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⏎ java/util/SplittableRandom.java
/*
* Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
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package java.util;
import java.util.concurrent.atomic.AtomicLong;
import java.util.function.DoubleConsumer;
import java.util.function.IntConsumer;
import java.util.function.LongConsumer;
import java.util.stream.DoubleStream;
import java.util.stream.IntStream;
import java.util.stream.LongStream;
import java.util.stream.StreamSupport;
/**
* A generator of uniform pseudorandom values applicable for use in
* (among other contexts) isolated parallel computations that may
* generate subtasks. Class {@code SplittableRandom} supports methods for
* producing pseudorandom numbers of type {@code int}, {@code long},
* and {@code double} with similar usages as for class
* {@link java.util.Random} but differs in the following ways:
*
* <ul>
*
* <li>Series of generated values pass the DieHarder suite testing
* independence and uniformity properties of random number generators.
* (Most recently validated with <a
* href="http://www.phy.duke.edu/~rgb/General/dieharder.php"> version
* 3.31.1</a>.) These tests validate only the methods for certain
* types and ranges, but similar properties are expected to hold, at
* least approximately, for others as well. The <em>period</em>
* (length of any series of generated values before it repeats) is at
* least 2<sup>64</sup>.
*
* <li>Method {@link #split} constructs and returns a new
* SplittableRandom instance that shares no mutable state with the
* current instance. However, with very high probability, the
* values collectively generated by the two objects have the same
* statistical properties as if the same quantity of values were
* generated by a single thread using a single {@code
* SplittableRandom} object.
*
* <li>Instances of SplittableRandom are <em>not</em> thread-safe.
* They are designed to be split, not shared, across threads. For
* example, a {@link java.util.concurrent.ForkJoinTask
* fork/join-style} computation using random numbers might include a
* construction of the form {@code new
* Subtask(aSplittableRandom.split()).fork()}.
*
* <li>This class provides additional methods for generating random
* streams, that employ the above techniques when used in {@code
* stream.parallel()} mode.
*
* </ul>
*
* <p>Instances of {@code SplittableRandom} are not cryptographically
* secure. Consider instead using {@link java.security.SecureRandom}
* in security-sensitive applications. Additionally,
* default-constructed instances do not use a cryptographically random
* seed unless the {@linkplain System#getProperty system property}
* {@code java.util.secureRandomSeed} is set to {@code true}.
*
* @author Guy Steele
* @author Doug Lea
* @since 1.8
*/
public final class SplittableRandom {
/*
* Implementation Overview.
*
* This algorithm was inspired by the "DotMix" algorithm by
* Leiserson, Schardl, and Sukha "Deterministic Parallel
* Random-Number Generation for Dynamic-Multithreading Platforms",
* PPoPP 2012, as well as those in "Parallel random numbers: as
* easy as 1, 2, 3" by Salmon, Morae, Dror, and Shaw, SC 2011. It
* differs mainly in simplifying and cheapening operations.
*
* The primary update step (method nextSeed()) is to add a
* constant ("gamma") to the current (64 bit) seed, forming a
* simple sequence. The seed and the gamma values for any two
* SplittableRandom instances are highly likely to be different.
*
* Methods nextLong, nextInt, and derivatives do not return the
* sequence (seed) values, but instead a hash-like bit-mix of
* their bits, producing more independently distributed sequences.
* For nextLong, the mix64 function is based on David Stafford's
* (http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html)
* "Mix13" variant of the "64-bit finalizer" function in Austin
* Appleby's MurmurHash3 algorithm (see
* http://code.google.com/p/smhasher/wiki/MurmurHash3). The mix32
* function is based on Stafford's Mix04 mix function, but returns
* the upper 32 bits cast as int.
*
* The split operation uses the current generator to form the seed
* and gamma for another SplittableRandom. To conservatively
* avoid potential correlations between seed and value generation,
* gamma selection (method mixGamma) uses different
* (Murmurhash3's) mix constants. To avoid potential weaknesses
* in bit-mixing transformations, we restrict gammas to odd values
* with at least 24 0-1 or 1-0 bit transitions. Rather than
* rejecting candidates with too few or too many bits set, method
* mixGamma flips some bits (which has the effect of mapping at
* most 4 to any given gamma value). This reduces the effective
* set of 64bit odd gamma values by about 2%, and serves as an
* automated screening for sequence constant selection that is
* left as an empirical decision in some other hashing and crypto
* algorithms.
*
* The resulting generator thus transforms a sequence in which
* (typically) many bits change on each step, with an inexpensive
* mixer with good (but less than cryptographically secure)
* avalanching.
*
* The default (no-argument) constructor, in essence, invokes
* split() for a common "defaultGen" SplittableRandom. Unlike
* other cases, this split must be performed in a thread-safe
* manner, so we use an AtomicLong to represent the seed rather
* than use an explicit SplittableRandom. To bootstrap the
* defaultGen, we start off using a seed based on current time
* unless the java.util.secureRandomSeed property is set. This
* serves as a slimmed-down (and insecure) variant of SecureRandom
* that also avoids stalls that may occur when using /dev/random.
*
* It is a relatively simple matter to apply the basic design here
* to use 128 bit seeds. However, emulating 128bit arithmetic and
* carrying around twice the state add more overhead than appears
* warranted for current usages.
*
* File organization: First the non-public methods that constitute
* the main algorithm, then the main public methods, followed by
* some custom spliterator classes needed for stream methods.
*/
/**
* The golden ratio scaled to 64bits, used as the initial gamma
* value for (unsplit) SplittableRandoms.
*/
private static final long GOLDEN_GAMMA = 0x9e3779b97f4a7c15L;
/**
* The least non-zero value returned by nextDouble(). This value
* is scaled by a random value of 53 bits to produce a result.
*/
private static final double DOUBLE_UNIT = 0x1.0p-53; // 1.0 / (1L << 53);
/**
* The seed. Updated only via method nextSeed.
*/
private long seed;
/**
* The step value.
*/
private final long gamma;
/**
* Internal constructor used by all others except default constructor.
*/
private SplittableRandom(long seed, long gamma) {
this.seed = seed;
this.gamma = gamma;
}
/**
* Computes Stafford variant 13 of 64bit mix function.
*/
private static long mix64(long z) {
z = (z ^ (z >>> 30)) * 0xbf58476d1ce4e5b9L;
z = (z ^ (z >>> 27)) * 0x94d049bb133111ebL;
return z ^ (z >>> 31);
}
/**
* Returns the 32 high bits of Stafford variant 4 mix64 function as int.
*/
private static int mix32(long z) {
z = (z ^ (z >>> 33)) * 0x62a9d9ed799705f5L;
return (int)(((z ^ (z >>> 28)) * 0xcb24d0a5c88c35b3L) >>> 32);
}
/**
* Returns the gamma value to use for a new split instance.
*/
private static long mixGamma(long z) {
z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL; // MurmurHash3 mix constants
z = (z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L;
z = (z ^ (z >>> 33)) | 1L; // force to be odd
int n = Long.bitCount(z ^ (z >>> 1)); // ensure enough transitions
return (n < 24) ? z ^ 0xaaaaaaaaaaaaaaaaL : z;
}
/**
* Adds gamma to seed.
*/
private long nextSeed() {
return seed += gamma;
}
// IllegalArgumentException messages
static final String BAD_BOUND = "bound must be positive";
static final String BAD_RANGE = "bound must be greater than origin";
static final String BAD_SIZE = "size must be non-negative";
/**
* The seed generator for default constructors.
*/
private static final AtomicLong defaultGen
= new AtomicLong(mix64(System.currentTimeMillis()) ^
mix64(System.nanoTime()));
// at end of <clinit> to survive static initialization circularity
static {
if (java.security.AccessController.doPrivileged(
new java.security.PrivilegedAction<Boolean>() {
public Boolean run() {
return Boolean.getBoolean("java.util.secureRandomSeed");
}})) {
byte[] seedBytes = java.security.SecureRandom.getSeed(8);
long s = (long)seedBytes[0] & 0xffL;
for (int i = 1; i < 8; ++i)
s = (s << 8) | ((long)seedBytes[i] & 0xffL);
defaultGen.set(s);
}
}
/*
* Internal versions of nextX methods used by streams, as well as
* the public nextX(origin, bound) methods. These exist mainly to
* avoid the need for multiple versions of stream spliterators
* across the different exported forms of streams.
*/
/**
* The form of nextLong used by LongStream Spliterators. If
* origin is greater than bound, acts as unbounded form of
* nextLong, else as bounded form.
*
* @param origin the least value, unless greater than bound
* @param bound the upper bound (exclusive), must not equal origin
* @return a pseudorandom value
*/
final long internalNextLong(long origin, long bound) {
/*
* Four Cases:
*
* 1. If the arguments indicate unbounded form, act as
* nextLong().
*
* 2. If the range is an exact power of two, apply the
* associated bit mask.
*
* 3. If the range is positive, loop to avoid potential bias
* when the implicit nextLong() bound (2<sup>64</sup>) is not
* evenly divisible by the range. The loop rejects candidates
* computed from otherwise over-represented values. The
* expected number of iterations under an ideal generator
* varies from 1 to 2, depending on the bound. The loop itself
* takes an unlovable form. Because the first candidate is
* already available, we need a break-in-the-middle
* construction, which is concisely but cryptically performed
* within the while-condition of a body-less for loop.
*
* 4. Otherwise, the range cannot be represented as a positive
* long. The loop repeatedly generates unbounded longs until
* obtaining a candidate meeting constraints (with an expected
* number of iterations of less than two).
*/
long r = mix64(nextSeed());
if (origin < bound) {
long n = bound - origin, m = n - 1;
if ((n & m) == 0L) // power of two
r = (r & m) + origin;
else if (n > 0L) { // reject over-represented candidates
for (long u = r >>> 1; // ensure nonnegative
u + m - (r = u % n) < 0L; // rejection check
u = mix64(nextSeed()) >>> 1) // retry
;
r += origin;
}
else { // range not representable as long
while (r < origin || r >= bound)
r = mix64(nextSeed());
}
}
return r;
}
/**
* The form of nextInt used by IntStream Spliterators.
* Exactly the same as long version, except for types.
*
* @param origin the least value, unless greater than bound
* @param bound the upper bound (exclusive), must not equal origin
* @return a pseudorandom value
*/
final int internalNextInt(int origin, int bound) {
int r = mix32(nextSeed());
if (origin < bound) {
int n = bound - origin, m = n - 1;
if ((n & m) == 0)
r = (r & m) + origin;
else if (n > 0) {
for (int u = r >>> 1;
u + m - (r = u % n) < 0;
u = mix32(nextSeed()) >>> 1)
;
r += origin;
}
else {
while (r < origin || r >= bound)
r = mix32(nextSeed());
}
}
return r;
}
/**
* The form of nextDouble used by DoubleStream Spliterators.
*
* @param origin the least value, unless greater than bound
* @param bound the upper bound (exclusive), must not equal origin
* @return a pseudorandom value
*/
final double internalNextDouble(double origin, double bound) {
double r = (nextLong() >>> 11) * DOUBLE_UNIT;
if (origin < bound) {
r = r * (bound - origin) + origin;
if (r >= bound) // correct for rounding
r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
}
return r;
}
/* ---------------- public methods ---------------- */
/**
* Creates a new SplittableRandom instance using the specified
* initial seed. SplittableRandom instances created with the same
* seed in the same program generate identical sequences of values.
*
* @param seed the initial seed
*/
public SplittableRandom(long seed) {
this(seed, GOLDEN_GAMMA);
}
/**
* Creates a new SplittableRandom instance that is likely to
* generate sequences of values that are statistically independent
* of those of any other instances in the current program; and
* may, and typically does, vary across program invocations.
*/
public SplittableRandom() { // emulate defaultGen.split()
long s = defaultGen.getAndAdd(GOLDEN_GAMMA << 1);
this.seed = mix64(s);
this.gamma = mixGamma(s + GOLDEN_GAMMA);
}
/**
* Constructs and returns a new SplittableRandom instance that
* shares no mutable state with this instance. However, with very
* high probability, the set of values collectively generated by
* the two objects has the same statistical properties as if the
* same quantity of values were generated by a single thread using
* a single SplittableRandom object. Either or both of the two
* objects may be further split using the {@code split()} method,
* and the same expected statistical properties apply to the
* entire set of generators constructed by such recursive
* splitting.
*
* @return the new SplittableRandom instance
*/
public SplittableRandom split() {
return new SplittableRandom(nextLong(), mixGamma(nextSeed()));
}
/**
* Fills a user-supplied byte array with generated pseudorandom bytes.
*
* @param bytes the byte array to fill with pseudorandom bytes
* @throws NullPointerException if bytes is null
* @since 10
*/
public void nextBytes(byte[] bytes) {
int i = 0;
int len = bytes.length;
for (int words = len >> 3; words--> 0; ) {
long rnd = nextLong();
for (int n = 8; n--> 0; rnd >>>= Byte.SIZE)
bytes[i++] = (byte)rnd;
}
if (i < len)
for (long rnd = nextLong(); i < len; rnd >>>= Byte.SIZE)
bytes[i++] = (byte)rnd;
}
/**
* Returns a pseudorandom {@code int} value.
*
* @return a pseudorandom {@code int} value
*/
public int nextInt() {
return mix32(nextSeed());
}
/**
* Returns a pseudorandom {@code int} value between zero (inclusive)
* and the specified bound (exclusive).
*
* @param bound the upper bound (exclusive). Must be positive.
* @return a pseudorandom {@code int} value between zero
* (inclusive) and the bound (exclusive)
* @throws IllegalArgumentException if {@code bound} is not positive
*/
public int nextInt(int bound) {
if (bound <= 0)
throw new IllegalArgumentException(BAD_BOUND);
// Specialize internalNextInt for origin 0
int r = mix32(nextSeed());
int m = bound - 1;
if ((bound & m) == 0) // power of two
r &= m;
else { // reject over-represented candidates
for (int u = r >>> 1;
u + m - (r = u % bound) < 0;
u = mix32(nextSeed()) >>> 1)
;
}
return r;
}
/**
* Returns a pseudorandom {@code int} value between the specified
* origin (inclusive) and the specified bound (exclusive).
*
* @param origin the least value returned
* @param bound the upper bound (exclusive)
* @return a pseudorandom {@code int} value between the origin
* (inclusive) and the bound (exclusive)
* @throws IllegalArgumentException if {@code origin} is greater than
* or equal to {@code bound}
*/
public int nextInt(int origin, int bound) {
if (origin >= bound)
throw new IllegalArgumentException(BAD_RANGE);
return internalNextInt(origin, bound);
}
/**
* Returns a pseudorandom {@code long} value.
*
* @return a pseudorandom {@code long} value
*/
public long nextLong() {
return mix64(nextSeed());
}
/**
* Returns a pseudorandom {@code long} value between zero (inclusive)
* and the specified bound (exclusive).
*
* @param bound the upper bound (exclusive). Must be positive.
* @return a pseudorandom {@code long} value between zero
* (inclusive) and the bound (exclusive)
* @throws IllegalArgumentException if {@code bound} is not positive
*/
public long nextLong(long bound) {
if (bound <= 0)
throw new IllegalArgumentException(BAD_BOUND);
// Specialize internalNextLong for origin 0
long r = mix64(nextSeed());
long m = bound - 1;
if ((bound & m) == 0L) // power of two
r &= m;
else { // reject over-represented candidates
for (long u = r >>> 1;
u + m - (r = u % bound) < 0L;
u = mix64(nextSeed()) >>> 1)
;
}
return r;
}
/**
* Returns a pseudorandom {@code long} value between the specified
* origin (inclusive) and the specified bound (exclusive).
*
* @param origin the least value returned
* @param bound the upper bound (exclusive)
* @return a pseudorandom {@code long} value between the origin
* (inclusive) and the bound (exclusive)
* @throws IllegalArgumentException if {@code origin} is greater than
* or equal to {@code bound}
*/
public long nextLong(long origin, long bound) {
if (origin >= bound)
throw new IllegalArgumentException(BAD_RANGE);
return internalNextLong(origin, bound);
}
/**
* Returns a pseudorandom {@code double} value between zero
* (inclusive) and one (exclusive).
*
* @return a pseudorandom {@code double} value between zero
* (inclusive) and one (exclusive)
*/
public double nextDouble() {
return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT;
}
/**
* Returns a pseudorandom {@code double} value between 0.0
* (inclusive) and the specified bound (exclusive).
*
* @param bound the upper bound (exclusive). Must be positive.
* @return a pseudorandom {@code double} value between zero
* (inclusive) and the bound (exclusive)
* @throws IllegalArgumentException if {@code bound} is not positive
*/
public double nextDouble(double bound) {
if (!(bound > 0.0))
throw new IllegalArgumentException(BAD_BOUND);
double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound;
return (result < bound) ? result : // correct for rounding
Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
}
/**
* Returns a pseudorandom {@code double} value between the specified
* origin (inclusive) and bound (exclusive).
*
* @param origin the least value returned
* @param bound the upper bound (exclusive)
* @return a pseudorandom {@code double} value between the origin
* (inclusive) and the bound (exclusive)
* @throws IllegalArgumentException if {@code origin} is greater than
* or equal to {@code bound}
*/
public double nextDouble(double origin, double bound) {
if (!(origin < bound))
throw new IllegalArgumentException(BAD_RANGE);
return internalNextDouble(origin, bound);
}
/**
* Returns a pseudorandom {@code boolean} value.
*
* @return a pseudorandom {@code boolean} value
*/
public boolean nextBoolean() {
return mix32(nextSeed()) < 0;
}
// stream methods, coded in a way intended to better isolate for
// maintenance purposes the small differences across forms.
/**
* Returns a stream producing the given {@code streamSize} number
* of pseudorandom {@code int} values from this generator and/or
* one split from it.
*
* @param streamSize the number of values to generate
* @return a stream of pseudorandom {@code int} values
* @throws IllegalArgumentException if {@code streamSize} is
* less than zero
*/
public IntStream ints(long streamSize) {
if (streamSize < 0L)
throw new IllegalArgumentException(BAD_SIZE);
return StreamSupport.intStream
(new RandomIntsSpliterator
(this, 0L, streamSize, Integer.MAX_VALUE, 0),
false);
}
/**
* Returns an effectively unlimited stream of pseudorandom {@code int}
* values from this generator and/or one split from it.
*
* @implNote This method is implemented to be equivalent to {@code
* ints(Long.MAX_VALUE)}.
*
* @return a stream of pseudorandom {@code int} values
*/
public IntStream ints() {
return StreamSupport.intStream
(new RandomIntsSpliterator
(this, 0L, Long.MAX_VALUE, Integer.MAX_VALUE, 0),
false);
}
/**
* Returns a stream producing the given {@code streamSize} number
* of pseudorandom {@code int} values from this generator and/or one split
* from it; each value conforms to the given origin (inclusive) and bound
* (exclusive).
*
* @param streamSize the number of values to generate
* @param randomNumberOrigin the origin (inclusive) of each random value
* @param randomNumberBound the bound (exclusive) of each random value
* @return a stream of pseudorandom {@code int} values,
* each with the given origin (inclusive) and bound (exclusive)
* @throws IllegalArgumentException if {@code streamSize} is
* less than zero, or {@code randomNumberOrigin}
* is greater than or equal to {@code randomNumberBound}
*/
public IntStream ints(long streamSize, int randomNumberOrigin,
int randomNumberBound) {
if (streamSize < 0L)
throw new IllegalArgumentException(BAD_SIZE);
if (randomNumberOrigin >= randomNumberBound)
throw new IllegalArgumentException(BAD_RANGE);
return StreamSupport.intStream
(new RandomIntsSpliterator
(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
false);
}
/**
* Returns an effectively unlimited stream of pseudorandom {@code
* int} values from this generator and/or one split from it; each value
* conforms to the given origin (inclusive) and bound (exclusive).
*
* @implNote This method is implemented to be equivalent to {@code
* ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
*
* @param randomNumberOrigin the origin (inclusive) of each random value
* @param randomNumberBound the bound (exclusive) of each random value
* @return a stream of pseudorandom {@code int} values,
* each with the given origin (inclusive) and bound (exclusive)
* @throws IllegalArgumentException if {@code randomNumberOrigin}
* is greater than or equal to {@code randomNumberBound}
*/
public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
if (randomNumberOrigin >= randomNumberBound)
throw new IllegalArgumentException(BAD_RANGE);
return StreamSupport.intStream
(new RandomIntsSpliterator
(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
false);
}
/**
* Returns a stream producing the given {@code streamSize} number
* of pseudorandom {@code long} values from this generator and/or
* one split from it.
*
* @param streamSize the number of values to generate
* @return a stream of pseudorandom {@code long} values
* @throws IllegalArgumentException if {@code streamSize} is
* less than zero
*/
public LongStream longs(long streamSize) {
if (streamSize < 0L)
throw new IllegalArgumentException(BAD_SIZE);
return StreamSupport.longStream
(new RandomLongsSpliterator
(this, 0L, streamSize, Long.MAX_VALUE, 0L),
false);
}
/**
* Returns an effectively unlimited stream of pseudorandom {@code
* long} values from this generator and/or one split from it.
*
* @implNote This method is implemented to be equivalent to {@code
* longs(Long.MAX_VALUE)}.
*
* @return a stream of pseudorandom {@code long} values
*/
public LongStream longs() {
return StreamSupport.longStream
(new RandomLongsSpliterator
(this, 0L, Long.MAX_VALUE, Long.MAX_VALUE, 0L),
false);
}
/**
* Returns a stream producing the given {@code streamSize} number of
* pseudorandom {@code long} values from this generator and/or one split
* from it; each value conforms to the given origin (inclusive) and bound
* (exclusive).
*
* @param streamSize the number of values to generate
* @param randomNumberOrigin the origin (inclusive) of each random value
* @param randomNumberBound the bound (exclusive) of each random value
* @return a stream of pseudorandom {@code long} values,
* each with the given origin (inclusive) and bound (exclusive)
* @throws IllegalArgumentException if {@code streamSize} is
* less than zero, or {@code randomNumberOrigin}
* is greater than or equal to {@code randomNumberBound}
*/
public LongStream longs(long streamSize, long randomNumberOrigin,
long randomNumberBound) {
if (streamSize < 0L)
throw new IllegalArgumentException(BAD_SIZE);
if (randomNumberOrigin >= randomNumberBound)
throw new IllegalArgumentException(BAD_RANGE);
return StreamSupport.longStream
(new RandomLongsSpliterator
(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
false);
}
/**
* Returns an effectively unlimited stream of pseudorandom {@code
* long} values from this generator and/or one split from it; each value
* conforms to the given origin (inclusive) and bound (exclusive).
*
* @implNote This method is implemented to be equivalent to {@code
* longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
*
* @param randomNumberOrigin the origin (inclusive) of each random value
* @param randomNumberBound the bound (exclusive) of each random value
* @return a stream of pseudorandom {@code long} values,
* each with the given origin (inclusive) and bound (exclusive)
* @throws IllegalArgumentException if {@code randomNumberOrigin}
* is greater than or equal to {@code randomNumberBound}
*/
public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
if (randomNumberOrigin >= randomNumberBound)
throw new IllegalArgumentException(BAD_RANGE);
return StreamSupport.longStream
(new RandomLongsSpliterator
(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
false);
}
/**
* Returns a stream producing the given {@code streamSize} number of
* pseudorandom {@code double} values from this generator and/or one split
* from it; each value is between zero (inclusive) and one (exclusive).
*
* @param streamSize the number of values to generate
* @return a stream of {@code double} values
* @throws IllegalArgumentException if {@code streamSize} is
* less than zero
*/
public DoubleStream doubles(long streamSize) {
if (streamSize < 0L)
throw new IllegalArgumentException(BAD_SIZE);
return StreamSupport.doubleStream
(new RandomDoublesSpliterator
(this, 0L, streamSize, Double.MAX_VALUE, 0.0),
false);
}
/**
* Returns an effectively unlimited stream of pseudorandom {@code
* double} values from this generator and/or one split from it; each value
* is between zero (inclusive) and one (exclusive).
*
* @implNote This method is implemented to be equivalent to {@code
* doubles(Long.MAX_VALUE)}.
*
* @return a stream of pseudorandom {@code double} values
*/
public DoubleStream doubles() {
return StreamSupport.doubleStream
(new RandomDoublesSpliterator
(this, 0L, Long.MAX_VALUE, Double.MAX_VALUE, 0.0),
false);
}
/**
* Returns a stream producing the given {@code streamSize} number of
* pseudorandom {@code double} values from this generator and/or one split
* from it; each value conforms to the given origin (inclusive) and bound
* (exclusive).
*
* @param streamSize the number of values to generate
* @param randomNumberOrigin the origin (inclusive) of each random value
* @param randomNumberBound the bound (exclusive) of each random value
* @return a stream of pseudorandom {@code double} values,
* each with the given origin (inclusive) and bound (exclusive)
* @throws IllegalArgumentException if {@code streamSize} is
* less than zero, or {@code randomNumberOrigin}
* is greater than or equal to {@code randomNumberBound}
*/
public DoubleStream doubles(long streamSize, double randomNumberOrigin,
double randomNumberBound) {
if (streamSize < 0L)
throw new IllegalArgumentException(BAD_SIZE);
if (!(randomNumberOrigin < randomNumberBound))
throw new IllegalArgumentException(BAD_RANGE);
return StreamSupport.doubleStream
(new RandomDoublesSpliterator
(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
false);
}
/**
* Returns an effectively unlimited stream of pseudorandom {@code
* double} values from this generator and/or one split from it; each value
* conforms to the given origin (inclusive) and bound (exclusive).
*
* @implNote This method is implemented to be equivalent to {@code
* doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
*
* @param randomNumberOrigin the origin (inclusive) of each random value
* @param randomNumberBound the bound (exclusive) of each random value
* @return a stream of pseudorandom {@code double} values,
* each with the given origin (inclusive) and bound (exclusive)
* @throws IllegalArgumentException if {@code randomNumberOrigin}
* is greater than or equal to {@code randomNumberBound}
*/
public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
if (!(randomNumberOrigin < randomNumberBound))
throw new IllegalArgumentException(BAD_RANGE);
return StreamSupport.doubleStream
(new RandomDoublesSpliterator
(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
false);
}
/**
* Spliterator for int streams. We multiplex the four int
* versions into one class by treating a bound less than origin as
* unbounded, and also by treating "infinite" as equivalent to
* Long.MAX_VALUE. For splits, it uses the standard divide-by-two
* approach. The long and double versions of this class are
* identical except for types.
*/
private static final class RandomIntsSpliterator
implements Spliterator.OfInt {
final SplittableRandom rng;
long index;
final long fence;
final int origin;
final int bound;
RandomIntsSpliterator(SplittableRandom rng, long index, long fence,
int origin, int bound) {
this.rng = rng; this.index = index; this.fence = fence;
this.origin = origin; this.bound = bound;
}
public RandomIntsSpliterator trySplit() {
long i = index, m = (i + fence) >>> 1;
return (m <= i) ? null :
new RandomIntsSpliterator(rng.split(), i, index = m, origin, bound);
}
public long estimateSize() {
return fence - index;
}
public int characteristics() {
return (Spliterator.SIZED | Spliterator.SUBSIZED |
Spliterator.NONNULL | Spliterator.IMMUTABLE);
}
public boolean tryAdvance(IntConsumer consumer) {
if (consumer == null) throw new NullPointerException();
long i = index, f = fence;
if (i < f) {
consumer.accept(rng.internalNextInt(origin, bound));
index = i + 1;
return true;
}
return false;
}
public void forEachRemaining(IntConsumer consumer) {
if (consumer == null) throw new NullPointerException();
long i = index, f = fence;
if (i < f) {
index = f;
SplittableRandom r = rng;
int o = origin, b = bound;
do {
consumer.accept(r.internalNextInt(o, b));
} while (++i < f);
}
}
}
/**
* Spliterator for long streams.
*/
private static final class RandomLongsSpliterator
implements Spliterator.OfLong {
final SplittableRandom rng;
long index;
final long fence;
final long origin;
final long bound;
RandomLongsSpliterator(SplittableRandom rng, long index, long fence,
long origin, long bound) {
this.rng = rng; this.index = index; this.fence = fence;
this.origin = origin; this.bound = bound;
}
public RandomLongsSpliterator trySplit() {
long i = index, m = (i + fence) >>> 1;
return (m <= i) ? null :
new RandomLongsSpliterator(rng.split(), i, index = m, origin, bound);
}
public long estimateSize() {
return fence - index;
}
public int characteristics() {
return (Spliterator.SIZED | Spliterator.SUBSIZED |
Spliterator.NONNULL | Spliterator.IMMUTABLE);
}
public boolean tryAdvance(LongConsumer consumer) {
if (consumer == null) throw new NullPointerException();
long i = index, f = fence;
if (i < f) {
consumer.accept(rng.internalNextLong(origin, bound));
index = i + 1;
return true;
}
return false;
}
public void forEachRemaining(LongConsumer consumer) {
if (consumer == null) throw new NullPointerException();
long i = index, f = fence;
if (i < f) {
index = f;
SplittableRandom r = rng;
long o = origin, b = bound;
do {
consumer.accept(r.internalNextLong(o, b));
} while (++i < f);
}
}
}
/**
* Spliterator for double streams.
*/
private static final class RandomDoublesSpliterator
implements Spliterator.OfDouble {
final SplittableRandom rng;
long index;
final long fence;
final double origin;
final double bound;
RandomDoublesSpliterator(SplittableRandom rng, long index, long fence,
double origin, double bound) {
this.rng = rng; this.index = index; this.fence = fence;
this.origin = origin; this.bound = bound;
}
public RandomDoublesSpliterator trySplit() {
long i = index, m = (i + fence) >>> 1;
return (m <= i) ? null :
new RandomDoublesSpliterator(rng.split(), i, index = m, origin, bound);
}
public long estimateSize() {
return fence - index;
}
public int characteristics() {
return (Spliterator.SIZED | Spliterator.SUBSIZED |
Spliterator.NONNULL | Spliterator.IMMUTABLE);
}
public boolean tryAdvance(DoubleConsumer consumer) {
if (consumer == null) throw new NullPointerException();
long i = index, f = fence;
if (i < f) {
consumer.accept(rng.internalNextDouble(origin, bound));
index = i + 1;
return true;
}
return false;
}
public void forEachRemaining(DoubleConsumer consumer) {
if (consumer == null) throw new NullPointerException();
long i = index, f = fence;
if (i < f) {
index = f;
SplittableRandom r = rng;
double o = origin, b = bound;
do {
consumer.accept(r.internalNextDouble(o, b));
} while (++i < f);
}
}
}
}
⏎ java/util/SplittableRandom.java
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File name: java.base-11.0.1-src.zip File size: 8740354 bytes Release date: 2018-11-04 Download
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