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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 :     * A generator of uniform pseudorandom values applicable for use in
40 :     * (among other contexts) isolated parallel computations that may
41 :     * generate subtasks. Class SplittableRandom supports methods for
42 : jsr166 1.3 * producing pseudorandom numbers of type {@code int}, {@code long},
43 : dl 1.1 * and {@code double} with similar usages as for class
44 :     * {@link java.util.Random} but differs in the following ways: <ul>
45 :     *
46 :     * <li>Series of generated values pass the DieHarder suite testing
47 :     * independence and uniformity properties of random number generators.
48 :     * (Most recently validated with <a
49 :     * href="http://www.phy.duke.edu/~rgb/General/dieharder.php"> version
50 :     * 3.31.1</a>.) These tests validate only the methods for certain
51 :     * types and ranges, but similar properties are expected to hold, at
52 :     * least approximately, for others as well. </li>
53 :     *
54 :     * <li> Method {@link #split} constructs and returns a new
55 :     * SplittableRandom instance that shares no mutable state with the
56 : dl 1.7 * current instance. However, with very high probability, the
57 :     * values collectively generated by the two objects have the same
58 : dl 1.1 * statistical properties as if the same quantity of values were
59 :     * generated by a single thread using a single {@code
60 :     * SplittableRandom} object. </li>
61 :     *
62 :     * <li>Instances of SplittableRandom are <em>not</em> thread-safe.
63 :     * They are designed to be split, not shared, across threads. For
64 :     * example, a {@link java.util.concurrent.ForkJoinTask
65 :     * fork/join-style} computation using random numbers might include a
66 :     * construction of the form {@code new
67 :     * Subtask(aSplittableRandom.split()).fork()}.
68 :     *
69 :     * <li>This class provides additional methods for generating random
70 :     * streams, that employ the above techniques when used in {@code
71 :     * stream.parallel()} mode.</li>
72 :     *
73 :     * </ul>
74 :     *
75 :     * @author Guy Steele
76 : dl 1.2 * @author Doug Lea
77 : dl 1.1 * @since 1.8
78 :     */
79 :     public class SplittableRandom {
80 :    
81 :     /*
82 :     * File organization: First the non-public methods that constitute
83 :     * the main algorithm, then the main public methods, followed by
84 :     * some custom spliterator classes needed for stream methods.
85 :     *
86 :     * Credits: Primary algorithm and code by Guy Steele. Stream
87 :     * support methods by Doug Lea. Documentation jointly produced
88 :     * with additional help from Brian Goetz.
89 :     */
90 :    
91 :     /*
92 :     * Implementation Overview.
93 :     *
94 :     * This algorithm was inspired by the "DotMix" algorithm by
95 :     * Leiserson, Schardl, and Sukha "Deterministic Parallel
96 :     * Random-Number Generation for Dynamic-Multithreading Platforms",
97 :     * PPoPP 2012, but improves and extends it in several ways.
98 :     *
99 : dl 1.7 * The primary update step (see method nextSeed()) is simply to
100 :     * add a constant ("gamma") to the current seed, modulo a prime
101 :     * ("George"). However, the nextLong and nextInt methods do not
102 :     * return this value, but instead the results of bit-mixing
103 :     * transformations that produce more uniformly distributed
104 :     * sequences.
105 : dl 1.1 *
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 1.7 * is scaled by a random value of 53 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 :     * Adds the given gamma value, g, to the given seed value s, mod
210 :     * George (2^64+13). We regard s and g as unsigned values
211 :     * (ranging from 0 to 2^64-1). We add g to s either once or twice
212 :     * (mod George) as necessary to produce an (unsigned) result less
213 :     * than 2^64. We require that g must be at least 13. This
214 :     * guarantees that if (s+g) mod George >= 2^64 then (s+g+g) mod
215 :     * George < 2^64; thus we need only a conditional, not a loop,
216 :     * to be sure of getting a representable value.
217 :     *
218 :     * @param s a seed value
219 :     * @param g a gamma value, 13 <= g (as unsigned)
220 :     */
221 :     private static long addGammaModGeorge(long s, long g) {
222 :     long p = s + g;
223 :     if (Long.compareUnsigned(p, g) >= 0)
224 :     return p;
225 :     long q = p - 13L;
226 :     return (Long.compareUnsigned(p, 13L) >= 0) ? q : (q + g);
227 :     }
228 :    
229 :     /**
230 :     * Returns a bit-mixed transformation of its argument.
231 :     * See above for explanation.
232 :     */
233 :     private static long mix64(long z) {
234 :     z ^= (z >>> 33);
235 :     z *= 0xff51afd7ed558ccdL;
236 :     z ^= (z >>> 33);
237 :     z *= 0xc4ceb9fe1a85ec53L;
238 :     z ^= (z >>> 33);
239 :     return z;
240 :     }
241 :    
242 :     /**
243 :     * Returns a bit-mixed int transformation of its argument.
244 :     * See above for explanation.
245 :     */
246 :     private static int mix32(long z) {
247 :     z ^= (z >>> 33);
248 :     z *= 0xc4ceb9fe1a85ec53L;
249 :     return (int)(z >>> 32);
250 :     }
251 :    
252 :     /**
253 : dl 1.7 * Internal constructor used by all other constructors and by
254 :     * method split. Establishes the initial seed for this instance,
255 :     * and uses the given splitSeed to establish gamma, as well as the
256 :     * nextSplit to use by this instance. The loop to skip ineligible
257 :     * gammas very rarely iterates, and does so at most 13 times.
258 :     */
259 :     private SplittableRandom(long seed, long splitSeed) {
260 :     this.seed = seed;
261 :     long s = splitSeed, g;
262 :     do { // ensure gamma >= 13, considered as an unsigned integer
263 :     s = addGammaModGeorge(s, GAMMA_GAMMA);
264 :     g = mix64(s);
265 :     } while (Long.compareUnsigned(g, 13L) < 0);
266 :     this.gamma = g;
267 :     this.nextSplit = s;
268 :     }
269 :    
270 :     /**
271 :     * Updates in-place and returns seed.
272 :     * See above for explanation.
273 :     */
274 :     private long nextSeed() {
275 :     return seed = addGammaModGeorge(seed, gamma);
276 :     }
277 :    
278 :     /**
279 :     * Atomically updates and returns next seed for default constructor.
280 : dl 1.1 */
281 :     private static long nextDefaultSeed() {
282 :     long oldSeed, newSeed;
283 :     do {
284 :     oldSeed = defaultSeedGenerator.get();
285 :     newSeed = addGammaModGeorge(oldSeed, DEFAULT_SEED_GAMMA);
286 :     } while (!defaultSeedGenerator.compareAndSet(oldSeed, newSeed));
287 :     return mix64(newSeed);
288 :     }
289 :    
290 :     /*
291 :     * Internal versions of nextX methods used by streams, as well as
292 :     * the public nextX(origin, bound) methods. These exist mainly to
293 :     * avoid the need for multiple versions of stream spliterators
294 :     * across the different exported forms of streams.
295 :     */
296 :    
297 :     /**
298 :     * The form of nextLong used by LongStream Spliterators. If
299 :     * origin is greater than bound, acts as unbounded form of
300 :     * nextLong, else as bounded form.
301 :     *
302 :     * @param origin the least value, unless greater than bound
303 :     * @param bound the upper bound (exclusive), must not equal origin
304 :     * @return a pseudorandom value
305 :     */
306 :     final long internalNextLong(long origin, long bound) {
307 :     /*
308 :     * Four Cases:
309 :     *
310 :     * 1. If the arguments indicate unbounded form, act as
311 :     * nextLong().
312 :     *
313 :     * 2. If the range is an exact power of two, apply the
314 :     * associated bit mask.
315 :     *
316 :     * 3. If the range is positive, loop to avoid potential bias
317 :     * when the implicit nextLong() bound (2<sup>64</sup>) is not
318 :     * evenly divisible by the range. The loop rejects candidates
319 :     * computed from otherwise over-represented values. The
320 :     * expected number of iterations under an ideal generator
321 : dl 1.4 * varies from 1 to 2, depending on the bound. The loop itself
322 :     * takes an unlovable form. Because the first candidate is
323 :     * already available, we need a break-in-the-middle
324 :     * construction, which is concisely but cryptically performed
325 :     * within the while-condition of a body-less for loop.
326 : dl 1.1 *
327 :     * 4. Otherwise, the range cannot be represented as a positive
328 : dl 1.4 * long. The loop repeatedly generates unbounded longs until
329 :     * obtaining a candidate meeting constraints (with an expected
330 :     * number of iterations of less than two).
331 : dl 1.1 */
332 :    
333 :     long r = mix64(nextSeed());
334 :     if (origin < bound) {
335 :     long n = bound - origin, m = n - 1;
336 : dl 1.7 if ((n & m) == 0L) // power of two
337 : dl 1.1 r = (r & m) + origin;
338 : dl 1.7 else if (n > 0L) { // reject over-represented candidates
339 : dl 1.1 for (long u = r >>> 1; // ensure nonnegative
340 : dl 1.7 u + m - (r = u % n) < 0L; // rejection check
341 : dl 1.1 u = mix64(nextSeed()) >>> 1) // retry
342 :     ;
343 :     r += origin;
344 :     }
345 : dl 1.7 else { // range not representable as long
346 : dl 1.1 while (r < origin || r >= bound)
347 :     r = mix64(nextSeed());
348 :     }
349 :     }
350 :     return r;
351 :     }
352 :    
353 :     /**
354 :     * The form of nextInt used by IntStream Spliterators.
355 :     * Exactly the same as long version, except for types.
356 :     *
357 :     * @param origin the least value, unless greater than bound
358 :     * @param bound the upper bound (exclusive), must not equal origin
359 :     * @return a pseudorandom value
360 :     */
361 :     final int internalNextInt(int origin, int bound) {
362 :     int r = mix32(nextSeed());
363 :     if (origin < bound) {
364 :     int n = bound - origin, m = n - 1;
365 :     if ((n & m) == 0L)
366 :     r = (r & m) + origin;
367 :     else if (n > 0) {
368 :     for (int u = r >>> 1;
369 : dl 1.7 u + m - (r = u % n) < 0;
370 : dl 1.1 u = mix32(nextSeed()) >>> 1)
371 :     ;
372 :     r += origin;
373 :     }
374 :     else {
375 :     while (r < origin || r >= bound)
376 :     r = mix32(nextSeed());
377 :     }
378 :     }
379 :     return r;
380 :     }
381 :    
382 :     /**
383 :     * The form of nextDouble used by DoubleStream Spliterators.
384 :     *
385 :     * @param origin the least value, unless greater than bound
386 :     * @param bound the upper bound (exclusive), must not equal origin
387 :     * @return a pseudorandom value
388 :     */
389 :     final double internalNextDouble(double origin, double bound) {
390 : dl 1.5 double r = (nextLong() >>> 11) * DOUBLE_UNIT;
391 : dl 1.1 if (origin < bound) {
392 :     r = r * (bound - origin) + origin;
393 : dl 1.7 if (r >= bound) // correct for rounding
394 : dl 1.1 r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
395 :     }
396 :     return r;
397 :     }
398 :    
399 :     /* ---------------- public methods ---------------- */
400 :    
401 :     /**
402 : dl 1.7 * Creates a new SplittableRandom instance using the specified
403 :     * initial seed. SplittableRandom instances created with the same
404 :     * seed generate identical sequences of values.
405 : dl 1.1 *
406 :     * @param seed the initial seed
407 :     */
408 :     public SplittableRandom(long seed) {
409 :     this(seed, 0);
410 :     }
411 :    
412 :     /**
413 :     * Creates a new SplittableRandom instance that is likely to
414 :     * generate sequences of values that are statistically independent
415 :     * of those of any other instances in the current program; and
416 :     * may, and typically does, vary across program invocations.
417 :     */
418 :     public SplittableRandom() {
419 :     this(nextDefaultSeed(), GAMMA_GAMMA);
420 :     }
421 :    
422 :     /**
423 :     * Constructs and returns a new SplittableRandom instance that
424 :     * shares no mutable state with this instance. However, with very
425 :     * high probability, the set of values collectively generated by
426 :     * the two objects has the same statistical properties as if the
427 :     * same quantity of values were generated by a single thread using
428 :     * a single SplittableRandom object. Either or both of the two
429 :     * objects may be further split using the {@code split()} method,
430 :     * and the same expected statistical properties apply to the
431 :     * entire set of generators constructed by such recursive
432 :     * splitting.
433 :     *
434 :     * @return the new SplittableRandom instance
435 :     */
436 :     public SplittableRandom split() {
437 :     return new SplittableRandom(nextSeed(), nextSplit);
438 :     }
439 :    
440 :     /**
441 :     * Returns a pseudorandom {@code int} value.
442 :     *
443 : dl 1.7 * @return a pseudorandom {@code int} value
444 : dl 1.1 */
445 :     public int nextInt() {
446 :     return mix32(nextSeed());
447 :     }
448 :    
449 :     /**
450 : dl 1.7 * Returns a pseudorandom {@code int} value between zero (inclusive)
451 : dl 1.1 * and the specified bound (exclusive).
452 :     *
453 :     * @param bound the bound on the random number to be returned. Must be
454 :     * positive.
455 : dl 1.7 * @return a pseudorandom {@code int} value between zero
456 : dl 1.1 * (inclusive) and the bound (exclusive).
457 : dl 1.7 * @throws IllegalArgumentException if the bound is less than zero
458 : dl 1.1 */
459 :     public int nextInt(int bound) {
460 :     if (bound <= 0)
461 :     throw new IllegalArgumentException("bound must be positive");
462 :     // Specialize internalNextInt for origin 0
463 :     int r = mix32(nextSeed());
464 :     int m = bound - 1;
465 :     if ((bound & m) == 0L) // power of two
466 :     r &= m;
467 :     else { // reject over-represented candidates
468 :     for (int u = r >>> 1;
469 : dl 1.7 u + m - (r = u % bound) < 0;
470 : dl 1.1 u = mix32(nextSeed()) >>> 1)
471 :     ;
472 :     }
473 :     return r;
474 :     }
475 :    
476 :     /**
477 :     * Returns a pseudorandom {@code int} value between the specified
478 :     * origin (inclusive) and the specified bound (exclusive).
479 :     *
480 :     * @param origin the least value returned
481 :     * @param bound the upper bound (exclusive)
482 :     * @return a pseudorandom {@code int} value between the origin
483 :     * (inclusive) and the bound (exclusive).
484 : dl 1.7 * @throws IllegalArgumentException if {@code origin} is greater than
485 : dl 1.1 * or equal to {@code bound}
486 :     */
487 :     public int nextInt(int origin, int bound) {
488 :     if (origin >= bound)
489 :     throw new IllegalArgumentException("bound must be greater than origin");
490 :     return internalNextInt(origin, bound);
491 :     }
492 :    
493 :     /**
494 :     * Returns a pseudorandom {@code long} value.
495 :     *
496 : dl 1.7 * @return a pseudorandom {@code long} value
497 : dl 1.1 */
498 :     public long nextLong() {
499 :     return mix64(nextSeed());
500 :     }
501 :    
502 :     /**
503 : dl 1.7 * Returns a pseudorandom {@code long} value between zero (inclusive)
504 : dl 1.1 * and the specified bound (exclusive).
505 :     *
506 :     * @param bound the bound on the random number to be returned. Must be
507 :     * positive.
508 : dl 1.7 * @return a pseudorandom {@code long} value between zero
509 : dl 1.1 * (inclusive) and the bound (exclusive).
510 : dl 1.7 * @throws IllegalArgumentException if {@code bound} is less than zero
511 : dl 1.1 */
512 :     public long nextLong(long bound) {
513 :     if (bound <= 0)
514 :     throw new IllegalArgumentException("bound must be positive");
515 :     // Specialize internalNextLong for origin 0
516 :     long r = mix64(nextSeed());
517 :     long m = bound - 1;
518 :     if ((bound & m) == 0L) // power of two
519 :     r &= m;
520 :     else { // reject over-represented candidates
521 :     for (long u = r >>> 1;
522 :     u + m - (r = u % bound) < 0L;
523 :     u = mix64(nextSeed()) >>> 1)
524 :     ;
525 :     }
526 :     return r;
527 :     }
528 :    
529 :     /**
530 :     * Returns a pseudorandom {@code long} value between the specified
531 :     * origin (inclusive) and the specified bound (exclusive).
532 :     *
533 :     * @param origin the least value returned
534 :     * @param bound the upper bound (exclusive)
535 :     * @return a pseudorandom {@code long} value between the origin
536 :     * (inclusive) and the bound (exclusive).
537 : dl 1.7 * @throws IllegalArgumentException if {@code origin} is greater than
538 : dl 1.1 * or equal to {@code bound}
539 :     */
540 :     public long nextLong(long origin, long bound) {
541 :     if (origin >= bound)
542 :     throw new IllegalArgumentException("bound must be greater than origin");
543 :     return internalNextLong(origin, bound);
544 :     }
545 :    
546 :     /**
547 : dl 1.7 * Returns a pseudorandom {@code double} value between zero
548 :     * (inclusive) and one (exclusive).
549 : dl 1.1 *
550 : dl 1.7 * @return a pseudorandom {@code double} value between zero
551 :     * (inclusive) and one (exclusive)
552 : dl 1.1 */
553 :     public double nextDouble() {
554 : dl 1.5 return (nextLong() >>> 11) * DOUBLE_UNIT;
555 : dl 1.1 }
556 :    
557 :     /**
558 :     * Returns a pseudorandom {@code double} value between 0.0
559 :     * (inclusive) and the specified bound (exclusive).
560 :     *
561 :     * @param bound the bound on the random number to be returned. Must be
562 :     * positive.
563 : dl 1.7 * @return a pseudorandom {@code double} value between zero
564 : dl 1.1 * (inclusive) and the bound (exclusive).
565 : dl 1.7 * @throws IllegalArgumentException if {@code bound} is less than zero
566 : dl 1.1 */
567 :     public double nextDouble(double bound) {
568 : dl 1.7 if (!(bound > 0.0))
569 : dl 1.1 throw new IllegalArgumentException("bound must be positive");
570 :     double result = nextDouble() * bound;
571 :     return (result < bound) ? result : // correct for rounding
572 :     Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
573 :     }
574 :    
575 :     /**
576 : dl 1.7 * Returns a pseudorandom {@code double} value between the specified
577 : dl 1.1 * origin (inclusive) and bound (exclusive).
578 :     *
579 :     * @param origin the least value returned
580 :     * @param bound the upper bound
581 :     * @return a pseudorandom {@code double} value between the origin
582 :     * (inclusive) and the bound (exclusive).
583 :     * @throws IllegalArgumentException if {@code origin} is greater than
584 :     * or equal to {@code bound}
585 :     */
586 :     public double nextDouble(double origin, double bound) {
587 : dl 1.7 if (!(origin < bound))
588 : dl 1.1 throw new IllegalArgumentException("bound must be greater than origin");
589 :     return internalNextDouble(origin, bound);
590 :     }
591 :    
592 :     // stream methods, coded in a way intended to better isolate for
593 :     // maintenance purposes the small differences across forms.
594 :    
595 :     /**
596 : dl 1.7 * Returns a stream producing the given {@code streamSize} number of
597 : dl 1.1 * pseudorandom {@code int} values.
598 :     *
599 :     * @param streamSize the number of values to generate
600 :     * @return a stream of pseudorandom {@code int} values
601 :     * @throws IllegalArgumentException if {@code streamSize} is
602 : dl 1.7 * less than zero
603 : dl 1.1 */
604 :     public IntStream ints(long streamSize) {
605 :     if (streamSize < 0L)
606 :     throw new IllegalArgumentException("negative Stream size");
607 :     return StreamSupport.intStream
608 :     (new RandomIntsSpliterator
609 :     (this, 0L, streamSize, Integer.MAX_VALUE, 0),
610 :     false);
611 :     }
612 :    
613 :     /**
614 :     * Returns an effectively unlimited stream of pseudorandom {@code int}
615 :     * values
616 :     *
617 :     * @implNote This method is implemented to be equivalent to {@code
618 :     * ints(Long.MAX_VALUE)}.
619 :     *
620 :     * @return a stream of pseudorandom {@code int} values
621 :     */
622 :     public IntStream ints() {
623 :     return StreamSupport.intStream
624 :     (new RandomIntsSpliterator
625 :     (this, 0L, Long.MAX_VALUE, Integer.MAX_VALUE, 0),
626 :     false);
627 :     }
628 :    
629 :     /**
630 : dl 1.7 * Returns a stream producing the given {@code streamSize} number of
631 : dl 1.1 * pseudorandom {@code int} values, each conforming to the given
632 :     * origin and bound.
633 :     *
634 :     * @param streamSize the number of values to generate
635 :     * @param randomNumberOrigin the origin of each random value
636 :     * @param randomNumberBound the bound of each random value
637 :     * @return a stream of pseudorandom {@code int} values,
638 : dl 1.7 * each with the given origin and bound.
639 : dl 1.1 * @throws IllegalArgumentException if {@code streamSize} is
640 : dl 1.7 * less than zero, or {@code randomNumberOrigin}
641 : dl 1.1 * 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 : dl 1.7 * each with the given origin and bound.
666 : dl 1.1 * @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 : dl 1.7 * Returns a stream producing the given {@code streamSize} number of
680 : dl 1.1 * pseudorandom {@code long} values.
681 :     *
682 :     * @param streamSize the number of values to generate
683 : dl 1.7 * @return a stream of pseudorandom {@code long} values
684 : dl 1.1 * @throws IllegalArgumentException if {@code streamSize} is
685 : dl 1.7 * less than zero
686 : dl 1.1 */
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 : dl 1.7 * Returns a stream producing the given {@code streamSize} number of
714 : dl 1.1 * 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 : dl 1.7 * each with the given origin and bound.
722 : dl 1.1 * @throws IllegalArgumentException if {@code streamSize} is
723 : dl 1.7 * less than zero, or {@code randomNumberOrigin}
724 : dl 1.1 * is greater than or equal to {@code randomNumberBound}
725 :     */
726 :     public LongStream longs(long streamSize, long randomNumberOrigin,
727 :     long randomNumberBound) {
728 :     if (streamSize < 0L)
729 :     throw new IllegalArgumentException("negative Stream size");
730 :     if (randomNumberOrigin >= randomNumberBound)
731 :     throw new IllegalArgumentException("bound must be greater than origin");
732 :     return StreamSupport.longStream
733 :     (new RandomLongsSpliterator
734 :     (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
735 :     false);
736 :     }
737 :    
738 :     /**
739 :     * Returns an effectively unlimited stream of pseudorandom {@code
740 :     * long} values, each conforming to the given origin and bound.
741 :     *
742 :     * @implNote This method is implemented to be equivalent to {@code
743 :     * longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
744 :     *
745 :     * @param randomNumberOrigin the origin of each random value
746 :     * @param randomNumberBound the bound of each random value
747 :     * @return a stream of pseudorandom {@code long} values,
748 : dl 1.7 * each with the given origin and bound.
749 : dl 1.1 * @throws IllegalArgumentException if {@code randomNumberOrigin}
750 :     * is greater than or equal to {@code randomNumberBound}
751 :     */
752 :     public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
753 :     if (randomNumberOrigin >= randomNumberBound)
754 :     throw new IllegalArgumentException("bound must be greater than origin");
755 :     return StreamSupport.longStream
756 :     (new RandomLongsSpliterator
757 :     (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
758 :     false);
759 :     }
760 :    
761 :     /**
762 : dl 1.7 * Returns a stream producing the given {@code streamSize} number of
763 :     * pseudorandom {@code double} values, each between zero
764 :     * (inclusive) and one (exclusive).
765 : dl 1.1 *
766 :     * @param streamSize the number of values to generate
767 :     * @return a stream of {@code double} values
768 :     * @throws IllegalArgumentException if {@code streamSize} is
769 : dl 1.7 * less than zero
770 : dl 1.1 */
771 :     public DoubleStream doubles(long streamSize) {
772 :     if (streamSize < 0L)
773 :     throw new IllegalArgumentException("negative Stream size");
774 :     return StreamSupport.doubleStream
775 :     (new RandomDoublesSpliterator
776 :     (this, 0L, streamSize, Double.MAX_VALUE, 0.0),
777 :     false);
778 :     }
779 :    
780 :     /**
781 :     * Returns an effectively unlimited stream of pseudorandom {@code
782 : dl 1.7 * double} values, each between zero (inclusive) and one
783 :     * (exclusive).
784 : dl 1.1 *
785 :     * @implNote This method is implemented to be equivalent to {@code
786 :     * doubles(Long.MAX_VALUE)}.
787 :     *
788 :     * @return a stream of pseudorandom {@code double} values
789 :     */
790 :     public DoubleStream doubles() {
791 :     return StreamSupport.doubleStream
792 :     (new RandomDoublesSpliterator
793 :     (this, 0L, Long.MAX_VALUE, Double.MAX_VALUE, 0.0),
794 :     false);
795 :     }
796 :    
797 :     /**
798 : dl 1.7 * Returns a stream producing the given {@code streamSize} number of
799 : dl 1.1 * pseudorandom {@code double} values, each conforming to the
800 :     * given origin and bound.
801 :     *
802 :     * @param streamSize the number of values to generate
803 :     * @param randomNumberOrigin the origin of each random value
804 :     * @param randomNumberBound the bound of each random value
805 :     * @return a stream of pseudorandom {@code double} values,
806 :     * each with the given origin and bound.
807 :     * @throws IllegalArgumentException if {@code streamSize} is
808 :     * less than zero.
809 :     * @throws IllegalArgumentException if {@code randomNumberOrigin}
810 :     * is greater than or equal to {@code randomNumberBound}
811 :     */
812 :     public DoubleStream doubles(long streamSize, double randomNumberOrigin,
813 :     double randomNumberBound) {
814 :     if (streamSize < 0L)
815 :     throw new IllegalArgumentException("negative Stream size");
816 : dl 1.7 if (!(randomNumberOrigin < randomNumberBound))
817 : dl 1.1 throw new IllegalArgumentException("bound must be greater than origin");
818 :     return StreamSupport.doubleStream
819 :     (new RandomDoublesSpliterator
820 :     (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
821 :     false);
822 :     }
823 :    
824 :     /**
825 :     * Returns an effectively unlimited stream of pseudorandom {@code
826 :     * double} values, each conforming to the given origin and bound.
827 :     *
828 :     * @implNote This method is implemented to be equivalent to {@code
829 :     * doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
830 :     *
831 :     * @param randomNumberOrigin the origin of each random value
832 :     * @param randomNumberBound the bound of each random value
833 :     * @return a stream of pseudorandom {@code double} values,
834 :     * each with the given origin and bound.
835 :     * @throws IllegalArgumentException if {@code randomNumberOrigin}
836 :     * is greater than or equal to {@code randomNumberBound}
837 :     */
838 :     public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
839 : dl 1.7 if (!(randomNumberOrigin < randomNumberBound))
840 : dl 1.1 throw new IllegalArgumentException("bound must be greater than origin");
841 :     return StreamSupport.doubleStream
842 :     (new RandomDoublesSpliterator
843 :     (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
844 :     false);
845 :     }
846 :    
847 :     /**
848 :     * Spliterator for int streams. We multiplex the four int
849 : dl 1.7 * versions into one class by treating a bound less than origin as
850 : dl 1.1 * unbounded, and also by treating "infinite" as equivalent to
851 :     * Long.MAX_VALUE. For splits, it uses the standard divide-by-two
852 :     * approach. The long and double versions of this class are
853 :     * identical except for types.
854 :     */
855 :     static class RandomIntsSpliterator implements Spliterator.OfInt {
856 :     final SplittableRandom rng;
857 :     long index;
858 :     final long fence;
859 :     final int origin;
860 :     final int bound;
861 :     RandomIntsSpliterator(SplittableRandom rng, long index, long fence,
862 :     int origin, int bound) {
863 :     this.rng = rng; this.index = index; this.fence = fence;
864 :     this.origin = origin; this.bound = bound;
865 :     }
866 :    
867 :     public RandomIntsSpliterator trySplit() {
868 :     long i = index, m = (i + fence) >>> 1;
869 :     return (m <= i) ? null :
870 :     new RandomIntsSpliterator(rng.split(), i, index = m, origin, bound);
871 :     }
872 :    
873 :     public long estimateSize() {
874 :     return fence - index;
875 :     }
876 :    
877 :     public int characteristics() {
878 :     return (Spliterator.SIZED | Spliterator.SUBSIZED |
879 : dl 1.4 Spliterator.NONNULL | Spliterator.IMMUTABLE);
880 : dl 1.1 }
881 :    
882 :     public boolean tryAdvance(IntConsumer consumer) {
883 :     if (consumer == null) throw new NullPointerException();
884 :     long i = index, f = fence;
885 :     if (i < f) {
886 :     consumer.accept(rng.internalNextInt(origin, bound));
887 :     index = i + 1;
888 :     return true;
889 :     }
890 :     return false;
891 :     }
892 :    
893 :     public void forEachRemaining(IntConsumer consumer) {
894 :     if (consumer == null) throw new NullPointerException();
895 :     long i = index, f = fence;
896 :     if (i < f) {
897 :     index = f;
898 :     int o = origin, b = bound;
899 :     do {
900 :     consumer.accept(rng.internalNextInt(o, b));
901 :     } while (++i < f);
902 :     }
903 :     }
904 :     }
905 :    
906 :     /**
907 :     * Spliterator for long streams.
908 :     */
909 :     static class RandomLongsSpliterator implements Spliterator.OfLong {
910 :     final SplittableRandom rng;
911 :     long index;
912 :     final long fence;
913 :     final long origin;
914 :     final long bound;
915 :     RandomLongsSpliterator(SplittableRandom rng, long index, long fence,
916 :     long origin, long bound) {
917 :     this.rng = rng; this.index = index; this.fence = fence;
918 :     this.origin = origin; this.bound = bound;
919 :     }
920 :    
921 :     public RandomLongsSpliterator trySplit() {
922 :     long i = index, m = (i + fence) >>> 1;
923 :     return (m <= i) ? null :
924 :     new RandomLongsSpliterator(rng.split(), i, index = m, origin, bound);
925 :     }
926 :    
927 :     public long estimateSize() {
928 :     return fence - index;
929 :     }
930 :    
931 :     public int characteristics() {
932 :     return (Spliterator.SIZED | Spliterator.SUBSIZED |
933 : dl 1.4 Spliterator.NONNULL | Spliterator.IMMUTABLE);
934 : dl 1.1 }
935 :    
936 :     public boolean tryAdvance(LongConsumer consumer) {
937 :     if (consumer == null) throw new NullPointerException();
938 :     long i = index, f = fence;
939 :     if (i < f) {
940 :     consumer.accept(rng.internalNextLong(origin, bound));
941 :     index = i + 1;
942 :     return true;
943 :     }
944 :     return false;
945 :     }
946 :    
947 :     public void forEachRemaining(LongConsumer consumer) {
948 :     if (consumer == null) throw new NullPointerException();
949 :     long i = index, f = fence;
950 :     if (i < f) {
951 :     index = f;
952 :     long o = origin, b = bound;
953 :     do {
954 :     consumer.accept(rng.internalNextLong(o, b));
955 :     } while (++i < f);
956 :     }
957 :     }
958 :    
959 :     }
960 :    
961 :     /**
962 :     * Spliterator for double streams.
963 :     */
964 :     static class RandomDoublesSpliterator implements Spliterator.OfDouble {
965 :     final SplittableRandom rng;
966 :     long index;
967 :     final long fence;
968 :     final double origin;
969 :     final double bound;
970 :     RandomDoublesSpliterator(SplittableRandom rng, long index, long fence,
971 :     double origin, double bound) {
972 :     this.rng = rng; this.index = index; this.fence = fence;
973 :     this.origin = origin; this.bound = bound;
974 :     }
975 :    
976 :     public RandomDoublesSpliterator trySplit() {
977 :     long i = index, m = (i + fence) >>> 1;
978 :     return (m <= i) ? null :
979 :     new RandomDoublesSpliterator(rng.split(), i, index = m, origin, bound);
980 :     }
981 :    
982 :     public long estimateSize() {
983 :     return fence - index;
984 :     }
985 :    
986 :     public int characteristics() {
987 :     return (Spliterator.SIZED | Spliterator.SUBSIZED |
988 : dl 1.4 Spliterator.NONNULL | Spliterator.IMMUTABLE);
989 : dl 1.1 }
990 :    
991 :     public boolean tryAdvance(DoubleConsumer consumer) {
992 :     if (consumer == null) throw new NullPointerException();
993 :     long i = index, f = fence;
994 :     if (i < f) {
995 :     consumer.accept(rng.internalNextDouble(origin, bound));
996 :     index = i + 1;
997 :     return true;
998 :     }
999 :     return false;
1000 :     }
1001 :    
1002 :     public void forEachRemaining(DoubleConsumer consumer) {
1003 :     if (consumer == null) throw new NullPointerException();
1004 :     long i = index, f = fence;
1005 :     if (i < f) {
1006 :     index = f;
1007 :     double o = origin, b = bound;
1008 :     do {
1009 :     consumer.accept(rng.internalNextDouble(o, b));
1010 :     } while (++i < f);
1011 :     }
1012 :     }
1013 :     }
1014 :    
1015 :     }
1016 :    

Doug Lea
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