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Comparing jsr166/src/main/java/util/SplittableRandom.java (file contents):
Revision 1.8 by jsr166, Fri Jul 12 19:45:19 2013 UTC vs.
Revision 1.39 by jsr166, Mon Feb 20 22:07:50 2017 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: <ul>
43	>	* {@link java.util.Random} but differs in the following ways:
44	>	*
45	>	* <ul>
46		*
47		* <li>Series of generated values pass the DieHarder suite testing
48		* independence and uniformity properties of random number generators.
#	Line 49 | 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 68 | 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	+	* {@code 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 {
80	<
81	<	/*
82	<	* File organization: First the non-public methods that constitute
83	<	* the main algorithm, then the main public methods, followed by
84	<	* some custom spliterator classes needed for stream methods.
85	<	*
86	<	* Credits: Primary algorithm and code by Guy Steele.  Stream
87	<	* support methods by Doug Lea.  Documentation jointly produced
88	<	* with additional help from Brian Goetz.
89	<	*/
89	>	public final class SplittableRandom {
90
91		/*
92		* Implementation Overview.
#	Line 94 | 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
102	<	* return this value, but instead the results of bit-mixing
103	<	* transformations that produce more uniformly distributed
104	<	* sequences.
105	<	*
106	<	* "George" is the otherwise nameless (because it cannot be
107	<	* represented) prime number 2^64+13. Using a prime number larger
108	<	* than can fit in a long ensures that all possible long values
109	<	* can occur, plus 13 others that just get skipped over when they
110	<	* are encountered; see method addGammaModGeorge. For this to
111	<	* work, initial gamma values must be at least 13.
112	<	*
113	<	* The value of gamma differs for each instance across a series of
114	<	* splits, and is generated using a slightly stripped-down variant
115	<	* of the same algorithm, but operating across calls to split(),
116	<	* not calls to nextSeed(): Each instance carries the state of
117	<	* this generator as nextSplit, and uses mix64(nextSplit) as its
118	<	* own gamma value. Computations of gammas themselves use a fixed
119	<	* constant as the second argument to the addGammaModGeorge
120	<	* function, GAMMA_GAMMA, a "genuinely random" number from a
121	<	* radioactive decay reading (obtained from
122	<	* http://www.fourmilab.ch/hotbits/) meeting the above range
123	<	* constraint. Using a fixed constant maintains the invariant that
124	<	* the value of gamma is the same for every instance that is at
125	<	* the same split-distance from their common root. (Note: there is
126	<	* nothing especially magic about obtaining this constant from a
127	<	* "truly random" physical source rather than just choosing one
128	<	* arbitrarily; using "hotbits" was merely an aesthetically pleasing
129	<	* choice.  In either case, good statistical behavior of the
130	<	* algorithm should be, and was, verified by using the DieHarder
131	<	* test suite.)
132	<	*
133	<	* The mix64 bit-mixing function called by nextLong and other
134	<	* methods computes the same value as the "64-bit finalizer"
135	<	* function in Austin Appleby's MurmurHash3 algorithm.  See
136	<	* http://code.google.com/p/smhasher/wiki/MurmurHash3 , which
137	<	* comments: "The constants for the finalizers were generated by a
138	<	* simple simulated-annealing algorithm, and both avalanche all
139	<	* bits of 'h' to within 0.25% bias." It also appears to work to
140	<	* use instead any of the variants proposed by David Stafford at
141	<	* http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html
142	<	* but these variants have not yet been tested as thoroughly
143	<	* in the context of the implementation of SplittableRandom.
144	<	*
145	<	* The mix32 function used for nextInt just consists of two of the
146	<	* five lines of mix64; avalanche testing shows that the 64-bit result
147	<	* has its top 32 bits avalanched well, though not the bottom 32 bits.
148	<	* DieHarder tests show that it is adequate for generating one
149	<	* random int from the 64-bit result of nextSeed.
150	<	*
151	<	* Support for the default (no-argument) constructor relies on an
152	<	* AtomicLong (defaultSeedGenerator) to help perform the
153	<	* equivalent of a split of a statically constructed
154	<	* SplittableRandom. Unlike other cases, this split must be
155	<	* performed in a thread-safe manner. We use
156	<	* AtomicLong.compareAndSet as the (typically) most efficient
157	<	* mechanism. To bootstrap, we start off using System.nanotime(),
158	<	* and update using another "genuinely random" constant
159	<	* DEFAULT_SEED_GAMMA. The default constructor uses GAMMA_GAMMA,
160	<	* not 0, for its splitSeed argument (addGammaModGeorge(0,
161	<	* GAMMA_GAMMA) == GAMMA_GAMMA) to reflect that each is split from
162	<	* this root generator, even though the root is not explicitly
163	<	* represented as a SplittableRandom.
164	<	*/
165	<
166	<	/**
167	<	* The "genuinely random" value for producing new gamma values.
168	<	* The value is arbitrary, subject to the requirement that it be
169	<	* greater or equal to 13.
170	<	*/
171	<	private static final long GAMMA_GAMMA = 0xF2281E2DBA6606F3L;
172	<
173	<	/**
174	<	* The "genuinely random" seed update value for default constructors.
175	<	* The value is arbitrary, subject to the requirement that it be
176	<	* 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		*/
178	–	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 =
190	<	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
204	<	* addGammaModGeorge across instances.
180	>	* Internal constructor used by all others except default constructor.
181		*/
182	<	private final long nextSplit;
183	<
184	<	/**
209	<	* Adds the given gamma value, g, to the given seed value s, mod
210	<	* George (2^64+13). We regard s and g as unsigned values
211	<	* (ranging from 0 to 2^64-1). We add g to s either once or twice
212	<	* (mod George) as necessary to produce an (unsigned) result less
213	<	* than 2^64.  We require that g must be at least 13. This
214	<	* guarantees that if (s+g) mod George >= 2^64 then (s+g+g) mod
215	<	* George < 2^64; thus we need only a conditional, not a loop,
216	<	* to be sure of getting a representable value.
217	<	*
218	<	* @param s a seed value
219	<	* @param g a gamma value, 13 <= g (as unsigned)
220	<	*/
221	<	private static long addGammaModGeorge(long s, long g) {
222	<	long p = s + g;
223	<	if (Long.compareUnsigned(p, g) >= 0)
224	<	return p;
225	<	long q = p - 13L;
226	<	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.
231	<	* 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);
237	<	z *= 0xc4ceb9fe1a85ec53L;
238	<	z ^= (z >>> 33);
239	<	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.
244	<	* 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;
249	<	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
254	<	* method split. Establishes the initial seed for this instance,
255	<	* and uses the given splitSeed to establish gamma, as well as the
256	<	* nextSplit to use by this instance. The loop to skip ineligible
257	<	* 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);
265	<	} while (Long.compareUnsigned(g, 13L) < 0);
266	<	this.gamma = g;
267	<	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.
272	<	* 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 362 | 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 401 | 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 415 | 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 434 | 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		/**
#	Line 450 | Line 411 | public class SplittableRandom {
411		* Returns a pseudorandom {@code int} value between zero (inclusive)
412		* and the specified bound (exclusive).
413		*
414	<	* @param bound the bound on the random number to be returned.  Must be
454	<	*        positive.
414	>	* @param bound the upper bound (exclusive).  Must be positive.
415		* @return a pseudorandom {@code int} value between zero
416	<	*         (inclusive) and the bound (exclusive).
417	<	* @throws IllegalArgumentException if the bound is less than zero
416	>	*         (inclusive) and the bound (exclusive)
417	>	* @throws IllegalArgumentException if {@code bound} is not positive
418		*/
419		public int nextInt(int bound) {
420		if (bound <= 0)
421	<	throw new IllegalArgumentException("bound must be positive");
421	>	throw new IllegalArgumentException(BAD_BOUND);
422		// Specialize internalNextInt for origin 0
423		int r = mix32(nextSeed());
424		int m = bound - 1;
425	<	if ((bound & m) == 0L) // power of two
425	>	if ((bound & m) == 0) // power of two
426		r &= m;
427		else { // reject over-represented candidates
428		for (int u = r >>> 1;
#	Line 480 | Line 440 | public class SplittableRandom {
440		* @param origin the least value returned
441		* @param bound the upper bound (exclusive)
442		* @return a pseudorandom {@code int} value between the origin
443	<	*         (inclusive) and the bound (exclusive).
443	>	*         (inclusive) and the bound (exclusive)
444		* @throws IllegalArgumentException if {@code origin} is greater than
445		*         or equal to {@code bound}
446		*/
447		public int nextInt(int origin, int bound) {
448		if (origin >= bound)
449	<	throw new IllegalArgumentException("bound must be greater than origin");
449	>	throw new IllegalArgumentException(BAD_RANGE);
450		return internalNextInt(origin, bound);
451		}
452
#	Line 503 | Line 463 | public class SplittableRandom {
463		* Returns a pseudorandom {@code long} value between zero (inclusive)
464		* and the specified bound (exclusive).
465		*
466	<	* @param bound the bound on the random number to be returned.  Must be
507	<	*        positive.
466	>	* @param bound the upper bound (exclusive).  Must be positive.
467		* @return a pseudorandom {@code long} value between zero
468	<	*         (inclusive) and the bound (exclusive).
469	<	* @throws IllegalArgumentException if {@code bound} is less than zero
468	>	*         (inclusive) and the bound (exclusive)
469	>	* @throws IllegalArgumentException if {@code bound} is not positive
470		*/
471		public long nextLong(long bound) {
472		if (bound <= 0)
473	<	throw new IllegalArgumentException("bound must be positive");
473	>	throw new IllegalArgumentException(BAD_BOUND);
474		// Specialize internalNextLong for origin 0
475		long r = mix64(nextSeed());
476		long m = bound - 1;
#	Line 533 | Line 492 | public class SplittableRandom {
492		* @param origin the least value returned
493		* @param bound the upper bound (exclusive)
494		* @return a pseudorandom {@code long} value between the origin
495	<	*         (inclusive) and the bound (exclusive).
495	>	*         (inclusive) and the bound (exclusive)
496		* @throws IllegalArgumentException if {@code origin} is greater than
497		*         or equal to {@code bound}
498		*/
499		public long nextLong(long origin, long bound) {
500		if (origin >= bound)
501	<	throw new IllegalArgumentException("bound must be greater than origin");
501	>	throw new IllegalArgumentException(BAD_RANGE);
502		return internalNextLong(origin, bound);
503		}
504
#	Line 548 | Line 507 | public class SplittableRandom {
507		* (inclusive) and one (exclusive).
508		*
509		* @return a pseudorandom {@code double} value between zero
510	<	* (inclusive) and one (exclusive)
510	>	*         (inclusive) and one (exclusive)
511		*/
512		public double nextDouble() {
513	<	return (nextLong() >>> 11) * DOUBLE_UNIT;
513	>	return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT;
514		}
515
516		/**
517		* Returns a pseudorandom {@code double} value between 0.0
518		* (inclusive) and the specified bound (exclusive).
519		*
520	<	* @param bound the bound on the random number to be returned.  Must be
562	<	*        positive.
520	>	* @param bound the upper bound (exclusive).  Must be positive.
521		* @return a pseudorandom {@code double} value between zero
522	<	*         (inclusive) and the bound (exclusive).
523	<	* @throws IllegalArgumentException if {@code bound} is less than zero
522	>	*         (inclusive) and the bound (exclusive)
523	>	* @throws IllegalArgumentException if {@code bound} is not positive
524		*/
525		public double nextDouble(double bound) {
526		if (!(bound > 0.0))
527	<	throw new IllegalArgumentException("bound must be positive");
528	<	double result = nextDouble() * bound;
527	>	throw new IllegalArgumentException(BAD_BOUND);
528	>	double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound;
529		return (result < bound) ?  result : // correct for rounding
530		Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
531		}
#	Line 577 | Line 535 | public class SplittableRandom {
535		* origin (inclusive) and bound (exclusive).
536		*
537		* @param origin the least value returned
538	<	* @param bound the upper bound
538	>	* @param bound the upper bound (exclusive)
539		* @return a pseudorandom {@code double} value between the origin
540	<	*         (inclusive) and the bound (exclusive).
540	>	*         (inclusive) and the bound (exclusive)
541		* @throws IllegalArgumentException if {@code origin} is greater than
542		*         or equal to {@code bound}
543		*/
544		public double nextDouble(double origin, double bound) {
545		if (!(origin < bound))
546	<	throw new IllegalArgumentException("bound must be greater than origin");
546	>	throw new IllegalArgumentException(BAD_RANGE);
547		return internalNextDouble(origin, bound);
548		}
549
550	+	/**
551	+	* Returns a pseudorandom {@code boolean} value.
552	+	*
553	+	* @return a pseudorandom {@code boolean} value
554	+	*/
555	+	public boolean nextBoolean() {
556	+	return mix32(nextSeed()) < 0;
557	+	}
558	+
559		// stream methods, coded in a way intended to better isolate for
560		// maintenance purposes the small differences across forms.
561
562		/**
563	<	* Returns a stream producing the given {@code streamSize} number of
564	<	* pseudorandom {@code int} values.
563	>	* Returns a stream producing the given {@code streamSize} number
564	>	* of pseudorandom {@code int} values from this generator and/or
565	>	* one split from it.
566		*
567		* @param streamSize the number of values to generate
568		* @return a stream of pseudorandom {@code int} values
#	Line 603 | Line 571 | public class SplittableRandom {
571		*/
572		public IntStream ints(long streamSize) {
573		if (streamSize < 0L)
574	<	throw new IllegalArgumentException("negative Stream size");
574	>	throw new IllegalArgumentException(BAD_SIZE);
575		return StreamSupport.intStream
576		(new RandomIntsSpliterator
577		(this, 0L, streamSize, Integer.MAX_VALUE, 0),
#	Line 612 | Line 580 | public class SplittableRandom {
580
581		/**
582		* Returns an effectively unlimited stream of pseudorandom {@code int}
583	<	* values
583	>	* values from this generator and/or one split from it.
584		*
585		* @implNote This method is implemented to be equivalent to {@code
586		* ints(Long.MAX_VALUE)}.
#	Line 627 | Line 595 | public class SplittableRandom {
595		}
596
597		/**
598	<	* Returns a stream producing the given {@code streamSize} number of
599	<	* pseudorandom {@code int} values, each conforming to the given
600	<	* origin and bound.
598	>	* Returns a stream producing the given {@code streamSize} number
599	>	* of pseudorandom {@code int} values from this generator and/or one split
600	>	* from it; each value conforms to the given origin (inclusive) and bound
601	>	* (exclusive).
602		*
603		* @param streamSize the number of values to generate
604	<	* @param randomNumberOrigin the origin of each random value
605	<	* @param randomNumberBound the bound of each random value
604	>	* @param randomNumberOrigin the origin (inclusive) of each random value
605	>	* @param randomNumberBound the bound (exclusive) of each random value
606		* @return a stream of pseudorandom {@code int} values,
607	<	*         each with the given origin and bound.
607	>	*         each with the given origin (inclusive) and bound (exclusive)
608		* @throws IllegalArgumentException if {@code streamSize} is
609		*         less than zero, or {@code randomNumberOrigin}
610		*         is greater than or equal to {@code randomNumberBound}
#	Line 643 | Line 612 | public class SplittableRandom {
612		public IntStream ints(long streamSize, int randomNumberOrigin,
613		int randomNumberBound) {
614		if (streamSize < 0L)
615	<	throw new IllegalArgumentException("negative Stream size");
615	>	throw new IllegalArgumentException(BAD_SIZE);
616		if (randomNumberOrigin >= randomNumberBound)
617	<	throw new IllegalArgumentException("bound must be greater than origin");
617	>	throw new IllegalArgumentException(BAD_RANGE);
618		return StreamSupport.intStream
619		(new RandomIntsSpliterator
620		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 654 | Line 623 | public class SplittableRandom {
623
624		/**
625		* Returns an effectively unlimited stream of pseudorandom {@code
626	<	* int} values, each conforming to the given origin and bound.
626	>	* int} values from this generator and/or one split from it; each value
627	>	* conforms to the given origin (inclusive) and bound (exclusive).
628		*
629		* @implNote This method is implemented to be equivalent to {@code
630		* ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
631		*
632	<	* @param randomNumberOrigin the origin of each random value
633	<	* @param randomNumberBound the bound of each random value
632	>	* @param randomNumberOrigin the origin (inclusive) of each random value
633	>	* @param randomNumberBound the bound (exclusive) of each random value
634		* @return a stream of pseudorandom {@code int} values,
635	<	*         each with the given origin and bound.
635	>	*         each with the given origin (inclusive) and bound (exclusive)
636		* @throws IllegalArgumentException if {@code randomNumberOrigin}
637		*         is greater than or equal to {@code randomNumberBound}
638		*/
639		public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
640		if (randomNumberOrigin >= randomNumberBound)
641	<	throw new IllegalArgumentException("bound must be greater than origin");
641	>	throw new IllegalArgumentException(BAD_RANGE);
642		return StreamSupport.intStream
643		(new RandomIntsSpliterator
644		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 676 | Line 646 | public class SplittableRandom {
646		}
647
648		/**
649	<	* Returns a stream producing the given {@code streamSize} number of
650	<	* pseudorandom {@code long} values.
649	>	* Returns a stream producing the given {@code streamSize} number
650	>	* of pseudorandom {@code long} values from this generator and/or
651	>	* one split from it.
652		*
653		* @param streamSize the number of values to generate
654		* @return a stream of pseudorandom {@code long} values
#	Line 686 | Line 657 | public class SplittableRandom {
657		*/
658		public LongStream longs(long streamSize) {
659		if (streamSize < 0L)
660	<	throw new IllegalArgumentException("negative Stream size");
660	>	throw new IllegalArgumentException(BAD_SIZE);
661		return StreamSupport.longStream
662		(new RandomLongsSpliterator
663		(this, 0L, streamSize, Long.MAX_VALUE, 0L),
#	Line 694 | Line 665 | public class SplittableRandom {
665		}
666
667		/**
668	<	* Returns an effectively unlimited stream of pseudorandom {@code long}
669	<	* values.
668	>	* Returns an effectively unlimited stream of pseudorandom {@code
669	>	* long} values from this generator and/or one split from it.
670		*
671		* @implNote This method is implemented to be equivalent to {@code
672		* longs(Long.MAX_VALUE)}.
#	Line 711 | Line 682 | public class SplittableRandom {
682
683		/**
684		* Returns a stream producing the given {@code streamSize} number of
685	<	* pseudorandom {@code long} values, each conforming to the
686	<	* given origin and bound.
685	>	* pseudorandom {@code long} values from this generator and/or one split
686	>	* from it; each value conforms to the given origin (inclusive) and bound
687	>	* (exclusive).
688		*
689		* @param streamSize the number of values to generate
690	<	* @param randomNumberOrigin the origin of each random value
691	<	* @param randomNumberBound the bound of each random value
690	>	* @param randomNumberOrigin the origin (inclusive) of each random value
691	>	* @param randomNumberBound the bound (exclusive) of each random value
692		* @return a stream of pseudorandom {@code long} values,
693	<	*         each with the given origin and bound.
693	>	*         each with the given origin (inclusive) and bound (exclusive)
694		* @throws IllegalArgumentException if {@code streamSize} is
695		*         less than zero, or {@code randomNumberOrigin}
696		*         is greater than or equal to {@code randomNumberBound}
#	Line 726 | Line 698 | public class SplittableRandom {
698		public LongStream longs(long streamSize, long randomNumberOrigin,
699		long randomNumberBound) {
700		if (streamSize < 0L)
701	<	throw new IllegalArgumentException("negative Stream size");
701	>	throw new IllegalArgumentException(BAD_SIZE);
702		if (randomNumberOrigin >= randomNumberBound)
703	<	throw new IllegalArgumentException("bound must be greater than origin");
703	>	throw new IllegalArgumentException(BAD_RANGE);
704		return StreamSupport.longStream
705		(new RandomLongsSpliterator
706		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 737 | Line 709 | public class SplittableRandom {
709
710		/**
711		* Returns an effectively unlimited stream of pseudorandom {@code
712	<	* long} values, each conforming to the given origin and bound.
712	>	* long} values from this generator and/or one split from it; each value
713	>	* conforms to the given origin (inclusive) and bound (exclusive).
714		*
715		* @implNote This method is implemented to be equivalent to {@code
716		* longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
717		*
718	<	* @param randomNumberOrigin the origin of each random value
719	<	* @param randomNumberBound the bound of each random value
718	>	* @param randomNumberOrigin the origin (inclusive) of each random value
719	>	* @param randomNumberBound the bound (exclusive) of each random value
720		* @return a stream of pseudorandom {@code long} values,
721	<	*         each with the given origin and bound.
721	>	*         each with the given origin (inclusive) and bound (exclusive)
722		* @throws IllegalArgumentException if {@code randomNumberOrigin}
723		*         is greater than or equal to {@code randomNumberBound}
724		*/
725		public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
726		if (randomNumberOrigin >= randomNumberBound)
727	<	throw new IllegalArgumentException("bound must be greater than origin");
727	>	throw new IllegalArgumentException(BAD_RANGE);
728		return StreamSupport.longStream
729		(new RandomLongsSpliterator
730		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 760 | Line 733 | public class SplittableRandom {
733
734		/**
735		* Returns a stream producing the given {@code streamSize} number of
736	<	* pseudorandom {@code double} values, each between zero
737	<	* (inclusive) and one (exclusive).
736	>	* pseudorandom {@code double} values from this generator and/or one split
737	>	* from it; each value is between zero (inclusive) and one (exclusive).
738		*
739		* @param streamSize the number of values to generate
740		* @return a stream of {@code double} values
#	Line 770 | Line 743 | public class SplittableRandom {
743		*/
744		public DoubleStream doubles(long streamSize) {
745		if (streamSize < 0L)
746	<	throw new IllegalArgumentException("negative Stream size");
746	>	throw new IllegalArgumentException(BAD_SIZE);
747		return StreamSupport.doubleStream
748		(new RandomDoublesSpliterator
749		(this, 0L, streamSize, Double.MAX_VALUE, 0.0),
#	Line 779 | Line 752 | public class SplittableRandom {
752
753		/**
754		* Returns an effectively unlimited stream of pseudorandom {@code
755	<	* double} values, each between zero (inclusive) and one
756	<	* (exclusive).
755	>	* double} values from this generator and/or one split from it; each value
756	>	* is between zero (inclusive) and one (exclusive).
757		*
758		* @implNote This method is implemented to be equivalent to {@code
759		* doubles(Long.MAX_VALUE)}.
#	Line 796 | Line 769 | public class SplittableRandom {
769
770		/**
771		* Returns a stream producing the given {@code streamSize} number of
772	<	* pseudorandom {@code double} values, each conforming to the
773	<	* given origin and bound.
772	>	* pseudorandom {@code double} values from this generator and/or one split
773	>	* from it; each value conforms to the given origin (inclusive) and bound
774	>	* (exclusive).
775		*
776		* @param streamSize the number of values to generate
777	<	* @param randomNumberOrigin the origin of each random value
778	<	* @param randomNumberBound the bound of each random value
777	>	* @param randomNumberOrigin the origin (inclusive) of each random value
778	>	* @param randomNumberBound the bound (exclusive) of each random value
779		* @return a stream of pseudorandom {@code double} values,
780	<	* each with the given origin and bound.
780	>	*         each with the given origin (inclusive) and bound (exclusive)
781		* @throws IllegalArgumentException if {@code streamSize} is
782	<	* less than zero.
809	<	* @throws IllegalArgumentException if {@code randomNumberOrigin}
782	>	*         less than zero, or {@code randomNumberOrigin}
783		*         is greater than or equal to {@code randomNumberBound}
784		*/
785		public DoubleStream doubles(long streamSize, double randomNumberOrigin,
786		double randomNumberBound) {
787		if (streamSize < 0L)
788	<	throw new IllegalArgumentException("negative Stream size");
788	>	throw new IllegalArgumentException(BAD_SIZE);
789		if (!(randomNumberOrigin < randomNumberBound))
790	<	throw new IllegalArgumentException("bound must be greater than origin");
790	>	throw new IllegalArgumentException(BAD_RANGE);
791		return StreamSupport.doubleStream
792		(new RandomDoublesSpliterator
793		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 823 | Line 796 | public class SplittableRandom {
796
797		/**
798		* Returns an effectively unlimited stream of pseudorandom {@code
799	<	* double} values, each conforming to the given origin and bound.
799	>	* double} values from this generator and/or one split from it; each value
800	>	* conforms to the given origin (inclusive) and bound (exclusive).
801		*
802		* @implNote This method is implemented to be equivalent to {@code
803		* doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
804		*
805	<	* @param randomNumberOrigin the origin of each random value
806	<	* @param randomNumberBound the bound of each random value
805	>	* @param randomNumberOrigin the origin (inclusive) of each random value
806	>	* @param randomNumberBound the bound (exclusive) of each random value
807		* @return a stream of pseudorandom {@code double} values,
808	<	* each with the given origin and bound.
808	>	*         each with the given origin (inclusive) and bound (exclusive)
809		* @throws IllegalArgumentException if {@code randomNumberOrigin}
810		*         is greater than or equal to {@code randomNumberBound}
811		*/
812		public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
813		if (!(randomNumberOrigin < randomNumberBound))
814	<	throw new IllegalArgumentException("bound must be greater than origin");
814	>	throw new IllegalArgumentException(BAD_RANGE);
815		return StreamSupport.doubleStream
816		(new RandomDoublesSpliterator
817		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 852 | Line 826 | public class SplittableRandom {
826		* approach. The long and double versions of this class are
827		* identical except for types.
828		*/
829	<	static class RandomIntsSpliterator implements Spliterator.OfInt {
829	>	private static final class RandomIntsSpliterator
830	>	implements Spliterator.OfInt {
831		final SplittableRandom rng;
832		long index;
833		final long fence;
#	Line 895 | Line 870 | public class SplittableRandom {
870		long i = index, f = fence;
871		if (i < f) {
872		index = f;
873	+	SplittableRandom r = rng;
874		int o = origin, b = bound;
875		do {
876	<	consumer.accept(rng.internalNextInt(o, b));
876	>	consumer.accept(r.internalNextInt(o, b));
877		} while (++i < f);
878		}
879		}
#	Line 906 | Line 882 | public class SplittableRandom {
882		/**
883		* Spliterator for long streams.
884		*/
885	<	static class RandomLongsSpliterator implements Spliterator.OfLong {
885	>	private static final class RandomLongsSpliterator
886	>	implements Spliterator.OfLong {
887		final SplittableRandom rng;
888		long index;
889		final long fence;
#	Line 949 | Line 926 | public class SplittableRandom {
926		long i = index, f = fence;
927		if (i < f) {
928		index = f;
929	+	SplittableRandom r = rng;
930		long o = origin, b = bound;
931		do {
932	<	consumer.accept(rng.internalNextLong(o, b));
932	>	consumer.accept(r.internalNextLong(o, b));
933		} while (++i < f);
934		}
935		}
#	Line 961 | Line 939 | public class SplittableRandom {
939		/**
940		* Spliterator for double streams.
941		*/
942	<	static class RandomDoublesSpliterator implements Spliterator.OfDouble {
942	>	private static final class RandomDoublesSpliterator
943	>	implements Spliterator.OfDouble {
944		final SplittableRandom rng;
945		long index;
946		final long fence;
#	Line 1004 | Line 983 | public class SplittableRandom {
983		long i = index, f = fence;
984		if (i < f) {
985		index = f;
986	+	SplittableRandom r = rng;
987		double o = origin, b = bound;
988		do {
989	<	consumer.accept(rng.internalNextDouble(o, b));
989	>	consumer.accept(r.internalNextDouble(o, b));
990		} while (++i < f);
991		}
992		}

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