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Comparing jsr166/src/main/java/util/SplittableRandom.java (file contents):
Revision 1.7 by dl, Fri Jul 12 11:26:34 2013 UTC vs.
Revision 1.27 by jsr166, Sun Sep 13 16:28:14 2015 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.
223	>	* The seed generator for default constructors.
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);
225	>	private static final AtomicLong defaultGen = new AtomicLong(initialSeed());
226	>
227	>	private static long initialSeed() {
228	>	String pp = java.security.AccessController.doPrivileged(
229	>	new sun.security.action.GetPropertyAction(
230	>	"java.util.secureRandomSeed"));
231	>	if (pp != null && pp.equalsIgnoreCase("true")) {
232	>	byte[] seedBytes = java.security.SecureRandom.getSeed(8);
233	>	long s = (long)(seedBytes[0]) & 0xffL;
234	>	for (int i = 1; i < 8; ++i)
235	>	s = (s << 8) | ((long)(seedBytes[i]) & 0xffL);
236	>	return s;
237	>	}
238	>	return (mix64(System.currentTimeMillis()) ^
239	>	mix64(System.nanoTime()));
240		}
241
242	+	// IllegalArgumentException messages
243	+	static final String BadBound = "bound must be positive";
244	+	static final String BadRange = "bound must be greater than origin";
245	+	static final String BadSize  = "size must be non-negative";
246	+
247		/*
248		* Internal versions of nextX methods used by streams, as well as
249		* the public nextX(origin, bound) methods.  These exist mainly to
#	Line 362 | Line 319 | public class SplittableRandom {
319		int r = mix32(nextSeed());
320		if (origin < bound) {
321		int n = bound - origin, m = n - 1;
322	<	if ((n & m) == 0L)
322	>	if ((n & m) == 0)
323		r = (r & m) + origin;
324		else if (n > 0) {
325		for (int u = r >>> 1;
#	Line 401 | Line 358 | public class SplittableRandom {
358		/**
359		* Creates a new SplittableRandom instance using the specified
360		* initial seed. SplittableRandom instances created with the same
361	<	* seed generate identical sequences of values.
361	>	* seed in the same program generate identical sequences of values.
362		*
363		* @param seed the initial seed
364		*/
365		public SplittableRandom(long seed) {
366	<	this(seed, 0);
366	>	this(seed, GOLDEN_GAMMA);
367		}
368
369		/**
#	Line 415 | Line 372 | public class SplittableRandom {
372		* of those of any other instances in the current program; and
373		* may, and typically does, vary across program invocations.
374		*/
375	<	public SplittableRandom() {
376	<	this(nextDefaultSeed(), GAMMA_GAMMA);
375	>	public SplittableRandom() { // emulate defaultGen.split()
376	>	long s = defaultGen.getAndAdd(2 * GOLDEN_GAMMA);
377	>	this.seed = mix64(s);
378	>	this.gamma = mixGamma(s + GOLDEN_GAMMA);
379		}
380
381		/**
#	Line 434 | Line 393 | public class SplittableRandom {
393		* @return the new SplittableRandom instance
394		*/
395		public SplittableRandom split() {
396	<	return new SplittableRandom(nextSeed(), nextSplit);
396	>	return new SplittableRandom(nextLong(), mixGamma(nextSeed()));
397		}
398
399		/**
#	Line 450 | Line 409 | public class SplittableRandom {
409		* Returns a pseudorandom {@code int} value between zero (inclusive)
410		* and the specified bound (exclusive).
411		*
412	<	* @param bound the bound on the random number to be returned.  Must be
454	<	*        positive.
412	>	* @param bound the upper bound (exclusive).  Must be positive.
413		* @return a pseudorandom {@code int} value between zero
414	<	*         (inclusive) and the bound (exclusive).
415	<	* @throws IllegalArgumentException if the bound is less than zero
414	>	*         (inclusive) and the bound (exclusive)
415	>	* @throws IllegalArgumentException if {@code bound} is not positive
416		*/
417		public int nextInt(int bound) {
418		if (bound <= 0)
419	<	throw new IllegalArgumentException("bound must be positive");
419	>	throw new IllegalArgumentException(BadBound);
420		// Specialize internalNextInt for origin 0
421		int r = mix32(nextSeed());
422		int m = bound - 1;
423	<	if ((bound & m) == 0L) // power of two
423	>	if ((bound & m) == 0) // power of two
424		r &= m;
425		else { // reject over-represented candidates
426		for (int u = r >>> 1;
#	Line 480 | Line 438 | public class SplittableRandom {
438		* @param origin the least value returned
439		* @param bound the upper bound (exclusive)
440		* @return a pseudorandom {@code int} value between the origin
441	<	*         (inclusive) and the bound (exclusive).
441	>	*         (inclusive) and the bound (exclusive)
442		* @throws IllegalArgumentException if {@code origin} is greater than
443		*         or equal to {@code bound}
444		*/
445		public int nextInt(int origin, int bound) {
446		if (origin >= bound)
447	<	throw new IllegalArgumentException("bound must be greater than origin");
447	>	throw new IllegalArgumentException(BadRange);
448		return internalNextInt(origin, bound);
449		}
450
#	Line 503 | Line 461 | public class SplittableRandom {
461		* Returns a pseudorandom {@code long} value between zero (inclusive)
462		* and the specified bound (exclusive).
463		*
464	<	* @param bound the bound on the random number to be returned.  Must be
507	<	*        positive.
464	>	* @param bound the upper bound (exclusive).  Must be positive.
465		* @return a pseudorandom {@code long} value between zero
466	<	*         (inclusive) and the bound (exclusive).
467	<	* @throws IllegalArgumentException if {@code bound} is less than zero
466	>	*         (inclusive) and the bound (exclusive)
467	>	* @throws IllegalArgumentException if {@code bound} is not positive
468		*/
469		public long nextLong(long bound) {
470		if (bound <= 0)
471	<	throw new IllegalArgumentException("bound must be positive");
471	>	throw new IllegalArgumentException(BadBound);
472		// Specialize internalNextLong for origin 0
473		long r = mix64(nextSeed());
474		long m = bound - 1;
#	Line 533 | Line 490 | public class SplittableRandom {
490		* @param origin the least value returned
491		* @param bound the upper bound (exclusive)
492		* @return a pseudorandom {@code long} value between the origin
493	<	*         (inclusive) and the bound (exclusive).
493	>	*         (inclusive) and the bound (exclusive)
494		* @throws IllegalArgumentException if {@code origin} is greater than
495		*         or equal to {@code bound}
496		*/
497		public long nextLong(long origin, long bound) {
498		if (origin >= bound)
499	<	throw new IllegalArgumentException("bound must be greater than origin");
499	>	throw new IllegalArgumentException(BadRange);
500		return internalNextLong(origin, bound);
501		}
502
#	Line 548 | Line 505 | public class SplittableRandom {
505		* (inclusive) and one (exclusive).
506		*
507		* @return a pseudorandom {@code double} value between zero
508	<	* (inclusive) and one (exclusive)
508	>	*         (inclusive) and one (exclusive)
509		*/
510		public double nextDouble() {
511	<	return (nextLong() >>> 11) * DOUBLE_UNIT;
511	>	return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT;
512		}
513
514		/**
515		* Returns a pseudorandom {@code double} value between 0.0
516		* (inclusive) and the specified bound (exclusive).
517		*
518	<	* @param bound the bound on the random number to be returned.  Must be
562	<	*        positive.
518	>	* @param bound the upper bound (exclusive).  Must be positive.
519		* @return a pseudorandom {@code double} value between zero
520	<	*         (inclusive) and the bound (exclusive).
521	<	* @throws IllegalArgumentException if {@code bound} is less than zero
520	>	*         (inclusive) and the bound (exclusive)
521	>	* @throws IllegalArgumentException if {@code bound} is not positive
522		*/
523		public double nextDouble(double bound) {
524		if (!(bound > 0.0))
525	<	throw new IllegalArgumentException("bound must be positive");
526	<	double result = nextDouble() * bound;
525	>	throw new IllegalArgumentException(BadBound);
526	>	double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound;
527		return (result < bound) ?  result : // correct for rounding
528		Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
529		}
#	Line 577 | Line 533 | public class SplittableRandom {
533		* origin (inclusive) and bound (exclusive).
534		*
535		* @param origin the least value returned
536	<	* @param bound the upper bound
536	>	* @param bound the upper bound (exclusive)
537		* @return a pseudorandom {@code double} value between the origin
538	<	*         (inclusive) and the bound (exclusive).
538	>	*         (inclusive) and the bound (exclusive)
539		* @throws IllegalArgumentException if {@code origin} is greater than
540		*         or equal to {@code bound}
541		*/
542		public double nextDouble(double origin, double bound) {
543		if (!(origin < bound))
544	<	throw new IllegalArgumentException("bound must be greater than origin");
544	>	throw new IllegalArgumentException(BadRange);
545		return internalNextDouble(origin, bound);
546		}
547
548	+	/**
549	+	* Returns a pseudorandom {@code boolean} value.
550	+	*
551	+	* @return a pseudorandom {@code boolean} value
552	+	*/
553	+	public boolean nextBoolean() {
554	+	return mix32(nextSeed()) < 0;
555	+	}
556	+
557		// stream methods, coded in a way intended to better isolate for
558		// maintenance purposes the small differences across forms.
559
560		/**
561	<	* Returns a stream producing the given {@code streamSize} number of
562	<	* pseudorandom {@code int} values.
561	>	* Returns a stream producing the given {@code streamSize} number
562	>	* of pseudorandom {@code int} values from this generator and/or
563	>	* one split from it.
564		*
565		* @param streamSize the number of values to generate
566		* @return a stream of pseudorandom {@code int} values
#	Line 603 | Line 569 | public class SplittableRandom {
569		*/
570		public IntStream ints(long streamSize) {
571		if (streamSize < 0L)
572	<	throw new IllegalArgumentException("negative Stream size");
572	>	throw new IllegalArgumentException(BadSize);
573		return StreamSupport.intStream
574		(new RandomIntsSpliterator
575		(this, 0L, streamSize, Integer.MAX_VALUE, 0),
#	Line 612 | Line 578 | public class SplittableRandom {
578
579		/**
580		* Returns an effectively unlimited stream of pseudorandom {@code int}
581	<	* values
581	>	* values from this generator and/or one split from it.
582		*
583		* @implNote This method is implemented to be equivalent to {@code
584		* ints(Long.MAX_VALUE)}.
#	Line 627 | Line 593 | public class SplittableRandom {
593		}
594
595		/**
596	<	* Returns a stream producing the given {@code streamSize} number of
597	<	* pseudorandom {@code int} values, each conforming to the given
598	<	* origin and bound.
596	>	* Returns a stream producing the given {@code streamSize} number
597	>	* of pseudorandom {@code int} values from this generator and/or one split
598	>	* from it; each value conforms to the given origin (inclusive) and bound
599	>	* (exclusive).
600		*
601		* @param streamSize the number of values to generate
602	<	* @param randomNumberOrigin the origin of each random value
603	<	* @param randomNumberBound the bound of each random value
602	>	* @param randomNumberOrigin the origin (inclusive) of each random value
603	>	* @param randomNumberBound the bound (exclusive) of each random value
604		* @return a stream of pseudorandom {@code int} values,
605	<	*         each with the given origin and bound.
605	>	*         each with the given origin (inclusive) and bound (exclusive)
606		* @throws IllegalArgumentException if {@code streamSize} is
607		*         less than zero, or {@code randomNumberOrigin}
608		*         is greater than or equal to {@code randomNumberBound}
#	Line 643 | Line 610 | public class SplittableRandom {
610		public IntStream ints(long streamSize, int randomNumberOrigin,
611		int randomNumberBound) {
612		if (streamSize < 0L)
613	<	throw new IllegalArgumentException("negative Stream size");
613	>	throw new IllegalArgumentException(BadSize);
614		if (randomNumberOrigin >= randomNumberBound)
615	<	throw new IllegalArgumentException("bound must be greater than origin");
615	>	throw new IllegalArgumentException(BadRange);
616		return StreamSupport.intStream
617		(new RandomIntsSpliterator
618		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 654 | Line 621 | public class SplittableRandom {
621
622		/**
623		* Returns an effectively unlimited stream of pseudorandom {@code
624	<	* int} values, each conforming to the given origin and bound.
624	>	* int} values from this generator and/or one split from it; each value
625	>	* conforms to the given origin (inclusive) and bound (exclusive).
626		*
627		* @implNote This method is implemented to be equivalent to {@code
628		* ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
629		*
630	<	* @param randomNumberOrigin the origin of each random value
631	<	* @param randomNumberBound the bound of each random value
630	>	* @param randomNumberOrigin the origin (inclusive) of each random value
631	>	* @param randomNumberBound the bound (exclusive) of each random value
632		* @return a stream of pseudorandom {@code int} values,
633	<	*         each with the given origin and bound.
633	>	*         each with the given origin (inclusive) and bound (exclusive)
634		* @throws IllegalArgumentException if {@code randomNumberOrigin}
635		*         is greater than or equal to {@code randomNumberBound}
636		*/
637		public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
638		if (randomNumberOrigin >= randomNumberBound)
639	<	throw new IllegalArgumentException("bound must be greater than origin");
639	>	throw new IllegalArgumentException(BadRange);
640		return StreamSupport.intStream
641		(new RandomIntsSpliterator
642		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 676 | Line 644 | public class SplittableRandom {
644		}
645
646		/**
647	<	* Returns a stream producing the given {@code streamSize} number of
648	<	* pseudorandom {@code long} values.
647	>	* Returns a stream producing the given {@code streamSize} number
648	>	* of pseudorandom {@code long} values from this generator and/or
649	>	* one split from it.
650		*
651		* @param streamSize the number of values to generate
652		* @return a stream of pseudorandom {@code long} values
#	Line 686 | Line 655 | public class SplittableRandom {
655		*/
656		public LongStream longs(long streamSize) {
657		if (streamSize < 0L)
658	<	throw new IllegalArgumentException("negative Stream size");
658	>	throw new IllegalArgumentException(BadSize);
659		return StreamSupport.longStream
660		(new RandomLongsSpliterator
661		(this, 0L, streamSize, Long.MAX_VALUE, 0L),
#	Line 694 | Line 663 | public class SplittableRandom {
663		}
664
665		/**
666	<	* Returns an effectively unlimited stream of pseudorandom {@code long}
667	<	* values.
666	>	* Returns an effectively unlimited stream of pseudorandom {@code
667	>	* long} values from this generator and/or one split from it.
668		*
669		* @implNote This method is implemented to be equivalent to {@code
670		* longs(Long.MAX_VALUE)}.
#	Line 711 | Line 680 | public class SplittableRandom {
680
681		/**
682		* Returns a stream producing the given {@code streamSize} number of
683	<	* pseudorandom {@code long} values, each conforming to the
684	<	* given origin and bound.
683	>	* pseudorandom {@code long} values from this generator and/or one split
684	>	* from it; each value conforms to the given origin (inclusive) and bound
685	>	* (exclusive).
686		*
687		* @param streamSize the number of values to generate
688	<	* @param randomNumberOrigin the origin of each random value
689	<	* @param randomNumberBound the bound of each random value
688	>	* @param randomNumberOrigin the origin (inclusive) of each random value
689	>	* @param randomNumberBound the bound (exclusive) of each random value
690		* @return a stream of pseudorandom {@code long} values,
691	<	*         each with the given origin and bound.
691	>	*         each with the given origin (inclusive) and bound (exclusive)
692		* @throws IllegalArgumentException if {@code streamSize} is
693		*         less than zero, or {@code randomNumberOrigin}
694		*         is greater than or equal to {@code randomNumberBound}
#	Line 726 | Line 696 | public class SplittableRandom {
696		public LongStream longs(long streamSize, long randomNumberOrigin,
697		long randomNumberBound) {
698		if (streamSize < 0L)
699	<	throw new IllegalArgumentException("negative Stream size");
699	>	throw new IllegalArgumentException(BadSize);
700		if (randomNumberOrigin >= randomNumberBound)
701	<	throw new IllegalArgumentException("bound must be greater than origin");
701	>	throw new IllegalArgumentException(BadRange);
702		return StreamSupport.longStream
703		(new RandomLongsSpliterator
704		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 737 | Line 707 | public class SplittableRandom {
707
708		/**
709		* Returns an effectively unlimited stream of pseudorandom {@code
710	<	* long} values, each conforming to the given origin and bound.
710	>	* long} values from this generator and/or one split from it; each value
711	>	* conforms to the given origin (inclusive) and bound (exclusive).
712		*
713		* @implNote This method is implemented to be equivalent to {@code
714		* longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
715		*
716	<	* @param randomNumberOrigin the origin of each random value
717	<	* @param randomNumberBound the bound of each random value
716	>	* @param randomNumberOrigin the origin (inclusive) of each random value
717	>	* @param randomNumberBound the bound (exclusive) of each random value
718		* @return a stream of pseudorandom {@code long} values,
719	<	*         each with the given origin and bound.
719	>	*         each with the given origin (inclusive) and bound (exclusive)
720		* @throws IllegalArgumentException if {@code randomNumberOrigin}
721		*         is greater than or equal to {@code randomNumberBound}
722		*/
723		public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
724		if (randomNumberOrigin >= randomNumberBound)
725	<	throw new IllegalArgumentException("bound must be greater than origin");
725	>	throw new IllegalArgumentException(BadRange);
726		return StreamSupport.longStream
727		(new RandomLongsSpliterator
728		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 760 | Line 731 | public class SplittableRandom {
731
732		/**
733		* Returns a stream producing the given {@code streamSize} number of
734	<	* pseudorandom {@code double} values, each between zero
735	<	* (inclusive) and one (exclusive).
734	>	* pseudorandom {@code double} values from this generator and/or one split
735	>	* from it; each value is between zero (inclusive) and one (exclusive).
736		*
737		* @param streamSize the number of values to generate
738		* @return a stream of {@code double} values
#	Line 770 | Line 741 | public class SplittableRandom {
741		*/
742		public DoubleStream doubles(long streamSize) {
743		if (streamSize < 0L)
744	<	throw new IllegalArgumentException("negative Stream size");
744	>	throw new IllegalArgumentException(BadSize);
745		return StreamSupport.doubleStream
746		(new RandomDoublesSpliterator
747		(this, 0L, streamSize, Double.MAX_VALUE, 0.0),
#	Line 779 | Line 750 | public class SplittableRandom {
750
751		/**
752		* Returns an effectively unlimited stream of pseudorandom {@code
753	<	* double} values, each between zero (inclusive) and one
754	<	* (exclusive).
753	>	* double} values from this generator and/or one split from it; each value
754	>	* is between zero (inclusive) and one (exclusive).
755		*
756		* @implNote This method is implemented to be equivalent to {@code
757		* doubles(Long.MAX_VALUE)}.
#	Line 796 | Line 767 | public class SplittableRandom {
767
768		/**
769		* Returns a stream producing the given {@code streamSize} number of
770	<	* pseudorandom {@code double} values, each conforming to the
771	<	* given origin and bound.
770	>	* pseudorandom {@code double} values from this generator and/or one split
771	>	* from it; each value conforms to the given origin (inclusive) and bound
772	>	* (exclusive).
773		*
774		* @param streamSize the number of values to generate
775	<	* @param randomNumberOrigin the origin of each random value
776	<	* @param randomNumberBound the bound of each random value
775	>	* @param randomNumberOrigin the origin (inclusive) of each random value
776	>	* @param randomNumberBound the bound (exclusive) of each random value
777		* @return a stream of pseudorandom {@code double} values,
778	<	* each with the given origin and bound.
778	>	*         each with the given origin (inclusive) and bound (exclusive)
779		* @throws IllegalArgumentException if {@code streamSize} is
780	<	* less than zero.
780	>	*         less than zero
781		* @throws IllegalArgumentException if {@code randomNumberOrigin}
782		*         is greater than or equal to {@code randomNumberBound}
783		*/
784		public DoubleStream doubles(long streamSize, double randomNumberOrigin,
785		double randomNumberBound) {
786		if (streamSize < 0L)
787	<	throw new IllegalArgumentException("negative Stream size");
787	>	throw new IllegalArgumentException(BadSize);
788		if (!(randomNumberOrigin < randomNumberBound))
789	<	throw new IllegalArgumentException("bound must be greater than origin");
789	>	throw new IllegalArgumentException(BadRange);
790		return StreamSupport.doubleStream
791		(new RandomDoublesSpliterator
792		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 823 | Line 795 | public class SplittableRandom {
795
796		/**
797		* Returns an effectively unlimited stream of pseudorandom {@code
798	<	* double} values, each conforming to the given origin and bound.
798	>	* double} values from this generator and/or one split from it; each value
799	>	* conforms to the given origin (inclusive) and bound (exclusive).
800		*
801		* @implNote This method is implemented to be equivalent to {@code
802		* doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
803		*
804	<	* @param randomNumberOrigin the origin of each random value
805	<	* @param randomNumberBound the bound of each random value
804	>	* @param randomNumberOrigin the origin (inclusive) of each random value
805	>	* @param randomNumberBound the bound (exclusive) of each random value
806		* @return a stream of pseudorandom {@code double} values,
807	<	* each with the given origin and bound.
807	>	*         each with the given origin (inclusive) and bound (exclusive)
808		* @throws IllegalArgumentException if {@code randomNumberOrigin}
809		*         is greater than or equal to {@code randomNumberBound}
810		*/
811		public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
812		if (!(randomNumberOrigin < randomNumberBound))
813	<	throw new IllegalArgumentException("bound must be greater than origin");
813	>	throw new IllegalArgumentException(BadRange);
814		return StreamSupport.doubleStream
815		(new RandomDoublesSpliterator
816		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 852 | Line 825 | public class SplittableRandom {
825		* approach. The long and double versions of this class are
826		* identical except for types.
827		*/
828	<	static class RandomIntsSpliterator implements Spliterator.OfInt {
828	>	static final class RandomIntsSpliterator implements Spliterator.OfInt {
829		final SplittableRandom rng;
830		long index;
831		final long fence;
#	Line 895 | Line 868 | public class SplittableRandom {
868		long i = index, f = fence;
869		if (i < f) {
870		index = f;
871	+	SplittableRandom r = rng;
872		int o = origin, b = bound;
873		do {
874	<	consumer.accept(rng.internalNextInt(o, b));
874	>	consumer.accept(r.internalNextInt(o, b));
875		} while (++i < f);
876		}
877		}
#	Line 906 | Line 880 | public class SplittableRandom {
880		/**
881		* Spliterator for long streams.
882		*/
883	<	static class RandomLongsSpliterator implements Spliterator.OfLong {
883	>	static final class RandomLongsSpliterator implements Spliterator.OfLong {
884		final SplittableRandom rng;
885		long index;
886		final long fence;
#	Line 949 | Line 923 | public class SplittableRandom {
923		long i = index, f = fence;
924		if (i < f) {
925		index = f;
926	+	SplittableRandom r = rng;
927		long o = origin, b = bound;
928		do {
929	<	consumer.accept(rng.internalNextLong(o, b));
929	>	consumer.accept(r.internalNextLong(o, b));
930		} while (++i < f);
931		}
932		}
#	Line 961 | Line 936 | public class SplittableRandom {
936		/**
937		* Spliterator for double streams.
938		*/
939	<	static class RandomDoublesSpliterator implements Spliterator.OfDouble {
939	>	static final class RandomDoublesSpliterator implements Spliterator.OfDouble {
940		final SplittableRandom rng;
941		long index;
942		final long fence;
#	Line 1004 | Line 979 | public class SplittableRandom {
979		long i = index, f = fence;
980		if (i < f) {
981		index = f;
982	+	SplittableRandom r = rng;
983		double o = origin, b = bound;
984		do {
985	<	consumer.accept(rng.internalNextDouble(o, b));
985	>	consumer.accept(r.internalNextDouble(o, b));
986		} while (++i < f);
987		}
988		}
989		}
990
991		}
1016	–

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