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1 : dl 1.1 /*
2 :     * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
3 :     * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 :     *
5 :     * This code is free software; you can redistribute it and/or modify it
6 :     * under the terms of the GNU General Public License version 2 only, as
7 :     * published by the Free Software Foundation. Oracle designates this
8 :     * particular file as subject to the "Classpath" exception as provided
9 :     * by Oracle in the LICENSE file that accompanied this code.
10 :     *
11 :     * This code is distributed in the hope that it will be useful, but WITHOUT
12 :     * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 :     * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 :     * version 2 for more details (a copy is included in the LICENSE file that
15 :     * accompanied this code).
16 :     *
17 :     * You should have received a copy of the GNU General Public License version
18 :     * 2 along with this work; if not, write to the Free Software Foundation,
19 :     * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 :     *
21 :     * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 :     * or visit www.oracle.com if you need additional information or have any
23 :     * questions.
24 :     */
25 :    
26 :     package java.util;
27 :    
28 :     import java.util.concurrent.atomic.AtomicLong;
29 :     import java.util.function.IntConsumer;
30 :     import java.util.function.LongConsumer;
31 :     import java.util.function.DoubleConsumer;
32 :     import java.util.stream.StreamSupport;
33 :     import java.util.stream.IntStream;
34 :     import java.util.stream.LongStream;
35 :     import java.util.stream.DoubleStream;
36 :    
37 :     /**
38 :     * A generator of uniform pseudorandom values applicable for use in
39 :     * (among other contexts) isolated parallel computations that may
40 : dl 1.18 * generate subtasks. Class {@code SplittableRandom} supports methods for
41 : jsr166 1.3 * producing pseudorandom numbers of type {@code int}, {@code long},
42 : dl 1.1 * and {@code double} with similar usages as for class
43 : jsr166 1.9 * {@link java.util.Random} but differs in the following ways:
44 :     *
45 :     * <ul>
46 : dl 1.1 *
47 :     * <li>Series of generated values pass the DieHarder suite testing
48 :     * independence and uniformity properties of random number generators.
49 :     * (Most recently validated with <a
50 :     * href="http://www.phy.duke.edu/~rgb/General/dieharder.php"> version
51 :     * 3.31.1</a>.) These tests validate only the methods for certain
52 :     * types and ranges, but similar properties are expected to hold, at
53 : dl 1.11 * least approximately, for others as well. The <em>period</em>
54 :     * (length of any series of generated values before it repeats) is at
55 :     * least 2<sup>64</sup>. </li>
56 : dl 1.1 *
57 :     * <li> Method {@link #split} constructs and returns a new
58 :     * SplittableRandom instance that shares no mutable state with the
59 : dl 1.7 * current instance. However, with very high probability, the
60 :     * values collectively generated by the two objects have the same
61 : dl 1.1 * statistical properties as if the same quantity of values were
62 :     * generated by a single thread using a single {@code
63 :     * SplittableRandom} object. </li>
64 :     *
65 :     * <li>Instances of SplittableRandom are <em>not</em> thread-safe.
66 :     * They are designed to be split, not shared, across threads. For
67 :     * example, a {@link java.util.concurrent.ForkJoinTask
68 :     * fork/join-style} computation using random numbers might include a
69 :     * construction of the form {@code new
70 :     * Subtask(aSplittableRandom.split()).fork()}.
71 :     *
72 :     * <li>This class provides additional methods for generating random
73 :     * streams, that employ the above techniques when used in {@code
74 :     * stream.parallel()} mode.</li>
75 :     *
76 :     * </ul>
77 :     *
78 : dl 1.18 * <p>Instances of {@code SplittableRandom} are not cryptographically
79 :     * secure. Consider instead using {@link java.security.SecureRandom}
80 :     * in security-sensitive applications. Additionally,
81 :     * default-constructed instances do not use a cryptographically random
82 :     * seed unless the {@linkplain System#getProperty system property}
83 :     * {@code java.util.secureRandomSeed} is set to {@code true}.
84 :     *
85 : dl 1.1 * @author Guy Steele
86 : dl 1.2 * @author Doug Lea
87 : dl 1.1 * @since 1.8
88 :     */
89 : dl 1.23 public final class SplittableRandom {
90 : dl 1.1
91 :     /*
92 :     * Implementation Overview.
93 :     *
94 :     * This algorithm was inspired by the "DotMix" algorithm by
95 :     * Leiserson, Schardl, and Sukha "Deterministic Parallel
96 :     * Random-Number Generation for Dynamic-Multithreading Platforms",
97 : dl 1.15 * PPoPP 2012, as well as those in "Parallel random numbers: as
98 :     * easy as 1, 2, 3" by Salmon, Morae, Dror, and Shaw, SC 2011. It
99 :     * differs mainly in simplifying and cheapening operations.
100 :     *
101 :     * The primary update step (method nextSeed()) is to add a
102 :     * constant ("gamma") to the current (64 bit) seed, forming a
103 :     * simple sequence. The seed and the gamma values for any two
104 :     * SplittableRandom instances are highly likely to be different.
105 :     *
106 :     * Methods nextLong, nextInt, and derivatives do not return the
107 :     * sequence (seed) values, but instead a hash-like bit-mix of
108 :     * their bits, producing more independently distributed sequences.
109 : dl 1.21 * For nextLong, the mix64 function is based on David Stafford's
110 :     * (http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html)
111 :     * "Mix13" variant of the "64-bit finalizer" function in Austin
112 : dl 1.24 * Appleby's MurmurHash3 algorithm (see
113 :     * http://code.google.com/p/smhasher/wiki/MurmurHash3). The mix32
114 : dl 1.21 * function is based on Stafford's Mix04 mix function, but returns
115 :     * the upper 32 bits cast as int.
116 : dl 1.15 *
117 :     * The split operation uses the current generator to form the seed
118 :     * and gamma for another SplittableRandom. To conservatively
119 :     * avoid potential correlations between seed and value generation,
120 : dl 1.21 * gamma selection (method mixGamma) uses different
121 :     * (Murmurhash3's) mix constants. To avoid potential weaknesses
122 :     * in bit-mixing transformations, we restrict gammas to odd values
123 :     * with at least 24 0-1 or 1-0 bit transitions. Rather than
124 :     * rejecting candidates with too few or too many bits set, method
125 :     * mixGamma flips some bits (which has the effect of mapping at
126 :     * most 4 to any given gamma value). This reduces the effective
127 :     * set of 64bit odd gamma values by about 2%, and serves as an
128 : dl 1.15 * automated screening for sequence constant selection that is
129 :     * left as an empirical decision in some other hashing and crypto
130 :     * algorithms.
131 :     *
132 :     * The resulting generator thus transforms a sequence in which
133 :     * (typically) many bits change on each step, with an inexpensive
134 :     * mixer with good (but less than cryptographically secure)
135 :     * avalanching.
136 :     *
137 :     * The default (no-argument) constructor, in essence, invokes
138 : dl 1.21 * split() for a common "defaultGen" SplittableRandom. Unlike
139 :     * other cases, this split must be performed in a thread-safe
140 :     * manner, so we use an AtomicLong to represent the seed rather
141 :     * than use an explicit SplittableRandom. To bootstrap the
142 : dl 1.25 * defaultGen, we start off using a seed based on current time
143 :     * unless the java.util.secureRandomSeed property is set. This
144 :     * serves as a slimmed-down (and insecure) variant of SecureRandom
145 :     * that also avoids stalls that may occur when using /dev/random.
146 : dl 1.15 *
147 :     * It is a relatively simple matter to apply the basic design here
148 :     * to use 128 bit seeds. However, emulating 128bit arithmetic and
149 :     * carrying around twice the state add more overhead than appears
150 :     * warranted for current usages.
151 : dl 1.13 *
152 : dl 1.15 * File organization: First the non-public methods that constitute
153 :     * the main algorithm, then the main public methods, followed by
154 :     * some custom spliterator classes needed for stream methods.
155 : dl 1.1 */
156 :    
157 :     /**
158 : dl 1.21 * The golden ratio scaled to 64bits, used as the initial gamma
159 :     * value for (unsplit) SplittableRandoms.
160 : dl 1.1 */
161 : dl 1.21 private static final long GOLDEN_GAMMA = 0x9e3779b97f4a7c15L;
162 : dl 1.11
163 :     /**
164 : dl 1.5 * The least non-zero value returned by nextDouble(). This value
165 : dl 1.7 * is scaled by a random value of 53 bits to produce a result.
166 : dl 1.5 */
167 : dl 1.24 private static final double DOUBLE_UNIT = 0x1.0p-53; // 1.0 / (1L << 53);
168 : dl 1.5
169 :     /**
170 : dl 1.15 * The seed. Updated only via method nextSeed.
171 : dl 1.1 */
172 :     private long seed;
173 :    
174 :     /**
175 : dl 1.15 * The step value.
176 : dl 1.1 */
177 :     private final long gamma;
178 :    
179 :     /**
180 : dl 1.15 * Internal constructor used by all others except default constructor.
181 : dl 1.1 */
182 : dl 1.15 private SplittableRandom(long seed, long gamma) {
183 :     this.seed = seed;
184 :     this.gamma = gamma;
185 : dl 1.1 }
186 :    
187 :     /**
188 : dl 1.21 * Computes Stafford variant 13 of 64bit mix function.
189 : dl 1.1 */
190 :     private static long mix64(long z) {
191 : dl 1.24 z = (z ^ (z >>> 30)) * 0xbf58476d1ce4e5b9L;
192 :     z = (z ^ (z >>> 27)) * 0x94d049bb133111ebL;
193 :     return z ^ (z >>> 31);
194 : dl 1.21 }
195 :    
196 : dl 1.1 /**
197 : dl 1.21 * Returns the 32 high bits of Stafford variant 4 mix64 function as int.
198 : dl 1.1 */
199 :     private static int mix32(long z) {
200 : dl 1.24 z = (z ^ (z >>> 33)) * 0x62a9d9ed799705f5L;
201 : dl 1.21 return (int)(((z ^ (z >>> 28)) * 0xcb24d0a5c88c35b3L) >>> 32);
202 : dl 1.1 }
203 :    
204 :     /**
205 : dl 1.15 * Returns the gamma value to use for a new split instance.
206 : dl 1.13 */
207 : dl 1.21 private static long mixGamma(long z) {
208 : dl 1.24 z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL; // MurmurHash3 mix constants
209 : dl 1.21 z = (z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L;
210 :     z = (z ^ (z >>> 33)) | 1L; // force to be odd
211 :     int n = Long.bitCount(z ^ (z >>> 1)); // ensure enough transitions
212 :     return (n < 24) ? z ^ 0xaaaaaaaaaaaaaaaaL : z;
213 : dl 1.13 }
214 :    
215 :     /**
216 : dl 1.15 * Adds gamma to seed.
217 : dl 1.7 */
218 : dl 1.15 private long nextSeed() {
219 :     return seed += gamma;
220 : dl 1.7 }
221 :    
222 :     /**
223 : dl 1.15 * The seed generator for default constructors.
224 : dl 1.7 */
225 : dl 1.21 private static final AtomicLong defaultGen = new AtomicLong(initialSeed());
226 : dl 1.7
227 : dl 1.18 private static long initialSeed() {
228 : dl 1.21 String pp = java.security.AccessController.doPrivileged(
229 :     new sun.security.action.GetPropertyAction(
230 :     "java.util.secureRandomSeed"));
231 :     if (pp != null && pp.equalsIgnoreCase("true")) {
232 :     byte[] seedBytes = java.security.SecureRandom.getSeed(8);
233 :     long s = (long)(seedBytes[0]) & 0xffL;
234 :     for (int i = 1; i < 8; ++i)
235 :     s = (s << 8) | ((long)(seedBytes[i]) & 0xffL);
236 :     return s;
237 : dl 1.18 }
238 : dl 1.25 return (mix64(System.currentTimeMillis()) ^
239 : dl 1.18 mix64(System.nanoTime()));
240 : dl 1.1 }
241 :    
242 : dl 1.15 // IllegalArgumentException messages
243 :     static final String BadBound = "bound must be positive";
244 :     static final String BadRange = "bound must be greater than origin";
245 :     static final String BadSize = "size must be non-negative";
246 : dl 1.12
247 : dl 1.1 /*
248 :     * Internal versions of nextX methods used by streams, as well as
249 :     * the public nextX(origin, bound) methods. These exist mainly to
250 :     * avoid the need for multiple versions of stream spliterators
251 :     * across the different exported forms of streams.
252 :     */
253 :    
254 :     /**
255 :     * The form of nextLong used by LongStream Spliterators. If
256 :     * origin is greater than bound, acts as unbounded form of
257 :     * nextLong, else as bounded form.
258 :     *
259 :     * @param origin the least value, unless greater than bound
260 :     * @param bound the upper bound (exclusive), must not equal origin
261 :     * @return a pseudorandom value
262 :     */
263 :     final long internalNextLong(long origin, long bound) {
264 :     /*
265 :     * Four Cases:
266 :     *
267 :     * 1. If the arguments indicate unbounded form, act as
268 :     * nextLong().
269 :     *
270 :     * 2. If the range is an exact power of two, apply the
271 :     * associated bit mask.
272 :     *
273 :     * 3. If the range is positive, loop to avoid potential bias
274 :     * when the implicit nextLong() bound (2<sup>64</sup>) is not
275 :     * evenly divisible by the range. The loop rejects candidates
276 :     * computed from otherwise over-represented values. The
277 :     * expected number of iterations under an ideal generator
278 : dl 1.4 * varies from 1 to 2, depending on the bound. The loop itself
279 :     * takes an unlovable form. Because the first candidate is
280 :     * already available, we need a break-in-the-middle
281 :     * construction, which is concisely but cryptically performed
282 :     * within the while-condition of a body-less for loop.
283 : dl 1.1 *
284 :     * 4. Otherwise, the range cannot be represented as a positive
285 : dl 1.4 * long. The loop repeatedly generates unbounded longs until
286 :     * obtaining a candidate meeting constraints (with an expected
287 :     * number of iterations of less than two).
288 : dl 1.1 */
289 :    
290 :     long r = mix64(nextSeed());
291 :     if (origin < bound) {
292 :     long n = bound - origin, m = n - 1;
293 : dl 1.7 if ((n & m) == 0L) // power of two
294 : dl 1.1 r = (r & m) + origin;
295 : dl 1.7 else if (n > 0L) { // reject over-represented candidates
296 : dl 1.1 for (long u = r >>> 1; // ensure nonnegative
297 : dl 1.7 u + m - (r = u % n) < 0L; // rejection check
298 : dl 1.1 u = mix64(nextSeed()) >>> 1) // retry
299 :     ;
300 :     r += origin;
301 :     }
302 : dl 1.7 else { // range not representable as long
303 : dl 1.1 while (r < origin || r >= bound)
304 :     r = mix64(nextSeed());
305 :     }
306 :     }
307 :     return r;
308 :     }
309 :    
310 :     /**
311 :     * The form of nextInt used by IntStream Spliterators.
312 :     * Exactly the same as long version, except for types.
313 :     *
314 :     * @param origin the least value, unless greater than bound
315 :     * @param bound the upper bound (exclusive), must not equal origin
316 :     * @return a pseudorandom value
317 :     */
318 :     final int internalNextInt(int origin, int bound) {
319 :     int r = mix32(nextSeed());
320 :     if (origin < bound) {
321 :     int n = bound - origin, m = n - 1;
322 : dl 1.13 if ((n & m) == 0)
323 : dl 1.1 r = (r & m) + origin;
324 :     else if (n > 0) {
325 :     for (int u = r >>> 1;
326 : dl 1.7 u + m - (r = u % n) < 0;
327 : dl 1.1 u = mix32(nextSeed()) >>> 1)
328 :     ;
329 :     r += origin;
330 :     }
331 :     else {
332 :     while (r < origin || r >= bound)
333 :     r = mix32(nextSeed());
334 :     }
335 :     }
336 :     return r;
337 :     }
338 :    
339 :     /**
340 :     * The form of nextDouble used by DoubleStream Spliterators.
341 :     *
342 :     * @param origin the least value, unless greater than bound
343 :     * @param bound the upper bound (exclusive), must not equal origin
344 :     * @return a pseudorandom value
345 :     */
346 :     final double internalNextDouble(double origin, double bound) {
347 : dl 1.24 double r = (nextLong() >>> 11) * DOUBLE_UNIT;
348 : dl 1.1 if (origin < bound) {
349 :     r = r * (bound - origin) + origin;
350 : dl 1.7 if (r >= bound) // correct for rounding
351 : dl 1.1 r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
352 :     }
353 :     return r;
354 :     }
355 :    
356 :     /* ---------------- public methods ---------------- */
357 :    
358 :     /**
359 : dl 1.7 * Creates a new SplittableRandom instance using the specified
360 :     * initial seed. SplittableRandom instances created with the same
361 : dl 1.11 * seed in the same program generate identical sequences of values.
362 : dl 1.1 *
363 :     * @param seed the initial seed
364 :     */
365 :     public SplittableRandom(long seed) {
366 : dl 1.21 this(seed, GOLDEN_GAMMA);
367 : dl 1.1 }
368 :    
369 :     /**
370 :     * Creates a new SplittableRandom instance that is likely to
371 :     * generate sequences of values that are statistically independent
372 :     * of those of any other instances in the current program; and
373 :     * may, and typically does, vary across program invocations.
374 :     */
375 : dl 1.21 public SplittableRandom() { // emulate defaultGen.split()
376 : dl 1.23 long s = defaultGen.getAndAdd(2 * GOLDEN_GAMMA);
377 : dl 1.21 this.seed = mix64(s);
378 :     this.gamma = mixGamma(s + GOLDEN_GAMMA);
379 : dl 1.1 }
380 :    
381 :     /**
382 :     * Constructs and returns a new SplittableRandom instance that
383 :     * shares no mutable state with this instance. However, with very
384 :     * high probability, the set of values collectively generated by
385 :     * the two objects has the same statistical properties as if the
386 :     * same quantity of values were generated by a single thread using
387 :     * a single SplittableRandom object. Either or both of the two
388 :     * objects may be further split using the {@code split()} method,
389 :     * and the same expected statistical properties apply to the
390 :     * entire set of generators constructed by such recursive
391 :     * splitting.
392 :     *
393 :     * @return the new SplittableRandom instance
394 :     */
395 :     public SplittableRandom split() {
396 : dl 1.21 return new SplittableRandom(nextLong(), mixGamma(nextSeed()));
397 : dl 1.1 }
398 :    
399 :     /**
400 :     * Returns a pseudorandom {@code int} value.
401 :     *
402 : dl 1.7 * @return a pseudorandom {@code int} value
403 : dl 1.1 */
404 :     public int nextInt() {
405 :     return mix32(nextSeed());
406 :     }
407 :    
408 :     /**
409 : dl 1.7 * Returns a pseudorandom {@code int} value between zero (inclusive)
410 : dl 1.1 * and the specified bound (exclusive).
411 :     *
412 : dl 1.18 * @param bound the upper bound (exclusive). Must be positive.
413 : dl 1.7 * @return a pseudorandom {@code int} value between zero
414 : jsr166 1.10 * (inclusive) and the bound (exclusive)
415 : dl 1.16 * @throws IllegalArgumentException if {@code bound} is not positive
416 : dl 1.1 */
417 :     public int nextInt(int bound) {
418 :     if (bound <= 0)
419 : dl 1.15 throw new IllegalArgumentException(BadBound);
420 : dl 1.1 // Specialize internalNextInt for origin 0
421 :     int r = mix32(nextSeed());
422 :     int m = bound - 1;
423 : dl 1.13 if ((bound & m) == 0) // power of two
424 : dl 1.1 r &= m;
425 :     else { // reject over-represented candidates
426 :     for (int u = r >>> 1;
427 : dl 1.7 u + m - (r = u % bound) < 0;
428 : dl 1.1 u = mix32(nextSeed()) >>> 1)
429 :     ;
430 :     }
431 :     return r;
432 :     }
433 :    
434 :     /**
435 :     * Returns a pseudorandom {@code int} value between the specified
436 :     * origin (inclusive) and the specified bound (exclusive).
437 :     *
438 :     * @param origin the least value returned
439 :     * @param bound the upper bound (exclusive)
440 :     * @return a pseudorandom {@code int} value between the origin
441 : jsr166 1.10 * (inclusive) and the bound (exclusive)
442 : dl 1.7 * @throws IllegalArgumentException if {@code origin} is greater than
443 : dl 1.1 * or equal to {@code bound}
444 :     */
445 :     public int nextInt(int origin, int bound) {
446 :     if (origin >= bound)
447 : dl 1.15 throw new IllegalArgumentException(BadRange);
448 : dl 1.1 return internalNextInt(origin, bound);
449 :     }
450 :    
451 :     /**
452 :     * Returns a pseudorandom {@code long} value.
453 :     *
454 : dl 1.7 * @return a pseudorandom {@code long} value
455 : dl 1.1 */
456 :     public long nextLong() {
457 :     return mix64(nextSeed());
458 :     }
459 :    
460 :     /**
461 : dl 1.7 * Returns a pseudorandom {@code long} value between zero (inclusive)
462 : dl 1.1 * and the specified bound (exclusive).
463 :     *
464 : dl 1.18 * @param bound the upper bound (exclusive). Must be positive.
465 : dl 1.7 * @return a pseudorandom {@code long} value between zero
466 : jsr166 1.10 * (inclusive) and the bound (exclusive)
467 : dl 1.16 * @throws IllegalArgumentException if {@code bound} is not positive
468 : dl 1.1 */
469 :     public long nextLong(long bound) {
470 :     if (bound <= 0)
471 : dl 1.15 throw new IllegalArgumentException(BadBound);
472 : dl 1.1 // Specialize internalNextLong for origin 0
473 :     long r = mix64(nextSeed());
474 :     long m = bound - 1;
475 :     if ((bound & m) == 0L) // power of two
476 :     r &= m;
477 :     else { // reject over-represented candidates
478 :     for (long u = r >>> 1;
479 :     u + m - (r = u % bound) < 0L;
480 :     u = mix64(nextSeed()) >>> 1)
481 :     ;
482 :     }
483 :     return r;
484 :     }
485 :    
486 :     /**
487 :     * Returns a pseudorandom {@code long} value between the specified
488 :     * origin (inclusive) and the specified bound (exclusive).
489 :     *
490 :     * @param origin the least value returned
491 :     * @param bound the upper bound (exclusive)
492 :     * @return a pseudorandom {@code long} value between the origin
493 : jsr166 1.10 * (inclusive) and the bound (exclusive)
494 : dl 1.7 * @throws IllegalArgumentException if {@code origin} is greater than
495 : dl 1.1 * or equal to {@code bound}
496 :     */
497 :     public long nextLong(long origin, long bound) {
498 :     if (origin >= bound)
499 : dl 1.15 throw new IllegalArgumentException(BadRange);
500 : dl 1.1 return internalNextLong(origin, bound);
501 :     }
502 :    
503 :     /**
504 : dl 1.7 * Returns a pseudorandom {@code double} value between zero
505 :     * (inclusive) and one (exclusive).
506 : dl 1.1 *
507 : dl 1.7 * @return a pseudorandom {@code double} value between zero
508 : dl 1.18 * (inclusive) and one (exclusive)
509 : dl 1.1 */
510 :     public double nextDouble() {
511 : dl 1.24 return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT;
512 : dl 1.1 }
513 :    
514 :     /**
515 :     * Returns a pseudorandom {@code double} value between 0.0
516 :     * (inclusive) and the specified bound (exclusive).
517 :     *
518 : dl 1.18 * @param bound the upper bound (exclusive). Must be positive.
519 : dl 1.7 * @return a pseudorandom {@code double} value between zero
520 : jsr166 1.10 * (inclusive) and the bound (exclusive)
521 : dl 1.16 * @throws IllegalArgumentException if {@code bound} is not positive
522 : dl 1.1 */
523 :     public double nextDouble(double bound) {
524 : dl 1.7 if (!(bound > 0.0))
525 : dl 1.15 throw new IllegalArgumentException(BadBound);
526 : dl 1.24 double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound;
527 : dl 1.1 return (result < bound) ? result : // correct for rounding
528 :     Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
529 :     }
530 :    
531 :     /**
532 : dl 1.7 * Returns a pseudorandom {@code double} value between the specified
533 : dl 1.1 * origin (inclusive) and bound (exclusive).
534 :     *
535 :     * @param origin the least value returned
536 : dl 1.18 * @param bound the upper bound (exclusive)
537 : dl 1.1 * @return a pseudorandom {@code double} value between the origin
538 : jsr166 1.10 * (inclusive) and the bound (exclusive)
539 : dl 1.1 * @throws IllegalArgumentException if {@code origin} is greater than
540 :     * or equal to {@code bound}
541 :     */
542 :     public double nextDouble(double origin, double bound) {
543 : dl 1.7 if (!(origin < bound))
544 : dl 1.15 throw new IllegalArgumentException(BadRange);
545 : dl 1.1 return internalNextDouble(origin, bound);
546 :     }
547 :    
548 : dl 1.11 /**
549 :     * Returns a pseudorandom {@code boolean} value.
550 :     *
551 :     * @return a pseudorandom {@code boolean} value
552 :     */
553 :     public boolean nextBoolean() {
554 :     return mix32(nextSeed()) < 0;
555 :     }
556 :    
557 : dl 1.1 // stream methods, coded in a way intended to better isolate for
558 :     // maintenance purposes the small differences across forms.
559 :    
560 :     /**
561 : dl 1.16 * Returns a stream producing the given {@code streamSize} number
562 :     * of pseudorandom {@code int} values from this generator and/or
563 :     * one split from it.
564 : dl 1.1 *
565 :     * @param streamSize the number of values to generate
566 :     * @return a stream of pseudorandom {@code int} values
567 :     * @throws IllegalArgumentException if {@code streamSize} is
568 : dl 1.7 * less than zero
569 : dl 1.1 */
570 :     public IntStream ints(long streamSize) {
571 :     if (streamSize < 0L)
572 : dl 1.15 throw new IllegalArgumentException(BadSize);
573 : dl 1.1 return StreamSupport.intStream
574 :     (new RandomIntsSpliterator
575 :     (this, 0L, streamSize, Integer.MAX_VALUE, 0),
576 :     false);
577 :     }
578 :    
579 :     /**
580 :     * Returns an effectively unlimited stream of pseudorandom {@code int}
581 : dl 1.16 * values from this generator and/or one split from it.
582 : dl 1.1 *
583 :     * @implNote This method is implemented to be equivalent to {@code
584 :     * ints(Long.MAX_VALUE)}.
585 :     *
586 :     * @return a stream of pseudorandom {@code int} values
587 :     */
588 :     public IntStream ints() {
589 :     return StreamSupport.intStream
590 :     (new RandomIntsSpliterator
591 :     (this, 0L, Long.MAX_VALUE, Integer.MAX_VALUE, 0),
592 :     false);
593 :     }
594 :    
595 :     /**
596 : dl 1.16 * Returns a stream producing the given {@code streamSize} number
597 : dl 1.18 * of pseudorandom {@code int} values from this generator and/or one split
598 :     * from it; each value conforms to the given origin (inclusive) and bound
599 :     * (exclusive).
600 : dl 1.1 *
601 :     * @param streamSize the number of values to generate
602 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
603 :     * @param randomNumberBound the bound (exclusive) of each random value
604 : dl 1.1 * @return a stream of pseudorandom {@code int} values,
605 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
606 : dl 1.1 * @throws IllegalArgumentException if {@code streamSize} is
607 : dl 1.7 * less than zero, or {@code randomNumberOrigin}
608 : dl 1.1 * is greater than or equal to {@code randomNumberBound}
609 :     */
610 :     public IntStream ints(long streamSize, int randomNumberOrigin,
611 :     int randomNumberBound) {
612 :     if (streamSize < 0L)
613 : dl 1.15 throw new IllegalArgumentException(BadSize);
614 : dl 1.1 if (randomNumberOrigin >= randomNumberBound)
615 : dl 1.15 throw new IllegalArgumentException(BadRange);
616 : dl 1.1 return StreamSupport.intStream
617 :     (new RandomIntsSpliterator
618 :     (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
619 :     false);
620 :     }
621 :    
622 :     /**
623 :     * Returns an effectively unlimited stream of pseudorandom {@code
624 : dl 1.18 * int} values from this generator and/or one split from it; each value
625 :     * conforms to the given origin (inclusive) and bound (exclusive).
626 : dl 1.1 *
627 :     * @implNote This method is implemented to be equivalent to {@code
628 :     * ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
629 :     *
630 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
631 :     * @param randomNumberBound the bound (exclusive) of each random value
632 : dl 1.1 * @return a stream of pseudorandom {@code int} values,
633 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
634 : dl 1.1 * @throws IllegalArgumentException if {@code randomNumberOrigin}
635 :     * is greater than or equal to {@code randomNumberBound}
636 :     */
637 :     public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
638 :     if (randomNumberOrigin >= randomNumberBound)
639 : dl 1.15 throw new IllegalArgumentException(BadRange);
640 : dl 1.1 return StreamSupport.intStream
641 :     (new RandomIntsSpliterator
642 :     (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
643 :     false);
644 :     }
645 :    
646 :     /**
647 : dl 1.16 * Returns a stream producing the given {@code streamSize} number
648 :     * of pseudorandom {@code long} values from this generator and/or
649 :     * one split from it.
650 : dl 1.1 *
651 :     * @param streamSize the number of values to generate
652 : dl 1.7 * @return a stream of pseudorandom {@code long} values
653 : dl 1.1 * @throws IllegalArgumentException if {@code streamSize} is
654 : dl 1.7 * less than zero
655 : dl 1.1 */
656 :     public LongStream longs(long streamSize) {
657 :     if (streamSize < 0L)
658 : dl 1.15 throw new IllegalArgumentException(BadSize);
659 : dl 1.1 return StreamSupport.longStream
660 :     (new RandomLongsSpliterator
661 :     (this, 0L, streamSize, Long.MAX_VALUE, 0L),
662 :     false);
663 :     }
664 :    
665 :     /**
666 : dl 1.16 * Returns an effectively unlimited stream of pseudorandom {@code
667 :     * long} values from this generator and/or one split from it.
668 : dl 1.1 *
669 :     * @implNote This method is implemented to be equivalent to {@code
670 :     * longs(Long.MAX_VALUE)}.
671 :     *
672 :     * @return a stream of pseudorandom {@code long} values
673 :     */
674 :     public LongStream longs() {
675 :     return StreamSupport.longStream
676 :     (new RandomLongsSpliterator
677 :     (this, 0L, Long.MAX_VALUE, Long.MAX_VALUE, 0L),
678 :     false);
679 :     }
680 :    
681 :     /**
682 : dl 1.7 * Returns a stream producing the given {@code streamSize} number of
683 : dl 1.18 * pseudorandom {@code long} values from this generator and/or one split
684 :     * from it; each value conforms to the given origin (inclusive) and bound
685 :     * (exclusive).
686 : dl 1.1 *
687 :     * @param streamSize the number of values to generate
688 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
689 :     * @param randomNumberBound the bound (exclusive) of each random value
690 : dl 1.1 * @return a stream of pseudorandom {@code long} values,
691 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
692 : dl 1.1 * @throws IllegalArgumentException if {@code streamSize} is
693 : dl 1.7 * less than zero, or {@code randomNumberOrigin}
694 : dl 1.1 * is greater than or equal to {@code randomNumberBound}
695 :     */
696 :     public LongStream longs(long streamSize, long randomNumberOrigin,
697 :     long randomNumberBound) {
698 :     if (streamSize < 0L)
699 : dl 1.15 throw new IllegalArgumentException(BadSize);
700 : dl 1.1 if (randomNumberOrigin >= randomNumberBound)
701 : dl 1.15 throw new IllegalArgumentException(BadRange);
702 : dl 1.1 return StreamSupport.longStream
703 :     (new RandomLongsSpliterator
704 :     (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
705 :     false);
706 :     }
707 :    
708 :     /**
709 :     * Returns an effectively unlimited stream of pseudorandom {@code
710 : dl 1.18 * long} values from this generator and/or one split from it; each value
711 :     * conforms to the given origin (inclusive) and bound (exclusive).
712 : dl 1.1 *
713 :     * @implNote This method is implemented to be equivalent to {@code
714 :     * longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
715 :     *
716 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
717 :     * @param randomNumberBound the bound (exclusive) of each random value
718 : dl 1.1 * @return a stream of pseudorandom {@code long} values,
719 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
720 : dl 1.1 * @throws IllegalArgumentException if {@code randomNumberOrigin}
721 :     * is greater than or equal to {@code randomNumberBound}
722 :     */
723 :     public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
724 :     if (randomNumberOrigin >= randomNumberBound)
725 : dl 1.15 throw new IllegalArgumentException(BadRange);
726 : dl 1.1 return StreamSupport.longStream
727 :     (new RandomLongsSpliterator
728 :     (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
729 :     false);
730 :     }
731 :    
732 :     /**
733 : dl 1.7 * Returns a stream producing the given {@code streamSize} number of
734 : dl 1.18 * pseudorandom {@code double} values from this generator and/or one split
735 :     * from it; each value is between zero (inclusive) and one (exclusive).
736 : dl 1.1 *
737 :     * @param streamSize the number of values to generate
738 :     * @return a stream of {@code double} values
739 :     * @throws IllegalArgumentException if {@code streamSize} is
740 : dl 1.7 * less than zero
741 : dl 1.1 */
742 :     public DoubleStream doubles(long streamSize) {
743 :     if (streamSize < 0L)
744 : dl 1.15 throw new IllegalArgumentException(BadSize);
745 : dl 1.1 return StreamSupport.doubleStream
746 :     (new RandomDoublesSpliterator
747 :     (this, 0L, streamSize, Double.MAX_VALUE, 0.0),
748 :     false);
749 :     }
750 :    
751 :     /**
752 :     * Returns an effectively unlimited stream of pseudorandom {@code
753 : dl 1.18 * double} values from this generator and/or one split from it; each value
754 :     * is between zero (inclusive) and one (exclusive).
755 : dl 1.1 *
756 :     * @implNote This method is implemented to be equivalent to {@code
757 :     * doubles(Long.MAX_VALUE)}.
758 :     *
759 :     * @return a stream of pseudorandom {@code double} values
760 :     */
761 :     public DoubleStream doubles() {
762 :     return StreamSupport.doubleStream
763 :     (new RandomDoublesSpliterator
764 :     (this, 0L, Long.MAX_VALUE, Double.MAX_VALUE, 0.0),
765 :     false);
766 :     }
767 :    
768 :     /**
769 : dl 1.7 * Returns a stream producing the given {@code streamSize} number of
770 : dl 1.18 * pseudorandom {@code double} values from this generator and/or one split
771 :     * from it; each value conforms to the given origin (inclusive) and bound
772 :     * (exclusive).
773 : dl 1.1 *
774 :     * @param streamSize the number of values to generate
775 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
776 :     * @param randomNumberBound the bound (exclusive) of each random value
777 : dl 1.1 * @return a stream of pseudorandom {@code double} values,
778 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
779 : dl 1.1 * @throws IllegalArgumentException if {@code streamSize} is
780 : dl 1.18 * less than zero
781 : dl 1.1 * @throws IllegalArgumentException if {@code randomNumberOrigin}
782 :     * is greater than or equal to {@code randomNumberBound}
783 :     */
784 :     public DoubleStream doubles(long streamSize, double randomNumberOrigin,
785 :     double randomNumberBound) {
786 :     if (streamSize < 0L)
787 : dl 1.15 throw new IllegalArgumentException(BadSize);
788 : dl 1.7 if (!(randomNumberOrigin < randomNumberBound))
789 : dl 1.15 throw new IllegalArgumentException(BadRange);
790 : dl 1.1 return StreamSupport.doubleStream
791 :     (new RandomDoublesSpliterator
792 :     (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
793 :     false);
794 :     }
795 :    
796 :     /**
797 :     * Returns an effectively unlimited stream of pseudorandom {@code
798 : dl 1.18 * double} values from this generator and/or one split from it; each value
799 :     * conforms to the given origin (inclusive) and bound (exclusive).
800 : dl 1.1 *
801 :     * @implNote This method is implemented to be equivalent to {@code
802 :     * doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
803 :     *
804 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
805 :     * @param randomNumberBound the bound (exclusive) of each random value
806 : dl 1.1 * @return a stream of pseudorandom {@code double} values,
807 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
808 : dl 1.1 * @throws IllegalArgumentException if {@code randomNumberOrigin}
809 :     * is greater than or equal to {@code randomNumberBound}
810 :     */
811 :     public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
812 : dl 1.7 if (!(randomNumberOrigin < randomNumberBound))
813 : dl 1.15 throw new IllegalArgumentException(BadRange);
814 : dl 1.1 return StreamSupport.doubleStream
815 :     (new RandomDoublesSpliterator
816 :     (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
817 :     false);
818 :     }
819 :    
820 :     /**
821 :     * Spliterator for int streams. We multiplex the four int
822 : dl 1.7 * versions into one class by treating a bound less than origin as
823 : dl 1.1 * unbounded, and also by treating "infinite" as equivalent to
824 :     * Long.MAX_VALUE. For splits, it uses the standard divide-by-two
825 :     * approach. The long and double versions of this class are
826 :     * identical except for types.
827 :     */
828 : dl 1.11 static final class RandomIntsSpliterator implements Spliterator.OfInt {
829 : dl 1.1 final SplittableRandom rng;
830 :     long index;
831 :     final long fence;
832 :     final int origin;
833 :     final int bound;
834 :     RandomIntsSpliterator(SplittableRandom rng, long index, long fence,
835 :     int origin, int bound) {
836 :     this.rng = rng; this.index = index; this.fence = fence;
837 :     this.origin = origin; this.bound = bound;
838 :     }
839 :    
840 :     public RandomIntsSpliterator trySplit() {
841 :     long i = index, m = (i + fence) >>> 1;
842 :     return (m <= i) ? null :
843 :     new RandomIntsSpliterator(rng.split(), i, index = m, origin, bound);
844 :     }
845 :    
846 :     public long estimateSize() {
847 :     return fence - index;
848 :     }
849 :    
850 :     public int characteristics() {
851 :     return (Spliterator.SIZED | Spliterator.SUBSIZED |
852 : dl 1.4 Spliterator.NONNULL | Spliterator.IMMUTABLE);
853 : dl 1.1 }
854 :    
855 :     public boolean tryAdvance(IntConsumer consumer) {
856 :     if (consumer == null) throw new NullPointerException();
857 :     long i = index, f = fence;
858 :     if (i < f) {
859 :     consumer.accept(rng.internalNextInt(origin, bound));
860 :     index = i + 1;
861 :     return true;
862 :     }
863 :     return false;
864 :     }
865 :    
866 :     public void forEachRemaining(IntConsumer consumer) {
867 :     if (consumer == null) throw new NullPointerException();
868 :     long i = index, f = fence;
869 :     if (i < f) {
870 :     index = f;
871 : dl 1.15 SplittableRandom r = rng;
872 : dl 1.1 int o = origin, b = bound;
873 :     do {
874 : dl 1.15 consumer.accept(r.internalNextInt(o, b));
875 : dl 1.1 } while (++i < f);
876 :     }
877 :     }
878 :     }
879 :    
880 :     /**
881 :     * Spliterator for long streams.
882 :     */
883 : dl 1.11 static final class RandomLongsSpliterator implements Spliterator.OfLong {
884 : dl 1.1 final SplittableRandom rng;
885 :     long index;
886 :     final long fence;
887 :     final long origin;
888 :     final long bound;
889 :     RandomLongsSpliterator(SplittableRandom rng, long index, long fence,
890 :     long origin, long bound) {
891 :     this.rng = rng; this.index = index; this.fence = fence;
892 :     this.origin = origin; this.bound = bound;
893 :     }
894 :    
895 :     public RandomLongsSpliterator trySplit() {
896 :     long i = index, m = (i + fence) >>> 1;
897 :     return (m <= i) ? null :
898 :     new RandomLongsSpliterator(rng.split(), i, index = m, origin, bound);
899 :     }
900 :    
901 :     public long estimateSize() {
902 :     return fence - index;
903 :     }
904 :    
905 :     public int characteristics() {
906 :     return (Spliterator.SIZED | Spliterator.SUBSIZED |
907 : dl 1.4 Spliterator.NONNULL | Spliterator.IMMUTABLE);
908 : dl 1.1 }
909 :    
910 :     public boolean tryAdvance(LongConsumer consumer) {
911 :     if (consumer == null) throw new NullPointerException();
912 :     long i = index, f = fence;
913 :     if (i < f) {
914 :     consumer.accept(rng.internalNextLong(origin, bound));
915 :     index = i + 1;
916 :     return true;
917 :     }
918 :     return false;
919 :     }
920 :    
921 :     public void forEachRemaining(LongConsumer consumer) {
922 :     if (consumer == null) throw new NullPointerException();
923 :     long i = index, f = fence;
924 :     if (i < f) {
925 :     index = f;
926 : dl 1.15 SplittableRandom r = rng;
927 : dl 1.1 long o = origin, b = bound;
928 :     do {
929 : dl 1.15 consumer.accept(r.internalNextLong(o, b));
930 : dl 1.1 } while (++i < f);
931 :     }
932 :     }
933 :    
934 :     }
935 :    
936 :     /**
937 :     * Spliterator for double streams.
938 :     */
939 : dl 1.11 static final class RandomDoublesSpliterator implements Spliterator.OfDouble {
940 : dl 1.1 final SplittableRandom rng;
941 :     long index;
942 :     final long fence;
943 :     final double origin;
944 :     final double bound;
945 :     RandomDoublesSpliterator(SplittableRandom rng, long index, long fence,
946 :     double origin, double bound) {
947 :     this.rng = rng; this.index = index; this.fence = fence;
948 :     this.origin = origin; this.bound = bound;
949 :     }
950 :    
951 :     public RandomDoublesSpliterator trySplit() {
952 :     long i = index, m = (i + fence) >>> 1;
953 :     return (m <= i) ? null :
954 :     new RandomDoublesSpliterator(rng.split(), i, index = m, origin, bound);
955 :     }
956 :    
957 :     public long estimateSize() {
958 :     return fence - index;
959 :     }
960 :    
961 :     public int characteristics() {
962 :     return (Spliterator.SIZED | Spliterator.SUBSIZED |
963 : dl 1.4 Spliterator.NONNULL | Spliterator.IMMUTABLE);
964 : dl 1.1 }
965 :    
966 :     public boolean tryAdvance(DoubleConsumer consumer) {
967 :     if (consumer == null) throw new NullPointerException();
968 :     long i = index, f = fence;
969 :     if (i < f) {
970 :     consumer.accept(rng.internalNextDouble(origin, bound));
971 :     index = i + 1;
972 :     return true;
973 :     }
974 :     return false;
975 :     }
976 :    
977 :     public void forEachRemaining(DoubleConsumer consumer) {
978 :     if (consumer == null) throw new NullPointerException();
979 :     long i = index, f = fence;
980 :     if (i < f) {
981 :     index = f;
982 : dl 1.15 SplittableRandom r = rng;
983 : dl 1.1 double o = origin, b = bound;
984 :     do {
985 : dl 1.15 consumer.accept(r.internalNextDouble(o, b));
986 : dl 1.1 } while (++i < f);
987 :     }
988 :     }
989 :     }
990 :    
991 :     }

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