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Comparing jsr166/src/main/java/util/SplittableRandom.java (file contents):
Revision 1.10 by jsr166, Sun Jul 14 08:06:49 2013 UTC vs.
Revision 1.41 by jsr166, Sun Dec 2 23:06:16 2018 UTC

#	Line 26 | Line 26
26		package java.util;
27
28		import java.util.concurrent.atomic.AtomicLong;
29	<	import java.util.Spliterator;
29	>	import java.util.function.DoubleConsumer;
30		import java.util.function.IntConsumer;
31		import java.util.function.LongConsumer;
32	<	import java.util.function.DoubleConsumer;
33	<	import java.util.stream.StreamSupport;
32	>	import java.util.stream.DoubleStream;
33		import java.util.stream.IntStream;
34		import java.util.stream.LongStream;
35	<	import java.util.stream.DoubleStream;
35	>	import java.util.stream.StreamSupport;
36
37		/**
38		* A generator of uniform pseudorandom values applicable for use in
39		* (among other contexts) isolated parallel computations that may
40	<	* generate subtasks. Class SplittableRandom supports methods for
40	>	* generate subtasks. Class {@code SplittableRandom} supports methods for
41		* producing pseudorandom numbers of type {@code int}, {@code long},
42		* and {@code double} with similar usages as for class
43		* {@link java.util.Random} but differs in the following ways:
#	Line 51 | Line 50 | import java.util.stream.DoubleStream;
50		* href="http://www.phy.duke.edu/~rgb/General/dieharder.php"> version
51		* 3.31.1</a>.) These tests validate only the methods for certain
52		* types and ranges, but similar properties are expected to hold, at
53	<	* least approximately, for others as well.  </li>
53	>	* least approximately, for others as well. The <em>period</em>
54	>	* (length of any series of generated values before it repeats) is at
55	>	* least 2<sup>64</sup>.
56		*
57	<	* <li> Method {@link #split} constructs and returns a new
57	>	* <li>Method {@link #split} constructs and returns a new
58		* SplittableRandom instance that shares no mutable state with the
59		* current instance. However, with very high probability, the
60		* values collectively generated by the two objects have the same
61		* statistical properties as if the same quantity of values were
62		* generated by a single thread using a single {@code
63	<	* SplittableRandom} object.  </li>
63	>	* SplittableRandom} object.
64		*
65		* <li>Instances of SplittableRandom are <em>not</em> thread-safe.
66		* They are designed to be split, not shared, across threads. For
#	Line 70 | Line 71 | import java.util.stream.DoubleStream;
71		*
72		* <li>This class provides additional methods for generating random
73		* streams, that employ the above techniques when used in {@code
74	<	* stream.parallel()} mode.</li>
74	>	* stream.parallel()} mode.
75		*
76		* </ul>
77		*
78	+	* <p>Instances of {@code SplittableRandom} are not cryptographically
79	+	* secure.  Consider instead using {@link java.security.SecureRandom}
80	+	* in security-sensitive applications. Additionally,
81	+	* default-constructed instances do not use a cryptographically random
82	+	* seed unless the {@linkplain System#getProperty system property}
83	+	* {@systemProperty java.util.secureRandomSeed} is set to {@code true}.
84	+	*
85		* @author  Guy Steele
86		* @author  Doug Lea
87		* @since   1.8
88		*/
89	<	public class SplittableRandom {
82	<
83	<	/*
84	<	* File organization: First the non-public methods that constitute
85	<	* the main algorithm, then the main public methods, followed by
86	<	* some custom spliterator classes needed for stream methods.
87	<	*
88	<	* Credits: Primary algorithm and code by Guy Steele.  Stream
89	<	* support methods by Doug Lea.  Documentation jointly produced
90	<	* with additional help from Brian Goetz.
91	<	*/
89	>	public final class SplittableRandom {
90
91		/*
92		* Implementation Overview.
#	Line 96 | Line 94 | public class SplittableRandom {
94		* This algorithm was inspired by the "DotMix" algorithm by
95		* Leiserson, Schardl, and Sukha "Deterministic Parallel
96		* Random-Number Generation for Dynamic-Multithreading Platforms",
97	<	* PPoPP 2012, but improves and extends it in several ways.
97	>	* PPoPP 2012, as well as those in "Parallel random numbers: as
98	>	* easy as 1, 2, 3" by Salmon, Morae, Dror, and Shaw, SC 2011.  It
99	>	* differs mainly in simplifying and cheapening operations.
100	>	*
101	>	* The primary update step (method nextSeed()) is to add a
102	>	* constant ("gamma") to the current (64 bit) seed, forming a
103	>	* simple sequence.  The seed and the gamma values for any two
104	>	* SplittableRandom instances are highly likely to be different.
105	>	*
106	>	* Methods nextLong, nextInt, and derivatives do not return the
107	>	* sequence (seed) values, but instead a hash-like bit-mix of
108	>	* their bits, producing more independently distributed sequences.
109	>	* For nextLong, the mix64 function is based on David Stafford's
110	>	* (http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html)
111	>	* "Mix13" variant of the "64-bit finalizer" function in Austin
112	>	* Appleby's MurmurHash3 algorithm (see
113	>	* http://code.google.com/p/smhasher/wiki/MurmurHash3). The mix32
114	>	* function is based on Stafford's Mix04 mix function, but returns
115	>	* the upper 32 bits cast as int.
116	>	*
117	>	* The split operation uses the current generator to form the seed
118	>	* and gamma for another SplittableRandom.  To conservatively
119	>	* avoid potential correlations between seed and value generation,
120	>	* gamma selection (method mixGamma) uses different
121	>	* (Murmurhash3's) mix constants.  To avoid potential weaknesses
122	>	* in bit-mixing transformations, we restrict gammas to odd values
123	>	* with at least 24 0-1 or 1-0 bit transitions.  Rather than
124	>	* rejecting candidates with too few or too many bits set, method
125	>	* mixGamma flips some bits (which has the effect of mapping at
126	>	* most 4 to any given gamma value).  This reduces the effective
127	>	* set of 64bit odd gamma values by about 2%, and serves as an
128	>	* automated screening for sequence constant selection that is
129	>	* left as an empirical decision in some other hashing and crypto
130	>	* algorithms.
131	>	*
132	>	* The resulting generator thus transforms a sequence in which
133	>	* (typically) many bits change on each step, with an inexpensive
134	>	* mixer with good (but less than cryptographically secure)
135	>	* avalanching.
136	>	*
137	>	* The default (no-argument) constructor, in essence, invokes
138	>	* split() for a common "defaultGen" SplittableRandom.  Unlike
139	>	* other cases, this split must be performed in a thread-safe
140	>	* manner, so we use an AtomicLong to represent the seed rather
141	>	* than use an explicit SplittableRandom. To bootstrap the
142	>	* defaultGen, we start off using a seed based on current time
143	>	* unless the java.util.secureRandomSeed property is set. This
144	>	* serves as a slimmed-down (and insecure) variant of SecureRandom
145	>	* that also avoids stalls that may occur when using /dev/random.
146	>	*
147	>	* It is a relatively simple matter to apply the basic design here
148	>	* to use 128 bit seeds. However, emulating 128bit arithmetic and
149	>	* carrying around twice the state add more overhead than appears
150	>	* warranted for current usages.
151		*
152	<	* The primary update step (see method nextSeed()) is simply to
153	<	* add a constant ("gamma") to the current seed, modulo a prime
154	<	* ("George"). However, the nextLong and nextInt methods do not
104	<	* return this value, but instead the results of bit-mixing
105	<	* transformations that produce more uniformly distributed
106	<	* sequences.
107	<	*
108	<	* "George" is the otherwise nameless (because it cannot be
109	<	* represented) prime number 2^64+13. Using a prime number larger
110	<	* than can fit in a long ensures that all possible long values
111	<	* can occur, plus 13 others that just get skipped over when they
112	<	* are encountered; see method addGammaModGeorge. For this to
113	<	* work, initial gamma values must be at least 13.
114	<	*
115	<	* The value of gamma differs for each instance across a series of
116	<	* splits, and is generated using a slightly stripped-down variant
117	<	* of the same algorithm, but operating across calls to split(),
118	<	* not calls to nextSeed(): Each instance carries the state of
119	<	* this generator as nextSplit, and uses mix64(nextSplit) as its
120	<	* own gamma value. Computations of gammas themselves use a fixed
121	<	* constant as the second argument to the addGammaModGeorge
122	<	* function, GAMMA_GAMMA, a "genuinely random" number from a
123	<	* radioactive decay reading (obtained from
124	<	* http://www.fourmilab.ch/hotbits/) meeting the above range
125	<	* constraint. Using a fixed constant maintains the invariant that
126	<	* the value of gamma is the same for every instance that is at
127	<	* the same split-distance from their common root. (Note: there is
128	<	* nothing especially magic about obtaining this constant from a
129	<	* "truly random" physical source rather than just choosing one
130	<	* arbitrarily; using "hotbits" was merely an aesthetically pleasing
131	<	* choice.  In either case, good statistical behavior of the
132	<	* algorithm should be, and was, verified by using the DieHarder
133	<	* test suite.)
134	<	*
135	<	* The mix64 bit-mixing function called by nextLong and other
136	<	* methods computes the same value as the "64-bit finalizer"
137	<	* function in Austin Appleby's MurmurHash3 algorithm.  See
138	<	* http://code.google.com/p/smhasher/wiki/MurmurHash3 , which
139	<	* comments: "The constants for the finalizers were generated by a
140	<	* simple simulated-annealing algorithm, and both avalanche all
141	<	* bits of 'h' to within 0.25% bias." It also appears to work to
142	<	* use instead any of the variants proposed by David Stafford at
143	<	* http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html
144	<	* but these variants have not yet been tested as thoroughly
145	<	* in the context of the implementation of SplittableRandom.
146	<	*
147	<	* The mix32 function used for nextInt just consists of two of the
148	<	* five lines of mix64; avalanche testing shows that the 64-bit result
149	<	* has its top 32 bits avalanched well, though not the bottom 32 bits.
150	<	* DieHarder tests show that it is adequate for generating one
151	<	* random int from the 64-bit result of nextSeed.
152	<	*
153	<	* Support for the default (no-argument) constructor relies on an
154	<	* AtomicLong (defaultSeedGenerator) to help perform the
155	<	* equivalent of a split of a statically constructed
156	<	* SplittableRandom. Unlike other cases, this split must be
157	<	* performed in a thread-safe manner. We use
158	<	* AtomicLong.compareAndSet as the (typically) most efficient
159	<	* mechanism. To bootstrap, we start off using System.nanotime(),
160	<	* and update using another "genuinely random" constant
161	<	* DEFAULT_SEED_GAMMA. The default constructor uses GAMMA_GAMMA,
162	<	* not 0, for its splitSeed argument (addGammaModGeorge(0,
163	<	* GAMMA_GAMMA) == GAMMA_GAMMA) to reflect that each is split from
164	<	* this root generator, even though the root is not explicitly
165	<	* represented as a SplittableRandom.
166	<	*/
167	<
168	<	/**
169	<	* The "genuinely random" value for producing new gamma values.
170	<	* The value is arbitrary, subject to the requirement that it be
171	<	* greater or equal to 13.
172	<	*/
173	<	private static final long GAMMA_GAMMA = 0xF2281E2DBA6606F3L;
174	<
175	<	/**
176	<	* The "genuinely random" seed update value for default constructors.
177	<	* The value is arbitrary, subject to the requirement that it be
178	<	* greater or equal to 13.
152	>	* File organization: First the non-public methods that constitute
153	>	* the main algorithm, then the main public methods, followed by
154	>	* some custom spliterator classes needed for stream methods.
155		*/
180	–	private static final long DEFAULT_SEED_GAMMA = 0xBD24B73A95FB84D9L;
156
157		/**
158	<	* The least non-zero value returned by nextDouble(). This value
159	<	* is scaled by a random value of 53 bits to produce a result.
158	>	* The golden ratio scaled to 64bits, used as the initial gamma
159	>	* value for (unsplit) SplittableRandoms.
160		*/
161	<	private static final double DOUBLE_UNIT = 1.0 / (1L << 53);
161	>	private static final long GOLDEN_GAMMA = 0x9e3779b97f4a7c15L;
162
163		/**
164	<	* The next seed for default constructors.
164	>	* The least non-zero value returned by nextDouble(). This value
165	>	* is scaled by a random value of 53 bits to produce a result.
166		*/
167	<	private static final AtomicLong defaultSeedGenerator =
192	<	new AtomicLong(System.nanoTime());
167	>	private static final double DOUBLE_UNIT = 0x1.0p-53; // 1.0 / (1L << 53);
168
169		/**
170	<	* The seed, updated only via method nextSeed.
170	>	* The seed. Updated only via method nextSeed.
171		*/
172		private long seed;
173
174		/**
175	<	* The constant value added to seed (mod George) on each update.
175	>	* The step value.
176		*/
177		private final long gamma;
178
179		/**
180	<	* The next seed to use for splits. Propagated using
206	<	* addGammaModGeorge across instances.
180	>	* Internal constructor used by all others except default constructor.
181		*/
182	<	private final long nextSplit;
183	<
184	<	/**
211	<	* Adds the given gamma value, g, to the given seed value s, mod
212	<	* George (2^64+13). We regard s and g as unsigned values
213	<	* (ranging from 0 to 2^64-1). We add g to s either once or twice
214	<	* (mod George) as necessary to produce an (unsigned) result less
215	<	* than 2^64.  We require that g must be at least 13. This
216	<	* guarantees that if (s+g) mod George >= 2^64 then (s+g+g) mod
217	<	* George < 2^64; thus we need only a conditional, not a loop,
218	<	* to be sure of getting a representable value.
219	<	*
220	<	* @param s a seed value
221	<	* @param g a gamma value, 13 <= g (as unsigned)
222	<	*/
223	<	private static long addGammaModGeorge(long s, long g) {
224	<	long p = s + g;
225	<	if (Long.compareUnsigned(p, g) >= 0)
226	<	return p;
227	<	long q = p - 13L;
228	<	return (Long.compareUnsigned(p, 13L) >= 0) ? q : (q + g);
182	>	private SplittableRandom(long seed, long gamma) {
183	>	this.seed = seed;
184	>	this.gamma = gamma;
185		}
186
187		/**
188	<	* Returns a bit-mixed transformation of its argument.
233	<	* See above for explanation.
188	>	* Computes Stafford variant 13 of 64bit mix function.
189		*/
190		private static long mix64(long z) {
191	<	z ^= (z >>> 33);
192	<	z *= 0xff51afd7ed558ccdL;
193	<	z ^= (z >>> 33);
239	<	z *= 0xc4ceb9fe1a85ec53L;
240	<	z ^= (z >>> 33);
241	<	return z;
191	>	z = (z ^ (z >>> 30)) * 0xbf58476d1ce4e5b9L;
192	>	z = (z ^ (z >>> 27)) * 0x94d049bb133111ebL;
193	>	return z ^ (z >>> 31);
194		}
195
196		/**
197	<	* Returns a bit-mixed int transformation of its argument.
246	<	* See above for explanation.
197	>	* Returns the 32 high bits of Stafford variant 4 mix64 function as int.
198		*/
199		private static int mix32(long z) {
200	<	z ^= (z >>> 33);
201	<	z *= 0xc4ceb9fe1a85ec53L;
251	<	return (int)(z >>> 32);
200	>	z = (z ^ (z >>> 33)) * 0x62a9d9ed799705f5L;
201	>	return (int)(((z ^ (z >>> 28)) * 0xcb24d0a5c88c35b3L) >>> 32);
202		}
203
204		/**
205	<	* Internal constructor used by all other constructors and by
256	<	* method split. Establishes the initial seed for this instance,
257	<	* and uses the given splitSeed to establish gamma, as well as the
258	<	* nextSplit to use by this instance. The loop to skip ineligible
259	<	* gammas very rarely iterates, and does so at most 13 times.
205	>	* Returns the gamma value to use for a new split instance.
206		*/
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);
267	<	} while (Long.compareUnsigned(g, 13L) < 0);
268	<	this.gamma = g;
269	<	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		}
214
215		/**
216	<	* Updates in-place and returns seed.
274	<	* 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		}
221
222	<	/**
223	<	* 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		/*
#	Line 364 | Line 321 | public class SplittableRandom {
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;
#	Line 403 | Line 360 | public class SplittableRandom {
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		/**
#	Line 417 | Line 374 | public class SplittableRandom {
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(GOLDEN_GAMMA << 1);
379	>	this.seed = mix64(s);
380	>	this.gamma = mixGamma(s + GOLDEN_GAMMA);
381		}
382
383		/**
#	Line 436 | Line 395 | public class SplittableRandom {
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	>	/**
402	>	* Fills a user-supplied byte array with generated pseudorandom bytes.
403	>	*
404	>	* @param  bytes the byte array to fill with pseudorandom bytes
405	>	* @throws NullPointerException if bytes is null
406	>	* @since  10
407	>	*/
408	>	public void nextBytes(byte[] bytes) {
409	>	int i = 0;
410	>	int len = bytes.length;
411	>	for (int words = len >> 3; words--> 0; ) {
412	>	long rnd = nextLong();
413	>	for (int n = 8; n--> 0; rnd >>>= Byte.SIZE)
414	>	bytes[i++] = (byte)rnd;
415	>	}
416	>	if (i < len)
417	>	for (long rnd = nextLong(); i < len; rnd >>>= Byte.SIZE)
418	>	bytes[i++] = (byte)rnd;
419		}
420
421		/**
#	Line 452 | Line 431 | public class SplittableRandom {
431		* Returns a pseudorandom {@code int} value between zero (inclusive)
432		* and the specified bound (exclusive).
433		*
434	<	* @param bound the bound on the random number to be returned.  Must be
456	<	*        positive.
434	>	* @param bound the upper bound (exclusive).  Must be positive.
435		* @return a pseudorandom {@code int} value between zero
436		*         (inclusive) and the bound (exclusive)
437	<	* @throws IllegalArgumentException if the bound is less than zero
437	>	* @throws IllegalArgumentException if {@code bound} is not positive
438		*/
439		public int nextInt(int bound) {
440		if (bound <= 0)
441	<	throw new IllegalArgumentException("bound must be positive");
441	>	throw new IllegalArgumentException(BAD_BOUND);
442		// Specialize internalNextInt for origin 0
443		int r = mix32(nextSeed());
444		int m = bound - 1;
445	<	if ((bound & m) == 0L) // power of two
445	>	if ((bound & m) == 0) // power of two
446		r &= m;
447		else { // reject over-represented candidates
448		for (int u = r >>> 1;
#	Line 488 | Line 466 | public class SplittableRandom {
466		*/
467		public int nextInt(int origin, int bound) {
468		if (origin >= bound)
469	<	throw new IllegalArgumentException("bound must be greater than origin");
469	>	throw new IllegalArgumentException(BAD_RANGE);
470		return internalNextInt(origin, bound);
471		}
472
#	Line 505 | Line 483 | public class SplittableRandom {
483		* Returns a pseudorandom {@code long} value between zero (inclusive)
484		* and the specified bound (exclusive).
485		*
486	<	* @param bound the bound on the random number to be returned.  Must be
509	<	*        positive.
486	>	* @param bound the upper bound (exclusive).  Must be positive.
487		* @return a pseudorandom {@code long} value between zero
488		*         (inclusive) and the bound (exclusive)
489	<	* @throws IllegalArgumentException if {@code bound} is less than zero
489	>	* @throws IllegalArgumentException if {@code bound} is not positive
490		*/
491		public long nextLong(long bound) {
492		if (bound <= 0)
493	<	throw new IllegalArgumentException("bound must be positive");
493	>	throw new IllegalArgumentException(BAD_BOUND);
494		// Specialize internalNextLong for origin 0
495		long r = mix64(nextSeed());
496		long m = bound - 1;
#	Line 541 | Line 518 | public class SplittableRandom {
518		*/
519		public long nextLong(long origin, long bound) {
520		if (origin >= bound)
521	<	throw new IllegalArgumentException("bound must be greater than origin");
521	>	throw new IllegalArgumentException(BAD_RANGE);
522		return internalNextLong(origin, bound);
523		}
524
#	Line 550 | Line 527 | public class SplittableRandom {
527		* (inclusive) and one (exclusive).
528		*
529		* @return a pseudorandom {@code double} value between zero
530	<	* (inclusive) and one (exclusive)
530	>	*         (inclusive) and one (exclusive)
531		*/
532		public double nextDouble() {
533	<	return (nextLong() >>> 11) * DOUBLE_UNIT;
533	>	return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT;
534		}
535
536		/**
537		* Returns a pseudorandom {@code double} value between 0.0
538		* (inclusive) and the specified bound (exclusive).
539		*
540	<	* @param bound the bound on the random number to be returned.  Must be
564	<	*        positive.
540	>	* @param bound the upper bound (exclusive).  Must be positive.
541		* @return a pseudorandom {@code double} value between zero
542		*         (inclusive) and the bound (exclusive)
543	<	* @throws IllegalArgumentException if {@code bound} is less than zero
543	>	* @throws IllegalArgumentException if {@code bound} is not positive
544		*/
545		public double nextDouble(double bound) {
546		if (!(bound > 0.0))
547	<	throw new IllegalArgumentException("bound must be positive");
548	<	double result = nextDouble() * bound;
547	>	throw new IllegalArgumentException(BAD_BOUND);
548	>	double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound;
549		return (result < bound) ?  result : // correct for rounding
550		Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
551		}
#	Line 579 | Line 555 | public class SplittableRandom {
555		* origin (inclusive) and bound (exclusive).
556		*
557		* @param origin the least value returned
558	<	* @param bound the upper bound
558	>	* @param bound the upper bound (exclusive)
559		* @return a pseudorandom {@code double} value between the origin
560		*         (inclusive) and the bound (exclusive)
561		* @throws IllegalArgumentException if {@code origin} is greater than
#	Line 587 | Line 563 | public class SplittableRandom {
563		*/
564		public double nextDouble(double origin, double bound) {
565		if (!(origin < bound))
566	<	throw new IllegalArgumentException("bound must be greater than origin");
566	>	throw new IllegalArgumentException(BAD_RANGE);
567		return internalNextDouble(origin, bound);
568		}
569
570	+	/**
571	+	* Returns a pseudorandom {@code boolean} value.
572	+	*
573	+	* @return a pseudorandom {@code boolean} value
574	+	*/
575	+	public boolean nextBoolean() {
576	+	return mix32(nextSeed()) < 0;
577	+	}
578	+
579		// stream methods, coded in a way intended to better isolate for
580		// maintenance purposes the small differences across forms.
581
582		/**
583	<	* Returns a stream producing the given {@code streamSize} number of
584	<	* pseudorandom {@code int} values.
583	>	* Returns a stream producing the given {@code streamSize} number
584	>	* of pseudorandom {@code int} values from this generator and/or
585	>	* one split from it.
586		*
587		* @param streamSize the number of values to generate
588		* @return a stream of pseudorandom {@code int} values
#	Line 605 | Line 591 | public class SplittableRandom {
591		*/
592		public IntStream ints(long streamSize) {
593		if (streamSize < 0L)
594	<	throw new IllegalArgumentException("negative Stream size");
594	>	throw new IllegalArgumentException(BAD_SIZE);
595		return StreamSupport.intStream
596		(new RandomIntsSpliterator
597		(this, 0L, streamSize, Integer.MAX_VALUE, 0),
#	Line 614 | Line 600 | public class SplittableRandom {
600
601		/**
602		* Returns an effectively unlimited stream of pseudorandom {@code int}
603	<	* values.
603	>	* values from this generator and/or one split from it.
604		*
605		* @implNote This method is implemented to be equivalent to {@code
606		* ints(Long.MAX_VALUE)}.
#	Line 629 | Line 615 | public class SplittableRandom {
615		}
616
617		/**
618	<	* Returns a stream producing the given {@code streamSize} number of
619	<	* pseudorandom {@code int} values, each conforming to the given
620	<	* origin and bound.
618	>	* Returns a stream producing the given {@code streamSize} number
619	>	* of pseudorandom {@code int} values from this generator and/or one split
620	>	* from it; each value conforms to the given origin (inclusive) and bound
621	>	* (exclusive).
622		*
623		* @param streamSize the number of values to generate
624	<	* @param randomNumberOrigin the origin of each random value
625	<	* @param randomNumberBound the bound of each random value
624	>	* @param randomNumberOrigin the origin (inclusive) of each random value
625	>	* @param randomNumberBound the bound (exclusive) of each random value
626		* @return a stream of pseudorandom {@code int} values,
627	<	*         each with the given origin and bound
627	>	*         each with the given origin (inclusive) and bound (exclusive)
628		* @throws IllegalArgumentException if {@code streamSize} is
629		*         less than zero, or {@code randomNumberOrigin}
630		*         is greater than or equal to {@code randomNumberBound}
#	Line 645 | Line 632 | public class SplittableRandom {
632		public IntStream ints(long streamSize, int randomNumberOrigin,
633		int randomNumberBound) {
634		if (streamSize < 0L)
635	<	throw new IllegalArgumentException("negative Stream size");
635	>	throw new IllegalArgumentException(BAD_SIZE);
636		if (randomNumberOrigin >= randomNumberBound)
637	<	throw new IllegalArgumentException("bound must be greater than origin");
637	>	throw new IllegalArgumentException(BAD_RANGE);
638		return StreamSupport.intStream
639		(new RandomIntsSpliterator
640		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 656 | Line 643 | public class SplittableRandom {
643
644		/**
645		* Returns an effectively unlimited stream of pseudorandom {@code
646	<	* int} values, each conforming to the given origin and bound.
646	>	* int} values from this generator and/or one split from it; each value
647	>	* conforms to the given origin (inclusive) and bound (exclusive).
648		*
649		* @implNote This method is implemented to be equivalent to {@code
650		* ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
651		*
652	<	* @param randomNumberOrigin the origin of each random value
653	<	* @param randomNumberBound the bound of each random value
652	>	* @param randomNumberOrigin the origin (inclusive) of each random value
653	>	* @param randomNumberBound the bound (exclusive) of each random value
654		* @return a stream of pseudorandom {@code int} values,
655	<	*         each with the given origin and bound
655	>	*         each with the given origin (inclusive) and bound (exclusive)
656		* @throws IllegalArgumentException if {@code randomNumberOrigin}
657		*         is greater than or equal to {@code randomNumberBound}
658		*/
659		public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
660		if (randomNumberOrigin >= randomNumberBound)
661	<	throw new IllegalArgumentException("bound must be greater than origin");
661	>	throw new IllegalArgumentException(BAD_RANGE);
662		return StreamSupport.intStream
663		(new RandomIntsSpliterator
664		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 678 | Line 666 | public class SplittableRandom {
666		}
667
668		/**
669	<	* Returns a stream producing the given {@code streamSize} number of
670	<	* pseudorandom {@code long} values.
669	>	* Returns a stream producing the given {@code streamSize} number
670	>	* of pseudorandom {@code long} values from this generator and/or
671	>	* one split from it.
672		*
673		* @param streamSize the number of values to generate
674		* @return a stream of pseudorandom {@code long} values
#	Line 688 | Line 677 | public class SplittableRandom {
677		*/
678		public LongStream longs(long streamSize) {
679		if (streamSize < 0L)
680	<	throw new IllegalArgumentException("negative Stream size");
680	>	throw new IllegalArgumentException(BAD_SIZE);
681		return StreamSupport.longStream
682		(new RandomLongsSpliterator
683		(this, 0L, streamSize, Long.MAX_VALUE, 0L),
#	Line 696 | Line 685 | public class SplittableRandom {
685		}
686
687		/**
688	<	* Returns an effectively unlimited stream of pseudorandom {@code long}
689	<	* values.
688	>	* Returns an effectively unlimited stream of pseudorandom {@code
689	>	* long} values from this generator and/or one split from it.
690		*
691		* @implNote This method is implemented to be equivalent to {@code
692		* longs(Long.MAX_VALUE)}.
#	Line 713 | Line 702 | public class SplittableRandom {
702
703		/**
704		* Returns a stream producing the given {@code streamSize} number of
705	<	* pseudorandom {@code long} values, each conforming to the
706	<	* given origin and bound.
705	>	* pseudorandom {@code long} values from this generator and/or one split
706	>	* from it; each value conforms to the given origin (inclusive) and bound
707	>	* (exclusive).
708		*
709		* @param streamSize the number of values to generate
710	<	* @param randomNumberOrigin the origin of each random value
711	<	* @param randomNumberBound the bound of each random value
710	>	* @param randomNumberOrigin the origin (inclusive) of each random value
711	>	* @param randomNumberBound the bound (exclusive) of each random value
712		* @return a stream of pseudorandom {@code long} values,
713	<	*         each with the given origin and bound
713	>	*         each with the given origin (inclusive) and bound (exclusive)
714		* @throws IllegalArgumentException if {@code streamSize} is
715		*         less than zero, or {@code randomNumberOrigin}
716		*         is greater than or equal to {@code randomNumberBound}
#	Line 728 | Line 718 | public class SplittableRandom {
718		public LongStream longs(long streamSize, long randomNumberOrigin,
719		long randomNumberBound) {
720		if (streamSize < 0L)
721	<	throw new IllegalArgumentException("negative Stream size");
721	>	throw new IllegalArgumentException(BAD_SIZE);
722		if (randomNumberOrigin >= randomNumberBound)
723	<	throw new IllegalArgumentException("bound must be greater than origin");
723	>	throw new IllegalArgumentException(BAD_RANGE);
724		return StreamSupport.longStream
725		(new RandomLongsSpliterator
726		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 739 | Line 729 | public class SplittableRandom {
729
730		/**
731		* Returns an effectively unlimited stream of pseudorandom {@code
732	<	* long} values, each conforming to the given origin and bound.
732	>	* long} values from this generator and/or one split from it; each value
733	>	* conforms to the given origin (inclusive) and bound (exclusive).
734		*
735		* @implNote This method is implemented to be equivalent to {@code
736		* longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
737		*
738	<	* @param randomNumberOrigin the origin of each random value
739	<	* @param randomNumberBound the bound of each random value
738	>	* @param randomNumberOrigin the origin (inclusive) of each random value
739	>	* @param randomNumberBound the bound (exclusive) of each random value
740		* @return a stream of pseudorandom {@code long} values,
741	<	*         each with the given origin and bound
741	>	*         each with the given origin (inclusive) and bound (exclusive)
742		* @throws IllegalArgumentException if {@code randomNumberOrigin}
743		*         is greater than or equal to {@code randomNumberBound}
744		*/
745		public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
746		if (randomNumberOrigin >= randomNumberBound)
747	<	throw new IllegalArgumentException("bound must be greater than origin");
747	>	throw new IllegalArgumentException(BAD_RANGE);
748		return StreamSupport.longStream
749		(new RandomLongsSpliterator
750		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 762 | Line 753 | public class SplittableRandom {
753
754		/**
755		* Returns a stream producing the given {@code streamSize} number of
756	<	* pseudorandom {@code double} values, each between zero
757	<	* (inclusive) and one (exclusive).
756	>	* pseudorandom {@code double} values from this generator and/or one split
757	>	* from it; each value is between zero (inclusive) and one (exclusive).
758		*
759		* @param streamSize the number of values to generate
760		* @return a stream of {@code double} values
#	Line 772 | Line 763 | public class SplittableRandom {
763		*/
764		public DoubleStream doubles(long streamSize) {
765		if (streamSize < 0L)
766	<	throw new IllegalArgumentException("negative Stream size");
766	>	throw new IllegalArgumentException(BAD_SIZE);
767		return StreamSupport.doubleStream
768		(new RandomDoublesSpliterator
769		(this, 0L, streamSize, Double.MAX_VALUE, 0.0),
#	Line 781 | Line 772 | public class SplittableRandom {
772
773		/**
774		* Returns an effectively unlimited stream of pseudorandom {@code
775	<	* double} values, each between zero (inclusive) and one
776	<	* (exclusive).
775	>	* double} values from this generator and/or one split from it; each value
776	>	* is between zero (inclusive) and one (exclusive).
777		*
778		* @implNote This method is implemented to be equivalent to {@code
779		* doubles(Long.MAX_VALUE)}.
#	Line 798 | Line 789 | public class SplittableRandom {
789
790		/**
791		* Returns a stream producing the given {@code streamSize} number of
792	<	* pseudorandom {@code double} values, each conforming to the
793	<	* given origin and bound.
792	>	* pseudorandom {@code double} values from this generator and/or one split
793	>	* from it; each value conforms to the given origin (inclusive) and bound
794	>	* (exclusive).
795		*
796		* @param streamSize the number of values to generate
797	<	* @param randomNumberOrigin the origin of each random value
798	<	* @param randomNumberBound the bound of each random value
797	>	* @param randomNumberOrigin the origin (inclusive) of each random value
798	>	* @param randomNumberBound the bound (exclusive) of each random value
799		* @return a stream of pseudorandom {@code double} values,
800	<	* each with the given origin and bound
800	>	*         each with the given origin (inclusive) and bound (exclusive)
801		* @throws IllegalArgumentException if {@code streamSize} is
802	<	* less than zero
811	<	* @throws IllegalArgumentException if {@code randomNumberOrigin}
802	>	*         less than zero, or {@code randomNumberOrigin}
803		*         is greater than or equal to {@code randomNumberBound}
804		*/
805		public DoubleStream doubles(long streamSize, double randomNumberOrigin,
806		double randomNumberBound) {
807		if (streamSize < 0L)
808	<	throw new IllegalArgumentException("negative Stream size");
808	>	throw new IllegalArgumentException(BAD_SIZE);
809		if (!(randomNumberOrigin < randomNumberBound))
810	<	throw new IllegalArgumentException("bound must be greater than origin");
810	>	throw new IllegalArgumentException(BAD_RANGE);
811		return StreamSupport.doubleStream
812		(new RandomDoublesSpliterator
813		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 825 | Line 816 | public class SplittableRandom {
816
817		/**
818		* Returns an effectively unlimited stream of pseudorandom {@code
819	<	* double} values, each conforming to the given origin and bound.
819	>	* double} values from this generator and/or one split from it; each value
820	>	* conforms to the given origin (inclusive) and bound (exclusive).
821		*
822		* @implNote This method is implemented to be equivalent to {@code
823		* doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
824		*
825	<	* @param randomNumberOrigin the origin of each random value
826	<	* @param randomNumberBound the bound of each random value
825	>	* @param randomNumberOrigin the origin (inclusive) of each random value
826	>	* @param randomNumberBound the bound (exclusive) of each random value
827		* @return a stream of pseudorandom {@code double} values,
828	<	* each with the given origin and bound
828	>	*         each with the given origin (inclusive) and bound (exclusive)
829		* @throws IllegalArgumentException if {@code randomNumberOrigin}
830		*         is greater than or equal to {@code randomNumberBound}
831		*/
832		public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
833		if (!(randomNumberOrigin < randomNumberBound))
834	<	throw new IllegalArgumentException("bound must be greater than origin");
834	>	throw new IllegalArgumentException(BAD_RANGE);
835		return StreamSupport.doubleStream
836		(new RandomDoublesSpliterator
837		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 854 | Line 846 | public class SplittableRandom {
846		* approach. The long and double versions of this class are
847		* identical except for types.
848		*/
849	<	static class RandomIntsSpliterator implements Spliterator.OfInt {
849	>	private static final class RandomIntsSpliterator
850	>	implements Spliterator.OfInt {
851		final SplittableRandom rng;
852		long index;
853		final long fence;
#	Line 897 | Line 890 | public class SplittableRandom {
890		long i = index, f = fence;
891		if (i < f) {
892		index = f;
893	+	SplittableRandom r = rng;
894		int o = origin, b = bound;
895		do {
896	<	consumer.accept(rng.internalNextInt(o, b));
896	>	consumer.accept(r.internalNextInt(o, b));
897		} while (++i < f);
898		}
899		}
#	Line 908 | Line 902 | public class SplittableRandom {
902		/**
903		* Spliterator for long streams.
904		*/
905	<	static class RandomLongsSpliterator implements Spliterator.OfLong {
905	>	private static final class RandomLongsSpliterator
906	>	implements Spliterator.OfLong {
907		final SplittableRandom rng;
908		long index;
909		final long fence;
#	Line 951 | Line 946 | public class SplittableRandom {
946		long i = index, f = fence;
947		if (i < f) {
948		index = f;
949	+	SplittableRandom r = rng;
950		long o = origin, b = bound;
951		do {
952	<	consumer.accept(rng.internalNextLong(o, b));
952	>	consumer.accept(r.internalNextLong(o, b));
953		} while (++i < f);
954		}
955		}
#	Line 963 | Line 959 | public class SplittableRandom {
959		/**
960		* Spliterator for double streams.
961		*/
962	<	static class RandomDoublesSpliterator implements Spliterator.OfDouble {
962	>	private static final class RandomDoublesSpliterator
963	>	implements Spliterator.OfDouble {
964		final SplittableRandom rng;
965		long index;
966		final long fence;
#	Line 1006 | Line 1003 | public class SplittableRandom {
1003		long i = index, f = fence;
1004		if (i < f) {
1005		index = f;
1006	+	SplittableRandom r = rng;
1007		double o = origin, b = bound;
1008		do {
1009	<	consumer.accept(rng.internalNextDouble(o, b));
1009	>	consumer.accept(r.internalNextDouble(o, b));
1010		} while (++i < f);
1011		}
1012		}

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