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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 : jsr166 1.26 import java.util.function.DoubleConsumer;
30 : dl 1.1 import java.util.function.IntConsumer;
31 :     import java.util.function.LongConsumer;
32 : jsr166 1.26 import java.util.stream.DoubleStream;
33 : dl 1.1 import java.util.stream.IntStream;
34 :     import java.util.stream.LongStream;
35 : jsr166 1.26 import java.util.stream.StreamSupport;
36 : dl 1.1
37 :     /**
38 :     * A generator of uniform pseudorandom values applicable for use in
39 :     * (among other contexts) isolated parallel computations that may
40 : dl 1.18 * generate subtasks. Class {@code SplittableRandom} supports methods for
41 : jsr166 1.3 * producing pseudorandom numbers of type {@code int}, {@code long},
42 : dl 1.1 * and {@code double} with similar usages as for class
43 : jsr166 1.9 * {@link java.util.Random} but differs in the following ways:
44 :     *
45 :     * <ul>
46 : dl 1.1 *
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 : dl 1.11 * least approximately, for others as well. The <em>period</em>
54 :     * (length of any series of generated values before it repeats) is at
55 : jsr166 1.27 * least 2<sup>64</sup>.
56 : dl 1.1 *
57 : jsr166 1.27 * <li>Method {@link #split} constructs and returns a new
58 : dl 1.1 * SplittableRandom instance that shares no mutable state with the
59 : dl 1.7 * current instance. However, with very high probability, the
60 :     * values collectively generated by the two objects have the same
61 : dl 1.1 * statistical properties as if the same quantity of values were
62 :     * generated by a single thread using a single {@code
63 : jsr166 1.27 * SplittableRandom} object.
64 : dl 1.1 *
65 :     * <li>Instances of SplittableRandom are <em>not</em> thread-safe.
66 :     * They are designed to be split, not shared, across threads. For
67 :     * example, a {@link java.util.concurrent.ForkJoinTask
68 :     * fork/join-style} computation using random numbers might include a
69 :     * construction of the form {@code new
70 :     * Subtask(aSplittableRandom.split()).fork()}.
71 :     *
72 :     * <li>This class provides additional methods for generating random
73 :     * streams, that employ the above techniques when used in {@code
74 : jsr166 1.27 * stream.parallel()} mode.
75 : dl 1.1 *
76 :     * </ul>
77 :     *
78 : dl 1.18 * <p>Instances of {@code SplittableRandom} are not cryptographically
79 :     * secure. Consider instead using {@link java.security.SecureRandom}
80 :     * in security-sensitive applications. Additionally,
81 :     * default-constructed instances do not use a cryptographically random
82 :     * seed unless the {@linkplain System#getProperty system property}
83 :     * {@code java.util.secureRandomSeed} is set to {@code true}.
84 :     *
85 : dl 1.1 * @author Guy Steele
86 : dl 1.2 * @author Doug Lea
87 : dl 1.1 * @since 1.8
88 :     */
89 : dl 1.23 public final class SplittableRandom {
90 : dl 1.1
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 : dl 1.15 * PPoPP 2012, as well as those in "Parallel random numbers: as
98 :     * easy as 1, 2, 3" by Salmon, Morae, Dror, and Shaw, SC 2011. It
99 :     * differs mainly in simplifying and cheapening operations.
100 :     *
101 :     * The primary update step (method nextSeed()) is to add a
102 :     * constant ("gamma") to the current (64 bit) seed, forming a
103 :     * simple sequence. The seed and the gamma values for any two
104 :     * SplittableRandom instances are highly likely to be different.
105 :     *
106 :     * Methods nextLong, nextInt, and derivatives do not return the
107 :     * sequence (seed) values, but instead a hash-like bit-mix of
108 :     * their bits, producing more independently distributed sequences.
109 : dl 1.21 * For nextLong, the mix64 function is based on David Stafford's
110 :     * (http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html)
111 :     * "Mix13" variant of the "64-bit finalizer" function in Austin
112 : dl 1.24 * Appleby's MurmurHash3 algorithm (see
113 :     * http://code.google.com/p/smhasher/wiki/MurmurHash3). The mix32
114 : dl 1.21 * function is based on Stafford's Mix04 mix function, but returns
115 :     * the upper 32 bits cast as int.
116 : dl 1.15 *
117 :     * The split operation uses the current generator to form the seed
118 :     * and gamma for another SplittableRandom. To conservatively
119 :     * avoid potential correlations between seed and value generation,
120 : dl 1.21 * gamma selection (method mixGamma) uses different
121 :     * (Murmurhash3's) mix constants. To avoid potential weaknesses
122 :     * in bit-mixing transformations, we restrict gammas to odd values
123 :     * with at least 24 0-1 or 1-0 bit transitions. Rather than
124 :     * rejecting candidates with too few or too many bits set, method
125 :     * mixGamma flips some bits (which has the effect of mapping at
126 :     * most 4 to any given gamma value). This reduces the effective
127 :     * set of 64bit odd gamma values by about 2%, and serves as an
128 : dl 1.15 * automated screening for sequence constant selection that is
129 :     * left as an empirical decision in some other hashing and crypto
130 :     * algorithms.
131 :     *
132 :     * The resulting generator thus transforms a sequence in which
133 :     * (typically) many bits change on each step, with an inexpensive
134 :     * mixer with good (but less than cryptographically secure)
135 :     * avalanching.
136 :     *
137 :     * The default (no-argument) constructor, in essence, invokes
138 : dl 1.21 * split() for a common "defaultGen" SplittableRandom. Unlike
139 :     * other cases, this split must be performed in a thread-safe
140 :     * manner, so we use an AtomicLong to represent the seed rather
141 :     * than use an explicit SplittableRandom. To bootstrap the
142 : dl 1.25 * defaultGen, we start off using a seed based on current time
143 :     * unless the java.util.secureRandomSeed property is set. This
144 :     * serves as a slimmed-down (and insecure) variant of SecureRandom
145 :     * that also avoids stalls that may occur when using /dev/random.
146 : dl 1.15 *
147 :     * It is a relatively simple matter to apply the basic design here
148 :     * to use 128 bit seeds. However, emulating 128bit arithmetic and
149 :     * carrying around twice the state add more overhead than appears
150 :     * warranted for current usages.
151 : dl 1.13 *
152 : dl 1.15 * File organization: First the non-public methods that constitute
153 :     * the main algorithm, then the main public methods, followed by
154 :     * some custom spliterator classes needed for stream methods.
155 : dl 1.1 */
156 :    
157 :     /**
158 : dl 1.21 * The golden ratio scaled to 64bits, used as the initial gamma
159 :     * value for (unsplit) SplittableRandoms.
160 : dl 1.1 */
161 : dl 1.21 private static final long GOLDEN_GAMMA = 0x9e3779b97f4a7c15L;
162 : dl 1.11
163 :     /**
164 : dl 1.5 * The least non-zero value returned by nextDouble(). This value
165 : dl 1.7 * is scaled by a random value of 53 bits to produce a result.
166 : dl 1.5 */
167 : dl 1.24 private static final double DOUBLE_UNIT = 0x1.0p-53; // 1.0 / (1L << 53);
168 : dl 1.5
169 :     /**
170 : dl 1.15 * The seed. Updated only via method nextSeed.
171 : dl 1.1 */
172 :     private long seed;
173 :    
174 :     /**
175 : dl 1.15 * The step value.
176 : dl 1.1 */
177 :     private final long gamma;
178 :    
179 :     /**
180 : dl 1.15 * Internal constructor used by all others except default constructor.
181 : dl 1.1 */
182 : dl 1.15 private SplittableRandom(long seed, long gamma) {
183 :     this.seed = seed;
184 :     this.gamma = gamma;
185 : dl 1.1 }
186 :    
187 :     /**
188 : dl 1.21 * Computes Stafford variant 13 of 64bit mix function.
189 : dl 1.1 */
190 :     private static long mix64(long z) {
191 : dl 1.24 z = (z ^ (z >>> 30)) * 0xbf58476d1ce4e5b9L;
192 :     z = (z ^ (z >>> 27)) * 0x94d049bb133111ebL;
193 :     return z ^ (z >>> 31);
194 : dl 1.21 }
195 :    
196 : dl 1.1 /**
197 : dl 1.21 * Returns the 32 high bits of Stafford variant 4 mix64 function as int.
198 : dl 1.1 */
199 :     private static int mix32(long z) {
200 : dl 1.24 z = (z ^ (z >>> 33)) * 0x62a9d9ed799705f5L;
201 : dl 1.21 return (int)(((z ^ (z >>> 28)) * 0xcb24d0a5c88c35b3L) >>> 32);
202 : dl 1.1 }
203 :    
204 :     /**
205 : dl 1.15 * Returns the gamma value to use for a new split instance.
206 : dl 1.13 */
207 : dl 1.21 private static long mixGamma(long z) {
208 : dl 1.24 z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL; // MurmurHash3 mix constants
209 : dl 1.21 z = (z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L;
210 :     z = (z ^ (z >>> 33)) | 1L; // force to be odd
211 :     int n = Long.bitCount(z ^ (z >>> 1)); // ensure enough transitions
212 :     return (n < 24) ? z ^ 0xaaaaaaaaaaaaaaaaL : z;
213 : dl 1.13 }
214 :    
215 :     /**
216 : dl 1.15 * Adds gamma to seed.
217 : dl 1.7 */
218 : dl 1.15 private long nextSeed() {
219 :     return seed += gamma;
220 : dl 1.7 }
221 :    
222 : jsr166 1.32 // IllegalArgumentException messages
223 :     static final String BAD_BOUND = "bound must be positive";
224 :     static final String BAD_RANGE = "bound must be greater than origin";
225 :     static final String BAD_SIZE = "size must be non-negative";
226 :    
227 : dl 1.7 /**
228 : dl 1.15 * The seed generator for default constructors.
229 : dl 1.7 */
230 : jsr166 1.32 private static final AtomicLong defaultGen
231 :     = new AtomicLong(mix64(System.currentTimeMillis()) ^
232 :     mix64(System.nanoTime()));
233 : dl 1.7
234 : jsr166 1.32 // at end of <clinit> to survive static initialization circularity
235 :     static {
236 : jsr166 1.31 if (java.security.AccessController.doPrivileged(
237 :     new java.security.PrivilegedAction<Boolean>() {
238 :     public Boolean run() {
239 :     return Boolean.getBoolean("java.util.secureRandomSeed");
240 :     }})) {
241 : dl 1.21 byte[] seedBytes = java.security.SecureRandom.getSeed(8);
242 : jsr166 1.30 long s = (long)seedBytes[0] & 0xffL;
243 : dl 1.21 for (int i = 1; i < 8; ++i)
244 : jsr166 1.30 s = (s << 8) | ((long)seedBytes[i] & 0xffL);
245 : jsr166 1.32 defaultGen.set(s);
246 : dl 1.18 }
247 : dl 1.1 }
248 :    
249 :     /*
250 :     * Internal versions of nextX methods used by streams, as well as
251 :     * the public nextX(origin, bound) methods. These exist mainly to
252 :     * avoid the need for multiple versions of stream spliterators
253 :     * across the different exported forms of streams.
254 :     */
255 :    
256 :     /**
257 :     * The form of nextLong used by LongStream Spliterators. If
258 :     * origin is greater than bound, acts as unbounded form of
259 :     * nextLong, else as bounded form.
260 :     *
261 :     * @param origin the least value, unless greater than bound
262 :     * @param bound the upper bound (exclusive), must not equal origin
263 :     * @return a pseudorandom value
264 :     */
265 :     final long internalNextLong(long origin, long bound) {
266 :     /*
267 :     * Four Cases:
268 :     *
269 :     * 1. If the arguments indicate unbounded form, act as
270 :     * nextLong().
271 :     *
272 :     * 2. If the range is an exact power of two, apply the
273 :     * associated bit mask.
274 :     *
275 :     * 3. If the range is positive, loop to avoid potential bias
276 :     * when the implicit nextLong() bound (2<sup>64</sup>) is not
277 :     * evenly divisible by the range. The loop rejects candidates
278 :     * computed from otherwise over-represented values. The
279 :     * expected number of iterations under an ideal generator
280 : dl 1.4 * varies from 1 to 2, depending on the bound. The loop itself
281 :     * takes an unlovable form. Because the first candidate is
282 :     * already available, we need a break-in-the-middle
283 :     * construction, which is concisely but cryptically performed
284 :     * within the while-condition of a body-less for loop.
285 : dl 1.1 *
286 :     * 4. Otherwise, the range cannot be represented as a positive
287 : dl 1.4 * long. The loop repeatedly generates unbounded longs until
288 :     * obtaining a candidate meeting constraints (with an expected
289 :     * number of iterations of less than two).
290 : dl 1.1 */
291 :    
292 :     long r = mix64(nextSeed());
293 :     if (origin < bound) {
294 :     long n = bound - origin, m = n - 1;
295 : dl 1.7 if ((n & m) == 0L) // power of two
296 : dl 1.1 r = (r & m) + origin;
297 : dl 1.7 else if (n > 0L) { // reject over-represented candidates
298 : dl 1.1 for (long u = r >>> 1; // ensure nonnegative
299 : dl 1.7 u + m - (r = u % n) < 0L; // rejection check
300 : dl 1.1 u = mix64(nextSeed()) >>> 1) // retry
301 :     ;
302 :     r += origin;
303 :     }
304 : dl 1.7 else { // range not representable as long
305 : dl 1.1 while (r < origin || r >= bound)
306 :     r = mix64(nextSeed());
307 :     }
308 :     }
309 :     return r;
310 :     }
311 :    
312 :     /**
313 :     * The form of nextInt used by IntStream Spliterators.
314 :     * Exactly the same as long version, except for types.
315 :     *
316 :     * @param origin the least value, unless greater than bound
317 :     * @param bound the upper bound (exclusive), must not equal origin
318 :     * @return a pseudorandom value
319 :     */
320 :     final int internalNextInt(int origin, int bound) {
321 :     int r = mix32(nextSeed());
322 :     if (origin < bound) {
323 :     int n = bound - origin, m = n - 1;
324 : dl 1.13 if ((n & m) == 0)
325 : dl 1.1 r = (r & m) + origin;
326 :     else if (n > 0) {
327 :     for (int u = r >>> 1;
328 : dl 1.7 u + m - (r = u % n) < 0;
329 : dl 1.1 u = mix32(nextSeed()) >>> 1)
330 :     ;
331 :     r += origin;
332 :     }
333 :     else {
334 :     while (r < origin || r >= bound)
335 :     r = mix32(nextSeed());
336 :     }
337 :     }
338 :     return r;
339 :     }
340 :    
341 :     /**
342 :     * The form of nextDouble used by DoubleStream Spliterators.
343 :     *
344 :     * @param origin the least value, unless greater than bound
345 :     * @param bound the upper bound (exclusive), must not equal origin
346 :     * @return a pseudorandom value
347 :     */
348 :     final double internalNextDouble(double origin, double bound) {
349 : dl 1.24 double r = (nextLong() >>> 11) * DOUBLE_UNIT;
350 : dl 1.1 if (origin < bound) {
351 :     r = r * (bound - origin) + origin;
352 : dl 1.7 if (r >= bound) // correct for rounding
353 : dl 1.1 r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
354 :     }
355 :     return r;
356 :     }
357 :    
358 :     /* ---------------- public methods ---------------- */
359 :    
360 :     /**
361 : dl 1.7 * Creates a new SplittableRandom instance using the specified
362 :     * initial seed. SplittableRandom instances created with the same
363 : dl 1.11 * seed in the same program generate identical sequences of values.
364 : dl 1.1 *
365 :     * @param seed the initial seed
366 :     */
367 :     public SplittableRandom(long seed) {
368 : dl 1.21 this(seed, GOLDEN_GAMMA);
369 : dl 1.1 }
370 :    
371 :     /**
372 :     * Creates a new SplittableRandom instance that is likely to
373 :     * generate sequences of values that are statistically independent
374 :     * of those of any other instances in the current program; and
375 :     * may, and typically does, vary across program invocations.
376 :     */
377 : dl 1.21 public SplittableRandom() { // emulate defaultGen.split()
378 : jsr166 1.38 long s = defaultGen.getAndAdd(GOLDEN_GAMMA << 1);
379 : dl 1.21 this.seed = mix64(s);
380 :     this.gamma = mixGamma(s + GOLDEN_GAMMA);
381 : dl 1.1 }
382 :    
383 :     /**
384 :     * Constructs and returns a new SplittableRandom instance that
385 :     * shares no mutable state with this instance. However, with very
386 :     * high probability, the set of values collectively generated by
387 :     * the two objects has the same statistical properties as if the
388 :     * same quantity of values were generated by a single thread using
389 :     * a single SplittableRandom object. Either or both of the two
390 :     * objects may be further split using the {@code split()} method,
391 :     * and the same expected statistical properties apply to the
392 :     * entire set of generators constructed by such recursive
393 :     * splitting.
394 :     *
395 :     * @return the new SplittableRandom instance
396 :     */
397 :     public SplittableRandom split() {
398 : dl 1.21 return new SplittableRandom(nextLong(), mixGamma(nextSeed()));
399 : dl 1.1 }
400 :    
401 :     /**
402 : jsr166 1.40 * Fills a user-supplied byte array with generated pseudorandom bytes.
403 :     *
404 :     * @param bytes the byte array to fill with pseudorandom bytes
405 :     * @throws NullPointerException if bytes is null
406 :     * @since 10
407 :     */
408 :     public void nextBytes(byte[] bytes) {
409 :     int i = 0;
410 :     int len = bytes.length;
411 :     for (int words = len >> 3; words--> 0; ) {
412 :     long rnd = nextLong();
413 :     for (int n = 8; n--> 0; rnd >>>= Byte.SIZE)
414 :     bytes[i++] = (byte)rnd;
415 :     }
416 :     if (i < len)
417 :     for (long rnd = nextLong(); i < len; rnd >>>= Byte.SIZE)
418 :     bytes[i++] = (byte)rnd;
419 :     }
420 :    
421 :     /**
422 : dl 1.1 * Returns a pseudorandom {@code int} value.
423 :     *
424 : dl 1.7 * @return a pseudorandom {@code int} value
425 : dl 1.1 */
426 :     public int nextInt() {
427 :     return mix32(nextSeed());
428 :     }
429 :    
430 :     /**
431 : dl 1.7 * Returns a pseudorandom {@code int} value between zero (inclusive)
432 : dl 1.1 * and the specified bound (exclusive).
433 :     *
434 : dl 1.18 * @param bound the upper bound (exclusive). Must be positive.
435 : dl 1.7 * @return a pseudorandom {@code int} value between zero
436 : jsr166 1.10 * (inclusive) and the bound (exclusive)
437 : dl 1.16 * @throws IllegalArgumentException if {@code bound} is not positive
438 : dl 1.1 */
439 :     public int nextInt(int bound) {
440 :     if (bound <= 0)
441 : jsr166 1.28 throw new IllegalArgumentException(BAD_BOUND);
442 : dl 1.1 // Specialize internalNextInt for origin 0
443 :     int r = mix32(nextSeed());
444 :     int m = bound - 1;
445 : dl 1.13 if ((bound & m) == 0) // power of two
446 : dl 1.1 r &= m;
447 :     else { // reject over-represented candidates
448 :     for (int u = r >>> 1;
449 : dl 1.7 u + m - (r = u % bound) < 0;
450 : dl 1.1 u = mix32(nextSeed()) >>> 1)
451 :     ;
452 :     }
453 :     return r;
454 :     }
455 :    
456 :     /**
457 :     * Returns a pseudorandom {@code int} value between the specified
458 :     * origin (inclusive) and the specified bound (exclusive).
459 :     *
460 :     * @param origin the least value returned
461 :     * @param bound the upper bound (exclusive)
462 :     * @return a pseudorandom {@code int} value between the origin
463 : jsr166 1.10 * (inclusive) and the bound (exclusive)
464 : dl 1.7 * @throws IllegalArgumentException if {@code origin} is greater than
465 : dl 1.1 * or equal to {@code bound}
466 :     */
467 :     public int nextInt(int origin, int bound) {
468 :     if (origin >= bound)
469 : jsr166 1.28 throw new IllegalArgumentException(BAD_RANGE);
470 : dl 1.1 return internalNextInt(origin, bound);
471 :     }
472 :    
473 :     /**
474 :     * Returns a pseudorandom {@code long} value.
475 :     *
476 : dl 1.7 * @return a pseudorandom {@code long} value
477 : dl 1.1 */
478 :     public long nextLong() {
479 :     return mix64(nextSeed());
480 :     }
481 :    
482 :     /**
483 : dl 1.7 * Returns a pseudorandom {@code long} value between zero (inclusive)
484 : dl 1.1 * and the specified bound (exclusive).
485 :     *
486 : dl 1.18 * @param bound the upper bound (exclusive). Must be positive.
487 : dl 1.7 * @return a pseudorandom {@code long} value between zero
488 : jsr166 1.10 * (inclusive) and the bound (exclusive)
489 : dl 1.16 * @throws IllegalArgumentException if {@code bound} is not positive
490 : dl 1.1 */
491 :     public long nextLong(long bound) {
492 :     if (bound <= 0)
493 : jsr166 1.28 throw new IllegalArgumentException(BAD_BOUND);
494 : dl 1.1 // Specialize internalNextLong for origin 0
495 :     long r = mix64(nextSeed());
496 :     long m = bound - 1;
497 :     if ((bound & m) == 0L) // power of two
498 :     r &= m;
499 :     else { // reject over-represented candidates
500 :     for (long u = r >>> 1;
501 :     u + m - (r = u % bound) < 0L;
502 :     u = mix64(nextSeed()) >>> 1)
503 :     ;
504 :     }
505 :     return r;
506 :     }
507 :    
508 :     /**
509 :     * Returns a pseudorandom {@code long} value between the specified
510 :     * origin (inclusive) and the specified bound (exclusive).
511 :     *
512 :     * @param origin the least value returned
513 :     * @param bound the upper bound (exclusive)
514 :     * @return a pseudorandom {@code long} value between the origin
515 : jsr166 1.10 * (inclusive) and the bound (exclusive)
516 : dl 1.7 * @throws IllegalArgumentException if {@code origin} is greater than
517 : dl 1.1 * or equal to {@code bound}
518 :     */
519 :     public long nextLong(long origin, long bound) {
520 :     if (origin >= bound)
521 : jsr166 1.28 throw new IllegalArgumentException(BAD_RANGE);
522 : dl 1.1 return internalNextLong(origin, bound);
523 :     }
524 :    
525 :     /**
526 : dl 1.7 * Returns a pseudorandom {@code double} value between zero
527 :     * (inclusive) and one (exclusive).
528 : dl 1.1 *
529 : dl 1.7 * @return a pseudorandom {@code double} value between zero
530 : dl 1.18 * (inclusive) and one (exclusive)
531 : dl 1.1 */
532 :     public double nextDouble() {
533 : dl 1.24 return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT;
534 : dl 1.1 }
535 :    
536 :     /**
537 :     * Returns a pseudorandom {@code double} value between 0.0
538 :     * (inclusive) and the specified bound (exclusive).
539 :     *
540 : dl 1.18 * @param bound the upper bound (exclusive). Must be positive.
541 : dl 1.7 * @return a pseudorandom {@code double} value between zero
542 : jsr166 1.10 * (inclusive) and the bound (exclusive)
543 : dl 1.16 * @throws IllegalArgumentException if {@code bound} is not positive
544 : dl 1.1 */
545 :     public double nextDouble(double bound) {
546 : dl 1.7 if (!(bound > 0.0))
547 : jsr166 1.28 throw new IllegalArgumentException(BAD_BOUND);
548 : dl 1.24 double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound;
549 : dl 1.1 return (result < bound) ? result : // correct for rounding
550 :     Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
551 :     }
552 :    
553 : jsr166 1.34 /**
554 : dl 1.7 * Returns a pseudorandom {@code double} value between the specified
555 : dl 1.1 * origin (inclusive) and bound (exclusive).
556 :     *
557 :     * @param origin the least value returned
558 : dl 1.18 * @param bound the upper bound (exclusive)
559 : dl 1.1 * @return a pseudorandom {@code double} value between the origin
560 : jsr166 1.10 * (inclusive) and the bound (exclusive)
561 : dl 1.1 * @throws IllegalArgumentException if {@code origin} is greater than
562 :     * or equal to {@code bound}
563 :     */
564 :     public double nextDouble(double origin, double bound) {
565 : dl 1.7 if (!(origin < bound))
566 : jsr166 1.28 throw new IllegalArgumentException(BAD_RANGE);
567 : dl 1.1 return internalNextDouble(origin, bound);
568 :     }
569 :    
570 : dl 1.11 /**
571 :     * Returns a pseudorandom {@code boolean} value.
572 :     *
573 :     * @return a pseudorandom {@code boolean} value
574 :     */
575 :     public boolean nextBoolean() {
576 :     return mix32(nextSeed()) < 0;
577 :     }
578 :    
579 : dl 1.1 // stream methods, coded in a way intended to better isolate for
580 :     // maintenance purposes the small differences across forms.
581 :    
582 :     /**
583 : dl 1.16 * Returns a stream producing the given {@code streamSize} number
584 :     * of pseudorandom {@code int} values from this generator and/or
585 :     * one split from it.
586 : dl 1.1 *
587 :     * @param streamSize the number of values to generate
588 :     * @return a stream of pseudorandom {@code int} values
589 :     * @throws IllegalArgumentException if {@code streamSize} is
590 : dl 1.7 * less than zero
591 : dl 1.1 */
592 :     public IntStream ints(long streamSize) {
593 :     if (streamSize < 0L)
594 : jsr166 1.28 throw new IllegalArgumentException(BAD_SIZE);
595 : dl 1.1 return StreamSupport.intStream
596 :     (new RandomIntsSpliterator
597 :     (this, 0L, streamSize, Integer.MAX_VALUE, 0),
598 :     false);
599 :     }
600 :    
601 :     /**
602 :     * Returns an effectively unlimited stream of pseudorandom {@code int}
603 : dl 1.16 * values from this generator and/or one split from it.
604 : dl 1.1 *
605 :     * @implNote This method is implemented to be equivalent to {@code
606 :     * ints(Long.MAX_VALUE)}.
607 :     *
608 :     * @return a stream of pseudorandom {@code int} values
609 :     */
610 :     public IntStream ints() {
611 :     return StreamSupport.intStream
612 :     (new RandomIntsSpliterator
613 :     (this, 0L, Long.MAX_VALUE, Integer.MAX_VALUE, 0),
614 :     false);
615 :     }
616 :    
617 :     /**
618 : dl 1.16 * Returns a stream producing the given {@code streamSize} number
619 : dl 1.18 * of pseudorandom {@code int} values from this generator and/or one split
620 :     * from it; each value conforms to the given origin (inclusive) and bound
621 :     * (exclusive).
622 : dl 1.1 *
623 :     * @param streamSize the number of values to generate
624 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
625 :     * @param randomNumberBound the bound (exclusive) of each random value
626 : dl 1.1 * @return a stream of pseudorandom {@code int} values,
627 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
628 : dl 1.1 * @throws IllegalArgumentException if {@code streamSize} is
629 : dl 1.7 * less than zero, or {@code randomNumberOrigin}
630 : dl 1.1 * is greater than or equal to {@code randomNumberBound}
631 :     */
632 :     public IntStream ints(long streamSize, int randomNumberOrigin,
633 :     int randomNumberBound) {
634 :     if (streamSize < 0L)
635 : jsr166 1.28 throw new IllegalArgumentException(BAD_SIZE);
636 : dl 1.1 if (randomNumberOrigin >= randomNumberBound)
637 : jsr166 1.28 throw new IllegalArgumentException(BAD_RANGE);
638 : dl 1.1 return StreamSupport.intStream
639 :     (new RandomIntsSpliterator
640 :     (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
641 :     false);
642 :     }
643 :    
644 :     /**
645 :     * Returns an effectively unlimited stream of pseudorandom {@code
646 : dl 1.18 * int} values from this generator and/or one split from it; each value
647 :     * conforms to the given origin (inclusive) and bound (exclusive).
648 : dl 1.1 *
649 :     * @implNote This method is implemented to be equivalent to {@code
650 :     * ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
651 :     *
652 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
653 :     * @param randomNumberBound the bound (exclusive) of each random value
654 : dl 1.1 * @return a stream of pseudorandom {@code int} values,
655 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
656 : dl 1.1 * @throws IllegalArgumentException if {@code randomNumberOrigin}
657 :     * is greater than or equal to {@code randomNumberBound}
658 :     */
659 :     public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
660 :     if (randomNumberOrigin >= randomNumberBound)
661 : jsr166 1.28 throw new IllegalArgumentException(BAD_RANGE);
662 : dl 1.1 return StreamSupport.intStream
663 :     (new RandomIntsSpliterator
664 :     (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
665 :     false);
666 :     }
667 :    
668 :     /**
669 : dl 1.16 * Returns a stream producing the given {@code streamSize} number
670 :     * of pseudorandom {@code long} values from this generator and/or
671 :     * one split from it.
672 : dl 1.1 *
673 :     * @param streamSize the number of values to generate
674 : dl 1.7 * @return a stream of pseudorandom {@code long} values
675 : dl 1.1 * @throws IllegalArgumentException if {@code streamSize} is
676 : dl 1.7 * less than zero
677 : dl 1.1 */
678 :     public LongStream longs(long streamSize) {
679 :     if (streamSize < 0L)
680 : jsr166 1.28 throw new IllegalArgumentException(BAD_SIZE);
681 : dl 1.1 return StreamSupport.longStream
682 :     (new RandomLongsSpliterator
683 :     (this, 0L, streamSize, Long.MAX_VALUE, 0L),
684 :     false);
685 :     }
686 :    
687 :     /**
688 : dl 1.16 * Returns an effectively unlimited stream of pseudorandom {@code
689 :     * long} values from this generator and/or one split from it.
690 : dl 1.1 *
691 :     * @implNote This method is implemented to be equivalent to {@code
692 :     * longs(Long.MAX_VALUE)}.
693 :     *
694 :     * @return a stream of pseudorandom {@code long} values
695 :     */
696 :     public LongStream longs() {
697 :     return StreamSupport.longStream
698 :     (new RandomLongsSpliterator
699 :     (this, 0L, Long.MAX_VALUE, Long.MAX_VALUE, 0L),
700 :     false);
701 :     }
702 :    
703 :     /**
704 : dl 1.7 * Returns a stream producing the given {@code streamSize} number of
705 : dl 1.18 * pseudorandom {@code long} values from this generator and/or one split
706 :     * from it; each value conforms to the given origin (inclusive) and bound
707 :     * (exclusive).
708 : dl 1.1 *
709 :     * @param streamSize the number of values to generate
710 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
711 :     * @param randomNumberBound the bound (exclusive) of each random value
712 : dl 1.1 * @return a stream of pseudorandom {@code long} values,
713 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
714 : dl 1.1 * @throws IllegalArgumentException if {@code streamSize} is
715 : dl 1.7 * less than zero, or {@code randomNumberOrigin}
716 : dl 1.1 * is greater than or equal to {@code randomNumberBound}
717 :     */
718 :     public LongStream longs(long streamSize, long randomNumberOrigin,
719 :     long randomNumberBound) {
720 :     if (streamSize < 0L)
721 : jsr166 1.28 throw new IllegalArgumentException(BAD_SIZE);
722 : dl 1.1 if (randomNumberOrigin >= randomNumberBound)
723 : jsr166 1.28 throw new IllegalArgumentException(BAD_RANGE);
724 : dl 1.1 return StreamSupport.longStream
725 :     (new RandomLongsSpliterator
726 :     (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
727 :     false);
728 :     }
729 :    
730 :     /**
731 :     * Returns an effectively unlimited stream of pseudorandom {@code
732 : dl 1.18 * long} values from this generator and/or one split from it; each value
733 :     * conforms to the given origin (inclusive) and bound (exclusive).
734 : dl 1.1 *
735 :     * @implNote This method is implemented to be equivalent to {@code
736 :     * longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
737 :     *
738 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
739 :     * @param randomNumberBound the bound (exclusive) of each random value
740 : dl 1.1 * @return a stream of pseudorandom {@code long} values,
741 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
742 : dl 1.1 * @throws IllegalArgumentException if {@code randomNumberOrigin}
743 :     * is greater than or equal to {@code randomNumberBound}
744 :     */
745 :     public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
746 :     if (randomNumberOrigin >= randomNumberBound)
747 : jsr166 1.28 throw new IllegalArgumentException(BAD_RANGE);
748 : dl 1.1 return StreamSupport.longStream
749 :     (new RandomLongsSpliterator
750 :     (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
751 :     false);
752 :     }
753 :    
754 :     /**
755 : dl 1.7 * Returns a stream producing the given {@code streamSize} number of
756 : dl 1.18 * pseudorandom {@code double} values from this generator and/or one split
757 :     * from it; each value is between zero (inclusive) and one (exclusive).
758 : dl 1.1 *
759 :     * @param streamSize the number of values to generate
760 :     * @return a stream of {@code double} values
761 :     * @throws IllegalArgumentException if {@code streamSize} is
762 : dl 1.7 * less than zero
763 : dl 1.1 */
764 :     public DoubleStream doubles(long streamSize) {
765 :     if (streamSize < 0L)
766 : jsr166 1.28 throw new IllegalArgumentException(BAD_SIZE);
767 : dl 1.1 return StreamSupport.doubleStream
768 :     (new RandomDoublesSpliterator
769 :     (this, 0L, streamSize, Double.MAX_VALUE, 0.0),
770 :     false);
771 :     }
772 :    
773 :     /**
774 :     * Returns an effectively unlimited stream of pseudorandom {@code
775 : dl 1.18 * double} values from this generator and/or one split from it; each value
776 :     * is between zero (inclusive) and one (exclusive).
777 : dl 1.1 *
778 :     * @implNote This method is implemented to be equivalent to {@code
779 :     * doubles(Long.MAX_VALUE)}.
780 :     *
781 :     * @return a stream of pseudorandom {@code double} values
782 :     */
783 :     public DoubleStream doubles() {
784 :     return StreamSupport.doubleStream
785 :     (new RandomDoublesSpliterator
786 :     (this, 0L, Long.MAX_VALUE, Double.MAX_VALUE, 0.0),
787 :     false);
788 :     }
789 :    
790 :     /**
791 : dl 1.7 * Returns a stream producing the given {@code streamSize} number of
792 : dl 1.18 * pseudorandom {@code double} values from this generator and/or one split
793 :     * from it; each value conforms to the given origin (inclusive) and bound
794 :     * (exclusive).
795 : dl 1.1 *
796 :     * @param streamSize the number of values to generate
797 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
798 :     * @param randomNumberBound the bound (exclusive) of each random value
799 : dl 1.1 * @return a stream of pseudorandom {@code double} values,
800 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
801 : dl 1.1 * @throws IllegalArgumentException if {@code streamSize} is
802 : jsr166 1.39 * less than zero, or {@code randomNumberOrigin}
803 : dl 1.1 * is greater than or equal to {@code randomNumberBound}
804 :     */
805 :     public DoubleStream doubles(long streamSize, double randomNumberOrigin,
806 :     double randomNumberBound) {
807 :     if (streamSize < 0L)
808 : jsr166 1.28 throw new IllegalArgumentException(BAD_SIZE);
809 : dl 1.7 if (!(randomNumberOrigin < randomNumberBound))
810 : jsr166 1.28 throw new IllegalArgumentException(BAD_RANGE);
811 : dl 1.1 return StreamSupport.doubleStream
812 :     (new RandomDoublesSpliterator
813 :     (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
814 :     false);
815 :     }
816 :    
817 :     /**
818 :     * Returns an effectively unlimited stream of pseudorandom {@code
819 : dl 1.18 * double} values from this generator and/or one split from it; each value
820 :     * conforms to the given origin (inclusive) and bound (exclusive).
821 : dl 1.1 *
822 :     * @implNote This method is implemented to be equivalent to {@code
823 :     * doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
824 :     *
825 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
826 :     * @param randomNumberBound the bound (exclusive) of each random value
827 : dl 1.1 * @return a stream of pseudorandom {@code double} values,
828 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
829 : dl 1.1 * @throws IllegalArgumentException if {@code randomNumberOrigin}
830 :     * is greater than or equal to {@code randomNumberBound}
831 :     */
832 :     public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
833 : dl 1.7 if (!(randomNumberOrigin < randomNumberBound))
834 : jsr166 1.28 throw new IllegalArgumentException(BAD_RANGE);
835 : dl 1.1 return StreamSupport.doubleStream
836 :     (new RandomDoublesSpliterator
837 :     (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
838 :     false);
839 :     }
840 :    
841 :     /**
842 :     * Spliterator for int streams. We multiplex the four int
843 : dl 1.7 * versions into one class by treating a bound less than origin as
844 : dl 1.1 * unbounded, and also by treating "infinite" as equivalent to
845 :     * Long.MAX_VALUE. For splits, it uses the standard divide-by-two
846 :     * approach. The long and double versions of this class are
847 :     * identical except for types.
848 :     */
849 : jsr166 1.29 private static final class RandomIntsSpliterator
850 :     implements Spliterator.OfInt {
851 : dl 1.1 final SplittableRandom rng;
852 :     long index;
853 :     final long fence;
854 :     final int origin;
855 :     final int bound;
856 :     RandomIntsSpliterator(SplittableRandom rng, long index, long fence,
857 :     int origin, int bound) {
858 :     this.rng = rng; this.index = index; this.fence = fence;
859 :     this.origin = origin; this.bound = bound;
860 :     }
861 :    
862 :     public RandomIntsSpliterator trySplit() {
863 :     long i = index, m = (i + fence) >>> 1;
864 :     return (m <= i) ? null :
865 :     new RandomIntsSpliterator(rng.split(), i, index = m, origin, bound);
866 :     }
867 :    
868 :     public long estimateSize() {
869 :     return fence - index;
870 :     }
871 :    
872 :     public int characteristics() {
873 :     return (Spliterator.SIZED | Spliterator.SUBSIZED |
874 : dl 1.4 Spliterator.NONNULL | Spliterator.IMMUTABLE);
875 : dl 1.1 }
876 :    
877 :     public boolean tryAdvance(IntConsumer consumer) {
878 :     if (consumer == null) throw new NullPointerException();
879 :     long i = index, f = fence;
880 :     if (i < f) {
881 :     consumer.accept(rng.internalNextInt(origin, bound));
882 :     index = i + 1;
883 :     return true;
884 :     }
885 :     return false;
886 :     }
887 :    
888 :     public void forEachRemaining(IntConsumer consumer) {
889 :     if (consumer == null) throw new NullPointerException();
890 :     long i = index, f = fence;
891 :     if (i < f) {
892 :     index = f;
893 : dl 1.15 SplittableRandom r = rng;
894 : dl 1.1 int o = origin, b = bound;
895 :     do {
896 : dl 1.15 consumer.accept(r.internalNextInt(o, b));
897 : dl 1.1 } while (++i < f);
898 :     }
899 :     }
900 :     }
901 :    
902 :     /**
903 :     * Spliterator for long streams.
904 :     */
905 : jsr166 1.29 private static final class RandomLongsSpliterator
906 :     implements Spliterator.OfLong {
907 : dl 1.1 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 : dl 1.15 SplittableRandom r = rng;
950 : dl 1.1 long o = origin, b = bound;
951 :     do {
952 : dl 1.15 consumer.accept(r.internalNextLong(o, b));
953 : dl 1.1 } while (++i < f);
954 :     }
955 :     }
956 :    
957 :     }
958 :    
959 :     /**
960 :     * Spliterator for double streams.
961 :     */
962 : jsr166 1.29 private static final class RandomDoublesSpliterator
963 :     implements Spliterator.OfDouble {
964 : dl 1.1 final SplittableRandom rng;
965 :     long index;
966 :     final long fence;
967 :     final double origin;
968 :     final double bound;
969 :     RandomDoublesSpliterator(SplittableRandom rng, long index, long fence,
970 :     double origin, double bound) {
971 :     this.rng = rng; this.index = index; this.fence = fence;
972 :     this.origin = origin; this.bound = bound;
973 :     }
974 :    
975 :     public RandomDoublesSpliterator trySplit() {
976 :     long i = index, m = (i + fence) >>> 1;
977 :     return (m <= i) ? null :
978 :     new RandomDoublesSpliterator(rng.split(), i, index = m, origin, bound);
979 :     }
980 :    
981 :     public long estimateSize() {
982 :     return fence - index;
983 :     }
984 :    
985 :     public int characteristics() {
986 :     return (Spliterator.SIZED | Spliterator.SUBSIZED |
987 : dl 1.4 Spliterator.NONNULL | Spliterator.IMMUTABLE);
988 : dl 1.1 }
989 :    
990 :     public boolean tryAdvance(DoubleConsumer consumer) {
991 :     if (consumer == null) throw new NullPointerException();
992 :     long i = index, f = fence;
993 :     if (i < f) {
994 :     consumer.accept(rng.internalNextDouble(origin, bound));
995 :     index = i + 1;
996 :     return true;
997 :     }
998 :     return false;
999 :     }
1000 :    
1001 :     public void forEachRemaining(DoubleConsumer consumer) {
1002 :     if (consumer == null) throw new NullPointerException();
1003 :     long i = index, f = fence;
1004 :     if (i < f) {
1005 :     index = f;
1006 : dl 1.15 SplittableRandom r = rng;
1007 : dl 1.1 double o = origin, b = bound;
1008 :     do {
1009 : dl 1.15 consumer.accept(r.internalNextDouble(o, b));
1010 : dl 1.1 } while (++i < f);
1011 :     }
1012 :     }
1013 :     }
1014 :    
1015 :     }

Doug Lea
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