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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
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* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
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*
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* accompanied this code).
*
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package java.util;
import java.util.concurrent.atomic.AtomicLong;
import java.util.Spliterator;
import java.util.function.IntConsumer;
import java.util.function.LongConsumer;
import java.util.function.DoubleConsumer;
import java.util.stream.StreamSupport;
import java.util.stream.IntStream;
import java.util.stream.LongStream;
import java.util.stream.DoubleStream;
/**
* A generator of uniform pseudorandom values applicable for use in
* (among other contexts) isolated parallel computations that may
* generate subtasks. Class 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:
*
*
*
* - Series of generated values pass the DieHarder suite testing
* independence and uniformity properties of random number generators.
* (Most recently validated with version
* 3.31.1.) 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.
*
* - 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.
*
* - Instances of SplittableRandom are not 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()}.
*
*
- This class provides additional methods for generating random
* streams, that employ the above techniques when used in {@code
* stream.parallel()} mode.
*
*
*
* @author Guy Steele
* @author Doug Lea
* @since 1.8
*/
public class SplittableRandom {
/*
* 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.
*
* Credits: Primary algorithm and code by Guy Steele. Stream
* support methods by Doug Lea. Documentation jointly produced
* with additional help from Brian Goetz.
*/
/*
* 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, but improves and extends it in several ways.
*
* The primary update step (see method nextSeed()) is simply to
* add a constant ("gamma") to the current seed, modulo a prime
* ("George"). However, the nextLong and nextInt methods do not
* return this value, but instead the results of bit-mixing
* transformations that produce more uniformly distributed
* sequences.
*
* "George" is the otherwise nameless (because it cannot be
* represented) prime number 2^64+13. Using a prime number larger
* than can fit in a long ensures that all possible long values
* can occur, plus 13 others that just get skipped over when they
* are encountered; see method addGammaModGeorge. For this to
* work, initial gamma values must be at least 13.
*
* The value of gamma differs for each instance across a series of
* splits, and is generated using a slightly stripped-down variant
* of the same algorithm, but operating across calls to split(),
* not calls to nextSeed(): Each instance carries the state of
* this generator as nextSplit, and uses mix64(nextSplit) as its
* own gamma value. Computations of gammas themselves use a fixed
* constant as the second argument to the addGammaModGeorge
* function, GAMMA_GAMMA, a "genuinely random" number from a
* radioactive decay reading (obtained from
* http://www.fourmilab.ch/hotbits/) meeting the above range
* constraint. Using a fixed constant maintains the invariant that
* the value of gamma is the same for every instance that is at
* the same split-distance from their common root. (Note: there is
* nothing especially magic about obtaining this constant from a
* "truly random" physical source rather than just choosing one
* arbitrarily; using "hotbits" was merely an aesthetically pleasing
* choice. In either case, good statistical behavior of the
* algorithm should be, and was, verified by using the DieHarder
* test suite.)
*
* The mix64 bit-mixing function called by nextLong and other
* methods computes the same value as the "64-bit finalizer"
* function in Austin Appleby's MurmurHash3 algorithm. See
* http://code.google.com/p/smhasher/wiki/MurmurHash3 , which
* comments: "The constants for the finalizers were generated by a
* simple simulated-annealing algorithm, and both avalanche all
* bits of 'h' to within 0.25% bias." It also appears to work to
* use instead any of the variants proposed by David Stafford at
* http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html
* but these variants have not yet been tested as thoroughly
* in the context of the implementation of SplittableRandom.
*
* The mix32 function used for nextInt just consists of two of the
* five lines of mix64; avalanche testing shows that the 64-bit result
* has its top 32 bits avalanched well, though not the bottom 32 bits.
* DieHarder tests show that it is adequate for generating one
* random int from the 64-bit result of nextSeed.
*
* Support for the default (no-argument) constructor relies on an
* AtomicLong (defaultSeedGenerator) to help perform the
* equivalent of a split of a statically constructed
* SplittableRandom. Unlike other cases, this split must be
* performed in a thread-safe manner. We use
* AtomicLong.compareAndSet as the (typically) most efficient
* mechanism. To bootstrap, we start off using System.nanotime(),
* and update using another "genuinely random" constant
* DEFAULT_SEED_GAMMA. The default constructor uses GAMMA_GAMMA,
* not 0, for its splitSeed argument (addGammaModGeorge(0,
* GAMMA_GAMMA) == GAMMA_GAMMA) to reflect that each is split from
* this root generator, even though the root is not explicitly
* represented as a SplittableRandom.
*/
/**
* The "genuinely random" value for producing new gamma values.
* The value is arbitrary, subject to the requirement that it be
* greater or equal to 13.
*/
private static final long GAMMA_GAMMA = 0xF2281E2DBA6606F3L;
/**
* The "genuinely random" seed update value for default constructors.
* The value is arbitrary, subject to the requirement that it be
* greater or equal to 13.
*/
private static final long DEFAULT_SEED_GAMMA = 0xBD24B73A95FB84D9L;
/**
* 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 = 1.0 / (1L << 53);
/**
* The next seed for default constructors.
*/
private static final AtomicLong defaultSeedGenerator =
new AtomicLong(System.nanoTime());
/**
* The seed, updated only via method nextSeed.
*/
private long seed;
/**
* The constant value added to seed (mod George) on each update.
*/
private final long gamma;
/**
* The next seed to use for splits. Propagated using
* addGammaModGeorge across instances.
*/
private final long nextSplit;
/**
* Adds the given gamma value, g, to the given seed value s, mod
* George (2^64+13). We regard s and g as unsigned values
* (ranging from 0 to 2^64-1). We add g to s either once or twice
* (mod George) as necessary to produce an (unsigned) result less
* than 2^64. We require that g must be at least 13. This
* guarantees that if (s+g) mod George >= 2^64 then (s+g+g) mod
* George < 2^64; thus we need only a conditional, not a loop,
* to be sure of getting a representable value.
*
* @param s a seed value
* @param g a gamma value, 13 <= g (as unsigned)
*/
private static long addGammaModGeorge(long s, long g) {
long p = s + g;
if (Long.compareUnsigned(p, g) >= 0)
return p;
long q = p - 13L;
return (Long.compareUnsigned(p, 13L) >= 0) ? q : (q + g);
}
/**
* Returns a bit-mixed transformation of its argument.
* See above for explanation.
*/
private static long mix64(long z) {
z ^= (z >>> 33);
z *= 0xff51afd7ed558ccdL;
z ^= (z >>> 33);
z *= 0xc4ceb9fe1a85ec53L;
z ^= (z >>> 33);
return z;
}
/**
* Returns a bit-mixed int transformation of its argument.
* See above for explanation.
*/
private static int mix32(long z) {
z ^= (z >>> 33);
z *= 0xc4ceb9fe1a85ec53L;
return (int)(z >>> 32);
}
/**
* Internal constructor used by all other constructors and by
* method split. Establishes the initial seed for this instance,
* and uses the given splitSeed to establish gamma, as well as the
* nextSplit to use by this instance. The loop to skip ineligible
* gammas very rarely iterates, and does so at most 13 times.
*/
private SplittableRandom(long seed, long splitSeed) {
this.seed = seed;
long s = splitSeed, g;
do { // ensure gamma >= 13, considered as an unsigned integer
s = addGammaModGeorge(s, GAMMA_GAMMA);
g = mix64(s);
} while (Long.compareUnsigned(g, 13L) < 0);
this.gamma = g;
this.nextSplit = s;
}
/**
* Updates in-place and returns seed.
* See above for explanation.
*/
private long nextSeed() {
return seed = addGammaModGeorge(seed, gamma);
}
/**
* Atomically updates and returns next seed for default constructor.
*/
private static long nextDefaultSeed() {
long oldSeed, newSeed;
do {
oldSeed = defaultSeedGenerator.get();
newSeed = addGammaModGeorge(oldSeed, DEFAULT_SEED_GAMMA);
} while (!defaultSeedGenerator.compareAndSet(oldSeed, newSeed));
return mix64(newSeed);
}
/*
* 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 (264) 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) == 0L)
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 generate identical sequences of values.
*
* @param seed the initial seed
*/
public SplittableRandom(long seed) {
this(seed, 0);
}
/**
* 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() {
this(nextDefaultSeed(), GAMMA_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(nextSeed(), nextSplit);
}
/**
* 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 bound on the random number to be returned. Must be
* positive.
* @return a pseudorandom {@code int} value between zero
* (inclusive) and the bound (exclusive).
* @throws IllegalArgumentException if the bound is less than zero
*/
public int nextInt(int bound) {
if (bound <= 0)
throw new IllegalArgumentException("bound must be positive");
// Specialize internalNextInt for origin 0
int r = mix32(nextSeed());
int m = bound - 1;
if ((bound & m) == 0L) // 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("bound must be greater than origin");
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 bound on the random number to be returned. Must be
* positive.
* @return a pseudorandom {@code long} value between zero
* (inclusive) and the bound (exclusive).
* @throws IllegalArgumentException if {@code bound} is less than zero
*/
public long nextLong(long bound) {
if (bound <= 0)
throw new IllegalArgumentException("bound must be positive");
// 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("bound must be greater than origin");
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 (nextLong() >>> 11) * DOUBLE_UNIT;
}
/**
* Returns a pseudorandom {@code double} value between 0.0
* (inclusive) and the specified bound (exclusive).
*
* @param bound the bound on the random number to be returned. Must be
* positive.
* @return a pseudorandom {@code double} value between zero
* (inclusive) and the bound (exclusive).
* @throws IllegalArgumentException if {@code bound} is less than zero
*/
public double nextDouble(double bound) {
if (!(bound > 0.0))
throw new IllegalArgumentException("bound must be positive");
double result = nextDouble() * 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
* @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("bound must be greater than origin");
return internalNextDouble(origin, bound);
}
// 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.
*
* @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("negative Stream size");
return StreamSupport.intStream
(new RandomIntsSpliterator
(this, 0L, streamSize, Integer.MAX_VALUE, 0),
false);
}
/**
* Returns an effectively unlimited stream of pseudorandom {@code int}
* values
*
* @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, each conforming to the given
* origin and bound.
*
* @param streamSize the number of values to generate
* @param randomNumberOrigin the origin of each random value
* @param randomNumberBound the bound of each random value
* @return a stream of pseudorandom {@code int} values,
* each with the given origin and bound.
* @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("negative Stream size");
if (randomNumberOrigin >= randomNumberBound)
throw new IllegalArgumentException("bound must be greater than origin");
return StreamSupport.intStream
(new RandomIntsSpliterator
(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
false);
}
/**
* Returns an effectively unlimited stream of pseudorandom {@code
* int} values, each conforming to the given origin and bound.
*
* @implNote This method is implemented to be equivalent to {@code
* ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
*
* @param randomNumberOrigin the origin of each random value
* @param randomNumberBound the bound of each random value
* @return a stream of pseudorandom {@code int} values,
* each with the given origin and bound.
* @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("bound must be greater than origin");
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.
*
* @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("negative Stream size");
return StreamSupport.longStream
(new RandomLongsSpliterator
(this, 0L, streamSize, Long.MAX_VALUE, 0L),
false);
}
/**
* Returns an effectively unlimited stream of pseudorandom {@code long}
* values.
*
* @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, each conforming to the
* given origin and bound.
*
* @param streamSize the number of values to generate
* @param randomNumberOrigin the origin of each random value
* @param randomNumberBound the bound of each random value
* @return a stream of pseudorandom {@code long} values,
* each with the given origin and bound.
* @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("negative Stream size");
if (randomNumberOrigin >= randomNumberBound)
throw new IllegalArgumentException("bound must be greater than origin");
return StreamSupport.longStream
(new RandomLongsSpliterator
(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
false);
}
/**
* Returns an effectively unlimited stream of pseudorandom {@code
* long} values, each conforming to the given origin and bound.
*
* @implNote This method is implemented to be equivalent to {@code
* longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
*
* @param randomNumberOrigin the origin of each random value
* @param randomNumberBound the bound of each random value
* @return a stream of pseudorandom {@code long} values,
* each with the given origin and bound.
* @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("bound must be greater than origin");
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, each 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("negative Stream 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, each 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, each conforming to the
* given origin and bound.
*
* @param streamSize the number of values to generate
* @param randomNumberOrigin the origin of each random value
* @param randomNumberBound the bound of each random value
* @return a stream of pseudorandom {@code double} values,
* each with the given origin and bound.
* @throws IllegalArgumentException if {@code streamSize} is
* less than zero.
* @throws IllegalArgumentException if {@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("negative Stream size");
if (!(randomNumberOrigin < randomNumberBound))
throw new IllegalArgumentException("bound must be greater than origin");
return StreamSupport.doubleStream
(new RandomDoublesSpliterator
(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
false);
}
/**
* Returns an effectively unlimited stream of pseudorandom {@code
* double} values, each conforming to the given origin and bound.
*
* @implNote This method is implemented to be equivalent to {@code
* doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
*
* @param randomNumberOrigin the origin of each random value
* @param randomNumberBound the bound of each random value
* @return a stream of pseudorandom {@code double} values,
* each with the given origin and bound.
* @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("bound must be greater than origin");
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.
*/
static 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;
int o = origin, b = bound;
do {
consumer.accept(rng.internalNextInt(o, b));
} while (++i < f);
}
}
}
/**
* Spliterator for long streams.
*/
static 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;
long o = origin, b = bound;
do {
consumer.accept(rng.internalNextLong(o, b));
} while (++i < f);
}
}
}
/**
* Spliterator for double streams.
*/
static 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;
double o = origin, b = bound;
do {
consumer.accept(rng.internalNextDouble(o, b));
} while (++i < f);
}
}
}
}