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Comparing jsr166/src/main/java/util/SplittableRandom.java (file contents):
Revision 1.4 by dl, Thu Jul 11 13:40:42 2013 UTC vs.
Revision 1.23 by dl, Fri Sep 20 14:06:46 2013 UTC

#	Line 25 | Line 25
25
26		package java.util;
27
28	+	import java.net.NetworkInterface;
29		import java.util.concurrent.atomic.AtomicLong;
29	–	import java.util.Spliterator;
30		import java.util.function.IntConsumer;
31		import java.util.function.LongConsumer;
32		import java.util.function.DoubleConsumer;
#	Line 35 | Line 35 | import java.util.stream.IntStream;
35		import java.util.stream.LongStream;
36		import java.util.stream.DoubleStream;
37
38	–
38		/**
39		* A generator of uniform pseudorandom values applicable for use in
40		* (among other contexts) isolated parallel computations that may
41	<	* generate subtasks. Class SplittableRandom supports methods for
41	>	* generate subtasks. Class {@code SplittableRandom} supports methods for
42		* producing pseudorandom numbers of type {@code int}, {@code long},
43		* and {@code double} with similar usages as for class
44	<	* {@link java.util.Random} but differs in the following ways: <ul>
44	>	* {@link java.util.Random} but differs in the following ways:
45	>	*
46	>	* <ul>
47		*
48		* <li>Series of generated values pass the DieHarder suite testing
49		* independence and uniformity properties of random number generators.
#	Line 50 | Line 51 | import java.util.stream.DoubleStream;
51		* href="http://www.phy.duke.edu/~rgb/General/dieharder.php"> version
52		* 3.31.1</a>.) These tests validate only the methods for certain
53		* types and ranges, but similar properties are expected to hold, at
54	<	* least approximately, for others as well.  </li>
54	>	* least approximately, for others as well. The <em>period</em>
55	>	* (length of any series of generated values before it repeats) is at
56	>	* least 2<sup>64</sup>. </li>
57		*
58		* <li> Method {@link #split} constructs and returns a new
59		* SplittableRandom instance that shares no mutable state with the
60	<	* current instance. However, with very high probability, the set of
61	<	* values collectively generated by the two objects has the same
60	>	* current instance. However, with very high probability, the
61	>	* values collectively generated by the two objects have the same
62		* statistical properties as if the same quantity of values were
63		* generated by a single thread using a single {@code
64		* SplittableRandom} object.  </li>
#	Line 73 | Line 76 | import java.util.stream.DoubleStream;
76		*
77		* </ul>
78		*
79	+	* <p>Instances of {@code SplittableRandom} are not cryptographically
80	+	* secure.  Consider instead using {@link java.security.SecureRandom}
81	+	* in security-sensitive applications. Additionally,
82	+	* default-constructed instances do not use a cryptographically random
83	+	* seed unless the {@linkplain System#getProperty system property}
84	+	* {@code java.util.secureRandomSeed} is set to {@code true}.
85	+	*
86		* @author  Guy Steele
87		* @author  Doug Lea
88		* @since   1.8
89		*/
90	<	public class SplittableRandom {
81	<
82	<	/*
83	<	* File organization: First the non-public methods that constitute
84	<	* the main algorithm, then the main public methods, followed by
85	<	* some custom spliterator classes needed for stream methods.
86	<	*
87	<	* Credits: Primary algorithm and code by Guy Steele.  Stream
88	<	* support methods by Doug Lea.  Documentation jointly produced
89	<	* with additional help from Brian Goetz.
90	<	*/
90	>	public final class SplittableRandom {
91
92		/*
93		* Implementation Overview.
#	Line 95 | Line 95 | public class SplittableRandom {
95		* This algorithm was inspired by the "DotMix" algorithm by
96		* Leiserson, Schardl, and Sukha "Deterministic Parallel
97		* Random-Number Generation for Dynamic-Multithreading Platforms",
98	<	* PPoPP 2012, but improves and extends it in several ways.
98	>	* PPoPP 2012, as well as those in "Parallel random numbers: as
99	>	* easy as 1, 2, 3" by Salmon, Morae, Dror, and Shaw, SC 2011.  It
100	>	* differs mainly in simplifying and cheapening operations.
101	>	*
102	>	* The primary update step (method nextSeed()) is to add a
103	>	* constant ("gamma") to the current (64 bit) seed, forming a
104	>	* simple sequence.  The seed and the gamma values for any two
105	>	* SplittableRandom instances are highly likely to be different.
106	>	*
107	>	* Methods nextLong, nextInt, and derivatives do not return the
108	>	* sequence (seed) values, but instead a hash-like bit-mix of
109	>	* their bits, producing more independently distributed sequences.
110	>	* For nextLong, the mix64 function is based on David Stafford's
111	>	* (http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html)
112	>	* "Mix13" variant of the "64-bit finalizer" function in Austin
113	>	* Appleby's MurmurHash3 algorithm See
114	>	* http://code.google.com/p/smhasher/wiki/MurmurHash3 . The mix32
115	>	* function is based on Stafford's Mix04 mix function, but returns
116	>	* the upper 32 bits cast as int.
117	>	*
118	>	* The split operation uses the current generator to form the seed
119	>	* and gamma for another SplittableRandom.  To conservatively
120	>	* avoid potential correlations between seed and value generation,
121	>	* gamma selection (method mixGamma) uses different
122	>	* (Murmurhash3's) mix constants.  To avoid potential weaknesses
123	>	* in bit-mixing transformations, we restrict gammas to odd values
124	>	* with at least 24 0-1 or 1-0 bit transitions.  Rather than
125	>	* rejecting candidates with too few or too many bits set, method
126	>	* mixGamma flips some bits (which has the effect of mapping at
127	>	* most 4 to any given gamma value).  This reduces the effective
128	>	* set of 64bit odd gamma values by about 2%, and serves as an
129	>	* automated screening for sequence constant selection that is
130	>	* left as an empirical decision in some other hashing and crypto
131	>	* algorithms.
132	>	*
133	>	* The resulting generator thus transforms a sequence in which
134	>	* (typically) many bits change on each step, with an inexpensive
135	>	* mixer with good (but less than cryptographically secure)
136	>	* avalanching.
137	>	*
138	>	* The default (no-argument) constructor, in essence, invokes
139	>	* split() for a common "defaultGen" SplittableRandom.  Unlike
140	>	* other cases, this split must be performed in a thread-safe
141	>	* manner, so we use an AtomicLong to represent the seed rather
142	>	* than use an explicit SplittableRandom. To bootstrap the
143	>	* defaultGen, we start off using a seed based on current time and
144	>	* network interface address unless the java.util.secureRandomSeed
145	>	* property is set. This serves as a slimmed-down (and insecure)
146	>	* variant of SecureRandom that also avoids stalls that may occur
147	>	* when using /dev/random.
148	>	*
149	>	* It is a relatively simple matter to apply the basic design here
150	>	* to use 128 bit seeds. However, emulating 128bit arithmetic and
151	>	* carrying around twice the state add more overhead than appears
152	>	* warranted for current usages.
153		*
154	<	* The primary update step is simply to add a constant ("gamma")
155	<	* to the current seed, modulo a prime ("George"). However, the
156	<	* nextLong and nextInt methods do not return this value, but
157	<	* instead the results of bit-mixing transformations that produce
104	<	* more uniformly distributed sequences.
105	<	*
106	<	* "George" is the otherwise nameless (because it cannot be
107	<	* represented) prime number 2^64+13. Using a prime number larger
108	<	* than can fit in a long ensures that all possible long values
109	<	* can occur, plus 13 others that just get skipped over when they
110	<	* are encountered; see method addGammaModGeorge. For this to
111	<	* work, initial gamma values must be at least 13.
112	<	*
113	<	* The value of gamma differs for each instance across a series of
114	<	* splits, and is generated using a slightly stripped-down variant
115	<	* of the same algorithm, but operating across calls to split(),
116	<	* not calls to nextSeed(): Each instance carries the state of
117	<	* this generator as nextSplit, and uses mix64(nextSplit) as its
118	<	* own gamma value. Computations of gammas themselves use a fixed
119	<	* constant as the second argument to the addGammaModGeorge
120	<	* function, GAMMA_GAMMA, a "genuinely random" number from a
121	<	* radioactive decay reading (obtained from
122	<	* http://www.fourmilab.ch/hotbits/) meeting the above range
123	<	* constraint. Using a fixed constant maintains the invariant that
124	<	* the value of gamma is the same for every instance that is at
125	<	* the same split-distance from their common root. (Note: there is
126	<	* nothing especially magic about obtaining this constant from a
127	<	* "truly random" physical source rather than just choosing one
128	<	* arbitrarily; using "hotbits" was merely an aesthetically pleasing
129	<	* choice.  In either case, good statistical behavior of the
130	<	* algorithm should be, and was, verified by using the DieHarder
131	<	* test suite.)
132	<	*
133	<	* The mix64 bit-mixing function called by nextLong and other
134	<	* methods computes the same value as the "64-bit finalizer"
135	<	* function in Austin Appleby's MurmurHash3 algorithm.  See
136	<	* http://code.google.com/p/smhasher/wiki/MurmurHash3 , which
137	<	* comments: "The constants for the finalizers were generated by a
138	<	* simple simulated-annealing algorithm, and both avalanche all
139	<	* bits of 'h' to within 0.25% bias." It also appears to work to
140	<	* use instead any of the variants proposed by David Stafford at
141	<	* http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html
142	<	* but these variants have not yet been tested as thoroughly
143	<	* in the context of the implementation of SplittableRandom.
144	<	*
145	<	* The mix32 function used for nextInt just consists of two of the
146	<	* five lines of mix64; avalanche testing shows that the 64-bit result
147	<	* has its top 32 bits avalanched well, though not the bottom 32 bits.
148	<	* DieHarder tests show that it is adequate for generating one
149	<	* random int from the 64-bit result of nextSeed.
150	<	*
151	<	* Support for the default (no-argument) constructor relies on an
152	<	* AtomicLong (defaultSeedGenerator) to help perform the
153	<	* equivalent of a split of a statically constructed
154	<	* SplittableRandom. Unlike other cases, this split must be
155	<	* performed in a thread-safe manner. We use
156	<	* AtomicLong.compareAndSet as the (typically) most efficient
157	<	* mechanism. To bootstrap, we start off using System.nanotime(),
158	<	* and update using another "genuinely random" constant
159	<	* DEFAULT_SEED_GAMMA. The default constructor uses GAMMA_GAMMA,
160	<	* not 0, for its splitSeed argument (addGammaModGeorge(0,
161	<	* GAMMA_GAMMA) == GAMMA_GAMMA) to reflect that each is split from
162	<	* this root generator, even though the root is not explicitly
163	<	* represented as a SplittableRandom.
164	<	*/
165	<
166	<	/**
167	<	* The "genuinely random" value for producing new gamma values.
168	<	* The value is arbitrary, subject to the requirement that it be
169	<	* greater or equal to 13.
170	<	*/
171	<	private static final long GAMMA_GAMMA = 0xF2281E2DBA6606F3L;
172	<
173	<	/**
174	<	* The "genuinely random" seed update value for default constructors.
175	<	* The value is arbitrary, subject to the requirement that it be
176	<	* greater or equal to 13.
177	<	*/
178	<	private static final long DEFAULT_SEED_GAMMA = 0xBD24B73A95FB84D9L;
154	>	* File organization: First the non-public methods that constitute
155	>	* the main algorithm, then the main public methods, followed by
156	>	* some custom spliterator classes needed for stream methods.
157	>	*/
158
159		/**
160	<	* The next seed for default constructors.
160	>	* The golden ratio scaled to 64bits, used as the initial gamma
161	>	* value for (unsplit) SplittableRandoms.
162		*/
163	<	private static final AtomicLong defaultSeedGenerator =
184	<	new AtomicLong(System.nanoTime());
163	>	private static final long GOLDEN_GAMMA = 0x9e3779b97f4a7c15L;
164
165		/**
166	<	* The seed, updated only via method nextSeed.
166	>	* The least non-zero value returned by nextDouble(). This value
167	>	* is scaled by a random value of 53 bits to produce a result.
168		*/
169	<	private long seed;
169	>	private static final double DOUBLE_ULP = 1.0 / (1L << 53);
170
171		/**
172	<	* The constant value added to seed (mod George) on each update.
172	>	* The seed. Updated only via method nextSeed.
173		*/
174	<	private final long gamma;
174	>	private long seed;
175
176		/**
177	<	* The next seed to use for splits. Propagated using
198	<	* addGammaModGeorge across instances.
177	>	* The step value.
178		*/
179	<	private final long nextSplit;
179	>	private final long gamma;
180
181		/**
182	<	* Internal constructor used by all other constructors and by
204	<	* method split. Establishes the initial seed for this instance,
205	<	* and uses the given splitSeed to establish gamma, as well as the
206	<	* nextSplit to use by this instance.
182	>	* Internal constructor used by all others except default constructor.
183		*/
184	<	private SplittableRandom(long seed, long splitSeed) {
184	>	private SplittableRandom(long seed, long gamma) {
185		this.seed = seed;
186	<	long s = splitSeed, g;
211	<	do { // ensure gamma >= 13, considered as an unsigned integer
212	<	s = addGammaModGeorge(s, GAMMA_GAMMA);
213	<	g = mix64(s);
214	<	} while (Long.compareUnsigned(g, 13L) < 0);
215	<	this.gamma = g;
216	<	this.nextSplit = s;
186	>	this.gamma = gamma;
187		}
188
189		/**
190	<	* Adds the given gamma value, g, to the given seed value s, mod
191	<	* George (2^64+13). We regard s and g as unsigned values
192	<	* (ranging from 0 to 2^64-1). We add g to s either once or twice
193	<	* (mod George) as necessary to produce an (unsigned) result less
194	<	* than 2^64.  We require that g must be at least 13. This
195	<	* guarantees that if (s+g) mod George >= 2^64 then (s+g+g) mod
226	<	* George < 2^64; thus we need only a conditional, not a loop,
227	<	* to be sure of getting a representable value.
228	<	*
229	<	* @param s a seed value
230	<	* @param g a gamma value, 13 <= g (as unsigned)
231	<	*/
232	<	private static long addGammaModGeorge(long s, long g) {
233	<	long p = s + g;
234	<	if (Long.compareUnsigned(p, g) >= 0)
235	<	return p;
236	<	long q = p - 13L;
237	<	return (Long.compareUnsigned(p, 13L) >= 0) ? q : (q + g);
190	>	* Computes Stafford variant 13 of 64bit mix function.
191	>	*/
192	>	private static long mix64(long z) {
193	>	z *= 0xbf58476d1ce4e5b9L;
194	>	z = (z ^ (z >>> 32)) * 0x94d049bb133111ebL;
195	>	return z ^ (z >>> 32);
196		}
197
198		/**
199	<	* Updates in-place and returns seed.
242	<	* See above for explanation.
199	>	* Returns the 32 high bits of Stafford variant 4 mix64 function as int.
200		*/
201	<	private long nextSeed() {
202	<	return seed = addGammaModGeorge(seed, gamma);
201	>	private static int mix32(long z) {
202	>	z *= 0x62a9d9ed799705f5L;
203	>	return (int)(((z ^ (z >>> 28)) * 0xcb24d0a5c88c35b3L) >>> 32);
204		}
205
206		/**
207	<	* Returns a bit-mixed transformation of its argument.
250	<	* See above for explanation.
207	>	* Returns the gamma value to use for a new split instance.
208		*/
209	<	private static long mix64(long z) {
210	<	z ^= (z >>> 33);
211	<	z *= 0xff51afd7ed558ccdL;
212	<	z ^= (z >>> 33);
213	<	z *= 0xc4ceb9fe1a85ec53L;
214	<	z ^= (z >>> 33);
258	<	return z;
209	>	private static long mixGamma(long z) {
210	>	z *= 0xff51afd7ed558ccdL;                   // MurmurHash3 mix constants
211	>	z = (z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L;
212	>	z = (z ^ (z >>> 33)) | 1L;                  // force to be odd
213	>	int n = Long.bitCount(z ^ (z >>> 1));       // ensure enough transitions
214	>	return (n < 24) ? z ^ 0xaaaaaaaaaaaaaaaaL : z;
215		}
216
217		/**
218	<	* Returns a bit-mixed int transformation of its argument.
263	<	* See above for explanation.
218	>	* Adds gamma to seed.
219		*/
220	<	private static int mix32(long z) {
221	<	z ^= (z >>> 33);
267	<	z *= 0xc4ceb9fe1a85ec53L;
268	<	return (int)(z >>> 32);
220	>	private long nextSeed() {
221	>	return seed += gamma;
222		}
223
224		/**
225	<	* Atomically updates and returns next seed for default constructor
225	>	* The seed generator for default constructors.
226		*/
227	<	private static long nextDefaultSeed() {
228	<	long oldSeed, newSeed;
229	<	do {
230	<	oldSeed = defaultSeedGenerator.get();
231	<	newSeed = addGammaModGeorge(oldSeed, DEFAULT_SEED_GAMMA);
232	<	} while (!defaultSeedGenerator.compareAndSet(oldSeed, newSeed));
233	<	return mix64(newSeed);
227	>	private static final AtomicLong defaultGen = new AtomicLong(initialSeed());
228	>
229	>	private static long initialSeed() {
230	>	String pp = java.security.AccessController.doPrivileged(
231	>	new sun.security.action.GetPropertyAction(
232	>	"java.util.secureRandomSeed"));
233	>	if (pp != null && pp.equalsIgnoreCase("true")) {
234	>	byte[] seedBytes = java.security.SecureRandom.getSeed(8);
235	>	long s = (long)(seedBytes[0]) & 0xffL;
236	>	for (int i = 1; i < 8; ++i)
237	>	s = (s << 8) | ((long)(seedBytes[i]) & 0xffL);
238	>	return s;
239	>	}
240	>	long h = 0L;
241	>	try {
242	>	Enumeration<NetworkInterface> ifcs =
243	>	NetworkInterface.getNetworkInterfaces();
244	>	boolean retry = false; // retry once if getHardwareAddress is null
245	>	while (ifcs.hasMoreElements()) {
246	>	NetworkInterface ifc = ifcs.nextElement();
247	>	if (!ifc.isVirtual()) { // skip fake addresses
248	>	byte[] bs = ifc.getHardwareAddress();
249	>	if (bs != null) {
250	>	int n = bs.length;
251	>	int m = Math.min(n >>> 1, 4);
252	>	for (int i = 0; i < m; ++i)
253	>	h = (h << 16) ^ (bs[i] << 8) ^ bs[n-1-i];
254	>	if (m < 4)
255	>	h = (h << 8) ^ bs[n-1-m];
256	>	h = mix64(h);
257	>	break;
258	>	}
259	>	else if (!retry)
260	>	retry = true;
261	>	else
262	>	break;
263	>	}
264	>	}
265	>	} catch (Exception ignore) {
266	>	}
267	>	return (h ^ mix64(System.currentTimeMillis()) ^
268	>	mix64(System.nanoTime()));
269		}
270
271	+	// IllegalArgumentException messages
272	+	static final String BadBound = "bound must be positive";
273	+	static final String BadRange = "bound must be greater than origin";
274	+	static final String BadSize  = "size must be non-negative";
275	+
276		/*
277		* Internal versions of nextX methods used by streams, as well as
278		* the public nextX(origin, bound) methods.  These exist mainly to
#	Line 326 | Line 319 | public class SplittableRandom {
319		long r = mix64(nextSeed());
320		if (origin < bound) {
321		long n = bound - origin, m = n - 1;
322	<	if ((n & m) == 0L) // power of two
322	>	if ((n & m) == 0L)  // power of two
323		r = (r & m) + origin;
324	<	else if (n > 0) { // reject over-represented candidates
324	>	else if (n > 0L) {  // reject over-represented candidates
325		for (long u = r >>> 1;            // ensure nonnegative
326	<	u + m - (r = u % n) < 0L;    // reject
326	>	u + m - (r = u % n) < 0L;    // rejection check
327		u = mix64(nextSeed()) >>> 1) // retry
328		;
329		r += origin;
330		}
331	<	else {             // range not representable as long
331	>	else {              // range not representable as long
332		while (r < origin || r >= bound)
333		r = mix64(nextSeed());
334		}
#	Line 355 | Line 348 | public class SplittableRandom {
348		int r = mix32(nextSeed());
349		if (origin < bound) {
350		int n = bound - origin, m = n - 1;
351	<	if ((n & m) == 0L)
351	>	if ((n & m) == 0)
352		r = (r & m) + origin;
353		else if (n > 0) {
354		for (int u = r >>> 1;
355	<	u + m - (r = u % n) < 0L;
355	>	u + m - (r = u % n) < 0;
356		u = mix32(nextSeed()) >>> 1)
357		;
358		r += origin;
#	Line 380 | Line 373 | public class SplittableRandom {
373		* @return a pseudorandom value
374		*/
375		final double internalNextDouble(double origin, double bound) {
376	<	long bits = (1023L << 52) | (nextLong() >>> 12);
384	<	double r = Double.longBitsToDouble(bits) - 1.0;
376	>	double r = (nextLong() >>> 11) * DOUBLE_ULP;
377		if (origin < bound) {
378		r = r * (bound - origin) + origin;
379	<	if (r == bound) // correct for rounding
379	>	if (r >= bound) // correct for rounding
380		r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
381		}
382		return r;
#	Line 393 | Line 385 | public class SplittableRandom {
385		/* ---------------- public methods ---------------- */
386
387		/**
388	<	* Creates a new SplittableRandom instance using the given initial
389	<	* seed. Two SplittableRandom instances created with the same seed
390	<	* generate identical sequences of values.
388	>	* Creates a new SplittableRandom instance using the specified
389	>	* initial seed. SplittableRandom instances created with the same
390	>	* seed in the same program generate identical sequences of values.
391		*
392		* @param seed the initial seed
393		*/
394		public SplittableRandom(long seed) {
395	<	this(seed, 0);
395	>	this(seed, GOLDEN_GAMMA);
396		}
397
398		/**
#	Line 409 | Line 401 | public class SplittableRandom {
401		* of those of any other instances in the current program; and
402		* may, and typically does, vary across program invocations.
403		*/
404	<	public SplittableRandom() {
405	<	this(nextDefaultSeed(), GAMMA_GAMMA);
404	>	public SplittableRandom() { // emulate defaultGen.split()
405	>	long s = defaultGen.getAndAdd(2 * GOLDEN_GAMMA);
406	>	this.seed = mix64(s);
407	>	this.gamma = mixGamma(s + GOLDEN_GAMMA);
408		}
409
410		/**
#	Line 428 | Line 422 | public class SplittableRandom {
422		* @return the new SplittableRandom instance
423		*/
424		public SplittableRandom split() {
425	<	return new SplittableRandom(nextSeed(), nextSplit);
425	>	return new SplittableRandom(nextLong(), mixGamma(nextSeed()));
426		}
427
428		/**
429		* Returns a pseudorandom {@code int} value.
430		*
431	<	* @return a pseudorandom value
431	>	* @return a pseudorandom {@code int} value
432		*/
433		public int nextInt() {
434		return mix32(nextSeed());
435		}
436
437		/**
438	<	* Returns a pseudorandom {@code int} value between 0 (inclusive)
438	>	* Returns a pseudorandom {@code int} value between zero (inclusive)
439		* and the specified bound (exclusive).
440		*
441	<	* @param bound the bound on the random number to be returned.  Must be
442	<	*        positive.
443	<	* @return a pseudorandom {@code int} value between {@code 0}
444	<	*         (inclusive) and the bound (exclusive).
451	<	* @exception IllegalArgumentException if the bound is not positive
441	>	* @param bound the upper bound (exclusive).  Must be positive.
442	>	* @return a pseudorandom {@code int} value between zero
443	>	*         (inclusive) and the bound (exclusive)
444	>	* @throws IllegalArgumentException if {@code bound} is not positive
445		*/
446		public int nextInt(int bound) {
447		if (bound <= 0)
448	<	throw new IllegalArgumentException("bound must be positive");
448	>	throw new IllegalArgumentException(BadBound);
449		// Specialize internalNextInt for origin 0
450		int r = mix32(nextSeed());
451		int m = bound - 1;
452	<	if ((bound & m) == 0L) // power of two
452	>	if ((bound & m) == 0) // power of two
453		r &= m;
454		else { // reject over-represented candidates
455		for (int u = r >>> 1;
456	<	u + m - (r = u % bound) < 0L;
456	>	u + m - (r = u % bound) < 0;
457		u = mix32(nextSeed()) >>> 1)
458		;
459		}
#	Line 474 | Line 467 | public class SplittableRandom {
467		* @param origin the least value returned
468		* @param bound the upper bound (exclusive)
469		* @return a pseudorandom {@code int} value between the origin
470	<	*         (inclusive) and the bound (exclusive).
471	<	* @exception IllegalArgumentException if {@code origin} is greater than
470	>	*         (inclusive) and the bound (exclusive)
471	>	* @throws IllegalArgumentException if {@code origin} is greater than
472		*         or equal to {@code bound}
473		*/
474		public int nextInt(int origin, int bound) {
475		if (origin >= bound)
476	<	throw new IllegalArgumentException("bound must be greater than origin");
476	>	throw new IllegalArgumentException(BadRange);
477		return internalNextInt(origin, bound);
478		}
479
480		/**
481		* Returns a pseudorandom {@code long} value.
482		*
483	<	* @return a pseudorandom value
483	>	* @return a pseudorandom {@code long} value
484		*/
485		public long nextLong() {
486		return mix64(nextSeed());
487		}
488
489		/**
490	<	* Returns a pseudorandom {@code long} value between 0 (inclusive)
490	>	* Returns a pseudorandom {@code long} value between zero (inclusive)
491		* and the specified bound (exclusive).
492		*
493	<	* @param bound the bound on the random number to be returned.  Must be
494	<	*        positive.
495	<	* @return a pseudorandom {@code long} value between {@code 0}
496	<	*         (inclusive) and the bound (exclusive).
504	<	* @exception IllegalArgumentException if the bound is not positive
493	>	* @param bound the upper bound (exclusive).  Must be positive.
494	>	* @return a pseudorandom {@code long} value between zero
495	>	*         (inclusive) and the bound (exclusive)
496	>	* @throws IllegalArgumentException if {@code bound} is not positive
497		*/
498		public long nextLong(long bound) {
499		if (bound <= 0)
500	<	throw new IllegalArgumentException("bound must be positive");
500	>	throw new IllegalArgumentException(BadBound);
501		// Specialize internalNextLong for origin 0
502		long r = mix64(nextSeed());
503		long m = bound - 1;
#	Line 527 | Line 519 | public class SplittableRandom {
519		* @param origin the least value returned
520		* @param bound the upper bound (exclusive)
521		* @return a pseudorandom {@code long} value between the origin
522	<	*         (inclusive) and the bound (exclusive).
523	<	* @exception IllegalArgumentException if {@code origin} is greater than
522	>	*         (inclusive) and the bound (exclusive)
523	>	* @throws IllegalArgumentException if {@code origin} is greater than
524		*         or equal to {@code bound}
525		*/
526		public long nextLong(long origin, long bound) {
527		if (origin >= bound)
528	<	throw new IllegalArgumentException("bound must be greater than origin");
528	>	throw new IllegalArgumentException(BadRange);
529		return internalNextLong(origin, bound);
530		}
531
532		/**
533	<	* Returns a pseudorandom {@code double} value between {@code 0.0}
534	<	* (inclusive) and {@code 1.0} (exclusive).
533	>	* Returns a pseudorandom {@code double} value between zero
534	>	* (inclusive) and one (exclusive).
535		*
536	<	* @return a pseudorandom value between {@code 0.0}
537	<	* (inclusive) and {@code 1.0} (exclusive)
536	>	* @return a pseudorandom {@code double} value between zero
537	>	*         (inclusive) and one (exclusive)
538		*/
539		public double nextDouble() {
540	<	long bits = (1023L << 52) | (nextLong() >>> 12);
549	<	return Double.longBitsToDouble(bits) - 1.0;
540	>	return (mix64(nextSeed()) >>> 11) * DOUBLE_ULP;
541		}
542
543		/**
544		* Returns a pseudorandom {@code double} value between 0.0
545		* (inclusive) and the specified bound (exclusive).
546		*
547	<	* @param bound the bound on the random number to be returned.  Must be
548	<	*        positive.
549	<	* @return a pseudorandom {@code double} value between {@code 0.0}
559	<	*         (inclusive) and the bound (exclusive).
547	>	* @param bound the upper bound (exclusive).  Must be positive.
548	>	* @return a pseudorandom {@code double} value between zero
549	>	*         (inclusive) and the bound (exclusive)
550		* @throws IllegalArgumentException if {@code bound} is not positive
551		*/
552		public double nextDouble(double bound) {
553	<	if (bound <= 0.0)
554	<	throw new IllegalArgumentException("bound must be positive");
555	<	double result = nextDouble() * bound;
553	>	if (!(bound > 0.0))
554	>	throw new IllegalArgumentException(BadBound);
555	>	double result = (mix64(nextSeed()) >>> 11) * DOUBLE_ULP * bound;
556		return (result < bound) ?  result : // correct for rounding
557		Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
558		}
559
560		/**
561	<	* Returns a pseudorandom {@code double} value between the given
561	>	* Returns a pseudorandom {@code double} value between the specified
562		* origin (inclusive) and bound (exclusive).
563		*
564		* @param origin the least value returned
565	<	* @param bound the upper bound
565	>	* @param bound the upper bound (exclusive)
566		* @return a pseudorandom {@code double} value between the origin
567	<	*         (inclusive) and the bound (exclusive).
567	>	*         (inclusive) and the bound (exclusive)
568		* @throws IllegalArgumentException if {@code origin} is greater than
569		*         or equal to {@code bound}
570		*/
571		public double nextDouble(double origin, double bound) {
572	<	if (origin >= bound)
573	<	throw new IllegalArgumentException("bound must be greater than origin");
572	>	if (!(origin < bound))
573	>	throw new IllegalArgumentException(BadRange);
574		return internalNextDouble(origin, bound);
575		}
576
577	+	/**
578	+	* Returns a pseudorandom {@code boolean} value.
579	+	*
580	+	* @return a pseudorandom {@code boolean} value
581	+	*/
582	+	public boolean nextBoolean() {
583	+	return mix32(nextSeed()) < 0;
584	+	}
585	+
586		// stream methods, coded in a way intended to better isolate for
587		// maintenance purposes the small differences across forms.
588
589		/**
590	<	* Returns a stream with the given {@code streamSize} number of
591	<	* pseudorandom {@code int} values.
590	>	* Returns a stream producing the given {@code streamSize} number
591	>	* of pseudorandom {@code int} values from this generator and/or
592	>	* one split from it.
593		*
594		* @param streamSize the number of values to generate
595		* @return a stream of pseudorandom {@code int} values
596		* @throws IllegalArgumentException if {@code streamSize} is
597	<	* less than zero
597	>	*         less than zero
598		*/
599		public IntStream ints(long streamSize) {
600		if (streamSize < 0L)
601	<	throw new IllegalArgumentException("negative Stream size");
601	>	throw new IllegalArgumentException(BadSize);
602		return StreamSupport.intStream
603		(new RandomIntsSpliterator
604		(this, 0L, streamSize, Integer.MAX_VALUE, 0),
#	Line 607 | Line 607 | public class SplittableRandom {
607
608		/**
609		* Returns an effectively unlimited stream of pseudorandom {@code int}
610	<	* values
610	>	* values from this generator and/or one split from it.
611		*
612		* @implNote This method is implemented to be equivalent to {@code
613		* ints(Long.MAX_VALUE)}.
#	Line 622 | Line 622 | public class SplittableRandom {
622		}
623
624		/**
625	<	* Returns a stream with the given {@code streamSize} number of
626	<	* pseudorandom {@code int} values, each conforming to the given
627	<	* origin and bound.
625	>	* Returns a stream producing the given {@code streamSize} number
626	>	* of pseudorandom {@code int} values from this generator and/or one split
627	>	* from it; each value conforms to the given origin (inclusive) and bound
628	>	* (exclusive).
629		*
630		* @param streamSize the number of values to generate
631	<	* @param randomNumberOrigin the origin of each random value
632	<	* @param randomNumberBound the bound of each random value
631	>	* @param randomNumberOrigin the origin (inclusive) of each random value
632	>	* @param randomNumberBound the bound (exclusive) of each random value
633		* @return a stream of pseudorandom {@code int} values,
634	<	* each with the given origin and bound.
634	>	*         each with the given origin (inclusive) and bound (exclusive)
635		* @throws IllegalArgumentException if {@code streamSize} is
636	<	* less than zero.
636	<	* @throws IllegalArgumentException if {@code randomNumberOrigin}
636	>	*         less than zero, or {@code randomNumberOrigin}
637		*         is greater than or equal to {@code randomNumberBound}
638		*/
639		public IntStream ints(long streamSize, int randomNumberOrigin,
640		int randomNumberBound) {
641		if (streamSize < 0L)
642	<	throw new IllegalArgumentException("negative Stream size");
642	>	throw new IllegalArgumentException(BadSize);
643		if (randomNumberOrigin >= randomNumberBound)
644	<	throw new IllegalArgumentException("bound must be greater than origin");
644	>	throw new IllegalArgumentException(BadRange);
645		return StreamSupport.intStream
646		(new RandomIntsSpliterator
647		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 650 | Line 650 | public class SplittableRandom {
650
651		/**
652		* Returns an effectively unlimited stream of pseudorandom {@code
653	<	* int} values, each conforming to the given origin and bound.
653	>	* int} values from this generator and/or one split from it; each value
654	>	* conforms to the given origin (inclusive) and bound (exclusive).
655		*
656		* @implNote This method is implemented to be equivalent to {@code
657		* ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
658		*
659	<	* @param randomNumberOrigin the origin of each random value
660	<	* @param randomNumberBound the bound of each random value
659	>	* @param randomNumberOrigin the origin (inclusive) of each random value
660	>	* @param randomNumberBound the bound (exclusive) of each random value
661		* @return a stream of pseudorandom {@code int} values,
662	<	* each with the given origin and bound.
662	>	*         each with the given origin (inclusive) and bound (exclusive)
663		* @throws IllegalArgumentException if {@code randomNumberOrigin}
664		*         is greater than or equal to {@code randomNumberBound}
665		*/
666		public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
667		if (randomNumberOrigin >= randomNumberBound)
668	<	throw new IllegalArgumentException("bound must be greater than origin");
668	>	throw new IllegalArgumentException(BadRange);
669		return StreamSupport.intStream
670		(new RandomIntsSpliterator
671		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 672 | Line 673 | public class SplittableRandom {
673		}
674
675		/**
676	<	* Returns a stream with the given {@code streamSize} number of
677	<	* pseudorandom {@code long} values.
676	>	* Returns a stream producing the given {@code streamSize} number
677	>	* of pseudorandom {@code long} values from this generator and/or
678	>	* one split from it.
679		*
680		* @param streamSize the number of values to generate
681	<	* @return a stream of {@code long} values
681	>	* @return a stream of pseudorandom {@code long} values
682		* @throws IllegalArgumentException if {@code streamSize} is
683	<	* less than zero
683	>	*         less than zero
684		*/
685		public LongStream longs(long streamSize) {
686		if (streamSize < 0L)
687	<	throw new IllegalArgumentException("negative Stream size");
687	>	throw new IllegalArgumentException(BadSize);
688		return StreamSupport.longStream
689		(new RandomLongsSpliterator
690		(this, 0L, streamSize, Long.MAX_VALUE, 0L),
#	Line 690 | Line 692 | public class SplittableRandom {
692		}
693
694		/**
695	<	* Returns an effectively unlimited stream of pseudorandom {@code long}
696	<	* values.
695	>	* Returns an effectively unlimited stream of pseudorandom {@code
696	>	* long} values from this generator and/or one split from it.
697		*
698		* @implNote This method is implemented to be equivalent to {@code
699		* longs(Long.MAX_VALUE)}.
#	Line 706 | Line 708 | public class SplittableRandom {
708		}
709
710		/**
711	<	* Returns a stream with the given {@code streamSize} number of
712	<	* pseudorandom {@code long} values, each conforming to the
713	<	* given origin and bound.
711	>	* Returns a stream producing the given {@code streamSize} number of
712	>	* pseudorandom {@code long} values from this generator and/or one split
713	>	* from it; each value conforms to the given origin (inclusive) and bound
714	>	* (exclusive).
715		*
716		* @param streamSize the number of values to generate
717	<	* @param randomNumberOrigin the origin of each random value
718	<	* @param randomNumberBound the bound of each random value
717	>	* @param randomNumberOrigin the origin (inclusive) of each random value
718	>	* @param randomNumberBound the bound (exclusive) of each random value
719		* @return a stream of pseudorandom {@code long} values,
720	<	* each with the given origin and bound.
720	>	*         each with the given origin (inclusive) and bound (exclusive)
721		* @throws IllegalArgumentException if {@code streamSize} is
722	<	* less than zero.
720	<	* @throws IllegalArgumentException if {@code randomNumberOrigin}
722	>	*         less than zero, or {@code randomNumberOrigin}
723		*         is greater than or equal to {@code randomNumberBound}
724		*/
725		public LongStream longs(long streamSize, long randomNumberOrigin,
726		long randomNumberBound) {
727		if (streamSize < 0L)
728	<	throw new IllegalArgumentException("negative Stream size");
728	>	throw new IllegalArgumentException(BadSize);
729		if (randomNumberOrigin >= randomNumberBound)
730	<	throw new IllegalArgumentException("bound must be greater than origin");
730	>	throw new IllegalArgumentException(BadRange);
731		return StreamSupport.longStream
732		(new RandomLongsSpliterator
733		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 734 | Line 736 | public class SplittableRandom {
736
737		/**
738		* Returns an effectively unlimited stream of pseudorandom {@code
739	<	* long} values, each conforming to the given origin and bound.
739	>	* long} values from this generator and/or one split from it; each value
740	>	* conforms to the given origin (inclusive) and bound (exclusive).
741		*
742		* @implNote This method is implemented to be equivalent to {@code
743		* longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
744		*
745	<	* @param randomNumberOrigin the origin of each random value
746	<	* @param randomNumberBound the bound of each random value
745	>	* @param randomNumberOrigin the origin (inclusive) of each random value
746	>	* @param randomNumberBound the bound (exclusive) of each random value
747		* @return a stream of pseudorandom {@code long} values,
748	<	* each with the given origin and bound.
748	>	*         each with the given origin (inclusive) and bound (exclusive)
749		* @throws IllegalArgumentException if {@code randomNumberOrigin}
750		*         is greater than or equal to {@code randomNumberBound}
751		*/
752		public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
753		if (randomNumberOrigin >= randomNumberBound)
754	<	throw new IllegalArgumentException("bound must be greater than origin");
754	>	throw new IllegalArgumentException(BadRange);
755		return StreamSupport.longStream
756		(new RandomLongsSpliterator
757		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 756 | Line 759 | public class SplittableRandom {
759		}
760
761		/**
762	<	* Returns a stream with the given {@code streamSize} number of
763	<	* pseudorandom {@code double} values, each between {@code 0.0}
764	<	* (inclusive) and {@code 1.0} (exclusive).
762	>	* Returns a stream producing the given {@code streamSize} number of
763	>	* pseudorandom {@code double} values from this generator and/or one split
764	>	* from it; each value is between zero (inclusive) and one (exclusive).
765		*
766		* @param streamSize the number of values to generate
767		* @return a stream of {@code double} values
768		* @throws IllegalArgumentException if {@code streamSize} is
769	<	* less than zero
769	>	*         less than zero
770		*/
771		public DoubleStream doubles(long streamSize) {
772		if (streamSize < 0L)
773	<	throw new IllegalArgumentException("negative Stream size");
773	>	throw new IllegalArgumentException(BadSize);
774		return StreamSupport.doubleStream
775		(new RandomDoublesSpliterator
776		(this, 0L, streamSize, Double.MAX_VALUE, 0.0),
#	Line 776 | Line 779 | public class SplittableRandom {
779
780		/**
781		* Returns an effectively unlimited stream of pseudorandom {@code
782	<	* double} values, each between {@code 0.0} (inclusive) and {@code
783	<	* 1.0} (exclusive).
782	>	* double} values from this generator and/or one split from it; each value
783	>	* is between zero (inclusive) and one (exclusive).
784		*
785		* @implNote This method is implemented to be equivalent to {@code
786		* doubles(Long.MAX_VALUE)}.
#	Line 792 | Line 795 | public class SplittableRandom {
795		}
796
797		/**
798	<	* Returns a stream with the given {@code streamSize} number of
799	<	* pseudorandom {@code double} values, each conforming to the
800	<	* given origin and bound.
798	>	* Returns a stream producing the given {@code streamSize} number of
799	>	* pseudorandom {@code double} values from this generator and/or one split
800	>	* from it; each value conforms to the given origin (inclusive) and bound
801	>	* (exclusive).
802		*
803		* @param streamSize the number of values to generate
804	<	* @param randomNumberOrigin the origin of each random value
805	<	* @param randomNumberBound the bound of each random value
804	>	* @param randomNumberOrigin the origin (inclusive) of each random value
805	>	* @param randomNumberBound the bound (exclusive) of each random value
806		* @return a stream of pseudorandom {@code double} values,
807	<	* each with the given origin and bound.
807	>	*         each with the given origin (inclusive) and bound (exclusive)
808		* @throws IllegalArgumentException if {@code streamSize} is
809	<	* less than zero.
809	>	*         less than zero
810		* @throws IllegalArgumentException if {@code randomNumberOrigin}
811		*         is greater than or equal to {@code randomNumberBound}
812		*/
813		public DoubleStream doubles(long streamSize, double randomNumberOrigin,
814		double randomNumberBound) {
815		if (streamSize < 0L)
816	<	throw new IllegalArgumentException("negative Stream size");
817	<	if (randomNumberOrigin >= randomNumberBound)
818	<	throw new IllegalArgumentException("bound must be greater than origin");
816	>	throw new IllegalArgumentException(BadSize);
817	>	if (!(randomNumberOrigin < randomNumberBound))
818	>	throw new IllegalArgumentException(BadRange);
819		return StreamSupport.doubleStream
820		(new RandomDoublesSpliterator
821		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 820 | Line 824 | public class SplittableRandom {
824
825		/**
826		* Returns an effectively unlimited stream of pseudorandom {@code
827	<	* double} values, each conforming to the given origin and bound.
827	>	* double} values from this generator and/or one split from it; each value
828	>	* conforms to the given origin (inclusive) and bound (exclusive).
829		*
830		* @implNote This method is implemented to be equivalent to {@code
831		* doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
832		*
833	<	* @param randomNumberOrigin the origin of each random value
834	<	* @param randomNumberBound the bound of each random value
833	>	* @param randomNumberOrigin the origin (inclusive) of each random value
834	>	* @param randomNumberBound the bound (exclusive) of each random value
835		* @return a stream of pseudorandom {@code double} values,
836	<	* each with the given origin and bound.
836	>	*         each with the given origin (inclusive) and bound (exclusive)
837		* @throws IllegalArgumentException if {@code randomNumberOrigin}
838		*         is greater than or equal to {@code randomNumberBound}
839		*/
840		public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
841	<	if (randomNumberOrigin >= randomNumberBound)
842	<	throw new IllegalArgumentException("bound must be greater than origin");
841	>	if (!(randomNumberOrigin < randomNumberBound))
842	>	throw new IllegalArgumentException(BadRange);
843		return StreamSupport.doubleStream
844		(new RandomDoublesSpliterator
845		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 843 | Line 848 | public class SplittableRandom {
848
849		/**
850		* Spliterator for int streams.  We multiplex the four int
851	<	* versions into one class by treating and bound < origin as
851	>	* versions into one class by treating a bound less than origin as
852		* unbounded, and also by treating "infinite" as equivalent to
853		* Long.MAX_VALUE. For splits, it uses the standard divide-by-two
854		* approach. The long and double versions of this class are
855		* identical except for types.
856		*/
857	<	static class RandomIntsSpliterator implements Spliterator.OfInt {
857	>	static final class RandomIntsSpliterator implements Spliterator.OfInt {
858		final SplittableRandom rng;
859		long index;
860		final long fence;
#	Line 892 | Line 897 | public class SplittableRandom {
897		long i = index, f = fence;
898		if (i < f) {
899		index = f;
900	+	SplittableRandom r = rng;
901		int o = origin, b = bound;
902		do {
903	<	consumer.accept(rng.internalNextInt(o, b));
903	>	consumer.accept(r.internalNextInt(o, b));
904		} while (++i < f);
905		}
906		}
#	Line 903 | Line 909 | public class SplittableRandom {
909		/**
910		* Spliterator for long streams.
911		*/
912	<	static class RandomLongsSpliterator implements Spliterator.OfLong {
912	>	static final class RandomLongsSpliterator implements Spliterator.OfLong {
913		final SplittableRandom rng;
914		long index;
915		final long fence;
#	Line 946 | Line 952 | public class SplittableRandom {
952		long i = index, f = fence;
953		if (i < f) {
954		index = f;
955	+	SplittableRandom r = rng;
956		long o = origin, b = bound;
957		do {
958	<	consumer.accept(rng.internalNextLong(o, b));
958	>	consumer.accept(r.internalNextLong(o, b));
959		} while (++i < f);
960		}
961		}
#	Line 958 | Line 965 | public class SplittableRandom {
965		/**
966		* Spliterator for double streams.
967		*/
968	<	static class RandomDoublesSpliterator implements Spliterator.OfDouble {
968	>	static final class RandomDoublesSpliterator implements Spliterator.OfDouble {
969		final SplittableRandom rng;
970		long index;
971		final long fence;
#	Line 1001 | Line 1008 | public class SplittableRandom {
1008		long i = index, f = fence;
1009		if (i < f) {
1010		index = f;
1011	+	SplittableRandom r = rng;
1012		double o = origin, b = bound;
1013		do {
1014	<	consumer.accept(rng.internalNextDouble(o, b));
1014	>	consumer.accept(r.internalNextDouble(o, b));
1015		} while (++i < f);
1016		}
1017		}
1018		}
1019
1020		}
1013	–

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