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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.Spliterator; |
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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.function.DoubleConsumer; |
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import java.util.stream.StreamSupport; |
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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.DoubleStream; |
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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 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>. </li> |
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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. </li> |
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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.</li> |
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* |
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* </ul> |
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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 class SplittableRandom { |
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|
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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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* Credits: Primary algorithm and code by Guy Steele. Stream |
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* support methods by Doug Lea. Documentation jointly produced |
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* with additional help from Brian Goetz. |
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*/ |
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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, but improves and extends it in several ways. |
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* |
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* The primary update step (see method nextSeed()) is simply to |
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* add a constant ("gamma") to the current seed, modulo a prime |
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* ("George"). However, the nextLong and nextInt methods do not |
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* return this value, but instead the results of bit-mixing |
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* transformations that produce more uniformly distributed |
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* sequences. |
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* |
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* "George" is the otherwise nameless (because it cannot be |
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* represented) prime number 2^64+13. Using a prime number larger |
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* than can fit in a long ensures that all possible long values |
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* can occur, plus 13 others that just get skipped over when they |
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* are encountered; see method addGammaModGeorge. For this to |
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* work, initial gamma values must be at least 13. |
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* |
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* The value of gamma differs for each instance across a series of |
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* splits, and is generated using a slightly stripped-down variant |
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* of the same algorithm, but operating across calls to split(), |
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* not calls to nextSeed(): Each instance carries the state of |
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* this generator as nextSplit, and uses mix64(nextSplit) as its |
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* own gamma value. Computations of gammas themselves use a fixed |
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* constant as the second argument to the addGammaModGeorge |
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* function, GAMMA_GAMMA, a "genuinely random" number from a |
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* radioactive decay reading (obtained from |
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* http://www.fourmilab.ch/hotbits/) meeting the above range |
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* constraint. Using a fixed constant maintains the invariant that |
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* the value of gamma is the same for every instance that is at |
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* the same split-distance from their common root. (Note: there is |
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* nothing especially magic about obtaining this constant from a |
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* "truly random" physical source rather than just choosing one |
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* arbitrarily; using "hotbits" was merely an aesthetically pleasing |
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* choice. In either case, good statistical behavior of the |
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* algorithm should be, and was, verified by using the DieHarder |
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* test suite.) |
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* |
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* The mix64 bit-mixing function called by nextLong and other |
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* methods computes the same value as the "64-bit finalizer" |
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* function in Austin Appleby's MurmurHash3 algorithm. See |
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* http://code.google.com/p/smhasher/wiki/MurmurHash3 , which |
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* comments: "The constants for the finalizers were generated by a |
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* simple simulated-annealing algorithm, and both avalanche all |
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* bits of 'h' to within 0.25% bias." It also appears to work to |
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* use instead any of the variants proposed by David Stafford at |
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* http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html |
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* but these variants have not yet been tested as thoroughly |
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* in the context of the implementation of SplittableRandom. |
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* |
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* The mix32 function used for nextInt just consists of two of the |
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* five lines of mix64; avalanche testing shows that the 64-bit result |
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* has its top 32 bits avalanched well, though not the bottom 32 bits. |
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* DieHarder tests show that it is adequate for generating one |
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* random int from the 64-bit result of nextSeed. |
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* |
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* Support for the default (no-argument) constructor relies on an |
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* AtomicLong (defaultSeedGenerator) to help perform the |
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* equivalent of a split of a statically constructed |
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* SplittableRandom. Unlike other cases, this split must be |
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* performed in a thread-safe manner. We use |
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* AtomicLong.compareAndSet as the (typically) most efficient |
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* mechanism. To bootstrap, we start off using a function of the |
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* current System time as seed, and update using another |
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* "genuinely random" constant DEFAULT_SEED_GAMMA. The default |
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* constructor uses GAMMA_GAMMA, not 0, for its splitSeed argument |
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* (addGammaModGeorge(0, GAMMA_GAMMA) == GAMMA_GAMMA) to reflect |
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* that each is split from this root generator, even though the |
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* root is not explicitly represented as a SplittableRandom. When |
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* establishing the initial seed, we use both |
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* System.currentTimeMillis and System.nanoTime(), to avoid |
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* regularities that may occur if using either alone. |
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*/ |
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|
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/** |
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* The "genuinely random" value for producing new gamma values. |
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* The value is arbitrary, subject to the requirement that it be |
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* greater or equal to 13. |
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*/ |
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private static final long GAMMA_GAMMA = 0xF2281E2DBA6606F3L; |
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|
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/** |
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* The "genuinely random" seed update value for default constructors. |
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* The value is arbitrary, subject to the requirement that it be |
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* greater or equal to 13. |
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*/ |
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private static final long DEFAULT_SEED_GAMMA = 0xBD24B73A95FB84D9L; |
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|
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/** |
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* The value 13 with 64bit sign bit set. Used in the signed |
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* comparison in addGammaModGeorge. |
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*/ |
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private static final long BOTTOM13 = 0x800000000000000DL; |
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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 = 1.0 / (1L << 53); |
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|
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/** |
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* The next seed for default constructors. |
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*/ |
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private static final AtomicLong defaultSeedGenerator = |
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new AtomicLong(mix64(System.currentTimeMillis()) ^ |
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mix64(System.nanoTime())); |
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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 constant value added to seed (mod George) on each update. |
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*/ |
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private final long gamma; |
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|
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/** |
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* The next seed to use for splits. Propagated using |
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* addGammaModGeorge across instances. |
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*/ |
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private final long nextSplit; |
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|
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/** |
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* Adds the given gamma value, g, to the given seed value s, mod |
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* George (2^64+13). We regard s and g as unsigned values |
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* (ranging from 0 to 2^64-1). We add g to s either once or twice |
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* (mod George) as necessary to produce an (unsigned) result less |
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* than 2^64. We require that g must be at least 13. This |
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* guarantees that if (s+g) mod George >= 2^64 then (s+g+g) mod |
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* George < 2^64; thus we need only a conditional, not a loop, |
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* to be sure of getting a representable value. |
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* |
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* Because Java comparison operators are signed, we implement this |
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* by conceptually offsetting seed values downwards by 2^63, so |
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* 0..13 is represented as Long.MIN_VALUE..BOTTOM13. |
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* |
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* @param s a seed value, viewed as a signed long |
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* @param g a gamma value, 13 <= g (as unsigned) |
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*/ |
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private static long addGammaModGeorge(long s, long g) { |
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long p = s + g; |
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return (p >= s) ? p : ((p >= BOTTOM13) ? p : p + g) - 13L; |
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} |
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|
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/** |
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* Returns a bit-mixed transformation of its argument. |
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* See above for explanation. |
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*/ |
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private static long mix64(long z) { |
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z ^= (z >>> 33); |
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z *= 0xff51afd7ed558ccdL; |
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z ^= (z >>> 33); |
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z *= 0xc4ceb9fe1a85ec53L; |
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z ^= (z >>> 33); |
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return z; |
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} |
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|
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/** |
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* Returns a bit-mixed int transformation of its argument. |
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* See above for explanation. |
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*/ |
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private static int mix32(long z) { |
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z ^= (z >>> 33); |
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z *= 0xc4ceb9fe1a85ec53L; |
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return (int)(z >>> 32); |
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} |
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|
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/** |
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* Internal constructor used by all other constructors and by |
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* method split. Establishes the initial seed for this instance, |
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* and uses the given splitSeed to establish gamma, as well as the |
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* nextSplit to use by this instance. The loop to skip ineligible |
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* gammas very rarely iterates, and does so at most 13 times. |
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*/ |
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private SplittableRandom(long seed, long splitSeed) { |
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this.seed = seed; |
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long s = splitSeed, g; |
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do { // ensure gamma >= 13, considered as an unsigned integer |
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s = addGammaModGeorge(s, GAMMA_GAMMA); |
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g = mix64(s); |
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} while (g >= 0L && g < 13L); |
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this.gamma = g; |
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this.nextSplit = s; |
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} |
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|
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/** |
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* Updates in-place and returns seed. |
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* See above for explanation. |
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*/ |
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private long nextSeed() { |
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return seed = addGammaModGeorge(seed, gamma); |
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} |
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|
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/** |
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* Atomically updates and returns next seed for default constructor. |
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*/ |
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private static long nextDefaultSeed() { |
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long oldSeed, newSeed; |
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do { |
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oldSeed = defaultSeedGenerator.get(); |
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newSeed = addGammaModGeorge(oldSeed, DEFAULT_SEED_GAMMA); |
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} while (!defaultSeedGenerator.compareAndSet(oldSeed, newSeed)); |
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return mix64(newSeed); |
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} |
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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) == 0L) |
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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, 0); |
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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. |
432 |
*/ |
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public SplittableRandom() { |
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this(nextDefaultSeed(), GAMMA_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. |
448 |
* |
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* @return the new SplittableRandom instance |
450 |
*/ |
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public SplittableRandom split() { |
452 |
return new SplittableRandom(nextSeed(), nextSplit); |
453 |
} |
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|
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/** |
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* Returns a pseudorandom {@code int} value. |
457 |
* |
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* @return a pseudorandom {@code int} value |
459 |
*/ |
460 |
public int nextInt() { |
461 |
return mix32(nextSeed()); |
462 |
} |
463 |
|
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/** |
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* Returns a pseudorandom {@code int} value between zero (inclusive) |
466 |
* and the specified bound (exclusive). |
467 |
* |
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* @param bound the bound on the random number to be returned. Must be |
469 |
* positive. |
470 |
* @return a pseudorandom {@code int} value between zero |
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* (inclusive) and the bound (exclusive) |
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* @throws IllegalArgumentException if the bound is less than zero |
473 |
*/ |
474 |
public int nextInt(int bound) { |
475 |
if (bound <= 0) |
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throw new IllegalArgumentException("bound must be positive"); |
477 |
// Specialize internalNextInt for origin 0 |
478 |
int r = mix32(nextSeed()); |
479 |
int m = bound - 1; |
480 |
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 (int u = r >>> 1; |
484 |
u + m - (r = u % bound) < 0; |
485 |
u = mix32(nextSeed()) >>> 1) |
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; |
487 |
} |
488 |
return r; |
489 |
} |
490 |
|
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/** |
492 |
* Returns a pseudorandom {@code int} value between the specified |
493 |
* origin (inclusive) and the specified bound (exclusive). |
494 |
* |
495 |
* @param origin the least value returned |
496 |
* @param bound the upper bound (exclusive) |
497 |
* @return a pseudorandom {@code int} value between the origin |
498 |
* (inclusive) and the bound (exclusive) |
499 |
* @throws IllegalArgumentException if {@code origin} is greater than |
500 |
* or equal to {@code bound} |
501 |
*/ |
502 |
public int nextInt(int origin, int bound) { |
503 |
if (origin >= bound) |
504 |
throw new IllegalArgumentException("bound must be greater than origin"); |
505 |
return internalNextInt(origin, bound); |
506 |
} |
507 |
|
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/** |
509 |
* Returns a pseudorandom {@code long} value. |
510 |
* |
511 |
* @return a pseudorandom {@code long} value |
512 |
*/ |
513 |
public long nextLong() { |
514 |
return mix64(nextSeed()); |
515 |
} |
516 |
|
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/** |
518 |
* Returns a pseudorandom {@code long} value between zero (inclusive) |
519 |
* and the specified bound (exclusive). |
520 |
* |
521 |
* @param bound the bound on the random number to be returned. Must be |
522 |
* positive. |
523 |
* @return a pseudorandom {@code long} value between zero |
524 |
* (inclusive) and the bound (exclusive) |
525 |
* @throws IllegalArgumentException if {@code bound} is less than zero |
526 |
*/ |
527 |
public long nextLong(long bound) { |
528 |
if (bound <= 0) |
529 |
throw new IllegalArgumentException("bound must be positive"); |
530 |
// Specialize internalNextLong for origin 0 |
531 |
long r = mix64(nextSeed()); |
532 |
long m = bound - 1; |
533 |
if ((bound & m) == 0L) // power of two |
534 |
r &= m; |
535 |
else { // reject over-represented candidates |
536 |
for (long u = r >>> 1; |
537 |
u + m - (r = u % bound) < 0L; |
538 |
u = mix64(nextSeed()) >>> 1) |
539 |
; |
540 |
} |
541 |
return r; |
542 |
} |
543 |
|
544 |
/** |
545 |
* Returns a pseudorandom {@code long} value between the specified |
546 |
* origin (inclusive) and the specified bound (exclusive). |
547 |
* |
548 |
* @param origin the least value returned |
549 |
* @param bound the upper bound (exclusive) |
550 |
* @return a pseudorandom {@code long} value between the origin |
551 |
* (inclusive) and the bound (exclusive) |
552 |
* @throws IllegalArgumentException if {@code origin} is greater than |
553 |
* or equal to {@code bound} |
554 |
*/ |
555 |
public long nextLong(long origin, long bound) { |
556 |
if (origin >= bound) |
557 |
throw new IllegalArgumentException("bound must be greater than origin"); |
558 |
return internalNextLong(origin, bound); |
559 |
} |
560 |
|
561 |
/** |
562 |
* Returns a pseudorandom {@code double} value between zero |
563 |
* (inclusive) and one (exclusive). |
564 |
* |
565 |
* @return a pseudorandom {@code double} value between zero |
566 |
* (inclusive) and one (exclusive) |
567 |
*/ |
568 |
public double nextDouble() { |
569 |
return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT; |
570 |
} |
571 |
|
572 |
/** |
573 |
* Returns a pseudorandom {@code double} value between 0.0 |
574 |
* (inclusive) and the specified bound (exclusive). |
575 |
* |
576 |
* @param bound the bound on the random number to be returned. Must be |
577 |
* positive. |
578 |
* @return a pseudorandom {@code double} value between zero |
579 |
* (inclusive) and the bound (exclusive) |
580 |
* @throws IllegalArgumentException if {@code bound} is less than zero |
581 |
*/ |
582 |
public double nextDouble(double bound) { |
583 |
if (!(bound > 0.0)) |
584 |
throw new IllegalArgumentException("bound must be positive"); |
585 |
double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound; |
586 |
return (result < bound) ? result : // correct for rounding |
587 |
Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1); |
588 |
} |
589 |
|
590 |
/** |
591 |
* Returns a pseudorandom {@code double} value between the specified |
592 |
* origin (inclusive) and bound (exclusive). |
593 |
* |
594 |
* @param origin the least value returned |
595 |
* @param bound the upper bound |
596 |
* @return a pseudorandom {@code double} value between the origin |
597 |
* (inclusive) and the bound (exclusive) |
598 |
* @throws IllegalArgumentException if {@code origin} is greater than |
599 |
* or equal to {@code bound} |
600 |
*/ |
601 |
public double nextDouble(double origin, double bound) { |
602 |
if (!(origin < bound)) |
603 |
throw new IllegalArgumentException("bound must be greater than origin"); |
604 |
return internalNextDouble(origin, bound); |
605 |
} |
606 |
|
607 |
/** |
608 |
* Returns a pseudorandom {@code boolean} value. |
609 |
* |
610 |
* @return a pseudorandom {@code boolean} value |
611 |
*/ |
612 |
public boolean nextBoolean() { |
613 |
return mix32(nextSeed()) < 0; |
614 |
} |
615 |
|
616 |
// stream methods, coded in a way intended to better isolate for |
617 |
// maintenance purposes the small differences across forms. |
618 |
|
619 |
/** |
620 |
* Returns a stream producing the given {@code streamSize} number of |
621 |
* pseudorandom {@code int} values. |
622 |
* |
623 |
* @param streamSize the number of values to generate |
624 |
* @return a stream of pseudorandom {@code int} values |
625 |
* @throws IllegalArgumentException if {@code streamSize} is |
626 |
* less than zero |
627 |
*/ |
628 |
public IntStream ints(long streamSize) { |
629 |
if (streamSize < 0L) |
630 |
throw new IllegalArgumentException("negative Stream size"); |
631 |
return StreamSupport.intStream |
632 |
(new RandomIntsSpliterator |
633 |
(this, 0L, streamSize, Integer.MAX_VALUE, 0), |
634 |
false); |
635 |
} |
636 |
|
637 |
/** |
638 |
* Returns an effectively unlimited stream of pseudorandom {@code int} |
639 |
* values. |
640 |
* |
641 |
* @implNote This method is implemented to be equivalent to {@code |
642 |
* ints(Long.MAX_VALUE)}. |
643 |
* |
644 |
* @return a stream of pseudorandom {@code int} values |
645 |
*/ |
646 |
public IntStream ints() { |
647 |
return StreamSupport.intStream |
648 |
(new RandomIntsSpliterator |
649 |
(this, 0L, Long.MAX_VALUE, Integer.MAX_VALUE, 0), |
650 |
false); |
651 |
} |
652 |
|
653 |
/** |
654 |
* Returns a stream producing the given {@code streamSize} number of |
655 |
* pseudorandom {@code int} values, each conforming to the given |
656 |
* origin and bound. |
657 |
* |
658 |
* @param streamSize the number of values to generate |
659 |
* @param randomNumberOrigin the origin of each random value |
660 |
* @param randomNumberBound the bound of each random value |
661 |
* @return a stream of pseudorandom {@code int} values, |
662 |
* each with the given origin and bound |
663 |
* @throws IllegalArgumentException if {@code streamSize} is |
664 |
* less than zero, or {@code randomNumberOrigin} |
665 |
* is greater than or equal to {@code randomNumberBound} |
666 |
*/ |
667 |
public IntStream ints(long streamSize, int randomNumberOrigin, |
668 |
int randomNumberBound) { |
669 |
if (streamSize < 0L) |
670 |
throw new IllegalArgumentException("negative Stream size"); |
671 |
if (randomNumberOrigin >= randomNumberBound) |
672 |
throw new IllegalArgumentException("bound must be greater than origin"); |
673 |
return StreamSupport.intStream |
674 |
(new RandomIntsSpliterator |
675 |
(this, 0L, streamSize, randomNumberOrigin, randomNumberBound), |
676 |
false); |
677 |
} |
678 |
|
679 |
/** |
680 |
* Returns an effectively unlimited stream of pseudorandom {@code |
681 |
* int} values, each conforming to the given origin and bound. |
682 |
* |
683 |
* @implNote This method is implemented to be equivalent to {@code |
684 |
* ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. |
685 |
* |
686 |
* @param randomNumberOrigin the origin of each random value |
687 |
* @param randomNumberBound the bound of each random value |
688 |
* @return a stream of pseudorandom {@code int} values, |
689 |
* each with the given origin and bound |
690 |
* @throws IllegalArgumentException if {@code randomNumberOrigin} |
691 |
* is greater than or equal to {@code randomNumberBound} |
692 |
*/ |
693 |
public IntStream ints(int randomNumberOrigin, int randomNumberBound) { |
694 |
if (randomNumberOrigin >= randomNumberBound) |
695 |
throw new IllegalArgumentException("bound must be greater than origin"); |
696 |
return StreamSupport.intStream |
697 |
(new RandomIntsSpliterator |
698 |
(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), |
699 |
false); |
700 |
} |
701 |
|
702 |
/** |
703 |
* Returns a stream producing the given {@code streamSize} number of |
704 |
* pseudorandom {@code long} values. |
705 |
* |
706 |
* @param streamSize the number of values to generate |
707 |
* @return a stream of pseudorandom {@code long} values |
708 |
* @throws IllegalArgumentException if {@code streamSize} is |
709 |
* less than zero |
710 |
*/ |
711 |
public LongStream longs(long streamSize) { |
712 |
if (streamSize < 0L) |
713 |
throw new IllegalArgumentException("negative Stream size"); |
714 |
return StreamSupport.longStream |
715 |
(new RandomLongsSpliterator |
716 |
(this, 0L, streamSize, Long.MAX_VALUE, 0L), |
717 |
false); |
718 |
} |
719 |
|
720 |
/** |
721 |
* Returns an effectively unlimited stream of pseudorandom {@code long} |
722 |
* values. |
723 |
* |
724 |
* @implNote This method is implemented to be equivalent to {@code |
725 |
* longs(Long.MAX_VALUE)}. |
726 |
* |
727 |
* @return a stream of pseudorandom {@code long} values |
728 |
*/ |
729 |
public LongStream longs() { |
730 |
return StreamSupport.longStream |
731 |
(new RandomLongsSpliterator |
732 |
(this, 0L, Long.MAX_VALUE, Long.MAX_VALUE, 0L), |
733 |
false); |
734 |
} |
735 |
|
736 |
/** |
737 |
* Returns a stream producing the given {@code streamSize} number of |
738 |
* pseudorandom {@code long} values, each conforming to the |
739 |
* given origin and bound. |
740 |
* |
741 |
* @param streamSize the number of values to generate |
742 |
* @param randomNumberOrigin the origin of each random value |
743 |
* @param randomNumberBound the bound of each random value |
744 |
* @return a stream of pseudorandom {@code long} values, |
745 |
* each with the given origin and bound |
746 |
* @throws IllegalArgumentException if {@code streamSize} is |
747 |
* less than zero, or {@code randomNumberOrigin} |
748 |
* is greater than or equal to {@code randomNumberBound} |
749 |
*/ |
750 |
public LongStream longs(long streamSize, long randomNumberOrigin, |
751 |
long randomNumberBound) { |
752 |
if (streamSize < 0L) |
753 |
throw new IllegalArgumentException("negative Stream size"); |
754 |
if (randomNumberOrigin >= randomNumberBound) |
755 |
throw new IllegalArgumentException("bound must be greater than origin"); |
756 |
return StreamSupport.longStream |
757 |
(new RandomLongsSpliterator |
758 |
(this, 0L, streamSize, randomNumberOrigin, randomNumberBound), |
759 |
false); |
760 |
} |
761 |
|
762 |
/** |
763 |
* Returns an effectively unlimited stream of pseudorandom {@code |
764 |
* long} values, each conforming to the given origin and bound. |
765 |
* |
766 |
* @implNote This method is implemented to be equivalent to {@code |
767 |
* longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. |
768 |
* |
769 |
* @param randomNumberOrigin the origin of each random value |
770 |
* @param randomNumberBound the bound of each random value |
771 |
* @return a stream of pseudorandom {@code long} values, |
772 |
* each with the given origin and bound |
773 |
* @throws IllegalArgumentException if {@code randomNumberOrigin} |
774 |
* is greater than or equal to {@code randomNumberBound} |
775 |
*/ |
776 |
public LongStream longs(long randomNumberOrigin, long randomNumberBound) { |
777 |
if (randomNumberOrigin >= randomNumberBound) |
778 |
throw new IllegalArgumentException("bound must be greater than origin"); |
779 |
return StreamSupport.longStream |
780 |
(new RandomLongsSpliterator |
781 |
(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), |
782 |
false); |
783 |
} |
784 |
|
785 |
/** |
786 |
* Returns a stream producing the given {@code streamSize} number of |
787 |
* pseudorandom {@code double} values, each between zero |
788 |
* (inclusive) and one (exclusive). |
789 |
* |
790 |
* @param streamSize the number of values to generate |
791 |
* @return a stream of {@code double} values |
792 |
* @throws IllegalArgumentException if {@code streamSize} is |
793 |
* less than zero |
794 |
*/ |
795 |
public DoubleStream doubles(long streamSize) { |
796 |
if (streamSize < 0L) |
797 |
throw new IllegalArgumentException("negative Stream size"); |
798 |
return StreamSupport.doubleStream |
799 |
(new RandomDoublesSpliterator |
800 |
(this, 0L, streamSize, Double.MAX_VALUE, 0.0), |
801 |
false); |
802 |
} |
803 |
|
804 |
/** |
805 |
* Returns an effectively unlimited stream of pseudorandom {@code |
806 |
* double} values, each between zero (inclusive) and one |
807 |
* (exclusive). |
808 |
* |
809 |
* @implNote This method is implemented to be equivalent to {@code |
810 |
* doubles(Long.MAX_VALUE)}. |
811 |
* |
812 |
* @return a stream of pseudorandom {@code double} values |
813 |
*/ |
814 |
public DoubleStream doubles() { |
815 |
return StreamSupport.doubleStream |
816 |
(new RandomDoublesSpliterator |
817 |
(this, 0L, Long.MAX_VALUE, Double.MAX_VALUE, 0.0), |
818 |
false); |
819 |
} |
820 |
|
821 |
/** |
822 |
* Returns a stream producing the given {@code streamSize} number of |
823 |
* pseudorandom {@code double} values, each conforming to the |
824 |
* given origin and bound. |
825 |
* |
826 |
* @param streamSize the number of values to generate |
827 |
* @param randomNumberOrigin the origin of each random value |
828 |
* @param randomNumberBound the bound of each random value |
829 |
* @return a stream of pseudorandom {@code double} values, |
830 |
* each with the given origin and bound |
831 |
* @throws IllegalArgumentException if {@code streamSize} is |
832 |
* less than zero |
833 |
* @throws IllegalArgumentException if {@code randomNumberOrigin} |
834 |
* is greater than or equal to {@code randomNumberBound} |
835 |
*/ |
836 |
public DoubleStream doubles(long streamSize, double randomNumberOrigin, |
837 |
double randomNumberBound) { |
838 |
if (streamSize < 0L) |
839 |
throw new IllegalArgumentException("negative Stream size"); |
840 |
if (!(randomNumberOrigin < randomNumberBound)) |
841 |
throw new IllegalArgumentException("bound must be greater than origin"); |
842 |
return StreamSupport.doubleStream |
843 |
(new RandomDoublesSpliterator |
844 |
(this, 0L, streamSize, randomNumberOrigin, randomNumberBound), |
845 |
false); |
846 |
} |
847 |
|
848 |
/** |
849 |
* Returns an effectively unlimited stream of pseudorandom {@code |
850 |
* double} values, each conforming to the given origin and bound. |
851 |
* |
852 |
* @implNote This method is implemented to be equivalent to {@code |
853 |
* doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. |
854 |
* |
855 |
* @param randomNumberOrigin the origin of each random value |
856 |
* @param randomNumberBound the bound of each random value |
857 |
* @return a stream of pseudorandom {@code double} values, |
858 |
* each with the given origin and bound |
859 |
* @throws IllegalArgumentException if {@code randomNumberOrigin} |
860 |
* is greater than or equal to {@code randomNumberBound} |
861 |
*/ |
862 |
public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) { |
863 |
if (!(randomNumberOrigin < randomNumberBound)) |
864 |
throw new IllegalArgumentException("bound must be greater than origin"); |
865 |
return StreamSupport.doubleStream |
866 |
(new RandomDoublesSpliterator |
867 |
(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), |
868 |
false); |
869 |
} |
870 |
|
871 |
/** |
872 |
* Spliterator for int streams. We multiplex the four int |
873 |
* versions into one class by treating a bound less than origin as |
874 |
* unbounded, and also by treating "infinite" as equivalent to |
875 |
* Long.MAX_VALUE. For splits, it uses the standard divide-by-two |
876 |
* approach. The long and double versions of this class are |
877 |
* identical except for types. |
878 |
*/ |
879 |
static final class RandomIntsSpliterator implements Spliterator.OfInt { |
880 |
final SplittableRandom rng; |
881 |
long index; |
882 |
final long fence; |
883 |
final int origin; |
884 |
final int bound; |
885 |
RandomIntsSpliterator(SplittableRandom rng, long index, long fence, |
886 |
int origin, int bound) { |
887 |
this.rng = rng; this.index = index; this.fence = fence; |
888 |
this.origin = origin; this.bound = bound; |
889 |
} |
890 |
|
891 |
public RandomIntsSpliterator trySplit() { |
892 |
long i = index, m = (i + fence) >>> 1; |
893 |
return (m <= i) ? null : |
894 |
new RandomIntsSpliterator(rng.split(), i, index = m, origin, bound); |
895 |
} |
896 |
|
897 |
public long estimateSize() { |
898 |
return fence - index; |
899 |
} |
900 |
|
901 |
public int characteristics() { |
902 |
return (Spliterator.SIZED | Spliterator.SUBSIZED | |
903 |
Spliterator.NONNULL | Spliterator.IMMUTABLE); |
904 |
} |
905 |
|
906 |
public boolean tryAdvance(IntConsumer consumer) { |
907 |
if (consumer == null) throw new NullPointerException(); |
908 |
long i = index, f = fence; |
909 |
if (i < f) { |
910 |
consumer.accept(rng.internalNextInt(origin, bound)); |
911 |
index = i + 1; |
912 |
return true; |
913 |
} |
914 |
return false; |
915 |
} |
916 |
|
917 |
public void forEachRemaining(IntConsumer consumer) { |
918 |
if (consumer == null) throw new NullPointerException(); |
919 |
long i = index, f = fence; |
920 |
if (i < f) { |
921 |
index = f; |
922 |
int o = origin, b = bound; |
923 |
do { |
924 |
consumer.accept(rng.internalNextInt(o, b)); |
925 |
} while (++i < f); |
926 |
} |
927 |
} |
928 |
} |
929 |
|
930 |
/** |
931 |
* Spliterator for long streams. |
932 |
*/ |
933 |
static final class RandomLongsSpliterator implements Spliterator.OfLong { |
934 |
final SplittableRandom rng; |
935 |
long index; |
936 |
final long fence; |
937 |
final long origin; |
938 |
final long bound; |
939 |
RandomLongsSpliterator(SplittableRandom rng, long index, long fence, |
940 |
long origin, long bound) { |
941 |
this.rng = rng; this.index = index; this.fence = fence; |
942 |
this.origin = origin; this.bound = bound; |
943 |
} |
944 |
|
945 |
public RandomLongsSpliterator trySplit() { |
946 |
long i = index, m = (i + fence) >>> 1; |
947 |
return (m <= i) ? null : |
948 |
new RandomLongsSpliterator(rng.split(), i, index = m, origin, bound); |
949 |
} |
950 |
|
951 |
public long estimateSize() { |
952 |
return fence - index; |
953 |
} |
954 |
|
955 |
public int characteristics() { |
956 |
return (Spliterator.SIZED | Spliterator.SUBSIZED | |
957 |
Spliterator.NONNULL | Spliterator.IMMUTABLE); |
958 |
} |
959 |
|
960 |
public boolean tryAdvance(LongConsumer consumer) { |
961 |
if (consumer == null) throw new NullPointerException(); |
962 |
long i = index, f = fence; |
963 |
if (i < f) { |
964 |
consumer.accept(rng.internalNextLong(origin, bound)); |
965 |
index = i + 1; |
966 |
return true; |
967 |
} |
968 |
return false; |
969 |
} |
970 |
|
971 |
public void forEachRemaining(LongConsumer consumer) { |
972 |
if (consumer == null) throw new NullPointerException(); |
973 |
long i = index, f = fence; |
974 |
if (i < f) { |
975 |
index = f; |
976 |
long o = origin, b = bound; |
977 |
do { |
978 |
consumer.accept(rng.internalNextLong(o, b)); |
979 |
} while (++i < f); |
980 |
} |
981 |
} |
982 |
|
983 |
} |
984 |
|
985 |
/** |
986 |
* Spliterator for double streams. |
987 |
*/ |
988 |
static final class RandomDoublesSpliterator implements Spliterator.OfDouble { |
989 |
final SplittableRandom rng; |
990 |
long index; |
991 |
final long fence; |
992 |
final double origin; |
993 |
final double bound; |
994 |
RandomDoublesSpliterator(SplittableRandom rng, long index, long fence, |
995 |
double origin, double bound) { |
996 |
this.rng = rng; this.index = index; this.fence = fence; |
997 |
this.origin = origin; this.bound = bound; |
998 |
} |
999 |
|
1000 |
public RandomDoublesSpliterator trySplit() { |
1001 |
long i = index, m = (i + fence) >>> 1; |
1002 |
return (m <= i) ? null : |
1003 |
new RandomDoublesSpliterator(rng.split(), i, index = m, origin, bound); |
1004 |
} |
1005 |
|
1006 |
public long estimateSize() { |
1007 |
return fence - index; |
1008 |
} |
1009 |
|
1010 |
public int characteristics() { |
1011 |
return (Spliterator.SIZED | Spliterator.SUBSIZED | |
1012 |
Spliterator.NONNULL | Spliterator.IMMUTABLE); |
1013 |
} |
1014 |
|
1015 |
public boolean tryAdvance(DoubleConsumer consumer) { |
1016 |
if (consumer == null) throw new NullPointerException(); |
1017 |
long i = index, f = fence; |
1018 |
if (i < f) { |
1019 |
consumer.accept(rng.internalNextDouble(origin, bound)); |
1020 |
index = i + 1; |
1021 |
return true; |
1022 |
} |
1023 |
return false; |
1024 |
} |
1025 |
|
1026 |
public void forEachRemaining(DoubleConsumer consumer) { |
1027 |
if (consumer == null) throw new NullPointerException(); |
1028 |
long i = index, f = fence; |
1029 |
if (i < f) { |
1030 |
index = f; |
1031 |
double o = origin, b = bound; |
1032 |
do { |
1033 |
consumer.accept(rng.internalNextDouble(o, b)); |
1034 |
} while (++i < f); |
1035 |
} |
1036 |
} |
1037 |
} |
1038 |
|
1039 |
} |