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Comparing jsr166/src/main/java/util/SplittableRandom.java (file contents):
Revision 1.5 by dl, Thu Jul 11 23:14:45 2013 UTC vs.
Revision 1.18 by dl, Thu Aug 22 23:36:06 2013 UTC

#	Line 25 | Line 25
25
26		package java.util;
27
28	+	import java.security.SecureRandom;
29	+	import java.net.InetAddress;
30		import java.util.concurrent.atomic.AtomicLong;
29	–	import java.util.Spliterator;
31		import java.util.function.IntConsumer;
32		import java.util.function.LongConsumer;
33		import java.util.function.DoubleConsumer;
#	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
42	>	* generate subtasks. Class {@code 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 73 | Line 77 | import java.util.stream.DoubleStream;
77		*
78		* </ul>
79		*
80	+	* <p>Instances of {@code SplittableRandom} are not cryptographically
81	+	* secure.  Consider instead using {@link java.security.SecureRandom}
82	+	* in security-sensitive applications. Additionally,
83	+	* default-constructed instances do not use a cryptographically random
84	+	* seed unless the {@linkplain System#getProperty system property}
85	+	* {@code java.util.secureRandomSeed} is set to {@code true}.
86	+
87	+	*
88		* @author  Guy Steele
89		* @author  Doug Lea
90		* @since   1.8
#	Line 80 | Line 92 | import java.util.stream.DoubleStream;
92		public class SplittableRandom {
93
94		/*
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	–	/*
95		* Implementation Overview.
96		*
97		* This algorithm was inspired by the "DotMix" algorithm by
98		* Leiserson, Schardl, and Sukha "Deterministic Parallel
99		* Random-Number Generation for Dynamic-Multithreading Platforms",
100	<	* PPoPP 2012, but improves and extends it in several ways.
101	<	*
102	<	* The primary update step is simply to add a constant ("gamma")
103	<	* to the current seed, modulo a prime ("George"). However, the
104	<	* nextLong and nextInt methods do not return this value, but
105	<	* instead the results of bit-mixing transformations that produce
106	<	* more uniformly distributed sequences.
107	<	*
108	<	* "George" is the otherwise nameless (because it cannot be
109	<	* represented) prime number 2^64+13. Using a prime number larger
110	<	* than can fit in a long ensures that all possible long values
111	<	* can occur, plus 13 others that just get skipped over when they
112	<	* are encountered; see method addGammaModGeorge. For this to
113	<	* work, initial gamma values must be at least 13.
114	<	*
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
100	>	* PPoPP 2012, as well as those in "Parallel random numbers: as
101	>	* easy as 1, 2, 3" by Salmon, Morae, Dror, and Shaw, SC 2011.  It
102	>	* differs mainly in simplifying and cheapening operations.
103	>	*
104	>	* The primary update step (method nextSeed()) is to add a
105	>	* constant ("gamma") to the current (64 bit) seed, forming a
106	>	* simple sequence.  The seed and the gamma values for any two
107	>	* SplittableRandom instances are highly likely to be different.
108	>	*
109	>	* Methods nextLong, nextInt, and derivatives do not return the
110	>	* sequence (seed) values, but instead a hash-like bit-mix of
111	>	* their bits, producing more independently distributed sequences.
112	>	* For nextLong, the mix64 bit-mixing function computes the same
113	>	* value as the "64-bit finalizer" function in Austin Appleby's
114	>	* MurmurHash3 algorithm.  See
115		* http://code.google.com/p/smhasher/wiki/MurmurHash3 , which
116		* comments: "The constants for the finalizers were generated by a
117		* simple simulated-annealing algorithm, and both avalanche all
118	<	* bits of 'h' to within 0.25% bias." It also appears to work to
119	<	* use instead any of the variants proposed by David Stafford at
120	<	* http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html
121	<	* but these variants have not yet been tested as thoroughly
122	<	* in the context of the implementation of SplittableRandom.
123	<	*
124	<	* The mix32 function used for nextInt just consists of two of the
125	<	* five lines of mix64; avalanche testing shows that the 64-bit result
126	<	* has its top 32 bits avalanched well, though not the bottom 32 bits.
127	<	* DieHarder tests show that it is adequate for generating one
128	<	* random int from the 64-bit result of nextSeed.
129	<	*
130	<	* Support for the default (no-argument) constructor relies on an
131	<	* AtomicLong (defaultSeedGenerator) to help perform the
132	<	* equivalent of a split of a statically constructed
133	<	* SplittableRandom. Unlike other cases, this split must be
134	<	* performed in a thread-safe manner. We use
135	<	* AtomicLong.compareAndSet as the (typically) most efficient
136	<	* mechanism. To bootstrap, we start off using System.nanotime(),
137	<	* and update using another "genuinely random" constant
138	<	* DEFAULT_SEED_GAMMA. The default constructor uses GAMMA_GAMMA,
139	<	* not 0, for its splitSeed argument (addGammaModGeorge(0,
140	<	* GAMMA_GAMMA) == GAMMA_GAMMA) to reflect that each is split from
141	<	* this root generator, even though the root is not explicitly
142	<	* represented as a SplittableRandom.
118	>	* bits of 'h' to within 0.25% bias." The mix32 function is
119	>	* equivalent to (int)(mix64(seed) >>> 32), but faster because it
120	>	* omits a step that doesn't contribute to result.
121	>	*
122	>	* The split operation uses the current generator to form the seed
123	>	* and gamma for another SplittableRandom.  To conservatively
124	>	* avoid potential correlations between seed and value generation,
125	>	* gamma selection (method nextGamma) uses the "Mix13" constants
126	>	* for MurmurHash3 described by David Stafford
127	>	* (http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html)
128	>	* To avoid potential weaknesses in bit-mixing transformations, we
129	>	* restrict gammas to odd values with at least 12 and no more than
130	>	* 52 bits set.  Rather than rejecting candidates with too few or
131	>	* too many bits set, method nextGamma flips some bits (which has
132	>	* the effect of mapping at most 4 to any given gamma value).
133	>	* This reduces the effective set of 64bit odd gamma values by
134	>	* about 2<sup>14</sup>, a very tiny percentage, and serves as an
135	>	* automated screening for sequence constant selection that is
136	>	* left as an empirical decision in some other hashing and crypto
137	>	* algorithms.
138	>	*
139	>	* The resulting generator thus transforms a sequence in which
140	>	* (typically) many bits change on each step, with an inexpensive
141	>	* mixer with good (but less than cryptographically secure)
142	>	* avalanching.
143	>	*
144	>	* The default (no-argument) constructor, in essence, invokes
145	>	* split() for a common "seeder" SplittableRandom.  Unlike other
146	>	* cases, this split must be performed in a thread-safe manner, so
147	>	* we use an AtomicLong to represent the seed rather than use an
148	>	* explicit SplittableRandom. To bootstrap the seeder, we start
149	>	* off using a seed based on current time and host unless the
150	>	* SecureRandomSeed property is set. This serves as a
151	>	* slimmed-down (and insecure) variant of SecureRandom that also
152	>	* avoids stalls that may occur when using /dev/random.
153	>	*
154	>	* It is a relatively simple matter to apply the basic design here
155	>	* to use 128 bit seeds. However, emulating 128bit arithmetic and
156	>	* carrying around twice the state add more overhead than appears
157	>	* warranted for current usages.
158	>	*
159	>	* File organization: First the non-public methods that constitute
160	>	* the main algorithm, then the main public methods, followed by
161	>	* some custom spliterator classes needed for stream methods.
162		*/
163
164		/**
165	<	* The "genuinely random" value for producing new gamma values.
166	<	* The value is arbitrary, subject to the requirement that it be
167	<	* 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.
165	>	* The initial gamma value for (unsplit) SplittableRandoms. Must
166	>	* be odd with at least 12 and no more than 52 bits set. Currently
167	>	* set to the golden ratio scaled to 64bits.
168		*/
169	<	private static final long DEFAULT_SEED_GAMMA = 0xBD24B73A95FB84D9L;
169	>	private static final long INITIAL_GAMMA = 0x9e3779b97f4a7c15L;
170
171		/**
172		* The least non-zero value returned by nextDouble(). This value
#	Line 184 | Line 175 | public class SplittableRandom {
175		private static final double DOUBLE_UNIT = 1.0 / (1L << 53);
176
177		/**
178	<	* 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.
178	>	* The seed. Updated only via method nextSeed.
179		*/
180		private long seed;
181
182		/**
183	<	* The constant value added to seed (mod George) on each update.
183	>	* The step value.
184		*/
185		private final long gamma;
186
187		/**
188	<	* The next seed to use for splits. Propagated using
204	<	* addGammaModGeorge across instances.
205	<	*/
206	<	private final long nextSplit;
207	<
208	<	/**
209	<	* 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.
188	>	* Internal constructor used by all others except default constructor.
189		*/
190	<	private SplittableRandom(long seed, long splitSeed) {
190	>	private SplittableRandom(long seed, long gamma) {
191		this.seed = seed;
192	<	long s = splitSeed, g;
217	<	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;
192	>	this.gamma = gamma;
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
201	<	* 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	>	* Computes MurmurHash3 64bit mix function.
197	>	*/
198	>	private static long mix64(long z) {
199	>	z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL;
200	>	z = (z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L;
201	>	return z ^ (z >>> 33);
202		}
203
204		/**
205	<	* Updates in-place and returns seed.
248	<	* See above for explanation.
205	>	* Returns the 32 high bits of mix64(z) as int.
206		*/
207	<	private long nextSeed() {
208	<	return seed = addGammaModGeorge(seed, gamma);
207	>	private static int mix32(long z) {
208	>	z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL;
209	>	return (int)(((z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L) >>> 32);
210		}
211
212		/**
213	<	* Returns a bit-mixed transformation of its argument.
256	<	* See above for explanation.
213	>	* Returns the gamma value to use for a new split instance.
214		*/
215	<	private static long mix64(long z) {
216	<	z ^= (z >>> 33);
217	<	z *= 0xff51afd7ed558ccdL;
218	<	z ^= (z >>> 33);
219	<	z *= 0xc4ceb9fe1a85ec53L;
220	<	z ^= (z >>> 33);
264	<	return z;
215	>	private static long nextGamma(long z) {
216	>	z = (z ^ (z >>> 30)) * 0xbf58476d1ce4e5b9L; // Stafford "Mix13"
217	>	z = (z ^ (z >>> 27)) * 0x94d049bb133111ebL;
218	>	z = (z ^ (z >>> 31)) | 1L; // force to be odd
219	>	int n = Long.bitCount(z);  // ensure enough 0 and 1 bits
220	>	return (n < 12 || n > 52) ? z ^ 0xaaaaaaaaaaaaaaaaL : z;
221		}
222
223		/**
224	<	* Returns a bit-mixed int transformation of its argument.
269	<	* See above for explanation.
224	>	* Adds gamma to seed.
225		*/
226	<	private static int mix32(long z) {
227	<	z ^= (z >>> 33);
273	<	z *= 0xc4ceb9fe1a85ec53L;
274	<	return (int)(z >>> 32);
226	>	private long nextSeed() {
227	>	return seed += gamma;
228		}
229
230		/**
231	<	* Atomically updates and returns next seed for default constructor
231	>	* The seed generator for default constructors.
232		*/
233	<	private static long nextDefaultSeed() {
234	<	long oldSeed, newSeed;
235	<	do {
236	<	oldSeed = defaultSeedGenerator.get();
237	<	newSeed = addGammaModGeorge(oldSeed, DEFAULT_SEED_GAMMA);
238	<	} while (!defaultSeedGenerator.compareAndSet(oldSeed, newSeed));
239	<	return mix64(newSeed);
233	>	private static final AtomicLong seeder = new AtomicLong(initialSeed());
234	>
235	>	private static long initialSeed() {
236	>	try {  // ignore exceptions in accessing/parsing properties
237	>	String pp = System.getProperty
238	>	("java.util.secureRandomSeed");
239	>	if (pp != null && pp.equalsIgnoreCase("true")) {
240	>	byte[] seedBytes = java.security.SecureRandom.getSeed(8);
241	>	long s = (long)(seedBytes[0]) & 0xffL;
242	>	for (int i = 1; i < 8; ++i)
243	>	s = (s << 8) | ((long)(seedBytes[i]) & 0xffL);
244	>	return s;
245	>	}
246	>	} catch (Exception ignore) {
247	>	}
248	>	int hh = 0; // hashed host address
249	>	try {
250	>	hh = InetAddress.getLocalHost().hashCode();
251	>	} catch (Exception ignore) {
252	>	}
253	>	return (mix64((((long)hh) << 32) ^ System.currentTimeMillis()) ^
254	>	mix64(System.nanoTime()));
255		}
256
257	+	// IllegalArgumentException messages
258	+	static final String BadBound = "bound must be positive";
259	+	static final String BadRange = "bound must be greater than origin";
260	+	static final String BadSize  = "size must be non-negative";
261	+
262		/*
263		* Internal versions of nextX methods used by streams, as well as
264		* the public nextX(origin, bound) methods.  These exist mainly to
#	Line 332 | Line 305 | public class SplittableRandom {
305		long r = mix64(nextSeed());
306		if (origin < bound) {
307		long n = bound - origin, m = n - 1;
308	<	if ((n & m) == 0L) // power of two
308	>	if ((n & m) == 0L)  // power of two
309		r = (r & m) + origin;
310	<	else if (n > 0) { // reject over-represented candidates
310	>	else if (n > 0L) {  // reject over-represented candidates
311		for (long u = r >>> 1;            // ensure nonnegative
312	<	u + m - (r = u % n) < 0L;    // reject
312	>	u + m - (r = u % n) < 0L;    // rejection check
313		u = mix64(nextSeed()) >>> 1) // retry
314		;
315		r += origin;
316		}
317	<	else {             // range not representable as long
317	>	else {              // range not representable as long
318		while (r < origin || r >= bound)
319		r = mix64(nextSeed());
320		}
#	Line 361 | Line 334 | public class SplittableRandom {
334		int r = mix32(nextSeed());
335		if (origin < bound) {
336		int n = bound - origin, m = n - 1;
337	<	if ((n & m) == 0L)
337	>	if ((n & m) == 0)
338		r = (r & m) + origin;
339		else if (n > 0) {
340		for (int u = r >>> 1;
341	<	u + m - (r = u % n) < 0L;
341	>	u + m - (r = u % n) < 0;
342		u = mix32(nextSeed()) >>> 1)
343		;
344		r += origin;
#	Line 389 | Line 362 | public class SplittableRandom {
362		double r = (nextLong() >>> 11) * DOUBLE_UNIT;
363		if (origin < bound) {
364		r = r * (bound - origin) + origin;
365	<	if (r == bound) // correct for rounding
365	>	if (r >= bound) // correct for rounding
366		r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
367		}
368		return r;
#	Line 398 | Line 371 | public class SplittableRandom {
371		/* ---------------- public methods ---------------- */
372
373		/**
374	<	* Creates a new SplittableRandom instance using the given initial
375	<	* seed. Two SplittableRandom instances created with the same seed
376	<	* generate identical sequences of values.
374	>	* Creates a new SplittableRandom instance using the specified
375	>	* initial seed. SplittableRandom instances created with the same
376	>	* seed in the same program generate identical sequences of values.
377		*
378		* @param seed the initial seed
379		*/
380		public SplittableRandom(long seed) {
381	<	this(seed, 0);
381	>	this(seed, INITIAL_GAMMA);
382		}
383
384		/**
#	Line 414 | Line 387 | public class SplittableRandom {
387		* of those of any other instances in the current program; and
388		* may, and typically does, vary across program invocations.
389		*/
390	<	public SplittableRandom() {
391	<	this(nextDefaultSeed(), GAMMA_GAMMA);
390	>	public SplittableRandom() { // emulate seeder.split()
391	>	this.gamma = nextGamma(this.seed = seeder.addAndGet(INITIAL_GAMMA));
392		}
393
394		/**
#	Line 433 | Line 406 | public class SplittableRandom {
406		* @return the new SplittableRandom instance
407		*/
408		public SplittableRandom split() {
409	<	return new SplittableRandom(nextSeed(), nextSplit);
409	>	long s = nextSeed();
410	>	return new SplittableRandom(s, nextGamma(s));
411		}
412
413		/**
414		* Returns a pseudorandom {@code int} value.
415		*
416	<	* @return a pseudorandom value
416	>	* @return a pseudorandom {@code int} value
417		*/
418		public int nextInt() {
419		return mix32(nextSeed());
420		}
421
422		/**
423	<	* Returns a pseudorandom {@code int} value between 0 (inclusive)
423	>	* Returns a pseudorandom {@code int} value between zero (inclusive)
424		* and the specified bound (exclusive).
425		*
426	<	* @param bound the bound on the random number to be returned.  Must be
427	<	*        positive.
428	<	* @return a pseudorandom {@code int} value between {@code 0}
429	<	*         (inclusive) and the bound (exclusive).
456	<	* @exception IllegalArgumentException if the bound is not positive
426	>	* @param bound the upper bound (exclusive).  Must be positive.
427	>	* @return a pseudorandom {@code int} value between zero
428	>	*         (inclusive) and the bound (exclusive)
429	>	* @throws IllegalArgumentException if {@code bound} is not positive
430		*/
431		public int nextInt(int bound) {
432		if (bound <= 0)
433	<	throw new IllegalArgumentException("bound must be positive");
433	>	throw new IllegalArgumentException(BadBound);
434		// Specialize internalNextInt for origin 0
435		int r = mix32(nextSeed());
436		int m = bound - 1;
437	<	if ((bound & m) == 0L) // power of two
437	>	if ((bound & m) == 0) // power of two
438		r &= m;
439		else { // reject over-represented candidates
440		for (int u = r >>> 1;
441	<	u + m - (r = u % bound) < 0L;
441	>	u + m - (r = u % bound) < 0;
442		u = mix32(nextSeed()) >>> 1)
443		;
444		}
#	Line 479 | Line 452 | public class SplittableRandom {
452		* @param origin the least value returned
453		* @param bound the upper bound (exclusive)
454		* @return a pseudorandom {@code int} value between the origin
455	<	*         (inclusive) and the bound (exclusive).
456	<	* @exception IllegalArgumentException if {@code origin} is greater than
455	>	*         (inclusive) and the bound (exclusive)
456	>	* @throws IllegalArgumentException if {@code origin} is greater than
457		*         or equal to {@code bound}
458		*/
459		public int nextInt(int origin, int bound) {
460		if (origin >= bound)
461	<	throw new IllegalArgumentException("bound must be greater than origin");
461	>	throw new IllegalArgumentException(BadRange);
462		return internalNextInt(origin, bound);
463		}
464
465		/**
466		* Returns a pseudorandom {@code long} value.
467		*
468	<	* @return a pseudorandom value
468	>	* @return a pseudorandom {@code long} value
469		*/
470		public long nextLong() {
471		return mix64(nextSeed());
472		}
473
474		/**
475	<	* Returns a pseudorandom {@code long} value between 0 (inclusive)
475	>	* Returns a pseudorandom {@code long} value between zero (inclusive)
476		* and the specified bound (exclusive).
477		*
478	<	* @param bound the bound on the random number to be returned.  Must be
479	<	*        positive.
480	<	* @return a pseudorandom {@code long} value between {@code 0}
481	<	*         (inclusive) and the bound (exclusive).
509	<	* @exception IllegalArgumentException if the bound is not positive
478	>	* @param bound the upper bound (exclusive).  Must be positive.
479	>	* @return a pseudorandom {@code long} value between zero
480	>	*         (inclusive) and the bound (exclusive)
481	>	* @throws IllegalArgumentException if {@code bound} is not positive
482		*/
483		public long nextLong(long bound) {
484		if (bound <= 0)
485	<	throw new IllegalArgumentException("bound must be positive");
485	>	throw new IllegalArgumentException(BadBound);
486		// Specialize internalNextLong for origin 0
487		long r = mix64(nextSeed());
488		long m = bound - 1;
#	Line 532 | Line 504 | public class SplittableRandom {
504		* @param origin the least value returned
505		* @param bound the upper bound (exclusive)
506		* @return a pseudorandom {@code long} value between the origin
507	<	*         (inclusive) and the bound (exclusive).
508	<	* @exception IllegalArgumentException if {@code origin} is greater than
507	>	*         (inclusive) and the bound (exclusive)
508	>	* @throws IllegalArgumentException if {@code origin} is greater than
509		*         or equal to {@code bound}
510		*/
511		public long nextLong(long origin, long bound) {
512		if (origin >= bound)
513	<	throw new IllegalArgumentException("bound must be greater than origin");
513	>	throw new IllegalArgumentException(BadRange);
514		return internalNextLong(origin, bound);
515		}
516
517		/**
518	<	* Returns a pseudorandom {@code double} value between {@code 0.0}
519	<	* (inclusive) and {@code 1.0} (exclusive).
518	>	* Returns a pseudorandom {@code double} value between zero
519	>	* (inclusive) and one (exclusive).
520		*
521	<	* @return a pseudorandom value between {@code 0.0}
522	<	* (inclusive) and {@code 1.0} (exclusive)
521	>	* @return a pseudorandom {@code double} value between zero
522	>	*         (inclusive) and one (exclusive)
523		*/
524		public double nextDouble() {
525	<	return (nextLong() >>> 11) * DOUBLE_UNIT;
525	>	return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT;
526		}
527
528		/**
529		* Returns a pseudorandom {@code double} value between 0.0
530		* (inclusive) and the specified bound (exclusive).
531		*
532	<	* @param bound the bound on the random number to be returned.  Must be
533	<	*        positive.
534	<	* @return a pseudorandom {@code double} value between {@code 0.0}
563	<	*         (inclusive) and the bound (exclusive).
532	>	* @param bound the upper bound (exclusive).  Must be positive.
533	>	* @return a pseudorandom {@code double} value between zero
534	>	*         (inclusive) and the bound (exclusive)
535		* @throws IllegalArgumentException if {@code bound} is not positive
536		*/
537		public double nextDouble(double bound) {
538	<	if (bound <= 0.0)
539	<	throw new IllegalArgumentException("bound must be positive");
540	<	double result = nextDouble() * bound;
538	>	if (!(bound > 0.0))
539	>	throw new IllegalArgumentException(BadBound);
540	>	double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound;
541		return (result < bound) ?  result : // correct for rounding
542		Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
543		}
544
545		/**
546	<	* Returns a pseudorandom {@code double} value between the given
546	>	* Returns a pseudorandom {@code double} value between the specified
547		* origin (inclusive) and bound (exclusive).
548		*
549		* @param origin the least value returned
550	<	* @param bound the upper bound
550	>	* @param bound the upper bound (exclusive)
551		* @return a pseudorandom {@code double} value between the origin
552	<	*         (inclusive) and the bound (exclusive).
552	>	*         (inclusive) and the bound (exclusive)
553		* @throws IllegalArgumentException if {@code origin} is greater than
554		*         or equal to {@code bound}
555		*/
556		public double nextDouble(double origin, double bound) {
557	<	if (origin >= bound)
558	<	throw new IllegalArgumentException("bound must be greater than origin");
557	>	if (!(origin < bound))
558	>	throw new IllegalArgumentException(BadRange);
559		return internalNextDouble(origin, bound);
560		}
561
562	+	/**
563	+	* Returns a pseudorandom {@code boolean} value.
564	+	*
565	+	* @return a pseudorandom {@code boolean} value
566	+	*/
567	+	public boolean nextBoolean() {
568	+	return mix32(nextSeed()) < 0;
569	+	}
570	+
571		// stream methods, coded in a way intended to better isolate for
572		// maintenance purposes the small differences across forms.
573
574		/**
575	<	* Returns a stream with the given {@code streamSize} number of
576	<	* pseudorandom {@code int} values.
575	>	* Returns a stream producing the given {@code streamSize} number
576	>	* of pseudorandom {@code int} values from this generator and/or
577	>	* one split from it.
578		*
579		* @param streamSize the number of values to generate
580		* @return a stream of pseudorandom {@code int} values
581		* @throws IllegalArgumentException if {@code streamSize} is
582	<	* less than zero
582	>	*         less than zero
583		*/
584		public IntStream ints(long streamSize) {
585		if (streamSize < 0L)
586	<	throw new IllegalArgumentException("negative Stream size");
586	>	throw new IllegalArgumentException(BadSize);
587		return StreamSupport.intStream
588		(new RandomIntsSpliterator
589		(this, 0L, streamSize, Integer.MAX_VALUE, 0),
#	Line 611 | Line 592 | public class SplittableRandom {
592
593		/**
594		* Returns an effectively unlimited stream of pseudorandom {@code int}
595	<	* values
595	>	* values from this generator and/or one split from it.
596		*
597		* @implNote This method is implemented to be equivalent to {@code
598		* ints(Long.MAX_VALUE)}.
#	Line 626 | Line 607 | public class SplittableRandom {
607		}
608
609		/**
610	<	* Returns a stream with the given {@code streamSize} number of
611	<	* pseudorandom {@code int} values, each conforming to the given
612	<	* origin and bound.
610	>	* Returns a stream producing the given {@code streamSize} number
611	>	* of pseudorandom {@code int} values from this generator and/or one split
612	>	* from it; each value conforms to the given origin (inclusive) and bound
613	>	* (exclusive).
614		*
615		* @param streamSize the number of values to generate
616	<	* @param randomNumberOrigin the origin of each random value
617	<	* @param randomNumberBound the bound of each random value
616	>	* @param randomNumberOrigin the origin (inclusive) of each random value
617	>	* @param randomNumberBound the bound (exclusive) of each random value
618		* @return a stream of pseudorandom {@code int} values,
619	<	* each with the given origin and bound.
619	>	*         each with the given origin (inclusive) and bound (exclusive)
620		* @throws IllegalArgumentException if {@code streamSize} is
621	<	* less than zero.
640	<	* @throws IllegalArgumentException if {@code randomNumberOrigin}
621	>	*         less than zero, or {@code randomNumberOrigin}
622		*         is greater than or equal to {@code randomNumberBound}
623		*/
624		public IntStream ints(long streamSize, int randomNumberOrigin,
625		int randomNumberBound) {
626		if (streamSize < 0L)
627	<	throw new IllegalArgumentException("negative Stream size");
627	>	throw new IllegalArgumentException(BadSize);
628		if (randomNumberOrigin >= randomNumberBound)
629	<	throw new IllegalArgumentException("bound must be greater than origin");
629	>	throw new IllegalArgumentException(BadRange);
630		return StreamSupport.intStream
631		(new RandomIntsSpliterator
632		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 654 | Line 635 | public class SplittableRandom {
635
636		/**
637		* Returns an effectively unlimited stream of pseudorandom {@code
638	<	* int} values, each conforming to the given origin and bound.
638	>	* int} values from this generator and/or one split from it; each value
639	>	* conforms to the given origin (inclusive) and bound (exclusive).
640		*
641		* @implNote This method is implemented to be equivalent to {@code
642		* ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
643		*
644	<	* @param randomNumberOrigin the origin of each random value
645	<	* @param randomNumberBound the bound of each random value
644	>	* @param randomNumberOrigin the origin (inclusive) of each random value
645	>	* @param randomNumberBound the bound (exclusive) of each random value
646		* @return a stream of pseudorandom {@code int} values,
647	<	* each with the given origin and bound.
647	>	*         each with the given origin (inclusive) and bound (exclusive)
648		* @throws IllegalArgumentException if {@code randomNumberOrigin}
649		*         is greater than or equal to {@code randomNumberBound}
650		*/
651		public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
652		if (randomNumberOrigin >= randomNumberBound)
653	<	throw new IllegalArgumentException("bound must be greater than origin");
653	>	throw new IllegalArgumentException(BadRange);
654		return StreamSupport.intStream
655		(new RandomIntsSpliterator
656		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 676 | Line 658 | public class SplittableRandom {
658		}
659
660		/**
661	<	* Returns a stream with the given {@code streamSize} number of
662	<	* pseudorandom {@code long} values.
661	>	* Returns a stream producing the given {@code streamSize} number
662	>	* of pseudorandom {@code long} values from this generator and/or
663	>	* one split from it.
664		*
665		* @param streamSize the number of values to generate
666	<	* @return a stream of {@code long} values
666	>	* @return a stream of pseudorandom {@code long} values
667		* @throws IllegalArgumentException if {@code streamSize} is
668	<	* less than zero
668	>	*         less than zero
669		*/
670		public LongStream longs(long streamSize) {
671		if (streamSize < 0L)
672	<	throw new IllegalArgumentException("negative Stream size");
672	>	throw new IllegalArgumentException(BadSize);
673		return StreamSupport.longStream
674		(new RandomLongsSpliterator
675		(this, 0L, streamSize, Long.MAX_VALUE, 0L),
#	Line 694 | Line 677 | public class SplittableRandom {
677		}
678
679		/**
680	<	* Returns an effectively unlimited stream of pseudorandom {@code long}
681	<	* values.
680	>	* Returns an effectively unlimited stream of pseudorandom {@code
681	>	* long} values from this generator and/or one split from it.
682		*
683		* @implNote This method is implemented to be equivalent to {@code
684		* longs(Long.MAX_VALUE)}.
#	Line 710 | Line 693 | public class SplittableRandom {
693		}
694
695		/**
696	<	* Returns a stream with the given {@code streamSize} number of
697	<	* pseudorandom {@code long} values, each conforming to the
698	<	* given origin and bound.
696	>	* Returns a stream producing the given {@code streamSize} number of
697	>	* pseudorandom {@code long} values from this generator and/or one split
698	>	* from it; each value conforms to the given origin (inclusive) and bound
699	>	* (exclusive).
700		*
701		* @param streamSize the number of values to generate
702	<	* @param randomNumberOrigin the origin of each random value
703	<	* @param randomNumberBound the bound of each random value
702	>	* @param randomNumberOrigin the origin (inclusive) of each random value
703	>	* @param randomNumberBound the bound (exclusive) of each random value
704		* @return a stream of pseudorandom {@code long} values,
705	<	* each with the given origin and bound.
705	>	*         each with the given origin (inclusive) and bound (exclusive)
706		* @throws IllegalArgumentException if {@code streamSize} is
707	<	* less than zero.
724	<	* @throws IllegalArgumentException if {@code randomNumberOrigin}
707	>	*         less than zero, or {@code randomNumberOrigin}
708		*         is greater than or equal to {@code randomNumberBound}
709		*/
710		public LongStream longs(long streamSize, long randomNumberOrigin,
711		long randomNumberBound) {
712		if (streamSize < 0L)
713	<	throw new IllegalArgumentException("negative Stream size");
713	>	throw new IllegalArgumentException(BadSize);
714		if (randomNumberOrigin >= randomNumberBound)
715	<	throw new IllegalArgumentException("bound must be greater than origin");
715	>	throw new IllegalArgumentException(BadRange);
716		return StreamSupport.longStream
717		(new RandomLongsSpliterator
718		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 738 | Line 721 | public class SplittableRandom {
721
722		/**
723		* Returns an effectively unlimited stream of pseudorandom {@code
724	<	* long} values, each conforming to the given origin and bound.
724	>	* long} values from this generator and/or one split from it; each value
725	>	* conforms to the given origin (inclusive) and bound (exclusive).
726		*
727		* @implNote This method is implemented to be equivalent to {@code
728		* longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
729		*
730	<	* @param randomNumberOrigin the origin of each random value
731	<	* @param randomNumberBound the bound of each random value
730	>	* @param randomNumberOrigin the origin (inclusive) of each random value
731	>	* @param randomNumberBound the bound (exclusive) of each random value
732		* @return a stream of pseudorandom {@code long} values,
733	<	* each with the given origin and bound.
733	>	*         each with the given origin (inclusive) and bound (exclusive)
734		* @throws IllegalArgumentException if {@code randomNumberOrigin}
735		*         is greater than or equal to {@code randomNumberBound}
736		*/
737		public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
738		if (randomNumberOrigin >= randomNumberBound)
739	<	throw new IllegalArgumentException("bound must be greater than origin");
739	>	throw new IllegalArgumentException(BadRange);
740		return StreamSupport.longStream
741		(new RandomLongsSpliterator
742		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 760 | Line 744 | public class SplittableRandom {
744		}
745
746		/**
747	<	* Returns a stream with the given {@code streamSize} number of
748	<	* pseudorandom {@code double} values, each between {@code 0.0}
749	<	* (inclusive) and {@code 1.0} (exclusive).
747	>	* Returns a stream producing the given {@code streamSize} number of
748	>	* pseudorandom {@code double} values from this generator and/or one split
749	>	* from it; each value is between zero (inclusive) and one (exclusive).
750		*
751		* @param streamSize the number of values to generate
752		* @return a stream of {@code double} values
753		* @throws IllegalArgumentException if {@code streamSize} is
754	<	* less than zero
754	>	*         less than zero
755		*/
756		public DoubleStream doubles(long streamSize) {
757		if (streamSize < 0L)
758	<	throw new IllegalArgumentException("negative Stream size");
758	>	throw new IllegalArgumentException(BadSize);
759		return StreamSupport.doubleStream
760		(new RandomDoublesSpliterator
761		(this, 0L, streamSize, Double.MAX_VALUE, 0.0),
#	Line 780 | Line 764 | public class SplittableRandom {
764
765		/**
766		* Returns an effectively unlimited stream of pseudorandom {@code
767	<	* double} values, each between {@code 0.0} (inclusive) and {@code
768	<	* 1.0} (exclusive).
767	>	* double} values from this generator and/or one split from it; each value
768	>	* is between zero (inclusive) and one (exclusive).
769		*
770		* @implNote This method is implemented to be equivalent to {@code
771		* doubles(Long.MAX_VALUE)}.
#	Line 796 | Line 780 | public class SplittableRandom {
780		}
781
782		/**
783	<	* Returns a stream with the given {@code streamSize} number of
784	<	* pseudorandom {@code double} values, each conforming to the
785	<	* given origin and bound.
783	>	* Returns a stream producing the given {@code streamSize} number of
784	>	* pseudorandom {@code double} values from this generator and/or one split
785	>	* from it; each value conforms to the given origin (inclusive) and bound
786	>	* (exclusive).
787		*
788		* @param streamSize the number of values to generate
789	<	* @param randomNumberOrigin the origin of each random value
790	<	* @param randomNumberBound the bound of each random value
789	>	* @param randomNumberOrigin the origin (inclusive) of each random value
790	>	* @param randomNumberBound the bound (exclusive) of each random value
791		* @return a stream of pseudorandom {@code double} values,
792	<	* each with the given origin and bound.
792	>	*         each with the given origin (inclusive) and bound (exclusive)
793		* @throws IllegalArgumentException if {@code streamSize} is
794	<	* less than zero.
794	>	*         less than zero
795		* @throws IllegalArgumentException if {@code randomNumberOrigin}
796		*         is greater than or equal to {@code randomNumberBound}
797		*/
798		public DoubleStream doubles(long streamSize, double randomNumberOrigin,
799		double randomNumberBound) {
800		if (streamSize < 0L)
801	<	throw new IllegalArgumentException("negative Stream size");
802	<	if (randomNumberOrigin >= randomNumberBound)
803	<	throw new IllegalArgumentException("bound must be greater than origin");
801	>	throw new IllegalArgumentException(BadSize);
802	>	if (!(randomNumberOrigin < randomNumberBound))
803	>	throw new IllegalArgumentException(BadRange);
804		return StreamSupport.doubleStream
805		(new RandomDoublesSpliterator
806		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 824 | Line 809 | public class SplittableRandom {
809
810		/**
811		* Returns an effectively unlimited stream of pseudorandom {@code
812	<	* double} values, each conforming to the given origin and bound.
812	>	* double} values from this generator and/or one split from it; each value
813	>	* conforms to the given origin (inclusive) and bound (exclusive).
814		*
815		* @implNote This method is implemented to be equivalent to {@code
816		* doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
817		*
818	<	* @param randomNumberOrigin the origin of each random value
819	<	* @param randomNumberBound the bound of each random value
818	>	* @param randomNumberOrigin the origin (inclusive) of each random value
819	>	* @param randomNumberBound the bound (exclusive) of each random value
820		* @return a stream of pseudorandom {@code double} values,
821	<	* each with the given origin and bound.
821	>	*         each with the given origin (inclusive) and bound (exclusive)
822		* @throws IllegalArgumentException if {@code randomNumberOrigin}
823		*         is greater than or equal to {@code randomNumberBound}
824		*/
825		public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
826	<	if (randomNumberOrigin >= randomNumberBound)
827	<	throw new IllegalArgumentException("bound must be greater than origin");
826	>	if (!(randomNumberOrigin < randomNumberBound))
827	>	throw new IllegalArgumentException(BadRange);
828		return StreamSupport.doubleStream
829		(new RandomDoublesSpliterator
830		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 847 | Line 833 | public class SplittableRandom {
833
834		/**
835		* Spliterator for int streams.  We multiplex the four int
836	<	* versions into one class by treating and bound < origin as
836	>	* versions into one class by treating a bound less than origin as
837		* unbounded, and also by treating "infinite" as equivalent to
838		* Long.MAX_VALUE. For splits, it uses the standard divide-by-two
839		* approach. The long and double versions of this class are
840		* identical except for types.
841		*/
842	<	static class RandomIntsSpliterator implements Spliterator.OfInt {
842	>	static final class RandomIntsSpliterator implements Spliterator.OfInt {
843		final SplittableRandom rng;
844		long index;
845		final long fence;
#	Line 896 | Line 882 | public class SplittableRandom {
882		long i = index, f = fence;
883		if (i < f) {
884		index = f;
885	+	SplittableRandom r = rng;
886		int o = origin, b = bound;
887		do {
888	<	consumer.accept(rng.internalNextInt(o, b));
888	>	consumer.accept(r.internalNextInt(o, b));
889		} while (++i < f);
890		}
891		}
#	Line 907 | Line 894 | public class SplittableRandom {
894		/**
895		* Spliterator for long streams.
896		*/
897	<	static class RandomLongsSpliterator implements Spliterator.OfLong {
897	>	static final class RandomLongsSpliterator implements Spliterator.OfLong {
898		final SplittableRandom rng;
899		long index;
900		final long fence;
#	Line 950 | Line 937 | public class SplittableRandom {
937		long i = index, f = fence;
938		if (i < f) {
939		index = f;
940	+	SplittableRandom r = rng;
941		long o = origin, b = bound;
942		do {
943	<	consumer.accept(rng.internalNextLong(o, b));
943	>	consumer.accept(r.internalNextLong(o, b));
944		} while (++i < f);
945		}
946		}
#	Line 962 | Line 950 | public class SplittableRandom {
950		/**
951		* Spliterator for double streams.
952		*/
953	<	static class RandomDoublesSpliterator implements Spliterator.OfDouble {
953	>	static final class RandomDoublesSpliterator implements Spliterator.OfDouble {
954		final SplittableRandom rng;
955		long index;
956		final long fence;
#	Line 1005 | Line 993 | public class SplittableRandom {
993		long i = index, f = fence;
994		if (i < f) {
995		index = f;
996	+	SplittableRandom r = rng;
997		double o = origin, b = bound;
998		do {
999	<	consumer.accept(rng.internalNextDouble(o, b));
999	>	consumer.accept(r.internalNextDouble(o, b));
1000		} while (++i < f);
1001		}
1002		}
1003		}
1004
1005		}
1017	–

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