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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 : dl 1.18 import java.security.SecureRandom;
29 : dl 1.15 import java.net.InetAddress;
30 : dl 1.1 import java.util.concurrent.atomic.AtomicLong;
31 :     import java.util.function.IntConsumer;
32 :     import java.util.function.LongConsumer;
33 :     import java.util.function.DoubleConsumer;
34 :     import java.util.stream.StreamSupport;
35 :     import java.util.stream.IntStream;
36 :     import java.util.stream.LongStream;
37 :     import java.util.stream.DoubleStream;
38 :    
39 :     /**
40 :     * A generator of uniform pseudorandom values applicable for use in
41 :     * (among other contexts) isolated parallel computations that may
42 : dl 1.18 * generate subtasks. Class {@code SplittableRandom} supports methods for
43 : jsr166 1.3 * producing pseudorandom numbers of type {@code int}, {@code long},
44 : dl 1.1 * and {@code double} with similar usages as for class
45 : jsr166 1.9 * {@link java.util.Random} but differs in the following ways:
46 :     *
47 :     * <ul>
48 : dl 1.1 *
49 :     * <li>Series of generated values pass the DieHarder suite testing
50 :     * independence and uniformity properties of random number generators.
51 :     * (Most recently validated with <a
52 :     * href="http://www.phy.duke.edu/~rgb/General/dieharder.php"> version
53 :     * 3.31.1</a>.) These tests validate only the methods for certain
54 :     * types and ranges, but similar properties are expected to hold, at
55 : dl 1.11 * least approximately, for others as well. The <em>period</em>
56 :     * (length of any series of generated values before it repeats) is at
57 :     * least 2<sup>64</sup>. </li>
58 : dl 1.1 *
59 :     * <li> Method {@link #split} constructs and returns a new
60 :     * SplittableRandom instance that shares no mutable state with the
61 : dl 1.7 * current instance. However, with very high probability, the
62 :     * values collectively generated by the two objects have the same
63 : dl 1.1 * statistical properties as if the same quantity of values were
64 :     * generated by a single thread using a single {@code
65 :     * SplittableRandom} object. </li>
66 :     *
67 :     * <li>Instances of SplittableRandom are <em>not</em> thread-safe.
68 :     * They are designed to be split, not shared, across threads. For
69 :     * example, a {@link java.util.concurrent.ForkJoinTask
70 :     * fork/join-style} computation using random numbers might include a
71 :     * construction of the form {@code new
72 :     * Subtask(aSplittableRandom.split()).fork()}.
73 :     *
74 :     * <li>This class provides additional methods for generating random
75 :     * streams, that employ the above techniques when used in {@code
76 :     * stream.parallel()} mode.</li>
77 :     *
78 :     * </ul>
79 :     *
80 : dl 1.18 * <p>Instances of {@code SplittableRandom} are not cryptographically
81 :     * secure. Consider instead using {@link java.security.SecureRandom}
82 :     * in security-sensitive applications. Additionally,
83 :     * default-constructed instances do not use a cryptographically random
84 :     * seed unless the {@linkplain System#getProperty system property}
85 :     * {@code java.util.secureRandomSeed} is set to {@code true}.
86 :    
87 :     *
88 : dl 1.1 * @author Guy Steele
89 : dl 1.2 * @author Doug Lea
90 : dl 1.1 * @since 1.8
91 :     */
92 :     public class SplittableRandom {
93 :    
94 :     /*
95 :     * Implementation Overview.
96 :     *
97 :     * This algorithm was inspired by the "DotMix" algorithm by
98 :     * Leiserson, Schardl, and Sukha "Deterministic Parallel
99 :     * Random-Number Generation for Dynamic-Multithreading Platforms",
100 : dl 1.15 * PPoPP 2012, as well as those in "Parallel random numbers: as
101 :     * easy as 1, 2, 3" by Salmon, Morae, Dror, and Shaw, SC 2011. It
102 :     * differs mainly in simplifying and cheapening operations.
103 :     *
104 :     * The primary update step (method nextSeed()) is to add a
105 :     * constant ("gamma") to the current (64 bit) seed, forming a
106 :     * simple sequence. The seed and the gamma values for any two
107 :     * SplittableRandom instances are highly likely to be different.
108 :     *
109 :     * Methods nextLong, nextInt, and derivatives do not return the
110 :     * sequence (seed) values, but instead a hash-like bit-mix of
111 :     * their bits, producing more independently distributed sequences.
112 :     * For nextLong, the mix64 bit-mixing function computes the same
113 :     * value as the "64-bit finalizer" function in Austin Appleby's
114 :     * MurmurHash3 algorithm. See
115 : dl 1.1 * http://code.google.com/p/smhasher/wiki/MurmurHash3 , which
116 :     * comments: "The constants for the finalizers were generated by a
117 :     * simple simulated-annealing algorithm, and both avalanche all
118 : dl 1.15 * bits of 'h' to within 0.25% bias." The mix32 function is
119 :     * equivalent to (int)(mix64(seed) >>> 32), but faster because it
120 :     * omits a step that doesn't contribute to result.
121 :     *
122 :     * The split operation uses the current generator to form the seed
123 :     * and gamma for another SplittableRandom. To conservatively
124 :     * avoid potential correlations between seed and value generation,
125 :     * gamma selection (method nextGamma) uses the "Mix13" constants
126 :     * for MurmurHash3 described by David Stafford
127 :     * (http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html)
128 :     * To avoid potential weaknesses in bit-mixing transformations, we
129 :     * restrict gammas to odd values with at least 12 and no more than
130 :     * 52 bits set. Rather than rejecting candidates with too few or
131 :     * too many bits set, method nextGamma flips some bits (which has
132 :     * the effect of mapping at most 4 to any given gamma value).
133 :     * This reduces the effective set of 64bit odd gamma values by
134 :     * about 2<sup>14</sup>, a very tiny percentage, and serves as an
135 :     * automated screening for sequence constant selection that is
136 :     * left as an empirical decision in some other hashing and crypto
137 :     * algorithms.
138 :     *
139 :     * The resulting generator thus transforms a sequence in which
140 :     * (typically) many bits change on each step, with an inexpensive
141 :     * mixer with good (but less than cryptographically secure)
142 :     * avalanching.
143 :     *
144 :     * The default (no-argument) constructor, in essence, invokes
145 :     * split() for a common "seeder" SplittableRandom. Unlike other
146 :     * cases, this split must be performed in a thread-safe manner, so
147 :     * we use an AtomicLong to represent the seed rather than use an
148 :     * explicit SplittableRandom. To bootstrap the seeder, we start
149 : dl 1.18 * off using a seed based on current time and host unless the
150 :     * SecureRandomSeed property is set. This serves as a
151 :     * slimmed-down (and insecure) variant of SecureRandom that also
152 : dl 1.15 * avoids stalls that may occur when using /dev/random.
153 :     *
154 :     * It is a relatively simple matter to apply the basic design here
155 :     * to use 128 bit seeds. However, emulating 128bit arithmetic and
156 :     * carrying around twice the state add more overhead than appears
157 :     * warranted for current usages.
158 : dl 1.13 *
159 : dl 1.15 * File organization: First the non-public methods that constitute
160 :     * the main algorithm, then the main public methods, followed by
161 :     * some custom spliterator classes needed for stream methods.
162 : dl 1.1 */
163 :    
164 :     /**
165 : dl 1.15 * The initial gamma value for (unsplit) SplittableRandoms. Must
166 :     * be odd with at least 12 and no more than 52 bits set. Currently
167 :     * set to the golden ratio scaled to 64bits.
168 : dl 1.1 */
169 : dl 1.15 private static final long INITIAL_GAMMA = 0x9e3779b97f4a7c15L;
170 : dl 1.11
171 :     /**
172 : dl 1.5 * The least non-zero value returned by nextDouble(). This value
173 : dl 1.7 * is scaled by a random value of 53 bits to produce a result.
174 : dl 1.5 */
175 :     private static final double DOUBLE_UNIT = 1.0 / (1L << 53);
176 :    
177 :     /**
178 : dl 1.15 * The seed. Updated only via method nextSeed.
179 : dl 1.1 */
180 :     private long seed;
181 :    
182 :     /**
183 : dl 1.15 * The step value.
184 : dl 1.1 */
185 :     private final long gamma;
186 :    
187 :     /**
188 : dl 1.15 * Internal constructor used by all others except default constructor.
189 : dl 1.1 */
190 : dl 1.15 private SplittableRandom(long seed, long gamma) {
191 :     this.seed = seed;
192 :     this.gamma = gamma;
193 : dl 1.1 }
194 :    
195 :     /**
196 : dl 1.15 * Computes MurmurHash3 64bit mix function.
197 : dl 1.1 */
198 :     private static long mix64(long z) {
199 : dl 1.15 z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL;
200 :     z = (z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L;
201 :     return z ^ (z >>> 33);
202 : dl 1.1 }
203 :    
204 :     /**
205 : dl 1.15 * Returns the 32 high bits of mix64(z) as int.
206 : dl 1.1 */
207 :     private static int mix32(long z) {
208 : dl 1.15 z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL;
209 :     return (int)(((z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L) >>> 32);
210 : dl 1.1 }
211 :    
212 :     /**
213 : dl 1.15 * Returns the gamma value to use for a new split instance.
214 : dl 1.13 */
215 : dl 1.15 private static long nextGamma(long z) {
216 :     z = (z ^ (z >>> 30)) * 0xbf58476d1ce4e5b9L; // Stafford "Mix13"
217 : dl 1.14 z = (z ^ (z >>> 27)) * 0x94d049bb133111ebL;
218 : dl 1.15 z = (z ^ (z >>> 31)) | 1L; // force to be odd
219 :     int n = Long.bitCount(z); // ensure enough 0 and 1 bits
220 :     return (n < 12 || n > 52) ? z ^ 0xaaaaaaaaaaaaaaaaL : z;
221 : dl 1.13 }
222 :    
223 :     /**
224 : dl 1.15 * Adds gamma to seed.
225 : dl 1.7 */
226 : dl 1.15 private long nextSeed() {
227 :     return seed += gamma;
228 : dl 1.7 }
229 :    
230 :     /**
231 : dl 1.15 * The seed generator for default constructors.
232 : dl 1.7 */
233 : dl 1.18 private static final AtomicLong seeder = new AtomicLong(initialSeed());
234 : dl 1.7
235 : dl 1.18 private static long initialSeed() {
236 :     try { // ignore exceptions in accessing/parsing properties
237 :     String pp = System.getProperty
238 :     ("java.util.secureRandomSeed");
239 :     if (pp != null && pp.equalsIgnoreCase("true")) {
240 :     byte[] seedBytes = java.security.SecureRandom.getSeed(8);
241 :     long s = (long)(seedBytes[0]) & 0xffL;
242 :     for (int i = 1; i < 8; ++i)
243 :     s = (s << 8) | ((long)(seedBytes[i]) & 0xffL);
244 :     return s;
245 :     }
246 :     } catch (Exception ignore) {
247 :     }
248 :     int hh = 0; // hashed host address
249 : jsr166 1.17 try {
250 : dl 1.18 hh = InetAddress.getLocalHost().hashCode();
251 :     } catch (Exception ignore) {
252 : jsr166 1.17 }
253 : dl 1.18 return (mix64((((long)hh) << 32) ^ System.currentTimeMillis()) ^
254 :     mix64(System.nanoTime()));
255 : dl 1.1 }
256 :    
257 : dl 1.15 // IllegalArgumentException messages
258 :     static final String BadBound = "bound must be positive";
259 :     static final String BadRange = "bound must be greater than origin";
260 :     static final String BadSize = "size must be non-negative";
261 : dl 1.12
262 : dl 1.1 /*
263 :     * Internal versions of nextX methods used by streams, as well as
264 :     * the public nextX(origin, bound) methods. These exist mainly to
265 :     * avoid the need for multiple versions of stream spliterators
266 :     * across the different exported forms of streams.
267 :     */
268 :    
269 :     /**
270 :     * The form of nextLong used by LongStream Spliterators. If
271 :     * origin is greater than bound, acts as unbounded form of
272 :     * nextLong, else as bounded form.
273 :     *
274 :     * @param origin the least value, unless greater than bound
275 :     * @param bound the upper bound (exclusive), must not equal origin
276 :     * @return a pseudorandom value
277 :     */
278 :     final long internalNextLong(long origin, long bound) {
279 :     /*
280 :     * Four Cases:
281 :     *
282 :     * 1. If the arguments indicate unbounded form, act as
283 :     * nextLong().
284 :     *
285 :     * 2. If the range is an exact power of two, apply the
286 :     * associated bit mask.
287 :     *
288 :     * 3. If the range is positive, loop to avoid potential bias
289 :     * when the implicit nextLong() bound (2<sup>64</sup>) is not
290 :     * evenly divisible by the range. The loop rejects candidates
291 :     * computed from otherwise over-represented values. The
292 :     * expected number of iterations under an ideal generator
293 : dl 1.4 * varies from 1 to 2, depending on the bound. The loop itself
294 :     * takes an unlovable form. Because the first candidate is
295 :     * already available, we need a break-in-the-middle
296 :     * construction, which is concisely but cryptically performed
297 :     * within the while-condition of a body-less for loop.
298 : dl 1.1 *
299 :     * 4. Otherwise, the range cannot be represented as a positive
300 : dl 1.4 * long. The loop repeatedly generates unbounded longs until
301 :     * obtaining a candidate meeting constraints (with an expected
302 :     * number of iterations of less than two).
303 : dl 1.1 */
304 :    
305 :     long r = mix64(nextSeed());
306 :     if (origin < bound) {
307 :     long n = bound - origin, m = n - 1;
308 : dl 1.7 if ((n & m) == 0L) // power of two
309 : dl 1.1 r = (r & m) + origin;
310 : dl 1.7 else if (n > 0L) { // reject over-represented candidates
311 : dl 1.1 for (long u = r >>> 1; // ensure nonnegative
312 : dl 1.7 u + m - (r = u % n) < 0L; // rejection check
313 : dl 1.1 u = mix64(nextSeed()) >>> 1) // retry
314 :     ;
315 :     r += origin;
316 :     }
317 : dl 1.7 else { // range not representable as long
318 : dl 1.1 while (r < origin || r >= bound)
319 :     r = mix64(nextSeed());
320 :     }
321 :     }
322 :     return r;
323 :     }
324 :    
325 :     /**
326 :     * The form of nextInt used by IntStream Spliterators.
327 :     * Exactly the same as long version, except for types.
328 :     *
329 :     * @param origin the least value, unless greater than bound
330 :     * @param bound the upper bound (exclusive), must not equal origin
331 :     * @return a pseudorandom value
332 :     */
333 :     final int internalNextInt(int origin, int bound) {
334 :     int r = mix32(nextSeed());
335 :     if (origin < bound) {
336 :     int n = bound - origin, m = n - 1;
337 : dl 1.13 if ((n & m) == 0)
338 : dl 1.1 r = (r & m) + origin;
339 :     else if (n > 0) {
340 :     for (int u = r >>> 1;
341 : dl 1.7 u + m - (r = u % n) < 0;
342 : dl 1.1 u = mix32(nextSeed()) >>> 1)
343 :     ;
344 :     r += origin;
345 :     }
346 :     else {
347 :     while (r < origin || r >= bound)
348 :     r = mix32(nextSeed());
349 :     }
350 :     }
351 :     return r;
352 :     }
353 :    
354 :     /**
355 :     * The form of nextDouble used by DoubleStream Spliterators.
356 :     *
357 :     * @param origin the least value, unless greater than bound
358 :     * @param bound the upper bound (exclusive), must not equal origin
359 :     * @return a pseudorandom value
360 :     */
361 :     final double internalNextDouble(double origin, double bound) {
362 : dl 1.5 double r = (nextLong() >>> 11) * DOUBLE_UNIT;
363 : dl 1.1 if (origin < bound) {
364 :     r = r * (bound - origin) + origin;
365 : dl 1.7 if (r >= bound) // correct for rounding
366 : dl 1.1 r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
367 :     }
368 :     return r;
369 :     }
370 :    
371 :     /* ---------------- public methods ---------------- */
372 :    
373 :     /**
374 : dl 1.7 * Creates a new SplittableRandom instance using the specified
375 :     * initial seed. SplittableRandom instances created with the same
376 : dl 1.11 * seed in the same program generate identical sequences of values.
377 : dl 1.1 *
378 :     * @param seed the initial seed
379 :     */
380 :     public SplittableRandom(long seed) {
381 : dl 1.15 this(seed, INITIAL_GAMMA);
382 : dl 1.1 }
383 :    
384 :     /**
385 :     * Creates a new SplittableRandom instance that is likely to
386 :     * generate sequences of values that are statistically independent
387 :     * of those of any other instances in the current program; and
388 :     * may, and typically does, vary across program invocations.
389 :     */
390 : dl 1.15 public SplittableRandom() { // emulate seeder.split()
391 :     this.gamma = nextGamma(this.seed = seeder.addAndGet(INITIAL_GAMMA));
392 : dl 1.1 }
393 :    
394 :     /**
395 :     * Constructs and returns a new SplittableRandom instance that
396 :     * shares no mutable state with this instance. However, with very
397 :     * high probability, the set of values collectively generated by
398 :     * the two objects has the same statistical properties as if the
399 :     * same quantity of values were generated by a single thread using
400 :     * a single SplittableRandom object. Either or both of the two
401 :     * objects may be further split using the {@code split()} method,
402 :     * and the same expected statistical properties apply to the
403 :     * entire set of generators constructed by such recursive
404 :     * splitting.
405 :     *
406 :     * @return the new SplittableRandom instance
407 :     */
408 :     public SplittableRandom split() {
409 : dl 1.15 long s = nextSeed();
410 :     return new SplittableRandom(s, nextGamma(s));
411 : dl 1.1 }
412 :    
413 :     /**
414 :     * Returns a pseudorandom {@code int} value.
415 :     *
416 : dl 1.7 * @return a pseudorandom {@code int} value
417 : dl 1.1 */
418 :     public int nextInt() {
419 :     return mix32(nextSeed());
420 :     }
421 :    
422 :     /**
423 : dl 1.7 * Returns a pseudorandom {@code int} value between zero (inclusive)
424 : dl 1.1 * and the specified bound (exclusive).
425 :     *
426 : dl 1.18 * @param bound the upper bound (exclusive). Must be positive.
427 : dl 1.7 * @return a pseudorandom {@code int} value between zero
428 : jsr166 1.10 * (inclusive) and the bound (exclusive)
429 : dl 1.16 * @throws IllegalArgumentException if {@code bound} is not positive
430 : dl 1.1 */
431 :     public int nextInt(int bound) {
432 :     if (bound <= 0)
433 : dl 1.15 throw new IllegalArgumentException(BadBound);
434 : dl 1.1 // Specialize internalNextInt for origin 0
435 :     int r = mix32(nextSeed());
436 :     int m = bound - 1;
437 : dl 1.13 if ((bound & m) == 0) // power of two
438 : dl 1.1 r &= m;
439 :     else { // reject over-represented candidates
440 :     for (int u = r >>> 1;
441 : dl 1.7 u + m - (r = u % bound) < 0;
442 : dl 1.1 u = mix32(nextSeed()) >>> 1)
443 :     ;
444 :     }
445 :     return r;
446 :     }
447 :    
448 :     /**
449 :     * Returns a pseudorandom {@code int} value between the specified
450 :     * origin (inclusive) and the specified bound (exclusive).
451 :     *
452 :     * @param origin the least value returned
453 :     * @param bound the upper bound (exclusive)
454 :     * @return a pseudorandom {@code int} value between the origin
455 : jsr166 1.10 * (inclusive) and the bound (exclusive)
456 : dl 1.7 * @throws IllegalArgumentException if {@code origin} is greater than
457 : dl 1.1 * or equal to {@code bound}
458 :     */
459 :     public int nextInt(int origin, int bound) {
460 :     if (origin >= bound)
461 : dl 1.15 throw new IllegalArgumentException(BadRange);
462 : dl 1.1 return internalNextInt(origin, bound);
463 :     }
464 :    
465 :     /**
466 :     * Returns a pseudorandom {@code long} value.
467 :     *
468 : dl 1.7 * @return a pseudorandom {@code long} value
469 : dl 1.1 */
470 :     public long nextLong() {
471 :     return mix64(nextSeed());
472 :     }
473 :    
474 :     /**
475 : dl 1.7 * Returns a pseudorandom {@code long} value between zero (inclusive)
476 : dl 1.1 * and the specified bound (exclusive).
477 :     *
478 : dl 1.18 * @param bound the upper bound (exclusive). Must be positive.
479 : dl 1.7 * @return a pseudorandom {@code long} value between zero
480 : jsr166 1.10 * (inclusive) and the bound (exclusive)
481 : dl 1.16 * @throws IllegalArgumentException if {@code bound} is not positive
482 : dl 1.1 */
483 :     public long nextLong(long bound) {
484 :     if (bound <= 0)
485 : dl 1.15 throw new IllegalArgumentException(BadBound);
486 : dl 1.1 // Specialize internalNextLong for origin 0
487 :     long r = mix64(nextSeed());
488 :     long m = bound - 1;
489 :     if ((bound & m) == 0L) // power of two
490 :     r &= m;
491 :     else { // reject over-represented candidates
492 :     for (long u = r >>> 1;
493 :     u + m - (r = u % bound) < 0L;
494 :     u = mix64(nextSeed()) >>> 1)
495 :     ;
496 :     }
497 :     return r;
498 :     }
499 :    
500 :     /**
501 :     * Returns a pseudorandom {@code long} value between the specified
502 :     * origin (inclusive) and the specified bound (exclusive).
503 :     *
504 :     * @param origin the least value returned
505 :     * @param bound the upper bound (exclusive)
506 :     * @return a pseudorandom {@code long} value between the origin
507 : jsr166 1.10 * (inclusive) and the bound (exclusive)
508 : dl 1.7 * @throws IllegalArgumentException if {@code origin} is greater than
509 : dl 1.1 * or equal to {@code bound}
510 :     */
511 :     public long nextLong(long origin, long bound) {
512 :     if (origin >= bound)
513 : dl 1.15 throw new IllegalArgumentException(BadRange);
514 : dl 1.1 return internalNextLong(origin, bound);
515 :     }
516 :    
517 :     /**
518 : dl 1.7 * Returns a pseudorandom {@code double} value between zero
519 :     * (inclusive) and one (exclusive).
520 : dl 1.1 *
521 : dl 1.7 * @return a pseudorandom {@code double} value between zero
522 : dl 1.18 * (inclusive) and one (exclusive)
523 : dl 1.1 */
524 :     public double nextDouble() {
525 : dl 1.11 return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT;
526 : dl 1.1 }
527 :    
528 :     /**
529 :     * Returns a pseudorandom {@code double} value between 0.0
530 :     * (inclusive) and the specified bound (exclusive).
531 :     *
532 : dl 1.18 * @param bound the upper bound (exclusive). Must be positive.
533 : dl 1.7 * @return a pseudorandom {@code double} value between zero
534 : jsr166 1.10 * (inclusive) and the bound (exclusive)
535 : dl 1.16 * @throws IllegalArgumentException if {@code bound} is not positive
536 : dl 1.1 */
537 :     public double nextDouble(double bound) {
538 : dl 1.7 if (!(bound > 0.0))
539 : dl 1.15 throw new IllegalArgumentException(BadBound);
540 : dl 1.11 double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound;
541 : dl 1.1 return (result < bound) ? result : // correct for rounding
542 :     Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
543 :     }
544 :    
545 :     /**
546 : dl 1.7 * Returns a pseudorandom {@code double} value between the specified
547 : dl 1.1 * origin (inclusive) and bound (exclusive).
548 :     *
549 :     * @param origin the least value returned
550 : dl 1.18 * @param bound the upper bound (exclusive)
551 : dl 1.1 * @return a pseudorandom {@code double} value between the origin
552 : jsr166 1.10 * (inclusive) and the bound (exclusive)
553 : dl 1.1 * @throws IllegalArgumentException if {@code origin} is greater than
554 :     * or equal to {@code bound}
555 :     */
556 :     public double nextDouble(double origin, double bound) {
557 : dl 1.7 if (!(origin < bound))
558 : dl 1.15 throw new IllegalArgumentException(BadRange);
559 : dl 1.1 return internalNextDouble(origin, bound);
560 :     }
561 :    
562 : dl 1.11 /**
563 :     * Returns a pseudorandom {@code boolean} value.
564 :     *
565 :     * @return a pseudorandom {@code boolean} value
566 :     */
567 :     public boolean nextBoolean() {
568 :     return mix32(nextSeed()) < 0;
569 :     }
570 :    
571 : dl 1.1 // stream methods, coded in a way intended to better isolate for
572 :     // maintenance purposes the small differences across forms.
573 :    
574 :     /**
575 : dl 1.16 * Returns a stream producing the given {@code streamSize} number
576 :     * of pseudorandom {@code int} values from this generator and/or
577 :     * one split from it.
578 : dl 1.1 *
579 :     * @param streamSize the number of values to generate
580 :     * @return a stream of pseudorandom {@code int} values
581 :     * @throws IllegalArgumentException if {@code streamSize} is
582 : dl 1.7 * less than zero
583 : dl 1.1 */
584 :     public IntStream ints(long streamSize) {
585 :     if (streamSize < 0L)
586 : dl 1.15 throw new IllegalArgumentException(BadSize);
587 : dl 1.1 return StreamSupport.intStream
588 :     (new RandomIntsSpliterator
589 :     (this, 0L, streamSize, Integer.MAX_VALUE, 0),
590 :     false);
591 :     }
592 :    
593 :     /**
594 :     * Returns an effectively unlimited stream of pseudorandom {@code int}
595 : dl 1.16 * values from this generator and/or one split from it.
596 : dl 1.1 *
597 :     * @implNote This method is implemented to be equivalent to {@code
598 :     * ints(Long.MAX_VALUE)}.
599 :     *
600 :     * @return a stream of pseudorandom {@code int} values
601 :     */
602 :     public IntStream ints() {
603 :     return StreamSupport.intStream
604 :     (new RandomIntsSpliterator
605 :     (this, 0L, Long.MAX_VALUE, Integer.MAX_VALUE, 0),
606 :     false);
607 :     }
608 :    
609 :     /**
610 : dl 1.16 * Returns a stream producing the given {@code streamSize} number
611 : dl 1.18 * of pseudorandom {@code int} values from this generator and/or one split
612 :     * from it; each value conforms to the given origin (inclusive) and bound
613 :     * (exclusive).
614 : dl 1.1 *
615 :     * @param streamSize the number of values to generate
616 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
617 :     * @param randomNumberBound the bound (exclusive) of each random value
618 : dl 1.1 * @return a stream of pseudorandom {@code int} values,
619 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
620 : dl 1.1 * @throws IllegalArgumentException if {@code streamSize} is
621 : dl 1.7 * less than zero, or {@code randomNumberOrigin}
622 : dl 1.1 * is greater than or equal to {@code randomNumberBound}
623 :     */
624 :     public IntStream ints(long streamSize, int randomNumberOrigin,
625 :     int randomNumberBound) {
626 :     if (streamSize < 0L)
627 : dl 1.15 throw new IllegalArgumentException(BadSize);
628 : dl 1.1 if (randomNumberOrigin >= randomNumberBound)
629 : dl 1.15 throw new IllegalArgumentException(BadRange);
630 : dl 1.1 return StreamSupport.intStream
631 :     (new RandomIntsSpliterator
632 :     (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
633 :     false);
634 :     }
635 :    
636 :     /**
637 :     * Returns an effectively unlimited stream of pseudorandom {@code
638 : dl 1.18 * int} values from this generator and/or one split from it; each value
639 :     * conforms to the given origin (inclusive) and bound (exclusive).
640 : dl 1.1 *
641 :     * @implNote This method is implemented to be equivalent to {@code
642 :     * ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
643 :     *
644 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
645 :     * @param randomNumberBound the bound (exclusive) of each random value
646 : dl 1.1 * @return a stream of pseudorandom {@code int} values,
647 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
648 : dl 1.1 * @throws IllegalArgumentException if {@code randomNumberOrigin}
649 :     * is greater than or equal to {@code randomNumberBound}
650 :     */
651 :     public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
652 :     if (randomNumberOrigin >= randomNumberBound)
653 : dl 1.15 throw new IllegalArgumentException(BadRange);
654 : dl 1.1 return StreamSupport.intStream
655 :     (new RandomIntsSpliterator
656 :     (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
657 :     false);
658 :     }
659 :    
660 :     /**
661 : dl 1.16 * Returns a stream producing the given {@code streamSize} number
662 :     * of pseudorandom {@code long} values from this generator and/or
663 :     * one split from it.
664 : dl 1.1 *
665 :     * @param streamSize the number of values to generate
666 : dl 1.7 * @return a stream of pseudorandom {@code long} values
667 : dl 1.1 * @throws IllegalArgumentException if {@code streamSize} is
668 : dl 1.7 * less than zero
669 : dl 1.1 */
670 :     public LongStream longs(long streamSize) {
671 :     if (streamSize < 0L)
672 : dl 1.15 throw new IllegalArgumentException(BadSize);
673 : dl 1.1 return StreamSupport.longStream
674 :     (new RandomLongsSpliterator
675 :     (this, 0L, streamSize, Long.MAX_VALUE, 0L),
676 :     false);
677 :     }
678 :    
679 :     /**
680 : dl 1.16 * Returns an effectively unlimited stream of pseudorandom {@code
681 :     * long} values from this generator and/or one split from it.
682 : dl 1.1 *
683 :     * @implNote This method is implemented to be equivalent to {@code
684 :     * longs(Long.MAX_VALUE)}.
685 :     *
686 :     * @return a stream of pseudorandom {@code long} values
687 :     */
688 :     public LongStream longs() {
689 :     return StreamSupport.longStream
690 :     (new RandomLongsSpliterator
691 :     (this, 0L, Long.MAX_VALUE, Long.MAX_VALUE, 0L),
692 :     false);
693 :     }
694 :    
695 :     /**
696 : dl 1.7 * Returns a stream producing the given {@code streamSize} number of
697 : dl 1.18 * pseudorandom {@code long} values from this generator and/or one split
698 :     * from it; each value conforms to the given origin (inclusive) and bound
699 :     * (exclusive).
700 : dl 1.1 *
701 :     * @param streamSize the number of values to generate
702 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
703 :     * @param randomNumberBound the bound (exclusive) of each random value
704 : dl 1.1 * @return a stream of pseudorandom {@code long} values,
705 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
706 : dl 1.1 * @throws IllegalArgumentException if {@code streamSize} is
707 : dl 1.7 * less than zero, or {@code randomNumberOrigin}
708 : dl 1.1 * is greater than or equal to {@code randomNumberBound}
709 :     */
710 :     public LongStream longs(long streamSize, long randomNumberOrigin,
711 :     long randomNumberBound) {
712 :     if (streamSize < 0L)
713 : dl 1.15 throw new IllegalArgumentException(BadSize);
714 : dl 1.1 if (randomNumberOrigin >= randomNumberBound)
715 : dl 1.15 throw new IllegalArgumentException(BadRange);
716 : dl 1.1 return StreamSupport.longStream
717 :     (new RandomLongsSpliterator
718 :     (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
719 :     false);
720 :     }
721 :    
722 :     /**
723 :     * Returns an effectively unlimited stream of pseudorandom {@code
724 : dl 1.18 * long} values from this generator and/or one split from it; each value
725 :     * conforms to the given origin (inclusive) and bound (exclusive).
726 : dl 1.1 *
727 :     * @implNote This method is implemented to be equivalent to {@code
728 :     * longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
729 :     *
730 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
731 :     * @param randomNumberBound the bound (exclusive) of each random value
732 : dl 1.1 * @return a stream of pseudorandom {@code long} values,
733 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
734 : dl 1.1 * @throws IllegalArgumentException if {@code randomNumberOrigin}
735 :     * is greater than or equal to {@code randomNumberBound}
736 :     */
737 :     public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
738 :     if (randomNumberOrigin >= randomNumberBound)
739 : dl 1.15 throw new IllegalArgumentException(BadRange);
740 : dl 1.1 return StreamSupport.longStream
741 :     (new RandomLongsSpliterator
742 :     (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
743 :     false);
744 :     }
745 :    
746 :     /**
747 : dl 1.7 * Returns a stream producing the given {@code streamSize} number of
748 : dl 1.18 * pseudorandom {@code double} values from this generator and/or one split
749 :     * from it; each value is between zero (inclusive) and one (exclusive).
750 : dl 1.1 *
751 :     * @param streamSize the number of values to generate
752 :     * @return a stream of {@code double} values
753 :     * @throws IllegalArgumentException if {@code streamSize} is
754 : dl 1.7 * less than zero
755 : dl 1.1 */
756 :     public DoubleStream doubles(long streamSize) {
757 :     if (streamSize < 0L)
758 : dl 1.15 throw new IllegalArgumentException(BadSize);
759 : dl 1.1 return StreamSupport.doubleStream
760 :     (new RandomDoublesSpliterator
761 :     (this, 0L, streamSize, Double.MAX_VALUE, 0.0),
762 :     false);
763 :     }
764 :    
765 :     /**
766 :     * Returns an effectively unlimited stream of pseudorandom {@code
767 : dl 1.18 * double} values from this generator and/or one split from it; each value
768 :     * is between zero (inclusive) and one (exclusive).
769 : dl 1.1 *
770 :     * @implNote This method is implemented to be equivalent to {@code
771 :     * doubles(Long.MAX_VALUE)}.
772 :     *
773 :     * @return a stream of pseudorandom {@code double} values
774 :     */
775 :     public DoubleStream doubles() {
776 :     return StreamSupport.doubleStream
777 :     (new RandomDoublesSpliterator
778 :     (this, 0L, Long.MAX_VALUE, Double.MAX_VALUE, 0.0),
779 :     false);
780 :     }
781 :    
782 :     /**
783 : dl 1.7 * Returns a stream producing the given {@code streamSize} number of
784 : dl 1.18 * pseudorandom {@code double} values from this generator and/or one split
785 :     * from it; each value conforms to the given origin (inclusive) and bound
786 :     * (exclusive).
787 : dl 1.1 *
788 :     * @param streamSize the number of values to generate
789 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
790 :     * @param randomNumberBound the bound (exclusive) of each random value
791 : dl 1.1 * @return a stream of pseudorandom {@code double} values,
792 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
793 : dl 1.1 * @throws IllegalArgumentException if {@code streamSize} is
794 : dl 1.18 * less than zero
795 : dl 1.1 * @throws IllegalArgumentException if {@code randomNumberOrigin}
796 :     * is greater than or equal to {@code randomNumberBound}
797 :     */
798 :     public DoubleStream doubles(long streamSize, double randomNumberOrigin,
799 :     double randomNumberBound) {
800 :     if (streamSize < 0L)
801 : dl 1.15 throw new IllegalArgumentException(BadSize);
802 : dl 1.7 if (!(randomNumberOrigin < randomNumberBound))
803 : dl 1.15 throw new IllegalArgumentException(BadRange);
804 : dl 1.1 return StreamSupport.doubleStream
805 :     (new RandomDoublesSpliterator
806 :     (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
807 :     false);
808 :     }
809 :    
810 :     /**
811 :     * Returns an effectively unlimited stream of pseudorandom {@code
812 : dl 1.18 * double} values from this generator and/or one split from it; each value
813 :     * conforms to the given origin (inclusive) and bound (exclusive).
814 : dl 1.1 *
815 :     * @implNote This method is implemented to be equivalent to {@code
816 :     * doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
817 :     *
818 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
819 :     * @param randomNumberBound the bound (exclusive) of each random value
820 : dl 1.1 * @return a stream of pseudorandom {@code double} values,
821 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
822 : dl 1.1 * @throws IllegalArgumentException if {@code randomNumberOrigin}
823 :     * is greater than or equal to {@code randomNumberBound}
824 :     */
825 :     public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
826 : dl 1.7 if (!(randomNumberOrigin < randomNumberBound))
827 : dl 1.15 throw new IllegalArgumentException(BadRange);
828 : dl 1.1 return StreamSupport.doubleStream
829 :     (new RandomDoublesSpliterator
830 :     (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
831 :     false);
832 :     }
833 :    
834 :     /**
835 :     * Spliterator for int streams. We multiplex the four int
836 : dl 1.7 * versions into one class by treating a bound less than origin as
837 : dl 1.1 * unbounded, and also by treating "infinite" as equivalent to
838 :     * Long.MAX_VALUE. For splits, it uses the standard divide-by-two
839 :     * approach. The long and double versions of this class are
840 :     * identical except for types.
841 :     */
842 : dl 1.11 static final class RandomIntsSpliterator implements Spliterator.OfInt {
843 : dl 1.1 final SplittableRandom rng;
844 :     long index;
845 :     final long fence;
846 :     final int origin;
847 :     final int bound;
848 :     RandomIntsSpliterator(SplittableRandom rng, long index, long fence,
849 :     int origin, int bound) {
850 :     this.rng = rng; this.index = index; this.fence = fence;
851 :     this.origin = origin; this.bound = bound;
852 :     }
853 :    
854 :     public RandomIntsSpliterator trySplit() {
855 :     long i = index, m = (i + fence) >>> 1;
856 :     return (m <= i) ? null :
857 :     new RandomIntsSpliterator(rng.split(), i, index = m, origin, bound);
858 :     }
859 :    
860 :     public long estimateSize() {
861 :     return fence - index;
862 :     }
863 :    
864 :     public int characteristics() {
865 :     return (Spliterator.SIZED | Spliterator.SUBSIZED |
866 : dl 1.4 Spliterator.NONNULL | Spliterator.IMMUTABLE);
867 : dl 1.1 }
868 :    
869 :     public boolean tryAdvance(IntConsumer consumer) {
870 :     if (consumer == null) throw new NullPointerException();
871 :     long i = index, f = fence;
872 :     if (i < f) {
873 :     consumer.accept(rng.internalNextInt(origin, bound));
874 :     index = i + 1;
875 :     return true;
876 :     }
877 :     return false;
878 :     }
879 :    
880 :     public void forEachRemaining(IntConsumer consumer) {
881 :     if (consumer == null) throw new NullPointerException();
882 :     long i = index, f = fence;
883 :     if (i < f) {
884 :     index = f;
885 : dl 1.15 SplittableRandom r = rng;
886 : dl 1.1 int o = origin, b = bound;
887 :     do {
888 : dl 1.15 consumer.accept(r.internalNextInt(o, b));
889 : dl 1.1 } while (++i < f);
890 :     }
891 :     }
892 :     }
893 :    
894 :     /**
895 :     * Spliterator for long streams.
896 :     */
897 : dl 1.11 static final class RandomLongsSpliterator implements Spliterator.OfLong {
898 : dl 1.1 final SplittableRandom rng;
899 :     long index;
900 :     final long fence;
901 :     final long origin;
902 :     final long bound;
903 :     RandomLongsSpliterator(SplittableRandom rng, long index, long fence,
904 :     long origin, long bound) {
905 :     this.rng = rng; this.index = index; this.fence = fence;
906 :     this.origin = origin; this.bound = bound;
907 :     }
908 :    
909 :     public RandomLongsSpliterator trySplit() {
910 :     long i = index, m = (i + fence) >>> 1;
911 :     return (m <= i) ? null :
912 :     new RandomLongsSpliterator(rng.split(), i, index = m, origin, bound);
913 :     }
914 :    
915 :     public long estimateSize() {
916 :     return fence - index;
917 :     }
918 :    
919 :     public int characteristics() {
920 :     return (Spliterator.SIZED | Spliterator.SUBSIZED |
921 : dl 1.4 Spliterator.NONNULL | Spliterator.IMMUTABLE);
922 : dl 1.1 }
923 :    
924 :     public boolean tryAdvance(LongConsumer consumer) {
925 :     if (consumer == null) throw new NullPointerException();
926 :     long i = index, f = fence;
927 :     if (i < f) {
928 :     consumer.accept(rng.internalNextLong(origin, bound));
929 :     index = i + 1;
930 :     return true;
931 :     }
932 :     return false;
933 :     }
934 :    
935 :     public void forEachRemaining(LongConsumer consumer) {
936 :     if (consumer == null) throw new NullPointerException();
937 :     long i = index, f = fence;
938 :     if (i < f) {
939 :     index = f;
940 : dl 1.15 SplittableRandom r = rng;
941 : dl 1.1 long o = origin, b = bound;
942 :     do {
943 : dl 1.15 consumer.accept(r.internalNextLong(o, b));
944 : dl 1.1 } while (++i < f);
945 :     }
946 :     }
947 :    
948 :     }
949 :    
950 :     /**
951 :     * Spliterator for double streams.
952 :     */
953 : dl 1.11 static final class RandomDoublesSpliterator implements Spliterator.OfDouble {
954 : dl 1.1 final SplittableRandom rng;
955 :     long index;
956 :     final long fence;
957 :     final double origin;
958 :     final double bound;
959 :     RandomDoublesSpliterator(SplittableRandom rng, long index, long fence,
960 :     double origin, double bound) {
961 :     this.rng = rng; this.index = index; this.fence = fence;
962 :     this.origin = origin; this.bound = bound;
963 :     }
964 :    
965 :     public RandomDoublesSpliterator trySplit() {
966 :     long i = index, m = (i + fence) >>> 1;
967 :     return (m <= i) ? null :
968 :     new RandomDoublesSpliterator(rng.split(), i, index = m, origin, bound);
969 :     }
970 :    
971 :     public long estimateSize() {
972 :     return fence - index;
973 :     }
974 :    
975 :     public int characteristics() {
976 :     return (Spliterator.SIZED | Spliterator.SUBSIZED |
977 : dl 1.4 Spliterator.NONNULL | Spliterator.IMMUTABLE);
978 : dl 1.1 }
979 :    
980 :     public boolean tryAdvance(DoubleConsumer consumer) {
981 :     if (consumer == null) throw new NullPointerException();
982 :     long i = index, f = fence;
983 :     if (i < f) {
984 :     consumer.accept(rng.internalNextDouble(origin, bound));
985 :     index = i + 1;
986 :     return true;
987 :     }
988 :     return false;
989 :     }
990 :    
991 :     public void forEachRemaining(DoubleConsumer consumer) {
992 :     if (consumer == null) throw new NullPointerException();
993 :     long i = index, f = fence;
994 :     if (i < f) {
995 :     index = f;
996 : dl 1.15 SplittableRandom r = rng;
997 : dl 1.1 double o = origin, b = bound;
998 :     do {
999 : dl 1.15 consumer.accept(r.internalNextDouble(o, b));
1000 : dl 1.1 } while (++i < f);
1001 :     }
1002 :     }
1003 :     }
1004 :    
1005 :     }

Doug Lea
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