1 /*
2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation. Oracle designates this
7 * particular file as subject to the "Classpath" exception as provided
8 * by Oracle in the LICENSE file that accompanied this code.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 */
24
25 /*
26 * This file is available under and governed by the GNU General Public
27 * License version 2 only, as published by the Free Software Foundation.
28 * However, the following notice accompanied the original version of this
29 * file:
30 *
31 * Written by Doug Lea with assistance from members of JCP JSR-166
32 * Expert Group and released to the public domain, as explained at
33 * http://creativecommons.org/publicdomain/zero/1.0/
34 */
35
36 package java.util.concurrent;
37
38 import java.io.ObjectStreamField;
39 import java.security.AccessControlContext;
40 import java.util.Random;
41 import java.util.Spliterator;
42 import java.util.concurrent.atomic.AtomicInteger;
43 import java.util.concurrent.atomic.AtomicLong;
44 import java.util.function.DoubleConsumer;
45 import java.util.function.IntConsumer;
46 import java.util.function.LongConsumer;
47 import java.util.stream.DoubleStream;
48 import java.util.stream.IntStream;
49 import java.util.stream.LongStream;
50 import java.util.stream.StreamSupport;
51 import jdk.internal.misc.Unsafe;
52 import jdk.internal.misc.VM;
53
54 /**
55 * A random number generator isolated to the current thread. Like the
56 * global {@link java.util.Random} generator used by the {@link
57 * java.lang.Math} class, a {@code ThreadLocalRandom} is initialized
58 * with an internally generated seed that may not otherwise be
59 * modified. When applicable, use of {@code ThreadLocalRandom} rather
60 * than shared {@code Random} objects in concurrent programs will
61 * typically encounter much less overhead and contention. Use of
62 * {@code ThreadLocalRandom} is particularly appropriate when multiple
63 * tasks (for example, each a {@link ForkJoinTask}) use random numbers
64 * in parallel in thread pools.
65 *
66 * <p>Usages of this class should typically be of the form:
67 * {@code ThreadLocalRandom.current().nextX(...)} (where
68 * {@code X} is {@code Int}, {@code Long}, etc).
69 * When all usages are of this form, it is never possible to
70 * accidentally share a {@code ThreadLocalRandom} across multiple threads.
71 *
72 * <p>This class also provides additional commonly used bounded random
73 * generation methods.
74 *
75 * <p>Instances of {@code ThreadLocalRandom} are not cryptographically
76 * secure. Consider instead using {@link java.security.SecureRandom}
77 * in security-sensitive applications. Additionally,
78 * default-constructed instances do not use a cryptographically random
79 * seed unless the {@linkplain System#getProperty system property}
80 * {@code java.util.secureRandomSeed} is set to {@code true}.
81 *
82 * @since 1.7
83 * @author Doug Lea
84 */
85 public class ThreadLocalRandom extends Random {
86 /*
87 * This class implements the java.util.Random API (and subclasses
88 * Random) using a single static instance that accesses random
89 * number state held in class Thread (primarily, field
90 * threadLocalRandomSeed). In doing so, it also provides a home
91 * for managing package-private utilities that rely on exactly the
92 * same state as needed to maintain the ThreadLocalRandom
93 * instances. We leverage the need for an initialization flag
94 * field to also use it as a "probe" -- a self-adjusting thread
95 * hash used for contention avoidance, as well as a secondary
96 * simpler (xorShift) random seed that is conservatively used to
97 * avoid otherwise surprising users by hijacking the
98 * ThreadLocalRandom sequence. The dual use is a marriage of
99 * convenience, but is a simple and efficient way of reducing
100 * application-level overhead and footprint of most concurrent
101 * programs. Even more opportunistically, we also define here
102 * other package-private utilities that access Thread class
103 * fields.
104 *
105 * Even though this class subclasses java.util.Random, it uses the
106 * same basic algorithm as java.util.SplittableRandom. (See its
107 * internal documentation for explanations, which are not repeated
108 * here.) Because ThreadLocalRandoms are not splittable
109 * though, we use only a single 64bit gamma.
110 *
111 * Because this class is in a different package than class Thread,
112 * field access methods use Unsafe to bypass access control rules.
113 * To conform to the requirements of the Random superclass
114 * constructor, the common static ThreadLocalRandom maintains an
115 * "initialized" field for the sake of rejecting user calls to
116 * setSeed while still allowing a call from constructor. Note
117 * that serialization is completely unnecessary because there is
118 * only a static singleton. But we generate a serial form
119 * containing "rnd" and "initialized" fields to ensure
120 * compatibility across versions.
121 *
122 * Implementations of non-core methods are mostly the same as in
123 * SplittableRandom, that were in part derived from a previous
124 * version of this class.
125 *
126 * The nextLocalGaussian ThreadLocal supports the very rarely used
127 * nextGaussian method by providing a holder for the second of a
128 * pair of them. As is true for the base class version of this
129 * method, this time/space tradeoff is probably never worthwhile,
130 * but we provide identical statistical properties.
131 */
132
133 private static long mix64(long z) {
134 z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL;
135 z = (z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L;
136 return z ^ (z >>> 33);
137 }
138
139 private static int mix32(long z) {
140 z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL;
141 return (int)(((z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L) >>> 32);
142 }
143
144 /**
145 * Field used only during singleton initialization.
146 * True when constructor completes.
147 */
148 boolean initialized;
149
150 /** Constructor used only for static singleton */
151 private ThreadLocalRandom() {
152 initialized = true; // false during super() call
153 }
154
155 /**
156 * Initialize Thread fields for the current thread. Called only
157 * when Thread.threadLocalRandomProbe is zero, indicating that a
158 * thread local seed value needs to be generated. Note that even
159 * though the initialization is purely thread-local, we need to
160 * rely on (static) atomic generators to initialize the values.
161 */
162 static final void localInit() {
163 int p = probeGenerator.addAndGet(PROBE_INCREMENT);
164 int probe = (p == 0) ? 1 : p; // skip 0
165 long seed = mix64(seeder.getAndAdd(SEEDER_INCREMENT));
166 Thread t = Thread.currentThread();
167 U.putLong(t, SEED, seed);
168 U.putInt(t, PROBE, probe);
169 }
170
171 /**
172 * Returns the current thread's {@code ThreadLocalRandom}.
173 *
174 * @return the current thread's {@code ThreadLocalRandom}
175 */
176 public static ThreadLocalRandom current() {
177 if (U.getInt(Thread.currentThread(), PROBE) == 0)
178 localInit();
179 return instance;
180 }
181
182 /**
183 * Throws {@code UnsupportedOperationException}. Setting seeds in
184 * this generator is not supported.
185 *
186 * @throws UnsupportedOperationException always
187 */
188 public void setSeed(long seed) {
189 // only allow call from super() constructor
190 if (initialized)
191 throw new UnsupportedOperationException();
192 }
193
194 final long nextSeed() {
195 Thread t; long r; // read and update per-thread seed
196 U.putLong(t = Thread.currentThread(), SEED,
197 r = U.getLong(t, SEED) + GAMMA);
198 return r;
199 }
200
201 /**
202 * Generates a pseudorandom number with the indicated number of
203 * low-order bits. Because this class has no subclasses, this
204 * method cannot be invoked or overridden.
205 *
206 * @param bits random bits
207 * @return the next pseudorandom value from this random number
208 * generator's sequence
209 */
210 protected int next(int bits) {
211 return nextInt() >>> (32 - bits);
212 }
213
214 /**
215 * The form of nextLong used by LongStream Spliterators. If
216 * origin is greater than bound, acts as unbounded form of
217 * nextLong, else as bounded form.
218 *
219 * @param origin the least value, unless greater than bound
220 * @param bound the upper bound (exclusive), must not equal origin
221 * @return a pseudorandom value
222 */
223 final long internalNextLong(long origin, long bound) {
224 long r = mix64(nextSeed());
225 if (origin < bound) {
226 long n = bound - origin, m = n - 1;
227 if ((n & m) == 0L) // power of two
228 r = (r & m) + origin;
229 else if (n > 0L) { // reject over-represented candidates
230 for (long u = r >>> 1; // ensure nonnegative
231 u + m - (r = u % n) < 0L; // rejection check
232 u = mix64(nextSeed()) >>> 1) // retry
233 ;
234 r += origin;
235 }
236 else { // range not representable as long
237 while (r < origin || r >= bound)
238 r = mix64(nextSeed());
239 }
240 }
241 return r;
242 }
243
244 /**
245 * The form of nextInt used by IntStream Spliterators.
246 * Exactly the same as long version, except for types.
247 *
248 * @param origin the least value, unless greater than bound
249 * @param bound the upper bound (exclusive), must not equal origin
250 * @return a pseudorandom value
251 */
252 final int internalNextInt(int origin, int bound) {
253 int r = mix32(nextSeed());
254 if (origin < bound) {
255 int n = bound - origin, m = n - 1;
256 if ((n & m) == 0)
257 r = (r & m) + origin;
258 else if (n > 0) {
259 for (int u = r >>> 1;
260 u + m - (r = u % n) < 0;
261 u = mix32(nextSeed()) >>> 1)
262 ;
263 r += origin;
264 }
265 else {
266 while (r < origin || r >= bound)
267 r = mix32(nextSeed());
268 }
269 }
270 return r;
271 }
272
273 /**
274 * The form of nextDouble used by DoubleStream Spliterators.
275 *
276 * @param origin the least value, unless greater than bound
277 * @param bound the upper bound (exclusive), must not equal origin
278 * @return a pseudorandom value
279 */
280 final double internalNextDouble(double origin, double bound) {
281 double r = (nextLong() >>> 11) * DOUBLE_UNIT;
282 if (origin < bound) {
283 r = r * (bound - origin) + origin;
284 if (r >= bound) // correct for rounding
285 r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
286 }
287 return r;
288 }
289
290 /**
291 * Returns a pseudorandom {@code int} value.
292 *
293 * @return a pseudorandom {@code int} value
294 */
295 public int nextInt() {
296 return mix32(nextSeed());
297 }
298
299 /**
300 * Returns a pseudorandom {@code int} value between zero (inclusive)
301 * and the specified bound (exclusive).
302 *
303 * @param bound the upper bound (exclusive). Must be positive.
304 * @return a pseudorandom {@code int} value between zero
305 * (inclusive) and the bound (exclusive)
306 * @throws IllegalArgumentException if {@code bound} is not positive
307 */
308 public int nextInt(int bound) {
309 if (bound <= 0)
310 throw new IllegalArgumentException(BAD_BOUND);
311 int r = mix32(nextSeed());
312 int m = bound - 1;
313 if ((bound & m) == 0) // power of two
314 r &= m;
315 else { // reject over-represented candidates
316 for (int u = r >>> 1;
317 u + m - (r = u % bound) < 0;
318 u = mix32(nextSeed()) >>> 1)
319 ;
320 }
321 return r;
322 }
323
324 /**
325 * Returns a pseudorandom {@code int} value between the specified
326 * origin (inclusive) and the specified bound (exclusive).
327 *
328 * @param origin the least value returned
329 * @param bound the upper bound (exclusive)
330 * @return a pseudorandom {@code int} value between the origin
331 * (inclusive) and the bound (exclusive)
332 * @throws IllegalArgumentException if {@code origin} is greater than
333 * or equal to {@code bound}
334 */
335 public int nextInt(int origin, int bound) {
336 if (origin >= bound)
337 throw new IllegalArgumentException(BAD_RANGE);
338 return internalNextInt(origin, bound);
339 }
340
341 /**
342 * Returns a pseudorandom {@code long} value.
343 *
344 * @return a pseudorandom {@code long} value
345 */
346 public long nextLong() {
347 return mix64(nextSeed());
348 }
349
350 /**
351 * Returns a pseudorandom {@code long} value between zero (inclusive)
352 * and the specified bound (exclusive).
353 *
354 * @param bound the upper bound (exclusive). Must be positive.
355 * @return a pseudorandom {@code long} value between zero
356 * (inclusive) and the bound (exclusive)
357 * @throws IllegalArgumentException if {@code bound} is not positive
358 */
359 public long nextLong(long bound) {
360 if (bound <= 0)
361 throw new IllegalArgumentException(BAD_BOUND);
362 long r = mix64(nextSeed());
363 long m = bound - 1;
364 if ((bound & m) == 0L) // power of two
365 r &= m;
366 else { // reject over-represented candidates
367 for (long u = r >>> 1;
368 u + m - (r = u % bound) < 0L;
369 u = mix64(nextSeed()) >>> 1)
370 ;
371 }
372 return r;
373 }
374
375 /**
376 * Returns a pseudorandom {@code long} value between the specified
377 * origin (inclusive) and the specified bound (exclusive).
378 *
379 * @param origin the least value returned
380 * @param bound the upper bound (exclusive)
381 * @return a pseudorandom {@code long} value between the origin
382 * (inclusive) and the bound (exclusive)
383 * @throws IllegalArgumentException if {@code origin} is greater than
384 * or equal to {@code bound}
385 */
386 public long nextLong(long origin, long bound) {
387 if (origin >= bound)
388 throw new IllegalArgumentException(BAD_RANGE);
389 return internalNextLong(origin, bound);
390 }
391
392 /**
393 * Returns a pseudorandom {@code double} value between zero
394 * (inclusive) and one (exclusive).
395 *
396 * @return a pseudorandom {@code double} value between zero
397 * (inclusive) and one (exclusive)
398 */
399 public double nextDouble() {
400 return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT;
401 }
402
403 /**
404 * Returns a pseudorandom {@code double} value between 0.0
405 * (inclusive) and the specified bound (exclusive).
406 *
407 * @param bound the upper bound (exclusive). Must be positive.
408 * @return a pseudorandom {@code double} value between zero
409 * (inclusive) and the bound (exclusive)
410 * @throws IllegalArgumentException if {@code bound} is not positive
411 */
412 public double nextDouble(double bound) {
413 if (!(bound > 0.0))
414 throw new IllegalArgumentException(BAD_BOUND);
415 double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound;
416 return (result < bound) ? result : // correct for rounding
417 Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
418 }
419
420 /**
421 * Returns a pseudorandom {@code double} value between the specified
422 * origin (inclusive) and bound (exclusive).
423 *
424 * @param origin the least value returned
425 * @param bound the upper bound (exclusive)
426 * @return a pseudorandom {@code double} value between the origin
427 * (inclusive) and the bound (exclusive)
428 * @throws IllegalArgumentException if {@code origin} is greater than
429 * or equal to {@code bound}
430 */
431 public double nextDouble(double origin, double bound) {
432 if (!(origin < bound))
433 throw new IllegalArgumentException(BAD_RANGE);
434 return internalNextDouble(origin, bound);
435 }
436
437 /**
438 * Returns a pseudorandom {@code boolean} value.
439 *
440 * @return a pseudorandom {@code boolean} value
441 */
442 public boolean nextBoolean() {
443 return mix32(nextSeed()) < 0;
444 }
445
446 /**
447 * Returns a pseudorandom {@code float} value between zero
448 * (inclusive) and one (exclusive).
449 *
450 * @return a pseudorandom {@code float} value between zero
451 * (inclusive) and one (exclusive)
452 */
453 public float nextFloat() {
454 return (mix32(nextSeed()) >>> 8) * FLOAT_UNIT;
455 }
456
457 public double nextGaussian() {
458 // Use nextLocalGaussian instead of nextGaussian field
459 Double d = nextLocalGaussian.get();
460 if (d != null) {
461 nextLocalGaussian.set(null);
462 return d.doubleValue();
463 }
464 double v1, v2, s;
465 do {
466 v1 = 2 * nextDouble() - 1; // between -1 and 1
467 v2 = 2 * nextDouble() - 1; // between -1 and 1
468 s = v1 * v1 + v2 * v2;
469 } while (s >= 1 || s == 0);
470 double multiplier = StrictMath.sqrt(-2 * StrictMath.log(s)/s);
471 nextLocalGaussian.set(Double.valueOf(v2 * multiplier));
472 return v1 * multiplier;
473 }
474
475 // stream methods, coded in a way intended to better isolate for
476 // maintenance purposes the small differences across forms.
477
478 /**
479 * Returns a stream producing the given {@code streamSize} number of
480 * pseudorandom {@code int} values.
481 *
482 * @param streamSize the number of values to generate
483 * @return a stream of pseudorandom {@code int} values
484 * @throws IllegalArgumentException if {@code streamSize} is
485 * less than zero
486 * @since 1.8
487 */
488 public IntStream ints(long streamSize) {
489 if (streamSize < 0L)
490 throw new IllegalArgumentException(BAD_SIZE);
491 return StreamSupport.intStream
492 (new RandomIntsSpliterator
493 (0L, streamSize, Integer.MAX_VALUE, 0),
494 false);
495 }
496
497 /**
498 * Returns an effectively unlimited stream of pseudorandom {@code int}
499 * values.
500 *
501 * @implNote This method is implemented to be equivalent to {@code
502 * ints(Long.MAX_VALUE)}.
503 *
504 * @return a stream of pseudorandom {@code int} values
505 * @since 1.8
506 */
507 public IntStream ints() {
508 return StreamSupport.intStream
509 (new RandomIntsSpliterator
510 (0L, Long.MAX_VALUE, Integer.MAX_VALUE, 0),
511 false);
512 }
513
514 /**
515 * Returns a stream producing the given {@code streamSize} number
516 * of pseudorandom {@code int} values, each conforming to the given
517 * origin (inclusive) and bound (exclusive).
518 *
519 * @param streamSize the number of values to generate
520 * @param randomNumberOrigin the origin (inclusive) of each random value
521 * @param randomNumberBound the bound (exclusive) of each random value
522 * @return a stream of pseudorandom {@code int} values,
523 * each with the given origin (inclusive) and bound (exclusive)
524 * @throws IllegalArgumentException if {@code streamSize} is
525 * less than zero, or {@code randomNumberOrigin}
526 * is greater than or equal to {@code randomNumberBound}
527 * @since 1.8
528 */
529 public IntStream ints(long streamSize, int randomNumberOrigin,
530 int randomNumberBound) {
531 if (streamSize < 0L)
532 throw new IllegalArgumentException(BAD_SIZE);
533 if (randomNumberOrigin >= randomNumberBound)
534 throw new IllegalArgumentException(BAD_RANGE);
535 return StreamSupport.intStream
536 (new RandomIntsSpliterator
537 (0L, streamSize, randomNumberOrigin, randomNumberBound),
538 false);
539 }
540
541 /**
542 * Returns an effectively unlimited stream of pseudorandom {@code
543 * int} values, each conforming to the given origin (inclusive) and bound
544 * (exclusive).
545 *
546 * @implNote This method is implemented to be equivalent to {@code
547 * ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
548 *
549 * @param randomNumberOrigin the origin (inclusive) of each random value
550 * @param randomNumberBound the bound (exclusive) of each random value
551 * @return a stream of pseudorandom {@code int} values,
552 * each with the given origin (inclusive) and bound (exclusive)
553 * @throws IllegalArgumentException if {@code randomNumberOrigin}
554 * is greater than or equal to {@code randomNumberBound}
555 * @since 1.8
556 */
557 public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
558 if (randomNumberOrigin >= randomNumberBound)
559 throw new IllegalArgumentException(BAD_RANGE);
560 return StreamSupport.intStream
561 (new RandomIntsSpliterator
562 (0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
563 false);
564 }
565
566 /**
567 * Returns a stream producing the given {@code streamSize} number of
568 * pseudorandom {@code long} values.
569 *
570 * @param streamSize the number of values to generate
571 * @return a stream of pseudorandom {@code long} values
572 * @throws IllegalArgumentException if {@code streamSize} is
573 * less than zero
574 * @since 1.8
575 */
576 public LongStream longs(long streamSize) {
577 if (streamSize < 0L)
578 throw new IllegalArgumentException(BAD_SIZE);
579 return StreamSupport.longStream
580 (new RandomLongsSpliterator
581 (0L, streamSize, Long.MAX_VALUE, 0L),
582 false);
583 }
584
585 /**
586 * Returns an effectively unlimited stream of pseudorandom {@code long}
587 * values.
588 *
589 * @implNote This method is implemented to be equivalent to {@code
590 * longs(Long.MAX_VALUE)}.
591 *
592 * @return a stream of pseudorandom {@code long} values
593 * @since 1.8
594 */
595 public LongStream longs() {
596 return StreamSupport.longStream
597 (new RandomLongsSpliterator
598 (0L, Long.MAX_VALUE, Long.MAX_VALUE, 0L),
599 false);
600 }
601
602 /**
603 * Returns a stream producing the given {@code streamSize} number of
604 * pseudorandom {@code long}, each conforming to the given origin
605 * (inclusive) and bound (exclusive).
606 *
607 * @param streamSize the number of values to generate
608 * @param randomNumberOrigin the origin (inclusive) of each random value
609 * @param randomNumberBound the bound (exclusive) of each random value
610 * @return a stream of pseudorandom {@code long} values,
611 * each with the given origin (inclusive) and bound (exclusive)
612 * @throws IllegalArgumentException if {@code streamSize} is
613 * less than zero, or {@code randomNumberOrigin}
614 * is greater than or equal to {@code randomNumberBound}
615 * @since 1.8
616 */
617 public LongStream longs(long streamSize, long randomNumberOrigin,
618 long randomNumberBound) {
619 if (streamSize < 0L)
620 throw new IllegalArgumentException(BAD_SIZE);
621 if (randomNumberOrigin >= randomNumberBound)
622 throw new IllegalArgumentException(BAD_RANGE);
623 return StreamSupport.longStream
624 (new RandomLongsSpliterator
625 (0L, streamSize, randomNumberOrigin, randomNumberBound),
626 false);
627 }
628
629 /**
630 * Returns an effectively unlimited stream of pseudorandom {@code
631 * long} values, each conforming to the given origin (inclusive) and bound
632 * (exclusive).
633 *
634 * @implNote This method is implemented to be equivalent to {@code
635 * longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
636 *
637 * @param randomNumberOrigin the origin (inclusive) of each random value
638 * @param randomNumberBound the bound (exclusive) of each random value
639 * @return a stream of pseudorandom {@code long} values,
640 * each with the given origin (inclusive) and bound (exclusive)
641 * @throws IllegalArgumentException if {@code randomNumberOrigin}
642 * is greater than or equal to {@code randomNumberBound}
643 * @since 1.8
644 */
645 public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
646 if (randomNumberOrigin >= randomNumberBound)
647 throw new IllegalArgumentException(BAD_RANGE);
648 return StreamSupport.longStream
649 (new RandomLongsSpliterator
650 (0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
651 false);
652 }
653
654 /**
655 * Returns a stream producing the given {@code streamSize} number of
656 * pseudorandom {@code double} values, each between zero
657 * (inclusive) and one (exclusive).
658 *
659 * @param streamSize the number of values to generate
660 * @return a stream of {@code double} values
661 * @throws IllegalArgumentException if {@code streamSize} is
662 * less than zero
663 * @since 1.8
664 */
665 public DoubleStream doubles(long streamSize) {
666 if (streamSize < 0L)
667 throw new IllegalArgumentException(BAD_SIZE);
668 return StreamSupport.doubleStream
669 (new RandomDoublesSpliterator
670 (0L, streamSize, Double.MAX_VALUE, 0.0),
671 false);
672 }
673
674 /**
675 * Returns an effectively unlimited stream of pseudorandom {@code
676 * double} values, each between zero (inclusive) and one
677 * (exclusive).
678 *
679 * @implNote This method is implemented to be equivalent to {@code
680 * doubles(Long.MAX_VALUE)}.
681 *
682 * @return a stream of pseudorandom {@code double} values
683 * @since 1.8
684 */
685 public DoubleStream doubles() {
686 return StreamSupport.doubleStream
687 (new RandomDoublesSpliterator
688 (0L, Long.MAX_VALUE, Double.MAX_VALUE, 0.0),
689 false);
690 }
691
692 /**
693 * Returns a stream producing the given {@code streamSize} number of
694 * pseudorandom {@code double} values, each conforming to the given origin
695 * (inclusive) and bound (exclusive).
696 *
697 * @param streamSize the number of values to generate
698 * @param randomNumberOrigin the origin (inclusive) of each random value
699 * @param randomNumberBound the bound (exclusive) of each random value
700 * @return a stream of pseudorandom {@code double} values,
701 * each with the given origin (inclusive) and bound (exclusive)
702 * @throws IllegalArgumentException if {@code streamSize} is
703 * less than zero, or {@code randomNumberOrigin}
704 * is greater than or equal to {@code randomNumberBound}
705 * @since 1.8
706 */
707 public DoubleStream doubles(long streamSize, double randomNumberOrigin,
708 double randomNumberBound) {
709 if (streamSize < 0L)
710 throw new IllegalArgumentException(BAD_SIZE);
711 if (!(randomNumberOrigin < randomNumberBound))
712 throw new IllegalArgumentException(BAD_RANGE);
713 return StreamSupport.doubleStream
714 (new RandomDoublesSpliterator
715 (0L, streamSize, randomNumberOrigin, randomNumberBound),
716 false);
717 }
718
719 /**
720 * Returns an effectively unlimited stream of pseudorandom {@code
721 * double} values, each conforming to the given origin (inclusive) and bound
722 * (exclusive).
723 *
724 * @implNote This method is implemented to be equivalent to {@code
725 * doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
726 *
727 * @param randomNumberOrigin the origin (inclusive) of each random value
728 * @param randomNumberBound the bound (exclusive) of each random value
729 * @return a stream of pseudorandom {@code double} values,
730 * each with the given origin (inclusive) and bound (exclusive)
731 * @throws IllegalArgumentException if {@code randomNumberOrigin}
732 * is greater than or equal to {@code randomNumberBound}
733 * @since 1.8
734 */
735 public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
736 if (!(randomNumberOrigin < randomNumberBound))
737 throw new IllegalArgumentException(BAD_RANGE);
738 return StreamSupport.doubleStream
739 (new RandomDoublesSpliterator
740 (0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
741 false);
742 }
743
744 /**
745 * Spliterator for int streams. We multiplex the four int
746 * versions into one class by treating a bound less than origin as
747 * unbounded, and also by treating "infinite" as equivalent to
748 * Long.MAX_VALUE. For splits, it uses the standard divide-by-two
749 * approach. The long and double versions of this class are
750 * identical except for types.
751 */
752 private static final class RandomIntsSpliterator
753 implements Spliterator.OfInt {
754 long index;
755 final long fence;
756 final int origin;
757 final int bound;
758 RandomIntsSpliterator(long index, long fence,
759 int origin, int bound) {
760 this.index = index; this.fence = fence;
761 this.origin = origin; this.bound = bound;
762 }
763
764 public RandomIntsSpliterator trySplit() {
765 long i = index, m = (i + fence) >>> 1;
766 return (m <= i) ? null :
767 new RandomIntsSpliterator(i, index = m, origin, bound);
768 }
769
770 public long estimateSize() {
771 return fence - index;
772 }
773
774 public int characteristics() {
775 return (Spliterator.SIZED | Spliterator.SUBSIZED |
776 Spliterator.NONNULL | Spliterator.IMMUTABLE);
777 }
778
779 public boolean tryAdvance(IntConsumer consumer) {
780 if (consumer == null) throw new NullPointerException();
781 long i = index, f = fence;
782 if (i < f) {
783 consumer.accept(ThreadLocalRandom.current().internalNextInt(origin, bound));
784 index = i + 1;
785 return true;
786 }
787 return false;
788 }
789
790 public void forEachRemaining(IntConsumer consumer) {
791 if (consumer == null) throw new NullPointerException();
792 long i = index, f = fence;
793 if (i < f) {
794 index = f;
795 int o = origin, b = bound;
796 ThreadLocalRandom rng = ThreadLocalRandom.current();
797 do {
798 consumer.accept(rng.internalNextInt(o, b));
799 } while (++i < f);
800 }
801 }
802 }
803
804 /**
805 * Spliterator for long streams.
806 */
807 private static final class RandomLongsSpliterator
808 implements Spliterator.OfLong {
809 long index;
810 final long fence;
811 final long origin;
812 final long bound;
813 RandomLongsSpliterator(long index, long fence,
814 long origin, long bound) {
815 this.index = index; this.fence = fence;
816 this.origin = origin; this.bound = bound;
817 }
818
819 public RandomLongsSpliterator trySplit() {
820 long i = index, m = (i + fence) >>> 1;
821 return (m <= i) ? null :
822 new RandomLongsSpliterator(i, index = m, origin, bound);
823 }
824
825 public long estimateSize() {
826 return fence - index;
827 }
828
829 public int characteristics() {
830 return (Spliterator.SIZED | Spliterator.SUBSIZED |
831 Spliterator.NONNULL | Spliterator.IMMUTABLE);
832 }
833
834 public boolean tryAdvance(LongConsumer consumer) {
835 if (consumer == null) throw new NullPointerException();
836 long i = index, f = fence;
837 if (i < f) {
838 consumer.accept(ThreadLocalRandom.current().internalNextLong(origin, bound));
839 index = i + 1;
840 return true;
841 }
842 return false;
843 }
844
845 public void forEachRemaining(LongConsumer consumer) {
846 if (consumer == null) throw new NullPointerException();
847 long i = index, f = fence;
848 if (i < f) {
849 index = f;
850 long o = origin, b = bound;
851 ThreadLocalRandom rng = ThreadLocalRandom.current();
852 do {
853 consumer.accept(rng.internalNextLong(o, b));
854 } while (++i < f);
855 }
856 }
857
858 }
859
860 /**
861 * Spliterator for double streams.
862 */
863 private static final class RandomDoublesSpliterator
864 implements Spliterator.OfDouble {
865 long index;
866 final long fence;
867 final double origin;
868 final double bound;
869 RandomDoublesSpliterator(long index, long fence,
870 double origin, double bound) {
871 this.index = index; this.fence = fence;
872 this.origin = origin; this.bound = bound;
873 }
874
875 public RandomDoublesSpliterator trySplit() {
876 long i = index, m = (i + fence) >>> 1;
877 return (m <= i) ? null :
878 new RandomDoublesSpliterator(i, index = m, origin, bound);
879 }
880
881 public long estimateSize() {
882 return fence - index;
883 }
884
885 public int characteristics() {
886 return (Spliterator.SIZED | Spliterator.SUBSIZED |
887 Spliterator.NONNULL | Spliterator.IMMUTABLE);
888 }
889
890 public boolean tryAdvance(DoubleConsumer consumer) {
891 if (consumer == null) throw new NullPointerException();
892 long i = index, f = fence;
893 if (i < f) {
894 consumer.accept(ThreadLocalRandom.current().internalNextDouble(origin, bound));
895 index = i + 1;
896 return true;
897 }
898 return false;
899 }
900
901 public void forEachRemaining(DoubleConsumer consumer) {
902 if (consumer == null) throw new NullPointerException();
903 long i = index, f = fence;
904 if (i < f) {
905 index = f;
906 double o = origin, b = bound;
907 ThreadLocalRandom rng = ThreadLocalRandom.current();
908 do {
909 consumer.accept(rng.internalNextDouble(o, b));
910 } while (++i < f);
911 }
912 }
913 }
914
915
916 // Within-package utilities
917
918 /*
919 * Descriptions of the usages of the methods below can be found in
920 * the classes that use them. Briefly, a thread's "probe" value is
921 * a non-zero hash code that (probably) does not collide with
922 * other existing threads with respect to any power of two
923 * collision space. When it does collide, it is pseudo-randomly
924 * adjusted (using a Marsaglia XorShift). The nextSecondarySeed
925 * method is used in the same contexts as ThreadLocalRandom, but
926 * only for transient usages such as random adaptive spin/block
927 * sequences for which a cheap RNG suffices and for which it could
928 * in principle disrupt user-visible statistical properties of the
929 * main ThreadLocalRandom if we were to use it.
930 *
931 * Note: Because of package-protection issues, versions of some
932 * these methods also appear in some subpackage classes.
933 */
934
935 /**
936 * Returns the probe value for the current thread without forcing
937 * initialization. Note that invoking ThreadLocalRandom.current()
938 * can be used to force initialization on zero return.
939 */
940 static final int getProbe() {
941 return U.getInt(Thread.currentThread(), PROBE);
942 }
943
944 /**
945 * Pseudo-randomly advances and records the given probe value for the
946 * given thread.
947 */
948 static final int advanceProbe(int probe) {
949 probe ^= probe << 13; // xorshift
950 probe ^= probe >>> 17;
951 probe ^= probe << 5;
952 U.putInt(Thread.currentThread(), PROBE, probe);
953 return probe;
954 }
955
956 /**
957 * Returns the pseudo-randomly initialized or updated secondary seed.
958 */
959 static final int nextSecondarySeed() {
960 int r;
961 Thread t = Thread.currentThread();
962 if ((r = U.getInt(t, SECONDARY)) != 0) {
963 r ^= r << 13; // xorshift
964 r ^= r >>> 17;
965 r ^= r << 5;
966 }
967 else if ((r = mix32(seeder.getAndAdd(SEEDER_INCREMENT))) == 0)
968 r = 1; // avoid zero
969 U.putInt(t, SECONDARY, r);
970 return r;
971 }
972
973 // Support for other package-private ThreadLocal access
974
975 /**
976 * Erases ThreadLocals by nulling out Thread maps.
977 */
978 static final void eraseThreadLocals(Thread thread) {
979 U.putObject(thread, THREADLOCALS, null);
980 U.putObject(thread, INHERITABLETHREADLOCALS, null);
981 }
982
983 static final void setInheritedAccessControlContext(Thread thread,
984 AccessControlContext acc) {
985 U.putObjectRelease(thread, INHERITEDACCESSCONTROLCONTEXT, acc);
986 }
987
988 // Serialization support
989
990 private static final long serialVersionUID = -5851777807851030925L;
991
992 /**
993 * @serialField rnd long
994 * seed for random computations
995 * @serialField initialized boolean
996 * always true
997 */
998 private static final ObjectStreamField[] serialPersistentFields = {
999 new ObjectStreamField("rnd", long.class),
1000 new ObjectStreamField("initialized", boolean.class),
1001 };
1002
1003 /**
1004 * Saves the {@code ThreadLocalRandom} to a stream (that is, serializes it).
1005 * @param s the stream
1006 * @throws java.io.IOException if an I/O error occurs
1007 */
1008 private void writeObject(java.io.ObjectOutputStream s)
1009 throws java.io.IOException {
1010
1011 java.io.ObjectOutputStream.PutField fields = s.putFields();
1012 fields.put("rnd", U.getLong(Thread.currentThread(), SEED));
1013 fields.put("initialized", true);
1014 s.writeFields();
1015 }
1016
1017 /**
1018 * Returns the {@link #current() current} thread's {@code ThreadLocalRandom}.
1019 * @return the {@link #current() current} thread's {@code ThreadLocalRandom}
1020 */
1021 private Object readResolve() {
1022 return current();
1023 }
1024
1025 // Static initialization
1026
1027 /**
1028 * The seed increment.
1029 */
1030 private static final long GAMMA = 0x9e3779b97f4a7c15L;
1031
1032 /**
1033 * The increment for generating probe values.
1034 */
1035 private static final int PROBE_INCREMENT = 0x9e3779b9;
1036
1037 /**
1038 * The increment of seeder per new instance.
1039 */
1040 private static final long SEEDER_INCREMENT = 0xbb67ae8584caa73bL;
1041
1042 /**
1043 * The least non-zero value returned by nextDouble(). This value
1044 * is scaled by a random value of 53 bits to produce a result.
1045 */
1046 private static final double DOUBLE_UNIT = 0x1.0p-53; // 1.0 / (1L << 53)
1047 private static final float FLOAT_UNIT = 0x1.0p-24f; // 1.0f / (1 << 24)
1048
1049 // IllegalArgumentException messages
1050 static final String BAD_BOUND = "bound must be positive";
1051 static final String BAD_RANGE = "bound must be greater than origin";
1052 static final String BAD_SIZE = "size must be non-negative";
1053
1054 // Unsafe mechanics
1055 private static final Unsafe U = Unsafe.getUnsafe();
1056 private static final long SEED = U.objectFieldOffset
1057 (Thread.class, "threadLocalRandomSeed");
1058 private static final long PROBE = U.objectFieldOffset
1059 (Thread.class, "threadLocalRandomProbe");
1060 private static final long SECONDARY = U.objectFieldOffset
1061 (Thread.class, "threadLocalRandomSecondarySeed");
1062 private static final long THREADLOCALS = U.objectFieldOffset
1063 (Thread.class, "threadLocals");
1064 private static final long INHERITABLETHREADLOCALS = U.objectFieldOffset
1065 (Thread.class, "inheritableThreadLocals");
1066 private static final long INHERITEDACCESSCONTROLCONTEXT = U.objectFieldOffset
1067 (Thread.class, "inheritedAccessControlContext");
1068
1069 /** Rarely-used holder for the second of a pair of Gaussians */
1070 private static final ThreadLocal<Double> nextLocalGaussian =
1071 new ThreadLocal<>();
1072
1073 /** Generates per-thread initialization/probe field */
1074 private static final AtomicInteger probeGenerator = new AtomicInteger();
1075
1076 /** The common ThreadLocalRandom */
1077 static final ThreadLocalRandom instance = new ThreadLocalRandom();
1078
1079 /**
1080 * The next seed for default constructors.
1081 */
1082 private static final AtomicLong seeder
1083 = new AtomicLong(mix64(System.currentTimeMillis()) ^
1084 mix64(System.nanoTime()));
1085
1086 // at end of <clinit> to survive static initialization circularity
1087 static {
1088 String sec = VM.getSavedProperty("java.util.secureRandomSeed");
1089 if (Boolean.parseBoolean(sec)) {
1090 byte[] seedBytes = java.security.SecureRandom.getSeed(8);
1091 long s = (long)seedBytes[0] & 0xffL;
1092 for (int i = 1; i < 8; ++i)
1093 s = (s << 8) | ((long)seedBytes[i] & 0xffL);
1094 seeder.set(s);
1095 }
1096 }
1097 }
1098