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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 :     * The next seed for default constructors.
182 :     */
183 :     private static final AtomicLong defaultSeedGenerator =
184 :     new AtomicLong(System.nanoTime());
185 :    
186 :     /**
187 :     * The seed, updated only via method nextSeed.
188 :     */
189 :     private long seed;
190 :    
191 :     /**
192 :     * The constant value added to seed (mod George) on each update.
193 :     */
194 :     private final long gamma;
195 :    
196 :     /**
197 :     * The next seed to use for splits. Propagated using
198 :     * addGammaModGeorge across instances.
199 :     */
200 :     private final long nextSplit;
201 :    
202 :     /**
203 :     * Internal constructor used by all other constructors and by
204 :     * method split. Establishes the initial seed for this instance,
205 :     * and uses the given splitSeed to establish gamma, as well as the
206 :     * nextSplit to use by this instance.
207 :     */
208 :     private SplittableRandom(long seed, long splitSeed) {
209 :     this.seed = seed;
210 :     long s = splitSeed, g;
211 :     do { // ensure gamma >= 13, considered as an unsigned integer
212 :     s = addGammaModGeorge(s, GAMMA_GAMMA);
213 :     g = mix64(s);
214 :     } while (Long.compareUnsigned(g, 13L) < 0);
215 :     this.gamma = g;
216 :     this.nextSplit = s;
217 :     }
218 :    
219 :     /**
220 :     * Adds the given gamma value, g, to the given seed value s, mod
221 :     * George (2^64+13). We regard s and g as unsigned values
222 :     * (ranging from 0 to 2^64-1). We add g to s either once or twice
223 :     * (mod George) as necessary to produce an (unsigned) result less
224 :     * than 2^64. We require that g must be at least 13. This
225 :     * guarantees that if (s+g) mod George >= 2^64 then (s+g+g) mod
226 :     * George < 2^64; thus we need only a conditional, not a loop,
227 :     * to be sure of getting a representable value.
228 :     *
229 :     * @param s a seed value
230 :     * @param g a gamma value, 13 <= g (as unsigned)
231 :     */
232 :     private static long addGammaModGeorge(long s, long g) {
233 :     long p = s + g;
234 :     if (Long.compareUnsigned(p, g) >= 0)
235 :     return p;
236 :     long q = p - 13L;
237 :     return (Long.compareUnsigned(p, 13L) >= 0) ? q : (q + g);
238 :     }
239 :    
240 :     /**
241 :     * Updates in-place and returns seed.
242 :     * See above for explanation.
243 :     */
244 :     private long nextSeed() {
245 :     return seed = addGammaModGeorge(seed, gamma);
246 :     }
247 :    
248 :     /**
249 :     * Returns a bit-mixed transformation of its argument.
250 :     * See above for explanation.
251 :     */
252 :     private static long mix64(long z) {
253 :     z ^= (z >>> 33);
254 :     z *= 0xff51afd7ed558ccdL;
255 :     z ^= (z >>> 33);
256 :     z *= 0xc4ceb9fe1a85ec53L;
257 :     z ^= (z >>> 33);
258 :     return z;
259 :     }
260 :    
261 :     /**
262 :     * Returns a bit-mixed int transformation of its argument.
263 :     * See above for explanation.
264 :     */
265 :     private static int mix32(long z) {
266 :     z ^= (z >>> 33);
267 :     z *= 0xc4ceb9fe1a85ec53L;
268 :     return (int)(z >>> 32);
269 :     }
270 :    
271 :     /**
272 :     * Atomically updates and returns next seed for default constructor
273 :     */
274 :     private static long nextDefaultSeed() {
275 :     long oldSeed, newSeed;
276 :     do {
277 :     oldSeed = defaultSeedGenerator.get();
278 :     newSeed = addGammaModGeorge(oldSeed, DEFAULT_SEED_GAMMA);
279 :     } while (!defaultSeedGenerator.compareAndSet(oldSeed, newSeed));
280 :     return mix64(newSeed);
281 :     }
282 :    
283 :     /*
284 :     * Internal versions of nextX methods used by streams, as well as
285 :     * the public nextX(origin, bound) methods. These exist mainly to
286 :     * avoid the need for multiple versions of stream spliterators
287 :     * across the different exported forms of streams.
288 :     */
289 :    
290 :     /**
291 :     * The form of nextLong used by LongStream Spliterators. If
292 :     * origin is greater than bound, acts as unbounded form of
293 :     * nextLong, else as bounded form.
294 :     *
295 :     * @param origin the least value, unless greater than bound
296 :     * @param bound the upper bound (exclusive), must not equal origin
297 :     * @return a pseudorandom value
298 :     */
299 :     final long internalNextLong(long origin, long bound) {
300 :     /*
301 :     * Four Cases:
302 :     *
303 :     * 1. If the arguments indicate unbounded form, act as
304 :     * nextLong().
305 :     *
306 :     * 2. If the range is an exact power of two, apply the
307 :     * associated bit mask.
308 :     *
309 :     * 3. If the range is positive, loop to avoid potential bias
310 :     * when the implicit nextLong() bound (2<sup>64</sup>) is not
311 :     * evenly divisible by the range. The loop rejects candidates
312 :     * computed from otherwise over-represented values. The
313 :     * expected number of iterations under an ideal generator
314 : dl 1.4 * varies from 1 to 2, depending on the bound. The loop itself
315 :     * takes an unlovable form. Because the first candidate is
316 :     * already available, we need a break-in-the-middle
317 :     * construction, which is concisely but cryptically performed
318 :     * within the while-condition of a body-less for loop.
319 : dl 1.1 *
320 :     * 4. Otherwise, the range cannot be represented as a positive
321 : dl 1.4 * long. The loop repeatedly generates unbounded longs until
322 :     * obtaining a candidate meeting constraints (with an expected
323 :     * number of iterations of less than two).
324 : dl 1.1 */
325 :    
326 :     long r = mix64(nextSeed());
327 :     if (origin < bound) {
328 :     long n = bound - origin, m = n - 1;
329 :     if ((n & m) == 0L) // power of two
330 :     r = (r & m) + origin;
331 :     else if (n > 0) { // reject over-represented candidates
332 :     for (long u = r >>> 1; // ensure nonnegative
333 :     u + m - (r = u % n) < 0L; // reject
334 :     u = mix64(nextSeed()) >>> 1) // retry
335 :     ;
336 :     r += origin;
337 :     }
338 :     else { // range not representable as long
339 :     while (r < origin || r >= bound)
340 :     r = mix64(nextSeed());
341 :     }
342 :     }
343 :     return r;
344 :     }
345 :    
346 :     /**
347 :     * The form of nextInt used by IntStream Spliterators.
348 :     * Exactly the same as long version, except for types.
349 :     *
350 :     * @param origin the least value, unless greater than bound
351 :     * @param bound the upper bound (exclusive), must not equal origin
352 :     * @return a pseudorandom value
353 :     */
354 :     final int internalNextInt(int origin, int bound) {
355 :     int r = mix32(nextSeed());
356 :     if (origin < bound) {
357 :     int n = bound - origin, m = n - 1;
358 :     if ((n & m) == 0L)
359 :     r = (r & m) + origin;
360 :     else if (n > 0) {
361 :     for (int u = r >>> 1;
362 :     u + m - (r = u % n) < 0L;
363 :     u = mix32(nextSeed()) >>> 1)
364 :     ;
365 :     r += origin;
366 :     }
367 :     else {
368 :     while (r < origin || r >= bound)
369 :     r = mix32(nextSeed());
370 :     }
371 :     }
372 :     return r;
373 :     }
374 :    
375 :     /**
376 :     * The form of nextDouble used by DoubleStream Spliterators.
377 :     *
378 :     * @param origin the least value, unless greater than bound
379 :     * @param bound the upper bound (exclusive), must not equal origin
380 :     * @return a pseudorandom value
381 :     */
382 :     final double internalNextDouble(double origin, double bound) {
383 :     long bits = (1023L << 52) | (nextLong() >>> 12);
384 :     double r = Double.longBitsToDouble(bits) - 1.0;
385 :     if (origin < bound) {
386 :     r = r * (bound - origin) + origin;
387 :     if (r == bound) // correct for rounding
388 :     r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
389 :     }
390 :     return r;
391 :     }
392 :    
393 :     /* ---------------- public methods ---------------- */
394 :    
395 :     /**
396 :     * Creates a new SplittableRandom instance using the given initial
397 :     * seed. Two SplittableRandom instances created with the same seed
398 :     * generate identical sequences of values.
399 :     *
400 :     * @param seed the initial seed
401 :     */
402 :     public SplittableRandom(long seed) {
403 :     this(seed, 0);
404 :     }
405 :    
406 :     /**
407 :     * Creates a new SplittableRandom instance that is likely to
408 :     * generate sequences of values that are statistically independent
409 :     * of those of any other instances in the current program; and
410 :     * may, and typically does, vary across program invocations.
411 :     */
412 :     public SplittableRandom() {
413 :     this(nextDefaultSeed(), GAMMA_GAMMA);
414 :     }
415 :    
416 :     /**
417 :     * Constructs and returns a new SplittableRandom instance that
418 :     * shares no mutable state with this instance. However, with very
419 :     * high probability, the set of values collectively generated by
420 :     * the two objects has the same statistical properties as if the
421 :     * same quantity of values were generated by a single thread using
422 :     * a single SplittableRandom object. Either or both of the two
423 :     * objects may be further split using the {@code split()} method,
424 :     * and the same expected statistical properties apply to the
425 :     * entire set of generators constructed by such recursive
426 :     * splitting.
427 :     *
428 :     * @return the new SplittableRandom instance
429 :     */
430 :     public SplittableRandom split() {
431 :     return new SplittableRandom(nextSeed(), nextSplit);
432 :     }
433 :    
434 :     /**
435 :     * Returns a pseudorandom {@code int} value.
436 :     *
437 :     * @return a pseudorandom value
438 :     */
439 :     public int nextInt() {
440 :     return mix32(nextSeed());
441 :     }
442 :    
443 :     /**
444 :     * Returns a pseudorandom {@code int} value between 0 (inclusive)
445 :     * and the specified bound (exclusive).
446 :     *
447 :     * @param bound the bound on the random number to be returned. Must be
448 :     * positive.
449 :     * @return a pseudorandom {@code int} value between {@code 0}
450 :     * (inclusive) and the bound (exclusive).
451 :     * @exception IllegalArgumentException if the bound is not positive
452 :     */
453 :     public int nextInt(int bound) {
454 :     if (bound <= 0)
455 :     throw new IllegalArgumentException("bound must be positive");
456 :     // Specialize internalNextInt for origin 0
457 :     int r = mix32(nextSeed());
458 :     int m = bound - 1;
459 :     if ((bound & m) == 0L) // power of two
460 :     r &= m;
461 :     else { // reject over-represented candidates
462 :     for (int u = r >>> 1;
463 :     u + m - (r = u % bound) < 0L;
464 :     u = mix32(nextSeed()) >>> 1)
465 :     ;
466 :     }
467 :     return r;
468 :     }
469 :    
470 :     /**
471 :     * Returns a pseudorandom {@code int} value between the specified
472 :     * origin (inclusive) and the specified bound (exclusive).
473 :     *
474 :     * @param origin the least value returned
475 :     * @param bound the upper bound (exclusive)
476 :     * @return a pseudorandom {@code int} value between the origin
477 :     * (inclusive) and the bound (exclusive).
478 :     * @exception IllegalArgumentException if {@code origin} is greater than
479 :     * or equal to {@code bound}
480 :     */
481 :     public int nextInt(int origin, int bound) {
482 :     if (origin >= bound)
483 :     throw new IllegalArgumentException("bound must be greater than origin");
484 :     return internalNextInt(origin, bound);
485 :     }
486 :    
487 :     /**
488 :     * Returns a pseudorandom {@code long} value.
489 :     *
490 :     * @return a pseudorandom value
491 :     */
492 :     public long nextLong() {
493 :     return mix64(nextSeed());
494 :     }
495 :    
496 :     /**
497 :     * Returns a pseudorandom {@code long} value between 0 (inclusive)
498 :     * and the specified bound (exclusive).
499 :     *
500 :     * @param bound the bound on the random number to be returned. Must be
501 :     * positive.
502 :     * @return a pseudorandom {@code long} value between {@code 0}
503 :     * (inclusive) and the bound (exclusive).
504 :     * @exception IllegalArgumentException if the bound is not positive
505 :     */
506 :     public long nextLong(long bound) {
507 :     if (bound <= 0)
508 :     throw new IllegalArgumentException("bound must be positive");
509 :     // Specialize internalNextLong for origin 0
510 :     long r = mix64(nextSeed());
511 :     long m = bound - 1;
512 :     if ((bound & m) == 0L) // power of two
513 :     r &= m;
514 :     else { // reject over-represented candidates
515 :     for (long u = r >>> 1;
516 :     u + m - (r = u % bound) < 0L;
517 :     u = mix64(nextSeed()) >>> 1)
518 :     ;
519 :     }
520 :     return r;
521 :     }
522 :    
523 :     /**
524 :     * Returns a pseudorandom {@code long} value between the specified
525 :     * origin (inclusive) and the specified bound (exclusive).
526 :     *
527 :     * @param origin the least value returned
528 :     * @param bound the upper bound (exclusive)
529 :     * @return a pseudorandom {@code long} value between the origin
530 :     * (inclusive) and the bound (exclusive).
531 :     * @exception IllegalArgumentException if {@code origin} is greater than
532 :     * or equal to {@code bound}
533 :     */
534 :     public long nextLong(long origin, long bound) {
535 :     if (origin >= bound)
536 :     throw new IllegalArgumentException("bound must be greater than origin");
537 :     return internalNextLong(origin, bound);
538 :     }
539 :    
540 :     /**
541 :     * Returns a pseudorandom {@code double} value between {@code 0.0}
542 :     * (inclusive) and {@code 1.0} (exclusive).
543 :     *
544 :     * @return a pseudorandom value between {@code 0.0}
545 :     * (inclusive) and {@code 1.0} (exclusive)
546 :     */
547 :     public double nextDouble() {
548 :     long bits = (1023L << 52) | (nextLong() >>> 12);
549 :     return Double.longBitsToDouble(bits) - 1.0;
550 :     }
551 :    
552 :     /**
553 :     * Returns a pseudorandom {@code double} value between 0.0
554 :     * (inclusive) and the specified bound (exclusive).
555 :     *
556 :     * @param bound the bound on the random number to be returned. Must be
557 :     * positive.
558 :     * @return a pseudorandom {@code double} value between {@code 0.0}
559 :     * (inclusive) and the bound (exclusive).
560 :     * @throws IllegalArgumentException if {@code bound} is not positive
561 :     */
562 :     public double nextDouble(double bound) {
563 :     if (bound <= 0.0)
564 :     throw new IllegalArgumentException("bound must be positive");
565 :     double result = nextDouble() * bound;
566 :     return (result < bound) ? result : // correct for rounding
567 :     Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
568 :     }
569 :    
570 :     /**
571 :     * Returns a pseudorandom {@code double} value between the given
572 :     * origin (inclusive) and bound (exclusive).
573 :     *
574 :     * @param origin the least value returned
575 :     * @param bound the upper bound
576 :     * @return a pseudorandom {@code double} value between the origin
577 :     * (inclusive) and the bound (exclusive).
578 :     * @throws IllegalArgumentException if {@code origin} is greater than
579 :     * or equal to {@code bound}
580 :     */
581 :     public double nextDouble(double origin, double bound) {
582 :     if (origin >= bound)
583 :     throw new IllegalArgumentException("bound must be greater than origin");
584 :     return internalNextDouble(origin, bound);
585 :     }
586 :    
587 :     // stream methods, coded in a way intended to better isolate for
588 :     // maintenance purposes the small differences across forms.
589 :    
590 :     /**
591 :     * Returns a stream with the given {@code streamSize} number of
592 :     * pseudorandom {@code int} values.
593 :     *
594 :     * @param streamSize the number of values to generate
595 :     * @return a stream of pseudorandom {@code int} values
596 :     * @throws IllegalArgumentException if {@code streamSize} is
597 :     * less than zero
598 :     */
599 :     public IntStream ints(long streamSize) {
600 :     if (streamSize < 0L)
601 :     throw new IllegalArgumentException("negative Stream size");
602 :     return StreamSupport.intStream
603 :     (new RandomIntsSpliterator
604 :     (this, 0L, streamSize, Integer.MAX_VALUE, 0),
605 :     false);
606 :     }
607 :    
608 :     /**
609 :     * Returns an effectively unlimited stream of pseudorandom {@code int}
610 :     * values
611 :     *
612 :     * @implNote This method is implemented to be equivalent to {@code
613 :     * ints(Long.MAX_VALUE)}.
614 :     *
615 :     * @return a stream of pseudorandom {@code int} values
616 :     */
617 :     public IntStream ints() {
618 :     return StreamSupport.intStream
619 :     (new RandomIntsSpliterator
620 :     (this, 0L, Long.MAX_VALUE, Integer.MAX_VALUE, 0),
621 :     false);
622 :     }
623 :    
624 :     /**
625 :     * Returns a stream with the given {@code streamSize} number of
626 :     * pseudorandom {@code int} values, each conforming to the given
627 :     * origin and bound.
628 :     *
629 :     * @param streamSize the number of values to generate
630 :     * @param randomNumberOrigin the origin of each random value
631 :     * @param randomNumberBound the bound of each random value
632 :     * @return a stream of pseudorandom {@code int} values,
633 :     * each with the given origin and bound.
634 :     * @throws IllegalArgumentException if {@code streamSize} is
635 :     * less than zero.
636 :     * @throws IllegalArgumentException if {@code randomNumberOrigin}
637 :     * is greater than or equal to {@code randomNumberBound}
638 :     */
639 :     public IntStream ints(long streamSize, int randomNumberOrigin,
640 :     int randomNumberBound) {
641 :     if (streamSize < 0L)
642 :     throw new IllegalArgumentException("negative Stream size");
643 :     if (randomNumberOrigin >= randomNumberBound)
644 :     throw new IllegalArgumentException("bound must be greater than origin");
645 :     return StreamSupport.intStream
646 :     (new RandomIntsSpliterator
647 :     (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
648 :     false);
649 :     }
650 :    
651 :     /**
652 :     * Returns an effectively unlimited stream of pseudorandom {@code
653 :     * int} values, each conforming to the given origin and bound.
654 :     *
655 :     * @implNote This method is implemented to be equivalent to {@code
656 :     * ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
657 :     *
658 :     * @param randomNumberOrigin the origin of each random value
659 :     * @param randomNumberBound the bound of each random value
660 :     * @return a stream of pseudorandom {@code int} values,
661 :     * each with the given origin and bound.
662 :     * @throws IllegalArgumentException if {@code randomNumberOrigin}
663 :     * is greater than or equal to {@code randomNumberBound}
664 :     */
665 :     public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
666 :     if (randomNumberOrigin >= randomNumberBound)
667 :     throw new IllegalArgumentException("bound must be greater than origin");
668 :     return StreamSupport.intStream
669 :     (new RandomIntsSpliterator
670 :     (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
671 :     false);
672 :     }
673 :    
674 :     /**
675 :     * Returns a stream with the given {@code streamSize} number of
676 :     * pseudorandom {@code long} values.
677 :     *
678 :     * @param streamSize the number of values to generate
679 :     * @return a stream of {@code long} values
680 :     * @throws IllegalArgumentException if {@code streamSize} is
681 :     * less than zero
682 :     */
683 :     public LongStream longs(long streamSize) {
684 :     if (streamSize < 0L)
685 :     throw new IllegalArgumentException("negative Stream size");
686 :     return StreamSupport.longStream
687 :     (new RandomLongsSpliterator
688 :     (this, 0L, streamSize, Long.MAX_VALUE, 0L),
689 :     false);
690 :     }
691 :    
692 :     /**
693 :     * Returns an effectively unlimited stream of pseudorandom {@code long}
694 :     * values.
695 :     *
696 :     * @implNote This method is implemented to be equivalent to {@code
697 :     * longs(Long.MAX_VALUE)}.
698 :     *
699 :     * @return a stream of pseudorandom {@code long} values
700 :     */
701 :     public LongStream longs() {
702 :     return StreamSupport.longStream
703 :     (new RandomLongsSpliterator
704 :     (this, 0L, Long.MAX_VALUE, Long.MAX_VALUE, 0L),
705 :     false);
706 :     }
707 :    
708 :     /**
709 :     * Returns a stream with the given {@code streamSize} number of
710 :     * pseudorandom {@code long} values, each conforming to the
711 :     * given origin and bound.
712 :     *
713 :     * @param streamSize the number of values to generate
714 :     * @param randomNumberOrigin the origin of each random value
715 :     * @param randomNumberBound the bound of each random value
716 :     * @return a stream of pseudorandom {@code long} values,
717 :     * each with the given origin and bound.
718 :     * @throws IllegalArgumentException if {@code streamSize} is
719 :     * less than zero.
720 :     * @throws IllegalArgumentException if {@code randomNumberOrigin}
721 :     * is greater than or equal to {@code randomNumberBound}
722 :     */
723 :     public LongStream longs(long streamSize, long randomNumberOrigin,
724 :     long randomNumberBound) {
725 :     if (streamSize < 0L)
726 :     throw new IllegalArgumentException("negative Stream size");
727 :     if (randomNumberOrigin >= randomNumberBound)
728 :     throw new IllegalArgumentException("bound must be greater than origin");
729 :     return StreamSupport.longStream
730 :     (new RandomLongsSpliterator
731 :     (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
732 :     false);
733 :     }
734 :    
735 :     /**
736 :     * Returns an effectively unlimited stream of pseudorandom {@code
737 :     * long} values, each conforming to the given origin and bound.
738 :     *
739 :     * @implNote This method is implemented to be equivalent to {@code
740 :     * longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
741 :     *
742 :     * @param randomNumberOrigin the origin of each random value
743 :     * @param randomNumberBound the bound of each random value
744 :     * @return a stream of pseudorandom {@code long} values,
745 :     * each with the given origin and bound.
746 :     * @throws IllegalArgumentException if {@code randomNumberOrigin}
747 :     * is greater than or equal to {@code randomNumberBound}
748 :     */
749 :     public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
750 :     if (randomNumberOrigin >= randomNumberBound)
751 :     throw new IllegalArgumentException("bound must be greater than origin");
752 :     return StreamSupport.longStream
753 :     (new RandomLongsSpliterator
754 :     (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
755 :     false);
756 :     }
757 :    
758 :     /**
759 :     * Returns a stream with the given {@code streamSize} number of
760 : dl 1.2 * pseudorandom {@code double} values, each between {@code 0.0}
761 :     * (inclusive) and {@code 1.0} (exclusive).
762 : dl 1.1 *
763 :     * @param streamSize the number of values to generate
764 :     * @return a stream of {@code double} values
765 :     * @throws IllegalArgumentException if {@code streamSize} is
766 :     * less than zero
767 :     */
768 :     public DoubleStream doubles(long streamSize) {
769 :     if (streamSize < 0L)
770 :     throw new IllegalArgumentException("negative Stream size");
771 :     return StreamSupport.doubleStream
772 :     (new RandomDoublesSpliterator
773 :     (this, 0L, streamSize, Double.MAX_VALUE, 0.0),
774 :     false);
775 :     }
776 :    
777 :     /**
778 :     * Returns an effectively unlimited stream of pseudorandom {@code
779 : dl 1.2 * double} values, each between {@code 0.0} (inclusive) and {@code
780 :     * 1.0} (exclusive).
781 : dl 1.1 *
782 :     * @implNote This method is implemented to be equivalent to {@code
783 :     * doubles(Long.MAX_VALUE)}.
784 :     *
785 :     * @return a stream of pseudorandom {@code double} values
786 :     */
787 :     public DoubleStream doubles() {
788 :     return StreamSupport.doubleStream
789 :     (new RandomDoublesSpliterator
790 :     (this, 0L, Long.MAX_VALUE, Double.MAX_VALUE, 0.0),
791 :     false);
792 :     }
793 :    
794 :     /**
795 :     * Returns a stream with the given {@code streamSize} number of
796 :     * pseudorandom {@code double} values, each conforming to the
797 :     * given origin and bound.
798 :     *
799 :     * @param streamSize the number of values to generate
800 :     * @param randomNumberOrigin the origin of each random value
801 :     * @param randomNumberBound the bound of each random value
802 :     * @return a stream of pseudorandom {@code double} values,
803 :     * each with the given origin and bound.
804 :     * @throws IllegalArgumentException if {@code streamSize} is
805 :     * less than zero.
806 :     * @throws IllegalArgumentException if {@code randomNumberOrigin}
807 :     * is greater than or equal to {@code randomNumberBound}
808 :     */
809 :     public DoubleStream doubles(long streamSize, double randomNumberOrigin,
810 :     double randomNumberBound) {
811 :     if (streamSize < 0L)
812 :     throw new IllegalArgumentException("negative Stream size");
813 :     if (randomNumberOrigin >= randomNumberBound)
814 :     throw new IllegalArgumentException("bound must be greater than origin");
815 :     return StreamSupport.doubleStream
816 :     (new RandomDoublesSpliterator
817 :     (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
818 :     false);
819 :     }
820 :    
821 :     /**
822 :     * Returns an effectively unlimited stream of pseudorandom {@code
823 :     * double} values, each conforming to the given origin and bound.
824 :     *
825 :     * @implNote This method is implemented to be equivalent to {@code
826 :     * doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
827 :     *
828 :     * @param randomNumberOrigin the origin of each random value
829 :     * @param randomNumberBound the bound of each random value
830 :     * @return a stream of pseudorandom {@code double} values,
831 :     * each with the given origin and bound.
832 :     * @throws IllegalArgumentException if {@code randomNumberOrigin}
833 :     * is greater than or equal to {@code randomNumberBound}
834 :     */
835 :     public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
836 :     if (randomNumberOrigin >= randomNumberBound)
837 :     throw new IllegalArgumentException("bound must be greater than origin");
838 :     return StreamSupport.doubleStream
839 :     (new RandomDoublesSpliterator
840 :     (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
841 :     false);
842 :     }
843 :    
844 :     /**
845 :     * Spliterator for int streams. We multiplex the four int
846 :     * versions into one class by treating and bound < origin as
847 :     * unbounded, and also by treating "infinite" as equivalent to
848 :     * Long.MAX_VALUE. For splits, it uses the standard divide-by-two
849 :     * approach. The long and double versions of this class are
850 :     * identical except for types.
851 :     */
852 :     static class RandomIntsSpliterator implements Spliterator.OfInt {
853 :     final SplittableRandom rng;
854 :     long index;
855 :     final long fence;
856 :     final int origin;
857 :     final int bound;
858 :     RandomIntsSpliterator(SplittableRandom rng, long index, long fence,
859 :     int origin, int bound) {
860 :     this.rng = rng; this.index = index; this.fence = fence;
861 :     this.origin = origin; this.bound = bound;
862 :     }
863 :    
864 :     public RandomIntsSpliterator trySplit() {
865 :     long i = index, m = (i + fence) >>> 1;
866 :     return (m <= i) ? null :
867 :     new RandomIntsSpliterator(rng.split(), i, index = m, origin, bound);
868 :     }
869 :    
870 :     public long estimateSize() {
871 :     return fence - index;
872 :     }
873 :    
874 :     public int characteristics() {
875 :     return (Spliterator.SIZED | Spliterator.SUBSIZED |
876 : dl 1.4 Spliterator.NONNULL | Spliterator.IMMUTABLE);
877 : dl 1.1 }
878 :    
879 :     public boolean tryAdvance(IntConsumer consumer) {
880 :     if (consumer == null) throw new NullPointerException();
881 :     long i = index, f = fence;
882 :     if (i < f) {
883 :     consumer.accept(rng.internalNextInt(origin, bound));
884 :     index = i + 1;
885 :     return true;
886 :     }
887 :     return false;
888 :     }
889 :    
890 :     public void forEachRemaining(IntConsumer consumer) {
891 :     if (consumer == null) throw new NullPointerException();
892 :     long i = index, f = fence;
893 :     if (i < f) {
894 :     index = f;
895 :     int o = origin, b = bound;
896 :     do {
897 :     consumer.accept(rng.internalNextInt(o, b));
898 :     } while (++i < f);
899 :     }
900 :     }
901 :     }
902 :    
903 :     /**
904 :     * Spliterator for long streams.
905 :     */
906 :     static class RandomLongsSpliterator implements Spliterator.OfLong {
907 :     final SplittableRandom rng;
908 :     long index;
909 :     final long fence;
910 :     final long origin;
911 :     final long bound;
912 :     RandomLongsSpliterator(SplittableRandom rng, long index, long fence,
913 :     long origin, long bound) {
914 :     this.rng = rng; this.index = index; this.fence = fence;
915 :     this.origin = origin; this.bound = bound;
916 :     }
917 :    
918 :     public RandomLongsSpliterator trySplit() {
919 :     long i = index, m = (i + fence) >>> 1;
920 :     return (m <= i) ? null :
921 :     new RandomLongsSpliterator(rng.split(), i, index = m, origin, bound);
922 :     }
923 :    
924 :     public long estimateSize() {
925 :     return fence - index;
926 :     }
927 :    
928 :     public int characteristics() {
929 :     return (Spliterator.SIZED | Spliterator.SUBSIZED |
930 : dl 1.4 Spliterator.NONNULL | Spliterator.IMMUTABLE);
931 : dl 1.1 }
932 :    
933 :     public boolean tryAdvance(LongConsumer consumer) {
934 :     if (consumer == null) throw new NullPointerException();
935 :     long i = index, f = fence;
936 :     if (i < f) {
937 :     consumer.accept(rng.internalNextLong(origin, bound));
938 :     index = i + 1;
939 :     return true;
940 :     }
941 :     return false;
942 :     }
943 :    
944 :     public void forEachRemaining(LongConsumer consumer) {
945 :     if (consumer == null) throw new NullPointerException();
946 :     long i = index, f = fence;
947 :     if (i < f) {
948 :     index = f;
949 :     long o = origin, b = bound;
950 :     do {
951 :     consumer.accept(rng.internalNextLong(o, b));
952 :     } while (++i < f);
953 :     }
954 :     }
955 :    
956 :     }
957 :    
958 :     /**
959 :     * Spliterator for double streams.
960 :     */
961 :     static class RandomDoublesSpliterator implements Spliterator.OfDouble {
962 :     final SplittableRandom rng;
963 :     long index;
964 :     final long fence;
965 :     final double origin;
966 :     final double bound;
967 :     RandomDoublesSpliterator(SplittableRandom rng, long index, long fence,
968 :     double origin, double bound) {
969 :     this.rng = rng; this.index = index; this.fence = fence;
970 :     this.origin = origin; this.bound = bound;
971 :     }
972 :    
973 :     public RandomDoublesSpliterator trySplit() {
974 :     long i = index, m = (i + fence) >>> 1;
975 :     return (m <= i) ? null :
976 :     new RandomDoublesSpliterator(rng.split(), i, index = m, origin, bound);
977 :     }
978 :    
979 :     public long estimateSize() {
980 :     return fence - index;
981 :     }
982 :    
983 :     public int characteristics() {
984 :     return (Spliterator.SIZED | Spliterator.SUBSIZED |
985 : dl 1.4 Spliterator.NONNULL | Spliterator.IMMUTABLE);
986 : dl 1.1 }
987 :    
988 :     public boolean tryAdvance(DoubleConsumer consumer) {
989 :     if (consumer == null) throw new NullPointerException();
990 :     long i = index, f = fence;
991 :     if (i < f) {
992 :     consumer.accept(rng.internalNextDouble(origin, bound));
993 :     index = i + 1;
994 :     return true;
995 :     }
996 :     return false;
997 :     }
998 :    
999 :     public void forEachRemaining(DoubleConsumer consumer) {
1000 :     if (consumer == null) throw new NullPointerException();
1001 :     long i = index, f = fence;
1002 :     if (i < f) {
1003 :     index = f;
1004 :     double o = origin, b = bound;
1005 :     do {
1006 :     consumer.accept(rng.internalNextDouble(o, b));
1007 :     } while (++i < f);
1008 :     }
1009 :     }
1010 :     }
1011 :    
1012 :     }
1013 :    

Doug Lea
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