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/* |
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* Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved. |
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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* |
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* This code is free software; you can redistribute it and/or modify it |
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* under the terms of the GNU General Public License version 2 only, as |
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* published by the Free Software Foundation. Oracle designates this |
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* particular file as subject to the "Classpath" exception as provided |
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* by Oracle in the LICENSE file that accompanied this code. |
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* |
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* This code is distributed in the hope that it will be useful, but WITHOUT |
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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* version 2 for more details (a copy is included in the LICENSE file that |
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* accompanied this code). |
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* |
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* You should have received a copy of the GNU General Public License version |
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* 2 along with this work; if not, write to the Free Software Foundation, |
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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* |
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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* or visit www.oracle.com if you need additional information or have any |
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* questions. |
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*/ |
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|
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package java.util; |
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|
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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 generator of uniform pseudorandom values applicable for use in |
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* (among other contexts) isolated parallel computations that may |
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* generate subtasks. Class {@code SplittableRandom} supports methods for |
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* producing pseudorandom numbers of type {@code int}, {@code long}, |
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* and {@code double} with similar usages as for class |
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* {@link java.util.Random} but differs in the following ways: |
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* |
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* <ul> |
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* |
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* <li>Series of generated values pass the DieHarder suite testing |
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* independence and uniformity properties of random number generators. |
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* (Most recently validated with <a |
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* href="http://www.phy.duke.edu/~rgb/General/dieharder.php"> version |
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* 3.31.1</a>.) These tests validate only the methods for certain |
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* types and ranges, but similar properties are expected to hold, at |
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* least approximately, for others as well. The <em>period</em> |
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* (length of any series of generated values before it repeats) is at |
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* least 2<sup>64</sup>. |
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* |
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* <li>Method {@link #split} constructs and returns a new |
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* SplittableRandom instance that shares no mutable state with the |
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* current instance. However, with very high probability, the |
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* values collectively generated by the two objects have the same |
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* statistical properties as if the same quantity of values were |
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* generated by a single thread using a single {@code |
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* SplittableRandom} object. |
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* |
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* <li>Instances of SplittableRandom are <em>not</em> thread-safe. |
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* They are designed to be split, not shared, across threads. For |
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* example, a {@link java.util.concurrent.ForkJoinTask |
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* fork/join-style} computation using random numbers might include a |
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* construction of the form {@code new |
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* Subtask(aSplittableRandom.split()).fork()}. |
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* |
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* <li>This class provides additional methods for generating random |
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* streams, that employ the above techniques when used in {@code |
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* stream.parallel()} mode. |
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* |
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* </ul> |
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* |
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* <p>Instances of {@code SplittableRandom} 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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* @author Guy Steele |
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* @author Doug Lea |
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* @since 1.8 |
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*/ |
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public final class SplittableRandom { |
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|
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/* |
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* Implementation Overview. |
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* |
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* This algorithm was inspired by the "DotMix" algorithm by |
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* Leiserson, Schardl, and Sukha "Deterministic Parallel |
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* Random-Number Generation for Dynamic-Multithreading Platforms", |
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* PPoPP 2012, as well as those in "Parallel random numbers: as |
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* easy as 1, 2, 3" by Salmon, Morae, Dror, and Shaw, SC 2011. It |
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* differs mainly in simplifying and cheapening operations. |
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* |
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* The primary update step (method nextSeed()) is to add a |
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* constant ("gamma") to the current (64 bit) seed, forming a |
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* simple sequence. The seed and the gamma values for any two |
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* SplittableRandom instances are highly likely to be different. |
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* |
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* Methods nextLong, nextInt, and derivatives do not return the |
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* sequence (seed) values, but instead a hash-like bit-mix of |
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* their bits, producing more independently distributed sequences. |
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* For nextLong, the mix64 function is based on David Stafford's |
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* (http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html) |
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* "Mix13" variant of the "64-bit finalizer" function in Austin |
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* Appleby's MurmurHash3 algorithm (see |
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* http://code.google.com/p/smhasher/wiki/MurmurHash3). The mix32 |
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* function is based on Stafford's Mix04 mix function, but returns |
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* the upper 32 bits cast as int. |
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* |
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* The split operation uses the current generator to form the seed |
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* and gamma for another SplittableRandom. To conservatively |
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* avoid potential correlations between seed and value generation, |
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* gamma selection (method mixGamma) uses different |
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* (Murmurhash3's) mix constants. To avoid potential weaknesses |
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* in bit-mixing transformations, we restrict gammas to odd values |
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* with at least 24 0-1 or 1-0 bit transitions. Rather than |
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* rejecting candidates with too few or too many bits set, method |
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* mixGamma flips some bits (which has the effect of mapping at |
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* most 4 to any given gamma value). This reduces the effective |
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* set of 64bit odd gamma values by about 2%, and serves as an |
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* automated screening for sequence constant selection that is |
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* left as an empirical decision in some other hashing and crypto |
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* algorithms. |
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* |
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* The resulting generator thus transforms a sequence in which |
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* (typically) many bits change on each step, with an inexpensive |
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* mixer with good (but less than cryptographically secure) |
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* avalanching. |
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* |
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* The default (no-argument) constructor, in essence, invokes |
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* split() for a common "defaultGen" SplittableRandom. Unlike |
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* other cases, this split must be performed in a thread-safe |
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* manner, so we use an AtomicLong to represent the seed rather |
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* than use an explicit SplittableRandom. To bootstrap the |
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* defaultGen, we start off using a seed based on current time |
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* unless the java.util.secureRandomSeed property is set. This |
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* serves as a slimmed-down (and insecure) variant of SecureRandom |
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* that also avoids stalls that may occur when using /dev/random. |
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* |
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* It is a relatively simple matter to apply the basic design here |
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* to use 128 bit seeds. However, emulating 128bit arithmetic and |
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* carrying around twice the state add more overhead than appears |
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* warranted for current usages. |
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* |
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* File organization: First the non-public methods that constitute |
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* the main algorithm, then the main public methods, followed by |
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* some custom spliterator classes needed for stream methods. |
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*/ |
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|
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/** |
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* The golden ratio scaled to 64bits, used as the initial gamma |
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* value for (unsplit) SplittableRandoms. |
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*/ |
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private static final long GOLDEN_GAMMA = 0x9e3779b97f4a7c15L; |
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|
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/** |
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* The least non-zero value returned by nextDouble(). This value |
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* is scaled by a random value of 53 bits to produce a result. |
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*/ |
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private static final double DOUBLE_UNIT = 0x1.0p-53; // 1.0 / (1L << 53); |
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|
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/** |
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* The seed. Updated only via method nextSeed. |
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*/ |
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private long seed; |
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|
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/** |
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* The step value. |
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*/ |
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private final long gamma; |
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|
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/** |
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* Internal constructor used by all others except default constructor. |
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*/ |
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private SplittableRandom(long seed, long gamma) { |
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this.seed = seed; |
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this.gamma = gamma; |
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} |
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|
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/** |
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* Computes Stafford variant 13 of 64bit mix function. |
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*/ |
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private static long mix64(long z) { |
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z = (z ^ (z >>> 30)) * 0xbf58476d1ce4e5b9L; |
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z = (z ^ (z >>> 27)) * 0x94d049bb133111ebL; |
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return z ^ (z >>> 31); |
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} |
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|
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/** |
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* Returns the 32 high bits of Stafford variant 4 mix64 function as int. |
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*/ |
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private static int mix32(long z) { |
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z = (z ^ (z >>> 33)) * 0x62a9d9ed799705f5L; |
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return (int)(((z ^ (z >>> 28)) * 0xcb24d0a5c88c35b3L) >>> 32); |
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} |
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|
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/** |
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* Returns the gamma value to use for a new split instance. |
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*/ |
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private static long mixGamma(long z) { |
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z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL; // MurmurHash3 mix constants |
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z = (z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L; |
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z = (z ^ (z >>> 33)) | 1L; // force to be odd |
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int n = Long.bitCount(z ^ (z >>> 1)); // ensure enough transitions |
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return (n < 24) ? z ^ 0xaaaaaaaaaaaaaaaaL : z; |
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} |
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|
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/** |
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* Adds gamma to seed. |
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*/ |
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private long nextSeed() { |
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return seed += gamma; |
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} |
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|
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/** |
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* The seed generator for default constructors. |
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*/ |
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private static final AtomicLong defaultGen = new AtomicLong(initialSeed()); |
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|
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private static long initialSeed() { |
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java.security.PrivilegedAction<Boolean> action = |
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() -> Boolean.getBoolean("java.util.secureRandomSeed"); |
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if (java.security.AccessController.doPrivileged(action)) { |
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byte[] seedBytes = java.security.SecureRandom.getSeed(8); |
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long s = (long)seedBytes[0] & 0xffL; |
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for (int i = 1; i < 8; ++i) |
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s = (s << 8) | ((long)seedBytes[i] & 0xffL); |
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return s; |
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} |
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return (mix64(System.currentTimeMillis()) ^ |
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mix64(System.nanoTime())); |
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} |
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|
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// IllegalArgumentException messages |
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static final String BAD_BOUND = "bound must be positive"; |
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static final String BAD_RANGE = "bound must be greater than origin"; |
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static final String BAD_SIZE = "size must be non-negative"; |
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|
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/* |
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* Internal versions of nextX methods used by streams, as well as |
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* the public nextX(origin, bound) methods. These exist mainly to |
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* avoid the need for multiple versions of stream spliterators |
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* across the different exported forms of streams. |
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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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/* |
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* Four Cases: |
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* |
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* 1. If the arguments indicate unbounded form, act as |
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* nextLong(). |
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* |
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* 2. If the range is an exact power of two, apply the |
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* associated bit mask. |
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* |
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* 3. If the range is positive, loop to avoid potential bias |
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* when the implicit nextLong() bound (2<sup>64</sup>) is not |
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* evenly divisible by the range. The loop rejects candidates |
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* computed from otherwise over-represented values. The |
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* expected number of iterations under an ideal generator |
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* varies from 1 to 2, depending on the bound. The loop itself |
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* takes an unlovable form. Because the first candidate is |
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* already available, we need a break-in-the-middle |
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* construction, which is concisely but cryptically performed |
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* within the while-condition of a body-less for loop. |
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* |
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* 4. Otherwise, the range cannot be represented as a positive |
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* long. The loop repeatedly generates unbounded longs until |
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* obtaining a candidate meeting constraints (with an expected |
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* number of iterations of less than two). |
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*/ |
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|
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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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/* ---------------- public methods ---------------- */ |
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|
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/** |
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* Creates a new SplittableRandom instance using the specified |
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* initial seed. SplittableRandom instances created with the same |
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* seed in the same program generate identical sequences of values. |
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* |
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* @param seed the initial seed |
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*/ |
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public SplittableRandom(long seed) { |
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this(seed, GOLDEN_GAMMA); |
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} |
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|
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/** |
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* Creates a new SplittableRandom instance that is likely to |
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* generate sequences of values that are statistically independent |
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* of those of any other instances in the current program; and |
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* may, and typically does, vary across program invocations. |
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*/ |
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public SplittableRandom() { // emulate defaultGen.split() |
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long s = defaultGen.getAndAdd(2 * GOLDEN_GAMMA); |
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this.seed = mix64(s); |
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this.gamma = mixGamma(s + GOLDEN_GAMMA); |
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} |
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|
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/** |
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* Constructs and returns a new SplittableRandom instance that |
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* shares no mutable state with this instance. However, with very |
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* high probability, the set of values collectively generated by |
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* the two objects has the same statistical properties as if the |
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* same quantity of values were generated by a single thread using |
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* a single SplittableRandom object. Either or both of the two |
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* objects may be further split using the {@code split()} method, |
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* and the same expected statistical properties apply to the |
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* entire set of generators constructed by such recursive |
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* splitting. |
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* |
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* @return the new SplittableRandom instance |
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*/ |
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public SplittableRandom split() { |
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return new SplittableRandom(nextLong(), mixGamma(nextSeed())); |
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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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// Specialize internalNextInt for origin 0 |
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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) |
461 |
* and the specified bound (exclusive). |
462 |
* |
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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 |
467 |
*/ |
468 |
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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// Specialize internalNextLong for origin 0 |
472 |
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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/** |
486 |
* Returns a pseudorandom {@code long} value between the specified |
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* origin (inclusive) and the specified bound (exclusive). |
488 |
* |
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* @param origin the least value returned |
490 |
* @param bound the upper bound (exclusive) |
491 |
* @return a pseudorandom {@code long} value between the origin |
492 |
* (inclusive) and the bound (exclusive) |
493 |
* @throws IllegalArgumentException if {@code origin} is greater than |
494 |
* or equal to {@code bound} |
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*/ |
496 |
public long nextLong(long origin, long bound) { |
497 |
if (origin >= bound) |
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throw new IllegalArgumentException(BAD_RANGE); |
499 |
return internalNextLong(origin, bound); |
500 |
} |
501 |
|
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/** |
503 |
* Returns a pseudorandom {@code double} value between zero |
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* (inclusive) and one (exclusive). |
505 |
* |
506 |
* @return a pseudorandom {@code double} value between zero |
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* (inclusive) and one (exclusive) |
508 |
*/ |
509 |
public double nextDouble() { |
510 |
return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT; |
511 |
} |
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|
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/** |
514 |
* Returns a pseudorandom {@code double} value between 0.0 |
515 |
* (inclusive) and the specified bound (exclusive). |
516 |
* |
517 |
* @param bound the upper bound (exclusive). Must be positive. |
518 |
* @return a pseudorandom {@code double} value between zero |
519 |
* (inclusive) and the bound (exclusive) |
520 |
* @throws IllegalArgumentException if {@code bound} is not positive |
521 |
*/ |
522 |
public double nextDouble(double bound) { |
523 |
if (!(bound > 0.0)) |
524 |
throw new IllegalArgumentException(BAD_BOUND); |
525 |
double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound; |
526 |
return (result < bound) ? result : // correct for rounding |
527 |
Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1); |
528 |
} |
529 |
|
530 |
/** |
531 |
* Returns a pseudorandom {@code double} value between the specified |
532 |
* origin (inclusive) and bound (exclusive). |
533 |
* |
534 |
* @param origin the least value returned |
535 |
* @param bound the upper bound (exclusive) |
536 |
* @return a pseudorandom {@code double} value between the origin |
537 |
* (inclusive) and the bound (exclusive) |
538 |
* @throws IllegalArgumentException if {@code origin} is greater than |
539 |
* or equal to {@code bound} |
540 |
*/ |
541 |
public double nextDouble(double origin, double bound) { |
542 |
if (!(origin < bound)) |
543 |
throw new IllegalArgumentException(BAD_RANGE); |
544 |
return internalNextDouble(origin, bound); |
545 |
} |
546 |
|
547 |
/** |
548 |
* Returns a pseudorandom {@code boolean} value. |
549 |
* |
550 |
* @return a pseudorandom {@code boolean} value |
551 |
*/ |
552 |
public boolean nextBoolean() { |
553 |
return mix32(nextSeed()) < 0; |
554 |
} |
555 |
|
556 |
// stream methods, coded in a way intended to better isolate for |
557 |
// maintenance purposes the small differences across forms. |
558 |
|
559 |
/** |
560 |
* Returns a stream producing the given {@code streamSize} number |
561 |
* of pseudorandom {@code int} values from this generator and/or |
562 |
* one split from it. |
563 |
* |
564 |
* @param streamSize the number of values to generate |
565 |
* @return a stream of pseudorandom {@code int} values |
566 |
* @throws IllegalArgumentException if {@code streamSize} is |
567 |
* less than zero |
568 |
*/ |
569 |
public IntStream ints(long streamSize) { |
570 |
if (streamSize < 0L) |
571 |
throw new IllegalArgumentException(BAD_SIZE); |
572 |
return StreamSupport.intStream |
573 |
(new RandomIntsSpliterator |
574 |
(this, 0L, streamSize, Integer.MAX_VALUE, 0), |
575 |
false); |
576 |
} |
577 |
|
578 |
/** |
579 |
* Returns an effectively unlimited stream of pseudorandom {@code int} |
580 |
* values from this generator and/or one split from it. |
581 |
* |
582 |
* @implNote This method is implemented to be equivalent to {@code |
583 |
* ints(Long.MAX_VALUE)}. |
584 |
* |
585 |
* @return a stream of pseudorandom {@code int} values |
586 |
*/ |
587 |
public IntStream ints() { |
588 |
return StreamSupport.intStream |
589 |
(new RandomIntsSpliterator |
590 |
(this, 0L, Long.MAX_VALUE, Integer.MAX_VALUE, 0), |
591 |
false); |
592 |
} |
593 |
|
594 |
/** |
595 |
* Returns a stream producing the given {@code streamSize} number |
596 |
* of pseudorandom {@code int} values from this generator and/or one split |
597 |
* from it; each value conforms to the given origin (inclusive) and bound |
598 |
* (exclusive). |
599 |
* |
600 |
* @param streamSize the number of values to generate |
601 |
* @param randomNumberOrigin the origin (inclusive) of each random value |
602 |
* @param randomNumberBound the bound (exclusive) of each random value |
603 |
* @return a stream of pseudorandom {@code int} values, |
604 |
* each with the given origin (inclusive) and bound (exclusive) |
605 |
* @throws IllegalArgumentException if {@code streamSize} is |
606 |
* less than zero, or {@code randomNumberOrigin} |
607 |
* is greater than or equal to {@code randomNumberBound} |
608 |
*/ |
609 |
public IntStream ints(long streamSize, int randomNumberOrigin, |
610 |
int randomNumberBound) { |
611 |
if (streamSize < 0L) |
612 |
throw new IllegalArgumentException(BAD_SIZE); |
613 |
if (randomNumberOrigin >= randomNumberBound) |
614 |
throw new IllegalArgumentException(BAD_RANGE); |
615 |
return StreamSupport.intStream |
616 |
(new RandomIntsSpliterator |
617 |
(this, 0L, streamSize, randomNumberOrigin, randomNumberBound), |
618 |
false); |
619 |
} |
620 |
|
621 |
/** |
622 |
* Returns an effectively unlimited stream of pseudorandom {@code |
623 |
* int} values from this generator and/or one split from it; each value |
624 |
* conforms to the given origin (inclusive) and bound (exclusive). |
625 |
* |
626 |
* @implNote This method is implemented to be equivalent to {@code |
627 |
* ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. |
628 |
* |
629 |
* @param randomNumberOrigin the origin (inclusive) of each random value |
630 |
* @param randomNumberBound the bound (exclusive) of each random value |
631 |
* @return a stream of pseudorandom {@code int} values, |
632 |
* each with the given origin (inclusive) and bound (exclusive) |
633 |
* @throws IllegalArgumentException if {@code randomNumberOrigin} |
634 |
* is greater than or equal to {@code randomNumberBound} |
635 |
*/ |
636 |
public IntStream ints(int randomNumberOrigin, int randomNumberBound) { |
637 |
if (randomNumberOrigin >= randomNumberBound) |
638 |
throw new IllegalArgumentException(BAD_RANGE); |
639 |
return StreamSupport.intStream |
640 |
(new RandomIntsSpliterator |
641 |
(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), |
642 |
false); |
643 |
} |
644 |
|
645 |
/** |
646 |
* Returns a stream producing the given {@code streamSize} number |
647 |
* of pseudorandom {@code long} values from this generator and/or |
648 |
* one split from it. |
649 |
* |
650 |
* @param streamSize the number of values to generate |
651 |
* @return a stream of pseudorandom {@code long} values |
652 |
* @throws IllegalArgumentException if {@code streamSize} is |
653 |
* less than zero |
654 |
*/ |
655 |
public LongStream longs(long streamSize) { |
656 |
if (streamSize < 0L) |
657 |
throw new IllegalArgumentException(BAD_SIZE); |
658 |
return StreamSupport.longStream |
659 |
(new RandomLongsSpliterator |
660 |
(this, 0L, streamSize, Long.MAX_VALUE, 0L), |
661 |
false); |
662 |
} |
663 |
|
664 |
/** |
665 |
* Returns an effectively unlimited stream of pseudorandom {@code |
666 |
* long} values from this generator and/or one split from it. |
667 |
* |
668 |
* @implNote This method is implemented to be equivalent to {@code |
669 |
* longs(Long.MAX_VALUE)}. |
670 |
* |
671 |
* @return a stream of pseudorandom {@code long} values |
672 |
*/ |
673 |
public LongStream longs() { |
674 |
return StreamSupport.longStream |
675 |
(new RandomLongsSpliterator |
676 |
(this, 0L, Long.MAX_VALUE, Long.MAX_VALUE, 0L), |
677 |
false); |
678 |
} |
679 |
|
680 |
/** |
681 |
* Returns a stream producing the given {@code streamSize} number of |
682 |
* pseudorandom {@code long} values from this generator and/or one split |
683 |
* from it; each value conforms to the given origin (inclusive) and bound |
684 |
* (exclusive). |
685 |
* |
686 |
* @param streamSize the number of values to generate |
687 |
* @param randomNumberOrigin the origin (inclusive) of each random value |
688 |
* @param randomNumberBound the bound (exclusive) of each random value |
689 |
* @return a stream of pseudorandom {@code long} values, |
690 |
* each with the given origin (inclusive) and bound (exclusive) |
691 |
* @throws IllegalArgumentException if {@code streamSize} is |
692 |
* less than zero, or {@code randomNumberOrigin} |
693 |
* is greater than or equal to {@code randomNumberBound} |
694 |
*/ |
695 |
public LongStream longs(long streamSize, long randomNumberOrigin, |
696 |
long randomNumberBound) { |
697 |
if (streamSize < 0L) |
698 |
throw new IllegalArgumentException(BAD_SIZE); |
699 |
if (randomNumberOrigin >= randomNumberBound) |
700 |
throw new IllegalArgumentException(BAD_RANGE); |
701 |
return StreamSupport.longStream |
702 |
(new RandomLongsSpliterator |
703 |
(this, 0L, streamSize, randomNumberOrigin, randomNumberBound), |
704 |
false); |
705 |
} |
706 |
|
707 |
/** |
708 |
* Returns an effectively unlimited stream of pseudorandom {@code |
709 |
* long} values from this generator and/or one split from it; each value |
710 |
* conforms to the given origin (inclusive) and bound (exclusive). |
711 |
* |
712 |
* @implNote This method is implemented to be equivalent to {@code |
713 |
* longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. |
714 |
* |
715 |
* @param randomNumberOrigin the origin (inclusive) of each random value |
716 |
* @param randomNumberBound the bound (exclusive) of each random value |
717 |
* @return a stream of pseudorandom {@code long} values, |
718 |
* each with the given origin (inclusive) and bound (exclusive) |
719 |
* @throws IllegalArgumentException if {@code randomNumberOrigin} |
720 |
* is greater than or equal to {@code randomNumberBound} |
721 |
*/ |
722 |
public LongStream longs(long randomNumberOrigin, long randomNumberBound) { |
723 |
if (randomNumberOrigin >= randomNumberBound) |
724 |
throw new IllegalArgumentException(BAD_RANGE); |
725 |
return StreamSupport.longStream |
726 |
(new RandomLongsSpliterator |
727 |
(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), |
728 |
false); |
729 |
} |
730 |
|
731 |
/** |
732 |
* Returns a stream producing the given {@code streamSize} number of |
733 |
* pseudorandom {@code double} values from this generator and/or one split |
734 |
* from it; each value is between zero (inclusive) and one (exclusive). |
735 |
* |
736 |
* @param streamSize the number of values to generate |
737 |
* @return a stream of {@code double} values |
738 |
* @throws IllegalArgumentException if {@code streamSize} is |
739 |
* less than zero |
740 |
*/ |
741 |
public DoubleStream doubles(long streamSize) { |
742 |
if (streamSize < 0L) |
743 |
throw new IllegalArgumentException(BAD_SIZE); |
744 |
return StreamSupport.doubleStream |
745 |
(new RandomDoublesSpliterator |
746 |
(this, 0L, streamSize, Double.MAX_VALUE, 0.0), |
747 |
false); |
748 |
} |
749 |
|
750 |
/** |
751 |
* Returns an effectively unlimited stream of pseudorandom {@code |
752 |
* double} values from this generator and/or one split from it; each value |
753 |
* is between zero (inclusive) and one (exclusive). |
754 |
* |
755 |
* @implNote This method is implemented to be equivalent to {@code |
756 |
* doubles(Long.MAX_VALUE)}. |
757 |
* |
758 |
* @return a stream of pseudorandom {@code double} values |
759 |
*/ |
760 |
public DoubleStream doubles() { |
761 |
return StreamSupport.doubleStream |
762 |
(new RandomDoublesSpliterator |
763 |
(this, 0L, Long.MAX_VALUE, Double.MAX_VALUE, 0.0), |
764 |
false); |
765 |
} |
766 |
|
767 |
/** |
768 |
* Returns a stream producing the given {@code streamSize} number of |
769 |
* pseudorandom {@code double} values from this generator and/or one split |
770 |
* from it; each value conforms to the given origin (inclusive) and bound |
771 |
* (exclusive). |
772 |
* |
773 |
* @param streamSize the number of values to generate |
774 |
* @param randomNumberOrigin the origin (inclusive) of each random value |
775 |
* @param randomNumberBound the bound (exclusive) of each random value |
776 |
* @return a stream of pseudorandom {@code double} values, |
777 |
* each with the given origin (inclusive) and bound (exclusive) |
778 |
* @throws IllegalArgumentException if {@code streamSize} is |
779 |
* less than zero |
780 |
* @throws IllegalArgumentException if {@code randomNumberOrigin} |
781 |
* is greater than or equal to {@code randomNumberBound} |
782 |
*/ |
783 |
public DoubleStream doubles(long streamSize, double randomNumberOrigin, |
784 |
double randomNumberBound) { |
785 |
if (streamSize < 0L) |
786 |
throw new IllegalArgumentException(BAD_SIZE); |
787 |
if (!(randomNumberOrigin < randomNumberBound)) |
788 |
throw new IllegalArgumentException(BAD_RANGE); |
789 |
return StreamSupport.doubleStream |
790 |
(new RandomDoublesSpliterator |
791 |
(this, 0L, streamSize, randomNumberOrigin, randomNumberBound), |
792 |
false); |
793 |
} |
794 |
|
795 |
/** |
796 |
* Returns an effectively unlimited stream of pseudorandom {@code |
797 |
* double} values from this generator and/or one split from it; each value |
798 |
* conforms to the given origin (inclusive) and bound (exclusive). |
799 |
* |
800 |
* @implNote This method is implemented to be equivalent to {@code |
801 |
* doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. |
802 |
* |
803 |
* @param randomNumberOrigin the origin (inclusive) of each random value |
804 |
* @param randomNumberBound the bound (exclusive) of each random value |
805 |
* @return a stream of pseudorandom {@code double} values, |
806 |
* each with the given origin (inclusive) and bound (exclusive) |
807 |
* @throws IllegalArgumentException if {@code randomNumberOrigin} |
808 |
* is greater than or equal to {@code randomNumberBound} |
809 |
*/ |
810 |
public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) { |
811 |
if (!(randomNumberOrigin < randomNumberBound)) |
812 |
throw new IllegalArgumentException(BAD_RANGE); |
813 |
return StreamSupport.doubleStream |
814 |
(new RandomDoublesSpliterator |
815 |
(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), |
816 |
false); |
817 |
} |
818 |
|
819 |
/** |
820 |
* Spliterator for int streams. We multiplex the four int |
821 |
* versions into one class by treating a bound less than origin as |
822 |
* unbounded, and also by treating "infinite" as equivalent to |
823 |
* Long.MAX_VALUE. For splits, it uses the standard divide-by-two |
824 |
* approach. The long and double versions of this class are |
825 |
* identical except for types. |
826 |
*/ |
827 |
private static final class RandomIntsSpliterator |
828 |
implements Spliterator.OfInt { |
829 |
final SplittableRandom rng; |
830 |
long index; |
831 |
final long fence; |
832 |
final int origin; |
833 |
final int bound; |
834 |
RandomIntsSpliterator(SplittableRandom rng, long index, long fence, |
835 |
int origin, int bound) { |
836 |
this.rng = rng; this.index = index; this.fence = fence; |
837 |
this.origin = origin; this.bound = bound; |
838 |
} |
839 |
|
840 |
public RandomIntsSpliterator trySplit() { |
841 |
long i = index, m = (i + fence) >>> 1; |
842 |
return (m <= i) ? null : |
843 |
new RandomIntsSpliterator(rng.split(), i, index = m, origin, bound); |
844 |
} |
845 |
|
846 |
public long estimateSize() { |
847 |
return fence - index; |
848 |
} |
849 |
|
850 |
public int characteristics() { |
851 |
return (Spliterator.SIZED | Spliterator.SUBSIZED | |
852 |
Spliterator.NONNULL | Spliterator.IMMUTABLE); |
853 |
} |
854 |
|
855 |
public boolean tryAdvance(IntConsumer consumer) { |
856 |
if (consumer == null) throw new NullPointerException(); |
857 |
long i = index, f = fence; |
858 |
if (i < f) { |
859 |
consumer.accept(rng.internalNextInt(origin, bound)); |
860 |
index = i + 1; |
861 |
return true; |
862 |
} |
863 |
return false; |
864 |
} |
865 |
|
866 |
public void forEachRemaining(IntConsumer consumer) { |
867 |
if (consumer == null) throw new NullPointerException(); |
868 |
long i = index, f = fence; |
869 |
if (i < f) { |
870 |
index = f; |
871 |
SplittableRandom r = rng; |
872 |
int o = origin, b = bound; |
873 |
do { |
874 |
consumer.accept(r.internalNextInt(o, b)); |
875 |
} while (++i < f); |
876 |
} |
877 |
} |
878 |
} |
879 |
|
880 |
/** |
881 |
* Spliterator for long streams. |
882 |
*/ |
883 |
private static final class RandomLongsSpliterator |
884 |
implements Spliterator.OfLong { |
885 |
final SplittableRandom rng; |
886 |
long index; |
887 |
final long fence; |
888 |
final long origin; |
889 |
final long bound; |
890 |
RandomLongsSpliterator(SplittableRandom rng, long index, long fence, |
891 |
long origin, long bound) { |
892 |
this.rng = rng; this.index = index; this.fence = fence; |
893 |
this.origin = origin; this.bound = bound; |
894 |
} |
895 |
|
896 |
public RandomLongsSpliterator trySplit() { |
897 |
long i = index, m = (i + fence) >>> 1; |
898 |
return (m <= i) ? null : |
899 |
new RandomLongsSpliterator(rng.split(), i, index = m, origin, bound); |
900 |
} |
901 |
|
902 |
public long estimateSize() { |
903 |
return fence - index; |
904 |
} |
905 |
|
906 |
public int characteristics() { |
907 |
return (Spliterator.SIZED | Spliterator.SUBSIZED | |
908 |
Spliterator.NONNULL | Spliterator.IMMUTABLE); |
909 |
} |
910 |
|
911 |
public boolean tryAdvance(LongConsumer consumer) { |
912 |
if (consumer == null) throw new NullPointerException(); |
913 |
long i = index, f = fence; |
914 |
if (i < f) { |
915 |
consumer.accept(rng.internalNextLong(origin, bound)); |
916 |
index = i + 1; |
917 |
return true; |
918 |
} |
919 |
return false; |
920 |
} |
921 |
|
922 |
public void forEachRemaining(LongConsumer consumer) { |
923 |
if (consumer == null) throw new NullPointerException(); |
924 |
long i = index, f = fence; |
925 |
if (i < f) { |
926 |
index = f; |
927 |
SplittableRandom r = rng; |
928 |
long o = origin, b = bound; |
929 |
do { |
930 |
consumer.accept(r.internalNextLong(o, b)); |
931 |
} while (++i < f); |
932 |
} |
933 |
} |
934 |
|
935 |
} |
936 |
|
937 |
/** |
938 |
* Spliterator for double streams. |
939 |
*/ |
940 |
private static final class RandomDoublesSpliterator |
941 |
implements Spliterator.OfDouble { |
942 |
final SplittableRandom rng; |
943 |
long index; |
944 |
final long fence; |
945 |
final double origin; |
946 |
final double bound; |
947 |
RandomDoublesSpliterator(SplittableRandom rng, long index, long fence, |
948 |
double origin, double bound) { |
949 |
this.rng = rng; this.index = index; this.fence = fence; |
950 |
this.origin = origin; this.bound = bound; |
951 |
} |
952 |
|
953 |
public RandomDoublesSpliterator trySplit() { |
954 |
long i = index, m = (i + fence) >>> 1; |
955 |
return (m <= i) ? null : |
956 |
new RandomDoublesSpliterator(rng.split(), i, index = m, origin, bound); |
957 |
} |
958 |
|
959 |
public long estimateSize() { |
960 |
return fence - index; |
961 |
} |
962 |
|
963 |
public int characteristics() { |
964 |
return (Spliterator.SIZED | Spliterator.SUBSIZED | |
965 |
Spliterator.NONNULL | Spliterator.IMMUTABLE); |
966 |
} |
967 |
|
968 |
public boolean tryAdvance(DoubleConsumer consumer) { |
969 |
if (consumer == null) throw new NullPointerException(); |
970 |
long i = index, f = fence; |
971 |
if (i < f) { |
972 |
consumer.accept(rng.internalNextDouble(origin, bound)); |
973 |
index = i + 1; |
974 |
return true; |
975 |
} |
976 |
return false; |
977 |
} |
978 |
|
979 |
public void forEachRemaining(DoubleConsumer consumer) { |
980 |
if (consumer == null) throw new NullPointerException(); |
981 |
long i = index, f = fence; |
982 |
if (i < f) { |
983 |
index = f; |
984 |
SplittableRandom r = rng; |
985 |
double o = origin, b = bound; |
986 |
do { |
987 |
consumer.accept(r.internalNextDouble(o, b)); |
988 |
} while (++i < f); |
989 |
} |
990 |
} |
991 |
} |
992 |
|
993 |
} |