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1 : dl 1.1 /*
2 :     * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
3 :     * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 :     *
5 :     * This code is free software; you can redistribute it and/or modify it
6 :     * under the terms of the GNU General Public License version 2 only, as
7 :     * published by the Free Software Foundation. Oracle designates this
8 :     * particular file as subject to the "Classpath" exception as provided
9 :     * by Oracle in the LICENSE file that accompanied this code.
10 :     *
11 :     * This code is distributed in the hope that it will be useful, but WITHOUT
12 :     * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 :     * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 :     * version 2 for more details (a copy is included in the LICENSE file that
15 :     * accompanied this code).
16 :     *
17 :     * You should have received a copy of the GNU General Public License version
18 :     * 2 along with this work; if not, write to the Free Software Foundation,
19 :     * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 :     *
21 :     * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 :     * or visit www.oracle.com if you need additional information or have any
23 :     * questions.
24 :     */
25 :    
26 :     package java.util;
27 :    
28 :     import java.util.concurrent.atomic.AtomicLong;
29 :     import java.util.Spliterator;
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 :     /**
40 :     * A generator of uniform pseudorandom values applicable for use in
41 :     * (among other contexts) isolated parallel computations that may
42 :     * generate subtasks. Class 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 :     * {@link java.util.Random} but differs in the following ways: <ul>
46 :     *
47 :     * <li>Series of generated values pass the DieHarder suite testing
48 :     * independence and uniformity properties of random number generators.
49 :     * (Most recently validated with <a
50 :     * href="http://www.phy.duke.edu/~rgb/General/dieharder.php"> version
51 :     * 3.31.1</a>.) These tests validate only the methods for certain
52 :     * types and ranges, but similar properties are expected to hold, at
53 :     * least approximately, for others as well. </li>
54 :     *
55 :     * <li> Method {@link #split} constructs and returns a new
56 :     * SplittableRandom instance that shares no mutable state with the
57 :     * current instance. However, with very high probability, the set of
58 :     * values collectively generated by the two objects has the same
59 :     * statistical properties as if the same quantity of values were
60 :     * generated by a single thread using a single {@code
61 :     * SplittableRandom} object. </li>
62 :     *
63 :     * <li>Instances of SplittableRandom are <em>not</em> thread-safe.
64 :     * They are designed to be split, not shared, across threads. For
65 :     * example, a {@link java.util.concurrent.ForkJoinTask
66 :     * fork/join-style} computation using random numbers might include a
67 :     * construction of the form {@code new
68 :     * Subtask(aSplittableRandom.split()).fork()}.
69 :     *
70 :     * <li>This class provides additional methods for generating random
71 :     * streams, that employ the above techniques when used in {@code
72 :     * stream.parallel()} mode.</li>
73 :     *
74 :     * </ul>
75 :     *
76 :     * @author Guy Steele
77 : dl 1.2 * @author Doug Lea
78 : dl 1.1 * @since 1.8
79 :     */
80 :     public class SplittableRandom {
81 :    
82 :     /*
83 :     * File organization: First the non-public methods that constitute
84 :     * the main algorithm, then the main public methods, followed by
85 :     * some custom spliterator classes needed for stream methods.
86 :     *
87 :     * Credits: Primary algorithm and code by Guy Steele. Stream
88 :     * support methods by Doug Lea. Documentation jointly produced
89 :     * with additional help from Brian Goetz.
90 :     */
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, but improves and extends it in several ways.
99 :     *
100 :     * The primary update step is simply to add a constant ("gamma")
101 :     * to the current seed, modulo a prime ("George"). However, the
102 :     * nextLong and nextInt methods do not return this value, but
103 :     * instead the results of bit-mixing transformations that produce
104 :     * more uniformly distributed sequences.
105 :     *
106 :     * "George" is the otherwise nameless (because it cannot be
107 :     * represented) prime number 2^64+13. Using a prime number larger
108 :     * than can fit in a long ensures that all possible long values
109 :     * can occur, plus 13 others that just get skipped over when they
110 :     * are encountered; see method addGammaModGeorge. For this to
111 :     * work, initial gamma values must be at least 13.
112 :     *
113 :     * The value of gamma differs for each instance across a series of
114 :     * splits, and is generated using a slightly stripped-down variant
115 :     * of the same algorithm, but operating across calls to split(),
116 : dl 1.2 * not calls to nextSeed(): Each instance carries the state of
117 : dl 1.1 * this generator as nextSplit, and uses mix64(nextSplit) as its
118 :     * own gamma value. Computations of gammas themselves use a fixed
119 :     * constant as the second argument to the addGammaModGeorge
120 :     * function, GAMMA_GAMMA, a "genuinely random" number from a
121 :     * radioactive decay reading (obtained from
122 :     * http://www.fourmilab.ch/hotbits/) meeting the above range
123 :     * constraint. Using a fixed constant maintains the invariant that
124 :     * the value of gamma is the same for every instance that is at
125 :     * the same split-distance from their common root. (Note: there is
126 :     * nothing especially magic about obtaining this constant from a
127 :     * "truly random" physical source rather than just choosing one
128 :     * arbitrarily; using "hotbits" was merely an aesthetically pleasing
129 :     * choice. In either case, good statistical behavior of the
130 :     * algorithm should be, and was, verified by using the DieHarder
131 :     * test suite.)
132 :     *
133 :     * The mix64 bit-mixing function called by nextLong and other
134 :     * methods computes the same value as the "64-bit finalizer"
135 :     * function in Austin Appleby's MurmurHash3 algorithm. See
136 :     * http://code.google.com/p/smhasher/wiki/MurmurHash3 , which
137 :     * comments: "The constants for the finalizers were generated by a
138 :     * simple simulated-annealing algorithm, and both avalanche all
139 :     * bits of 'h' to within 0.25% bias." It also appears to work to
140 :     * use instead any of the variants proposed by David Stafford at
141 :     * http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html
142 :     * but these variants have not yet been tested as thoroughly
143 :     * in the context of the implementation of SplittableRandom.
144 :     *
145 :     * The mix32 function used for nextInt just consists of two of the
146 :     * five lines of mix64; avalanche testing shows that the 64-bit result
147 :     * has its top 32 bits avalanched well, though not the bottom 32 bits.
148 :     * DieHarder tests show that it is adequate for generating one
149 :     * random int from the 64-bit result of nextSeed.
150 :     *
151 :     * Support for the default (no-argument) constructor relies on an
152 :     * AtomicLong (defaultSeedGenerator) to help perform the
153 :     * equivalent of a split of a statically constructed
154 :     * SplittableRandom. Unlike other cases, this split must be
155 :     * performed in a thread-safe manner. We use
156 :     * AtomicLong.compareAndSet as the (typically) most efficient
157 :     * mechanism. To bootstrap, we start off using System.nanotime(),
158 :     * and update using another "genuinely random" constant
159 :     * DEFAULT_SEED_GAMMA. The default constructor uses GAMMA_GAMMA,
160 :     * not 0, for its splitSeed argument (addGammaModGeorge(0,
161 :     * GAMMA_GAMMA) == GAMMA_GAMMA) to reflect that each is split from
162 :     * this root generator, even though the root is not explicitly
163 :     * represented as a SplittableRandom.
164 :     */
165 :    
166 :     /**
167 :     * The "genuinely random" value for producing new gamma values.
168 :     * The value is arbitrary, subject to the requirement that it be
169 :     * greater or equal to 13.
170 :     */
171 :     private static final long GAMMA_GAMMA = 0xF2281E2DBA6606F3L;
172 :    
173 :     /**
174 :     * The "genuinely random" seed update value for default constructors.
175 :     * The value is arbitrary, subject to the requirement that it be
176 :     * greater or equal to 13.
177 :     */
178 :     private static final long DEFAULT_SEED_GAMMA = 0xBD24B73A95FB84D9L;
179 :    
180 :     /**
181 : dl 1.5 * The least non-zero value returned by nextDouble(). This value
182 : dl 1.6 * is scaled by a random value of 52 bits to produce a result.
183 : dl 1.5 */
184 :     private static final double DOUBLE_UNIT = 1.0 / (1L << 53);
185 :    
186 :     /**
187 : dl 1.1 * The next seed for default constructors.
188 :     */
189 :     private static final AtomicLong defaultSeedGenerator =
190 :     new AtomicLong(System.nanoTime());
191 :    
192 :     /**
193 :     * The seed, updated only via method nextSeed.
194 :     */
195 :     private long seed;
196 :    
197 :     /**
198 :     * The constant value added to seed (mod George) on each update.
199 :     */
200 :     private final long gamma;
201 :    
202 :     /**
203 :     * The next seed to use for splits. Propagated using
204 :     * addGammaModGeorge across instances.
205 :     */
206 :     private final long nextSplit;
207 :    
208 :     /**
209 :     * Internal constructor used by all other constructors and by
210 :     * method split. Establishes the initial seed for this instance,
211 :     * and uses the given splitSeed to establish gamma, as well as the
212 :     * nextSplit to use by this instance.
213 :     */
214 :     private SplittableRandom(long seed, long splitSeed) {
215 :     this.seed = seed;
216 :     long s = splitSeed, g;
217 :     do { // ensure gamma >= 13, considered as an unsigned integer
218 :     s = addGammaModGeorge(s, GAMMA_GAMMA);
219 :     g = mix64(s);
220 :     } while (Long.compareUnsigned(g, 13L) < 0);
221 :     this.gamma = g;
222 :     this.nextSplit = s;
223 :     }
224 :    
225 :     /**
226 :     * Adds the given gamma value, g, to the given seed value s, mod
227 :     * George (2^64+13). We regard s and g as unsigned values
228 :     * (ranging from 0 to 2^64-1). We add g to s either once or twice
229 :     * (mod George) as necessary to produce an (unsigned) result less
230 :     * than 2^64. We require that g must be at least 13. This
231 :     * guarantees that if (s+g) mod George >= 2^64 then (s+g+g) mod
232 :     * George < 2^64; thus we need only a conditional, not a loop,
233 :     * to be sure of getting a representable value.
234 :     *
235 :     * @param s a seed value
236 :     * @param g a gamma value, 13 <= g (as unsigned)
237 :     */
238 :     private static long addGammaModGeorge(long s, long g) {
239 :     long p = s + g;
240 :     if (Long.compareUnsigned(p, g) >= 0)
241 :     return p;
242 :     long q = p - 13L;
243 :     return (Long.compareUnsigned(p, 13L) >= 0) ? q : (q + g);
244 :     }
245 :    
246 :     /**
247 :     * Updates in-place and returns seed.
248 :     * See above for explanation.
249 :     */
250 :     private long nextSeed() {
251 :     return seed = addGammaModGeorge(seed, gamma);
252 :     }
253 :    
254 :     /**
255 :     * Returns a bit-mixed transformation of its argument.
256 :     * See above for explanation.
257 :     */
258 :     private static long mix64(long z) {
259 :     z ^= (z >>> 33);
260 :     z *= 0xff51afd7ed558ccdL;
261 :     z ^= (z >>> 33);
262 :     z *= 0xc4ceb9fe1a85ec53L;
263 :     z ^= (z >>> 33);
264 :     return z;
265 :     }
266 :    
267 :     /**
268 :     * Returns a bit-mixed int transformation of its argument.
269 :     * See above for explanation.
270 :     */
271 :     private static int mix32(long z) {
272 :     z ^= (z >>> 33);
273 :     z *= 0xc4ceb9fe1a85ec53L;
274 :     return (int)(z >>> 32);
275 :     }
276 :    
277 :     /**
278 :     * Atomically updates and returns next seed for default constructor
279 :     */
280 :     private static long nextDefaultSeed() {
281 :     long oldSeed, newSeed;
282 :     do {
283 :     oldSeed = defaultSeedGenerator.get();
284 :     newSeed = addGammaModGeorge(oldSeed, DEFAULT_SEED_GAMMA);
285 :     } while (!defaultSeedGenerator.compareAndSet(oldSeed, newSeed));
286 :     return mix64(newSeed);
287 :     }
288 :    
289 :     /*
290 :     * Internal versions of nextX methods used by streams, as well as
291 :     * the public nextX(origin, bound) methods. These exist mainly to
292 :     * avoid the need for multiple versions of stream spliterators
293 :     * across the different exported forms of streams.
294 :     */
295 :    
296 :     /**
297 :     * The form of nextLong used by LongStream Spliterators. If
298 :     * origin is greater than bound, acts as unbounded form of
299 :     * nextLong, else as bounded form.
300 :     *
301 :     * @param origin the least value, unless greater than bound
302 :     * @param bound the upper bound (exclusive), must not equal origin
303 :     * @return a pseudorandom value
304 :     */
305 :     final long internalNextLong(long origin, long bound) {
306 :     /*
307 :     * Four Cases:
308 :     *
309 :     * 1. If the arguments indicate unbounded form, act as
310 :     * nextLong().
311 :     *
312 :     * 2. If the range is an exact power of two, apply the
313 :     * associated bit mask.
314 :     *
315 :     * 3. If the range is positive, loop to avoid potential bias
316 :     * when the implicit nextLong() bound (2<sup>64</sup>) is not
317 :     * evenly divisible by the range. The loop rejects candidates
318 :     * computed from otherwise over-represented values. The
319 :     * expected number of iterations under an ideal generator
320 : dl 1.4 * varies from 1 to 2, depending on the bound. The loop itself
321 :     * takes an unlovable form. Because the first candidate is
322 :     * already available, we need a break-in-the-middle
323 :     * construction, which is concisely but cryptically performed
324 :     * within the while-condition of a body-less for loop.
325 : dl 1.1 *
326 :     * 4. Otherwise, the range cannot be represented as a positive
327 : dl 1.4 * long. The loop repeatedly generates unbounded longs until
328 :     * obtaining a candidate meeting constraints (with an expected
329 :     * number of iterations of less than two).
330 : dl 1.1 */
331 :    
332 :     long r = mix64(nextSeed());
333 :     if (origin < bound) {
334 :     long n = bound - origin, m = n - 1;
335 :     if ((n & m) == 0L) // power of two
336 :     r = (r & m) + origin;
337 :     else if (n > 0) { // reject over-represented candidates
338 :     for (long u = r >>> 1; // ensure nonnegative
339 :     u + m - (r = u % n) < 0L; // reject
340 :     u = mix64(nextSeed()) >>> 1) // retry
341 :     ;
342 :     r += origin;
343 :     }
344 :     else { // range not representable as long
345 :     while (r < origin || r >= bound)
346 :     r = mix64(nextSeed());
347 :     }
348 :     }
349 :     return r;
350 :     }
351 :    
352 :     /**
353 :     * The form of nextInt used by IntStream Spliterators.
354 :     * Exactly the same as long version, except for types.
355 :     *
356 :     * @param origin the least value, unless greater than bound
357 :     * @param bound the upper bound (exclusive), must not equal origin
358 :     * @return a pseudorandom value
359 :     */
360 :     final int internalNextInt(int origin, int bound) {
361 :     int r = mix32(nextSeed());
362 :     if (origin < bound) {
363 :     int n = bound - origin, m = n - 1;
364 :     if ((n & m) == 0L)
365 :     r = (r & m) + origin;
366 :     else if (n > 0) {
367 :     for (int u = r >>> 1;
368 :     u + m - (r = u % n) < 0L;
369 :     u = mix32(nextSeed()) >>> 1)
370 :     ;
371 :     r += origin;
372 :     }
373 :     else {
374 :     while (r < origin || r >= bound)
375 :     r = mix32(nextSeed());
376 :     }
377 :     }
378 :     return r;
379 :     }
380 :    
381 :     /**
382 :     * The form of nextDouble used by DoubleStream Spliterators.
383 :     *
384 :     * @param origin the least value, unless greater than bound
385 :     * @param bound the upper bound (exclusive), must not equal origin
386 :     * @return a pseudorandom value
387 :     */
388 :     final double internalNextDouble(double origin, double bound) {
389 : dl 1.5 double r = (nextLong() >>> 11) * DOUBLE_UNIT;
390 : dl 1.1 if (origin < bound) {
391 :     r = r * (bound - origin) + origin;
392 :     if (r == bound) // correct for rounding
393 :     r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
394 :     }
395 :     return r;
396 :     }
397 :    
398 :     /* ---------------- public methods ---------------- */
399 :    
400 :     /**
401 :     * Creates a new SplittableRandom instance using the given initial
402 :     * seed. Two SplittableRandom instances created with the same seed
403 :     * generate identical sequences of values.
404 :     *
405 :     * @param seed the initial seed
406 :     */
407 :     public SplittableRandom(long seed) {
408 :     this(seed, 0);
409 :     }
410 :    
411 :     /**
412 :     * Creates a new SplittableRandom instance that is likely to
413 :     * generate sequences of values that are statistically independent
414 :     * of those of any other instances in the current program; and
415 :     * may, and typically does, vary across program invocations.
416 :     */
417 :     public SplittableRandom() {
418 :     this(nextDefaultSeed(), GAMMA_GAMMA);
419 :     }
420 :    
421 :     /**
422 :     * Constructs and returns a new SplittableRandom instance that
423 :     * shares no mutable state with this instance. However, with very
424 :     * high probability, the set of values collectively generated by
425 :     * the two objects has the same statistical properties as if the
426 :     * same quantity of values were generated by a single thread using
427 :     * a single SplittableRandom object. Either or both of the two
428 :     * objects may be further split using the {@code split()} method,
429 :     * and the same expected statistical properties apply to the
430 :     * entire set of generators constructed by such recursive
431 :     * splitting.
432 :     *
433 :     * @return the new SplittableRandom instance
434 :     */
435 :     public SplittableRandom split() {
436 :     return new SplittableRandom(nextSeed(), nextSplit);
437 :     }
438 :    
439 :     /**
440 :     * Returns a pseudorandom {@code int} value.
441 :     *
442 :     * @return a pseudorandom value
443 :     */
444 :     public int nextInt() {
445 :     return mix32(nextSeed());
446 :     }
447 :    
448 :     /**
449 :     * Returns a pseudorandom {@code int} value between 0 (inclusive)
450 :     * and the specified bound (exclusive).
451 :     *
452 :     * @param bound the bound on the random number to be returned. Must be
453 :     * positive.
454 :     * @return a pseudorandom {@code int} value between {@code 0}
455 :     * (inclusive) and the bound (exclusive).
456 :     * @exception IllegalArgumentException if the bound is not positive
457 :     */
458 :     public int nextInt(int bound) {
459 :     if (bound <= 0)
460 :     throw new IllegalArgumentException("bound must be positive");
461 :     // Specialize internalNextInt for origin 0
462 :     int r = mix32(nextSeed());
463 :     int m = bound - 1;
464 :     if ((bound & m) == 0L) // power of two
465 :     r &= m;
466 :     else { // reject over-represented candidates
467 :     for (int u = r >>> 1;
468 :     u + m - (r = u % bound) < 0L;
469 :     u = mix32(nextSeed()) >>> 1)
470 :     ;
471 :     }
472 :     return r;
473 :     }
474 :    
475 :     /**
476 :     * Returns a pseudorandom {@code int} value between the specified
477 :     * origin (inclusive) and the specified bound (exclusive).
478 :     *
479 :     * @param origin the least value returned
480 :     * @param bound the upper bound (exclusive)
481 :     * @return a pseudorandom {@code int} value between the origin
482 :     * (inclusive) and the bound (exclusive).
483 :     * @exception IllegalArgumentException if {@code origin} is greater than
484 :     * or equal to {@code bound}
485 :     */
486 :     public int nextInt(int origin, int bound) {
487 :     if (origin >= bound)
488 :     throw new IllegalArgumentException("bound must be greater than origin");
489 :     return internalNextInt(origin, bound);
490 :     }
491 :    
492 :     /**
493 :     * Returns a pseudorandom {@code long} value.
494 :     *
495 :     * @return a pseudorandom value
496 :     */
497 :     public long nextLong() {
498 :     return mix64(nextSeed());
499 :     }
500 :    
501 :     /**
502 :     * Returns a pseudorandom {@code long} value between 0 (inclusive)
503 :     * and the specified bound (exclusive).
504 :     *
505 :     * @param bound the bound on the random number to be returned. Must be
506 :     * positive.
507 :     * @return a pseudorandom {@code long} value between {@code 0}
508 :     * (inclusive) and the bound (exclusive).
509 :     * @exception IllegalArgumentException if the bound is not positive
510 :     */
511 :     public long nextLong(long bound) {
512 :     if (bound <= 0)
513 :     throw new IllegalArgumentException("bound must be positive");
514 :     // Specialize internalNextLong for origin 0
515 :     long r = mix64(nextSeed());
516 :     long m = bound - 1;
517 :     if ((bound & m) == 0L) // power of two
518 :     r &= m;
519 :     else { // reject over-represented candidates
520 :     for (long u = r >>> 1;
521 :     u + m - (r = u % bound) < 0L;
522 :     u = mix64(nextSeed()) >>> 1)
523 :     ;
524 :     }
525 :     return r;
526 :     }
527 :    
528 :     /**
529 :     * Returns a pseudorandom {@code long} value between the specified
530 :     * origin (inclusive) and the specified bound (exclusive).
531 :     *
532 :     * @param origin the least value returned
533 :     * @param bound the upper bound (exclusive)
534 :     * @return a pseudorandom {@code long} value between the origin
535 :     * (inclusive) and the bound (exclusive).
536 :     * @exception IllegalArgumentException if {@code origin} is greater than
537 :     * or equal to {@code bound}
538 :     */
539 :     public long nextLong(long origin, long bound) {
540 :     if (origin >= bound)
541 :     throw new IllegalArgumentException("bound must be greater than origin");
542 :     return internalNextLong(origin, bound);
543 :     }
544 :    
545 :     /**
546 :     * Returns a pseudorandom {@code double} value between {@code 0.0}
547 :     * (inclusive) and {@code 1.0} (exclusive).
548 :     *
549 :     * @return a pseudorandom value between {@code 0.0}
550 :     * (inclusive) and {@code 1.0} (exclusive)
551 :     */
552 :     public double nextDouble() {
553 : dl 1.5 return (nextLong() >>> 11) * DOUBLE_UNIT;
554 : dl 1.1 }
555 :    
556 :     /**
557 :     * Returns a pseudorandom {@code double} value between 0.0
558 :     * (inclusive) and the specified bound (exclusive).
559 :     *
560 :     * @param bound the bound on the random number to be returned. Must be
561 :     * positive.
562 :     * @return a pseudorandom {@code double} value between {@code 0.0}
563 :     * (inclusive) and the bound (exclusive).
564 :     * @throws IllegalArgumentException if {@code bound} is not positive
565 :     */
566 :     public double nextDouble(double bound) {
567 :     if (bound <= 0.0)
568 :     throw new IllegalArgumentException("bound must be positive");
569 :     double result = nextDouble() * bound;
570 :     return (result < bound) ? result : // correct for rounding
571 :     Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
572 :     }
573 :    
574 :     /**
575 :     * Returns a pseudorandom {@code double} value between the given
576 :     * origin (inclusive) and bound (exclusive).
577 :     *
578 :     * @param origin the least value returned
579 :     * @param bound the upper bound
580 :     * @return a pseudorandom {@code double} value between the origin
581 :     * (inclusive) and the bound (exclusive).
582 :     * @throws IllegalArgumentException if {@code origin} is greater than
583 :     * or equal to {@code bound}
584 :     */
585 :     public double nextDouble(double origin, double bound) {
586 :     if (origin >= bound)
587 :     throw new IllegalArgumentException("bound must be greater than origin");
588 :     return internalNextDouble(origin, bound);
589 :     }
590 :    
591 :     // stream methods, coded in a way intended to better isolate for
592 :     // maintenance purposes the small differences across forms.
593 :    
594 :     /**
595 :     * Returns a stream with the given {@code streamSize} number of
596 :     * pseudorandom {@code int} values.
597 :     *
598 :     * @param streamSize the number of values to generate
599 :     * @return a stream of pseudorandom {@code int} values
600 :     * @throws IllegalArgumentException if {@code streamSize} is
601 :     * less than zero
602 :     */
603 :     public IntStream ints(long streamSize) {
604 :     if (streamSize < 0L)
605 :     throw new IllegalArgumentException("negative Stream size");
606 :     return StreamSupport.intStream
607 :     (new RandomIntsSpliterator
608 :     (this, 0L, streamSize, Integer.MAX_VALUE, 0),
609 :     false);
610 :     }
611 :    
612 :     /**
613 :     * Returns an effectively unlimited stream of pseudorandom {@code int}
614 :     * values
615 :     *
616 :     * @implNote This method is implemented to be equivalent to {@code
617 :     * ints(Long.MAX_VALUE)}.
618 :     *
619 :     * @return a stream of pseudorandom {@code int} values
620 :     */
621 :     public IntStream ints() {
622 :     return StreamSupport.intStream
623 :     (new RandomIntsSpliterator
624 :     (this, 0L, Long.MAX_VALUE, Integer.MAX_VALUE, 0),
625 :     false);
626 :     }
627 :    
628 :     /**
629 :     * Returns a stream with the given {@code streamSize} number of
630 :     * pseudorandom {@code int} values, each conforming to the given
631 :     * origin and bound.
632 :     *
633 :     * @param streamSize the number of values to generate
634 :     * @param randomNumberOrigin the origin of each random value
635 :     * @param randomNumberBound the bound of each random value
636 :     * @return a stream of pseudorandom {@code int} values,
637 :     * each with the given origin and bound.
638 :     * @throws IllegalArgumentException if {@code streamSize} is
639 :     * less than zero.
640 :     * @throws IllegalArgumentException if {@code randomNumberOrigin}
641 :     * is greater than or equal to {@code randomNumberBound}
642 :     */
643 :     public IntStream ints(long streamSize, int randomNumberOrigin,
644 :     int randomNumberBound) {
645 :     if (streamSize < 0L)
646 :     throw new IllegalArgumentException("negative Stream size");
647 :     if (randomNumberOrigin >= randomNumberBound)
648 :     throw new IllegalArgumentException("bound must be greater than origin");
649 :     return StreamSupport.intStream
650 :     (new RandomIntsSpliterator
651 :     (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
652 :     false);
653 :     }
654 :    
655 :     /**
656 :     * Returns an effectively unlimited stream of pseudorandom {@code
657 :     * int} values, each conforming to the given origin and bound.
658 :     *
659 :     * @implNote This method is implemented to be equivalent to {@code
660 :     * ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
661 :     *
662 :     * @param randomNumberOrigin the origin of each random value
663 :     * @param randomNumberBound the bound of each random value
664 :     * @return a stream of pseudorandom {@code int} values,
665 :     * each with the given origin and bound.
666 :     * @throws IllegalArgumentException if {@code randomNumberOrigin}
667 :     * is greater than or equal to {@code randomNumberBound}
668 :     */
669 :     public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
670 :     if (randomNumberOrigin >= randomNumberBound)
671 :     throw new IllegalArgumentException("bound must be greater than origin");
672 :     return StreamSupport.intStream
673 :     (new RandomIntsSpliterator
674 :     (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
675 :     false);
676 :     }
677 :    
678 :     /**
679 :     * Returns a stream with the given {@code streamSize} number of
680 :     * pseudorandom {@code long} values.
681 :     *
682 :     * @param streamSize the number of values to generate
683 :     * @return a stream of {@code long} values
684 :     * @throws IllegalArgumentException if {@code streamSize} is
685 :     * less than zero
686 :     */
687 :     public LongStream longs(long streamSize) {
688 :     if (streamSize < 0L)
689 :     throw new IllegalArgumentException("negative Stream size");
690 :     return StreamSupport.longStream
691 :     (new RandomLongsSpliterator
692 :     (this, 0L, streamSize, Long.MAX_VALUE, 0L),
693 :     false);
694 :     }
695 :    
696 :     /**
697 :     * Returns an effectively unlimited stream of pseudorandom {@code long}
698 :     * values.
699 :     *
700 :     * @implNote This method is implemented to be equivalent to {@code
701 :     * longs(Long.MAX_VALUE)}.
702 :     *
703 :     * @return a stream of pseudorandom {@code long} values
704 :     */
705 :     public LongStream longs() {
706 :     return StreamSupport.longStream
707 :     (new RandomLongsSpliterator
708 :     (this, 0L, Long.MAX_VALUE, Long.MAX_VALUE, 0L),
709 :     false);
710 :     }
711 :    
712 :     /**
713 :     * Returns a stream with the given {@code streamSize} number of
714 :     * pseudorandom {@code long} values, each conforming to the
715 :     * given origin and bound.
716 :     *
717 :     * @param streamSize the number of values to generate
718 :     * @param randomNumberOrigin the origin of each random value
719 :     * @param randomNumberBound the bound of each random value
720 :     * @return a stream of pseudorandom {@code long} values,
721 :     * each with the given origin and bound.
722 :     * @throws IllegalArgumentException if {@code streamSize} is
723 :     * less than zero.
724 :     * @throws IllegalArgumentException if {@code randomNumberOrigin}
725 :     * is greater than or equal to {@code randomNumberBound}
726 :     */
727 :     public LongStream longs(long streamSize, long randomNumberOrigin,
728 :     long randomNumberBound) {
729 :     if (streamSize < 0L)
730 :     throw new IllegalArgumentException("negative Stream size");
731 :     if (randomNumberOrigin >= randomNumberBound)
732 :     throw new IllegalArgumentException("bound must be greater than origin");
733 :     return StreamSupport.longStream
734 :     (new RandomLongsSpliterator
735 :     (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
736 :     false);
737 :     }
738 :    
739 :     /**
740 :     * Returns an effectively unlimited stream of pseudorandom {@code
741 :     * long} values, each conforming to the given origin and bound.
742 :     *
743 :     * @implNote This method is implemented to be equivalent to {@code
744 :     * longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
745 :     *
746 :     * @param randomNumberOrigin the origin of each random value
747 :     * @param randomNumberBound the bound of each random value
748 :     * @return a stream of pseudorandom {@code long} values,
749 :     * each with the given origin and bound.
750 :     * @throws IllegalArgumentException if {@code randomNumberOrigin}
751 :     * is greater than or equal to {@code randomNumberBound}
752 :     */
753 :     public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
754 :     if (randomNumberOrigin >= randomNumberBound)
755 :     throw new IllegalArgumentException("bound must be greater than origin");
756 :     return StreamSupport.longStream
757 :     (new RandomLongsSpliterator
758 :     (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
759 :     false);
760 :     }
761 :    
762 :     /**
763 :     * Returns a stream with the given {@code streamSize} number of
764 : dl 1.2 * pseudorandom {@code double} values, each between {@code 0.0}
765 :     * (inclusive) and {@code 1.0} (exclusive).
766 : dl 1.1 *
767 :     * @param streamSize the number of values to generate
768 :     * @return a stream of {@code double} values
769 :     * @throws IllegalArgumentException if {@code streamSize} is
770 :     * less than zero
771 :     */
772 :     public DoubleStream doubles(long streamSize) {
773 :     if (streamSize < 0L)
774 :     throw new IllegalArgumentException("negative Stream size");
775 :     return StreamSupport.doubleStream
776 :     (new RandomDoublesSpliterator
777 :     (this, 0L, streamSize, Double.MAX_VALUE, 0.0),
778 :     false);
779 :     }
780 :    
781 :     /**
782 :     * Returns an effectively unlimited stream of pseudorandom {@code
783 : dl 1.2 * double} values, each between {@code 0.0} (inclusive) and {@code
784 :     * 1.0} (exclusive).
785 : dl 1.1 *
786 :     * @implNote This method is implemented to be equivalent to {@code
787 :     * doubles(Long.MAX_VALUE)}.
788 :     *
789 :     * @return a stream of pseudorandom {@code double} values
790 :     */
791 :     public DoubleStream doubles() {
792 :     return StreamSupport.doubleStream
793 :     (new RandomDoublesSpliterator
794 :     (this, 0L, Long.MAX_VALUE, Double.MAX_VALUE, 0.0),
795 :     false);
796 :     }
797 :    
798 :     /**
799 :     * Returns a stream with the given {@code streamSize} number of
800 :     * pseudorandom {@code double} values, each conforming to the
801 :     * given origin and bound.
802 :     *
803 :     * @param streamSize the number of values to generate
804 :     * @param randomNumberOrigin the origin of each random value
805 :     * @param randomNumberBound the bound of each random value
806 :     * @return a stream of pseudorandom {@code double} values,
807 :     * each with the given origin and bound.
808 :     * @throws IllegalArgumentException if {@code streamSize} is
809 :     * less than zero.
810 :     * @throws IllegalArgumentException if {@code randomNumberOrigin}
811 :     * is greater than or equal to {@code randomNumberBound}
812 :     */
813 :     public DoubleStream doubles(long streamSize, double randomNumberOrigin,
814 :     double randomNumberBound) {
815 :     if (streamSize < 0L)
816 :     throw new IllegalArgumentException("negative Stream size");
817 :     if (randomNumberOrigin >= randomNumberBound)
818 :     throw new IllegalArgumentException("bound must be greater than origin");
819 :     return StreamSupport.doubleStream
820 :     (new RandomDoublesSpliterator
821 :     (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
822 :     false);
823 :     }
824 :    
825 :     /**
826 :     * Returns an effectively unlimited stream of pseudorandom {@code
827 :     * double} values, each conforming to the given origin and bound.
828 :     *
829 :     * @implNote This method is implemented to be equivalent to {@code
830 :     * doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
831 :     *
832 :     * @param randomNumberOrigin the origin of each random value
833 :     * @param randomNumberBound the bound of each random value
834 :     * @return a stream of pseudorandom {@code double} values,
835 :     * each with the given origin and bound.
836 :     * @throws IllegalArgumentException if {@code randomNumberOrigin}
837 :     * is greater than or equal to {@code randomNumberBound}
838 :     */
839 :     public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
840 :     if (randomNumberOrigin >= randomNumberBound)
841 :     throw new IllegalArgumentException("bound must be greater than origin");
842 :     return StreamSupport.doubleStream
843 :     (new RandomDoublesSpliterator
844 :     (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
845 :     false);
846 :     }
847 :    
848 :     /**
849 :     * Spliterator for int streams. We multiplex the four int
850 :     * versions into one class by treating and bound < origin as
851 :     * unbounded, and also by treating "infinite" as equivalent to
852 :     * Long.MAX_VALUE. For splits, it uses the standard divide-by-two
853 :     * approach. The long and double versions of this class are
854 :     * identical except for types.
855 :     */
856 :     static class RandomIntsSpliterator implements Spliterator.OfInt {
857 :     final SplittableRandom rng;
858 :     long index;
859 :     final long fence;
860 :     final int origin;
861 :     final int bound;
862 :     RandomIntsSpliterator(SplittableRandom rng, long index, long fence,
863 :     int origin, int bound) {
864 :     this.rng = rng; this.index = index; this.fence = fence;
865 :     this.origin = origin; this.bound = bound;
866 :     }
867 :    
868 :     public RandomIntsSpliterator trySplit() {
869 :     long i = index, m = (i + fence) >>> 1;
870 :     return (m <= i) ? null :
871 :     new RandomIntsSpliterator(rng.split(), i, index = m, origin, bound);
872 :     }
873 :    
874 :     public long estimateSize() {
875 :     return fence - index;
876 :     }
877 :    
878 :     public int characteristics() {
879 :     return (Spliterator.SIZED | Spliterator.SUBSIZED |
880 : dl 1.4 Spliterator.NONNULL | Spliterator.IMMUTABLE);
881 : dl 1.1 }
882 :    
883 :     public boolean tryAdvance(IntConsumer consumer) {
884 :     if (consumer == null) throw new NullPointerException();
885 :     long i = index, f = fence;
886 :     if (i < f) {
887 :     consumer.accept(rng.internalNextInt(origin, bound));
888 :     index = i + 1;
889 :     return true;
890 :     }
891 :     return false;
892 :     }
893 :    
894 :     public void forEachRemaining(IntConsumer consumer) {
895 :     if (consumer == null) throw new NullPointerException();
896 :     long i = index, f = fence;
897 :     if (i < f) {
898 :     index = f;
899 :     int o = origin, b = bound;
900 :     do {
901 :     consumer.accept(rng.internalNextInt(o, b));
902 :     } while (++i < f);
903 :     }
904 :     }
905 :     }
906 :    
907 :     /**
908 :     * Spliterator for long streams.
909 :     */
910 :     static class RandomLongsSpliterator implements Spliterator.OfLong {
911 :     final SplittableRandom rng;
912 :     long index;
913 :     final long fence;
914 :     final long origin;
915 :     final long bound;
916 :     RandomLongsSpliterator(SplittableRandom rng, long index, long fence,
917 :     long origin, long bound) {
918 :     this.rng = rng; this.index = index; this.fence = fence;
919 :     this.origin = origin; this.bound = bound;
920 :     }
921 :    
922 :     public RandomLongsSpliterator trySplit() {
923 :     long i = index, m = (i + fence) >>> 1;
924 :     return (m <= i) ? null :
925 :     new RandomLongsSpliterator(rng.split(), i, index = m, origin, bound);
926 :     }
927 :    
928 :     public long estimateSize() {
929 :     return fence - index;
930 :     }
931 :    
932 :     public int characteristics() {
933 :     return (Spliterator.SIZED | Spliterator.SUBSIZED |
934 : dl 1.4 Spliterator.NONNULL | Spliterator.IMMUTABLE);
935 : dl 1.1 }
936 :    
937 :     public boolean tryAdvance(LongConsumer consumer) {
938 :     if (consumer == null) throw new NullPointerException();
939 :     long i = index, f = fence;
940 :     if (i < f) {
941 :     consumer.accept(rng.internalNextLong(origin, bound));
942 :     index = i + 1;
943 :     return true;
944 :     }
945 :     return false;
946 :     }
947 :    
948 :     public void forEachRemaining(LongConsumer consumer) {
949 :     if (consumer == null) throw new NullPointerException();
950 :     long i = index, f = fence;
951 :     if (i < f) {
952 :     index = f;
953 :     long o = origin, b = bound;
954 :     do {
955 :     consumer.accept(rng.internalNextLong(o, b));
956 :     } while (++i < f);
957 :     }
958 :     }
959 :    
960 :     }
961 :    
962 :     /**
963 :     * Spliterator for double streams.
964 :     */
965 :     static class RandomDoublesSpliterator implements Spliterator.OfDouble {
966 :     final SplittableRandom rng;
967 :     long index;
968 :     final long fence;
969 :     final double origin;
970 :     final double bound;
971 :     RandomDoublesSpliterator(SplittableRandom rng, long index, long fence,
972 :     double origin, double bound) {
973 :     this.rng = rng; this.index = index; this.fence = fence;
974 :     this.origin = origin; this.bound = bound;
975 :     }
976 :    
977 :     public RandomDoublesSpliterator trySplit() {
978 :     long i = index, m = (i + fence) >>> 1;
979 :     return (m <= i) ? null :
980 :     new RandomDoublesSpliterator(rng.split(), i, index = m, origin, bound);
981 :     }
982 :    
983 :     public long estimateSize() {
984 :     return fence - index;
985 :     }
986 :    
987 :     public int characteristics() {
988 :     return (Spliterator.SIZED | Spliterator.SUBSIZED |
989 : dl 1.4 Spliterator.NONNULL | Spliterator.IMMUTABLE);
990 : dl 1.1 }
991 :    
992 :     public boolean tryAdvance(DoubleConsumer consumer) {
993 :     if (consumer == null) throw new NullPointerException();
994 :     long i = index, f = fence;
995 :     if (i < f) {
996 :     consumer.accept(rng.internalNextDouble(origin, bound));
997 :     index = i + 1;
998 :     return true;
999 :     }
1000 :     return false;
1001 :     }
1002 :    
1003 :     public void forEachRemaining(DoubleConsumer consumer) {
1004 :     if (consumer == null) throw new NullPointerException();
1005 :     long i = index, f = fence;
1006 :     if (i < f) {
1007 :     index = f;
1008 :     double o = origin, b = bound;
1009 :     do {
1010 :     consumer.accept(rng.internalNextDouble(o, b));
1011 :     } while (++i < f);
1012 :     }
1013 :     }
1014 :     }
1015 :    
1016 :     }
1017 :    

Doug Lea
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