727 |
|
728 |
public long estimateSize() { |
729 |
return fence - index; |
730 |
} |
731 |
|
732 |
public int characteristics() { |
733 |
return (Spliterator.SIZED | Spliterator.SUBSIZED | |
734 |
Spliterator.NONNULL | Spliterator.IMMUTABLE); |
735 |
} |
736 |
|
737 |
public boolean tryAdvance(IntConsumer consumer) { |
738 |
if (consumer == null) throw new NullPointerException(); |
739 |
long i = index, f = fence; |
740 |
if (i < f) { |
741 |
consumer.accept(ThreadLocalRandom.current().internalNextInt(origin, bound)); |
742 |
index = i + 1; |
743 |
return true; |
744 |
} |
745 |
return false; |
746 |
} |
747 |
|
748 |
public void forEachRemaining(IntConsumer consumer) { |
749 |
if (consumer == null) throw new NullPointerException(); |
750 |
long i = index, f = fence; |
751 |
if (i < f) { |
752 |
index = f; |
753 |
int o = origin, b = bound; |
754 |
ThreadLocalRandom rng = ThreadLocalRandom.current(); |
755 |
do { |
756 |
consumer.accept(rng.internalNextInt(o, b)); |
757 |
} while (++i < f); |
758 |
} |
759 |
} |
760 |
} |
761 |
|
762 |
/** |
763 |
* Spliterator for long streams. |
764 |
*/ |
765 |
private static final class RandomLongsSpliterator |
766 |
implements Spliterator.OfLong { |
767 |
long index; |
768 |
final long fence; |
769 |
final long origin; |
770 |
final long bound; |
771 |
RandomLongsSpliterator(long index, long fence, |
772 |
long origin, long bound) { |
773 |
this.index = index; this.fence = fence; |
774 |
this.origin = origin; this.bound = bound; |
775 |
} |
776 |
|
777 |
public RandomLongsSpliterator trySplit() { |
778 |
long i = index, m = (i + fence) >>> 1; |
779 |
return (m <= i) ? null : |
780 |
new RandomLongsSpliterator(i, index = m, origin, bound); |
781 |
} |
782 |
|
783 |
public long estimateSize() { |
784 |
return fence - index; |
785 |
} |
786 |
|
787 |
public int characteristics() { |
788 |
return (Spliterator.SIZED | Spliterator.SUBSIZED | |
789 |
Spliterator.NONNULL | Spliterator.IMMUTABLE); |
790 |
} |
791 |
|
792 |
public boolean tryAdvance(LongConsumer consumer) { |
793 |
if (consumer == null) throw new NullPointerException(); |
794 |
long i = index, f = fence; |
795 |
if (i < f) { |
796 |
consumer.accept(ThreadLocalRandom.current().internalNextLong(origin, bound)); |
797 |
index = i + 1; |
798 |
return true; |
799 |
} |
800 |
return false; |
801 |
} |
802 |
|
803 |
public void forEachRemaining(LongConsumer consumer) { |
804 |
if (consumer == null) throw new NullPointerException(); |
805 |
long i = index, f = fence; |
806 |
if (i < f) { |
807 |
index = f; |
808 |
long o = origin, b = bound; |
809 |
ThreadLocalRandom rng = ThreadLocalRandom.current(); |
810 |
do { |
811 |
consumer.accept(rng.internalNextLong(o, b)); |
812 |
} while (++i < f); |
813 |
} |
814 |
} |
815 |
|
816 |
} |
817 |
|
818 |
/** |
819 |
* Spliterator for double streams. |
820 |
*/ |
821 |
private static final class RandomDoublesSpliterator |
822 |
implements Spliterator.OfDouble { |
823 |
long index; |
824 |
final long fence; |
825 |
final double origin; |
826 |
final double bound; |
827 |
RandomDoublesSpliterator(long index, long fence, |
828 |
double origin, double bound) { |
829 |
this.index = index; this.fence = fence; |
830 |
this.origin = origin; this.bound = bound; |
831 |
} |
832 |
|
833 |
public RandomDoublesSpliterator trySplit() { |
834 |
long i = index, m = (i + fence) >>> 1; |
835 |
return (m <= i) ? null : |
836 |
new RandomDoublesSpliterator(i, index = m, origin, bound); |
837 |
} |
838 |
|
839 |
public long estimateSize() { |
840 |
return fence - index; |
841 |
} |
842 |
|
843 |
public int characteristics() { |
844 |
return (Spliterator.SIZED | Spliterator.SUBSIZED | |
845 |
Spliterator.NONNULL | Spliterator.IMMUTABLE); |
846 |
} |
847 |
|
848 |
public boolean tryAdvance(DoubleConsumer consumer) { |
849 |
if (consumer == null) throw new NullPointerException(); |
850 |
long i = index, f = fence; |
851 |
if (i < f) { |
852 |
consumer.accept(ThreadLocalRandom.current().internalNextDouble(origin, bound)); |
853 |
index = i + 1; |
854 |
return true; |
855 |
} |
856 |
return false; |
857 |
} |
858 |
|
859 |
public void forEachRemaining(DoubleConsumer consumer) { |
860 |
if (consumer == null) throw new NullPointerException(); |
861 |
long i = index, f = fence; |
862 |
if (i < f) { |
863 |
index = f; |
864 |
double o = origin, b = bound; |
865 |
ThreadLocalRandom rng = ThreadLocalRandom.current(); |
866 |
do { |
867 |
consumer.accept(rng.internalNextDouble(o, b)); |
868 |
} while (++i < f); |
869 |
} |
870 |
} |
871 |
} |
872 |
|
873 |
|
874 |
// Within-package utilities |
875 |
|
876 |
/* |
877 |
* Descriptions of the usages of the methods below can be found in |
878 |
* the classes that use them. Briefly, a thread's "probe" value is |
879 |
* a non-zero hash code that (probably) does not collide with |
880 |
* other existing threads with respect to any power of two |
881 |
* collision space. When it does collide, it is pseudo-randomly |
882 |
* adjusted (using a Marsaglia XorShift). The nextSecondarySeed |
883 |
* method is used in the same contexts as ThreadLocalRandom, but |
884 |
* only for transient usages such as random adaptive spin/block |
885 |
* sequences for which a cheap RNG suffices and for which it could |
886 |
* in principle disrupt user-visible statistical properties of the |
887 |
* main ThreadLocalRandom if we were to use it. |
888 |
* |
889 |
* Note: Because of package-protection issues, versions of some |
890 |
* these methods also appear in some subpackage classes. |
891 |
*/ |
892 |
|
893 |
/** |
894 |
* Returns the probe value for the current thread without forcing |
895 |
* initialization. Note that invoking ThreadLocalRandom.current() |
896 |
* can be used to force initialization on zero return. |
897 |
*/ |
898 |
static final int getProbe() { |
899 |
return U.getInt(Thread.currentThread(), PROBE); |
900 |
} |
901 |
|
902 |
/** |
903 |
* Pseudo-randomly advances and records the given probe value for the |
904 |
* given thread. |
905 |
*/ |
906 |
static final int advanceProbe(int probe) { |
907 |
probe ^= probe << 13; // xorshift |
908 |
probe ^= probe >>> 17; |
909 |
probe ^= probe << 5; |
910 |
U.putInt(Thread.currentThread(), PROBE, probe); |
911 |
return probe; |
912 |
} |
913 |
|
914 |
/** |
915 |
* Returns the pseudo-randomly initialized or updated secondary seed. |
916 |
*/ |
917 |
static final int nextSecondarySeed() { |
918 |
int r; |
919 |
Thread t = Thread.currentThread(); |
920 |
if ((r = U.getInt(t, SECONDARY)) != 0) { |
921 |
r ^= r << 13; // xorshift |
922 |
r ^= r >>> 17; |
923 |
r ^= r << 5; |
924 |
} |
925 |
else if ((r = mix32(seeder.getAndAdd(SEEDER_INCREMENT))) == 0) |
926 |
r = 1; // avoid zero |
927 |
U.putInt(t, SECONDARY, r); |
928 |
return r; |
929 |
} |
930 |
|
931 |
// Serialization support |
932 |
|
933 |
private static final long serialVersionUID = -5851777807851030925L; |
934 |
|
935 |
/** |
936 |
* @serialField rnd long |
937 |
* seed for random computations |
938 |
* @serialField initialized boolean |
939 |
* always true |
940 |
*/ |
941 |
private static final ObjectStreamField[] serialPersistentFields = { |
942 |
new ObjectStreamField("rnd", long.class), |
943 |
new ObjectStreamField("initialized", boolean.class), |
944 |
}; |
945 |
|
946 |
/** |
947 |
* Saves the {@code ThreadLocalRandom} to a stream (that is, serializes it). |
948 |
* @param s the stream |
949 |
* @throws java.io.IOException if an I/O error occurs |
950 |
*/ |
951 |
private void writeObject(java.io.ObjectOutputStream s) |
952 |
throws java.io.IOException { |
953 |
|
954 |
java.io.ObjectOutputStream.PutField fields = s.putFields(); |
955 |
fields.put("rnd", U.getLong(Thread.currentThread(), SEED)); |
956 |
fields.put("initialized", true); |
957 |
s.writeFields(); |
958 |
} |
959 |
|
960 |
/** |
961 |
* Returns the {@link #current() current} thread's {@code ThreadLocalRandom}. |
962 |
* @return the {@link #current() current} thread's {@code ThreadLocalRandom} |
963 |
*/ |
964 |
private Object readResolve() { |
965 |
return current(); |
966 |
} |
967 |
|
968 |
// Static initialization |
969 |
|
970 |
/** |
971 |
* The seed increment. |
972 |
*/ |
973 |
private static final long GAMMA = 0x9e3779b97f4a7c15L; |
974 |
|
975 |
/** |
976 |
* The increment for generating probe values. |
977 |
*/ |
978 |
private static final int PROBE_INCREMENT = 0x9e3779b9; |
979 |
|
980 |
/** |
981 |
* The increment of seeder per new instance. |
982 |
*/ |
983 |
private static final long SEEDER_INCREMENT = 0xbb67ae8584caa73bL; |
984 |
|
985 |
// Constants from SplittableRandom |
986 |
private static final double DOUBLE_UNIT = 0x1.0p-53; // 1.0 / (1L << 53) |
987 |
private static final float FLOAT_UNIT = 0x1.0p-24f; // 1.0f / (1 << 24) |
988 |
|
989 |
// IllegalArgumentException messages |
990 |
static final String BAD_BOUND = "bound must be positive"; |
991 |
static final String BAD_RANGE = "bound must be greater than origin"; |
992 |
static final String BAD_SIZE = "size must be non-negative"; |
993 |
|
994 |
// Unsafe mechanics |
995 |
private static final sun.misc.Unsafe U = sun.misc.Unsafe.getUnsafe(); |
996 |
private static final long SEED; |
997 |
private static final long PROBE; |
998 |
private static final long SECONDARY; |
999 |
static { |
1000 |
try { |
1001 |
SEED = U.objectFieldOffset |
1002 |
(Thread.class.getDeclaredField("threadLocalRandomSeed")); |
1003 |
PROBE = U.objectFieldOffset |
1004 |
(Thread.class.getDeclaredField("threadLocalRandomProbe")); |
1005 |
SECONDARY = U.objectFieldOffset |
1006 |
(Thread.class.getDeclaredField("threadLocalRandomSecondarySeed")); |
1007 |
} catch (ReflectiveOperationException e) { |
1008 |
throw new Error(e); |
1009 |
} |
1010 |
} |
1011 |
|
1012 |
/** Rarely-used holder for the second of a pair of Gaussians */ |
1013 |
private static final ThreadLocal<Double> nextLocalGaussian = |
1014 |
new ThreadLocal<>(); |
1015 |
|
1016 |
/** Generates per-thread initialization/probe field */ |
1017 |
private static final AtomicInteger probeGenerator = new AtomicInteger(); |
1018 |
|
1019 |
/** The common ThreadLocalRandom */ |
1020 |
static final ThreadLocalRandom instance = new ThreadLocalRandom(); |
1021 |
|
1022 |
/** |
1023 |
* The next seed for default constructors. |
1024 |
*/ |
1025 |
private static final AtomicLong seeder |
1026 |
= new AtomicLong(mix64(System.currentTimeMillis()) ^ |
1027 |
mix64(System.nanoTime())); |
1028 |
|
1029 |
// at end of <clinit> to survive static initialization circularity |
1030 |
static { |
1031 |
if (java.security.AccessController.doPrivileged( |
1032 |
new java.security.PrivilegedAction<Boolean>() { |
1033 |
public Boolean run() { |
1034 |
return Boolean.getBoolean("java.util.secureRandomSeed"); |
1035 |
}})) { |
1036 |
byte[] seedBytes = java.security.SecureRandom.getSeed(8); |
1037 |
long s = (long)seedBytes[0] & 0xffL; |
1038 |
for (int i = 1; i < 8; ++i) |
1039 |
s = (s << 8) | ((long)seedBytes[i] & 0xffL); |
1040 |
seeder.set(s); |
1041 |
} |
1042 |
} |
1043 |
} |