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root/jsr166/jsr166/src/main/java/util/SplittableRandom.java

Comparing jsr166/src/main/java/util/SplittableRandom.java (file contents):
Revision 1.6 by dl, Thu Jul 11 23:22:01 2013 UTC vs.
Revision 1.17 by jsr166, Tue Aug 13 23:34:47 2013 UTC

#	Line 25 | Line 25
25
26		package java.util;
27
28	+	import java.net.InetAddress;
29		import java.util.concurrent.atomic.AtomicLong;
30		import java.util.Spliterator;
31		import java.util.function.IntConsumer;
#	Line 35 | Line 36 | import java.util.stream.IntStream;
36		import java.util.stream.LongStream;
37		import java.util.stream.DoubleStream;
38
38	–
39		/**
40		* A generator of uniform pseudorandom values applicable for use in
41		* (among other contexts) isolated parallel computations that may
42		* generate subtasks. Class SplittableRandom supports methods for
43		* producing pseudorandom numbers of type {@code int}, {@code long},
44		* and {@code double} with similar usages as for class
45	<	* {@link java.util.Random} but differs in the following ways: <ul>
45	>	* {@link java.util.Random} but differs in the following ways:
46	>	*
47	>	* <ul>
48		*
49		* <li>Series of generated values pass the DieHarder suite testing
50		* independence and uniformity properties of random number generators.
#	Line 50 | Line 52 | import java.util.stream.DoubleStream;
52		* href="http://www.phy.duke.edu/~rgb/General/dieharder.php"> version
53		* 3.31.1</a>.) These tests validate only the methods for certain
54		* types and ranges, but similar properties are expected to hold, at
55	<	* least approximately, for others as well.  </li>
55	>	* least approximately, for others as well. The <em>period</em>
56	>	* (length of any series of generated values before it repeats) is at
57	>	* least 2<sup>64</sup>. </li>
58		*
59		* <li> Method {@link #split} constructs and returns a new
60		* SplittableRandom instance that shares no mutable state with the
61	<	* current instance. However, with very high probability, the set of
62	<	* values collectively generated by the two objects has the same
61	>	* current instance. However, with very high probability, the
62	>	* values collectively generated by the two objects have the same
63		* statistical properties as if the same quantity of values were
64		* generated by a single thread using a single {@code
65		* SplittableRandom} object.  </li>
#	Line 80 | Line 84 | import java.util.stream.DoubleStream;
84		public class SplittableRandom {
85
86		/*
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	–	*/
91	–
92	–	/*
87		* Implementation Overview.
88		*
89		* This algorithm was inspired by the "DotMix" algorithm by
90		* Leiserson, Schardl, and Sukha "Deterministic Parallel
91		* Random-Number Generation for Dynamic-Multithreading Platforms",
92	<	* PPoPP 2012, but improves and extends it in several ways.
93	<	*
94	<	* The primary update step is simply to add a constant ("gamma")
95	<	* to the current seed, modulo a prime ("George"). However, the
96	<	* nextLong and nextInt methods do not return this value, but
97	<	* instead the results of bit-mixing transformations that produce
98	<	* more uniformly distributed sequences.
99	<	*
100	<	* "George" is the otherwise nameless (because it cannot be
101	<	* represented) prime number 2^64+13. Using a prime number larger
102	<	* than can fit in a long ensures that all possible long values
103	<	* can occur, plus 13 others that just get skipped over when they
104	<	* are encountered; see method addGammaModGeorge. For this to
105	<	* work, initial gamma values must be at least 13.
106	<	*
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
92	>	* PPoPP 2012, as well as those in "Parallel random numbers: as
93	>	* easy as 1, 2, 3" by Salmon, Morae, Dror, and Shaw, SC 2011.  It
94	>	* differs mainly in simplifying and cheapening operations.
95	>	*
96	>	* The primary update step (method nextSeed()) is to add a
97	>	* constant ("gamma") to the current (64 bit) seed, forming a
98	>	* simple sequence.  The seed and the gamma values for any two
99	>	* SplittableRandom instances are highly likely to be different.
100	>	*
101	>	* Methods nextLong, nextInt, and derivatives do not return the
102	>	* sequence (seed) values, but instead a hash-like bit-mix of
103	>	* their bits, producing more independently distributed sequences.
104	>	* For nextLong, the mix64 bit-mixing function computes the same
105	>	* value as the "64-bit finalizer" function in Austin Appleby's
106	>	* MurmurHash3 algorithm.  See
107		* http://code.google.com/p/smhasher/wiki/MurmurHash3 , which
108		* comments: "The constants for the finalizers were generated by a
109		* simple simulated-annealing algorithm, and both avalanche all
110	<	* bits of 'h' to within 0.25% bias." It also appears to work to
111	<	* use instead any of the variants proposed by David Stafford at
112	<	* http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html
113	<	* but these variants have not yet been tested as thoroughly
114	<	* in the context of the implementation of SplittableRandom.
115	<	*
116	<	* The mix32 function used for nextInt just consists of two of the
117	<	* five lines of mix64; avalanche testing shows that the 64-bit result
118	<	* has its top 32 bits avalanched well, though not the bottom 32 bits.
119	<	* DieHarder tests show that it is adequate for generating one
120	<	* random int from the 64-bit result of nextSeed.
121	<	*
122	<	* Support for the default (no-argument) constructor relies on an
123	<	* AtomicLong (defaultSeedGenerator) to help perform the
124	<	* equivalent of a split of a statically constructed
125	<	* SplittableRandom. Unlike other cases, this split must be
126	<	* performed in a thread-safe manner. We use
127	<	* AtomicLong.compareAndSet as the (typically) most efficient
128	<	* mechanism. To bootstrap, we start off using System.nanotime(),
129	<	* and update using another "genuinely random" constant
130	<	* DEFAULT_SEED_GAMMA. The default constructor uses GAMMA_GAMMA,
131	<	* not 0, for its splitSeed argument (addGammaModGeorge(0,
132	<	* GAMMA_GAMMA) == GAMMA_GAMMA) to reflect that each is split from
133	<	* this root generator, even though the root is not explicitly
134	<	* represented as a SplittableRandom.
110	>	* bits of 'h' to within 0.25% bias." The mix32 function is
111	>	* equivalent to (int)(mix64(seed) >>> 32), but faster because it
112	>	* omits a step that doesn't contribute to result.
113	>	*
114	>	* The split operation uses the current generator to form the seed
115	>	* and gamma for another SplittableRandom.  To conservatively
116	>	* avoid potential correlations between seed and value generation,
117	>	* gamma selection (method nextGamma) uses the "Mix13" constants
118	>	* for MurmurHash3 described by David Stafford
119	>	* (http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html)
120	>	* To avoid potential weaknesses in bit-mixing transformations, we
121	>	* restrict gammas to odd values with at least 12 and no more than
122	>	* 52 bits set.  Rather than rejecting candidates with too few or
123	>	* too many bits set, method nextGamma flips some bits (which has
124	>	* the effect of mapping at most 4 to any given gamma value).
125	>	* This reduces the effective set of 64bit odd gamma values by
126	>	* about 2<sup>14</sup>, a very tiny percentage, and serves as an
127	>	* automated screening for sequence constant selection that is
128	>	* left as an empirical decision in some other hashing and crypto
129	>	* algorithms.
130	>	*
131	>	* The resulting generator thus transforms a sequence in which
132	>	* (typically) many bits change on each step, with an inexpensive
133	>	* mixer with good (but less than cryptographically secure)
134	>	* avalanching.
135	>	*
136	>	* The default (no-argument) constructor, in essence, invokes
137	>	* split() for a common "seeder" SplittableRandom.  Unlike other
138	>	* cases, this split must be performed in a thread-safe manner, so
139	>	* we use an AtomicLong to represent the seed rather than use an
140	>	* explicit SplittableRandom. To bootstrap the seeder, we start
141	>	* off using a seed based on current time and host. This serves as
142	>	* a slimmed-down (and insecure) variant of SecureRandom that also
143	>	* avoids stalls that may occur when using /dev/random.
144	>	*
145	>	* It is a relatively simple matter to apply the basic design here
146	>	* to use 128 bit seeds. However, emulating 128bit arithmetic and
147	>	* carrying around twice the state add more overhead than appears
148	>	* warranted for current usages.
149	>	*
150	>	* File organization: First the non-public methods that constitute
151	>	* the main algorithm, then the main public methods, followed by
152	>	* some custom spliterator classes needed for stream methods.
153		*/
154
155		/**
156	<	* The "genuinely random" value for producing new gamma values.
157	<	* The value is arbitrary, subject to the requirement that it be
158	<	* 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.
156	>	* The initial gamma value for (unsplit) SplittableRandoms. Must
157	>	* be odd with at least 12 and no more than 52 bits set. Currently
158	>	* set to the golden ratio scaled to 64bits.
159		*/
160	<	private static final long DEFAULT_SEED_GAMMA = 0xBD24B73A95FB84D9L;
160	>	private static final long INITIAL_GAMMA = 0x9e3779b97f4a7c15L;
161
162		/**
163		* The least non-zero value returned by nextDouble(). This value
164	<	* is scaled by a random value of 52 bits to produce a result.
164	>	* is scaled by a random value of 53 bits to produce a result.
165		*/
166		private static final double DOUBLE_UNIT = 1.0 / (1L << 53);
167
168		/**
169	<	* The next seed for default constructors.
188	<	*/
189	<	private static final AtomicLong defaultSeedGenerator =
190	<	new AtomicLong(System.nanoTime());
191	<
192	<	/**
193	<	* The seed, updated only via method nextSeed.
169	>	* The seed. Updated only via method nextSeed.
170		*/
171		private long seed;
172
173		/**
174	<	* The constant value added to seed (mod George) on each update.
174	>	* The step value.
175		*/
176		private final long gamma;
177
178		/**
179	<	* The next seed to use for splits. Propagated using
204	<	* addGammaModGeorge across instances.
179	>	* Internal constructor used by all others except default constructor.
180		*/
181	<	private final long nextSplit;
181	>	private SplittableRandom(long seed, long gamma) {
182	>	this.seed = seed;
183	>	this.gamma = gamma;
184	>	}
185
186		/**
187	<	* Internal constructor used by all other constructors and by
210	<	* method split. Establishes the initial seed for this instance,
211	<	* and uses the given splitSeed to establish gamma, as well as the
212	<	* nextSplit to use by this instance.
187	>	* Computes MurmurHash3 64bit mix function.
188		*/
189	<	private SplittableRandom(long seed, long splitSeed) {
190	<	this.seed = seed;
191	<	long s = splitSeed, g;
192	<	do { // ensure gamma >= 13, considered as an unsigned integer
218	<	s = addGammaModGeorge(s, GAMMA_GAMMA);
219	<	g = mix64(s);
220	<	} while (Long.compareUnsigned(g, 13L) < 0);
221	<	this.gamma = g;
222	<	this.nextSplit = s;
189	>	private static long mix64(long z) {
190	>	z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL;
191	>	z = (z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L;
192	>	return z ^ (z >>> 33);
193		}
194
195		/**
196	<	* Adds the given gamma value, g, to the given seed value s, mod
197	<	* George (2^64+13). We regard s and g as unsigned values
198	<	* (ranging from 0 to 2^64-1). We add g to s either once or twice
199	<	* (mod George) as necessary to produce an (unsigned) result less
200	<	* than 2^64.  We require that g must be at least 13. This
231	<	* guarantees that if (s+g) mod George >= 2^64 then (s+g+g) mod
232	<	* George < 2^64; thus we need only a conditional, not a loop,
233	<	* to be sure of getting a representable value.
234	<	*
235	<	* @param s a seed value
236	<	* @param g a gamma value, 13 <= g (as unsigned)
237	<	*/
238	<	private static long addGammaModGeorge(long s, long g) {
239	<	long p = s + g;
240	<	if (Long.compareUnsigned(p, g) >= 0)
241	<	return p;
242	<	long q = p - 13L;
243	<	return (Long.compareUnsigned(p, 13L) >= 0) ? q : (q + g);
196	>	* Returns the 32 high bits of mix64(z) as int.
197	>	*/
198	>	private static int mix32(long z) {
199	>	z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL;
200	>	return (int)(((z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L) >>> 32);
201		}
202
203		/**
204	<	* Updates in-place and returns seed.
248	<	* See above for explanation.
204	>	* Returns the gamma value to use for a new split instance.
205		*/
206	<	private long nextSeed() {
207	<	return seed = addGammaModGeorge(seed, gamma);
206	>	private static long nextGamma(long z) {
207	>	z = (z ^ (z >>> 30)) * 0xbf58476d1ce4e5b9L; // Stafford "Mix13"
208	>	z = (z ^ (z >>> 27)) * 0x94d049bb133111ebL;
209	>	z = (z ^ (z >>> 31)) | 1L; // force to be odd
210	>	int n = Long.bitCount(z);  // ensure enough 0 and 1 bits
211	>	return (n < 12 || n > 52) ? z ^ 0xaaaaaaaaaaaaaaaaL : z;
212		}
213
214		/**
215	<	* Returns a bit-mixed transformation of its argument.
256	<	* See above for explanation.
215	>	* Adds gamma to seed.
216		*/
217	<	private static long mix64(long z) {
218	<	z ^= (z >>> 33);
260	<	z *= 0xff51afd7ed558ccdL;
261	<	z ^= (z >>> 33);
262	<	z *= 0xc4ceb9fe1a85ec53L;
263	<	z ^= (z >>> 33);
264	<	return z;
217	>	private long nextSeed() {
218	>	return seed += gamma;
219		}
220
221		/**
222	<	* Returns a bit-mixed int transformation of its argument.
269	<	* See above for explanation.
222	>	* The seed generator for default constructors.
223		*/
224	<	private static int mix32(long z) {
225	<	z ^= (z >>> 33);
226	<	z *= 0xc4ceb9fe1a85ec53L;
227	<	return (int)(z >>> 32);
275	<	}
224	>	private static final AtomicLong seeder =
225	>	new AtomicLong(mix64((((long)hashedHostAddress()) << 32) ^
226	>	System.currentTimeMillis()) ^
227	>	mix64(System.nanoTime()));
228
229		/**
230	<	* Atomically updates and returns next seed for default constructor
230	>	* Returns hash of local host IP address, if available; else 0.
231		*/
232	<	private static long nextDefaultSeed() {
233	<	long oldSeed, newSeed;
234	<	do {
235	<	oldSeed = defaultSeedGenerator.get();
236	<	newSeed = addGammaModGeorge(oldSeed, DEFAULT_SEED_GAMMA);
237	<	} while (!defaultSeedGenerator.compareAndSet(oldSeed, newSeed));
286	<	return mix64(newSeed);
232	>	private static int hashedHostAddress() {
233	>	try {
234	>	return InetAddress.getLocalHost().hashCode();
235	>	} catch (Exception ex) {
236	>	return 0;
237	>	}
238		}
239
240	+	// IllegalArgumentException messages
241	+	static final String BadBound = "bound must be positive";
242	+	static final String BadRange = "bound must be greater than origin";
243	+	static final String BadSize  = "size must be non-negative";
244	+
245		/*
246		* Internal versions of nextX methods used by streams, as well as
247		* the public nextX(origin, bound) methods.  These exist mainly to
#	Line 332 | Line 288 | public class SplittableRandom {
288		long r = mix64(nextSeed());
289		if (origin < bound) {
290		long n = bound - origin, m = n - 1;
291	<	if ((n & m) == 0L) // power of two
291	>	if ((n & m) == 0L)  // power of two
292		r = (r & m) + origin;
293	<	else if (n > 0) { // reject over-represented candidates
293	>	else if (n > 0L) {  // reject over-represented candidates
294		for (long u = r >>> 1;            // ensure nonnegative
295	<	u + m - (r = u % n) < 0L;    // reject
295	>	u + m - (r = u % n) < 0L;    // rejection check
296		u = mix64(nextSeed()) >>> 1) // retry
297		;
298		r += origin;
299		}
300	<	else {             // range not representable as long
300	>	else {              // range not representable as long
301		while (r < origin || r >= bound)
302		r = mix64(nextSeed());
303		}
#	Line 361 | Line 317 | public class SplittableRandom {
317		int r = mix32(nextSeed());
318		if (origin < bound) {
319		int n = bound - origin, m = n - 1;
320	<	if ((n & m) == 0L)
320	>	if ((n & m) == 0)
321		r = (r & m) + origin;
322		else if (n > 0) {
323		for (int u = r >>> 1;
324	<	u + m - (r = u % n) < 0L;
324	>	u + m - (r = u % n) < 0;
325		u = mix32(nextSeed()) >>> 1)
326		;
327		r += origin;
#	Line 389 | Line 345 | public class SplittableRandom {
345		double r = (nextLong() >>> 11) * DOUBLE_UNIT;
346		if (origin < bound) {
347		r = r * (bound - origin) + origin;
348	<	if (r == bound) // correct for rounding
348	>	if (r >= bound) // correct for rounding
349		r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
350		}
351		return r;
#	Line 398 | Line 354 | public class SplittableRandom {
354		/* ---------------- public methods ---------------- */
355
356		/**
357	<	* Creates a new SplittableRandom instance using the given initial
358	<	* seed. Two SplittableRandom instances created with the same seed
359	<	* generate identical sequences of values.
357	>	* Creates a new SplittableRandom instance using the specified
358	>	* initial seed. SplittableRandom instances created with the same
359	>	* seed in the same program generate identical sequences of values.
360		*
361		* @param seed the initial seed
362		*/
363		public SplittableRandom(long seed) {
364	<	this(seed, 0);
364	>	this(seed, INITIAL_GAMMA);
365		}
366
367		/**
#	Line 414 | Line 370 | public class SplittableRandom {
370		* of those of any other instances in the current program; and
371		* may, and typically does, vary across program invocations.
372		*/
373	<	public SplittableRandom() {
374	<	this(nextDefaultSeed(), GAMMA_GAMMA);
373	>	public SplittableRandom() { // emulate seeder.split()
374	>	this.gamma = nextGamma(this.seed = seeder.addAndGet(INITIAL_GAMMA));
375		}
376
377		/**
#	Line 433 | Line 389 | public class SplittableRandom {
389		* @return the new SplittableRandom instance
390		*/
391		public SplittableRandom split() {
392	<	return new SplittableRandom(nextSeed(), nextSplit);
392	>	long s = nextSeed();
393	>	return new SplittableRandom(s, nextGamma(s));
394		}
395
396		/**
397		* Returns a pseudorandom {@code int} value.
398		*
399	<	* @return a pseudorandom value
399	>	* @return a pseudorandom {@code int} value
400		*/
401		public int nextInt() {
402		return mix32(nextSeed());
403		}
404
405		/**
406	<	* Returns a pseudorandom {@code int} value between 0 (inclusive)
406	>	* Returns a pseudorandom {@code int} value between zero (inclusive)
407		* and the specified bound (exclusive).
408		*
409		* @param bound the bound on the random number to be returned.  Must be
410		*        positive.
411	<	* @return a pseudorandom {@code int} value between {@code 0}
412	<	*         (inclusive) and the bound (exclusive).
413	<	* @exception IllegalArgumentException if the bound is not positive
411	>	* @return a pseudorandom {@code int} value between zero
412	>	*         (inclusive) and the bound (exclusive)
413	>	* @throws IllegalArgumentException if {@code bound} is not positive
414		*/
415		public int nextInt(int bound) {
416		if (bound <= 0)
417	<	throw new IllegalArgumentException("bound must be positive");
417	>	throw new IllegalArgumentException(BadBound);
418		// Specialize internalNextInt for origin 0
419		int r = mix32(nextSeed());
420		int m = bound - 1;
421	<	if ((bound & m) == 0L) // power of two
421	>	if ((bound & m) == 0) // power of two
422		r &= m;
423		else { // reject over-represented candidates
424		for (int u = r >>> 1;
425	<	u + m - (r = u % bound) < 0L;
425	>	u + m - (r = u % bound) < 0;
426		u = mix32(nextSeed()) >>> 1)
427		;
428		}
#	Line 479 | Line 436 | public class SplittableRandom {
436		* @param origin the least value returned
437		* @param bound the upper bound (exclusive)
438		* @return a pseudorandom {@code int} value between the origin
439	<	*         (inclusive) and the bound (exclusive).
440	<	* @exception IllegalArgumentException if {@code origin} is greater than
439	>	*         (inclusive) and the bound (exclusive)
440	>	* @throws IllegalArgumentException if {@code origin} is greater than
441		*         or equal to {@code bound}
442		*/
443		public int nextInt(int origin, int bound) {
444		if (origin >= bound)
445	<	throw new IllegalArgumentException("bound must be greater than origin");
445	>	throw new IllegalArgumentException(BadRange);
446		return internalNextInt(origin, bound);
447		}
448
449		/**
450		* Returns a pseudorandom {@code long} value.
451		*
452	<	* @return a pseudorandom value
452	>	* @return a pseudorandom {@code long} value
453		*/
454		public long nextLong() {
455		return mix64(nextSeed());
456		}
457
458		/**
459	<	* Returns a pseudorandom {@code long} value between 0 (inclusive)
459	>	* Returns a pseudorandom {@code long} value between zero (inclusive)
460		* and the specified bound (exclusive).
461		*
462		* @param bound the bound on the random number to be returned.  Must be
463		*        positive.
464	<	* @return a pseudorandom {@code long} value between {@code 0}
465	<	*         (inclusive) and the bound (exclusive).
466	<	* @exception IllegalArgumentException if the bound is not 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(BadBound);
471		// Specialize internalNextLong for origin 0
472		long r = mix64(nextSeed());
473		long m = bound - 1;
#	Line 532 | 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(BadRange);
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	<	return (nextLong() >>> 11) * DOUBLE_UNIT;
510	>	return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT;
511		}
512
513		/**
#	Line 559 | Line 516 | public class SplittableRandom {
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}
520	<	*         (inclusive) and the bound (exclusive).
519	>	* @return a pseudorandom {@code double} value between 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;
524	>	if (!(bound > 0.0))
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		}
530
531		/**
532	<	* Returns a pseudorandom {@code double} value between the given
532	>	* Returns a pseudorandom {@code double} value between the specified
533		* origin (inclusive) and bound (exclusive).
534		*
535		* @param origin the least value returned
536		* @param bound the upper bound
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");
543	>	if (!(origin < bound))
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 with 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
567		* @throws IllegalArgumentException if {@code streamSize} is
568	<	* less than zero
568	>	*         less than zero
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 611 | 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 626 | Line 593 | public class SplittableRandom {
593		}
594
595		/**
596	<	* Returns a stream with 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, each conforming to the
598	>	* given origin and bound.
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
603		* @return a stream of pseudorandom {@code int} values,
604	<	* each with the given origin and bound.
604	>	*         each with the given origin and bound
605		* @throws IllegalArgumentException if {@code streamSize} is
606	<	* less than zero.
640	<	* @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(BadSize);
613		if (randomNumberOrigin >= randomNumberBound)
614	<	throw new IllegalArgumentException("bound must be greater than origin");
614	>	throw new IllegalArgumentException(BadRange);
615		return StreamSupport.intStream
616		(new RandomIntsSpliterator
617		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 662 | Line 628 | public class SplittableRandom {
628		* @param randomNumberOrigin the origin of each random value
629		* @param randomNumberBound the bound of each random value
630		* @return a stream of pseudorandom {@code int} values,
631	<	* each with the given origin and bound.
631	>	*         each with the given origin and bound
632		* @throws IllegalArgumentException if {@code randomNumberOrigin}
633		*         is greater than or equal to {@code randomNumberBound}
634		*/
635		public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
636		if (randomNumberOrigin >= randomNumberBound)
637	<	throw new IllegalArgumentException("bound must be greater than origin");
637	>	throw new IllegalArgumentException(BadRange);
638		return StreamSupport.intStream
639		(new RandomIntsSpliterator
640		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 676 | Line 642 | public class SplittableRandom {
642		}
643
644		/**
645	<	* Returns a stream with the given {@code streamSize} number of
646	<	* pseudorandom {@code long} values.
645	>	* Returns a stream producing the given {@code streamSize} number
646	>	* of pseudorandom {@code long} values from this generator and/or
647	>	* one split from it.
648		*
649		* @param streamSize the number of values to generate
650	<	* @return a stream of {@code long} values
650	>	* @return a stream of pseudorandom {@code long} values
651		* @throws IllegalArgumentException if {@code streamSize} is
652	<	* less than zero
652	>	*         less than zero
653		*/
654		public LongStream longs(long streamSize) {
655		if (streamSize < 0L)
656	<	throw new IllegalArgumentException("negative Stream size");
656	>	throw new IllegalArgumentException(BadSize);
657		return StreamSupport.longStream
658		(new RandomLongsSpliterator
659		(this, 0L, streamSize, Long.MAX_VALUE, 0L),
#	Line 694 | Line 661 | public class SplittableRandom {
661		}
662
663		/**
664	<	* Returns an effectively unlimited stream of pseudorandom {@code long}
665	<	* values.
664	>	* Returns an effectively unlimited stream of pseudorandom {@code
665	>	* long} values from this generator and/or one split from it.
666		*
667		* @implNote This method is implemented to be equivalent to {@code
668		* longs(Long.MAX_VALUE)}.
#	Line 710 | Line 677 | public class SplittableRandom {
677		}
678
679		/**
680	<	* Returns a stream with the given {@code streamSize} number of
680	>	* Returns a stream producing the given {@code streamSize} number of
681		* pseudorandom {@code long} values, each conforming to the
682		* given origin and bound.
683		*
#	Line 718 | Line 685 | public class SplittableRandom {
685		* @param randomNumberOrigin the origin of each random value
686		* @param randomNumberBound the bound of each random value
687		* @return a stream of pseudorandom {@code long} values,
688	<	* each with the given origin and bound.
688	>	*         each with the given origin and bound
689		* @throws IllegalArgumentException if {@code streamSize} is
690	<	* less than zero.
724	<	* @throws IllegalArgumentException if {@code randomNumberOrigin}
690	>	*         less than zero, or {@code randomNumberOrigin}
691		*         is greater than or equal to {@code randomNumberBound}
692		*/
693		public LongStream longs(long streamSize, long randomNumberOrigin,
694		long randomNumberBound) {
695		if (streamSize < 0L)
696	<	throw new IllegalArgumentException("negative Stream size");
696	>	throw new IllegalArgumentException(BadSize);
697		if (randomNumberOrigin >= randomNumberBound)
698	<	throw new IllegalArgumentException("bound must be greater than origin");
698	>	throw new IllegalArgumentException(BadRange);
699		return StreamSupport.longStream
700		(new RandomLongsSpliterator
701		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 746 | Line 712 | public class SplittableRandom {
712		* @param randomNumberOrigin the origin of each random value
713		* @param randomNumberBound the bound of each random value
714		* @return a stream of pseudorandom {@code long} values,
715	<	* each with the given origin and bound.
715	>	*         each with the given origin and bound
716		* @throws IllegalArgumentException if {@code randomNumberOrigin}
717		*         is greater than or equal to {@code randomNumberBound}
718		*/
719		public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
720		if (randomNumberOrigin >= randomNumberBound)
721	<	throw new IllegalArgumentException("bound must be greater than origin");
721	>	throw new IllegalArgumentException(BadRange);
722		return StreamSupport.longStream
723		(new RandomLongsSpliterator
724		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 760 | Line 726 | public class SplittableRandom {
726		}
727
728		/**
729	<	* Returns a stream with the given {@code streamSize} number of
730	<	* pseudorandom {@code double} values, each between {@code 0.0}
731	<	* (inclusive) and {@code 1.0} (exclusive).
729	>	* Returns a stream producing the given {@code streamSize} number of
730	>	* pseudorandom {@code double} values, each between zero
731	>	* (inclusive) and one (exclusive).
732		*
733		* @param streamSize the number of values to generate
734		* @return a stream of {@code double} values
735		* @throws IllegalArgumentException if {@code streamSize} is
736	<	* less than zero
736	>	*         less than zero
737		*/
738		public DoubleStream doubles(long streamSize) {
739		if (streamSize < 0L)
740	<	throw new IllegalArgumentException("negative Stream size");
740	>	throw new IllegalArgumentException(BadSize);
741		return StreamSupport.doubleStream
742		(new RandomDoublesSpliterator
743		(this, 0L, streamSize, Double.MAX_VALUE, 0.0),
#	Line 780 | Line 746 | public class SplittableRandom {
746
747		/**
748		* Returns an effectively unlimited stream of pseudorandom {@code
749	<	* double} values, each between {@code 0.0} (inclusive) and {@code
750	<	* 1.0} (exclusive).
749	>	* double} values, each between zero (inclusive) and one
750	>	* (exclusive).
751		*
752		* @implNote This method is implemented to be equivalent to {@code
753		* doubles(Long.MAX_VALUE)}.
#	Line 796 | Line 762 | public class SplittableRandom {
762		}
763
764		/**
765	<	* Returns a stream with the given {@code streamSize} number of
765	>	* Returns a stream producing the given {@code streamSize} number of
766		* pseudorandom {@code double} values, each conforming to the
767		* given origin and bound.
768		*
#	Line 804 | Line 770 | public class SplittableRandom {
770		* @param randomNumberOrigin the origin of each random value
771		* @param randomNumberBound the bound of each random value
772		* @return a stream of pseudorandom {@code double} values,
773	<	* each with the given origin and bound.
773	>	* each with the given origin and bound
774		* @throws IllegalArgumentException if {@code streamSize} is
775	<	* less than zero.
775	>	* less than zero
776		* @throws IllegalArgumentException if {@code randomNumberOrigin}
777		*         is greater than or equal to {@code randomNumberBound}
778		*/
779		public DoubleStream doubles(long streamSize, double randomNumberOrigin,
780		double randomNumberBound) {
781		if (streamSize < 0L)
782	<	throw new IllegalArgumentException("negative Stream size");
783	<	if (randomNumberOrigin >= randomNumberBound)
784	<	throw new IllegalArgumentException("bound must be greater than origin");
782	>	throw new IllegalArgumentException(BadSize);
783	>	if (!(randomNumberOrigin < randomNumberBound))
784	>	throw new IllegalArgumentException(BadRange);
785		return StreamSupport.doubleStream
786		(new RandomDoublesSpliterator
787		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 832 | Line 798 | public class SplittableRandom {
798		* @param randomNumberOrigin the origin of each random value
799		* @param randomNumberBound the bound of each random value
800		* @return a stream of pseudorandom {@code double} values,
801	<	* each with the given origin and bound.
801	>	* each with the given origin and bound
802		* @throws IllegalArgumentException if {@code randomNumberOrigin}
803		*         is greater than or equal to {@code randomNumberBound}
804		*/
805		public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
806	<	if (randomNumberOrigin >= randomNumberBound)
807	<	throw new IllegalArgumentException("bound must be greater than origin");
806	>	if (!(randomNumberOrigin < randomNumberBound))
807	>	throw new IllegalArgumentException(BadRange);
808		return StreamSupport.doubleStream
809		(new RandomDoublesSpliterator
810		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 847 | Line 813 | public class SplittableRandom {
813
814		/**
815		* Spliterator for int streams.  We multiplex the four int
816	<	* versions into one class by treating and bound < origin as
816	>	* versions into one class by treating a bound less than origin as
817		* unbounded, and also by treating "infinite" as equivalent to
818		* Long.MAX_VALUE. For splits, it uses the standard divide-by-two
819		* approach. The long and double versions of this class are
820		* identical except for types.
821		*/
822	<	static class RandomIntsSpliterator implements Spliterator.OfInt {
822	>	static final class RandomIntsSpliterator implements Spliterator.OfInt {
823		final SplittableRandom rng;
824		long index;
825		final long fence;
#	Line 896 | Line 862 | public class SplittableRandom {
862		long i = index, f = fence;
863		if (i < f) {
864		index = f;
865	+	SplittableRandom r = rng;
866		int o = origin, b = bound;
867		do {
868	<	consumer.accept(rng.internalNextInt(o, b));
868	>	consumer.accept(r.internalNextInt(o, b));
869		} while (++i < f);
870		}
871		}
#	Line 907 | Line 874 | public class SplittableRandom {
874		/**
875		* Spliterator for long streams.
876		*/
877	<	static class RandomLongsSpliterator implements Spliterator.OfLong {
877	>	static final class RandomLongsSpliterator implements Spliterator.OfLong {
878		final SplittableRandom rng;
879		long index;
880		final long fence;
#	Line 950 | Line 917 | public class SplittableRandom {
917		long i = index, f = fence;
918		if (i < f) {
919		index = f;
920	+	SplittableRandom r = rng;
921		long o = origin, b = bound;
922		do {
923	<	consumer.accept(rng.internalNextLong(o, b));
923	>	consumer.accept(r.internalNextLong(o, b));
924		} while (++i < f);
925		}
926		}
#	Line 962 | Line 930 | public class SplittableRandom {
930		/**
931		* Spliterator for double streams.
932		*/
933	<	static class RandomDoublesSpliterator implements Spliterator.OfDouble {
933	>	static final class RandomDoublesSpliterator implements Spliterator.OfDouble {
934		final SplittableRandom rng;
935		long index;
936		final long fence;
#	Line 1005 | Line 973 | public class SplittableRandom {
973		long i = index, f = fence;
974		if (i < f) {
975		index = f;
976	+	SplittableRandom r = rng;
977		double o = origin, b = bound;
978		do {
979	<	consumer.accept(rng.internalNextDouble(o, b));
979	>	consumer.accept(r.internalNextDouble(o, b));
980		} while (++i < f);
981		}
982		}
983		}
984
985		}
1017	–

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