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package java.util; |
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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.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.function.DoubleConsumer; |
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import java.util.stream.StreamSupport; |
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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.DoubleStream; |
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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 SplittableRandom supports methods for |
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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: <ul> |
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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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* 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. </li> |
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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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* <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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* 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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* |
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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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* 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 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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public final class SplittableRandom { |
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|
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/* |
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* Implementation Overview. |
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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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* 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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* 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 System.nanotime(), |
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* and update using another "genuinely random" constant |
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* DEFAULT_SEED_GAMMA. The default constructor uses GAMMA_GAMMA, |
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* not 0, for its splitSeed argument (addGammaModGeorge(0, |
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* GAMMA_GAMMA) == GAMMA_GAMMA) to reflect that each is split from |
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* this root generator, even though the root is not explicitly |
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* represented as a SplittableRandom. |
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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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* 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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private static final long DEFAULT_SEED_GAMMA = 0xBD24B73A95FB84D9L; |
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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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* The golden ratio scaled to 64bits, used as the initial gamma |
159 |
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* value for (unsplit) SplittableRandoms. |
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*/ |
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private static final double DOUBLE_UNIT = 1.0 / (1L << 53); |
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private static final long GOLDEN_GAMMA = 0x9e3779b97f4a7c15L; |
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|
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/** |
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* The next seed for default constructors. |
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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 AtomicLong defaultSeedGenerator = |
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new AtomicLong(System.nanoTime()); |
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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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* 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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* 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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* 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. |
217 |
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* |
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* @param s a seed value |
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* @param g a gamma value, 13 <= g (as unsigned) |
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* Internal constructor used by all others except default constructor. |
181 |
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*/ |
182 |
< |
private static long addGammaModGeorge(long s, long g) { |
183 |
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long p = s + g; |
184 |
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if (Long.compareUnsigned(p, g) >= 0) |
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return p; |
225 |
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long q = p - 13L; |
226 |
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return (Long.compareUnsigned(p, 13L) >= 0) ? q : (q + g); |
182 |
> |
private SplittableRandom(long seed, long gamma) { |
183 |
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this.seed = seed; |
184 |
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this.gamma = gamma; |
185 |
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} |
186 |
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|
187 |
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/** |
188 |
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* Returns a bit-mixed transformation of its argument. |
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* See above for explanation. |
188 |
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* Computes Stafford variant 13 of 64bit mix function. |
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*/ |
190 |
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private static long mix64(long z) { |
191 |
< |
z ^= (z >>> 33); |
192 |
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z *= 0xff51afd7ed558ccdL; |
193 |
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z ^= (z >>> 33); |
237 |
< |
z *= 0xc4ceb9fe1a85ec53L; |
238 |
< |
z ^= (z >>> 33); |
239 |
< |
return z; |
191 |
> |
z = (z ^ (z >>> 30)) * 0xbf58476d1ce4e5b9L; |
192 |
> |
z = (z ^ (z >>> 27)) * 0x94d049bb133111ebL; |
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return z ^ (z >>> 31); |
194 |
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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. |
197 |
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* Returns the 32 high bits of Stafford variant 4 mix64 function as int. |
198 |
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*/ |
199 |
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private static int mix32(long z) { |
200 |
< |
z ^= (z >>> 33); |
201 |
< |
z *= 0xc4ceb9fe1a85ec53L; |
249 |
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return (int)(z >>> 32); |
200 |
> |
z = (z ^ (z >>> 33)) * 0x62a9d9ed799705f5L; |
201 |
> |
return (int)(((z ^ (z >>> 28)) * 0xcb24d0a5c88c35b3L) >>> 32); |
202 |
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} |
203 |
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|
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/** |
205 |
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* Internal constructor used by all other constructors and by |
254 |
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* method split. Establishes the initial seed for this instance, |
255 |
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* and uses the given splitSeed to establish gamma, as well as the |
256 |
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* nextSplit to use by this instance. The loop to skip ineligible |
257 |
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* gammas very rarely iterates, and does so at most 13 times. |
205 |
> |
* Returns the gamma value to use for a new split instance. |
206 |
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*/ |
207 |
< |
private SplittableRandom(long seed, long splitSeed) { |
208 |
< |
this.seed = seed; |
209 |
< |
long s = splitSeed, g; |
210 |
< |
do { // ensure gamma >= 13, considered as an unsigned integer |
211 |
< |
s = addGammaModGeorge(s, GAMMA_GAMMA); |
212 |
< |
g = mix64(s); |
265 |
< |
} while (Long.compareUnsigned(g, 13L) < 0); |
266 |
< |
this.gamma = g; |
267 |
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this.nextSplit = s; |
207 |
> |
private static long mixGamma(long z) { |
208 |
> |
z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL; // MurmurHash3 mix constants |
209 |
> |
z = (z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L; |
210 |
> |
z = (z ^ (z >>> 33)) | 1L; // force to be odd |
211 |
> |
int n = Long.bitCount(z ^ (z >>> 1)); // ensure enough transitions |
212 |
> |
return (n < 24) ? z ^ 0xaaaaaaaaaaaaaaaaL : z; |
213 |
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} |
214 |
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|
215 |
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/** |
216 |
< |
* Updates in-place and returns seed. |
272 |
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* See above for explanation. |
216 |
> |
* Adds gamma to seed. |
217 |
|
*/ |
218 |
|
private long nextSeed() { |
219 |
< |
return seed = addGammaModGeorge(seed, gamma); |
219 |
> |
return seed += gamma; |
220 |
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} |
221 |
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|
222 |
< |
/** |
223 |
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* Atomically updates and returns next seed for default constructor. |
224 |
< |
*/ |
225 |
< |
private static long nextDefaultSeed() { |
226 |
< |
long oldSeed, newSeed; |
227 |
< |
do { |
228 |
< |
oldSeed = defaultSeedGenerator.get(); |
229 |
< |
newSeed = addGammaModGeorge(oldSeed, DEFAULT_SEED_GAMMA); |
230 |
< |
} while (!defaultSeedGenerator.compareAndSet(oldSeed, newSeed)); |
231 |
< |
return mix64(newSeed); |
222 |
> |
// IllegalArgumentException messages |
223 |
> |
static final String BAD_BOUND = "bound must be positive"; |
224 |
> |
static final String BAD_RANGE = "bound must be greater than origin"; |
225 |
> |
static final String BAD_SIZE = "size must be non-negative"; |
226 |
> |
|
227 |
> |
/** |
228 |
> |
* The seed generator for default constructors. |
229 |
> |
*/ |
230 |
> |
private static final AtomicLong defaultGen |
231 |
> |
= new AtomicLong(mix64(System.currentTimeMillis()) ^ |
232 |
> |
mix64(System.nanoTime())); |
233 |
> |
|
234 |
> |
// at end of <clinit> to survive static initialization circularity |
235 |
> |
static { |
236 |
> |
if (java.security.AccessController.doPrivileged( |
237 |
> |
new java.security.PrivilegedAction<Boolean>() { |
238 |
> |
public Boolean run() { |
239 |
> |
return Boolean.getBoolean("java.util.secureRandomSeed"); |
240 |
> |
}})) { |
241 |
> |
byte[] seedBytes = java.security.SecureRandom.getSeed(8); |
242 |
> |
long s = (long)seedBytes[0] & 0xffL; |
243 |
> |
for (int i = 1; i < 8; ++i) |
244 |
> |
s = (s << 8) | ((long)seedBytes[i] & 0xffL); |
245 |
> |
defaultGen.set(s); |
246 |
> |
} |
247 |
|
} |
248 |
|
|
249 |
|
/* |
321 |
|
int r = mix32(nextSeed()); |
322 |
|
if (origin < bound) { |
323 |
|
int n = bound - origin, m = n - 1; |
324 |
< |
if ((n & m) == 0L) |
324 |
> |
if ((n & m) == 0) |
325 |
|
r = (r & m) + origin; |
326 |
|
else if (n > 0) { |
327 |
|
for (int u = r >>> 1; |
360 |
|
/** |
361 |
|
* Creates a new SplittableRandom instance using the specified |
362 |
|
* initial seed. SplittableRandom instances created with the same |
363 |
< |
* seed generate identical sequences of values. |
363 |
> |
* seed in the same program generate identical sequences of values. |
364 |
|
* |
365 |
|
* @param seed the initial seed |
366 |
|
*/ |
367 |
|
public SplittableRandom(long seed) { |
368 |
< |
this(seed, 0); |
368 |
> |
this(seed, GOLDEN_GAMMA); |
369 |
|
} |
370 |
|
|
371 |
|
/** |
374 |
|
* of those of any other instances in the current program; and |
375 |
|
* may, and typically does, vary across program invocations. |
376 |
|
*/ |
377 |
< |
public SplittableRandom() { |
378 |
< |
this(nextDefaultSeed(), GAMMA_GAMMA); |
377 |
> |
public SplittableRandom() { // emulate defaultGen.split() |
378 |
> |
long s = defaultGen.getAndAdd(2 * GOLDEN_GAMMA); |
379 |
> |
this.seed = mix64(s); |
380 |
> |
this.gamma = mixGamma(s + GOLDEN_GAMMA); |
381 |
|
} |
382 |
|
|
383 |
|
/** |
395 |
|
* @return the new SplittableRandom instance |
396 |
|
*/ |
397 |
|
public SplittableRandom split() { |
398 |
< |
return new SplittableRandom(nextSeed(), nextSplit); |
398 |
> |
return new SplittableRandom(nextLong(), mixGamma(nextSeed())); |
399 |
|
} |
400 |
|
|
401 |
|
/** |
411 |
|
* Returns a pseudorandom {@code int} value between zero (inclusive) |
412 |
|
* and the specified bound (exclusive). |
413 |
|
* |
414 |
< |
* @param bound the bound on the random number to be returned. Must be |
454 |
< |
* positive. |
414 |
> |
* @param bound the upper bound (exclusive). Must be positive. |
415 |
|
* @return a pseudorandom {@code int} value between zero |
416 |
< |
* (inclusive) and the bound (exclusive). |
417 |
< |
* @throws IllegalArgumentException if the bound is less than zero |
416 |
> |
* (inclusive) and the bound (exclusive) |
417 |
> |
* @throws IllegalArgumentException if {@code bound} is not positive |
418 |
|
*/ |
419 |
|
public int nextInt(int bound) { |
420 |
|
if (bound <= 0) |
421 |
< |
throw new IllegalArgumentException("bound must be positive"); |
421 |
> |
throw new IllegalArgumentException(BAD_BOUND); |
422 |
|
// Specialize internalNextInt for origin 0 |
423 |
|
int r = mix32(nextSeed()); |
424 |
|
int m = bound - 1; |
425 |
< |
if ((bound & m) == 0L) // power of two |
425 |
> |
if ((bound & m) == 0) // power of two |
426 |
|
r &= m; |
427 |
|
else { // reject over-represented candidates |
428 |
|
for (int u = r >>> 1; |
440 |
|
* @param origin the least value returned |
441 |
|
* @param bound the upper bound (exclusive) |
442 |
|
* @return a pseudorandom {@code int} value between the origin |
443 |
< |
* (inclusive) and the bound (exclusive). |
443 |
> |
* (inclusive) and the bound (exclusive) |
444 |
|
* @throws IllegalArgumentException if {@code origin} is greater than |
445 |
|
* or equal to {@code bound} |
446 |
|
*/ |
447 |
|
public int nextInt(int origin, int bound) { |
448 |
|
if (origin >= bound) |
449 |
< |
throw new IllegalArgumentException("bound must be greater than origin"); |
449 |
> |
throw new IllegalArgumentException(BAD_RANGE); |
450 |
|
return internalNextInt(origin, bound); |
451 |
|
} |
452 |
|
|
463 |
|
* Returns a pseudorandom {@code long} value between zero (inclusive) |
464 |
|
* and the specified bound (exclusive). |
465 |
|
* |
466 |
< |
* @param bound the bound on the random number to be returned. Must be |
507 |
< |
* positive. |
466 |
> |
* @param bound the upper bound (exclusive). Must be positive. |
467 |
|
* @return a pseudorandom {@code long} value between zero |
468 |
< |
* (inclusive) and the bound (exclusive). |
469 |
< |
* @throws IllegalArgumentException if {@code bound} is less than zero |
468 |
> |
* (inclusive) and the bound (exclusive) |
469 |
> |
* @throws IllegalArgumentException if {@code bound} is not positive |
470 |
|
*/ |
471 |
|
public long nextLong(long bound) { |
472 |
|
if (bound <= 0) |
473 |
< |
throw new IllegalArgumentException("bound must be positive"); |
473 |
> |
throw new IllegalArgumentException(BAD_BOUND); |
474 |
|
// Specialize internalNextLong for origin 0 |
475 |
|
long r = mix64(nextSeed()); |
476 |
|
long m = bound - 1; |
492 |
|
* @param origin the least value returned |
493 |
|
* @param bound the upper bound (exclusive) |
494 |
|
* @return a pseudorandom {@code long} value between the origin |
495 |
< |
* (inclusive) and the bound (exclusive). |
495 |
> |
* (inclusive) and the bound (exclusive) |
496 |
|
* @throws IllegalArgumentException if {@code origin} is greater than |
497 |
|
* or equal to {@code bound} |
498 |
|
*/ |
499 |
|
public long nextLong(long origin, long bound) { |
500 |
|
if (origin >= bound) |
501 |
< |
throw new IllegalArgumentException("bound must be greater than origin"); |
501 |
> |
throw new IllegalArgumentException(BAD_RANGE); |
502 |
|
return internalNextLong(origin, bound); |
503 |
|
} |
504 |
|
|
507 |
|
* (inclusive) and one (exclusive). |
508 |
|
* |
509 |
|
* @return a pseudorandom {@code double} value between zero |
510 |
< |
* (inclusive) and one (exclusive) |
510 |
> |
* (inclusive) and one (exclusive) |
511 |
|
*/ |
512 |
|
public double nextDouble() { |
513 |
< |
return (nextLong() >>> 11) * DOUBLE_UNIT; |
513 |
> |
return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT; |
514 |
|
} |
515 |
|
|
516 |
|
/** |
517 |
|
* Returns a pseudorandom {@code double} value between 0.0 |
518 |
|
* (inclusive) and the specified bound (exclusive). |
519 |
|
* |
520 |
< |
* @param bound the bound on the random number to be returned. Must be |
562 |
< |
* positive. |
520 |
> |
* @param bound the upper bound (exclusive). Must be positive. |
521 |
|
* @return a pseudorandom {@code double} value between zero |
522 |
< |
* (inclusive) and the bound (exclusive). |
523 |
< |
* @throws IllegalArgumentException if {@code bound} is less than zero |
522 |
> |
* (inclusive) and the bound (exclusive) |
523 |
> |
* @throws IllegalArgumentException if {@code bound} is not positive |
524 |
|
*/ |
525 |
|
public double nextDouble(double bound) { |
526 |
|
if (!(bound > 0.0)) |
527 |
< |
throw new IllegalArgumentException("bound must be positive"); |
528 |
< |
double result = nextDouble() * bound; |
527 |
> |
throw new IllegalArgumentException(BAD_BOUND); |
528 |
> |
double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound; |
529 |
|
return (result < bound) ? result : // correct for rounding |
530 |
|
Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1); |
531 |
|
} |
532 |
|
|
533 |
|
/** |
534 |
+ |
* Generates a pseudorandom number with the indicated number of |
535 |
+ |
* bits. Unlike in superclass @{link Random}, this method is never |
536 |
+ |
* internally called or used by any other publicly accessible |
537 |
+ |
* method. |
538 |
+ |
* |
539 |
+ |
* @param bits random bits |
540 |
+ |
* @return the next pseudorandom value from this random number |
541 |
+ |
* generator's sequence |
542 |
+ |
*/ |
543 |
+ |
protected int next(int bits) { |
544 |
+ |
return (int)(nextLong() >>> (64 - bits)); |
545 |
+ |
} |
546 |
+ |
|
547 |
+ |
/** |
548 |
|
* Returns a pseudorandom {@code double} value between the specified |
549 |
|
* origin (inclusive) and bound (exclusive). |
550 |
|
* |
551 |
|
* @param origin the least value returned |
552 |
< |
* @param bound the upper bound |
552 |
> |
* @param bound the upper bound (exclusive) |
553 |
|
* @return a pseudorandom {@code double} value between the origin |
554 |
< |
* (inclusive) and the bound (exclusive). |
554 |
> |
* (inclusive) and the bound (exclusive) |
555 |
|
* @throws IllegalArgumentException if {@code origin} is greater than |
556 |
|
* or equal to {@code bound} |
557 |
|
*/ |
558 |
|
public double nextDouble(double origin, double bound) { |
559 |
|
if (!(origin < bound)) |
560 |
< |
throw new IllegalArgumentException("bound must be greater than origin"); |
560 |
> |
throw new IllegalArgumentException(BAD_RANGE); |
561 |
|
return internalNextDouble(origin, bound); |
562 |
|
} |
563 |
|
|
564 |
+ |
/** |
565 |
+ |
* Returns a pseudorandom {@code boolean} value. |
566 |
+ |
* |
567 |
+ |
* @return a pseudorandom {@code boolean} value |
568 |
+ |
*/ |
569 |
+ |
public boolean nextBoolean() { |
570 |
+ |
return mix32(nextSeed()) < 0; |
571 |
+ |
} |
572 |
+ |
|
573 |
|
// stream methods, coded in a way intended to better isolate for |
574 |
|
// maintenance purposes the small differences across forms. |
575 |
|
|
576 |
|
/** |
577 |
< |
* Returns a stream producing the given {@code streamSize} number of |
578 |
< |
* pseudorandom {@code int} values. |
577 |
> |
* Returns a stream producing the given {@code streamSize} number |
578 |
> |
* of pseudorandom {@code int} values from this generator and/or |
579 |
> |
* one split from it. |
580 |
|
* |
581 |
|
* @param streamSize the number of values to generate |
582 |
|
* @return a stream of pseudorandom {@code int} values |
585 |
|
*/ |
586 |
|
public IntStream ints(long streamSize) { |
587 |
|
if (streamSize < 0L) |
588 |
< |
throw new IllegalArgumentException("negative Stream size"); |
588 |
> |
throw new IllegalArgumentException(BAD_SIZE); |
589 |
|
return StreamSupport.intStream |
590 |
|
(new RandomIntsSpliterator |
591 |
|
(this, 0L, streamSize, Integer.MAX_VALUE, 0), |
594 |
|
|
595 |
|
/** |
596 |
|
* Returns an effectively unlimited stream of pseudorandom {@code int} |
597 |
< |
* values |
597 |
> |
* values from this generator and/or one split from it. |
598 |
|
* |
599 |
|
* @implNote This method is implemented to be equivalent to {@code |
600 |
|
* ints(Long.MAX_VALUE)}. |
609 |
|
} |
610 |
|
|
611 |
|
/** |
612 |
< |
* Returns a stream producing the given {@code streamSize} number of |
613 |
< |
* pseudorandom {@code int} values, each conforming to the given |
614 |
< |
* origin and bound. |
612 |
> |
* Returns a stream producing the given {@code streamSize} number |
613 |
> |
* of pseudorandom {@code int} values from this generator and/or one split |
614 |
> |
* from it; each value conforms to the given origin (inclusive) and bound |
615 |
> |
* (exclusive). |
616 |
|
* |
617 |
|
* @param streamSize the number of values to generate |
618 |
< |
* @param randomNumberOrigin the origin of each random value |
619 |
< |
* @param randomNumberBound the bound of each random value |
618 |
> |
* @param randomNumberOrigin the origin (inclusive) of each random value |
619 |
> |
* @param randomNumberBound the bound (exclusive) of each random value |
620 |
|
* @return a stream of pseudorandom {@code int} values, |
621 |
< |
* each with the given origin and bound. |
621 |
> |
* each with the given origin (inclusive) and bound (exclusive) |
622 |
|
* @throws IllegalArgumentException if {@code streamSize} is |
623 |
|
* less than zero, or {@code randomNumberOrigin} |
624 |
|
* is greater than or equal to {@code randomNumberBound} |
626 |
|
public IntStream ints(long streamSize, int randomNumberOrigin, |
627 |
|
int randomNumberBound) { |
628 |
|
if (streamSize < 0L) |
629 |
< |
throw new IllegalArgumentException("negative Stream size"); |
629 |
> |
throw new IllegalArgumentException(BAD_SIZE); |
630 |
|
if (randomNumberOrigin >= randomNumberBound) |
631 |
< |
throw new IllegalArgumentException("bound must be greater than origin"); |
631 |
> |
throw new IllegalArgumentException(BAD_RANGE); |
632 |
|
return StreamSupport.intStream |
633 |
|
(new RandomIntsSpliterator |
634 |
|
(this, 0L, streamSize, randomNumberOrigin, randomNumberBound), |
637 |
|
|
638 |
|
/** |
639 |
|
* Returns an effectively unlimited stream of pseudorandom {@code |
640 |
< |
* int} values, each conforming to the given origin and bound. |
640 |
> |
* int} values from this generator and/or one split from it; each value |
641 |
> |
* conforms to the given origin (inclusive) and bound (exclusive). |
642 |
|
* |
643 |
|
* @implNote This method is implemented to be equivalent to {@code |
644 |
|
* ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. |
645 |
|
* |
646 |
< |
* @param randomNumberOrigin the origin of each random value |
647 |
< |
* @param randomNumberBound the bound of each random value |
646 |
> |
* @param randomNumberOrigin the origin (inclusive) of each random value |
647 |
> |
* @param randomNumberBound the bound (exclusive) of each random value |
648 |
|
* @return a stream of pseudorandom {@code int} values, |
649 |
< |
* each with the given origin and bound. |
649 |
> |
* each with the given origin (inclusive) and bound (exclusive) |
650 |
|
* @throws IllegalArgumentException if {@code randomNumberOrigin} |
651 |
|
* is greater than or equal to {@code randomNumberBound} |
652 |
|
*/ |
653 |
|
public IntStream ints(int randomNumberOrigin, int randomNumberBound) { |
654 |
|
if (randomNumberOrigin >= randomNumberBound) |
655 |
< |
throw new IllegalArgumentException("bound must be greater than origin"); |
655 |
> |
throw new IllegalArgumentException(BAD_RANGE); |
656 |
|
return StreamSupport.intStream |
657 |
|
(new RandomIntsSpliterator |
658 |
|
(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), |
660 |
|
} |
661 |
|
|
662 |
|
/** |
663 |
< |
* Returns a stream producing the given {@code streamSize} number of |
664 |
< |
* pseudorandom {@code long} values. |
663 |
> |
* Returns a stream producing the given {@code streamSize} number |
664 |
> |
* of pseudorandom {@code long} values from this generator and/or |
665 |
> |
* one split from it. |
666 |
|
* |
667 |
|
* @param streamSize the number of values to generate |
668 |
|
* @return a stream of pseudorandom {@code long} values |
671 |
|
*/ |
672 |
|
public LongStream longs(long streamSize) { |
673 |
|
if (streamSize < 0L) |
674 |
< |
throw new IllegalArgumentException("negative Stream size"); |
674 |
> |
throw new IllegalArgumentException(BAD_SIZE); |
675 |
|
return StreamSupport.longStream |
676 |
|
(new RandomLongsSpliterator |
677 |
|
(this, 0L, streamSize, Long.MAX_VALUE, 0L), |
679 |
|
} |
680 |
|
|
681 |
|
/** |
682 |
< |
* Returns an effectively unlimited stream of pseudorandom {@code long} |
683 |
< |
* values. |
682 |
> |
* Returns an effectively unlimited stream of pseudorandom {@code |
683 |
> |
* long} values from this generator and/or one split from it. |
684 |
|
* |
685 |
|
* @implNote This method is implemented to be equivalent to {@code |
686 |
|
* longs(Long.MAX_VALUE)}. |
696 |
|
|
697 |
|
/** |
698 |
|
* Returns a stream producing the given {@code streamSize} number of |
699 |
< |
* pseudorandom {@code long} values, each conforming to the |
700 |
< |
* given origin and bound. |
699 |
> |
* pseudorandom {@code long} values from this generator and/or one split |
700 |
> |
* from it; each value conforms to the given origin (inclusive) and bound |
701 |
> |
* (exclusive). |
702 |
|
* |
703 |
|
* @param streamSize the number of values to generate |
704 |
< |
* @param randomNumberOrigin the origin of each random value |
705 |
< |
* @param randomNumberBound the bound of each random value |
704 |
> |
* @param randomNumberOrigin the origin (inclusive) of each random value |
705 |
> |
* @param randomNumberBound the bound (exclusive) of each random value |
706 |
|
* @return a stream of pseudorandom {@code long} values, |
707 |
< |
* each with the given origin and bound. |
707 |
> |
* each with the given origin (inclusive) and bound (exclusive) |
708 |
|
* @throws IllegalArgumentException if {@code streamSize} is |
709 |
|
* less than zero, or {@code randomNumberOrigin} |
710 |
|
* is greater than or equal to {@code randomNumberBound} |
712 |
|
public LongStream longs(long streamSize, long randomNumberOrigin, |
713 |
|
long randomNumberBound) { |
714 |
|
if (streamSize < 0L) |
715 |
< |
throw new IllegalArgumentException("negative Stream size"); |
715 |
> |
throw new IllegalArgumentException(BAD_SIZE); |
716 |
|
if (randomNumberOrigin >= randomNumberBound) |
717 |
< |
throw new IllegalArgumentException("bound must be greater than origin"); |
717 |
> |
throw new IllegalArgumentException(BAD_RANGE); |
718 |
|
return StreamSupport.longStream |
719 |
|
(new RandomLongsSpliterator |
720 |
|
(this, 0L, streamSize, randomNumberOrigin, randomNumberBound), |
723 |
|
|
724 |
|
/** |
725 |
|
* Returns an effectively unlimited stream of pseudorandom {@code |
726 |
< |
* long} values, each conforming to the given origin and bound. |
726 |
> |
* long} values from this generator and/or one split from it; each value |
727 |
> |
* conforms to the given origin (inclusive) and bound (exclusive). |
728 |
|
* |
729 |
|
* @implNote This method is implemented to be equivalent to {@code |
730 |
|
* longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. |
731 |
|
* |
732 |
< |
* @param randomNumberOrigin the origin of each random value |
733 |
< |
* @param randomNumberBound the bound of each random value |
732 |
> |
* @param randomNumberOrigin the origin (inclusive) of each random value |
733 |
> |
* @param randomNumberBound the bound (exclusive) of each random value |
734 |
|
* @return a stream of pseudorandom {@code long} values, |
735 |
< |
* each with the given origin and bound. |
735 |
> |
* each with the given origin (inclusive) and bound (exclusive) |
736 |
|
* @throws IllegalArgumentException if {@code randomNumberOrigin} |
737 |
|
* is greater than or equal to {@code randomNumberBound} |
738 |
|
*/ |
739 |
|
public LongStream longs(long randomNumberOrigin, long randomNumberBound) { |
740 |
|
if (randomNumberOrigin >= randomNumberBound) |
741 |
< |
throw new IllegalArgumentException("bound must be greater than origin"); |
741 |
> |
throw new IllegalArgumentException(BAD_RANGE); |
742 |
|
return StreamSupport.longStream |
743 |
|
(new RandomLongsSpliterator |
744 |
|
(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), |
747 |
|
|
748 |
|
/** |
749 |
|
* Returns a stream producing the given {@code streamSize} number of |
750 |
< |
* pseudorandom {@code double} values, each between zero |
751 |
< |
* (inclusive) and one (exclusive). |
750 |
> |
* pseudorandom {@code double} values from this generator and/or one split |
751 |
> |
* from it; each value is between zero (inclusive) and one (exclusive). |
752 |
|
* |
753 |
|
* @param streamSize the number of values to generate |
754 |
|
* @return a stream of {@code double} values |
757 |
|
*/ |
758 |
|
public DoubleStream doubles(long streamSize) { |
759 |
|
if (streamSize < 0L) |
760 |
< |
throw new IllegalArgumentException("negative Stream size"); |
760 |
> |
throw new IllegalArgumentException(BAD_SIZE); |
761 |
|
return StreamSupport.doubleStream |
762 |
|
(new RandomDoublesSpliterator |
763 |
|
(this, 0L, streamSize, Double.MAX_VALUE, 0.0), |
766 |
|
|
767 |
|
/** |
768 |
|
* Returns an effectively unlimited stream of pseudorandom {@code |
769 |
< |
* double} values, each between zero (inclusive) and one |
770 |
< |
* (exclusive). |
769 |
> |
* double} values from this generator and/or one split from it; each value |
770 |
> |
* is between zero (inclusive) and one (exclusive). |
771 |
|
* |
772 |
|
* @implNote This method is implemented to be equivalent to {@code |
773 |
|
* doubles(Long.MAX_VALUE)}. |
783 |
|
|
784 |
|
/** |
785 |
|
* Returns a stream producing the given {@code streamSize} number of |
786 |
< |
* pseudorandom {@code double} values, each conforming to the |
787 |
< |
* given origin and bound. |
786 |
> |
* pseudorandom {@code double} values from this generator and/or one split |
787 |
> |
* from it; each value conforms to the given origin (inclusive) and bound |
788 |
> |
* (exclusive). |
789 |
|
* |
790 |
|
* @param streamSize the number of values to generate |
791 |
< |
* @param randomNumberOrigin the origin of each random value |
792 |
< |
* @param randomNumberBound the bound of each random value |
791 |
> |
* @param randomNumberOrigin the origin (inclusive) of each random value |
792 |
> |
* @param randomNumberBound the bound (exclusive) of each random value |
793 |
|
* @return a stream of pseudorandom {@code double} values, |
794 |
< |
* each with the given origin and bound. |
794 |
> |
* each with the given origin (inclusive) and bound (exclusive) |
795 |
|
* @throws IllegalArgumentException if {@code streamSize} is |
796 |
< |
* less than zero. |
796 |
> |
* less than zero |
797 |
|
* @throws IllegalArgumentException if {@code randomNumberOrigin} |
798 |
|
* is greater than or equal to {@code randomNumberBound} |
799 |
|
*/ |
800 |
|
public DoubleStream doubles(long streamSize, double randomNumberOrigin, |
801 |
|
double randomNumberBound) { |
802 |
|
if (streamSize < 0L) |
803 |
< |
throw new IllegalArgumentException("negative Stream size"); |
803 |
> |
throw new IllegalArgumentException(BAD_SIZE); |
804 |
|
if (!(randomNumberOrigin < randomNumberBound)) |
805 |
< |
throw new IllegalArgumentException("bound must be greater than origin"); |
805 |
> |
throw new IllegalArgumentException(BAD_RANGE); |
806 |
|
return StreamSupport.doubleStream |
807 |
|
(new RandomDoublesSpliterator |
808 |
|
(this, 0L, streamSize, randomNumberOrigin, randomNumberBound), |
811 |
|
|
812 |
|
/** |
813 |
|
* Returns an effectively unlimited stream of pseudorandom {@code |
814 |
< |
* double} values, each conforming to the given origin and bound. |
814 |
> |
* double} values from this generator and/or one split from it; each value |
815 |
> |
* conforms to the given origin (inclusive) and bound (exclusive). |
816 |
|
* |
817 |
|
* @implNote This method is implemented to be equivalent to {@code |
818 |
|
* doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. |
819 |
|
* |
820 |
< |
* @param randomNumberOrigin the origin of each random value |
821 |
< |
* @param randomNumberBound the bound of each random value |
820 |
> |
* @param randomNumberOrigin the origin (inclusive) of each random value |
821 |
> |
* @param randomNumberBound the bound (exclusive) of each random value |
822 |
|
* @return a stream of pseudorandom {@code double} values, |
823 |
< |
* each with the given origin and bound. |
823 |
> |
* each with the given origin (inclusive) and bound (exclusive) |
824 |
|
* @throws IllegalArgumentException if {@code randomNumberOrigin} |
825 |
|
* is greater than or equal to {@code randomNumberBound} |
826 |
|
*/ |
827 |
|
public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) { |
828 |
|
if (!(randomNumberOrigin < randomNumberBound)) |
829 |
< |
throw new IllegalArgumentException("bound must be greater than origin"); |
829 |
> |
throw new IllegalArgumentException(BAD_RANGE); |
830 |
|
return StreamSupport.doubleStream |
831 |
|
(new RandomDoublesSpliterator |
832 |
|
(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), |
841 |
|
* approach. The long and double versions of this class are |
842 |
|
* identical except for types. |
843 |
|
*/ |
844 |
< |
static class RandomIntsSpliterator implements Spliterator.OfInt { |
844 |
> |
private static final class RandomIntsSpliterator |
845 |
> |
implements Spliterator.OfInt { |
846 |
|
final SplittableRandom rng; |
847 |
|
long index; |
848 |
|
final long fence; |
885 |
|
long i = index, f = fence; |
886 |
|
if (i < f) { |
887 |
|
index = f; |
888 |
+ |
SplittableRandom r = rng; |
889 |
|
int o = origin, b = bound; |
890 |
|
do { |
891 |
< |
consumer.accept(rng.internalNextInt(o, b)); |
891 |
> |
consumer.accept(r.internalNextInt(o, b)); |
892 |
|
} while (++i < f); |
893 |
|
} |
894 |
|
} |
897 |
|
/** |
898 |
|
* Spliterator for long streams. |
899 |
|
*/ |
900 |
< |
static class RandomLongsSpliterator implements Spliterator.OfLong { |
900 |
> |
private static final class RandomLongsSpliterator |
901 |
> |
implements Spliterator.OfLong { |
902 |
|
final SplittableRandom rng; |
903 |
|
long index; |
904 |
|
final long fence; |
941 |
|
long i = index, f = fence; |
942 |
|
if (i < f) { |
943 |
|
index = f; |
944 |
+ |
SplittableRandom r = rng; |
945 |
|
long o = origin, b = bound; |
946 |
|
do { |
947 |
< |
consumer.accept(rng.internalNextLong(o, b)); |
947 |
> |
consumer.accept(r.internalNextLong(o, b)); |
948 |
|
} while (++i < f); |
949 |
|
} |
950 |
|
} |
954 |
|
/** |
955 |
|
* Spliterator for double streams. |
956 |
|
*/ |
957 |
< |
static class RandomDoublesSpliterator implements Spliterator.OfDouble { |
957 |
> |
private static final class RandomDoublesSpliterator |
958 |
> |
implements Spliterator.OfDouble { |
959 |
|
final SplittableRandom rng; |
960 |
|
long index; |
961 |
|
final long fence; |
998 |
|
long i = index, f = fence; |
999 |
|
if (i < f) { |
1000 |
|
index = f; |
1001 |
+ |
SplittableRandom r = rng; |
1002 |
|
double o = origin, b = bound; |
1003 |
|
do { |
1004 |
< |
consumer.accept(rng.internalNextDouble(o, b)); |
1004 |
> |
consumer.accept(r.internalNextDouble(o, b)); |
1005 |
|
} while (++i < f); |
1006 |
|
} |
1007 |
|
} |