[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 1.30 - (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 : 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 :     /**
223 : dl 1.15 * The seed generator for default constructors.
224 : dl 1.7 */
225 : dl 1.21 private static final AtomicLong defaultGen = new AtomicLong(initialSeed());
226 : dl 1.7
227 : dl 1.18 private static long initialSeed() {
228 : jsr166 1.30 java.security.PrivilegedAction<Boolean> action =
229 :     () -> Boolean.getBoolean("java.util.secureRandomSeed");
230 :     if (java.security.AccessController.doPrivileged(action)) {
231 : dl 1.21 byte[] seedBytes = java.security.SecureRandom.getSeed(8);
232 : jsr166 1.30 long s = (long)seedBytes[0] & 0xffL;
233 : dl 1.21 for (int i = 1; i < 8; ++i)
234 : jsr166 1.30 s = (s << 8) | ((long)seedBytes[i] & 0xffL);
235 : dl 1.21 return s;
236 : dl 1.18 }
237 : dl 1.25 return (mix64(System.currentTimeMillis()) ^
238 : dl 1.18 mix64(System.nanoTime()));
239 : dl 1.1 }
240 :    
241 : dl 1.15 // IllegalArgumentException messages
242 : jsr166 1.28 static final String BAD_BOUND = "bound must be positive";
243 :     static final String BAD_RANGE = "bound must be greater than origin";
244 :     static final String BAD_SIZE = "size must be non-negative";
245 : dl 1.12
246 : dl 1.1 /*
247 :     * Internal versions of nextX methods used by streams, as well as
248 :     * the public nextX(origin, bound) methods. These exist mainly to
249 :     * avoid the need for multiple versions of stream spliterators
250 :     * across the different exported forms of streams.
251 :     */
252 :    
253 :     /**
254 :     * The form of nextLong used by LongStream Spliterators. If
255 :     * origin is greater than bound, acts as unbounded form of
256 :     * nextLong, else as bounded form.
257 :     *
258 :     * @param origin the least value, unless greater than bound
259 :     * @param bound the upper bound (exclusive), must not equal origin
260 :     * @return a pseudorandom value
261 :     */
262 :     final long internalNextLong(long origin, long bound) {
263 :     /*
264 :     * Four Cases:
265 :     *
266 :     * 1. If the arguments indicate unbounded form, act as
267 :     * nextLong().
268 :     *
269 :     * 2. If the range is an exact power of two, apply the
270 :     * associated bit mask.
271 :     *
272 :     * 3. If the range is positive, loop to avoid potential bias
273 :     * when the implicit nextLong() bound (2<sup>64</sup>) is not
274 :     * evenly divisible by the range. The loop rejects candidates
275 :     * computed from otherwise over-represented values. The
276 :     * expected number of iterations under an ideal generator
277 : dl 1.4 * varies from 1 to 2, depending on the bound. The loop itself
278 :     * takes an unlovable form. Because the first candidate is
279 :     * already available, we need a break-in-the-middle
280 :     * construction, which is concisely but cryptically performed
281 :     * within the while-condition of a body-less for loop.
282 : dl 1.1 *
283 :     * 4. Otherwise, the range cannot be represented as a positive
284 : dl 1.4 * long. The loop repeatedly generates unbounded longs until
285 :     * obtaining a candidate meeting constraints (with an expected
286 :     * number of iterations of less than two).
287 : dl 1.1 */
288 :    
289 :     long r = mix64(nextSeed());
290 :     if (origin < bound) {
291 :     long n = bound - origin, m = n - 1;
292 : dl 1.7 if ((n & m) == 0L) // power of two
293 : dl 1.1 r = (r & m) + origin;
294 : dl 1.7 else if (n > 0L) { // reject over-represented candidates
295 : dl 1.1 for (long u = r >>> 1; // ensure nonnegative
296 : dl 1.7 u + m - (r = u % n) < 0L; // rejection check
297 : dl 1.1 u = mix64(nextSeed()) >>> 1) // retry
298 :     ;
299 :     r += origin;
300 :     }
301 : dl 1.7 else { // range not representable as long
302 : dl 1.1 while (r < origin || r >= bound)
303 :     r = mix64(nextSeed());
304 :     }
305 :     }
306 :     return r;
307 :     }
308 :    
309 :     /**
310 :     * The form of nextInt used by IntStream Spliterators.
311 :     * Exactly the same as long version, except for types.
312 :     *
313 :     * @param origin the least value, unless greater than bound
314 :     * @param bound the upper bound (exclusive), must not equal origin
315 :     * @return a pseudorandom value
316 :     */
317 :     final int internalNextInt(int origin, int bound) {
318 :     int r = mix32(nextSeed());
319 :     if (origin < bound) {
320 :     int n = bound - origin, m = n - 1;
321 : dl 1.13 if ((n & m) == 0)
322 : dl 1.1 r = (r & m) + origin;
323 :     else if (n > 0) {
324 :     for (int u = r >>> 1;
325 : dl 1.7 u + m - (r = u % n) < 0;
326 : dl 1.1 u = mix32(nextSeed()) >>> 1)
327 :     ;
328 :     r += origin;
329 :     }
330 :     else {
331 :     while (r < origin || r >= bound)
332 :     r = mix32(nextSeed());
333 :     }
334 :     }
335 :     return r;
336 :     }
337 :    
338 :     /**
339 :     * The form of nextDouble used by DoubleStream Spliterators.
340 :     *
341 :     * @param origin the least value, unless greater than bound
342 :     * @param bound the upper bound (exclusive), must not equal origin
343 :     * @return a pseudorandom value
344 :     */
345 :     final double internalNextDouble(double origin, double bound) {
346 : dl 1.24 double r = (nextLong() >>> 11) * DOUBLE_UNIT;
347 : dl 1.1 if (origin < bound) {
348 :     r = r * (bound - origin) + origin;
349 : dl 1.7 if (r >= bound) // correct for rounding
350 : dl 1.1 r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
351 :     }
352 :     return r;
353 :     }
354 :    
355 :     /* ---------------- public methods ---------------- */
356 :    
357 :     /**
358 : dl 1.7 * Creates a new SplittableRandom instance using the specified
359 :     * initial seed. SplittableRandom instances created with the same
360 : dl 1.11 * seed in the same program generate identical sequences of values.
361 : dl 1.1 *
362 :     * @param seed the initial seed
363 :     */
364 :     public SplittableRandom(long seed) {
365 : dl 1.21 this(seed, GOLDEN_GAMMA);
366 : dl 1.1 }
367 :    
368 :     /**
369 :     * Creates a new SplittableRandom instance that is likely to
370 :     * generate sequences of values that are statistically independent
371 :     * of those of any other instances in the current program; and
372 :     * may, and typically does, vary across program invocations.
373 :     */
374 : dl 1.21 public SplittableRandom() { // emulate defaultGen.split()
375 : dl 1.23 long s = defaultGen.getAndAdd(2 * GOLDEN_GAMMA);
376 : dl 1.21 this.seed = mix64(s);
377 :     this.gamma = mixGamma(s + GOLDEN_GAMMA);
378 : dl 1.1 }
379 :    
380 :     /**
381 :     * Constructs and returns a new SplittableRandom instance that
382 :     * shares no mutable state with this instance. However, with very
383 :     * high probability, the set of values collectively generated by
384 :     * the two objects has the same statistical properties as if the
385 :     * same quantity of values were generated by a single thread using
386 :     * a single SplittableRandom object. Either or both of the two
387 :     * objects may be further split using the {@code split()} method,
388 :     * and the same expected statistical properties apply to the
389 :     * entire set of generators constructed by such recursive
390 :     * splitting.
391 :     *
392 :     * @return the new SplittableRandom instance
393 :     */
394 :     public SplittableRandom split() {
395 : dl 1.21 return new SplittableRandom(nextLong(), mixGamma(nextSeed()));
396 : dl 1.1 }
397 :    
398 :     /**
399 :     * Returns a pseudorandom {@code int} value.
400 :     *
401 : dl 1.7 * @return a pseudorandom {@code int} value
402 : dl 1.1 */
403 :     public int nextInt() {
404 :     return mix32(nextSeed());
405 :     }
406 :    
407 :     /**
408 : dl 1.7 * Returns a pseudorandom {@code int} value between zero (inclusive)
409 : dl 1.1 * and the specified bound (exclusive).
410 :     *
411 : dl 1.18 * @param bound the upper bound (exclusive). Must be positive.
412 : dl 1.7 * @return a pseudorandom {@code int} value between zero
413 : jsr166 1.10 * (inclusive) and the bound (exclusive)
414 : dl 1.16 * @throws IllegalArgumentException if {@code bound} is not positive
415 : dl 1.1 */
416 :     public int nextInt(int bound) {
417 :     if (bound <= 0)
418 : jsr166 1.28 throw new IllegalArgumentException(BAD_BOUND);
419 : dl 1.1 // Specialize internalNextInt for origin 0
420 :     int r = mix32(nextSeed());
421 :     int m = bound - 1;
422 : dl 1.13 if ((bound & m) == 0) // power of two
423 : dl 1.1 r &= m;
424 :     else { // reject over-represented candidates
425 :     for (int u = r >>> 1;
426 : dl 1.7 u + m - (r = u % bound) < 0;
427 : dl 1.1 u = mix32(nextSeed()) >>> 1)
428 :     ;
429 :     }
430 :     return r;
431 :     }
432 :    
433 :     /**
434 :     * Returns a pseudorandom {@code int} value between the specified
435 :     * origin (inclusive) and the specified bound (exclusive).
436 :     *
437 :     * @param origin the least value returned
438 :     * @param bound the upper bound (exclusive)
439 :     * @return a pseudorandom {@code int} value between the origin
440 : jsr166 1.10 * (inclusive) and the bound (exclusive)
441 : dl 1.7 * @throws IllegalArgumentException if {@code origin} is greater than
442 : dl 1.1 * or equal to {@code bound}
443 :     */
444 :     public int nextInt(int origin, int bound) {
445 :     if (origin >= bound)
446 : jsr166 1.28 throw new IllegalArgumentException(BAD_RANGE);
447 : dl 1.1 return internalNextInt(origin, bound);
448 :     }
449 :    
450 :     /**
451 :     * Returns a pseudorandom {@code long} value.
452 :     *
453 : dl 1.7 * @return a pseudorandom {@code long} value
454 : dl 1.1 */
455 :     public long nextLong() {
456 :     return mix64(nextSeed());
457 :     }
458 :    
459 :     /**
460 : dl 1.7 * Returns a pseudorandom {@code long} value between zero (inclusive)
461 : dl 1.1 * and the specified bound (exclusive).
462 :     *
463 : dl 1.18 * @param bound the upper bound (exclusive). Must be positive.
464 : dl 1.7 * @return a pseudorandom {@code long} value between zero
465 : jsr166 1.10 * (inclusive) and the bound (exclusive)
466 : dl 1.16 * @throws IllegalArgumentException if {@code bound} is not positive
467 : dl 1.1 */
468 :     public long nextLong(long bound) {
469 :     if (bound <= 0)
470 : jsr166 1.28 throw new IllegalArgumentException(BAD_BOUND);
471 : dl 1.1 // Specialize internalNextLong for origin 0
472 :     long r = mix64(nextSeed());
473 :     long m = bound - 1;
474 :     if ((bound & m) == 0L) // power of two
475 :     r &= m;
476 :     else { // reject over-represented candidates
477 :     for (long u = r >>> 1;
478 :     u + m - (r = u % bound) < 0L;
479 :     u = mix64(nextSeed()) >>> 1)
480 :     ;
481 :     }
482 :     return r;
483 :     }
484 :    
485 :     /**
486 :     * Returns a pseudorandom {@code long} value between the specified
487 :     * origin (inclusive) and the specified bound (exclusive).
488 :     *
489 :     * @param origin the least value returned
490 :     * @param bound the upper bound (exclusive)
491 :     * @return a pseudorandom {@code long} value between the origin
492 : jsr166 1.10 * (inclusive) and the bound (exclusive)
493 : dl 1.7 * @throws IllegalArgumentException if {@code origin} is greater than
494 : dl 1.1 * or equal to {@code bound}
495 :     */
496 :     public long nextLong(long origin, long bound) {
497 :     if (origin >= bound)
498 : jsr166 1.28 throw new IllegalArgumentException(BAD_RANGE);
499 : dl 1.1 return internalNextLong(origin, bound);
500 :     }
501 :    
502 :     /**
503 : dl 1.7 * Returns a pseudorandom {@code double} value between zero
504 :     * (inclusive) and one (exclusive).
505 : dl 1.1 *
506 : dl 1.7 * @return a pseudorandom {@code double} value between zero
507 : dl 1.18 * (inclusive) and one (exclusive)
508 : dl 1.1 */
509 :     public double nextDouble() {
510 : dl 1.24 return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT;
511 : dl 1.1 }
512 :    
513 :     /**
514 :     * Returns a pseudorandom {@code double} value between 0.0
515 :     * (inclusive) and the specified bound (exclusive).
516 :     *
517 : dl 1.18 * @param bound the upper bound (exclusive). Must be positive.
518 : dl 1.7 * @return a pseudorandom {@code double} value between zero
519 : jsr166 1.10 * (inclusive) and the bound (exclusive)
520 : dl 1.16 * @throws IllegalArgumentException if {@code bound} is not positive
521 : dl 1.1 */
522 :     public double nextDouble(double bound) {
523 : dl 1.7 if (!(bound > 0.0))
524 : jsr166 1.28 throw new IllegalArgumentException(BAD_BOUND);
525 : dl 1.24 double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound;
526 : dl 1.1 return (result < bound) ? result : // correct for rounding
527 :     Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
528 :     }
529 :    
530 :     /**
531 : dl 1.7 * Returns a pseudorandom {@code double} value between the specified
532 : dl 1.1 * origin (inclusive) and bound (exclusive).
533 :     *
534 :     * @param origin the least value returned
535 : dl 1.18 * @param bound the upper bound (exclusive)
536 : dl 1.1 * @return a pseudorandom {@code double} value between the origin
537 : jsr166 1.10 * (inclusive) and the bound (exclusive)
538 : dl 1.1 * @throws IllegalArgumentException if {@code origin} is greater than
539 :     * or equal to {@code bound}
540 :     */
541 :     public double nextDouble(double origin, double bound) {
542 : dl 1.7 if (!(origin < bound))
543 : jsr166 1.28 throw new IllegalArgumentException(BAD_RANGE);
544 : dl 1.1 return internalNextDouble(origin, bound);
545 :     }
546 :    
547 : dl 1.11 /**
548 :     * Returns a pseudorandom {@code boolean} value.
549 :     *
550 :     * @return a pseudorandom {@code boolean} value
551 :     */
552 :     public boolean nextBoolean() {
553 :     return mix32(nextSeed()) < 0;
554 :     }
555 :    
556 : dl 1.1 // stream methods, coded in a way intended to better isolate for
557 :     // maintenance purposes the small differences across forms.
558 :    
559 :     /**
560 : dl 1.16 * Returns a stream producing the given {@code streamSize} number
561 :     * of pseudorandom {@code int} values from this generator and/or
562 :     * one split from it.
563 : dl 1.1 *
564 :     * @param streamSize the number of values to generate
565 :     * @return a stream of pseudorandom {@code int} values
566 :     * @throws IllegalArgumentException if {@code streamSize} is
567 : dl 1.7 * less than zero
568 : dl 1.1 */
569 :     public IntStream ints(long streamSize) {
570 :     if (streamSize < 0L)
571 : jsr166 1.28 throw new IllegalArgumentException(BAD_SIZE);
572 : dl 1.1 return StreamSupport.intStream
573 :     (new RandomIntsSpliterator
574 :     (this, 0L, streamSize, Integer.MAX_VALUE, 0),
575 :     false);
576 :     }
577 :    
578 :     /**
579 :     * Returns an effectively unlimited stream of pseudorandom {@code int}
580 : dl 1.16 * values from this generator and/or one split from it.
581 : dl 1.1 *
582 :     * @implNote This method is implemented to be equivalent to {@code
583 :     * ints(Long.MAX_VALUE)}.
584 :     *
585 :     * @return a stream of pseudorandom {@code int} values
586 :     */
587 :     public IntStream ints() {
588 :     return StreamSupport.intStream
589 :     (new RandomIntsSpliterator
590 :     (this, 0L, Long.MAX_VALUE, Integer.MAX_VALUE, 0),
591 :     false);
592 :     }
593 :    
594 :     /**
595 : dl 1.16 * Returns a stream producing the given {@code streamSize} number
596 : dl 1.18 * of pseudorandom {@code int} values from this generator and/or one split
597 :     * from it; each value conforms to the given origin (inclusive) and bound
598 :     * (exclusive).
599 : dl 1.1 *
600 :     * @param streamSize the number of values to generate
601 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
602 :     * @param randomNumberBound the bound (exclusive) of each random value
603 : dl 1.1 * @return a stream of pseudorandom {@code int} values,
604 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
605 : dl 1.1 * @throws IllegalArgumentException if {@code streamSize} is
606 : dl 1.7 * less than zero, or {@code randomNumberOrigin}
607 : dl 1.1 * is greater than or equal to {@code randomNumberBound}
608 :     */
609 :     public IntStream ints(long streamSize, int randomNumberOrigin,
610 :     int randomNumberBound) {
611 :     if (streamSize < 0L)
612 : jsr166 1.28 throw new IllegalArgumentException(BAD_SIZE);
613 : dl 1.1 if (randomNumberOrigin >= randomNumberBound)
614 : jsr166 1.28 throw new IllegalArgumentException(BAD_RANGE);
615 : dl 1.1 return StreamSupport.intStream
616 :     (new RandomIntsSpliterator
617 :     (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
618 :     false);
619 :     }
620 :    
621 :     /**
622 :     * Returns an effectively unlimited stream of pseudorandom {@code
623 : dl 1.18 * int} values from this generator and/or one split from it; each value
624 :     * conforms to the given origin (inclusive) and bound (exclusive).
625 : dl 1.1 *
626 :     * @implNote This method is implemented to be equivalent to {@code
627 :     * ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
628 :     *
629 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
630 :     * @param randomNumberBound the bound (exclusive) of each random value
631 : dl 1.1 * @return a stream of pseudorandom {@code int} values,
632 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
633 : dl 1.1 * @throws IllegalArgumentException if {@code randomNumberOrigin}
634 :     * is greater than or equal to {@code randomNumberBound}
635 :     */
636 :     public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
637 :     if (randomNumberOrigin >= randomNumberBound)
638 : jsr166 1.28 throw new IllegalArgumentException(BAD_RANGE);
639 : dl 1.1 return StreamSupport.intStream
640 :     (new RandomIntsSpliterator
641 :     (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
642 :     false);
643 :     }
644 :    
645 :     /**
646 : dl 1.16 * Returns a stream producing the given {@code streamSize} number
647 :     * of pseudorandom {@code long} values from this generator and/or
648 :     * one split from it.
649 : dl 1.1 *
650 :     * @param streamSize the number of values to generate
651 : dl 1.7 * @return a stream of pseudorandom {@code long} values
652 : dl 1.1 * @throws IllegalArgumentException if {@code streamSize} is
653 : dl 1.7 * less than zero
654 : dl 1.1 */
655 :     public LongStream longs(long streamSize) {
656 :     if (streamSize < 0L)
657 : jsr166 1.28 throw new IllegalArgumentException(BAD_SIZE);
658 : dl 1.1 return StreamSupport.longStream
659 :     (new RandomLongsSpliterator
660 :     (this, 0L, streamSize, Long.MAX_VALUE, 0L),
661 :     false);
662 :     }
663 :    
664 :     /**
665 : dl 1.16 * Returns an effectively unlimited stream of pseudorandom {@code
666 :     * long} values from this generator and/or one split from it.
667 : dl 1.1 *
668 :     * @implNote This method is implemented to be equivalent to {@code
669 :     * longs(Long.MAX_VALUE)}.
670 :     *
671 :     * @return a stream of pseudorandom {@code long} values
672 :     */
673 :     public LongStream longs() {
674 :     return StreamSupport.longStream
675 :     (new RandomLongsSpliterator
676 :     (this, 0L, Long.MAX_VALUE, Long.MAX_VALUE, 0L),
677 :     false);
678 :     }
679 :    
680 :     /**
681 : dl 1.7 * Returns a stream producing the given {@code streamSize} number of
682 : dl 1.18 * pseudorandom {@code long} values from this generator and/or one split
683 :     * from it; each value conforms to the given origin (inclusive) and bound
684 :     * (exclusive).
685 : dl 1.1 *
686 :     * @param streamSize the number of values to generate
687 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
688 :     * @param randomNumberBound the bound (exclusive) of each random value
689 : dl 1.1 * @return a stream of pseudorandom {@code long} values,
690 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
691 : dl 1.1 * @throws IllegalArgumentException if {@code streamSize} is
692 : dl 1.7 * less than zero, or {@code randomNumberOrigin}
693 : dl 1.1 * is greater than or equal to {@code randomNumberBound}
694 :     */
695 :     public LongStream longs(long streamSize, long randomNumberOrigin,
696 :     long randomNumberBound) {
697 :     if (streamSize < 0L)
698 : jsr166 1.28 throw new IllegalArgumentException(BAD_SIZE);
699 : dl 1.1 if (randomNumberOrigin >= randomNumberBound)
700 : jsr166 1.28 throw new IllegalArgumentException(BAD_RANGE);
701 : dl 1.1 return StreamSupport.longStream
702 :     (new RandomLongsSpliterator
703 :     (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
704 :     false);
705 :     }
706 :    
707 :     /**
708 :     * Returns an effectively unlimited stream of pseudorandom {@code
709 : dl 1.18 * long} values from this generator and/or one split from it; each value
710 :     * conforms to the given origin (inclusive) and bound (exclusive).
711 : dl 1.1 *
712 :     * @implNote This method is implemented to be equivalent to {@code
713 :     * longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
714 :     *
715 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
716 :     * @param randomNumberBound the bound (exclusive) of each random value
717 : dl 1.1 * @return a stream of pseudorandom {@code long} values,
718 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
719 : dl 1.1 * @throws IllegalArgumentException if {@code randomNumberOrigin}
720 :     * is greater than or equal to {@code randomNumberBound}
721 :     */
722 :     public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
723 :     if (randomNumberOrigin >= randomNumberBound)
724 : jsr166 1.28 throw new IllegalArgumentException(BAD_RANGE);
725 : dl 1.1 return StreamSupport.longStream
726 :     (new RandomLongsSpliterator
727 :     (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
728 :     false);
729 :     }
730 :    
731 :     /**
732 : dl 1.7 * Returns a stream producing the given {@code streamSize} number of
733 : dl 1.18 * pseudorandom {@code double} values from this generator and/or one split
734 :     * from it; each value is between zero (inclusive) and one (exclusive).
735 : dl 1.1 *
736 :     * @param streamSize the number of values to generate
737 :     * @return a stream of {@code double} values
738 :     * @throws IllegalArgumentException if {@code streamSize} is
739 : dl 1.7 * less than zero
740 : dl 1.1 */
741 :     public DoubleStream doubles(long streamSize) {
742 :     if (streamSize < 0L)
743 : jsr166 1.28 throw new IllegalArgumentException(BAD_SIZE);
744 : dl 1.1 return StreamSupport.doubleStream
745 :     (new RandomDoublesSpliterator
746 :     (this, 0L, streamSize, Double.MAX_VALUE, 0.0),
747 :     false);
748 :     }
749 :    
750 :     /**
751 :     * Returns an effectively unlimited stream of pseudorandom {@code
752 : dl 1.18 * double} values from this generator and/or one split from it; each value
753 :     * is between zero (inclusive) and one (exclusive).
754 : dl 1.1 *
755 :     * @implNote This method is implemented to be equivalent to {@code
756 :     * doubles(Long.MAX_VALUE)}.
757 :     *
758 :     * @return a stream of pseudorandom {@code double} values
759 :     */
760 :     public DoubleStream doubles() {
761 :     return StreamSupport.doubleStream
762 :     (new RandomDoublesSpliterator
763 :     (this, 0L, Long.MAX_VALUE, Double.MAX_VALUE, 0.0),
764 :     false);
765 :     }
766 :    
767 :     /**
768 : dl 1.7 * Returns a stream producing the given {@code streamSize} number of
769 : dl 1.18 * pseudorandom {@code double} values from this generator and/or one split
770 :     * from it; each value conforms to the given origin (inclusive) and bound
771 :     * (exclusive).
772 : dl 1.1 *
773 :     * @param streamSize the number of values to generate
774 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
775 :     * @param randomNumberBound the bound (exclusive) of each random value
776 : dl 1.1 * @return a stream of pseudorandom {@code double} values,
777 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
778 : dl 1.1 * @throws IllegalArgumentException if {@code streamSize} is
779 : dl 1.18 * less than zero
780 : dl 1.1 * @throws IllegalArgumentException if {@code randomNumberOrigin}
781 :     * is greater than or equal to {@code randomNumberBound}
782 :     */
783 :     public DoubleStream doubles(long streamSize, double randomNumberOrigin,
784 :     double randomNumberBound) {
785 :     if (streamSize < 0L)
786 : jsr166 1.28 throw new IllegalArgumentException(BAD_SIZE);
787 : dl 1.7 if (!(randomNumberOrigin < randomNumberBound))
788 : jsr166 1.28 throw new IllegalArgumentException(BAD_RANGE);
789 : dl 1.1 return StreamSupport.doubleStream
790 :     (new RandomDoublesSpliterator
791 :     (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
792 :     false);
793 :     }
794 :    
795 :     /**
796 :     * Returns an effectively unlimited stream of pseudorandom {@code
797 : dl 1.18 * double} values from this generator and/or one split from it; each value
798 :     * conforms to the given origin (inclusive) and bound (exclusive).
799 : dl 1.1 *
800 :     * @implNote This method is implemented to be equivalent to {@code
801 :     * doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}.
802 :     *
803 : dl 1.18 * @param randomNumberOrigin the origin (inclusive) of each random value
804 :     * @param randomNumberBound the bound (exclusive) of each random value
805 : dl 1.1 * @return a stream of pseudorandom {@code double} values,
806 : dl 1.18 * each with the given origin (inclusive) and bound (exclusive)
807 : dl 1.1 * @throws IllegalArgumentException if {@code randomNumberOrigin}
808 :     * is greater than or equal to {@code randomNumberBound}
809 :     */
810 :     public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
811 : dl 1.7 if (!(randomNumberOrigin < randomNumberBound))
812 : jsr166 1.28 throw new IllegalArgumentException(BAD_RANGE);
813 : dl 1.1 return StreamSupport.doubleStream
814 :     (new RandomDoublesSpliterator
815 :     (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
816 :     false);
817 :     }
818 :    
819 :     /**
820 :     * Spliterator for int streams. We multiplex the four int
821 : dl 1.7 * versions into one class by treating a bound less than origin as
822 : dl 1.1 * unbounded, and also by treating "infinite" as equivalent to
823 :     * Long.MAX_VALUE. For splits, it uses the standard divide-by-two
824 :     * approach. The long and double versions of this class are
825 :     * identical except for types.
826 :     */
827 : jsr166 1.29 private static final class RandomIntsSpliterator
828 :     implements Spliterator.OfInt {
829 : dl 1.1 final SplittableRandom rng;
830 :     long index;
831 :     final long fence;
832 :     final int origin;
833 :     final int bound;
834 :     RandomIntsSpliterator(SplittableRandom rng, long index, long fence,
835 :     int origin, int bound) {
836 :     this.rng = rng; this.index = index; this.fence = fence;
837 :     this.origin = origin; this.bound = bound;
838 :     }
839 :    
840 :     public RandomIntsSpliterator trySplit() {
841 :     long i = index, m = (i + fence) >>> 1;
842 :     return (m <= i) ? null :
843 :     new RandomIntsSpliterator(rng.split(), i, index = m, origin, bound);
844 :     }
845 :    
846 :     public long estimateSize() {
847 :     return fence - index;
848 :     }
849 :    
850 :     public int characteristics() {
851 :     return (Spliterator.SIZED | Spliterator.SUBSIZED |
852 : dl 1.4 Spliterator.NONNULL | Spliterator.IMMUTABLE);
853 : dl 1.1 }
854 :    
855 :     public boolean tryAdvance(IntConsumer consumer) {
856 :     if (consumer == null) throw new NullPointerException();
857 :     long i = index, f = fence;
858 :     if (i < f) {
859 :     consumer.accept(rng.internalNextInt(origin, bound));
860 :     index = i + 1;
861 :     return true;
862 :     }
863 :     return false;
864 :     }
865 :    
866 :     public void forEachRemaining(IntConsumer consumer) {
867 :     if (consumer == null) throw new NullPointerException();
868 :     long i = index, f = fence;
869 :     if (i < f) {
870 :     index = f;
871 : dl 1.15 SplittableRandom r = rng;
872 : dl 1.1 int o = origin, b = bound;
873 :     do {
874 : dl 1.15 consumer.accept(r.internalNextInt(o, b));
875 : dl 1.1 } while (++i < f);
876 :     }
877 :     }
878 :     }
879 :    
880 :     /**
881 :     * Spliterator for long streams.
882 :     */
883 : jsr166 1.29 private static final class RandomLongsSpliterator
884 :     implements Spliterator.OfLong {
885 : dl 1.1 final SplittableRandom rng;
886 :     long index;
887 :     final long fence;
888 :     final long origin;
889 :     final long bound;
890 :     RandomLongsSpliterator(SplittableRandom rng, long index, long fence,
891 :     long origin, long bound) {
892 :     this.rng = rng; this.index = index; this.fence = fence;
893 :     this.origin = origin; this.bound = bound;
894 :     }
895 :    
896 :     public RandomLongsSpliterator trySplit() {
897 :     long i = index, m = (i + fence) >>> 1;
898 :     return (m <= i) ? null :
899 :     new RandomLongsSpliterator(rng.split(), i, index = m, origin, bound);
900 :     }
901 :    
902 :     public long estimateSize() {
903 :     return fence - index;
904 :     }
905 :    
906 :     public int characteristics() {
907 :     return (Spliterator.SIZED | Spliterator.SUBSIZED |
908 : dl 1.4 Spliterator.NONNULL | Spliterator.IMMUTABLE);
909 : dl 1.1 }
910 :    
911 :     public boolean tryAdvance(LongConsumer consumer) {
912 :     if (consumer == null) throw new NullPointerException();
913 :     long i = index, f = fence;
914 :     if (i < f) {
915 :     consumer.accept(rng.internalNextLong(origin, bound));
916 :     index = i + 1;
917 :     return true;
918 :     }
919 :     return false;
920 :     }
921 :    
922 :     public void forEachRemaining(LongConsumer consumer) {
923 :     if (consumer == null) throw new NullPointerException();
924 :     long i = index, f = fence;
925 :     if (i < f) {
926 :     index = f;
927 : dl 1.15 SplittableRandom r = rng;
928 : dl 1.1 long o = origin, b = bound;
929 :     do {
930 : dl 1.15 consumer.accept(r.internalNextLong(o, b));
931 : dl 1.1 } while (++i < f);
932 :     }
933 :     }
934 :    
935 :     }
936 :    
937 :     /**
938 :     * Spliterator for double streams.
939 :     */
940 : jsr166 1.29 private static final class RandomDoublesSpliterator
941 :     implements Spliterator.OfDouble {
942 : dl 1.1 final SplittableRandom rng;
943 :     long index;
944 :     final long fence;
945 :     final double origin;
946 :     final double bound;
947 :     RandomDoublesSpliterator(SplittableRandom rng, long index, long fence,
948 :     double origin, double bound) {
949 :     this.rng = rng; this.index = index; this.fence = fence;
950 :     this.origin = origin; this.bound = bound;
951 :     }
952 :    
953 :     public RandomDoublesSpliterator trySplit() {
954 :     long i = index, m = (i + fence) >>> 1;
955 :     return (m <= i) ? null :
956 :     new RandomDoublesSpliterator(rng.split(), i, index = m, origin, bound);
957 :     }
958 :    
959 :     public long estimateSize() {
960 :     return fence - index;
961 :     }
962 :    
963 :     public int characteristics() {
964 :     return (Spliterator.SIZED | Spliterator.SUBSIZED |
965 : dl 1.4 Spliterator.NONNULL | Spliterator.IMMUTABLE);
966 : dl 1.1 }
967 :    
968 :     public boolean tryAdvance(DoubleConsumer consumer) {
969 :     if (consumer == null) throw new NullPointerException();
970 :     long i = index, f = fence;
971 :     if (i < f) {
972 :     consumer.accept(rng.internalNextDouble(origin, bound));
973 :     index = i + 1;
974 :     return true;
975 :     }
976 :     return false;
977 :     }
978 :    
979 :     public void forEachRemaining(DoubleConsumer consumer) {
980 :     if (consumer == null) throw new NullPointerException();
981 :     long i = index, f = fence;
982 :     if (i < f) {
983 :     index = f;
984 : dl 1.15 SplittableRandom r = rng;
985 : dl 1.1 double o = origin, b = bound;
986 :     do {
987 : dl 1.15 consumer.accept(r.internalNextDouble(o, b));
988 : dl 1.1 } while (++i < f);
989 :     }
990 :     }
991 :     }
992 :    
993 :     }

Doug Lea
ViewVC Help
Powered by ViewVC 1.0.8