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Comparing jsr166/src/main/java/util/SplittableRandom.java (file contents):
Revision 1.12 by dl, Sun Jul 21 14:02:23 2013 UTC vs.
Revision 1.33 by dl, Sat Nov 12 00:12:05 2016 UTC

#	Line 25 | Line 25
25
26		package java.util;
27
28	–	import java.security.SecureRandom;
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;
34	<	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 54 | Line 52 | import java.util.stream.DoubleStream;
52		* types and ranges, but similar properties are expected to hold, at
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>. </li>
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 73 | 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 {
85	<
86	<	/*
87	<	* File organization: First the non-public methods that constitute
88	<	* the main algorithm, then the main public methods, followed by
89	<	* some custom spliterator classes needed for stream methods.
90	<	*
91	<	* Credits: Primary algorithm and code by Guy Steele.  Stream
92	<	* support methods by Doug Lea.  Documentation jointly produced
93	<	* with additional help from Brian Goetz.
94	<	*/
89	>	public final class SplittableRandom {
90
91		/*
92		* Implementation Overview.
#	Line 99 | 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
107	<	* return this value, but instead the results of bit-mixing
108	<	* transformations that produce more uniformly distributed
109	<	* sequences.
110	<	*
111	<	* "George" is the otherwise nameless (because it cannot be
112	<	* represented) prime number 2^64+13. Using a prime number larger
113	<	* than can fit in a long ensures that all possible long values
114	<	* can occur, plus 13 others that just get skipped over when they
115	<	* are encountered; see method addGammaModGeorge. For this to
116	<	* work, initial gamma values must be at least 13.
117	<	*
118	<	* The value of gamma differs for each instance across a series of
119	<	* splits, and is generated using a slightly stripped-down variant
120	<	* of the same algorithm, but operating across calls to split(),
121	<	* not calls to nextSeed(): Each instance carries the state of
122	<	* this generator as nextSplit, and uses mix64(nextSplit) as its
123	<	* own gamma value. Computations of gammas themselves use a fixed
124	<	* constant as the second argument to the addGammaModGeorge
125	<	* function, GAMMA_GAMMA. The value of GAMMA_GAMMA is arbitrary
126	<	* (except must be at least 13), but because it serves as the base
127	<	* of split sequences, should be subject to validation of
128	<	* consequent random number quality metrics.
129	<	*
130	<	* The mix64 bit-mixing function called by nextLong and other
131	<	* methods computes the same value as the "64-bit finalizer"
132	<	* function in Austin Appleby's MurmurHash3 algorithm.  See
133	<	* http://code.google.com/p/smhasher/wiki/MurmurHash3 , which
134	<	* comments: "The constants for the finalizers were generated by a
135	<	* simple simulated-annealing algorithm, and both avalanche all
136	<	* bits of 'h' to within 0.25% bias." It also appears to work to
137	<	* use instead any of the variants proposed by David Stafford at
138	<	* http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html
139	<	* but these variants have not yet been tested as thoroughly
140	<	* in the context of the implementation of SplittableRandom.
141	<	*
142	<	* The mix32 function used for nextInt just consists of two of the
143	<	* five lines of mix64; avalanche testing shows that the 64-bit result
144	<	* has its top 32 bits avalanched well, though not the bottom 32 bits.
145	<	* DieHarder tests show that it is adequate for generating one
146	<	* random int from the 64-bit result of nextSeed.
147	<	*
148	<	* Support for the default (no-argument) constructor relies on an
149	<	* AtomicLong (defaultSeedGenerator) to help perform the
150	<	* equivalent of a split of a statically constructed
151	<	* SplittableRandom. Unlike other cases, this split must be
152	<	* performed in a thread-safe manner. We use
153	<	* AtomicLong.compareAndSet as the (typically) most efficient
154	<	* mechanism. To bootstrap, we start off using a SecureRandom
155	<	* initial default seed, and update using a fixed
156	<	* DEFAULT_SEED_GAMMA. The default constructor uses GAMMA_GAMMA,
157	<	* not 0, for its splitSeed argument (addGammaModGeorge(0,
158	<	* GAMMA_GAMMA) == GAMMA_GAMMA) to reflect that each is split from
159	<	* this root generator, even though the root is not explicitly
160	<	* represented as a SplittableRandom.
161	<	*/
162	<
163	<	/**
164	<	* The value for producing new gamma values. Must be greater or
165	<	* equal to 13. Otherwise, the value is arbitrary subject to
166	<	* validation of the resulting statistical quality of splits.
167	<	*/
168	<	private static final long GAMMA_GAMMA = 0xF2281E2DBA6606F3L;
169	<
170	<	/**
171	<	* The seed update value for default constructors.  Must be
172	<	* greater or equal to 13. Otherwise, the value is arbitrary.
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		*/
174	–	private static final long DEFAULT_SEED_GAMMA = 0xBD24B73A95FB84D9L;
156
157		/**
158	<	* The value 13 with 64bit sign bit set. Used in the signed
159	<	* comparison in addGammaModGeorge.
158	>	* The golden ratio scaled to 64bits, used as the initial gamma
159	>	* value for (unsplit) SplittableRandoms.
160		*/
161	<	private static final long BOTTOM13 = 0x800000000000000DL;
161	>	private static final long GOLDEN_GAMMA = 0x9e3779b97f4a7c15L;
162
163		/**
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 double DOUBLE_UNIT = 1.0 / (1L << 53);
187	<
188	<	/**
189	<	* The next seed for default constructors.
190	<	*/
191	<	private static final AtomicLong defaultSeedGenerator =
192	<	new AtomicLong(getInitialDefaultSeed());
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.
207	<	*/
208	<	private final long nextSplit;
209	<
210	<	/**
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	<	* Because Java comparison operators are signed, we implement this
221	<	* by conceptually offsetting seed values downwards by 2^63, so
222	<	* 0..13 is represented as Long.MIN_VALUE..BOTTOM13.
223	<	*
224	<	* @param s a seed value, viewed as a signed long
225	<	* @param g a gamma value, 13 <= g (as unsigned)
180	>	* Internal constructor used by all others except default constructor.
181		*/
182	<	private static long addGammaModGeorge(long s, long g) {
183	<	long p = s + g;
184	<	return (p >= s) ? p : ((p >= BOTTOM13) ? p  : p + g) - 13L;
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.
234	<	* 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);
240	<	z *= 0xc4ceb9fe1a85ec53L;
241	<	z ^= (z >>> 33);
242	<	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.
247	<	* 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;
252	<	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
257	<	* method split. Establishes the initial seed for this instance,
258	<	* and uses the given splitSeed to establish gamma, as well as the
259	<	* nextSplit to use by this instance. The loop to skip ineligible
260	<	* 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);
268	<	} while (g >= 0L && g < 13L);
269	<	this.gamma = g;
270	<	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.
275	<	* See above for explanation.
216	>	* Adds gamma to seed.
217		*/
218		private long nextSeed() {
219	<	return seed = addGammaModGeorge(seed, gamma);
279	<	}
280	<
281	<	/**
282	<	* Atomically updates and returns next seed for default constructor.
283	<	*/
284	<	private static long nextDefaultSeed() {
285	<	long oldSeed, newSeed;
286	<	do {
287	<	oldSeed = defaultSeedGenerator.get();
288	<	newSeed = addGammaModGeorge(oldSeed, DEFAULT_SEED_GAMMA);
289	<	} while (!defaultSeedGenerator.compareAndSet(oldSeed, newSeed));
290	<	return mix64(newSeed);
219	>	return seed += gamma;
220		}
221
222	<	/**
223	<	* Returns an initial default seed.
224	<	*/
225	<	private static long getInitialDefaultSeed() {
226	<	byte[] seedBytes = java.security.SecureRandom.getSeed(8);
227	<	long s = (long)(seedBytes[0]) & 0xffL;
228	<	for (int i = 1; i < 8; ++i)
229	<	s = (s << 8) | ((long)(seedBytes[i]) & 0xffL);
230	<	return s;
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 376 | 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 420 | Line 365 | public class SplittableRandom {
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 429 | 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(2 * GOLDEN_GAMMA);
379	>	this.seed = mix64(s);
380	>	this.gamma = mixGamma(s + GOLDEN_GAMMA);
381		}
382
383		/**
#	Line 448 | 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 464 | 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
468	<	*        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
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 500 | Line 446 | public class SplittableRandom {
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 517 | 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
521	<	*        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
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 553 | Line 498 | public class SplittableRandom {
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 562 | 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 (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT;
#	Line 572 | Line 517 | public class SplittableRandom {
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
576	<	*        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
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");
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		}
532
533	+	/**
534	+	* Generates a pseudorandom number with the indicated number of
535	+	* bits. Unlike in superclass @{link Random}, this method is never
536	+	* internally called or used by any other publicly accessible
537	+	* method.
538	+	*
539	+	* @param  bits random bits
540	+	* @return the next pseudorandom value from this random number
541	+	*         generator's sequence
542	+	*/
543	+	protected int next(int bits) {
544	+	return (int)(nextLong() >>> (64 - bits));
545	+	}
546	+
547		/**
548		* Returns a pseudorandom {@code double} value between the specified
549		* origin (inclusive) and bound (exclusive).
550		*
551		* @param origin the least value returned
552	<	* @param bound the upper bound
552	>	* @param bound the upper bound (exclusive)
553		* @return a pseudorandom {@code double} value between the origin
554		*         (inclusive) and the bound (exclusive)
555		* @throws IllegalArgumentException if {@code origin} is greater than
#	Line 599 | Line 557 | public class SplittableRandom {
557		*/
558		public double nextDouble(double origin, double bound) {
559		if (!(origin < bound))
560	<	throw new IllegalArgumentException("bound must be greater than origin");
560	>	throw new IllegalArgumentException(BAD_RANGE);
561		return internalNextDouble(origin, bound);
562		}
563
#	Line 616 | Line 574 | public class SplittableRandom {
574		// maintenance purposes the small differences across forms.
575
576		/**
577	<	* Returns a stream producing the given {@code streamSize} number of
578	<	* pseudorandom {@code int} values.
577	>	* Returns a stream producing the given {@code streamSize} number
578	>	* of pseudorandom {@code int} values from this generator and/or
579	>	* one split from it.
580		*
581		* @param streamSize the number of values to generate
582		* @return a stream of pseudorandom {@code int} values
#	Line 626 | Line 585 | public class SplittableRandom {
585		*/
586		public IntStream ints(long streamSize) {
587		if (streamSize < 0L)
588	<	throw new IllegalArgumentException("negative Stream size");
588	>	throw new IllegalArgumentException(BAD_SIZE);
589		return StreamSupport.intStream
590		(new RandomIntsSpliterator
591		(this, 0L, streamSize, Integer.MAX_VALUE, 0),
#	Line 635 | Line 594 | public class SplittableRandom {
594
595		/**
596		* Returns an effectively unlimited stream of pseudorandom {@code int}
597	<	* values.
597	>	* values from this generator and/or one split from it.
598		*
599		* @implNote This method is implemented to be equivalent to {@code
600		* ints(Long.MAX_VALUE)}.
#	Line 650 | Line 609 | public class SplittableRandom {
609		}
610
611		/**
612	<	* Returns a stream producing the given {@code streamSize} number of
613	<	* pseudorandom {@code int} values, each conforming to the given
614	<	* origin and bound.
612	>	* Returns a stream producing the given {@code streamSize} number
613	>	* of pseudorandom {@code int} values from this generator and/or one split
614	>	* from it; each value conforms to the given origin (inclusive) and bound
615	>	* (exclusive).
616		*
617		* @param streamSize the number of values to generate
618	<	* @param randomNumberOrigin the origin of each random value
619	<	* @param randomNumberBound the bound of each random value
618	>	* @param randomNumberOrigin the origin (inclusive) of each random value
619	>	* @param randomNumberBound the bound (exclusive) of each random value
620		* @return a stream of pseudorandom {@code int} values,
621	<	*         each with the given origin and bound
621	>	*         each with the given origin (inclusive) and bound (exclusive)
622		* @throws IllegalArgumentException if {@code streamSize} is
623		*         less than zero, or {@code randomNumberOrigin}
624		*         is greater than or equal to {@code randomNumberBound}
#	Line 666 | Line 626 | public class SplittableRandom {
626		public IntStream ints(long streamSize, int randomNumberOrigin,
627		int randomNumberBound) {
628		if (streamSize < 0L)
629	<	throw new IllegalArgumentException("negative Stream size");
629	>	throw new IllegalArgumentException(BAD_SIZE);
630		if (randomNumberOrigin >= randomNumberBound)
631	<	throw new IllegalArgumentException("bound must be greater than origin");
631	>	throw new IllegalArgumentException(BAD_RANGE);
632		return StreamSupport.intStream
633		(new RandomIntsSpliterator
634		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 677 | Line 637 | public class SplittableRandom {
637
638		/**
639		* Returns an effectively unlimited stream of pseudorandom {@code
640	<	* int} values, each conforming to the given origin and bound.
640	>	* int} values from this generator and/or one split from it; each value
641	>	* conforms to the given origin (inclusive) and bound (exclusive).
642		*
643		* @implNote This method is implemented to be equivalent to {@code
644		* ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
645		*
646	<	* @param randomNumberOrigin the origin of each random value
647	<	* @param randomNumberBound the bound of each random value
646	>	* @param randomNumberOrigin the origin (inclusive) of each random value
647	>	* @param randomNumberBound the bound (exclusive) of each random value
648		* @return a stream of pseudorandom {@code int} values,
649	<	*         each with the given origin and bound
649	>	*         each with the given origin (inclusive) and bound (exclusive)
650		* @throws IllegalArgumentException if {@code randomNumberOrigin}
651		*         is greater than or equal to {@code randomNumberBound}
652		*/
653		public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
654		if (randomNumberOrigin >= randomNumberBound)
655	<	throw new IllegalArgumentException("bound must be greater than origin");
655	>	throw new IllegalArgumentException(BAD_RANGE);
656		return StreamSupport.intStream
657		(new RandomIntsSpliterator
658		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 699 | Line 660 | public class SplittableRandom {
660		}
661
662		/**
663	<	* Returns a stream producing the given {@code streamSize} number of
664	<	* pseudorandom {@code long} values.
663	>	* Returns a stream producing the given {@code streamSize} number
664	>	* of pseudorandom {@code long} values from this generator and/or
665	>	* one split from it.
666		*
667		* @param streamSize the number of values to generate
668		* @return a stream of pseudorandom {@code long} values
#	Line 709 | Line 671 | public class SplittableRandom {
671		*/
672		public LongStream longs(long streamSize) {
673		if (streamSize < 0L)
674	<	throw new IllegalArgumentException("negative Stream size");
674	>	throw new IllegalArgumentException(BAD_SIZE);
675		return StreamSupport.longStream
676		(new RandomLongsSpliterator
677		(this, 0L, streamSize, Long.MAX_VALUE, 0L),
#	Line 717 | Line 679 | public class SplittableRandom {
679		}
680
681		/**
682	<	* Returns an effectively unlimited stream of pseudorandom {@code long}
683	<	* values.
682	>	* Returns an effectively unlimited stream of pseudorandom {@code
683	>	* long} values from this generator and/or one split from it.
684		*
685		* @implNote This method is implemented to be equivalent to {@code
686		* longs(Long.MAX_VALUE)}.
#	Line 734 | Line 696 | public class SplittableRandom {
696
697		/**
698		* Returns a stream producing the given {@code streamSize} number of
699	<	* pseudorandom {@code long} values, each conforming to the
700	<	* given origin and bound.
699	>	* pseudorandom {@code long} values from this generator and/or one split
700	>	* from it; each value conforms to the given origin (inclusive) and bound
701	>	* (exclusive).
702		*
703		* @param streamSize the number of values to generate
704	<	* @param randomNumberOrigin the origin of each random value
705	<	* @param randomNumberBound the bound of each random value
704	>	* @param randomNumberOrigin the origin (inclusive) of each random value
705	>	* @param randomNumberBound the bound (exclusive) of each random value
706		* @return a stream of pseudorandom {@code long} values,
707	<	*         each with the given origin and bound
707	>	*         each with the given origin (inclusive) and bound (exclusive)
708		* @throws IllegalArgumentException if {@code streamSize} is
709		*         less than zero, or {@code randomNumberOrigin}
710		*         is greater than or equal to {@code randomNumberBound}
#	Line 749 | Line 712 | public class SplittableRandom {
712		public LongStream longs(long streamSize, long randomNumberOrigin,
713		long randomNumberBound) {
714		if (streamSize < 0L)
715	<	throw new IllegalArgumentException("negative Stream size");
715	>	throw new IllegalArgumentException(BAD_SIZE);
716		if (randomNumberOrigin >= randomNumberBound)
717	<	throw new IllegalArgumentException("bound must be greater than origin");
717	>	throw new IllegalArgumentException(BAD_RANGE);
718		return StreamSupport.longStream
719		(new RandomLongsSpliterator
720		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 760 | Line 723 | public class SplittableRandom {
723
724		/**
725		* Returns an effectively unlimited stream of pseudorandom {@code
726	<	* long} values, each conforming to the given origin and bound.
726	>	* long} values from this generator and/or one split from it; each value
727	>	* conforms to the given origin (inclusive) and bound (exclusive).
728		*
729		* @implNote This method is implemented to be equivalent to {@code
730		* longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
731		*
732	<	* @param randomNumberOrigin the origin of each random value
733	<	* @param randomNumberBound the bound of each random value
732	>	* @param randomNumberOrigin the origin (inclusive) of each random value
733	>	* @param randomNumberBound the bound (exclusive) of each random value
734		* @return a stream of pseudorandom {@code long} values,
735	<	*         each with the given origin and bound
735	>	*         each with the given origin (inclusive) and bound (exclusive)
736		* @throws IllegalArgumentException if {@code randomNumberOrigin}
737		*         is greater than or equal to {@code randomNumberBound}
738		*/
739		public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
740		if (randomNumberOrigin >= randomNumberBound)
741	<	throw new IllegalArgumentException("bound must be greater than origin");
741	>	throw new IllegalArgumentException(BAD_RANGE);
742		return StreamSupport.longStream
743		(new RandomLongsSpliterator
744		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 783 | Line 747 | public class SplittableRandom {
747
748		/**
749		* Returns a stream producing the given {@code streamSize} number of
750	<	* pseudorandom {@code double} values, each between zero
751	<	* (inclusive) and one (exclusive).
750	>	* pseudorandom {@code double} values from this generator and/or one split
751	>	* from it; each value is between zero (inclusive) and one (exclusive).
752		*
753		* @param streamSize the number of values to generate
754		* @return a stream of {@code double} values
#	Line 793 | Line 757 | public class SplittableRandom {
757		*/
758		public DoubleStream doubles(long streamSize) {
759		if (streamSize < 0L)
760	<	throw new IllegalArgumentException("negative Stream size");
760	>	throw new IllegalArgumentException(BAD_SIZE);
761		return StreamSupport.doubleStream
762		(new RandomDoublesSpliterator
763		(this, 0L, streamSize, Double.MAX_VALUE, 0.0),
#	Line 802 | Line 766 | public class SplittableRandom {
766
767		/**
768		* Returns an effectively unlimited stream of pseudorandom {@code
769	<	* double} values, each between zero (inclusive) and one
770	<	* (exclusive).
769	>	* double} values from this generator and/or one split from it; each value
770	>	* is between zero (inclusive) and one (exclusive).
771		*
772		* @implNote This method is implemented to be equivalent to {@code
773		* doubles(Long.MAX_VALUE)}.
#	Line 819 | Line 783 | public class SplittableRandom {
783
784		/**
785		* Returns a stream producing the given {@code streamSize} number of
786	<	* pseudorandom {@code double} values, each conforming to the
787	<	* given origin and bound.
786	>	* pseudorandom {@code double} values from this generator and/or one split
787	>	* from it; each value conforms to the given origin (inclusive) and bound
788	>	* (exclusive).
789		*
790		* @param streamSize the number of values to generate
791	<	* @param randomNumberOrigin the origin of each random value
792	<	* @param randomNumberBound the bound of each random value
791	>	* @param randomNumberOrigin the origin (inclusive) of each random value
792	>	* @param randomNumberBound the bound (exclusive) of each random value
793		* @return a stream of pseudorandom {@code double} values,
794	<	* each with the given origin and bound
794	>	*         each with the given origin (inclusive) and bound (exclusive)
795		* @throws IllegalArgumentException if {@code streamSize} is
796	<	* less than zero
796	>	*         less than zero
797		* @throws IllegalArgumentException if {@code randomNumberOrigin}
798		*         is greater than or equal to {@code randomNumberBound}
799		*/
800		public DoubleStream doubles(long streamSize, double randomNumberOrigin,
801		double randomNumberBound) {
802		if (streamSize < 0L)
803	<	throw new IllegalArgumentException("negative Stream size");
803	>	throw new IllegalArgumentException(BAD_SIZE);
804		if (!(randomNumberOrigin < randomNumberBound))
805	<	throw new IllegalArgumentException("bound must be greater than origin");
805	>	throw new IllegalArgumentException(BAD_RANGE);
806		return StreamSupport.doubleStream
807		(new RandomDoublesSpliterator
808		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 846 | Line 811 | public class SplittableRandom {
811
812		/**
813		* Returns an effectively unlimited stream of pseudorandom {@code
814	<	* double} values, each conforming to the given origin and bound.
814	>	* double} values from this generator and/or one split from it; each value
815	>	* conforms to the given origin (inclusive) and bound (exclusive).
816		*
817		* @implNote This method is implemented to be equivalent to {@code
818		* doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
819		*
820	<	* @param randomNumberOrigin the origin of each random value
821	<	* @param randomNumberBound the bound of each random value
820	>	* @param randomNumberOrigin the origin (inclusive) of each random value
821	>	* @param randomNumberBound the bound (exclusive) of each random value
822		* @return a stream of pseudorandom {@code double} values,
823	<	* each with the given origin and bound
823	>	*         each with the given origin (inclusive) and bound (exclusive)
824		* @throws IllegalArgumentException if {@code randomNumberOrigin}
825		*         is greater than or equal to {@code randomNumberBound}
826		*/
827		public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
828		if (!(randomNumberOrigin < randomNumberBound))
829	<	throw new IllegalArgumentException("bound must be greater than origin");
829	>	throw new IllegalArgumentException(BAD_RANGE);
830		return StreamSupport.doubleStream
831		(new RandomDoublesSpliterator
832		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 875 | Line 841 | public class SplittableRandom {
841		* approach. The long and double versions of this class are
842		* identical except for types.
843		*/
844	<	static final class RandomIntsSpliterator implements Spliterator.OfInt {
844	>	private static final class RandomIntsSpliterator
845	>	implements Spliterator.OfInt {
846		final SplittableRandom rng;
847		long index;
848		final long fence;
#	Line 918 | Line 885 | public class SplittableRandom {
885		long i = index, f = fence;
886		if (i < f) {
887		index = f;
888	+	SplittableRandom r = rng;
889		int o = origin, b = bound;
890		do {
891	<	consumer.accept(rng.internalNextInt(o, b));
891	>	consumer.accept(r.internalNextInt(o, b));
892		} while (++i < f);
893		}
894		}
#	Line 929 | Line 897 | public class SplittableRandom {
897		/**
898		* Spliterator for long streams.
899		*/
900	<	static final class RandomLongsSpliterator implements Spliterator.OfLong {
900	>	private static final class RandomLongsSpliterator
901	>	implements Spliterator.OfLong {
902		final SplittableRandom rng;
903		long index;
904		final long fence;
#	Line 972 | Line 941 | public class SplittableRandom {
941		long i = index, f = fence;
942		if (i < f) {
943		index = f;
944	+	SplittableRandom r = rng;
945		long o = origin, b = bound;
946		do {
947	<	consumer.accept(rng.internalNextLong(o, b));
947	>	consumer.accept(r.internalNextLong(o, b));
948		} while (++i < f);
949		}
950		}
#	Line 984 | Line 954 | public class SplittableRandom {
954		/**
955		* Spliterator for double streams.
956		*/
957	<	static final class RandomDoublesSpliterator implements Spliterator.OfDouble {
957	>	private static final class RandomDoublesSpliterator
958	>	implements Spliterator.OfDouble {
959		final SplittableRandom rng;
960		long index;
961		final long fence;
#	Line 1027 | Line 998 | public class SplittableRandom {
998		long i = index, f = fence;
999		if (i < f) {
1000		index = f;
1001	+	SplittableRandom r = rng;
1002		double o = origin, b = bound;
1003		do {
1004	<	consumer.accept(rng.internalNextDouble(o, b));
1004	>	consumer.accept(r.internalNextDouble(o, b));
1005		} while (++i < f);
1006		}
1007		}

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