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Comparing jsr166/src/main/java/util/SplittableRandom.java (file contents):
Revision 1.10 by jsr166, Sun Jul 14 08:06:49 2013 UTC vs.
Revision 1.22 by dl, Fri Sep 20 09:38:07 2013 UTC

#	Line 25 | Line 25
25
26		package java.util;
27
28	+	import java.security.SecureRandom;
29	+	import java.net.NetworkInterface;
30	+	import java.util.Enumeration;
31		import java.util.concurrent.atomic.AtomicLong;
29	–	import java.util.Spliterator;
32		import java.util.function.IntConsumer;
33		import java.util.function.LongConsumer;
34		import java.util.function.DoubleConsumer;
#	Line 38 | Line 40 | import java.util.stream.DoubleStream;
40		/**
41		* A generator of uniform pseudorandom values applicable for use in
42		* (among other contexts) isolated parallel computations that may
43	<	* generate subtasks. Class SplittableRandom supports methods for
43	>	* generate subtasks. Class {@code SplittableRandom} supports methods for
44		* producing pseudorandom numbers of type {@code int}, {@code long},
45		* and {@code double} with similar usages as for class
46		* {@link java.util.Random} but differs in the following ways:
#	Line 51 | Line 53 | import java.util.stream.DoubleStream;
53		* href="http://www.phy.duke.edu/~rgb/General/dieharder.php"> version
54		* 3.31.1</a>.) These tests validate only the methods for certain
55		* types and ranges, but similar properties are expected to hold, at
56	<	* least approximately, for others as well.  </li>
56	>	* least approximately, for others as well. The <em>period</em>
57	>	* (length of any series of generated values before it repeats) is at
58	>	* least 2<sup>64</sup>. </li>
59		*
60		* <li> Method {@link #split} constructs and returns a new
61		* SplittableRandom instance that shares no mutable state with the
#	Line 74 | Line 78 | import java.util.stream.DoubleStream;
78		*
79		* </ul>
80		*
81	+	* <p>Instances of {@code SplittableRandom} are not cryptographically
82	+	* secure.  Consider instead using {@link java.security.SecureRandom}
83	+	* in security-sensitive applications. Additionally,
84	+	* default-constructed instances do not use a cryptographically random
85	+	* seed unless the {@linkplain System#getProperty system property}
86	+	* {@code java.util.secureRandomSeed} is set to {@code true}.
87	+	*
88		* @author  Guy Steele
89		* @author  Doug Lea
90		* @since   1.8
#	Line 81 | Line 92 | import java.util.stream.DoubleStream;
92		public class SplittableRandom {
93
94		/*
84	–	* File organization: First the non-public methods that constitute
85	–	* the main algorithm, then the main public methods, followed by
86	–	* some custom spliterator classes needed for stream methods.
87	–	*
88	–	* Credits: Primary algorithm and code by Guy Steele.  Stream
89	–	* support methods by Doug Lea.  Documentation jointly produced
90	–	* with additional help from Brian Goetz.
91	–	*/
92	–
93	–	/*
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.
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 function is based on David Stafford's
113	>	* (http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html)
114	>	* "Mix13" variant of the "64-bit finalizer" function in Austin
115	>	* Appleby's MurmurHash3 algorithm See
116	>	* http://code.google.com/p/smhasher/wiki/MurmurHash3 . The mix32
117	>	* function is based on Stafford's Mix04 mix function, but returns
118	>	* the upper 32 bits cast as int.
119	>	*
120	>	* The split operation uses the current generator to form the seed
121	>	* and gamma for another SplittableRandom.  To conservatively
122	>	* avoid potential correlations between seed and value generation,
123	>	* gamma selection (method mixGamma) uses different
124	>	* (Murmurhash3's) mix constants.  To avoid potential weaknesses
125	>	* in bit-mixing transformations, we restrict gammas to odd values
126	>	* with at least 24 0-1 or 1-0 bit transitions.  Rather than
127	>	* rejecting candidates with too few or too many bits set, method
128	>	* mixGamma flips some bits (which has the effect of mapping at
129	>	* most 4 to any given gamma value).  This reduces the effective
130	>	* set of 64bit odd gamma values by about 2%, and serves as an
131	>	* automated screening for sequence constant selection that is
132	>	* left as an empirical decision in some other hashing and crypto
133	>	* algorithms.
134	>	*
135	>	* The resulting generator thus transforms a sequence in which
136	>	* (typically) many bits change on each step, with an inexpensive
137	>	* mixer with good (but less than cryptographically secure)
138	>	* avalanching.
139	>	*
140	>	* The default (no-argument) constructor, in essence, invokes
141	>	* split() for a common "defaultGen" SplittableRandom.  Unlike
142	>	* other cases, this split must be performed in a thread-safe
143	>	* manner, so we use an AtomicLong to represent the seed rather
144	>	* than use an explicit SplittableRandom. To bootstrap the
145	>	* defaultGen, we start off using a seed based on current time and
146	>	* network interface address unless the java.util.secureRandomSeed
147	>	* property is set. This serves as a slimmed-down (and insecure)
148	>	* variant of SecureRandom that also avoids stalls that may occur
149	>	* when using /dev/random.
150	>	*
151	>	* It is a relatively simple matter to apply the basic design here
152	>	* to use 128 bit seeds. However, emulating 128bit arithmetic and
153	>	* carrying around twice the state add more overhead than appears
154	>	* warranted for current usages.
155		*
156	<	* The primary update step (see method nextSeed()) is simply to
157	<	* add a constant ("gamma") to the current seed, modulo a prime
158	<	* ("George"). However, the nextLong and nextInt methods do not
104	<	* return this value, but instead the results of bit-mixing
105	<	* transformations that produce more uniformly distributed
106	<	* 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	<	*
115	<	* The value of gamma differs for each instance across a series of
116	<	* splits, and is generated using a slightly stripped-down variant
117	<	* of the same algorithm, but operating across calls to split(),
118	<	* not calls to nextSeed(): Each instance carries the state of
119	<	* this generator as nextSplit, and uses mix64(nextSplit) as its
120	<	* own gamma value. Computations of gammas themselves use a fixed
121	<	* constant as the second argument to the addGammaModGeorge
122	<	* function, GAMMA_GAMMA, a "genuinely random" number from a
123	<	* radioactive decay reading (obtained from
124	<	* http://www.fourmilab.ch/hotbits/) meeting the above range
125	<	* constraint. Using a fixed constant maintains the invariant that
126	<	* the value of gamma is the same for every instance that is at
127	<	* the same split-distance from their common root. (Note: there is
128	<	* nothing especially magic about obtaining this constant from a
129	<	* "truly random" physical source rather than just choosing one
130	<	* arbitrarily; using "hotbits" was merely an aesthetically pleasing
131	<	* choice.  In either case, good statistical behavior of the
132	<	* algorithm should be, and was, verified by using the DieHarder
133	<	* test suite.)
134	<	*
135	<	* The mix64 bit-mixing function called by nextLong and other
136	<	* methods computes the same value as the "64-bit finalizer"
137	<	* function in Austin Appleby's MurmurHash3 algorithm.  See
138	<	* http://code.google.com/p/smhasher/wiki/MurmurHash3 , which
139	<	* comments: "The constants for the finalizers were generated by a
140	<	* simple simulated-annealing algorithm, and both avalanche all
141	<	* bits of 'h' to within 0.25% bias." It also appears to work to
142	<	* use instead any of the variants proposed by David Stafford at
143	<	* http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html
144	<	* but these variants have not yet been tested as thoroughly
145	<	* in the context of the implementation of SplittableRandom.
146	<	*
147	<	* The mix32 function used for nextInt just consists of two of the
148	<	* five lines of mix64; avalanche testing shows that the 64-bit result
149	<	* has its top 32 bits avalanched well, though not the bottom 32 bits.
150	<	* DieHarder tests show that it is adequate for generating one
151	<	* random int from the 64-bit result of nextSeed.
152	<	*
153	<	* Support for the default (no-argument) constructor relies on an
154	<	* AtomicLong (defaultSeedGenerator) to help perform the
155	<	* equivalent of a split of a statically constructed
156	<	* SplittableRandom. Unlike other cases, this split must be
157	<	* performed in a thread-safe manner. We use
158	<	* AtomicLong.compareAndSet as the (typically) most efficient
159	<	* mechanism. To bootstrap, we start off using System.nanotime(),
160	<	* and update using another "genuinely random" constant
161	<	* DEFAULT_SEED_GAMMA. The default constructor uses GAMMA_GAMMA,
162	<	* not 0, for its splitSeed argument (addGammaModGeorge(0,
163	<	* GAMMA_GAMMA) == GAMMA_GAMMA) to reflect that each is split from
164	<	* this root generator, even though the root is not explicitly
165	<	* represented as a SplittableRandom.
166	<	*/
167	<
168	<	/**
169	<	* The "genuinely random" value for producing new gamma values.
170	<	* The value is arbitrary, subject to the requirement that it be
171	<	* greater or equal to 13.
172	<	*/
173	<	private static final long GAMMA_GAMMA = 0xF2281E2DBA6606F3L;
174	<
175	<	/**
176	<	* The "genuinely random" seed update value for default constructors.
177	<	* The value is arbitrary, subject to the requirement that it be
178	<	* greater or equal to 13.
156	>	* File organization: First the non-public methods that constitute
157	>	* the main algorithm, then the main public methods, followed by
158	>	* some custom spliterator classes needed for stream methods.
159		*/
180	–	private static final long DEFAULT_SEED_GAMMA = 0xBD24B73A95FB84D9L;
160
161		/**
162	<	* The least non-zero value returned by nextDouble(). This value
163	<	* is scaled by a random value of 53 bits to produce a result.
162	>	* The golden ratio scaled to 64bits, used as the initial gamma
163	>	* value for (unsplit) SplittableRandoms.
164		*/
165	<	private static final double DOUBLE_UNIT = 1.0 / (1L << 53);
165	>	private static final long GOLDEN_GAMMA = 0x9e3779b97f4a7c15L;
166
167		/**
168	<	* The next seed for default constructors.
168	>	* The least non-zero value returned by nextDouble(). This value
169	>	* is scaled by a random value of 53 bits to produce a result.
170		*/
171	<	private static final AtomicLong defaultSeedGenerator =
192	<	new AtomicLong(System.nanoTime());
171	>	private static final double DOUBLE_ULP = 1.0 / (1L << 53);
172
173		/**
174	<	* The seed, updated only via method nextSeed.
174	>	* The seed. Updated only via method nextSeed.
175		*/
176		private long seed;
177
178		/**
179	<	* The constant value added to seed (mod George) on each update.
179	>	* The step value.
180		*/
181		private final long gamma;
182
183		/**
184	<	* The next seed to use for splits. Propagated using
206	<	* addGammaModGeorge across instances.
207	<	*/
208	<	private final long nextSplit;
209	<
210	<	/**
211	<	* Adds the given gamma value, g, to the given seed value s, mod
212	<	* George (2^64+13). We regard s and g as unsigned values
213	<	* (ranging from 0 to 2^64-1). We add g to s either once or twice
214	<	* (mod George) as necessary to produce an (unsigned) result less
215	<	* than 2^64.  We require that g must be at least 13. This
216	<	* guarantees that if (s+g) mod George >= 2^64 then (s+g+g) mod
217	<	* George < 2^64; thus we need only a conditional, not a loop,
218	<	* to be sure of getting a representable value.
219	<	*
220	<	* @param s a seed value
221	<	* @param g a gamma value, 13 <= g (as unsigned)
184	>	* Internal constructor used by all others except default constructor.
185		*/
186	<	private static long addGammaModGeorge(long s, long g) {
187	<	long p = s + g;
188	<	if (Long.compareUnsigned(p, g) >= 0)
226	<	return p;
227	<	long q = p - 13L;
228	<	return (Long.compareUnsigned(p, 13L) >= 0) ? q : (q + g);
186	>	private SplittableRandom(long seed, long gamma) {
187	>	this.seed = seed;
188	>	this.gamma = gamma;
189		}
190
191		/**
192	<	* Returns a bit-mixed transformation of its argument.
233	<	* See above for explanation.
192	>	* Computes Stafford variant 13 of 64bit mix function.
193		*/
194		private static long mix64(long z) {
195	<	z ^= (z >>> 33);
196	<	z *= 0xff51afd7ed558ccdL;
197	<	z ^= (z >>> 33);
239	<	z *= 0xc4ceb9fe1a85ec53L;
240	<	z ^= (z >>> 33);
241	<	return z;
195	>	z *= 0xbf58476d1ce4e5b9L;
196	>	z = (z ^ (z >>> 32)) * 0x94d049bb133111ebL;
197	>	return z ^ (z >>> 32);
198		}
199
200		/**
201	<	* Returns a bit-mixed int transformation of its argument.
246	<	* See above for explanation.
201	>	* Returns the 32 high bits of Stafford variant 4 mix64 function as int.
202		*/
203		private static int mix32(long z) {
204	<	z ^= (z >>> 33);
205	<	z *= 0xc4ceb9fe1a85ec53L;
251	<	return (int)(z >>> 32);
204	>	z *= 0x62a9d9ed799705f5L;
205	>	return (int)(((z ^ (z >>> 28)) * 0xcb24d0a5c88c35b3L) >>> 32);
206		}
207
208		/**
209	<	* Internal constructor used by all other constructors and by
256	<	* method split. Establishes the initial seed for this instance,
257	<	* and uses the given splitSeed to establish gamma, as well as the
258	<	* nextSplit to use by this instance. The loop to skip ineligible
259	<	* gammas very rarely iterates, and does so at most 13 times.
209	>	* Returns the gamma value to use for a new split instance.
210		*/
211	<	private SplittableRandom(long seed, long splitSeed) {
212	<	this.seed = seed;
213	<	long s = splitSeed, g;
214	<	do { // ensure gamma >= 13, considered as an unsigned integer
215	<	s = addGammaModGeorge(s, GAMMA_GAMMA);
216	<	g = mix64(s);
267	<	} while (Long.compareUnsigned(g, 13L) < 0);
268	<	this.gamma = g;
269	<	this.nextSplit = s;
211	>	private static long mixGamma(long z) {
212	>	z *= 0xff51afd7ed558ccdL;                   // MurmurHash3 mix constants
213	>	z = (z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L;
214	>	z = (z ^ (z >>> 33)) | 1L;                  // force to be odd
215	>	int n = Long.bitCount(z ^ (z >>> 1));       // ensure enough transitions
216	>	return (n < 24) ? z ^ 0xaaaaaaaaaaaaaaaaL : z;
217		}
218
219		/**
220	<	* Updates in-place and returns seed.
274	<	* See above for explanation.
220	>	* Adds gamma to seed.
221		*/
222		private long nextSeed() {
223	<	return seed = addGammaModGeorge(seed, gamma);
223	>	return seed += gamma;
224		}
225
226		/**
227	<	* Atomically updates and returns next seed for default constructor.
227	>	* The seed generator for default constructors.
228		*/
229	<	private static long nextDefaultSeed() {
230	<	long oldSeed, newSeed;
231	<	do {
232	<	oldSeed = defaultSeedGenerator.get();
233	<	newSeed = addGammaModGeorge(oldSeed, DEFAULT_SEED_GAMMA);
234	<	} while (!defaultSeedGenerator.compareAndSet(oldSeed, newSeed));
235	<	return mix64(newSeed);
229	>	private static final AtomicLong defaultGen = new AtomicLong(initialSeed());
230	>
231	>	private static long initialSeed() {
232	>	String pp = java.security.AccessController.doPrivileged(
233	>	new sun.security.action.GetPropertyAction(
234	>	"java.util.secureRandomSeed"));
235	>	if (pp != null && pp.equalsIgnoreCase("true")) {
236	>	byte[] seedBytes = java.security.SecureRandom.getSeed(8);
237	>	long s = (long)(seedBytes[0]) & 0xffL;
238	>	for (int i = 1; i < 8; ++i)
239	>	s = (s << 8) | ((long)(seedBytes[i]) & 0xffL);
240	>	return s;
241	>	}
242	>	long h = 0L;
243	>	try {
244	>	Enumeration<NetworkInterface> ifcs =
245	>	NetworkInterface.getNetworkInterfaces();
246	>	boolean retry = false; // retry once if getHardwareAddress is null
247	>	while (ifcs.hasMoreElements()) {
248	>	NetworkInterface ifc = ifcs.nextElement();
249	>	if (!ifc.isVirtual()) { // skip fake addresses
250	>	byte[] bs = ifc.getHardwareAddress();
251	>	if (bs != null) {
252	>	int n = bs.length;
253	>	int m = Math.min(n >>> 1, 4);
254	>	for (int i = 0; i < m; ++i)
255	>	h = (h << 16) ^ (bs[i] << 8) ^ bs[n-1-i];
256	>	if (m < 4)
257	>	h = (h << 8) ^ bs[n-1-m];
258	>	h = mix64(h);
259	>	break;
260	>	}
261	>	else if (!retry)
262	>	retry = true;
263	>	else
264	>	break;
265	>	}
266	>	}
267	>	} catch (Exception ignore) {
268	>	}
269	>	return (h ^ mix64(System.currentTimeMillis()) ^
270	>	mix64(System.nanoTime()));
271		}
272
273	+	// IllegalArgumentException messages
274	+	static final String BadBound = "bound must be positive";
275	+	static final String BadRange = "bound must be greater than origin";
276	+	static final String BadSize  = "size must be non-negative";
277	+
278		/*
279		* Internal versions of nextX methods used by streams, as well as
280		* the public nextX(origin, bound) methods.  These exist mainly to
#	Line 364 | Line 350 | public class SplittableRandom {
350		int r = mix32(nextSeed());
351		if (origin < bound) {
352		int n = bound - origin, m = n - 1;
353	<	if ((n & m) == 0L)
353	>	if ((n & m) == 0)
354		r = (r & m) + origin;
355		else if (n > 0) {
356		for (int u = r >>> 1;
#	Line 389 | Line 375 | public class SplittableRandom {
375		* @return a pseudorandom value
376		*/
377		final double internalNextDouble(double origin, double bound) {
378	<	double r = (nextLong() >>> 11) * DOUBLE_UNIT;
378	>	double r = (nextLong() >>> 11) * DOUBLE_ULP;
379		if (origin < bound) {
380		r = r * (bound - origin) + origin;
381		if (r >= bound) // correct for rounding
#	Line 403 | Line 389 | public class SplittableRandom {
389		/**
390		* Creates a new SplittableRandom instance using the specified
391		* initial seed. SplittableRandom instances created with the same
392	<	* seed generate identical sequences of values.
392	>	* seed in the same program generate identical sequences of values.
393		*
394		* @param seed the initial seed
395		*/
396		public SplittableRandom(long seed) {
397	<	this(seed, 0);
397	>	this(seed, GOLDEN_GAMMA);
398		}
399
400		/**
#	Line 417 | Line 403 | public class SplittableRandom {
403		* of those of any other instances in the current program; and
404		* may, and typically does, vary across program invocations.
405		*/
406	<	public SplittableRandom() {
407	<	this(nextDefaultSeed(), GAMMA_GAMMA);
406	>	public SplittableRandom() { // emulate defaultGen.split()
407	>	long s = defaultGen.getAndAdd(2*GOLDEN_GAMMA);
408	>	this.seed = mix64(s);
409	>	this.gamma = mixGamma(s + GOLDEN_GAMMA);
410		}
411
412		/**
#	Line 436 | Line 424 | public class SplittableRandom {
424		* @return the new SplittableRandom instance
425		*/
426		public SplittableRandom split() {
427	<	return new SplittableRandom(nextSeed(), nextSplit);
427	>	return new SplittableRandom(nextLong(), mixGamma(nextSeed()));
428		}
429
430		/**
#	Line 452 | Line 440 | public class SplittableRandom {
440		* Returns a pseudorandom {@code int} value between zero (inclusive)
441		* and the specified bound (exclusive).
442		*
443	<	* @param bound the bound on the random number to be returned.  Must be
456	<	*        positive.
443	>	* @param bound the upper bound (exclusive).  Must be positive.
444		* @return a pseudorandom {@code int} value between zero
445		*         (inclusive) and the bound (exclusive)
446	<	* @throws IllegalArgumentException if the bound is less than zero
446	>	* @throws IllegalArgumentException if {@code bound} is not positive
447		*/
448		public int nextInt(int bound) {
449		if (bound <= 0)
450	<	throw new IllegalArgumentException("bound must be positive");
450	>	throw new IllegalArgumentException(BadBound);
451		// Specialize internalNextInt for origin 0
452		int r = mix32(nextSeed());
453		int m = bound - 1;
454	<	if ((bound & m) == 0L) // power of two
454	>	if ((bound & m) == 0) // power of two
455		r &= m;
456		else { // reject over-represented candidates
457		for (int u = r >>> 1;
#	Line 488 | Line 475 | public class SplittableRandom {
475		*/
476		public int nextInt(int origin, int bound) {
477		if (origin >= bound)
478	<	throw new IllegalArgumentException("bound must be greater than origin");
478	>	throw new IllegalArgumentException(BadRange);
479		return internalNextInt(origin, bound);
480		}
481
#	Line 505 | Line 492 | public class SplittableRandom {
492		* Returns a pseudorandom {@code long} value between zero (inclusive)
493		* and the specified bound (exclusive).
494		*
495	<	* @param bound the bound on the random number to be returned.  Must be
509	<	*        positive.
495	>	* @param bound the upper bound (exclusive).  Must be positive.
496		* @return a pseudorandom {@code long} value between zero
497		*         (inclusive) and the bound (exclusive)
498	<	* @throws IllegalArgumentException if {@code bound} is less than zero
498	>	* @throws IllegalArgumentException if {@code bound} is not positive
499		*/
500		public long nextLong(long bound) {
501		if (bound <= 0)
502	<	throw new IllegalArgumentException("bound must be positive");
502	>	throw new IllegalArgumentException(BadBound);
503		// Specialize internalNextLong for origin 0
504		long r = mix64(nextSeed());
505		long m = bound - 1;
#	Line 541 | Line 527 | public class SplittableRandom {
527		*/
528		public long nextLong(long origin, long bound) {
529		if (origin >= bound)
530	<	throw new IllegalArgumentException("bound must be greater than origin");
530	>	throw new IllegalArgumentException(BadRange);
531		return internalNextLong(origin, bound);
532		}
533
#	Line 550 | Line 536 | public class SplittableRandom {
536		* (inclusive) and one (exclusive).
537		*
538		* @return a pseudorandom {@code double} value between zero
539	<	* (inclusive) and one (exclusive)
539	>	*         (inclusive) and one (exclusive)
540		*/
541		public double nextDouble() {
542	<	return (nextLong() >>> 11) * DOUBLE_UNIT;
542	>	return (mix64(nextSeed()) >>> 11) * DOUBLE_ULP;
543		}
544
545		/**
546		* Returns a pseudorandom {@code double} value between 0.0
547		* (inclusive) and the specified bound (exclusive).
548		*
549	<	* @param bound the bound on the random number to be returned.  Must be
564	<	*        positive.
549	>	* @param bound the upper bound (exclusive).  Must be positive.
550		* @return a pseudorandom {@code double} value between zero
551		*         (inclusive) and the bound (exclusive)
552	<	* @throws IllegalArgumentException if {@code bound} is less than zero
552	>	* @throws IllegalArgumentException if {@code bound} is not positive
553		*/
554		public double nextDouble(double bound) {
555		if (!(bound > 0.0))
556	<	throw new IllegalArgumentException("bound must be positive");
557	<	double result = nextDouble() * bound;
556	>	throw new IllegalArgumentException(BadBound);
557	>	double result = (mix64(nextSeed()) >>> 11) * DOUBLE_ULP * bound;
558		return (result < bound) ?  result : // correct for rounding
559		Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
560		}
#	Line 579 | Line 564 | public class SplittableRandom {
564		* origin (inclusive) and bound (exclusive).
565		*
566		* @param origin the least value returned
567	<	* @param bound the upper bound
567	>	* @param bound the upper bound (exclusive)
568		* @return a pseudorandom {@code double} value between the origin
569		*         (inclusive) and the bound (exclusive)
570		* @throws IllegalArgumentException if {@code origin} is greater than
#	Line 587 | Line 572 | public class SplittableRandom {
572		*/
573		public double nextDouble(double origin, double bound) {
574		if (!(origin < bound))
575	<	throw new IllegalArgumentException("bound must be greater than origin");
575	>	throw new IllegalArgumentException(BadRange);
576		return internalNextDouble(origin, bound);
577		}
578
579	+	/**
580	+	* Returns a pseudorandom {@code boolean} value.
581	+	*
582	+	* @return a pseudorandom {@code boolean} value
583	+	*/
584	+	public boolean nextBoolean() {
585	+	return mix32(nextSeed()) < 0;
586	+	}
587	+
588		// stream methods, coded in a way intended to better isolate for
589		// maintenance purposes the small differences across forms.
590
591		/**
592	<	* Returns a stream producing the given {@code streamSize} number of
593	<	* pseudorandom {@code int} values.
592	>	* Returns a stream producing the given {@code streamSize} number
593	>	* of pseudorandom {@code int} values from this generator and/or
594	>	* one split from it.
595		*
596		* @param streamSize the number of values to generate
597		* @return a stream of pseudorandom {@code int} values
#	Line 605 | Line 600 | public class SplittableRandom {
600		*/
601		public IntStream ints(long streamSize) {
602		if (streamSize < 0L)
603	<	throw new IllegalArgumentException("negative Stream size");
603	>	throw new IllegalArgumentException(BadSize);
604		return StreamSupport.intStream
605		(new RandomIntsSpliterator
606		(this, 0L, streamSize, Integer.MAX_VALUE, 0),
#	Line 614 | Line 609 | public class SplittableRandom {
609
610		/**
611		* Returns an effectively unlimited stream of pseudorandom {@code int}
612	<	* values.
612	>	* values from this generator and/or one split from it.
613		*
614		* @implNote This method is implemented to be equivalent to {@code
615		* ints(Long.MAX_VALUE)}.
#	Line 629 | Line 624 | public class SplittableRandom {
624		}
625
626		/**
627	<	* Returns a stream producing the given {@code streamSize} number of
628	<	* pseudorandom {@code int} values, each conforming to the given
629	<	* origin and bound.
627	>	* Returns a stream producing the given {@code streamSize} number
628	>	* of pseudorandom {@code int} values from this generator and/or one split
629	>	* from it; each value conforms to the given origin (inclusive) and bound
630	>	* (exclusive).
631		*
632		* @param streamSize the number of values to generate
633	<	* @param randomNumberOrigin the origin of each random value
634	<	* @param randomNumberBound the bound of each random value
633	>	* @param randomNumberOrigin the origin (inclusive) of each random value
634	>	* @param randomNumberBound the bound (exclusive) of each random value
635		* @return a stream of pseudorandom {@code int} values,
636	<	*         each with the given origin and bound
636	>	*         each with the given origin (inclusive) and bound (exclusive)
637		* @throws IllegalArgumentException if {@code streamSize} is
638		*         less than zero, or {@code randomNumberOrigin}
639		*         is greater than or equal to {@code randomNumberBound}
#	Line 645 | Line 641 | public class SplittableRandom {
641		public IntStream ints(long streamSize, int randomNumberOrigin,
642		int randomNumberBound) {
643		if (streamSize < 0L)
644	<	throw new IllegalArgumentException("negative Stream size");
644	>	throw new IllegalArgumentException(BadSize);
645		if (randomNumberOrigin >= randomNumberBound)
646	<	throw new IllegalArgumentException("bound must be greater than origin");
646	>	throw new IllegalArgumentException(BadRange);
647		return StreamSupport.intStream
648		(new RandomIntsSpliterator
649		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 656 | Line 652 | public class SplittableRandom {
652
653		/**
654		* Returns an effectively unlimited stream of pseudorandom {@code
655	<	* int} values, each conforming to the given origin and bound.
655	>	* int} values from this generator and/or one split from it; each value
656	>	* conforms to the given origin (inclusive) and bound (exclusive).
657		*
658		* @implNote This method is implemented to be equivalent to {@code
659		* ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
660		*
661	<	* @param randomNumberOrigin the origin of each random value
662	<	* @param randomNumberBound the bound of each random value
661	>	* @param randomNumberOrigin the origin (inclusive) of each random value
662	>	* @param randomNumberBound the bound (exclusive) of each random value
663		* @return a stream of pseudorandom {@code int} values,
664	<	*         each with the given origin and bound
664	>	*         each with the given origin (inclusive) and bound (exclusive)
665		* @throws IllegalArgumentException if {@code randomNumberOrigin}
666		*         is greater than or equal to {@code randomNumberBound}
667		*/
668		public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
669		if (randomNumberOrigin >= randomNumberBound)
670	<	throw new IllegalArgumentException("bound must be greater than origin");
670	>	throw new IllegalArgumentException(BadRange);
671		return StreamSupport.intStream
672		(new RandomIntsSpliterator
673		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 678 | Line 675 | public class SplittableRandom {
675		}
676
677		/**
678	<	* Returns a stream producing the given {@code streamSize} number of
679	<	* pseudorandom {@code long} values.
678	>	* Returns a stream producing the given {@code streamSize} number
679	>	* of pseudorandom {@code long} values from this generator and/or
680	>	* one split from it.
681		*
682		* @param streamSize the number of values to generate
683		* @return a stream of pseudorandom {@code long} values
#	Line 688 | Line 686 | public class SplittableRandom {
686		*/
687		public LongStream longs(long streamSize) {
688		if (streamSize < 0L)
689	<	throw new IllegalArgumentException("negative Stream size");
689	>	throw new IllegalArgumentException(BadSize);
690		return StreamSupport.longStream
691		(new RandomLongsSpliterator
692		(this, 0L, streamSize, Long.MAX_VALUE, 0L),
#	Line 696 | Line 694 | public class SplittableRandom {
694		}
695
696		/**
697	<	* Returns an effectively unlimited stream of pseudorandom {@code long}
698	<	* values.
697	>	* Returns an effectively unlimited stream of pseudorandom {@code
698	>	* long} values from this generator and/or one split from it.
699		*
700		* @implNote This method is implemented to be equivalent to {@code
701		* longs(Long.MAX_VALUE)}.
#	Line 713 | Line 711 | public class SplittableRandom {
711
712		/**
713		* Returns a stream producing the given {@code streamSize} number of
714	<	* pseudorandom {@code long} values, each conforming to the
715	<	* given origin and bound.
714	>	* pseudorandom {@code long} values from this generator and/or one split
715	>	* from it; each value conforms to the given origin (inclusive) and bound
716	>	* (exclusive).
717		*
718		* @param streamSize the number of values to generate
719	<	* @param randomNumberOrigin the origin of each random value
720	<	* @param randomNumberBound the bound of each random value
719	>	* @param randomNumberOrigin the origin (inclusive) of each random value
720	>	* @param randomNumberBound the bound (exclusive) of each random value
721		* @return a stream of pseudorandom {@code long} values,
722	<	*         each with the given origin and bound
722	>	*         each with the given origin (inclusive) and bound (exclusive)
723		* @throws IllegalArgumentException if {@code streamSize} is
724		*         less than zero, or {@code randomNumberOrigin}
725		*         is greater than or equal to {@code randomNumberBound}
#	Line 728 | Line 727 | public class SplittableRandom {
727		public LongStream longs(long streamSize, long randomNumberOrigin,
728		long randomNumberBound) {
729		if (streamSize < 0L)
730	<	throw new IllegalArgumentException("negative Stream size");
730	>	throw new IllegalArgumentException(BadSize);
731		if (randomNumberOrigin >= randomNumberBound)
732	<	throw new IllegalArgumentException("bound must be greater than origin");
732	>	throw new IllegalArgumentException(BadRange);
733		return StreamSupport.longStream
734		(new RandomLongsSpliterator
735		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 739 | Line 738 | public class SplittableRandom {
738
739		/**
740		* Returns an effectively unlimited stream of pseudorandom {@code
741	<	* long} values, each conforming to the given origin and bound.
741	>	* long} values from this generator and/or one split from it; each value
742	>	* conforms to the given origin (inclusive) and bound (exclusive).
743		*
744		* @implNote This method is implemented to be equivalent to {@code
745		* longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
746		*
747	<	* @param randomNumberOrigin the origin of each random value
748	<	* @param randomNumberBound the bound of each random value
747	>	* @param randomNumberOrigin the origin (inclusive) of each random value
748	>	* @param randomNumberBound the bound (exclusive) of each random value
749		* @return a stream of pseudorandom {@code long} values,
750	<	*         each with the given origin and bound
750	>	*         each with the given origin (inclusive) and bound (exclusive)
751		* @throws IllegalArgumentException if {@code randomNumberOrigin}
752		*         is greater than or equal to {@code randomNumberBound}
753		*/
754		public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
755		if (randomNumberOrigin >= randomNumberBound)
756	<	throw new IllegalArgumentException("bound must be greater than origin");
756	>	throw new IllegalArgumentException(BadRange);
757		return StreamSupport.longStream
758		(new RandomLongsSpliterator
759		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 762 | Line 762 | public class SplittableRandom {
762
763		/**
764		* Returns a stream producing the given {@code streamSize} number of
765	<	* pseudorandom {@code double} values, each between zero
766	<	* (inclusive) and one (exclusive).
765	>	* pseudorandom {@code double} values from this generator and/or one split
766	>	* from it; each value is between zero (inclusive) and one (exclusive).
767		*
768		* @param streamSize the number of values to generate
769		* @return a stream of {@code double} values
#	Line 772 | Line 772 | public class SplittableRandom {
772		*/
773		public DoubleStream doubles(long streamSize) {
774		if (streamSize < 0L)
775	<	throw new IllegalArgumentException("negative Stream size");
775	>	throw new IllegalArgumentException(BadSize);
776		return StreamSupport.doubleStream
777		(new RandomDoublesSpliterator
778		(this, 0L, streamSize, Double.MAX_VALUE, 0.0),
#	Line 781 | Line 781 | public class SplittableRandom {
781
782		/**
783		* Returns an effectively unlimited stream of pseudorandom {@code
784	<	* double} values, each between zero (inclusive) and one
785	<	* (exclusive).
784	>	* double} values from this generator and/or one split from it; each value
785	>	* is between zero (inclusive) and one (exclusive).
786		*
787		* @implNote This method is implemented to be equivalent to {@code
788		* doubles(Long.MAX_VALUE)}.
#	Line 798 | Line 798 | public class SplittableRandom {
798
799		/**
800		* Returns a stream producing the given {@code streamSize} number of
801	<	* pseudorandom {@code double} values, each conforming to the
802	<	* given origin and bound.
801	>	* pseudorandom {@code double} values from this generator and/or one split
802	>	* from it; each value conforms to the given origin (inclusive) and bound
803	>	* (exclusive).
804		*
805		* @param streamSize the number of values to generate
806	<	* @param randomNumberOrigin the origin of each random value
807	<	* @param randomNumberBound the bound of each random value
806	>	* @param randomNumberOrigin the origin (inclusive) of each random value
807	>	* @param randomNumberBound the bound (exclusive) of each random value
808		* @return a stream of pseudorandom {@code double} values,
809	<	* each with the given origin and bound
809	>	*         each with the given origin (inclusive) and bound (exclusive)
810		* @throws IllegalArgumentException if {@code streamSize} is
811	<	* less than zero
811	>	*         less than zero
812		* @throws IllegalArgumentException if {@code randomNumberOrigin}
813		*         is greater than or equal to {@code randomNumberBound}
814		*/
815		public DoubleStream doubles(long streamSize, double randomNumberOrigin,
816		double randomNumberBound) {
817		if (streamSize < 0L)
818	<	throw new IllegalArgumentException("negative Stream size");
818	>	throw new IllegalArgumentException(BadSize);
819		if (!(randomNumberOrigin < randomNumberBound))
820	<	throw new IllegalArgumentException("bound must be greater than origin");
820	>	throw new IllegalArgumentException(BadRange);
821		return StreamSupport.doubleStream
822		(new RandomDoublesSpliterator
823		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 825 | Line 826 | public class SplittableRandom {
826
827		/**
828		* Returns an effectively unlimited stream of pseudorandom {@code
829	<	* double} values, each conforming to the given origin and bound.
829	>	* double} values from this generator and/or one split from it; each value
830	>	* conforms to the given origin (inclusive) and bound (exclusive).
831		*
832		* @implNote This method is implemented to be equivalent to {@code
833		* doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
834		*
835	<	* @param randomNumberOrigin the origin of each random value
836	<	* @param randomNumberBound the bound of each random value
835	>	* @param randomNumberOrigin the origin (inclusive) of each random value
836	>	* @param randomNumberBound the bound (exclusive) of each random value
837		* @return a stream of pseudorandom {@code double} values,
838	<	* each with the given origin and bound
838	>	*         each with the given origin (inclusive) and bound (exclusive)
839		* @throws IllegalArgumentException if {@code randomNumberOrigin}
840		*         is greater than or equal to {@code randomNumberBound}
841		*/
842		public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
843		if (!(randomNumberOrigin < randomNumberBound))
844	<	throw new IllegalArgumentException("bound must be greater than origin");
844	>	throw new IllegalArgumentException(BadRange);
845		return StreamSupport.doubleStream
846		(new RandomDoublesSpliterator
847		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 854 | Line 856 | public class SplittableRandom {
856		* approach. The long and double versions of this class are
857		* identical except for types.
858		*/
859	<	static class RandomIntsSpliterator implements Spliterator.OfInt {
859	>	static final class RandomIntsSpliterator implements Spliterator.OfInt {
860		final SplittableRandom rng;
861		long index;
862		final long fence;
#	Line 897 | Line 899 | public class SplittableRandom {
899		long i = index, f = fence;
900		if (i < f) {
901		index = f;
902	+	SplittableRandom r = rng;
903		int o = origin, b = bound;
904		do {
905	<	consumer.accept(rng.internalNextInt(o, b));
905	>	consumer.accept(r.internalNextInt(o, b));
906		} while (++i < f);
907		}
908		}
#	Line 908 | Line 911 | public class SplittableRandom {
911		/**
912		* Spliterator for long streams.
913		*/
914	<	static class RandomLongsSpliterator implements Spliterator.OfLong {
914	>	static final class RandomLongsSpliterator implements Spliterator.OfLong {
915		final SplittableRandom rng;
916		long index;
917		final long fence;
#	Line 951 | Line 954 | public class SplittableRandom {
954		long i = index, f = fence;
955		if (i < f) {
956		index = f;
957	+	SplittableRandom r = rng;
958		long o = origin, b = bound;
959		do {
960	<	consumer.accept(rng.internalNextLong(o, b));
960	>	consumer.accept(r.internalNextLong(o, b));
961		} while (++i < f);
962		}
963		}
#	Line 963 | Line 967 | public class SplittableRandom {
967		/**
968		* Spliterator for double streams.
969		*/
970	<	static class RandomDoublesSpliterator implements Spliterator.OfDouble {
970	>	static final class RandomDoublesSpliterator implements Spliterator.OfDouble {
971		final SplittableRandom rng;
972		long index;
973		final long fence;
#	Line 1006 | Line 1010 | public class SplittableRandom {
1010		long i = index, f = fence;
1011		if (i < f) {
1012		index = f;
1013	+	SplittableRandom r = rng;
1014		double o = origin, b = bound;
1015		do {
1016	<	consumer.accept(rng.internalNextDouble(o, b));
1016	>	consumer.accept(r.internalNextDouble(o, b));
1017		} while (++i < f);
1018		}
1019		}

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