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Comparing jsr166/src/main/java/util/SplittableRandom.java (file contents):
Revision 1.4 by dl, Thu Jul 11 13:40:42 2013 UTC vs.
Revision 1.30 by jsr166, Sat Jan 2 02:27:03 2016 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;
37	<
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 50 | 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 set of
60	<	* values collectively generated by the two objects has the same
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 69 | 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 {
81	<
82	<	/*
83	<	* File organization: First the non-public methods that constitute
84	<	* the main algorithm, then the main public methods, followed by
85	<	* some custom spliterator classes needed for stream methods.
86	<	*
87	<	* Credits: Primary algorithm and code by Guy Steele.  Stream
88	<	* support methods by Doug Lea.  Documentation jointly produced
89	<	* with additional help from Brian Goetz.
90	<	*/
89	>	public final class SplittableRandom {
90
91		/*
92		* Implementation Overview.
#	Line 95 | 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 is simply to add a constant ("gamma")
153	<	* to the current seed, modulo a prime ("George"). However, the
154	<	* nextLong and nextInt methods do not return this value, but
155	<	* instead the results of bit-mixing transformations that produce
104	<	* more uniformly distributed 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.
177	<	*/
178	<	private static final long DEFAULT_SEED_GAMMA = 0xBD24B73A95FB84D9L;
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	>	*/
156
157		/**
158	<	* The next seed for default constructors.
158	>	* The golden ratio scaled to 64bits, used as the initial gamma
159	>	* value for (unsplit) SplittableRandoms.
160		*/
161	<	private static final AtomicLong defaultSeedGenerator =
184	<	new AtomicLong(System.nanoTime());
161	>	private static final long GOLDEN_GAMMA = 0x9e3779b97f4a7c15L;
162
163		/**
164	<	* The seed, updated only via method nextSeed.
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 long seed;
167	>	private static final double DOUBLE_UNIT = 0x1.0p-53; // 1.0 / (1L << 53);
168
169		/**
170	<	* The constant value added to seed (mod George) on each update.
170	>	* The seed. Updated only via method nextSeed.
171		*/
172	<	private final long gamma;
172	>	private long seed;
173
174		/**
175	<	* The next seed to use for splits. Propagated using
198	<	* addGammaModGeorge across instances.
175	>	* The step value.
176		*/
177	<	private final long nextSplit;
177	>	private final long gamma;
178
179		/**
180	<	* Internal constructor used by all other constructors and by
204	<	* method split. Establishes the initial seed for this instance,
205	<	* and uses the given splitSeed to establish gamma, as well as the
206	<	* nextSplit to use by this instance.
180	>	* Internal constructor used by all others except default constructor.
181		*/
182	<	private SplittableRandom(long seed, long splitSeed) {
182	>	private SplittableRandom(long seed, long gamma) {
183		this.seed = seed;
184	<	long s = splitSeed, g;
211	<	do { // ensure gamma >= 13, considered as an unsigned integer
212	<	s = addGammaModGeorge(s, GAMMA_GAMMA);
213	<	g = mix64(s);
214	<	} while (Long.compareUnsigned(g, 13L) < 0);
215	<	this.gamma = g;
216	<	this.nextSplit = s;
184	>	this.gamma = gamma;
185		}
186
187		/**
188	<	* Adds the given gamma value, g, to the given seed value s, mod
189	<	* George (2^64+13). We regard s and g as unsigned values
190	<	* (ranging from 0 to 2^64-1). We add g to s either once or twice
191	<	* (mod George) as necessary to produce an (unsigned) result less
192	<	* than 2^64.  We require that g must be at least 13. This
193	<	* guarantees that if (s+g) mod George >= 2^64 then (s+g+g) mod
226	<	* George < 2^64; thus we need only a conditional, not a loop,
227	<	* to be sure of getting a representable value.
228	<	*
229	<	* @param s a seed value
230	<	* @param g a gamma value, 13 <= g (as unsigned)
231	<	*/
232	<	private static long addGammaModGeorge(long s, long g) {
233	<	long p = s + g;
234	<	if (Long.compareUnsigned(p, g) >= 0)
235	<	return p;
236	<	long q = p - 13L;
237	<	return (Long.compareUnsigned(p, 13L) >= 0) ? q : (q + g);
188	>	* Computes Stafford variant 13 of 64bit mix function.
189	>	*/
190	>	private static long mix64(long z) {
191	>	z = (z ^ (z >>> 30)) * 0xbf58476d1ce4e5b9L;
192	>	z = (z ^ (z >>> 27)) * 0x94d049bb133111ebL;
193	>	return z ^ (z >>> 31);
194		}
195
196		/**
197	<	* Updates in-place and returns seed.
242	<	* See above for explanation.
197	>	* Returns the 32 high bits of Stafford variant 4 mix64 function as int.
198		*/
199	<	private long nextSeed() {
200	<	return seed = addGammaModGeorge(seed, gamma);
199	>	private static int mix32(long z) {
200	>	z = (z ^ (z >>> 33)) * 0x62a9d9ed799705f5L;
201	>	return (int)(((z ^ (z >>> 28)) * 0xcb24d0a5c88c35b3L) >>> 32);
202		}
203
204		/**
205	<	* Returns a bit-mixed transformation of its argument.
250	<	* See above for explanation.
205	>	* Returns the gamma value to use for a new split instance.
206		*/
207	<	private static long mix64(long z) {
208	<	z ^= (z >>> 33);
209	<	z *= 0xff51afd7ed558ccdL;
210	<	z ^= (z >>> 33);
211	<	z *= 0xc4ceb9fe1a85ec53L;
212	<	z ^= (z >>> 33);
258	<	return z;
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	<	* Returns a bit-mixed int transformation of its argument.
263	<	* See above for explanation.
216	>	* Adds gamma to seed.
217		*/
218	<	private static int mix32(long z) {
219	<	z ^= (z >>> 33);
267	<	z *= 0xc4ceb9fe1a85ec53L;
268	<	return (int)(z >>> 32);
218	>	private long nextSeed() {
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	>	java.security.PrivilegedAction<Boolean> action =
229	>	() -> Boolean.getBoolean("java.util.secureRandomSeed");
230	>	if (java.security.AccessController.doPrivileged(action)) {
231	>	byte[] seedBytes = java.security.SecureRandom.getSeed(8);
232	>	long s = (long)seedBytes[0] & 0xffL;
233	>	for (int i = 1; i < 8; ++i)
234	>	s = (s << 8) | ((long)seedBytes[i] & 0xffL);
235	>	return s;
236	>	}
237	>	return (mix64(System.currentTimeMillis()) ^
238	>	mix64(System.nanoTime()));
239		}
240
241	+	// IllegalArgumentException messages
242	+	static final String BAD_BOUND = "bound must be positive";
243	+	static final String BAD_RANGE = "bound must be greater than origin";
244	+	static final String BAD_SIZE  = "size must be non-negative";
245	+
246		/*
247		* Internal versions of nextX methods used by streams, as well as
248		* the public nextX(origin, bound) methods.  These exist mainly to
#	Line 326 | Line 289 | public class SplittableRandom {
289		long r = mix64(nextSeed());
290		if (origin < bound) {
291		long n = bound - origin, m = n - 1;
292	<	if ((n & m) == 0L) // power of two
292	>	if ((n & m) == 0L)  // power of two
293		r = (r & m) + origin;
294	<	else if (n > 0) { // reject over-represented candidates
294	>	else if (n > 0L) {  // reject over-represented candidates
295		for (long u = r >>> 1;            // ensure nonnegative
296	<	u + m - (r = u % n) < 0L;    // reject
296	>	u + m - (r = u % n) < 0L;    // rejection check
297		u = mix64(nextSeed()) >>> 1) // retry
298		;
299		r += origin;
300		}
301	<	else {             // range not representable as long
301	>	else {              // range not representable as long
302		while (r < origin || r >= bound)
303		r = mix64(nextSeed());
304		}
#	Line 355 | Line 318 | public class SplittableRandom {
318		int r = mix32(nextSeed());
319		if (origin < bound) {
320		int n = bound - origin, m = n - 1;
321	<	if ((n & m) == 0L)
321	>	if ((n & m) == 0)
322		r = (r & m) + origin;
323		else if (n > 0) {
324		for (int u = r >>> 1;
325	<	u + m - (r = u % n) < 0L;
325	>	u + m - (r = u % n) < 0;
326		u = mix32(nextSeed()) >>> 1)
327		;
328		r += origin;
#	Line 380 | Line 343 | public class SplittableRandom {
343		* @return a pseudorandom value
344		*/
345		final double internalNextDouble(double origin, double bound) {
346	<	long bits = (1023L << 52) | (nextLong() >>> 12);
384	<	double r = Double.longBitsToDouble(bits) - 1.0;
346	>	double r = (nextLong() >>> 11) * DOUBLE_UNIT;
347		if (origin < bound) {
348		r = r * (bound - origin) + origin;
349	<	if (r == bound) // correct for rounding
349	>	if (r >= bound) // correct for rounding
350		r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
351		}
352		return r;
#	Line 393 | Line 355 | public class SplittableRandom {
355		/* ---------------- public methods ---------------- */
356
357		/**
358	<	* Creates a new SplittableRandom instance using the given initial
359	<	* seed. Two SplittableRandom instances created with the same seed
360	<	* generate identical sequences of values.
358	>	* Creates a new SplittableRandom instance using the specified
359	>	* initial seed. SplittableRandom instances created with the same
360	>	* seed in the same program generate identical sequences of values.
361		*
362		* @param seed the initial seed
363		*/
364		public SplittableRandom(long seed) {
365	<	this(seed, 0);
365	>	this(seed, GOLDEN_GAMMA);
366		}
367
368		/**
#	Line 409 | Line 371 | public class SplittableRandom {
371		* of those of any other instances in the current program; and
372		* may, and typically does, vary across program invocations.
373		*/
374	<	public SplittableRandom() {
375	<	this(nextDefaultSeed(), GAMMA_GAMMA);
374	>	public SplittableRandom() { // emulate defaultGen.split()
375	>	long s = defaultGen.getAndAdd(2 * GOLDEN_GAMMA);
376	>	this.seed = mix64(s);
377	>	this.gamma = mixGamma(s + GOLDEN_GAMMA);
378		}
379
380		/**
#	Line 428 | Line 392 | public class SplittableRandom {
392		* @return the new SplittableRandom instance
393		*/
394		public SplittableRandom split() {
395	<	return new SplittableRandom(nextSeed(), nextSplit);
395	>	return new SplittableRandom(nextLong(), mixGamma(nextSeed()));
396		}
397
398		/**
399		* Returns a pseudorandom {@code int} value.
400		*
401	<	* @return a pseudorandom value
401	>	* @return a pseudorandom {@code int} value
402		*/
403		public int nextInt() {
404		return mix32(nextSeed());
405		}
406
407		/**
408	<	* Returns a pseudorandom {@code int} value between 0 (inclusive)
408	>	* Returns a pseudorandom {@code int} value between zero (inclusive)
409		* and the specified bound (exclusive).
410		*
411	<	* @param bound the bound on the random number to be returned.  Must be
412	<	*        positive.
413	<	* @return a pseudorandom {@code int} value between {@code 0}
414	<	*         (inclusive) and the bound (exclusive).
451	<	* @exception IllegalArgumentException if the bound is not positive
411	>	* @param bound the upper bound (exclusive).  Must be positive.
412	>	* @return a pseudorandom {@code int} value between zero
413	>	*         (inclusive) and the bound (exclusive)
414	>	* @throws IllegalArgumentException if {@code bound} is not positive
415		*/
416		public int nextInt(int bound) {
417		if (bound <= 0)
418	<	throw new IllegalArgumentException("bound must be positive");
418	>	throw new IllegalArgumentException(BAD_BOUND);
419		// Specialize internalNextInt for origin 0
420		int r = mix32(nextSeed());
421		int m = bound - 1;
422	<	if ((bound & m) == 0L) // power of two
422	>	if ((bound & m) == 0) // power of two
423		r &= m;
424		else { // reject over-represented candidates
425		for (int u = r >>> 1;
426	<	u + m - (r = u % bound) < 0L;
426	>	u + m - (r = u % bound) < 0;
427		u = mix32(nextSeed()) >>> 1)
428		;
429		}
#	Line 474 | Line 437 | public class SplittableRandom {
437		* @param origin the least value returned
438		* @param bound the upper bound (exclusive)
439		* @return a pseudorandom {@code int} value between the origin
440	<	*         (inclusive) and the bound (exclusive).
441	<	* @exception IllegalArgumentException if {@code origin} is greater than
440	>	*         (inclusive) and the bound (exclusive)
441	>	* @throws IllegalArgumentException if {@code origin} is greater than
442		*         or equal to {@code bound}
443		*/
444		public int nextInt(int origin, int bound) {
445		if (origin >= bound)
446	<	throw new IllegalArgumentException("bound must be greater than origin");
446	>	throw new IllegalArgumentException(BAD_RANGE);
447		return internalNextInt(origin, bound);
448		}
449
450		/**
451		* Returns a pseudorandom {@code long} value.
452		*
453	<	* @return a pseudorandom value
453	>	* @return a pseudorandom {@code long} value
454		*/
455		public long nextLong() {
456		return mix64(nextSeed());
457		}
458
459		/**
460	<	* Returns a pseudorandom {@code long} value between 0 (inclusive)
460	>	* Returns a pseudorandom {@code long} value between zero (inclusive)
461		* and the specified bound (exclusive).
462		*
463	<	* @param bound the bound on the random number to be returned.  Must be
464	<	*        positive.
465	<	* @return a pseudorandom {@code long} value between {@code 0}
466	<	*         (inclusive) and the bound (exclusive).
504	<	* @exception IllegalArgumentException if the bound is not positive
463	>	* @param bound the upper bound (exclusive).  Must be positive.
464	>	* @return a pseudorandom {@code long} value between zero
465	>	*         (inclusive) and the bound (exclusive)
466	>	* @throws IllegalArgumentException if {@code bound} is not positive
467		*/
468		public long nextLong(long bound) {
469		if (bound <= 0)
470	<	throw new IllegalArgumentException("bound must be positive");
470	>	throw new IllegalArgumentException(BAD_BOUND);
471		// Specialize internalNextLong for origin 0
472		long r = mix64(nextSeed());
473		long m = bound - 1;
#	Line 527 | Line 489 | public class SplittableRandom {
489		* @param origin the least value returned
490		* @param bound the upper bound (exclusive)
491		* @return a pseudorandom {@code long} value between the origin
492	<	*         (inclusive) and the bound (exclusive).
493	<	* @exception IllegalArgumentException if {@code origin} is greater than
492	>	*         (inclusive) and the bound (exclusive)
493	>	* @throws IllegalArgumentException if {@code origin} is greater than
494		*         or equal to {@code bound}
495		*/
496		public long nextLong(long origin, long bound) {
497		if (origin >= bound)
498	<	throw new IllegalArgumentException("bound must be greater than origin");
498	>	throw new IllegalArgumentException(BAD_RANGE);
499		return internalNextLong(origin, bound);
500		}
501
502		/**
503	<	* Returns a pseudorandom {@code double} value between {@code 0.0}
504	<	* (inclusive) and {@code 1.0} (exclusive).
503	>	* Returns a pseudorandom {@code double} value between zero
504	>	* (inclusive) and one (exclusive).
505		*
506	<	* @return a pseudorandom value between {@code 0.0}
507	<	* (inclusive) and {@code 1.0} (exclusive)
506	>	* @return a pseudorandom {@code double} value between zero
507	>	*         (inclusive) and one (exclusive)
508		*/
509		public double nextDouble() {
510	<	long bits = (1023L << 52) | (nextLong() >>> 12);
549	<	return Double.longBitsToDouble(bits) - 1.0;
510	>	return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT;
511		}
512
513		/**
514		* Returns a pseudorandom {@code double} value between 0.0
515		* (inclusive) and the specified bound (exclusive).
516		*
517	<	* @param bound the bound on the random number to be returned.  Must be
518	<	*        positive.
519	<	* @return a pseudorandom {@code double} value between {@code 0.0}
559	<	*         (inclusive) and the bound (exclusive).
517	>	* @param bound the upper bound (exclusive).  Must be positive.
518	>	* @return a pseudorandom {@code double} value between zero
519	>	*         (inclusive) and the bound (exclusive)
520		* @throws IllegalArgumentException if {@code bound} is not positive
521		*/
522		public double nextDouble(double bound) {
523	<	if (bound <= 0.0)
524	<	throw new IllegalArgumentException("bound must be positive");
525	<	double result = nextDouble() * bound;
523	>	if (!(bound > 0.0))
524	>	throw new IllegalArgumentException(BAD_BOUND);
525	>	double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound;
526		return (result < bound) ?  result : // correct for rounding
527		Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
528		}
529
530		/**
531	<	* Returns a pseudorandom {@code double} value between the given
531	>	* Returns a pseudorandom {@code double} value between the specified
532		* origin (inclusive) and bound (exclusive).
533		*
534		* @param origin the least value returned
535	<	* @param bound the upper bound
535	>	* @param bound the upper bound (exclusive)
536		* @return a pseudorandom {@code double} value between the origin
537	<	*         (inclusive) and the bound (exclusive).
537	>	*         (inclusive) and the bound (exclusive)
538		* @throws IllegalArgumentException if {@code origin} is greater than
539		*         or equal to {@code bound}
540		*/
541		public double nextDouble(double origin, double bound) {
542	<	if (origin >= bound)
543	<	throw new IllegalArgumentException("bound must be greater than origin");
542	>	if (!(origin < bound))
543	>	throw new IllegalArgumentException(BAD_RANGE);
544		return internalNextDouble(origin, bound);
545		}
546
547	+	/**
548	+	* Returns a pseudorandom {@code boolean} value.
549	+	*
550	+	* @return a pseudorandom {@code boolean} value
551	+	*/
552	+	public boolean nextBoolean() {
553	+	return mix32(nextSeed()) < 0;
554	+	}
555	+
556		// stream methods, coded in a way intended to better isolate for
557		// maintenance purposes the small differences across forms.
558
559		/**
560	<	* Returns a stream with the given {@code streamSize} number of
561	<	* pseudorandom {@code int} values.
560	>	* Returns a stream producing the given {@code streamSize} number
561	>	* of pseudorandom {@code int} values from this generator and/or
562	>	* one split from it.
563		*
564		* @param streamSize the number of values to generate
565		* @return a stream of pseudorandom {@code int} values
566		* @throws IllegalArgumentException if {@code streamSize} is
567	<	* less than zero
567	>	*         less than zero
568		*/
569		public IntStream ints(long streamSize) {
570		if (streamSize < 0L)
571	<	throw new IllegalArgumentException("negative Stream size");
571	>	throw new IllegalArgumentException(BAD_SIZE);
572		return StreamSupport.intStream
573		(new RandomIntsSpliterator
574		(this, 0L, streamSize, Integer.MAX_VALUE, 0),
#	Line 607 | Line 577 | public class SplittableRandom {
577
578		/**
579		* Returns an effectively unlimited stream of pseudorandom {@code int}
580	<	* values
580	>	* values from this generator and/or one split from it.
581		*
582		* @implNote This method is implemented to be equivalent to {@code
583		* ints(Long.MAX_VALUE)}.
#	Line 622 | Line 592 | public class SplittableRandom {
592		}
593
594		/**
595	<	* Returns a stream with the given {@code streamSize} number of
596	<	* pseudorandom {@code int} values, each conforming to the given
597	<	* origin and bound.
595	>	* Returns a stream producing the given {@code streamSize} number
596	>	* of pseudorandom {@code int} values from this generator and/or one split
597	>	* from it; each value conforms to the given origin (inclusive) and bound
598	>	* (exclusive).
599		*
600		* @param streamSize the number of values to generate
601	<	* @param randomNumberOrigin the origin of each random value
602	<	* @param randomNumberBound the bound of each random value
601	>	* @param randomNumberOrigin the origin (inclusive) of each random value
602	>	* @param randomNumberBound the bound (exclusive) of each random value
603		* @return a stream of pseudorandom {@code int} values,
604	<	* each with the given origin and bound.
604	>	*         each with the given origin (inclusive) and bound (exclusive)
605		* @throws IllegalArgumentException if {@code streamSize} is
606	<	* less than zero.
636	<	* @throws IllegalArgumentException if {@code randomNumberOrigin}
606	>	*         less than zero, or {@code randomNumberOrigin}
607		*         is greater than or equal to {@code randomNumberBound}
608		*/
609		public IntStream ints(long streamSize, int randomNumberOrigin,
610		int randomNumberBound) {
611		if (streamSize < 0L)
612	<	throw new IllegalArgumentException("negative Stream size");
612	>	throw new IllegalArgumentException(BAD_SIZE);
613		if (randomNumberOrigin >= randomNumberBound)
614	<	throw new IllegalArgumentException("bound must be greater than origin");
614	>	throw new IllegalArgumentException(BAD_RANGE);
615		return StreamSupport.intStream
616		(new RandomIntsSpliterator
617		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 650 | Line 620 | public class SplittableRandom {
620
621		/**
622		* Returns an effectively unlimited stream of pseudorandom {@code
623	<	* int} values, each conforming to the given origin and bound.
623	>	* int} values from this generator and/or one split from it; each value
624	>	* conforms to the given origin (inclusive) and bound (exclusive).
625		*
626		* @implNote This method is implemented to be equivalent to {@code
627		* ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
628		*
629	<	* @param randomNumberOrigin the origin of each random value
630	<	* @param randomNumberBound the bound of each random value
629	>	* @param randomNumberOrigin the origin (inclusive) of each random value
630	>	* @param randomNumberBound the bound (exclusive) of each random value
631		* @return a stream of pseudorandom {@code int} values,
632	<	* each with the given origin and bound.
632	>	*         each with the given origin (inclusive) and bound (exclusive)
633		* @throws IllegalArgumentException if {@code randomNumberOrigin}
634		*         is greater than or equal to {@code randomNumberBound}
635		*/
636		public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
637		if (randomNumberOrigin >= randomNumberBound)
638	<	throw new IllegalArgumentException("bound must be greater than origin");
638	>	throw new IllegalArgumentException(BAD_RANGE);
639		return StreamSupport.intStream
640		(new RandomIntsSpliterator
641		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 672 | Line 643 | public class SplittableRandom {
643		}
644
645		/**
646	<	* Returns a stream with the given {@code streamSize} number of
647	<	* pseudorandom {@code long} values.
646	>	* Returns a stream producing the given {@code streamSize} number
647	>	* of pseudorandom {@code long} values from this generator and/or
648	>	* one split from it.
649		*
650		* @param streamSize the number of values to generate
651	<	* @return a stream of {@code long} values
651	>	* @return a stream of pseudorandom {@code long} values
652		* @throws IllegalArgumentException if {@code streamSize} is
653	<	* less than zero
653	>	*         less than zero
654		*/
655		public LongStream longs(long streamSize) {
656		if (streamSize < 0L)
657	<	throw new IllegalArgumentException("negative Stream size");
657	>	throw new IllegalArgumentException(BAD_SIZE);
658		return StreamSupport.longStream
659		(new RandomLongsSpliterator
660		(this, 0L, streamSize, Long.MAX_VALUE, 0L),
#	Line 690 | Line 662 | public class SplittableRandom {
662		}
663
664		/**
665	<	* Returns an effectively unlimited stream of pseudorandom {@code long}
666	<	* values.
665	>	* Returns an effectively unlimited stream of pseudorandom {@code
666	>	* long} values from this generator and/or one split from it.
667		*
668		* @implNote This method is implemented to be equivalent to {@code
669		* longs(Long.MAX_VALUE)}.
#	Line 706 | Line 678 | public class SplittableRandom {
678		}
679
680		/**
681	<	* Returns a stream with the given {@code streamSize} number of
682	<	* pseudorandom {@code long} values, each conforming to the
683	<	* given origin and bound.
681	>	* Returns a stream producing the given {@code streamSize} number of
682	>	* pseudorandom {@code long} values from this generator and/or one split
683	>	* from it; each value conforms to the given origin (inclusive) and bound
684	>	* (exclusive).
685		*
686		* @param streamSize the number of values to generate
687	<	* @param randomNumberOrigin the origin of each random value
688	<	* @param randomNumberBound the bound of each random value
687	>	* @param randomNumberOrigin the origin (inclusive) of each random value
688	>	* @param randomNumberBound the bound (exclusive) of each random value
689		* @return a stream of pseudorandom {@code long} values,
690	<	* each with the given origin and bound.
690	>	*         each with the given origin (inclusive) and bound (exclusive)
691		* @throws IllegalArgumentException if {@code streamSize} is
692	<	* less than zero.
720	<	* @throws IllegalArgumentException if {@code randomNumberOrigin}
692	>	*         less than zero, or {@code randomNumberOrigin}
693		*         is greater than or equal to {@code randomNumberBound}
694		*/
695		public LongStream longs(long streamSize, long randomNumberOrigin,
696		long randomNumberBound) {
697		if (streamSize < 0L)
698	<	throw new IllegalArgumentException("negative Stream size");
698	>	throw new IllegalArgumentException(BAD_SIZE);
699		if (randomNumberOrigin >= randomNumberBound)
700	<	throw new IllegalArgumentException("bound must be greater than origin");
700	>	throw new IllegalArgumentException(BAD_RANGE);
701		return StreamSupport.longStream
702		(new RandomLongsSpliterator
703		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 734 | Line 706 | public class SplittableRandom {
706
707		/**
708		* Returns an effectively unlimited stream of pseudorandom {@code
709	<	* long} values, each conforming to the given origin and bound.
709	>	* long} values from this generator and/or one split from it; each value
710	>	* conforms to the given origin (inclusive) and bound (exclusive).
711		*
712		* @implNote This method is implemented to be equivalent to {@code
713		* longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
714		*
715	<	* @param randomNumberOrigin the origin of each random value
716	<	* @param randomNumberBound the bound of each random value
715	>	* @param randomNumberOrigin the origin (inclusive) of each random value
716	>	* @param randomNumberBound the bound (exclusive) of each random value
717		* @return a stream of pseudorandom {@code long} values,
718	<	* each with the given origin and bound.
718	>	*         each with the given origin (inclusive) and bound (exclusive)
719		* @throws IllegalArgumentException if {@code randomNumberOrigin}
720		*         is greater than or equal to {@code randomNumberBound}
721		*/
722		public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
723		if (randomNumberOrigin >= randomNumberBound)
724	<	throw new IllegalArgumentException("bound must be greater than origin");
724	>	throw new IllegalArgumentException(BAD_RANGE);
725		return StreamSupport.longStream
726		(new RandomLongsSpliterator
727		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 756 | Line 729 | public class SplittableRandom {
729		}
730
731		/**
732	<	* Returns a stream with the given {@code streamSize} number of
733	<	* pseudorandom {@code double} values, each between {@code 0.0}
734	<	* (inclusive) and {@code 1.0} (exclusive).
732	>	* Returns a stream producing the given {@code streamSize} number of
733	>	* pseudorandom {@code double} values from this generator and/or one split
734	>	* from it; each value is between zero (inclusive) and one (exclusive).
735		*
736		* @param streamSize the number of values to generate
737		* @return a stream of {@code double} values
738		* @throws IllegalArgumentException if {@code streamSize} is
739	<	* less than zero
739	>	*         less than zero
740		*/
741		public DoubleStream doubles(long streamSize) {
742		if (streamSize < 0L)
743	<	throw new IllegalArgumentException("negative Stream size");
743	>	throw new IllegalArgumentException(BAD_SIZE);
744		return StreamSupport.doubleStream
745		(new RandomDoublesSpliterator
746		(this, 0L, streamSize, Double.MAX_VALUE, 0.0),
#	Line 776 | Line 749 | public class SplittableRandom {
749
750		/**
751		* Returns an effectively unlimited stream of pseudorandom {@code
752	<	* double} values, each between {@code 0.0} (inclusive) and {@code
753	<	* 1.0} (exclusive).
752	>	* double} values from this generator and/or one split from it; each value
753	>	* is between zero (inclusive) and one (exclusive).
754		*
755		* @implNote This method is implemented to be equivalent to {@code
756		* doubles(Long.MAX_VALUE)}.
#	Line 792 | Line 765 | public class SplittableRandom {
765		}
766
767		/**
768	<	* Returns a stream with the given {@code streamSize} number of
769	<	* pseudorandom {@code double} values, each conforming to the
770	<	* given origin and bound.
768	>	* Returns a stream producing the given {@code streamSize} number of
769	>	* pseudorandom {@code double} values from this generator and/or one split
770	>	* from it; each value conforms to the given origin (inclusive) and bound
771	>	* (exclusive).
772		*
773		* @param streamSize the number of values to generate
774	<	* @param randomNumberOrigin the origin of each random value
775	<	* @param randomNumberBound the bound of each random value
774	>	* @param randomNumberOrigin the origin (inclusive) of each random value
775	>	* @param randomNumberBound the bound (exclusive) of each random value
776		* @return a stream of pseudorandom {@code double} values,
777	<	* each with the given origin and bound.
777	>	*         each with the given origin (inclusive) and bound (exclusive)
778		* @throws IllegalArgumentException if {@code streamSize} is
779	<	* less than zero.
779	>	*         less than zero
780		* @throws IllegalArgumentException if {@code randomNumberOrigin}
781		*         is greater than or equal to {@code randomNumberBound}
782		*/
783		public DoubleStream doubles(long streamSize, double randomNumberOrigin,
784		double randomNumberBound) {
785		if (streamSize < 0L)
786	<	throw new IllegalArgumentException("negative Stream size");
787	<	if (randomNumberOrigin >= randomNumberBound)
788	<	throw new IllegalArgumentException("bound must be greater than origin");
786	>	throw new IllegalArgumentException(BAD_SIZE);
787	>	if (!(randomNumberOrigin < randomNumberBound))
788	>	throw new IllegalArgumentException(BAD_RANGE);
789		return StreamSupport.doubleStream
790		(new RandomDoublesSpliterator
791		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 820 | Line 794 | public class SplittableRandom {
794
795		/**
796		* Returns an effectively unlimited stream of pseudorandom {@code
797	<	* double} values, each conforming to the given origin and bound.
797	>	* double} values from this generator and/or one split from it; each value
798	>	* conforms to the given origin (inclusive) and bound (exclusive).
799		*
800		* @implNote This method is implemented to be equivalent to {@code
801		* doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
802		*
803	<	* @param randomNumberOrigin the origin of each random value
804	<	* @param randomNumberBound the bound of each random value
803	>	* @param randomNumberOrigin the origin (inclusive) of each random value
804	>	* @param randomNumberBound the bound (exclusive) of each random value
805		* @return a stream of pseudorandom {@code double} values,
806	<	* each with the given origin and bound.
806	>	*         each with the given origin (inclusive) and bound (exclusive)
807		* @throws IllegalArgumentException if {@code randomNumberOrigin}
808		*         is greater than or equal to {@code randomNumberBound}
809		*/
810		public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
811	<	if (randomNumberOrigin >= randomNumberBound)
812	<	throw new IllegalArgumentException("bound must be greater than origin");
811	>	if (!(randomNumberOrigin < randomNumberBound))
812	>	throw new IllegalArgumentException(BAD_RANGE);
813		return StreamSupport.doubleStream
814		(new RandomDoublesSpliterator
815		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 843 | Line 818 | public class SplittableRandom {
818
819		/**
820		* Spliterator for int streams.  We multiplex the four int
821	<	* versions into one class by treating and bound < origin as
821	>	* versions into one class by treating a bound less than origin as
822		* unbounded, and also by treating "infinite" as equivalent to
823		* Long.MAX_VALUE. For splits, it uses the standard divide-by-two
824		* approach. The long and double versions of this class are
825		* identical except for types.
826		*/
827	<	static class RandomIntsSpliterator implements Spliterator.OfInt {
827	>	private static final class RandomIntsSpliterator
828	>	implements Spliterator.OfInt {
829		final SplittableRandom rng;
830		long index;
831		final long fence;
#	Line 892 | 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 903 | Line 880 | public class SplittableRandom {
880		/**
881		* Spliterator for long streams.
882		*/
883	<	static class RandomLongsSpliterator implements Spliterator.OfLong {
883	>	private static final class RandomLongsSpliterator
884	>	implements Spliterator.OfLong {
885		final SplittableRandom rng;
886		long index;
887		final long fence;
#	Line 946 | Line 924 | public class SplittableRandom {
924		long i = index, f = fence;
925		if (i < f) {
926		index = f;
927	+	SplittableRandom r = rng;
928		long o = origin, b = bound;
929		do {
930	<	consumer.accept(rng.internalNextLong(o, b));
930	>	consumer.accept(r.internalNextLong(o, b));
931		} while (++i < f);
932		}
933		}
#	Line 958 | Line 937 | public class SplittableRandom {
937		/**
938		* Spliterator for double streams.
939		*/
940	<	static class RandomDoublesSpliterator implements Spliterator.OfDouble {
940	>	private static final class RandomDoublesSpliterator
941	>	implements Spliterator.OfDouble {
942		final SplittableRandom rng;
943		long index;
944		final long fence;
#	Line 1001 | Line 981 | public class SplittableRandom {
981		long i = index, f = fence;
982		if (i < f) {
983		index = f;
984	+	SplittableRandom r = rng;
985		double o = origin, b = bound;
986		do {
987	<	consumer.accept(rng.internalNextDouble(o, b));
987	>	consumer.accept(r.internalNextDouble(o, b));
988		} while (++i < f);
989		}
990		}
991		}
992
993		}
1013	–

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