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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 : jsr166 1.26 import java.util.function.DoubleConsumer;
30 : dl 1.1 import java.util.function.IntConsumer;
31 :     import java.util.function.LongConsumer;
32 : jsr166 1.26 import java.util.stream.DoubleStream;
33 : dl 1.1 import java.util.stream.IntStream;
34 :     import java.util.stream.LongStream;
35 : jsr166 1.26 import java.util.stream.StreamSupport;
36 : dl 1.1
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 : jsr166 1.27 * least 2<sup>64</sup>.
56 : dl 1.1 *
57 : jsr166 1.27 * <li>Method {@link #split} constructs and returns a new
58 : dl 1.1 * 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 : jsr166 1.27 * SplittableRandom} object.
64 : dl 1.1 *
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 : jsr166 1.27 * stream.parallel()} mode.
75 : dl 1.1 *
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 : jsr166 1.31 if (java.security.AccessController.doPrivileged(
229 :     new java.security.PrivilegedAction<Boolean>() {
230 :     public Boolean run() {
231 :     return Boolean.getBoolean("java.util.secureRandomSeed");
232 :     }})) {
233 : dl 1.21 byte[] seedBytes = java.security.SecureRandom.getSeed(8);
234 : jsr166 1.30 long s = (long)seedBytes[0] & 0xffL;
235 : dl 1.21 for (int i = 1; i < 8; ++i)
236 : jsr166 1.30 s = (s << 8) | ((long)seedBytes[i] & 0xffL);
237 : dl 1.21 return s;
238 : dl 1.18 }
239 : dl 1.25 return (mix64(System.currentTimeMillis()) ^
240 : dl 1.18 mix64(System.nanoTime()));
241 : dl 1.1 }
242 :    
243 : dl 1.15 // IllegalArgumentException messages
244 : jsr166 1.28 static final String BAD_BOUND = "bound must be positive";
245 :     static final String BAD_RANGE = "bound must be greater than origin";
246 :     static final String BAD_SIZE = "size must be non-negative";
247 : dl 1.12
248 : dl 1.1 /*
249 :     * Internal versions of nextX methods used by streams, as well as
250 :     * the public nextX(origin, bound) methods. These exist mainly to
251 :     * avoid the need for multiple versions of stream spliterators
252 :     * across the different exported forms of streams.
253 :     */
254 :    
255 :     /**
256 :     * The form of nextLong used by LongStream Spliterators. If
257 :     * origin is greater than bound, acts as unbounded form of
258 :     * nextLong, else as bounded form.
259 :     *
260 :     * @param origin the least value, unless greater than bound
261 :     * @param bound the upper bound (exclusive), must not equal origin
262 :     * @return a pseudorandom value
263 :     */
264 :     final long internalNextLong(long origin, long bound) {
265 :     /*
266 :     * Four Cases:
267 :     *
268 :     * 1. If the arguments indicate unbounded form, act as
269 :     * nextLong().
270 :     *
271 :     * 2. If the range is an exact power of two, apply the
272 :     * associated bit mask.
273 :     *
274 :     * 3. If the range is positive, loop to avoid potential bias
275 :     * when the implicit nextLong() bound (2<sup>64</sup>) is not
276 :     * evenly divisible by the range. The loop rejects candidates
277 :     * computed from otherwise over-represented values. The
278 :     * expected number of iterations under an ideal generator
279 : dl 1.4 * varies from 1 to 2, depending on the bound. The loop itself
280 :     * takes an unlovable form. Because the first candidate is
281 :     * already available, we need a break-in-the-middle
282 :     * construction, which is concisely but cryptically performed
283 :     * within the while-condition of a body-less for loop.
284 : dl 1.1 *
285 :     * 4. Otherwise, the range cannot be represented as a positive
286 : dl 1.4 * long. The loop repeatedly generates unbounded longs until
287 :     * obtaining a candidate meeting constraints (with an expected
288 :     * number of iterations of less than two).
289 : dl 1.1 */
290 :    
291 :     long r = mix64(nextSeed());
292 :     if (origin < bound) {
293 :     long n = bound - origin, m = n - 1;
294 : dl 1.7 if ((n & m) == 0L) // power of two
295 : dl 1.1 r = (r & m) + origin;
296 : dl 1.7 else if (n > 0L) { // reject over-represented candidates
297 : dl 1.1 for (long u = r >>> 1; // ensure nonnegative
298 : dl 1.7 u + m - (r = u % n) < 0L; // rejection check
299 : dl 1.1 u = mix64(nextSeed()) >>> 1) // retry
300 :     ;
301 :     r += origin;
302 :     }
303 : dl 1.7 else { // range not representable as long
304 : dl 1.1 while (r < origin || r >= bound)
305 :     r = mix64(nextSeed());
306 :     }
307 :     }
308 :     return r;
309 :     }
310 :    
311 :     /**
312 :     * The form of nextInt used by IntStream Spliterators.
313 :     * Exactly the same as long version, except for types.
314 :     *
315 :     * @param origin the least value, unless greater than bound
316 :     * @param bound the upper bound (exclusive), must not equal origin
317 :     * @return a pseudorandom value
318 :     */
319 :     final int internalNextInt(int origin, int bound) {
320 :     int r = mix32(nextSeed());
321 :     if (origin < bound) {
322 :     int n = bound - origin, m = n - 1;
323 : dl 1.13 if ((n & m) == 0)
324 : dl 1.1 r = (r & m) + origin;
325 :     else if (n > 0) {
326 :     for (int u = r >>> 1;
327 : dl 1.7 u + m - (r = u % n) < 0;
328 : dl 1.1 u = mix32(nextSeed()) >>> 1)
329 :     ;
330 :     r += origin;
331 :     }
332 :     else {
333 :     while (r < origin || r >= bound)
334 :     r = mix32(nextSeed());
335 :     }
336 :     }
337 :     return r;
338 :     }
339 :    
340 :     /**
341 :     * The form of nextDouble used by DoubleStream Spliterators.
342 :     *
343 :     * @param origin the least value, unless greater than bound
344 :     * @param bound the upper bound (exclusive), must not equal origin
345 :     * @return a pseudorandom value
346 :     */
347 :     final double internalNextDouble(double origin, double bound) {
348 : dl 1.24 double r = (nextLong() >>> 11) * DOUBLE_UNIT;
349 : dl 1.1 if (origin < bound) {
350 :     r = r * (bound - origin) + origin;
351 : dl 1.7 if (r >= bound) // correct for rounding
352 : dl 1.1 r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
353 :     }
354 :     return r;
355 :     }
356 :    
357 :     /* ---------------- public methods ---------------- */
358 :    
359 :     /**
360 : dl 1.7 * Creates a new SplittableRandom instance using the specified
361 :     * initial seed. SplittableRandom instances created with the same
362 : dl 1.11 * seed in the same program generate identical sequences of values.
363 : dl 1.1 *
364 :     * @param seed the initial seed
365 :     */
366 :     public SplittableRandom(long seed) {
367 : dl 1.21 this(seed, GOLDEN_GAMMA);
368 : dl 1.1 }
369 :    
370 :     /**
371 :     * Creates a new SplittableRandom instance that is likely to
372 :     * generate sequences of values that are statistically independent
373 :     * of those of any other instances in the current program; and
374 :     * may, and typically does, vary across program invocations.
375 :     */
376 : dl 1.21 public SplittableRandom() { // emulate defaultGen.split()
377 : dl 1.23 long s = defaultGen.getAndAdd(2 * GOLDEN_GAMMA);
378 : dl 1.21 this.seed = mix64(s);
379 :     this.gamma = mixGamma(s + GOLDEN_GAMMA);
380 : dl 1.1 }
381 :    
382 :     /**
383 :     * Constructs and returns a new SplittableRandom instance that
384 :     * shares no mutable state with this instance. However, with very
385 :     * high probability, the set of values collectively generated by
386 :     * the two objects has the same statistical properties as if the
387 :     * same quantity of values were generated by a single thread using
388 :     * a single SplittableRandom object. Either or both of the two
389 :     * objects may be further split using the {@code split()} method,
390 :     * and the same expected statistical properties apply to the
391 :     * entire set of generators constructed by such recursive
392 :     * splitting.
393 :     *
394 :     * @return the new SplittableRandom instance
395 :     */
396 :     public SplittableRandom split() {
397 : dl 1.21 return new SplittableRandom(nextLong(), mixGamma(nextSeed()));
398 : dl 1.1 }
399 :    
400 :     /**
401 :     * Returns a pseudorandom {@code int} value.
402 :     *
403 : dl 1.7 * @return a pseudorandom {@code int} value
404 : dl 1.1 */
405 :     public int nextInt() {
406 :     return mix32(nextSeed());
407 :     }
408 :    
409 :     /**
410 : dl 1.7 * Returns a pseudorandom {@code int} value between zero (inclusive)
411 : dl 1.1 * and the specified bound (exclusive).
412 :     *
413 : dl 1.18 * @param bound the upper bound (exclusive). Must be positive.
414 : dl 1.7 * @return a pseudorandom {@code int} value between zero
415 : jsr166 1.10 * (inclusive) and the bound (exclusive)
416 : dl 1.16 * @throws IllegalArgumentException if {@code bound} is not positive
417 : dl 1.1 */
418 :     public int nextInt(int bound) {
419 :     if (bound <= 0)
420 : jsr166 1.28 throw new IllegalArgumentException(BAD_BOUND);
421 : dl 1.1 // Specialize internalNextInt for origin 0
422 :     int r = mix32(nextSeed());
423 :     int m = bound - 1;
424 : dl 1.13 if ((bound & m) == 0) // power of two
425 : dl 1.1 r &= m;
426 :     else { // reject over-represented candidates
427 :     for (int u = r >>> 1;
428 : dl 1.7 u + m - (r = u % bound) < 0;
429 : dl 1.1 u = mix32(nextSeed()) >>> 1)
430 :     ;
431 :     }
432 :     return r;
433 :     }
434 :    
435 :     /**
436 :     * Returns a pseudorandom {@code int} value between the specified
437 :     * origin (inclusive) and the specified bound (exclusive).
438 :     *
439 :     * @param origin the least value returned
440 :     * @param bound the upper bound (exclusive)
441 :     * @return a pseudorandom {@code int} value between the origin
442 : jsr166 1.10 * (inclusive) and the bound (exclusive)
443 : dl 1.7 * @throws IllegalArgumentException if {@code origin} is greater than
444 : dl 1.1 * or equal to {@code bound}
445 :     */
446 :     public int nextInt(int origin, int bound) {
447 :     if (origin >= bound)
448 : jsr166 1.28 throw new IllegalArgumentException(BAD_RANGE);
449 : dl 1.1 return internalNextInt(origin, bound);
450 :     }
451 :    
452 :     /**
453 :     * Returns a pseudorandom {@code long} value.
454 :     *
455 : dl 1.7 * @return a pseudorandom {@code long} value
456 : dl 1.1 */
457 :     public long nextLong() {
458 :     return mix64(nextSeed());
459 :     }
460 :    
461 :     /**
462 : dl 1.7 * Returns a pseudorandom {@code long} value between zero (inclusive)
463 : dl 1.1 * and the specified bound (exclusive).
464 :     *
465 : dl 1.18 * @param bound the upper bound (exclusive). Must be positive.
466 : dl 1.7 * @return a pseudorandom {@code long} value between zero
467 : jsr166 1.10 * (inclusive) and the bound (exclusive)
468 : dl 1.16 * @throws IllegalArgumentException if {@code bound} is not positive
469 : dl 1.1 */
470 :     public long nextLong(long bound) {
471 :     if (bound <= 0)
472 : jsr166 1.28 throw new IllegalArgumentException(BAD_BOUND);
473 : dl 1.1 // Specialize internalNextLong for origin 0
474 :     long r = mix64(nextSeed());
475 :     long m = bound - 1;
476 :     if ((bound & m) == 0L) // power of two
477 :     r &= m;
478 :     else { // reject over-represented candidates
479 :     for (long u = r >>> 1;
480 :     u + m - (r = u % bound) < 0L;
481 :     u = mix64(nextSeed()) >>> 1)
482 :     ;
483 :     }
484 :     return r;
485 :     }
486 :    
487 :     /**
488 :     * Returns a pseudorandom {@code long} value between the specified
489 :     * origin (inclusive) and the specified bound (exclusive).
490 :     *
491 :     * @param origin the least value returned
492 :     * @param bound the upper bound (exclusive)
493 :     * @return a pseudorandom {@code long} value between the origin
494 : jsr166 1.10 * (inclusive) and the bound (exclusive)
495 : dl 1.7 * @throws IllegalArgumentException if {@code origin} is greater than
496 : dl 1.1 * or equal to {@code bound}
497 :     */
498 :     public long nextLong(long origin, long bound) {
499 :     if (origin >= bound)
500 : jsr166 1.28 throw new IllegalArgumentException(BAD_RANGE);
501 : dl 1.1 return internalNextLong(origin, bound);
502 :     }
503 :    
504 :     /**
505 : dl 1.7 * Returns a pseudorandom {@code double} value between zero
506 :     * (inclusive) and one (exclusive).
507 : dl 1.1 *
508 : dl 1.7 * @return a pseudorandom {@code double} value between zero
509 : dl 1.18 * (inclusive) and one (exclusive)
510 : dl 1.1 */
511 :     public double nextDouble() {
512 : dl 1.24 return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT;
513 : dl 1.1 }
514 :    
515 :     /**
516 :     * Returns a pseudorandom {@code double} value between 0.0
517 :     * (inclusive) and the specified bound (exclusive).
518 :     *
519 : dl 1.18 * @param bound the upper bound (exclusive). Must be positive.
520 : dl 1.7 * @return a pseudorandom {@code double} value between zero
521 : jsr166 1.10 * (inclusive) and the bound (exclusive)
522 : dl 1.16 * @throws IllegalArgumentException if {@code bound} is not positive
523 : dl 1.1 */
524 :     public double nextDouble(double bound) {
525 : dl 1.7 if (!(bound > 0.0))
526 : jsr166 1.28 throw new IllegalArgumentException(BAD_BOUND);
527 : dl 1.24 double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound;
528 : dl 1.1 return (result < bound) ? result : // correct for rounding
529 :     Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
530 :     }
531 :    
532 :     /**
533 : dl 1.7 * Returns a pseudorandom {@code double} value between the specified
534 : dl 1.1 * origin (inclusive) and bound (exclusive).
535 :     *
536 :     * @param origin the least value returned
537 : dl 1.18 * @param bound the upper bound (exclusive)
538 : dl 1.1 * @return a pseudorandom {@code double} value between the origin
539 : jsr166 1.10 * (inclusive) and the bound (exclusive)
540 : dl 1.1 * @throws IllegalArgumentException if {@code origin} is greater than
541 :     * or equal to {@code bound}
542 :     */
543 :     public double nextDouble(double origin, double bound) {
544 : dl 1.7 if (!(origin < bound))
545 : jsr166 1.28 throw new IllegalArgumentException(BAD_RANGE);
546 : dl 1.1 return internalNextDouble(origin, bound);
547 :     }
548 :    
549 : dl 1.11 /**
550 :     * Returns a pseudorandom {@code boolean} value.
551 :     *
552 :     * @return a pseudorandom {@code boolean} value
553 :     */
554 :     public boolean nextBoolean() {
555 :     return mix32(nextSeed()) < 0;
556 :     }
557 :    
558 : dl 1.1 // stream methods, coded in a way intended to better isolate for
559 :     // maintenance purposes the small differences across forms.
560 :    
561 :     /**
562 : dl 1.16 * Returns a stream producing the given {@code streamSize} number
563 :     * of pseudorandom {@code int} values from this generator and/or
564 :     * one split from it.
565 : dl 1.1 *
566 :     * @param streamSize the number of values to generate
567 :     * @return a stream of pseudorandom {@code int} values
568 :     * @throws IllegalArgumentException if {@code streamSize} is
569 : dl 1.7 * less than zero
570 : dl 1.1 */
571 :     public IntStream ints(long streamSize) {
572 :     if (streamSize < 0L)
573 : jsr166 1.28 throw new IllegalArgumentException(BAD_SIZE);
574 : dl 1.1 return StreamSupport.intStream
575 :     (new RandomIntsSpliterator
576 :     (this, 0L, streamSize, Integer.MAX_VALUE, 0),
577 :     false);
578 :     }
579 :    
580 :     /**
581 :     * Returns an effectively unlimited stream of pseudorandom {@code int}
582 : dl 1.16 * values from this generator and/or one split from it.
583 : dl 1.1 *
584 :     * @implNote This method is implemented to be equivalent to {@code
585 :     * ints(Long.MAX_VALUE)}.
586 :     *
587 :     * @return a stream of pseudorandom {@code int} values
588 :     */
589 :     public IntStream ints() {
590 :     return StreamSupport.intStream
591 :     (new RandomIntsSpliterator
592 :     (this, 0L, Long.MAX_VALUE, Integer.MAX_VALUE, 0),
593 :     false);
594 :     }
595 :    
596 :     /**
597 : dl 1.16 * Returns a stream producing the given {@code streamSize} number
598 : dl 1.18 * of pseudorandom {@code int} values from this generator and/or one split
599 :     * from it; each value conforms to the given origin (inclusive) and bound
600 :     * (exclusive).
601 : dl 1.1 *
602 :     * @param streamSize the number of values to generate
603 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
604 :     * @param randomNumberBound the bound (exclusive) of each random value
605 : dl 1.1 * @return a stream of pseudorandom {@code int} values,
606 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
607 : dl 1.1 * @throws IllegalArgumentException if {@code streamSize} is
608 : dl 1.7 * less than zero, or {@code randomNumberOrigin}
609 : dl 1.1 * is greater than or equal to {@code randomNumberBound}
610 :     */
611 :     public IntStream ints(long streamSize, int randomNumberOrigin,
612 :     int randomNumberBound) {
613 :     if (streamSize < 0L)
614 : jsr166 1.28 throw new IllegalArgumentException(BAD_SIZE);
615 : dl 1.1 if (randomNumberOrigin >= randomNumberBound)
616 : jsr166 1.28 throw new IllegalArgumentException(BAD_RANGE);
617 : dl 1.1 return StreamSupport.intStream
618 :     (new RandomIntsSpliterator
619 :     (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
620 :     false);
621 :     }
622 :    
623 :     /**
624 :     * Returns an effectively unlimited stream of pseudorandom {@code
625 : dl 1.18 * int} values from this generator and/or one split from it; each value
626 :     * conforms to the given origin (inclusive) and bound (exclusive).
627 : dl 1.1 *
628 :     * @implNote This method is implemented to be equivalent to {@code
629 :     * ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
630 :     *
631 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
632 :     * @param randomNumberBound the bound (exclusive) of each random value
633 : dl 1.1 * @return a stream of pseudorandom {@code int} values,
634 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
635 : dl 1.1 * @throws IllegalArgumentException if {@code randomNumberOrigin}
636 :     * is greater than or equal to {@code randomNumberBound}
637 :     */
638 :     public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
639 :     if (randomNumberOrigin >= randomNumberBound)
640 : jsr166 1.28 throw new IllegalArgumentException(BAD_RANGE);
641 : dl 1.1 return StreamSupport.intStream
642 :     (new RandomIntsSpliterator
643 :     (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
644 :     false);
645 :     }
646 :    
647 :     /**
648 : dl 1.16 * Returns a stream producing the given {@code streamSize} number
649 :     * of pseudorandom {@code long} values from this generator and/or
650 :     * one split from it.
651 : dl 1.1 *
652 :     * @param streamSize the number of values to generate
653 : dl 1.7 * @return a stream of pseudorandom {@code long} values
654 : dl 1.1 * @throws IllegalArgumentException if {@code streamSize} is
655 : dl 1.7 * less than zero
656 : dl 1.1 */
657 :     public LongStream longs(long streamSize) {
658 :     if (streamSize < 0L)
659 : jsr166 1.28 throw new IllegalArgumentException(BAD_SIZE);
660 : dl 1.1 return StreamSupport.longStream
661 :     (new RandomLongsSpliterator
662 :     (this, 0L, streamSize, Long.MAX_VALUE, 0L),
663 :     false);
664 :     }
665 :    
666 :     /**
667 : dl 1.16 * Returns an effectively unlimited stream of pseudorandom {@code
668 :     * long} values from this generator and/or one split from it.
669 : dl 1.1 *
670 :     * @implNote This method is implemented to be equivalent to {@code
671 :     * longs(Long.MAX_VALUE)}.
672 :     *
673 :     * @return a stream of pseudorandom {@code long} values
674 :     */
675 :     public LongStream longs() {
676 :     return StreamSupport.longStream
677 :     (new RandomLongsSpliterator
678 :     (this, 0L, Long.MAX_VALUE, Long.MAX_VALUE, 0L),
679 :     false);
680 :     }
681 :    
682 :     /**
683 : dl 1.7 * Returns a stream producing the given {@code streamSize} number of
684 : dl 1.18 * pseudorandom {@code long} values from this generator and/or one split
685 :     * from it; each value conforms to the given origin (inclusive) and bound
686 :     * (exclusive).
687 : dl 1.1 *
688 :     * @param streamSize the number of values to generate
689 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
690 :     * @param randomNumberBound the bound (exclusive) of each random value
691 : dl 1.1 * @return a stream of pseudorandom {@code long} values,
692 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
693 : dl 1.1 * @throws IllegalArgumentException if {@code streamSize} is
694 : dl 1.7 * less than zero, or {@code randomNumberOrigin}
695 : dl 1.1 * is greater than or equal to {@code randomNumberBound}
696 :     */
697 :     public LongStream longs(long streamSize, long randomNumberOrigin,
698 :     long randomNumberBound) {
699 :     if (streamSize < 0L)
700 : jsr166 1.28 throw new IllegalArgumentException(BAD_SIZE);
701 : dl 1.1 if (randomNumberOrigin >= randomNumberBound)
702 : jsr166 1.28 throw new IllegalArgumentException(BAD_RANGE);
703 : dl 1.1 return StreamSupport.longStream
704 :     (new RandomLongsSpliterator
705 :     (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
706 :     false);
707 :     }
708 :    
709 :     /**
710 :     * Returns an effectively unlimited stream of pseudorandom {@code
711 : dl 1.18 * long} values from this generator and/or one split from it; each value
712 :     * conforms to the given origin (inclusive) and bound (exclusive).
713 : dl 1.1 *
714 :     * @implNote This method is implemented to be equivalent to {@code
715 :     * longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
716 :     *
717 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
718 :     * @param randomNumberBound the bound (exclusive) of each random value
719 : dl 1.1 * @return a stream of pseudorandom {@code long} values,
720 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
721 : dl 1.1 * @throws IllegalArgumentException if {@code randomNumberOrigin}
722 :     * is greater than or equal to {@code randomNumberBound}
723 :     */
724 :     public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
725 :     if (randomNumberOrigin >= randomNumberBound)
726 : jsr166 1.28 throw new IllegalArgumentException(BAD_RANGE);
727 : dl 1.1 return StreamSupport.longStream
728 :     (new RandomLongsSpliterator
729 :     (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
730 :     false);
731 :     }
732 :    
733 :     /**
734 : dl 1.7 * Returns a stream producing the given {@code streamSize} number of
735 : dl 1.18 * pseudorandom {@code double} values from this generator and/or one split
736 :     * from it; each value is between zero (inclusive) and one (exclusive).
737 : dl 1.1 *
738 :     * @param streamSize the number of values to generate
739 :     * @return a stream of {@code double} values
740 :     * @throws IllegalArgumentException if {@code streamSize} is
741 : dl 1.7 * less than zero
742 : dl 1.1 */
743 :     public DoubleStream doubles(long streamSize) {
744 :     if (streamSize < 0L)
745 : jsr166 1.28 throw new IllegalArgumentException(BAD_SIZE);
746 : dl 1.1 return StreamSupport.doubleStream
747 :     (new RandomDoublesSpliterator
748 :     (this, 0L, streamSize, Double.MAX_VALUE, 0.0),
749 :     false);
750 :     }
751 :    
752 :     /**
753 :     * Returns an effectively unlimited stream of pseudorandom {@code
754 : dl 1.18 * double} values from this generator and/or one split from it; each value
755 :     * is between zero (inclusive) and one (exclusive).
756 : dl 1.1 *
757 :     * @implNote This method is implemented to be equivalent to {@code
758 :     * doubles(Long.MAX_VALUE)}.
759 :     *
760 :     * @return a stream of pseudorandom {@code double} values
761 :     */
762 :     public DoubleStream doubles() {
763 :     return StreamSupport.doubleStream
764 :     (new RandomDoublesSpliterator
765 :     (this, 0L, Long.MAX_VALUE, Double.MAX_VALUE, 0.0),
766 :     false);
767 :     }
768 :    
769 :     /**
770 : dl 1.7 * Returns a stream producing the given {@code streamSize} number of
771 : dl 1.18 * pseudorandom {@code double} values from this generator and/or one split
772 :     * from it; each value conforms to the given origin (inclusive) and bound
773 :     * (exclusive).
774 : dl 1.1 *
775 :     * @param streamSize the number of values to generate
776 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
777 :     * @param randomNumberBound the bound (exclusive) of each random value
778 : dl 1.1 * @return a stream of pseudorandom {@code double} values,
779 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
780 : dl 1.1 * @throws IllegalArgumentException if {@code streamSize} is
781 : dl 1.18 * less than zero
782 : dl 1.1 * @throws IllegalArgumentException if {@code randomNumberOrigin}
783 :     * is greater than or equal to {@code randomNumberBound}
784 :     */
785 :     public DoubleStream doubles(long streamSize, double randomNumberOrigin,
786 :     double randomNumberBound) {
787 :     if (streamSize < 0L)
788 : jsr166 1.28 throw new IllegalArgumentException(BAD_SIZE);
789 : dl 1.7 if (!(randomNumberOrigin < randomNumberBound))
790 : jsr166 1.28 throw new IllegalArgumentException(BAD_RANGE);
791 : dl 1.1 return StreamSupport.doubleStream
792 :     (new RandomDoublesSpliterator
793 :     (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
794 :     false);
795 :     }
796 :    
797 :     /**
798 :     * Returns an effectively unlimited stream of pseudorandom {@code
799 : dl 1.18 * double} values from this generator and/or one split from it; each value
800 :     * conforms to the given origin (inclusive) and bound (exclusive).
801 : dl 1.1 *
802 :     * @implNote This method is implemented to be equivalent to {@code
803 :     * doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
804 :     *
805 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
806 :     * @param randomNumberBound the bound (exclusive) of each random value
807 : dl 1.1 * @return a stream of pseudorandom {@code double} values,
808 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
809 : dl 1.1 * @throws IllegalArgumentException if {@code randomNumberOrigin}
810 :     * is greater than or equal to {@code randomNumberBound}
811 :     */
812 :     public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
813 : dl 1.7 if (!(randomNumberOrigin < randomNumberBound))
814 : jsr166 1.28 throw new IllegalArgumentException(BAD_RANGE);
815 : dl 1.1 return StreamSupport.doubleStream
816 :     (new RandomDoublesSpliterator
817 :     (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
818 :     false);
819 :     }
820 :    
821 :     /**
822 :     * Spliterator for int streams. We multiplex the four int
823 : dl 1.7 * versions into one class by treating a bound less than origin as
824 : dl 1.1 * unbounded, and also by treating "infinite" as equivalent to
825 :     * Long.MAX_VALUE. For splits, it uses the standard divide-by-two
826 :     * approach. The long and double versions of this class are
827 :     * identical except for types.
828 :     */
829 : jsr166 1.29 private static final class RandomIntsSpliterator
830 :     implements Spliterator.OfInt {
831 : dl 1.1 final SplittableRandom rng;
832 :     long index;
833 :     final long fence;
834 :     final int origin;
835 :     final int bound;
836 :     RandomIntsSpliterator(SplittableRandom rng, long index, long fence,
837 :     int origin, int bound) {
838 :     this.rng = rng; this.index = index; this.fence = fence;
839 :     this.origin = origin; this.bound = bound;
840 :     }
841 :    
842 :     public RandomIntsSpliterator trySplit() {
843 :     long i = index, m = (i + fence) >>> 1;
844 :     return (m <= i) ? null :
845 :     new RandomIntsSpliterator(rng.split(), i, index = m, origin, bound);
846 :     }
847 :    
848 :     public long estimateSize() {
849 :     return fence - index;
850 :     }
851 :    
852 :     public int characteristics() {
853 :     return (Spliterator.SIZED | Spliterator.SUBSIZED |
854 : dl 1.4 Spliterator.NONNULL | Spliterator.IMMUTABLE);
855 : dl 1.1 }
856 :    
857 :     public boolean tryAdvance(IntConsumer consumer) {
858 :     if (consumer == null) throw new NullPointerException();
859 :     long i = index, f = fence;
860 :     if (i < f) {
861 :     consumer.accept(rng.internalNextInt(origin, bound));
862 :     index = i + 1;
863 :     return true;
864 :     }
865 :     return false;
866 :     }
867 :    
868 :     public void forEachRemaining(IntConsumer consumer) {
869 :     if (consumer == null) throw new NullPointerException();
870 :     long i = index, f = fence;
871 :     if (i < f) {
872 :     index = f;
873 : dl 1.15 SplittableRandom r = rng;
874 : dl 1.1 int o = origin, b = bound;
875 :     do {
876 : dl 1.15 consumer.accept(r.internalNextInt(o, b));
877 : dl 1.1 } while (++i < f);
878 :     }
879 :     }
880 :     }
881 :    
882 :     /**
883 :     * Spliterator for long streams.
884 :     */
885 : jsr166 1.29 private static final class RandomLongsSpliterator
886 :     implements Spliterator.OfLong {
887 : dl 1.1 final SplittableRandom rng;
888 :     long index;
889 :     final long fence;
890 :     final long origin;
891 :     final long bound;
892 :     RandomLongsSpliterator(SplittableRandom rng, long index, long fence,
893 :     long origin, long bound) {
894 :     this.rng = rng; this.index = index; this.fence = fence;
895 :     this.origin = origin; this.bound = bound;
896 :     }
897 :    
898 :     public RandomLongsSpliterator trySplit() {
899 :     long i = index, m = (i + fence) >>> 1;
900 :     return (m <= i) ? null :
901 :     new RandomLongsSpliterator(rng.split(), i, index = m, origin, bound);
902 :     }
903 :    
904 :     public long estimateSize() {
905 :     return fence - index;
906 :     }
907 :    
908 :     public int characteristics() {
909 :     return (Spliterator.SIZED | Spliterator.SUBSIZED |
910 : dl 1.4 Spliterator.NONNULL | Spliterator.IMMUTABLE);
911 : dl 1.1 }
912 :    
913 :     public boolean tryAdvance(LongConsumer consumer) {
914 :     if (consumer == null) throw new NullPointerException();
915 :     long i = index, f = fence;
916 :     if (i < f) {
917 :     consumer.accept(rng.internalNextLong(origin, bound));
918 :     index = i + 1;
919 :     return true;
920 :     }
921 :     return false;
922 :     }
923 :    
924 :     public void forEachRemaining(LongConsumer consumer) {
925 :     if (consumer == null) throw new NullPointerException();
926 :     long i = index, f = fence;
927 :     if (i < f) {
928 :     index = f;
929 : dl 1.15 SplittableRandom r = rng;
930 : dl 1.1 long o = origin, b = bound;
931 :     do {
932 : dl 1.15 consumer.accept(r.internalNextLong(o, b));
933 : dl 1.1 } while (++i < f);
934 :     }
935 :     }
936 :    
937 :     }
938 :    
939 :     /**
940 :     * Spliterator for double streams.
941 :     */
942 : jsr166 1.29 private static final class RandomDoublesSpliterator
943 :     implements Spliterator.OfDouble {
944 : dl 1.1 final SplittableRandom rng;
945 :     long index;
946 :     final long fence;
947 :     final double origin;
948 :     final double bound;
949 :     RandomDoublesSpliterator(SplittableRandom rng, long index, long fence,
950 :     double origin, double bound) {
951 :     this.rng = rng; this.index = index; this.fence = fence;
952 :     this.origin = origin; this.bound = bound;
953 :     }
954 :    
955 :     public RandomDoublesSpliterator trySplit() {
956 :     long i = index, m = (i + fence) >>> 1;
957 :     return (m <= i) ? null :
958 :     new RandomDoublesSpliterator(rng.split(), i, index = m, origin, bound);
959 :     }
960 :    
961 :     public long estimateSize() {
962 :     return fence - index;
963 :     }
964 :    
965 :     public int characteristics() {
966 :     return (Spliterator.SIZED | Spliterator.SUBSIZED |
967 : dl 1.4 Spliterator.NONNULL | Spliterator.IMMUTABLE);
968 : dl 1.1 }
969 :    
970 :     public boolean tryAdvance(DoubleConsumer consumer) {
971 :     if (consumer == null) throw new NullPointerException();
972 :     long i = index, f = fence;
973 :     if (i < f) {
974 :     consumer.accept(rng.internalNextDouble(origin, bound));
975 :     index = i + 1;
976 :     return true;
977 :     }
978 :     return false;
979 :     }
980 :    
981 :     public void forEachRemaining(DoubleConsumer consumer) {
982 :     if (consumer == null) throw new NullPointerException();
983 :     long i = index, f = fence;
984 :     if (i < f) {
985 :     index = f;
986 : dl 1.15 SplittableRandom r = rng;
987 : dl 1.1 double o = origin, b = bound;
988 :     do {
989 : dl 1.15 consumer.accept(r.internalNextDouble(o, b));
990 : dl 1.1 } while (++i < f);
991 :     }
992 :     }
993 :     }
994 :    
995 :     }

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