[cvs] / jsr166 / src / main / java / util / SplittableRandom.java Repository:
ViewVC logotype

Annotation of /jsr166/src/main/java/util/SplittableRandom.java

Parent Directory Parent Directory | Revision Log Revision Log


Revision 1.11 - (view) (download)

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 : jsr166 1.9 * {@link java.util.Random} but differs in the following ways:
45 :     *
46 :     * <ul>
47 : dl 1.1 *
48 :     * <li>Series of generated values pass the DieHarder suite testing
49 :     * independence and uniformity properties of random number generators.
50 :     * (Most recently validated with <a
51 :     * href="http://www.phy.duke.edu/~rgb/General/dieharder.php"> version
52 :     * 3.31.1</a>.) These tests validate only the methods for certain
53 :     * types and ranges, but similar properties are expected to hold, at
54 : dl 1.11 * least approximately, for others as well. The <em>period</em>
55 :     * (length of any series of generated values before it repeats) is at
56 :     * least 2<sup>64</sup>. </li>
57 : dl 1.1 *
58 :     * <li> Method {@link #split} constructs and returns a new
59 :     * SplittableRandom instance that shares no mutable state with the
60 : dl 1.7 * current instance. However, with very high probability, the
61 :     * values collectively generated by the two objects have the same
62 : dl 1.1 * statistical properties as if the same quantity of values were
63 :     * generated by a single thread using a single {@code
64 :     * SplittableRandom} object. </li>
65 :     *
66 :     * <li>Instances of SplittableRandom are <em>not</em> thread-safe.
67 :     * They are designed to be split, not shared, across threads. For
68 :     * example, a {@link java.util.concurrent.ForkJoinTask
69 :     * fork/join-style} computation using random numbers might include a
70 :     * construction of the form {@code new
71 :     * Subtask(aSplittableRandom.split()).fork()}.
72 :     *
73 :     * <li>This class provides additional methods for generating random
74 :     * streams, that employ the above techniques when used in {@code
75 :     * stream.parallel()} mode.</li>
76 :     *
77 :     * </ul>
78 :     *
79 :     * @author Guy Steele
80 : dl 1.2 * @author Doug Lea
81 : dl 1.1 * @since 1.8
82 :     */
83 :     public class SplittableRandom {
84 :    
85 :     /*
86 :     * File organization: First the non-public methods that constitute
87 :     * the main algorithm, then the main public methods, followed by
88 :     * some custom spliterator classes needed for stream methods.
89 :     *
90 :     * Credits: Primary algorithm and code by Guy Steele. Stream
91 :     * support methods by Doug Lea. Documentation jointly produced
92 :     * with additional help from Brian Goetz.
93 :     */
94 :    
95 :     /*
96 :     * Implementation Overview.
97 :     *
98 :     * This algorithm was inspired by the "DotMix" algorithm by
99 :     * Leiserson, Schardl, and Sukha "Deterministic Parallel
100 :     * Random-Number Generation for Dynamic-Multithreading Platforms",
101 :     * PPoPP 2012, but improves and extends it in several ways.
102 :     *
103 : dl 1.7 * The primary update step (see method nextSeed()) is simply to
104 :     * add a constant ("gamma") to the current seed, modulo a prime
105 :     * ("George"). However, the nextLong and nextInt methods do not
106 :     * return this value, but instead the results of bit-mixing
107 :     * transformations that produce more uniformly distributed
108 :     * sequences.
109 : dl 1.1 *
110 :     * "George" is the otherwise nameless (because it cannot be
111 :     * represented) prime number 2^64+13. Using a prime number larger
112 :     * than can fit in a long ensures that all possible long values
113 :     * can occur, plus 13 others that just get skipped over when they
114 :     * are encountered; see method addGammaModGeorge. For this to
115 :     * work, initial gamma values must be at least 13.
116 :     *
117 :     * The value of gamma differs for each instance across a series of
118 :     * splits, and is generated using a slightly stripped-down variant
119 :     * of the same algorithm, but operating across calls to split(),
120 : dl 1.2 * not calls to nextSeed(): Each instance carries the state of
121 : dl 1.1 * this generator as nextSplit, and uses mix64(nextSplit) as its
122 :     * own gamma value. Computations of gammas themselves use a fixed
123 :     * constant as the second argument to the addGammaModGeorge
124 :     * function, GAMMA_GAMMA, a "genuinely random" number from a
125 :     * radioactive decay reading (obtained from
126 :     * http://www.fourmilab.ch/hotbits/) meeting the above range
127 :     * constraint. Using a fixed constant maintains the invariant that
128 :     * the value of gamma is the same for every instance that is at
129 :     * the same split-distance from their common root. (Note: there is
130 :     * nothing especially magic about obtaining this constant from a
131 :     * "truly random" physical source rather than just choosing one
132 :     * arbitrarily; using "hotbits" was merely an aesthetically pleasing
133 :     * choice. In either case, good statistical behavior of the
134 :     * algorithm should be, and was, verified by using the DieHarder
135 :     * test suite.)
136 :     *
137 :     * The mix64 bit-mixing function called by nextLong and other
138 :     * methods computes the same value as the "64-bit finalizer"
139 :     * function in Austin Appleby's MurmurHash3 algorithm. See
140 :     * http://code.google.com/p/smhasher/wiki/MurmurHash3 , which
141 :     * comments: "The constants for the finalizers were generated by a
142 :     * simple simulated-annealing algorithm, and both avalanche all
143 :     * bits of 'h' to within 0.25% bias." It also appears to work to
144 :     * use instead any of the variants proposed by David Stafford at
145 :     * http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html
146 :     * but these variants have not yet been tested as thoroughly
147 :     * in the context of the implementation of SplittableRandom.
148 :     *
149 :     * The mix32 function used for nextInt just consists of two of the
150 :     * five lines of mix64; avalanche testing shows that the 64-bit result
151 :     * has its top 32 bits avalanched well, though not the bottom 32 bits.
152 :     * DieHarder tests show that it is adequate for generating one
153 :     * random int from the 64-bit result of nextSeed.
154 :     *
155 :     * Support for the default (no-argument) constructor relies on an
156 :     * AtomicLong (defaultSeedGenerator) to help perform the
157 :     * equivalent of a split of a statically constructed
158 :     * SplittableRandom. Unlike other cases, this split must be
159 :     * performed in a thread-safe manner. We use
160 :     * AtomicLong.compareAndSet as the (typically) most efficient
161 : dl 1.11 * mechanism. To bootstrap, we start off using a function of the
162 :     * current System time as seed, and update using another
163 :     * "genuinely random" constant DEFAULT_SEED_GAMMA. The default
164 :     * constructor uses GAMMA_GAMMA, not 0, for its splitSeed argument
165 :     * (addGammaModGeorge(0, GAMMA_GAMMA) == GAMMA_GAMMA) to reflect
166 :     * that each is split from this root generator, even though the
167 :     * root is not explicitly represented as a SplittableRandom. When
168 :     * establishing the initial seed, we use both
169 :     * System.currentTimeMillis and System.nanoTime(), to avoid
170 :     * regularities that may occur if using either alone.
171 : dl 1.1 */
172 :    
173 :     /**
174 :     * The "genuinely random" value for producing new gamma values.
175 :     * The value is arbitrary, subject to the requirement that it be
176 :     * greater or equal to 13.
177 :     */
178 :     private static final long GAMMA_GAMMA = 0xF2281E2DBA6606F3L;
179 :    
180 :     /**
181 :     * The "genuinely random" seed update value for default constructors.
182 :     * The value is arbitrary, subject to the requirement that it be
183 :     * greater or equal to 13.
184 :     */
185 :     private static final long DEFAULT_SEED_GAMMA = 0xBD24B73A95FB84D9L;
186 :    
187 :     /**
188 : dl 1.11 * The value 13 with 64bit sign bit set. Used in the signed
189 :     * comparison in addGammaModGeorge.
190 :     */
191 :     private static final long BOTTOM13 = 0x800000000000000DL;
192 :    
193 :     /**
194 : dl 1.5 * The least non-zero value returned by nextDouble(). This value
195 : dl 1.7 * is scaled by a random value of 53 bits to produce a result.
196 : dl 1.5 */
197 :     private static final double DOUBLE_UNIT = 1.0 / (1L << 53);
198 :    
199 :     /**
200 : dl 1.1 * The next seed for default constructors.
201 :     */
202 :     private static final AtomicLong defaultSeedGenerator =
203 : dl 1.11 new AtomicLong(mix64(System.currentTimeMillis()) ^
204 :     mix64(System.nanoTime()));
205 : dl 1.1
206 :     /**
207 :     * The seed, updated only via method nextSeed.
208 :     */
209 :     private long seed;
210 :    
211 :     /**
212 :     * The constant value added to seed (mod George) on each update.
213 :     */
214 :     private final long gamma;
215 :    
216 :     /**
217 :     * The next seed to use for splits. Propagated using
218 :     * addGammaModGeorge across instances.
219 :     */
220 :     private final long nextSplit;
221 :    
222 :     /**
223 :     * Adds the given gamma value, g, to the given seed value s, mod
224 :     * George (2^64+13). We regard s and g as unsigned values
225 :     * (ranging from 0 to 2^64-1). We add g to s either once or twice
226 :     * (mod George) as necessary to produce an (unsigned) result less
227 :     * than 2^64. We require that g must be at least 13. This
228 :     * guarantees that if (s+g) mod George >= 2^64 then (s+g+g) mod
229 :     * George < 2^64; thus we need only a conditional, not a loop,
230 :     * to be sure of getting a representable value.
231 :     *
232 : dl 1.11 * Because Java comparison operators are signed, we implement this
233 :     * by conceptually offsetting seed values downwards by 2^63, so
234 :     * 0..13 is represented as Long.MIN_VALUE..BOTTOM13.
235 :     *
236 :     * @param s a seed value, viewed as a signed long
237 : dl 1.1 * @param g a gamma value, 13 <= g (as unsigned)
238 :     */
239 :     private static long addGammaModGeorge(long s, long g) {
240 :     long p = s + g;
241 : dl 1.11 return (p >= s) ? p : ((p >= BOTTOM13) ? p : p + g) - 13L;
242 : dl 1.1 }
243 :    
244 :     /**
245 :     * Returns a bit-mixed transformation of its argument.
246 :     * See above for explanation.
247 :     */
248 :     private static long mix64(long z) {
249 :     z ^= (z >>> 33);
250 :     z *= 0xff51afd7ed558ccdL;
251 :     z ^= (z >>> 33);
252 :     z *= 0xc4ceb9fe1a85ec53L;
253 :     z ^= (z >>> 33);
254 :     return z;
255 :     }
256 :    
257 :     /**
258 :     * Returns a bit-mixed int transformation of its argument.
259 :     * See above for explanation.
260 :     */
261 :     private static int mix32(long z) {
262 :     z ^= (z >>> 33);
263 :     z *= 0xc4ceb9fe1a85ec53L;
264 :     return (int)(z >>> 32);
265 :     }
266 :    
267 :     /**
268 : dl 1.7 * Internal constructor used by all other constructors and by
269 :     * method split. Establishes the initial seed for this instance,
270 :     * and uses the given splitSeed to establish gamma, as well as the
271 :     * nextSplit to use by this instance. The loop to skip ineligible
272 :     * gammas very rarely iterates, and does so at most 13 times.
273 :     */
274 :     private SplittableRandom(long seed, long splitSeed) {
275 :     this.seed = seed;
276 :     long s = splitSeed, g;
277 :     do { // ensure gamma >= 13, considered as an unsigned integer
278 :     s = addGammaModGeorge(s, GAMMA_GAMMA);
279 :     g = mix64(s);
280 : dl 1.11 } while (g >= 0L && g < 13L);
281 : dl 1.7 this.gamma = g;
282 :     this.nextSplit = s;
283 :     }
284 :    
285 :     /**
286 :     * Updates in-place and returns seed.
287 :     * See above for explanation.
288 :     */
289 :     private long nextSeed() {
290 :     return seed = addGammaModGeorge(seed, gamma);
291 :     }
292 :    
293 :     /**
294 :     * Atomically updates and returns next seed for default constructor.
295 : dl 1.1 */
296 :     private static long nextDefaultSeed() {
297 :     long oldSeed, newSeed;
298 :     do {
299 :     oldSeed = defaultSeedGenerator.get();
300 :     newSeed = addGammaModGeorge(oldSeed, DEFAULT_SEED_GAMMA);
301 :     } while (!defaultSeedGenerator.compareAndSet(oldSeed, newSeed));
302 :     return mix64(newSeed);
303 :     }
304 :    
305 :     /*
306 :     * Internal versions of nextX methods used by streams, as well as
307 :     * the public nextX(origin, bound) methods. These exist mainly to
308 :     * avoid the need for multiple versions of stream spliterators
309 :     * across the different exported forms of streams.
310 :     */
311 :    
312 :     /**
313 :     * The form of nextLong used by LongStream Spliterators. If
314 :     * origin is greater than bound, acts as unbounded form of
315 :     * nextLong, else as bounded form.
316 :     *
317 :     * @param origin the least value, unless greater than bound
318 :     * @param bound the upper bound (exclusive), must not equal origin
319 :     * @return a pseudorandom value
320 :     */
321 :     final long internalNextLong(long origin, long bound) {
322 :     /*
323 :     * Four Cases:
324 :     *
325 :     * 1. If the arguments indicate unbounded form, act as
326 :     * nextLong().
327 :     *
328 :     * 2. If the range is an exact power of two, apply the
329 :     * associated bit mask.
330 :     *
331 :     * 3. If the range is positive, loop to avoid potential bias
332 :     * when the implicit nextLong() bound (2<sup>64</sup>) is not
333 :     * evenly divisible by the range. The loop rejects candidates
334 :     * computed from otherwise over-represented values. The
335 :     * expected number of iterations under an ideal generator
336 : dl 1.4 * varies from 1 to 2, depending on the bound. The loop itself
337 :     * takes an unlovable form. Because the first candidate is
338 :     * already available, we need a break-in-the-middle
339 :     * construction, which is concisely but cryptically performed
340 :     * within the while-condition of a body-less for loop.
341 : dl 1.1 *
342 :     * 4. Otherwise, the range cannot be represented as a positive
343 : dl 1.4 * long. The loop repeatedly generates unbounded longs until
344 :     * obtaining a candidate meeting constraints (with an expected
345 :     * number of iterations of less than two).
346 : dl 1.1 */
347 :    
348 :     long r = mix64(nextSeed());
349 :     if (origin < bound) {
350 :     long n = bound - origin, m = n - 1;
351 : dl 1.7 if ((n & m) == 0L) // power of two
352 : dl 1.1 r = (r & m) + origin;
353 : dl 1.7 else if (n > 0L) { // reject over-represented candidates
354 : dl 1.1 for (long u = r >>> 1; // ensure nonnegative
355 : dl 1.7 u + m - (r = u % n) < 0L; // rejection check
356 : dl 1.1 u = mix64(nextSeed()) >>> 1) // retry
357 :     ;
358 :     r += origin;
359 :     }
360 : dl 1.7 else { // range not representable as long
361 : dl 1.1 while (r < origin || r >= bound)
362 :     r = mix64(nextSeed());
363 :     }
364 :     }
365 :     return r;
366 :     }
367 :    
368 :     /**
369 :     * The form of nextInt used by IntStream Spliterators.
370 :     * Exactly the same as long version, except for types.
371 :     *
372 :     * @param origin the least value, unless greater than bound
373 :     * @param bound the upper bound (exclusive), must not equal origin
374 :     * @return a pseudorandom value
375 :     */
376 :     final int internalNextInt(int origin, int bound) {
377 :     int r = mix32(nextSeed());
378 :     if (origin < bound) {
379 :     int n = bound - origin, m = n - 1;
380 :     if ((n & m) == 0L)
381 :     r = (r & m) + origin;
382 :     else if (n > 0) {
383 :     for (int u = r >>> 1;
384 : dl 1.7 u + m - (r = u % n) < 0;
385 : dl 1.1 u = mix32(nextSeed()) >>> 1)
386 :     ;
387 :     r += origin;
388 :     }
389 :     else {
390 :     while (r < origin || r >= bound)
391 :     r = mix32(nextSeed());
392 :     }
393 :     }
394 :     return r;
395 :     }
396 :    
397 :     /**
398 :     * The form of nextDouble used by DoubleStream Spliterators.
399 :     *
400 :     * @param origin the least value, unless greater than bound
401 :     * @param bound the upper bound (exclusive), must not equal origin
402 :     * @return a pseudorandom value
403 :     */
404 :     final double internalNextDouble(double origin, double bound) {
405 : dl 1.5 double r = (nextLong() >>> 11) * DOUBLE_UNIT;
406 : dl 1.1 if (origin < bound) {
407 :     r = r * (bound - origin) + origin;
408 : dl 1.7 if (r >= bound) // correct for rounding
409 : dl 1.1 r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
410 :     }
411 :     return r;
412 :     }
413 :    
414 :     /* ---------------- public methods ---------------- */
415 :    
416 :     /**
417 : dl 1.7 * Creates a new SplittableRandom instance using the specified
418 :     * initial seed. SplittableRandom instances created with the same
419 : dl 1.11 * seed in the same program generate identical sequences of values.
420 : dl 1.1 *
421 :     * @param seed the initial seed
422 :     */
423 :     public SplittableRandom(long seed) {
424 :     this(seed, 0);
425 :     }
426 :    
427 :     /**
428 :     * Creates a new SplittableRandom instance that is likely to
429 :     * generate sequences of values that are statistically independent
430 :     * of those of any other instances in the current program; and
431 :     * may, and typically does, vary across program invocations.
432 :     */
433 :     public SplittableRandom() {
434 :     this(nextDefaultSeed(), GAMMA_GAMMA);
435 :     }
436 :    
437 :     /**
438 :     * Constructs and returns a new SplittableRandom instance that
439 :     * shares no mutable state with this instance. However, with very
440 :     * high probability, the set of values collectively generated by
441 :     * the two objects has the same statistical properties as if the
442 :     * same quantity of values were generated by a single thread using
443 :     * a single SplittableRandom object. Either or both of the two
444 :     * objects may be further split using the {@code split()} method,
445 :     * and the same expected statistical properties apply to the
446 :     * entire set of generators constructed by such recursive
447 :     * splitting.
448 :     *
449 :     * @return the new SplittableRandom instance
450 :     */
451 :     public SplittableRandom split() {
452 :     return new SplittableRandom(nextSeed(), nextSplit);
453 :     }
454 :    
455 :     /**
456 :     * Returns a pseudorandom {@code int} value.
457 :     *
458 : dl 1.7 * @return a pseudorandom {@code int} value
459 : dl 1.1 */
460 :     public int nextInt() {
461 :     return mix32(nextSeed());
462 :     }
463 :    
464 :     /**
465 : dl 1.7 * Returns a pseudorandom {@code int} value between zero (inclusive)
466 : dl 1.1 * and the specified bound (exclusive).
467 :     *
468 :     * @param bound the bound on the random number to be returned. Must be
469 :     * positive.
470 : dl 1.7 * @return a pseudorandom {@code int} value between zero
471 : jsr166 1.10 * (inclusive) and the bound (exclusive)
472 : dl 1.7 * @throws IllegalArgumentException if the bound is less than zero
473 : dl 1.1 */
474 :     public int nextInt(int bound) {
475 :     if (bound <= 0)
476 :     throw new IllegalArgumentException("bound must be positive");
477 :     // Specialize internalNextInt for origin 0
478 :     int r = mix32(nextSeed());
479 :     int m = bound - 1;
480 :     if ((bound & m) == 0L) // power of two
481 :     r &= m;
482 :     else { // reject over-represented candidates
483 :     for (int u = r >>> 1;
484 : dl 1.7 u + m - (r = u % bound) < 0;
485 : dl 1.1 u = mix32(nextSeed()) >>> 1)
486 :     ;
487 :     }
488 :     return r;
489 :     }
490 :    
491 :     /**
492 :     * Returns a pseudorandom {@code int} value between the specified
493 :     * origin (inclusive) and the specified bound (exclusive).
494 :     *
495 :     * @param origin the least value returned
496 :     * @param bound the upper bound (exclusive)
497 :     * @return a pseudorandom {@code int} value between the origin
498 : jsr166 1.10 * (inclusive) and the bound (exclusive)
499 : dl 1.7 * @throws IllegalArgumentException if {@code origin} is greater than
500 : dl 1.1 * or equal to {@code bound}
501 :     */
502 :     public int nextInt(int origin, int bound) {
503 :     if (origin >= bound)
504 :     throw new IllegalArgumentException("bound must be greater than origin");
505 :     return internalNextInt(origin, bound);
506 :     }
507 :    
508 :     /**
509 :     * Returns a pseudorandom {@code long} value.
510 :     *
511 : dl 1.7 * @return a pseudorandom {@code long} value
512 : dl 1.1 */
513 :     public long nextLong() {
514 :     return mix64(nextSeed());
515 :     }
516 :    
517 :     /**
518 : dl 1.7 * Returns a pseudorandom {@code long} value between zero (inclusive)
519 : dl 1.1 * and the specified bound (exclusive).
520 :     *
521 :     * @param bound the bound on the random number to be returned. Must be
522 :     * positive.
523 : dl 1.7 * @return a pseudorandom {@code long} value between zero
524 : jsr166 1.10 * (inclusive) and the bound (exclusive)
525 : dl 1.7 * @throws IllegalArgumentException if {@code bound} is less than zero
526 : dl 1.1 */
527 :     public long nextLong(long bound) {
528 :     if (bound <= 0)
529 :     throw new IllegalArgumentException("bound must be positive");
530 :     // Specialize internalNextLong for origin 0
531 :     long r = mix64(nextSeed());
532 :     long m = bound - 1;
533 :     if ((bound & m) == 0L) // power of two
534 :     r &= m;
535 :     else { // reject over-represented candidates
536 :     for (long u = r >>> 1;
537 :     u + m - (r = u % bound) < 0L;
538 :     u = mix64(nextSeed()) >>> 1)
539 :     ;
540 :     }
541 :     return r;
542 :     }
543 :    
544 :     /**
545 :     * Returns a pseudorandom {@code long} value between the specified
546 :     * origin (inclusive) and the specified bound (exclusive).
547 :     *
548 :     * @param origin the least value returned
549 :     * @param bound the upper bound (exclusive)
550 :     * @return a pseudorandom {@code long} value between the origin
551 : jsr166 1.10 * (inclusive) and the bound (exclusive)
552 : dl 1.7 * @throws IllegalArgumentException if {@code origin} is greater than
553 : dl 1.1 * or equal to {@code bound}
554 :     */
555 :     public long nextLong(long origin, long bound) {
556 :     if (origin >= bound)
557 :     throw new IllegalArgumentException("bound must be greater than origin");
558 :     return internalNextLong(origin, bound);
559 :     }
560 :    
561 :     /**
562 : dl 1.7 * Returns a pseudorandom {@code double} value between zero
563 :     * (inclusive) and one (exclusive).
564 : dl 1.1 *
565 : dl 1.7 * @return a pseudorandom {@code double} value between zero
566 :     * (inclusive) and one (exclusive)
567 : dl 1.1 */
568 :     public double nextDouble() {
569 : dl 1.11 return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT;
570 : dl 1.1 }
571 :    
572 :     /**
573 :     * Returns a pseudorandom {@code double} value between 0.0
574 :     * (inclusive) and the specified bound (exclusive).
575 :     *
576 :     * @param bound the bound on the random number to be returned. Must be
577 :     * positive.
578 : dl 1.7 * @return a pseudorandom {@code double} value between zero
579 : jsr166 1.10 * (inclusive) and the bound (exclusive)
580 : dl 1.7 * @throws IllegalArgumentException if {@code bound} is less than zero
581 : dl 1.1 */
582 :     public double nextDouble(double bound) {
583 : dl 1.7 if (!(bound > 0.0))
584 : dl 1.1 throw new IllegalArgumentException("bound must be positive");
585 : dl 1.11 double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound;
586 : dl 1.1 return (result < bound) ? result : // correct for rounding
587 :     Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
588 :     }
589 :    
590 :     /**
591 : dl 1.7 * Returns a pseudorandom {@code double} value between the specified
592 : dl 1.1 * origin (inclusive) and bound (exclusive).
593 :     *
594 :     * @param origin the least value returned
595 :     * @param bound the upper bound
596 :     * @return a pseudorandom {@code double} value between the origin
597 : jsr166 1.10 * (inclusive) and the bound (exclusive)
598 : dl 1.1 * @throws IllegalArgumentException if {@code origin} is greater than
599 :     * or equal to {@code bound}
600 :     */
601 :     public double nextDouble(double origin, double bound) {
602 : dl 1.7 if (!(origin < bound))
603 : dl 1.1 throw new IllegalArgumentException("bound must be greater than origin");
604 :     return internalNextDouble(origin, bound);
605 :     }
606 :    
607 : dl 1.11 /**
608 :     * Returns a pseudorandom {@code boolean} value.
609 :     *
610 :     * @return a pseudorandom {@code boolean} value
611 :     */
612 :     public boolean nextBoolean() {
613 :     return mix32(nextSeed()) < 0;
614 :     }
615 :    
616 : dl 1.1 // stream methods, coded in a way intended to better isolate for
617 :     // maintenance purposes the small differences across forms.
618 :    
619 :     /**
620 : dl 1.7 * Returns a stream producing the given {@code streamSize} number of
621 : dl 1.1 * pseudorandom {@code int} values.
622 :     *
623 :     * @param streamSize the number of values to generate
624 :     * @return a stream of pseudorandom {@code int} values
625 :     * @throws IllegalArgumentException if {@code streamSize} is
626 : dl 1.7 * less than zero
627 : dl 1.1 */
628 :     public IntStream ints(long streamSize) {
629 :     if (streamSize < 0L)
630 :     throw new IllegalArgumentException("negative Stream size");
631 :     return StreamSupport.intStream
632 :     (new RandomIntsSpliterator
633 :     (this, 0L, streamSize, Integer.MAX_VALUE, 0),
634 :     false);
635 :     }
636 :    
637 :     /**
638 :     * Returns an effectively unlimited stream of pseudorandom {@code int}
639 : jsr166 1.10 * values.
640 : dl 1.1 *
641 :     * @implNote This method is implemented to be equivalent to {@code
642 :     * ints(Long.MAX_VALUE)}.
643 :     *
644 :     * @return a stream of pseudorandom {@code int} values
645 :     */
646 :     public IntStream ints() {
647 :     return StreamSupport.intStream
648 :     (new RandomIntsSpliterator
649 :     (this, 0L, Long.MAX_VALUE, Integer.MAX_VALUE, 0),
650 :     false);
651 :     }
652 :    
653 :     /**
654 : dl 1.7 * Returns a stream producing the given {@code streamSize} number of
655 : dl 1.1 * pseudorandom {@code int} values, each conforming to the given
656 :     * origin and bound.
657 :     *
658 :     * @param streamSize the number of values to generate
659 :     * @param randomNumberOrigin the origin of each random value
660 :     * @param randomNumberBound the bound of each random value
661 :     * @return a stream of pseudorandom {@code int} values,
662 : jsr166 1.10 * each with the given origin and bound
663 : dl 1.1 * @throws IllegalArgumentException if {@code streamSize} is
664 : dl 1.7 * less than zero, or {@code randomNumberOrigin}
665 : dl 1.1 * is greater than or equal to {@code randomNumberBound}
666 :     */
667 :     public IntStream ints(long streamSize, int randomNumberOrigin,
668 :     int randomNumberBound) {
669 :     if (streamSize < 0L)
670 :     throw new IllegalArgumentException("negative Stream size");
671 :     if (randomNumberOrigin >= randomNumberBound)
672 :     throw new IllegalArgumentException("bound must be greater than origin");
673 :     return StreamSupport.intStream
674 :     (new RandomIntsSpliterator
675 :     (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
676 :     false);
677 :     }
678 :    
679 :     /**
680 :     * Returns an effectively unlimited stream of pseudorandom {@code
681 :     * int} values, each conforming to the given origin and bound.
682 :     *
683 :     * @implNote This method is implemented to be equivalent to {@code
684 :     * ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
685 :     *
686 :     * @param randomNumberOrigin the origin of each random value
687 :     * @param randomNumberBound the bound of each random value
688 :     * @return a stream of pseudorandom {@code int} values,
689 : jsr166 1.10 * each with the given origin and bound
690 : dl 1.1 * @throws IllegalArgumentException if {@code randomNumberOrigin}
691 :     * is greater than or equal to {@code randomNumberBound}
692 :     */
693 :     public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
694 :     if (randomNumberOrigin >= randomNumberBound)
695 :     throw new IllegalArgumentException("bound must be greater than origin");
696 :     return StreamSupport.intStream
697 :     (new RandomIntsSpliterator
698 :     (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
699 :     false);
700 :     }
701 :    
702 :     /**
703 : dl 1.7 * Returns a stream producing the given {@code streamSize} number of
704 : dl 1.1 * pseudorandom {@code long} values.
705 :     *
706 :     * @param streamSize the number of values to generate
707 : dl 1.7 * @return a stream of pseudorandom {@code long} values
708 : dl 1.1 * @throws IllegalArgumentException if {@code streamSize} is
709 : dl 1.7 * less than zero
710 : dl 1.1 */
711 :     public LongStream longs(long streamSize) {
712 :     if (streamSize < 0L)
713 :     throw new IllegalArgumentException("negative Stream size");
714 :     return StreamSupport.longStream
715 :     (new RandomLongsSpliterator
716 :     (this, 0L, streamSize, Long.MAX_VALUE, 0L),
717 :     false);
718 :     }
719 :    
720 :     /**
721 :     * Returns an effectively unlimited stream of pseudorandom {@code long}
722 :     * values.
723 :     *
724 :     * @implNote This method is implemented to be equivalent to {@code
725 :     * longs(Long.MAX_VALUE)}.
726 :     *
727 :     * @return a stream of pseudorandom {@code long} values
728 :     */
729 :     public LongStream longs() {
730 :     return StreamSupport.longStream
731 :     (new RandomLongsSpliterator
732 :     (this, 0L, Long.MAX_VALUE, Long.MAX_VALUE, 0L),
733 :     false);
734 :     }
735 :    
736 :     /**
737 : dl 1.7 * Returns a stream producing the given {@code streamSize} number of
738 : dl 1.1 * pseudorandom {@code long} values, each conforming to the
739 :     * given origin and bound.
740 :     *
741 :     * @param streamSize the number of values to generate
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 : jsr166 1.10 * each with the given origin and bound
746 : dl 1.1 * @throws IllegalArgumentException if {@code streamSize} is
747 : dl 1.7 * less than zero, or {@code randomNumberOrigin}
748 : dl 1.1 * is greater than or equal to {@code randomNumberBound}
749 :     */
750 :     public LongStream longs(long streamSize, long randomNumberOrigin,
751 :     long randomNumberBound) {
752 :     if (streamSize < 0L)
753 :     throw new IllegalArgumentException("negative Stream size");
754 :     if (randomNumberOrigin >= randomNumberBound)
755 :     throw new IllegalArgumentException("bound must be greater than origin");
756 :     return StreamSupport.longStream
757 :     (new RandomLongsSpliterator
758 :     (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
759 :     false);
760 :     }
761 :    
762 :     /**
763 :     * Returns an effectively unlimited stream of pseudorandom {@code
764 :     * long} values, each conforming to the given origin and bound.
765 :     *
766 :     * @implNote This method is implemented to be equivalent to {@code
767 :     * longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
768 :     *
769 :     * @param randomNumberOrigin the origin of each random value
770 :     * @param randomNumberBound the bound of each random value
771 :     * @return a stream of pseudorandom {@code long} values,
772 : jsr166 1.10 * each with the given origin and bound
773 : dl 1.1 * @throws IllegalArgumentException if {@code randomNumberOrigin}
774 :     * is greater than or equal to {@code randomNumberBound}
775 :     */
776 :     public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
777 :     if (randomNumberOrigin >= randomNumberBound)
778 :     throw new IllegalArgumentException("bound must be greater than origin");
779 :     return StreamSupport.longStream
780 :     (new RandomLongsSpliterator
781 :     (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
782 :     false);
783 :     }
784 :    
785 :     /**
786 : dl 1.7 * Returns a stream producing the given {@code streamSize} number of
787 :     * pseudorandom {@code double} values, each between zero
788 :     * (inclusive) and one (exclusive).
789 : dl 1.1 *
790 :     * @param streamSize the number of values to generate
791 :     * @return a stream of {@code double} values
792 :     * @throws IllegalArgumentException if {@code streamSize} is
793 : dl 1.7 * less than zero
794 : dl 1.1 */
795 :     public DoubleStream doubles(long streamSize) {
796 :     if (streamSize < 0L)
797 :     throw new IllegalArgumentException("negative Stream size");
798 :     return StreamSupport.doubleStream
799 :     (new RandomDoublesSpliterator
800 :     (this, 0L, streamSize, Double.MAX_VALUE, 0.0),
801 :     false);
802 :     }
803 :    
804 :     /**
805 :     * Returns an effectively unlimited stream of pseudorandom {@code
806 : dl 1.7 * double} values, each between zero (inclusive) and one
807 :     * (exclusive).
808 : dl 1.1 *
809 :     * @implNote This method is implemented to be equivalent to {@code
810 :     * doubles(Long.MAX_VALUE)}.
811 :     *
812 :     * @return a stream of pseudorandom {@code double} values
813 :     */
814 :     public DoubleStream doubles() {
815 :     return StreamSupport.doubleStream
816 :     (new RandomDoublesSpliterator
817 :     (this, 0L, Long.MAX_VALUE, Double.MAX_VALUE, 0.0),
818 :     false);
819 :     }
820 :    
821 :     /**
822 : dl 1.7 * Returns a stream producing the given {@code streamSize} number of
823 : dl 1.1 * pseudorandom {@code double} values, each conforming to the
824 :     * given origin and bound.
825 :     *
826 :     * @param streamSize the number of values to generate
827 :     * @param randomNumberOrigin the origin of each random value
828 :     * @param randomNumberBound the bound of each random value
829 :     * @return a stream of pseudorandom {@code double} values,
830 : jsr166 1.10 * each with the given origin and bound
831 : dl 1.1 * @throws IllegalArgumentException if {@code streamSize} is
832 : jsr166 1.10 * less than zero
833 : dl 1.1 * @throws IllegalArgumentException if {@code randomNumberOrigin}
834 :     * is greater than or equal to {@code randomNumberBound}
835 :     */
836 :     public DoubleStream doubles(long streamSize, double randomNumberOrigin,
837 :     double randomNumberBound) {
838 :     if (streamSize < 0L)
839 :     throw new IllegalArgumentException("negative Stream size");
840 : dl 1.7 if (!(randomNumberOrigin < randomNumberBound))
841 : dl 1.1 throw new IllegalArgumentException("bound must be greater than origin");
842 :     return StreamSupport.doubleStream
843 :     (new RandomDoublesSpliterator
844 :     (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
845 :     false);
846 :     }
847 :    
848 :     /**
849 :     * Returns an effectively unlimited stream of pseudorandom {@code
850 :     * double} values, each conforming to the given origin and bound.
851 :     *
852 :     * @implNote This method is implemented to be equivalent to {@code
853 :     * doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
854 :     *
855 :     * @param randomNumberOrigin the origin of each random value
856 :     * @param randomNumberBound the bound of each random value
857 :     * @return a stream of pseudorandom {@code double} values,
858 : jsr166 1.10 * each with the given origin and bound
859 : dl 1.1 * @throws IllegalArgumentException if {@code randomNumberOrigin}
860 :     * is greater than or equal to {@code randomNumberBound}
861 :     */
862 :     public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
863 : dl 1.7 if (!(randomNumberOrigin < randomNumberBound))
864 : dl 1.1 throw new IllegalArgumentException("bound must be greater than origin");
865 :     return StreamSupport.doubleStream
866 :     (new RandomDoublesSpliterator
867 :     (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
868 :     false);
869 :     }
870 :    
871 :     /**
872 :     * Spliterator for int streams. We multiplex the four int
873 : dl 1.7 * versions into one class by treating a bound less than origin as
874 : dl 1.1 * unbounded, and also by treating "infinite" as equivalent to
875 :     * Long.MAX_VALUE. For splits, it uses the standard divide-by-two
876 :     * approach. The long and double versions of this class are
877 :     * identical except for types.
878 :     */
879 : dl 1.11 static final class RandomIntsSpliterator implements Spliterator.OfInt {
880 : dl 1.1 final SplittableRandom rng;
881 :     long index;
882 :     final long fence;
883 :     final int origin;
884 :     final int bound;
885 :     RandomIntsSpliterator(SplittableRandom rng, long index, long fence,
886 :     int origin, int bound) {
887 :     this.rng = rng; this.index = index; this.fence = fence;
888 :     this.origin = origin; this.bound = bound;
889 :     }
890 :    
891 :     public RandomIntsSpliterator trySplit() {
892 :     long i = index, m = (i + fence) >>> 1;
893 :     return (m <= i) ? null :
894 :     new RandomIntsSpliterator(rng.split(), i, index = m, origin, bound);
895 :     }
896 :    
897 :     public long estimateSize() {
898 :     return fence - index;
899 :     }
900 :    
901 :     public int characteristics() {
902 :     return (Spliterator.SIZED | Spliterator.SUBSIZED |
903 : dl 1.4 Spliterator.NONNULL | Spliterator.IMMUTABLE);
904 : dl 1.1 }
905 :    
906 :     public boolean tryAdvance(IntConsumer consumer) {
907 :     if (consumer == null) throw new NullPointerException();
908 :     long i = index, f = fence;
909 :     if (i < f) {
910 :     consumer.accept(rng.internalNextInt(origin, bound));
911 :     index = i + 1;
912 :     return true;
913 :     }
914 :     return false;
915 :     }
916 :    
917 :     public void forEachRemaining(IntConsumer consumer) {
918 :     if (consumer == null) throw new NullPointerException();
919 :     long i = index, f = fence;
920 :     if (i < f) {
921 :     index = f;
922 :     int o = origin, b = bound;
923 :     do {
924 :     consumer.accept(rng.internalNextInt(o, b));
925 :     } while (++i < f);
926 :     }
927 :     }
928 :     }
929 :    
930 :     /**
931 :     * Spliterator for long streams.
932 :     */
933 : dl 1.11 static final class RandomLongsSpliterator implements Spliterator.OfLong {
934 : dl 1.1 final SplittableRandom rng;
935 :     long index;
936 :     final long fence;
937 :     final long origin;
938 :     final long bound;
939 :     RandomLongsSpliterator(SplittableRandom rng, long index, long fence,
940 :     long origin, long bound) {
941 :     this.rng = rng; this.index = index; this.fence = fence;
942 :     this.origin = origin; this.bound = bound;
943 :     }
944 :    
945 :     public RandomLongsSpliterator trySplit() {
946 :     long i = index, m = (i + fence) >>> 1;
947 :     return (m <= i) ? null :
948 :     new RandomLongsSpliterator(rng.split(), i, index = m, origin, bound);
949 :     }
950 :    
951 :     public long estimateSize() {
952 :     return fence - index;
953 :     }
954 :    
955 :     public int characteristics() {
956 :     return (Spliterator.SIZED | Spliterator.SUBSIZED |
957 : dl 1.4 Spliterator.NONNULL | Spliterator.IMMUTABLE);
958 : dl 1.1 }
959 :    
960 :     public boolean tryAdvance(LongConsumer consumer) {
961 :     if (consumer == null) throw new NullPointerException();
962 :     long i = index, f = fence;
963 :     if (i < f) {
964 :     consumer.accept(rng.internalNextLong(origin, bound));
965 :     index = i + 1;
966 :     return true;
967 :     }
968 :     return false;
969 :     }
970 :    
971 :     public void forEachRemaining(LongConsumer consumer) {
972 :     if (consumer == null) throw new NullPointerException();
973 :     long i = index, f = fence;
974 :     if (i < f) {
975 :     index = f;
976 :     long o = origin, b = bound;
977 :     do {
978 :     consumer.accept(rng.internalNextLong(o, b));
979 :     } while (++i < f);
980 :     }
981 :     }
982 :    
983 :     }
984 :    
985 :     /**
986 :     * Spliterator for double streams.
987 :     */
988 : dl 1.11 static final class RandomDoublesSpliterator implements Spliterator.OfDouble {
989 : dl 1.1 final SplittableRandom rng;
990 :     long index;
991 :     final long fence;
992 :     final double origin;
993 :     final double bound;
994 :     RandomDoublesSpliterator(SplittableRandom rng, long index, long fence,
995 :     double origin, double bound) {
996 :     this.rng = rng; this.index = index; this.fence = fence;
997 :     this.origin = origin; this.bound = bound;
998 :     }
999 :    
1000 :     public RandomDoublesSpliterator trySplit() {
1001 :     long i = index, m = (i + fence) >>> 1;
1002 :     return (m <= i) ? null :
1003 :     new RandomDoublesSpliterator(rng.split(), i, index = m, origin, bound);
1004 :     }
1005 :    
1006 :     public long estimateSize() {
1007 :     return fence - index;
1008 :     }
1009 :    
1010 :     public int characteristics() {
1011 :     return (Spliterator.SIZED | Spliterator.SUBSIZED |
1012 : dl 1.4 Spliterator.NONNULL | Spliterator.IMMUTABLE);
1013 : dl 1.1 }
1014 :    
1015 :     public boolean tryAdvance(DoubleConsumer consumer) {
1016 :     if (consumer == null) throw new NullPointerException();
1017 :     long i = index, f = fence;
1018 :     if (i < f) {
1019 :     consumer.accept(rng.internalNextDouble(origin, bound));
1020 :     index = i + 1;
1021 :     return true;
1022 :     }
1023 :     return false;
1024 :     }
1025 :    
1026 :     public void forEachRemaining(DoubleConsumer consumer) {
1027 :     if (consumer == null) throw new NullPointerException();
1028 :     long i = index, f = fence;
1029 :     if (i < f) {
1030 :     index = f;
1031 :     double o = origin, b = bound;
1032 :     do {
1033 :     consumer.accept(rng.internalNextDouble(o, b));
1034 :     } while (++i < f);
1035 :     }
1036 :     }
1037 :     }
1038 :    
1039 :     }

Doug Lea
ViewVC Help
Powered by ViewVC 1.0.8