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