|
1 /* |
|
2 * Copyright (c) 2013, 2019, 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.random; |
|
27 |
|
28 import java.util.function.Consumer; |
|
29 import java.util.function.DoubleConsumer; |
|
30 import java.util.function.IntConsumer; |
|
31 import java.util.function.LongConsumer; |
|
32 import java.util.random.RandomGenerator.SplittableGenerator; |
|
33 import java.util.Spliterator; |
|
34 import java.util.stream.DoubleStream; |
|
35 import java.util.stream.IntStream; |
|
36 import java.util.stream.LongStream; |
|
37 import java.util.stream.Stream; |
|
38 import java.util.stream.StreamSupport; |
|
39 |
|
40 /** |
|
41 * Low-level utility methods helpful for implementing pseudorandom number generators. |
|
42 * |
|
43 * This class is mostly for library writers creating specific implementations of the |
|
44 * interface {@link RandomGenerator}. |
|
45 * |
|
46 * @since 14 |
|
47 */ |
|
48 public class RandomSupport { |
|
49 |
|
50 /* |
|
51 * Implementation Overview. |
|
52 * |
|
53 * This class provides utility methods and constants frequently |
|
54 * useful in the implementation of pseudorandom number generators |
|
55 * that satisfy the interface {@link RandomGenerator}. |
|
56 * |
|
57 * File organization: First some message strings, then the main |
|
58 * public methods, followed by a non-public base spliterator class. |
|
59 */ |
|
60 |
|
61 // IllegalArgumentException messages |
|
62 static final String BAD_SIZE = "size must be non-negative"; |
|
63 static final String BAD_DISTANCE = "jump distance must be finite, positive, and an exact integer"; |
|
64 static final String BAD_BOUND = "bound must be positive"; |
|
65 static final String BAD_FLOATING_BOUND = "bound must be finite and positive"; |
|
66 static final String BAD_RANGE = "bound must be greater than origin"; |
|
67 |
|
68 /* ---------------- public methods ---------------- */ |
|
69 |
|
70 /** |
|
71 * Check a {@code long} proposed stream size for validity. |
|
72 * |
|
73 * @param streamSize the proposed stream size |
|
74 * |
|
75 * @throws IllegalArgumentException if {@code streamSize} is negative |
|
76 */ |
|
77 public static void checkStreamSize(long streamSize) { |
|
78 if (streamSize < 0L) |
|
79 throw new IllegalArgumentException(BAD_SIZE); |
|
80 } |
|
81 |
|
82 /** |
|
83 * Check a {@code double} proposed jump distance for validity. |
|
84 * |
|
85 * @param distance the proposed jump distance |
|
86 * |
|
87 * @throws IllegalArgumentException if {@code size} fails to be positive, finite, and an exact integer |
|
88 */ |
|
89 public static void checkJumpDistance(double distance) { |
|
90 if (!(distance > 0.0 && distance < Float.POSITIVE_INFINITY |
|
91 && distance == Math.floor(distance))) { |
|
92 throw new IllegalArgumentException(BAD_DISTANCE); |
|
93 } |
|
94 } |
|
95 |
|
96 /** |
|
97 * Checks a {@code float} upper bound value for validity. |
|
98 * |
|
99 * @param bound the upper bound (exclusive) |
|
100 * |
|
101 * @throws IllegalArgumentException if {@code bound} fails to be positive and finite |
|
102 */ |
|
103 public static void checkBound(float bound) { |
|
104 if (!(bound > 0.0 && bound < Float.POSITIVE_INFINITY)) { |
|
105 throw new IllegalArgumentException(BAD_FLOATING_BOUND); |
|
106 } |
|
107 } |
|
108 |
|
109 /** |
|
110 * Checks a {@code double} upper bound value for validity. |
|
111 * |
|
112 * @param bound the upper bound (exclusive) |
|
113 * |
|
114 * @throws IllegalArgumentException if {@code bound} fails to be positive and finite |
|
115 */ |
|
116 public static void checkBound(double bound) { |
|
117 if (!(bound > 0.0 && bound < Double.POSITIVE_INFINITY)) { |
|
118 throw new IllegalArgumentException(BAD_FLOATING_BOUND); |
|
119 } |
|
120 } |
|
121 |
|
122 /** |
|
123 * Checks an {@code int} upper bound value for validity. |
|
124 * |
|
125 * @param bound the upper bound (exclusive) |
|
126 * |
|
127 * @throws IllegalArgumentException if {@code bound} is not positive |
|
128 */ |
|
129 public static void checkBound(int bound) { |
|
130 if (bound <= 0) { |
|
131 throw new IllegalArgumentException(BAD_BOUND); |
|
132 } |
|
133 } |
|
134 |
|
135 /** |
|
136 * Checks a {@code long} upper bound value for validity. |
|
137 * |
|
138 * @param bound the upper bound (exclusive) |
|
139 * |
|
140 * @throws IllegalArgumentException if {@code bound} is not positive |
|
141 */ |
|
142 public static void checkBound(long bound) { |
|
143 if (bound <= 0) { |
|
144 throw new IllegalArgumentException(BAD_BOUND); |
|
145 } |
|
146 } |
|
147 |
|
148 /** |
|
149 * Checks a {@code float} range for validity. |
|
150 * |
|
151 * @param origin the least value (inclusive) in the range |
|
152 * @param bound the upper bound (exclusive) of the range |
|
153 * |
|
154 * @throws IllegalArgumentException if {@code origin} is not finite, {@code bound} is not finite, |
|
155 * or {@code bound - origin} is not finite |
|
156 */ |
|
157 public static void checkRange(float origin, float bound) { |
|
158 if (!(origin < bound && (bound - origin) < Float.POSITIVE_INFINITY)) { |
|
159 throw new IllegalArgumentException(BAD_RANGE); |
|
160 } |
|
161 } |
|
162 |
|
163 /** |
|
164 * Checks a {@code double} range for validity. |
|
165 * |
|
166 * @param origin the least value (inclusive) in the range |
|
167 * @param bound the upper bound (exclusive) of the range |
|
168 * |
|
169 * @throws IllegalArgumentException if {@code origin} is not finite, {@code bound} is not finite, |
|
170 * or {@code bound - origin} is not finite |
|
171 */ |
|
172 public static void checkRange(double origin, double bound) { |
|
173 if (!(origin < bound && (bound - origin) < Double.POSITIVE_INFINITY)) { |
|
174 throw new IllegalArgumentException(BAD_RANGE); |
|
175 } |
|
176 } |
|
177 |
|
178 /** |
|
179 * Checks an {@code int} range for validity. |
|
180 * |
|
181 * @param origin the least value that can be returned |
|
182 * @param bound the upper bound (exclusive) for the returned value |
|
183 * |
|
184 * @throws IllegalArgumentException if {@code origin} is greater than or equal to {@code bound} |
|
185 */ |
|
186 public static void checkRange(int origin, int bound) { |
|
187 if (origin >= bound) { |
|
188 throw new IllegalArgumentException(BAD_RANGE); |
|
189 } |
|
190 } |
|
191 |
|
192 /** |
|
193 * Checks a {@code long} range for validity. |
|
194 * |
|
195 * @param origin the least value that can be returned |
|
196 * @param bound the upper bound (exclusive) for the returned value |
|
197 * |
|
198 * @throws IllegalArgumentException if {@code origin} is greater than or equal to {@code bound} |
|
199 */ |
|
200 public static void checkRange(long origin, long bound) { |
|
201 if (origin >= bound) { |
|
202 throw new IllegalArgumentException(BAD_RANGE); |
|
203 } |
|
204 } |
|
205 |
|
206 /** |
|
207 * Given an array of seed bytes of any length, construct an array |
|
208 * of {@code long} seed values of length {@code n}, such that the |
|
209 * last {@code z} values are not all zero. |
|
210 * |
|
211 * @param seed an array of {@code byte} values |
|
212 * @param n the length of the result array (should be nonnegative) |
|
213 * @param z the number of trailing result elements that are required |
|
214 * to be not all zero (should be nonnegative but not larger |
|
215 * than {@code n}) |
|
216 * |
|
217 * @return an array of length {@code n} containing {@code long} seed values |
|
218 */ |
|
219 public static long[] convertSeedBytesToLongs(byte[] seed, int n, int z) { |
|
220 final long[] result = new long[n]; |
|
221 final int m = Math.min(seed.length, n << 3); |
|
222 // Distribute seed bytes into the words to be formed. |
|
223 for (int j = 0; j < m; j++) { |
|
224 result[j>>3] = (result[j>>3] << 8) | seed[j]; |
|
225 } |
|
226 // If there aren't enough seed bytes for all the words we need, |
|
227 // use a SplitMix-style PRNG to fill in the rest. |
|
228 long v = result[0]; |
|
229 for (int j = (m + 7) >> 3; j < n; j++) { |
|
230 result[j] = mixMurmur64(v += SILVER_RATIO_64); |
|
231 } |
|
232 // Finally, we need to make sure the last z words are not all zero. |
|
233 search: { |
|
234 for (int j = n - z; j < n; j++) { |
|
235 if (result[j] != 0) break search; |
|
236 } |
|
237 // If they are, fill in using a SplitMix-style PRNG. |
|
238 // Using "& ~1L" in the next line defends against the case z==1 |
|
239 // by guaranteeing that the first generated value will be nonzero. |
|
240 long w = result[0] & ~1L; |
|
241 for (int j = n - z; j < n; j++) { |
|
242 result[j] = mixMurmur64(w += SILVER_RATIO_64); |
|
243 } |
|
244 } |
|
245 return result; |
|
246 } |
|
247 |
|
248 /** |
|
249 * Given an array of seed bytes of any length, construct an array |
|
250 * of {@code int} seed values of length {@code n}, such that the |
|
251 * last {@code z} values are not all zero. |
|
252 * |
|
253 * @param seed an array of {@code byte} values |
|
254 * @param n the length of the result array (should be nonnegative) |
|
255 * @param z the number of trailing result elements that are required |
|
256 * to be not all zero (should be nonnegative but not larger |
|
257 * than {@code n}) |
|
258 * |
|
259 * @return an array of length {@code n} containing {@code int} seed values |
|
260 */ |
|
261 public static int[] convertSeedBytesToInts(byte[] seed, int n, int z) { |
|
262 final int[] result = new int[n]; |
|
263 final int m = Math.min(seed.length, n << 2); |
|
264 // Distribute seed bytes into the words to be formed. |
|
265 for (int j = 0; j < m; j++) { |
|
266 result[j>>2] = (result[j>>2] << 8) | seed[j]; |
|
267 } |
|
268 // If there aren't enough seed bytes for all the words we need, |
|
269 // use a SplitMix-style PRNG to fill in the rest. |
|
270 int v = result[0]; |
|
271 for (int j = (m + 3) >> 2; j < n; j++) { |
|
272 result[j] = mixMurmur32(v += SILVER_RATIO_32); |
|
273 } |
|
274 // Finally, we need to make sure the last z words are not all zero. |
|
275 search: { |
|
276 for (int j = n - z; j < n; j++) { |
|
277 if (result[j] != 0) break search; |
|
278 } |
|
279 // If they are, fill in using a SplitMix-style PRNG. |
|
280 // Using "& ~1" in the next line defends against the case z==1 |
|
281 // by guaranteeing that the first generated value will be nonzero. |
|
282 int w = result[0] & ~1; |
|
283 for (int j = n - z; j < n; j++) { |
|
284 result[j] = mixMurmur32(w += SILVER_RATIO_32); |
|
285 } |
|
286 } |
|
287 return result; |
|
288 } |
|
289 |
|
290 /* |
|
291 * Bounded versions of nextX methods used by streams, as well as |
|
292 * the public nextX(origin, bound) methods. These exist mainly to |
|
293 * avoid the need for multiple versions of stream spliterators |
|
294 * across the different exported forms of streams. |
|
295 */ |
|
296 |
|
297 /** |
|
298 * This is the form of {@code nextLong} used by a {@link LongStream} |
|
299 * {@link Spliterator} and by the public method |
|
300 * {@code nextLong(origin, bound)}. If {@code origin} is greater |
|
301 * than {@code bound}, then this method simply calls the unbounded |
|
302 * version of {@code nextLong()}, choosing pseudorandomly from |
|
303 * among all 2<sup>64</sup> possible {@code long} values}, and |
|
304 * otherwise uses one or more calls to {@code nextLong()} to |
|
305 * choose a value pseudorandomly from the possible values |
|
306 * between {@code origin} (inclusive) and {@code bound} (exclusive). |
|
307 * |
|
308 * @implNote This method first calls {@code nextLong()} to obtain |
|
309 * a {@code long} value that is assumed to be pseudorandomly |
|
310 * chosen uniformly and independently from the 2<sup>64</sup> |
|
311 * possible {@code long} values (that is, each of the 2<sup>64</sup> |
|
312 * possible long values is equally likely to be chosen). |
|
313 * Under some circumstances (when the specified range is not |
|
314 * a power of 2), {@code nextLong()} may be called additional times |
|
315 * to ensure that that the values in the specified range are |
|
316 * equally likely to be chosen (provided the assumption holds). |
|
317 * <p> |
|
318 * The implementation considers four cases: |
|
319 * <ol> |
|
320 * |
|
321 * <li> If the {@code} bound} is less than or equal to the {@code origin} |
|
322 * (indicated an unbounded form), the 64-bit {@code long} value |
|
323 * obtained from {@code nextLong()} is returned directly. |
|
324 * |
|
325 * <li> Otherwise, if the length <i>n</i> of the specified range is an |
|
326 * exact power of two 2<sup><i>m</i></sup> for some integer |
|
327 * <i>m</i>, then return the sum of {@code origin} and the |
|
328 * <i>m</i> lowest-order bits of the value from {@code nextLong()}. |
|
329 * |
|
330 * <li> Otherwise, if the length <i>n</i> of the specified range |
|
331 * is less than 2<sup>63</sup>, then the basic idea is to use the |
|
332 * remainder modulo <i>n</i> of the value from {@code nextLong()}, |
|
333 * but with this approach some values will be over-represented. |
|
334 * Therefore a loop is used to avoid potential bias by rejecting |
|
335 * candidates that are too large. Assuming that the results from |
|
336 * {@code nextLong()} are truly chosen uniformly and independently, |
|
337 * the expected number of iterations will be somewhere between |
|
338 * 1 and 2, depending on the precise value of <i>n</i>. |
|
339 * |
|
340 * <li> Otherwise, the length <i>n</i> of the specified range |
|
341 * cannot be represented as a positive {@code long} value. |
|
342 * A loop repeatedly calls {@code nextlong()} until obtaining |
|
343 * a suitable candidate, Again, the expected number of iterations |
|
344 * is less than 2. |
|
345 * |
|
346 * </ol> |
|
347 * |
|
348 * @param rng a random number generator to be used as a |
|
349 * source of pseudorandom {@code long} values |
|
350 * @param origin the least value that can be produced, |
|
351 * unless greater than or equal to {@code bound} |
|
352 * @param bound the upper bound (exclusive), unless {@code origin} |
|
353 * is greater than or equal to {@code bound} |
|
354 * |
|
355 * @return a pseudorandomly chosen {@code long} value, |
|
356 * which will be between {@code origin} (inclusive) and |
|
357 * {@code bound} exclusive unless {@code origin} |
|
358 * is greater than or equal to {@code bound} |
|
359 */ |
|
360 public static long boundedNextLong(RandomGenerator rng, long origin, long bound) { |
|
361 long r = rng.nextLong(); |
|
362 if (origin < bound) { |
|
363 // It's not case (1). |
|
364 final long n = bound - origin; |
|
365 final long m = n - 1; |
|
366 if ((n & m) == 0L) { |
|
367 // It is case (2): length of range is a power of 2. |
|
368 r = (r & m) + origin; |
|
369 } else if (n > 0L) { |
|
370 // It is case (3): need to reject over-represented candidates. |
|
371 /* This loop takes an unlovable form (but it works): |
|
372 because the first candidate is already available, |
|
373 we need a break-in-the-middle construction, |
|
374 which is concisely but cryptically performed |
|
375 within the while-condition of a body-less for loop. */ |
|
376 for (long u = r >>> 1; // ensure nonnegative |
|
377 u + m - (r = u % n) < 0L; // rejection check |
|
378 u = rng.nextLong() >>> 1) // retry |
|
379 ; |
|
380 r += origin; |
|
381 } |
|
382 else { |
|
383 // It is case (4): length of range not representable as long. |
|
384 while (r < origin || r >= bound) |
|
385 r = rng.nextLong(); |
|
386 } |
|
387 } |
|
388 return r; |
|
389 } |
|
390 |
|
391 /** |
|
392 * This is the form of {@code nextLong} used by the public method |
|
393 * {@code nextLong(bound)}. This is essentially a version of |
|
394 * {@code boundedNextLong(origin, bound)} that has been |
|
395 * specialized for the case where the {@code origin} is zero |
|
396 * and the {@code bound} is greater than zero. The value |
|
397 * returned is chosen pseudorandomly from nonnegative integer |
|
398 * values less than {@code bound}. |
|
399 * |
|
400 * @implNote This method first calls {@code nextLong()} to obtain |
|
401 * a {@code long} value that is assumed to be pseudorandomly |
|
402 * chosen uniformly and independently from the 2<sup>64</sup> |
|
403 * possible {@code long} values (that is, each of the 2<sup>64</sup> |
|
404 * possible long values is equally likely to be chosen). |
|
405 * Under some circumstances (when the specified range is not |
|
406 * a power of 2), {@code nextLong()} may be called additional times |
|
407 * to ensure that that the values in the specified range are |
|
408 * equally likely to be chosen (provided the assumption holds). |
|
409 * <p> |
|
410 * The implementation considers two cases: |
|
411 * <ol> |
|
412 * |
|
413 * <li> If {@code bound} is an exact power of two 2<sup><i>m</i></sup> |
|
414 * for some integer <i>m</i>, then return the sum of {@code origin} |
|
415 * and the <i>m</i> lowest-order bits of the value from |
|
416 * {@code nextLong()}. |
|
417 * |
|
418 * <li> Otherwise, the basic idea is to use the remainder modulo |
|
419 * <i>bound</i> of the value from {@code nextLong()}, |
|
420 * but with this approach some values will be over-represented. |
|
421 * Therefore a loop is used to avoid potential bias by rejecting |
|
422 * candidates that vare too large. Assuming that the results from |
|
423 * {@code nextLong()} are truly chosen uniformly and independently, |
|
424 * the expected number of iterations will be somewhere between |
|
425 * 1 and 2, depending on the precise value of <i>bound</i>. |
|
426 * |
|
427 * </ol> |
|
428 * |
|
429 * @param rng a random number generator to be used as a |
|
430 * source of pseudorandom {@code long} values |
|
431 * @param bound the upper bound (exclusive); must be greater than zero |
|
432 * |
|
433 * @return a pseudorandomly chosen {@code long} value |
|
434 */ |
|
435 public static long boundedNextLong(RandomGenerator rng, long bound) { |
|
436 // Specialize boundedNextLong for origin == 0, bound > 0 |
|
437 final long m = bound - 1; |
|
438 long r = rng.nextLong(); |
|
439 if ((bound & m) == 0L) { |
|
440 // The bound is a power of 2. |
|
441 r &= m; |
|
442 } else { |
|
443 // Must reject over-represented candidates |
|
444 /* This loop takes an unlovable form (but it works): |
|
445 because the first candidate is already available, |
|
446 we need a break-in-the-middle construction, |
|
447 which is concisely but cryptically performed |
|
448 within the while-condition of a body-less for loop. */ |
|
449 for (long u = r >>> 1; |
|
450 u + m - (r = u % bound) < 0L; |
|
451 u = rng.nextLong() >>> 1) |
|
452 ; |
|
453 } |
|
454 return r; |
|
455 } |
|
456 |
|
457 /** |
|
458 * This is the form of {@code nextInt} used by an {@link IntStream} |
|
459 * {@link Spliterator} and by the public method |
|
460 * {@code nextInt(origin, bound)}. If {@code origin} is greater |
|
461 * than {@code bound}, then this method simply calls the unbounded |
|
462 * version of {@code nextInt()}, choosing pseudorandomly from |
|
463 * among all 2<sup>64</sup> possible {@code int} values}, and |
|
464 * otherwise uses one or more calls to {@code nextInt()} to |
|
465 * choose a value pseudorandomly from the possible values |
|
466 * between {@code origin} (inclusive) and {@code bound} (exclusive). |
|
467 * |
|
468 * @param rng a random number generator to be used as a |
|
469 * source of pseudorandom {@code int} values |
|
470 * @param origin the least value that can be produced, |
|
471 * unless greater than or equal to {@code bound} |
|
472 * @param bound the upper bound (exclusive), unless {@code origin} |
|
473 * is greater than or equal to {@code bound} |
|
474 * |
|
475 * @return a pseudorandomly chosen {@code int} value, |
|
476 * which will be between {@code origin} (inclusive) and |
|
477 * {@code bound} exclusive unless {@code origin} |
|
478 * is greater than or equal to {@code bound} |
|
479 * |
|
480 * @implNote The implementation of this method is identical to |
|
481 * the implementation of {@code nextLong(origin, bound)} |
|
482 * except that {@code int} values and the {@code nextInt()} |
|
483 * method are used rather than {@code long} values and the |
|
484 * {@code nextLong()} method. |
|
485 */ |
|
486 public static int boundedNextInt(RandomGenerator rng, int origin, int bound) { |
|
487 int r = rng.nextInt(); |
|
488 if (origin < bound) { |
|
489 // It's not case (1). |
|
490 final int n = bound - origin; |
|
491 final int m = n - 1; |
|
492 if ((n & m) == 0) { |
|
493 // It is case (2): length of range is a power of 2. |
|
494 r = (r & m) + origin; |
|
495 } else if (n > 0) { |
|
496 // It is case (3): need to reject over-represented candidates. |
|
497 for (int u = r >>> 1; |
|
498 u + m - (r = u % n) < 0; |
|
499 u = rng.nextInt() >>> 1) |
|
500 ; |
|
501 r += origin; |
|
502 } |
|
503 else { |
|
504 // It is case (4): length of range not representable as long. |
|
505 while (r < origin || r >= bound) { |
|
506 r = rng.nextInt(); |
|
507 } |
|
508 } |
|
509 } |
|
510 return r; |
|
511 } |
|
512 |
|
513 /** |
|
514 * This is the form of {@code nextInt} used by the public method |
|
515 * {@code nextInt(bound)}. This is essentially a version of |
|
516 * {@code boundedNextInt(origin, bound)} that has been |
|
517 * specialized for the case where the {@code origin} is zero |
|
518 * and the {@code bound} is greater than zero. The value |
|
519 * returned is chosen pseudorandomly from nonnegative integer |
|
520 * values less than {@code bound}. |
|
521 * |
|
522 * @param rng a random number generator to be used as a |
|
523 * source of pseudorandom {@code long} values |
|
524 * @param bound the upper bound (exclusive); must be greater than zero |
|
525 * |
|
526 * @return a pseudorandomly chosen {@code long} value |
|
527 * |
|
528 * @implNote The implementation of this method is identical to |
|
529 * the implementation of {@code nextLong(bound)} |
|
530 * except that {@code int} values and the {@code nextInt()} |
|
531 * method are used rather than {@code long} values and the |
|
532 * {@code nextLong()} method. |
|
533 */ |
|
534 public static int boundedNextInt(RandomGenerator rng, int bound) { |
|
535 // Specialize boundedNextInt for origin == 0, bound > 0 |
|
536 final int m = bound - 1; |
|
537 int r = rng.nextInt(); |
|
538 if ((bound & m) == 0) { |
|
539 // The bound is a power of 2. |
|
540 r &= m; |
|
541 } else { |
|
542 // Must reject over-represented candidates |
|
543 for (int u = r >>> 1; |
|
544 u + m - (r = u % bound) < 0; |
|
545 u = rng.nextInt() >>> 1) |
|
546 ; |
|
547 } |
|
548 return r; |
|
549 } |
|
550 |
|
551 /** |
|
552 * This is the form of {@code nextDouble} used by a {@link DoubleStream} |
|
553 * {@link Spliterator} and by the public method |
|
554 * {@code nextDouble(origin, bound)}. If {@code origin} is greater |
|
555 * than {@code bound}, then this method simply calls the unbounded |
|
556 * version of {@code nextDouble()}, and otherwise scales and translates |
|
557 * the result of a call to {@code nextDouble()} so that it lies |
|
558 * between {@code origin} (inclusive) and {@code bound} (exclusive). |
|
559 * |
|
560 * @implNote The implementation considers two cases: |
|
561 * <ol> |
|
562 * |
|
563 * <li> If the {@code bound} is less than or equal to the {@code origin} |
|
564 * (indicated an unbounded form), the 64-bit {@code double} value |
|
565 * obtained from {@code nextDouble()} is returned directly. |
|
566 * |
|
567 * <li> Otherwise, the result of a call to {@code nextDouble} is |
|
568 * multiplied by {@code (bound - origin)}, then {@code origin} |
|
569 * is added, and then if this this result is not less than |
|
570 * {@code bound} (which can sometimes occur because of rounding), |
|
571 * it is replaced with the largest {@code double} value that |
|
572 * is less than {@code bound}. |
|
573 * |
|
574 * </ol> |
|
575 * |
|
576 * @param rng a random number generator to be used as a |
|
577 * source of pseudorandom {@code double} values |
|
578 * @param origin the least value that can be produced, |
|
579 * unless greater than or equal to {@code bound}; must be finite |
|
580 * @param bound the upper bound (exclusive), unless {@code origin} |
|
581 * is greater than or equal to {@code bound}; must be finite |
|
582 * @return a pseudorandomly chosen {@code double} value, |
|
583 * which will be between {@code origin} (inclusive) and |
|
584 * {@code bound} exclusive unless {@code origin} |
|
585 * is greater than or equal to {@code bound}, |
|
586 * in which case it will be between 0.0 (inclusive) |
|
587 * and 1.0 (exclusive) |
|
588 */ |
|
589 public static double boundedNextDouble(RandomGenerator rng, double origin, double bound) { |
|
590 double r = rng.nextDouble(); |
|
591 if (origin < bound) { |
|
592 r = r * (bound - origin) + origin; |
|
593 if (r >= bound) // may need to correct a rounding problem |
|
594 r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1); |
|
595 } |
|
596 return r; |
|
597 } |
|
598 |
|
599 /** |
|
600 * This is the form of {@code nextDouble} used by the public method |
|
601 * {@code nextDouble(bound)}. This is essentially a version of |
|
602 * {@code boundedNextDouble(origin, bound)} that has been |
|
603 * specialized for the case where the {@code origin} is zero |
|
604 * and the {@code bound} is greater than zero. |
|
605 * |
|
606 * @implNote The result of a call to {@code nextDouble} is |
|
607 * multiplied by {@code bound}, and then if this result is |
|
608 * not less than {@code bound} (which can sometimes occur |
|
609 * because of rounding), it is replaced with the largest |
|
610 * {@code double} value that is less than {@code bound}. |
|
611 * |
|
612 * @param rng a random number generator to be used as a |
|
613 * source of pseudorandom {@code double} values |
|
614 * @param bound the upper bound (exclusive); must be finite and |
|
615 * greater than zero |
|
616 * @return a pseudorandomly chosen {@code double} value |
|
617 * between zero (inclusive) and {@code bound} (exclusive) |
|
618 */ |
|
619 public static double boundedNextDouble(RandomGenerator rng, double bound) { |
|
620 // Specialize boundedNextDouble for origin == 0, bound > 0 |
|
621 double r = rng.nextDouble(); |
|
622 r = r * bound; |
|
623 if (r >= bound) // may need to correct a rounding problem |
|
624 r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1); |
|
625 return r; |
|
626 } |
|
627 |
|
628 /** |
|
629 * This is the form of {@code nextFloat} used by a {@code Stream<Float>} |
|
630 * {@link Spliterator} (if there were any) and by the public method |
|
631 * {@code nextFloat(origin, bound)}. If {@code origin} is greater |
|
632 * than {@code bound}, then this method simply calls the unbounded |
|
633 * version of {@code nextFloat()}, and otherwise scales and translates |
|
634 * the result of a call to {@code nextFloat()} so that it lies |
|
635 * between {@code origin} (inclusive) and {@code bound} (exclusive). |
|
636 * |
|
637 * @implNote The implementation of this method is identical to |
|
638 * the implementation of {@code nextDouble(origin, bound)} |
|
639 * except that {@code float} values and the {@code nextFloat()} |
|
640 * method are used rather than {@code double} values and the |
|
641 * {@code nextDouble()} method. |
|
642 * |
|
643 * @param rng a random number generator to be used as a |
|
644 * source of pseudorandom {@code float} values |
|
645 * @param origin the least value that can be produced, |
|
646 * unless greater than or equal to {@code bound}; must be finite |
|
647 * @param bound the upper bound (exclusive), unless {@code origin} |
|
648 * is greater than or equal to {@code bound}; must be finite |
|
649 * @return a pseudorandomly chosen {@code float} value, |
|
650 * which will be between {@code origin} (inclusive) and |
|
651 * {@code bound} exclusive unless {@code origin} |
|
652 * is greater than or equal to {@code bound}, |
|
653 * in which case it will be between 0.0 (inclusive) |
|
654 * and 1.0 (exclusive) |
|
655 */ |
|
656 public static float boundedNextFloat(RandomGenerator rng, float origin, float bound) { |
|
657 float r = rng.nextFloat(); |
|
658 if (origin < bound) { |
|
659 r = r * (bound - origin) + origin; |
|
660 if (r >= bound) // may need to correct a rounding problem |
|
661 r = Float.intBitsToFloat(Float.floatToIntBits(bound) - 1); |
|
662 } |
|
663 return r; |
|
664 } |
|
665 |
|
666 /** |
|
667 * This is the form of {@code nextFloat} used by the public method |
|
668 * {@code nextFloat(bound)}. This is essentially a version of |
|
669 * {@code boundedNextFloat(origin, bound)} that has been |
|
670 * specialized for the case where the {@code origin} is zero |
|
671 * and the {@code bound} is greater than zero. |
|
672 * |
|
673 * @implNote The implementation of this method is identical to |
|
674 * the implementation of {@code nextDouble(bound)} |
|
675 * except that {@code float} values and the {@code nextFloat()} |
|
676 * method are used rather than {@code double} values and the |
|
677 * {@code nextDouble()} method. |
|
678 * |
|
679 * @param rng a random number generator to be used as a |
|
680 * source of pseudorandom {@code float} values |
|
681 * @param bound the upper bound (exclusive); must be finite and |
|
682 * greater than zero |
|
683 * @return a pseudorandomly chosen {@code float} value |
|
684 * between zero (inclusive) and {@code bound} (exclusive) |
|
685 */ |
|
686 public static float boundedNextFloat(RandomGenerator rng, float bound) { |
|
687 // Specialize boundedNextFloat for origin == 0, bound > 0 |
|
688 float r = rng.nextFloat(); |
|
689 r = r * bound; |
|
690 if (r >= bound) // may need to correct a rounding problem |
|
691 r = Float.intBitsToFloat(Float.floatToIntBits(bound) - 1); |
|
692 return r; |
|
693 } |
|
694 |
|
695 // The following decides which of two strategies initialSeed() will use. |
|
696 private static boolean secureRandomSeedRequested() { |
|
697 String pp = java.security.AccessController.doPrivileged( |
|
698 new sun.security.action.GetPropertyAction( |
|
699 "java.util.secureRandomSeed")); |
|
700 return (pp != null && pp.equalsIgnoreCase("true")); |
|
701 } |
|
702 |
|
703 private static final boolean useSecureRandomSeed = secureRandomSeedRequested(); |
|
704 |
|
705 /** |
|
706 * Returns a {@code long} value (chosen from some |
|
707 * machine-dependent entropy source) that may be useful for |
|
708 * initializing a source of seed values for instances of {@link RandomGenerator} |
|
709 * created by zero-argument constructors. (This method should |
|
710 * <i>not</i> be called repeatedly, once per constructed |
|
711 * object; at most it should be called once per class.) |
|
712 * |
|
713 * @return a {@code long} value, randomly chosen using |
|
714 * appropriate environmental entropy |
|
715 */ |
|
716 public static long initialSeed() { |
|
717 if (useSecureRandomSeed) { |
|
718 byte[] seedBytes = java.security.SecureRandom.getSeed(8); |
|
719 long s = (long)(seedBytes[0]) & 0xffL; |
|
720 for (int i = 1; i < 8; ++i) |
|
721 s = (s << 8) | ((long)(seedBytes[i]) & 0xffL); |
|
722 return s; |
|
723 } |
|
724 return (mixStafford13(System.currentTimeMillis()) ^ |
|
725 mixStafford13(System.nanoTime())); |
|
726 } |
|
727 |
|
728 /** |
|
729 * The first 32 bits of the golden ratio (1+sqrt(5))/2, forced to be odd. |
|
730 * Useful for producing good Weyl sequences or as an arbitrary nonzero odd value. |
|
731 */ |
|
732 public static final int GOLDEN_RATIO_32 = 0x9e3779b9; |
|
733 |
|
734 /** |
|
735 * The first 64 bits of the golden ratio (1+sqrt(5))/2, forced to be odd. |
|
736 * Useful for producing good Weyl sequences or as an arbitrary nonzero odd value. |
|
737 */ |
|
738 public static final long GOLDEN_RATIO_64 = 0x9e3779b97f4a7c15L; |
|
739 |
|
740 /** |
|
741 * The first 32 bits of the silver ratio 1+sqrt(2), forced to be odd. |
|
742 * Useful for producing good Weyl sequences or as an arbitrary nonzero odd value. |
|
743 */ |
|
744 public static final int SILVER_RATIO_32 = 0x6A09E667; |
|
745 |
|
746 /** |
|
747 * The first 64 bits of the silver ratio 1+sqrt(2), forced to be odd. |
|
748 * Useful for producing good Weyl sequences or as an arbitrary nonzero odd value. |
|
749 */ |
|
750 public static final long SILVER_RATIO_64 = 0x6A09E667F3BCC909L; |
|
751 |
|
752 /** |
|
753 * Computes the 64-bit mixing function for MurmurHash3. |
|
754 * This is a 64-bit hashing function with excellent avalanche statistics. |
|
755 * https://github.com/aappleby/smhasher/wiki/MurmurHash3 |
|
756 * |
|
757 * Note that if the argument {@code z} is 0, the result is 0. |
|
758 * |
|
759 * @param z any long value |
|
760 * |
|
761 * @return the result of hashing z |
|
762 */ |
|
763 public static long mixMurmur64(long z) { |
|
764 z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL; |
|
765 z = (z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L; |
|
766 return z ^ (z >>> 33); |
|
767 } |
|
768 |
|
769 /** |
|
770 * Computes Stafford variant 13 of the 64-bit mixing function for MurmurHash3. |
|
771 * This is a 64-bit hashing function with excellent avalanche statistics. |
|
772 * http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html |
|
773 * |
|
774 * Note that if the argument {@code z} is 0, the result is 0. |
|
775 * |
|
776 * @param z any long value |
|
777 * |
|
778 * @return the result of hashing z |
|
779 */ |
|
780 public static long mixStafford13(long z) { |
|
781 z = (z ^ (z >>> 30)) * 0xbf58476d1ce4e5b9L; |
|
782 z = (z ^ (z >>> 27)) * 0x94d049bb133111ebL; |
|
783 return z ^ (z >>> 31); |
|
784 } |
|
785 |
|
786 /** |
|
787 * Computes Doug Lea's 64-bit mixing function. |
|
788 * This is a 64-bit hashing function with excellent avalanche statistics. |
|
789 * It has the advantages of using the same multiplicative constant twice |
|
790 * and of using only 32-bit shifts. |
|
791 * |
|
792 * Note that if the argument {@code z} is 0, the result is 0. |
|
793 * |
|
794 * @param z any long value |
|
795 * |
|
796 * @return the result of hashing z |
|
797 */ |
|
798 public static long mixLea64(long z) { |
|
799 z = (z ^ (z >>> 32)) * 0xdaba0b6eb09322e3L; |
|
800 z = (z ^ (z >>> 32)) * 0xdaba0b6eb09322e3L; |
|
801 return z ^ (z >>> 32); |
|
802 } |
|
803 |
|
804 /** |
|
805 * Computes the 32-bit mixing function for MurmurHash3. |
|
806 * This is a 32-bit hashing function with excellent avalanche statistics. |
|
807 * https://github.com/aappleby/smhasher/wiki/MurmurHash3 |
|
808 * |
|
809 * Note that if the argument {@code z} is 0, the result is 0. |
|
810 * |
|
811 * @param z any long value |
|
812 * |
|
813 * @return the result of hashing z |
|
814 */ |
|
815 public static int mixMurmur32(int z) { |
|
816 z = (z ^ (z >>> 16)) * 0x85ebca6b; |
|
817 z = (z ^ (z >>> 13)) * 0xc2b2ae35; |
|
818 return z ^ (z >>> 16); |
|
819 } |
|
820 |
|
821 /** |
|
822 * Computes Doug Lea's 32-bit mixing function. |
|
823 * This is a 32-bit hashing function with excellent avalanche statistics. |
|
824 * It has the advantages of using the same multiplicative constant twice |
|
825 * and of using only 16-bit shifts. |
|
826 * |
|
827 * Note that if the argument {@code z} is 0, the result is 0. |
|
828 * |
|
829 * @param z any long value |
|
830 * |
|
831 * @return the result of hashing z |
|
832 */ |
|
833 public static int mixLea32(int z) { |
|
834 z = (z ^ (z >>> 16)) * 0xd36d884b; |
|
835 z = (z ^ (z >>> 16)) * 0xd36d884b; |
|
836 return z ^ (z >>> 16); |
|
837 } |
|
838 |
|
839 // Non-public (package only) support for spliterators needed by AbstractSplittableGenerator |
|
840 // and AbstractArbitrarilyJumpableGenerator and AbstractSharedGenerator |
|
841 |
|
842 /** |
|
843 * Base class for making Spliterator classes for streams of randomly chosen values. |
|
844 */ |
|
845 public abstract static class RandomSpliterator { |
|
846 |
|
847 /** low range value */ |
|
848 public long index; |
|
849 |
|
850 /** high range value */ |
|
851 public final long fence; |
|
852 |
|
853 /** |
|
854 * Constructor |
|
855 * |
|
856 * @param index low range value |
|
857 * @param fence high range value |
|
858 */ |
|
859 public RandomSpliterator(long index, long fence) { |
|
860 this.index = index; this.fence = fence; |
|
861 } |
|
862 |
|
863 /** |
|
864 * Returns estimated size. |
|
865 * |
|
866 * @return estimated size |
|
867 */ |
|
868 public long estimateSize() { |
|
869 return fence - index; |
|
870 } |
|
871 |
|
872 /** |
|
873 * Returns characteristics. |
|
874 * |
|
875 * @return characteristics |
|
876 */ |
|
877 public int characteristics() { |
|
878 return (Spliterator.SIZED | Spliterator.SUBSIZED | |
|
879 Spliterator.NONNULL | Spliterator.IMMUTABLE); |
|
880 } |
|
881 } |
|
882 |
|
883 |
|
884 /* |
|
885 * Implementation support for nextExponential() and nextGaussian() methods of RandomGenerator. |
|
886 * |
|
887 * Each is implemented using McFarland's fast modified ziggurat algorithm (largely |
|
888 * table-driven, with rare cases handled by computation and rejection sampling). |
|
889 * Walker's alias method for sampling a discrete distribution also plays a role. |
|
890 * |
|
891 * The tables themselves, as well as a number of associated parameters, are defined |
|
892 * in class java.util.DoubleZigguratTables, which is automatically generated by the |
|
893 * program create_ziggurat_tables.c (which takes only a few seconds to run). |
|
894 * |
|
895 * For more information about the algorithms, see these articles: |
|
896 * |
|
897 * Christopher D. McFarland. 2016 (published online 24 Jun 2015). A modified ziggurat |
|
898 * algorithm for generating exponentially and normally distributed pseudorandom numbers. |
|
899 * Journal of Statistical Computation and Simulation 86 (7), pages 1281-1294. |
|
900 * https://www.tandfonline.com/doi/abs/10.1080/00949655.2015.1060234 |
|
901 * Also at https://arxiv.org/abs/1403.6870 (26 March 2014). |
|
902 * |
|
903 * Alastair J. Walker. 1977. An efficient method for generating discrete random |
|
904 * variables with general distributions. ACM Trans. Math. Software 3, 3 |
|
905 * (September 1977), 253-256. DOI: https://doi.org/10.1145/355744.355749 |
|
906 * |
|
907 * Certain details of these algorithms depend critically on the quality of the |
|
908 * low-order bits delivered by NextLong(). These algorithms should not be used |
|
909 * with RNG algorithms (such as a simple Linear Congruential Generator) whose |
|
910 * low-order output bits do not have good statistical quality. |
|
911 */ |
|
912 |
|
913 // Implementation support for nextExponential() |
|
914 |
|
915 static double computeNextExponential(RandomGenerator rng) { |
|
916 long U1 = rng.nextLong(); |
|
917 // Experimentation on a variety of machines indicates that it is overall much faster |
|
918 // to do the following & and < operations on longs rather than first cast U1 to int |
|
919 // (but then we need to cast to int before doing the array indexing operation). |
|
920 long i = U1 & DoubleZigguratTables.exponentialLayerMask; |
|
921 if (i < DoubleZigguratTables.exponentialNumberOfLayers) { |
|
922 // This is the fast path (occurring more than 98% of the time). Make an early exit. |
|
923 return DoubleZigguratTables.exponentialX[(int)i] * (U1 >>> 1); |
|
924 } |
|
925 // We didn't use the upper part of U1 after all. We'll be able to use it later. |
|
926 |
|
927 for (double extra = 0.0; ; ) { |
|
928 // Use Walker's alias method to sample an (unsigned) integer j from a discrete |
|
929 // probability distribution that includes the tail and all the ziggurat overhangs; |
|
930 // j will be less than DoubleZigguratTables.exponentialNumberOfLayers + 1. |
|
931 long UA = rng.nextLong(); |
|
932 int j = (int)UA & DoubleZigguratTables.exponentialAliasMask; |
|
933 if (UA >= DoubleZigguratTables.exponentialAliasThreshold[j]) { |
|
934 j = DoubleZigguratTables.exponentialAliasMap[j] & |
|
935 DoubleZigguratTables.exponentialSignCorrectionMask; |
|
936 } |
|
937 if (j > 0) { // Sample overhang j |
|
938 // For the exponential distribution, every overhang is convex. |
|
939 final double[] X = DoubleZigguratTables.exponentialX; |
|
940 final double[] Y = DoubleZigguratTables.exponentialY; |
|
941 for (;; U1 = (rng.nextLong() >>> 1)) { |
|
942 long U2 = (rng.nextLong() >>> 1); |
|
943 // Compute the actual x-coordinate of the randomly chosen point. |
|
944 double x = (X[j] * 0x1.0p63) + ((X[j-1] - X[j]) * (double)U1); |
|
945 // Does the point lie below the curve? |
|
946 long Udiff = U2 - U1; |
|
947 if (Udiff < 0) { |
|
948 // We picked a point in the upper-right triangle. None of those can be |
|
949 // accepted. So remap the point into the lower-left triangle and try that. |
|
950 // In effect, we swap U1 and U2, and invert the sign of Udiff. |
|
951 Udiff = -Udiff; |
|
952 U2 = U1; |
|
953 U1 -= Udiff; |
|
954 } |
|
955 if (Udiff >= DoubleZigguratTables.exponentialConvexMargin) { |
|
956 return x + extra; // The chosen point is way below the curve; accept it. |
|
957 } |
|
958 // Compute the actual y-coordinate of the randomly chosen point. |
|
959 double y = (Y[j] * 0x1.0p63) + ((Y[j] - Y[j-1]) * (double)U2); |
|
960 // Now see how that y-coordinate compares to the curve |
|
961 if (y <= Math.exp(-x)) { |
|
962 return x + extra; // The chosen point is below the curve; accept it. |
|
963 } |
|
964 // Otherwise, we reject this sample and have to try again. |
|
965 } |
|
966 } |
|
967 // We are now committed to sampling from the tail. We could do a recursive call |
|
968 // and then add X[0] but we save some time and stack space by using an iterative loop. |
|
969 extra += DoubleZigguratTables.exponentialX0; |
|
970 // This is like the first five lines of this method, but if it returns, it first adds "extra". |
|
971 U1 = rng.nextLong(); |
|
972 i = U1 & DoubleZigguratTables.exponentialLayerMask; |
|
973 if (i < DoubleZigguratTables.exponentialNumberOfLayers) { |
|
974 return DoubleZigguratTables.exponentialX[(int)i] * (U1 >>> 1) + extra; |
|
975 } |
|
976 } |
|
977 } |
|
978 |
|
979 // Implementation support for nextGaussian() |
|
980 |
|
981 static double computeNextGaussian(RandomGenerator rng) { |
|
982 long U1 = rng.nextLong(); |
|
983 // Experimentation on a variety of machines indicates that it is overall much faster |
|
984 // to do the following & and < operations on longs rather than first cast U1 to int |
|
985 // (but then we need to cast to int before doing the array indexing operation). |
|
986 long i = U1 & DoubleZigguratTables.normalLayerMask; |
|
987 |
|
988 if (i < DoubleZigguratTables.normalNumberOfLayers) { |
|
989 // This is the fast path (occurring more than 98% of the time). Make an early exit. |
|
990 return DoubleZigguratTables.normalX[(int)i] * U1; // Note that the sign bit of U1 is used here. |
|
991 } |
|
992 // We didn't use the upper part of U1 after all. |
|
993 // Pull U1 apart into a sign bit and a 63-bit value for later use. |
|
994 double signBit = (U1 >= 0) ? 1.0 : -1.0; |
|
995 U1 = (U1 << 1) >>> 1; |
|
996 |
|
997 // Use Walker's alias method to sample an (unsigned) integer j from a discrete |
|
998 // probability distribution that includes the tail and all the ziggurat overhangs; |
|
999 // j will be less than DoubleZigguratTables.normalNumberOfLayers + 1. |
|
1000 long UA = rng.nextLong(); |
|
1001 int j = (int)UA & DoubleZigguratTables.normalAliasMask; |
|
1002 if (UA >= DoubleZigguratTables.normalAliasThreshold[j]) { |
|
1003 j = DoubleZigguratTables.normalAliasMap[j] & DoubleZigguratTables.normalSignCorrectionMask; |
|
1004 } |
|
1005 |
|
1006 double x; |
|
1007 // Now the goal is to choose the result, which will be multiplied by signBit just before return. |
|
1008 |
|
1009 // There are four kinds of overhangs: |
|
1010 // |
|
1011 // j == 0 : Sample from tail |
|
1012 // 0 < j < normalInflectionIndex : Overhang is convex; can reject upper-right triangle |
|
1013 // j == normalInflectionIndex : Overhang includes the inflection point |
|
1014 // j > normalInflectionIndex : Overhang is concave; can accept point in lower-left triangle |
|
1015 // |
|
1016 // Choose one of four loops to compute x, each specialized for a specific kind of overhang. |
|
1017 // Conditional statements are arranged such that the more likely outcomes are first. |
|
1018 |
|
1019 // In the three cases other than the tail case: |
|
1020 // U1 represents a fraction (scaled by 2**63) of the width of rectangle measured from the left. |
|
1021 // U2 represents a fraction (scaled by 2**63) of the height of rectangle measured from the top. |
|
1022 // Together they indicate a randomly chosen point within the rectangle. |
|
1023 |
|
1024 final double[] X = DoubleZigguratTables.normalX; |
|
1025 final double[] Y = DoubleZigguratTables.normalY; |
|
1026 if (j > DoubleZigguratTables.normalInflectionIndex) { // Concave overhang |
|
1027 for (;; U1 = (rng.nextLong() >>> 1)) { |
|
1028 long U2 = (rng.nextLong() >>> 1); |
|
1029 // Compute the actual x-coordinate of the randomly chosen point. |
|
1030 x = (X[j] * 0x1.0p63) + ((X[j-1] - X[j]) * (double)U1); |
|
1031 // Does the point lie below the curve? |
|
1032 long Udiff = U2 - U1; |
|
1033 if (Udiff >= 0) { |
|
1034 break; // The chosen point is in the lower-left triangle; accept it. |
|
1035 } |
|
1036 if (Udiff <= -DoubleZigguratTables.normalConcaveMargin) { |
|
1037 continue; // The chosen point is way above the curve; reject it. |
|
1038 } |
|
1039 // Compute the actual y-coordinate of the randomly chosen point. |
|
1040 double y = (Y[j] * 0x1.0p63) + ((Y[j] - Y[j-1]) * (double)U2); |
|
1041 // Now see how that y-coordinate compares to the curve |
|
1042 if (y <= Math.exp(-0.5*x*x)) { |
|
1043 break; // The chosen point is below the curve; accept it. |
|
1044 } |
|
1045 // Otherwise, we reject this sample and have to try again. |
|
1046 } |
|
1047 } else if (j == 0) { // Tail |
|
1048 // Tail-sampling method of Marsaglia and Tsang. See any one of: |
|
1049 // Marsaglia and Tsang. 1984. A fast, easily implemented method for sampling from decreasing |
|
1050 // or symmetric unimodal density functions. SIAM J. Sci. Stat. Comput. 5, 349-359. |
|
1051 // Marsaglia and Tsang. 1998. The Monty Python method for generating random variables. |
|
1052 // ACM Trans. Math. Softw. 24, 3 (September 1998), 341-350. See page 342, step (4). |
|
1053 // http://doi.org/10.1145/292395.292453 |
|
1054 // Thomas, Luk, Leong, and Villasenor. 2007. Gaussian random number generators. |
|
1055 // ACM Comput. Surv. 39, 4, Article 11 (November 2007). See Algorithm 16. |
|
1056 // http://doi.org/10.1145/1287620.1287622 |
|
1057 // Compute two separate random exponential samples and then compare them in certain way. |
|
1058 do { |
|
1059 x = (1.0 / DoubleZigguratTables.normalX0) * computeNextExponential(rng); |
|
1060 } while (computeNextExponential(rng) < 0.5*x*x); |
|
1061 x += DoubleZigguratTables.normalX0; |
|
1062 } else if (j < DoubleZigguratTables.normalInflectionIndex) { // Convex overhang |
|
1063 for (;; U1 = (rng.nextLong() >>> 1)) { |
|
1064 long U2 = (rng.nextLong() >>> 1); |
|
1065 // Compute the actual x-coordinate of the randomly chosen point. |
|
1066 x = (X[j] * 0x1.0p63) + ((X[j-1] - X[j]) * (double)U1); |
|
1067 // Does the point lie below the curve? |
|
1068 long Udiff = U2 - U1; |
|
1069 if (Udiff < 0) { |
|
1070 // We picked a point in the upper-right triangle. None of those can be accepted. |
|
1071 // So remap the point into the lower-left triangle and try that. |
|
1072 // In effect, we swap U1 and U2, and invert the sign of Udiff. |
|
1073 Udiff = -Udiff; |
|
1074 U2 = U1; |
|
1075 U1 -= Udiff; |
|
1076 } |
|
1077 if (Udiff >= DoubleZigguratTables.normalConvexMargin) { |
|
1078 break; // The chosen point is way below the curve; accept it. |
|
1079 } |
|
1080 // Compute the actual y-coordinate of the randomly chosen point. |
|
1081 double y = (Y[j] * 0x1.0p63) + ((Y[j] - Y[j-1]) * (double)U2); |
|
1082 // Now see how that y-coordinate compares to the curve |
|
1083 if (y <= Math.exp(-0.5*x*x)) break; // The chosen point is below the curve; accept it. |
|
1084 // Otherwise, we reject this sample and have to try again. |
|
1085 } |
|
1086 } else { |
|
1087 // The overhang includes the inflection point, so the curve is both convex and concave |
|
1088 for (;; U1 = (rng.nextLong() >>> 1)) { |
|
1089 long U2 = (rng.nextLong() >>> 1); |
|
1090 // Compute the actual x-coordinate of the randomly chosen point. |
|
1091 x = (X[j] * 0x1.0p63) + ((X[j-1] - X[j]) * (double)U1); |
|
1092 // Does the point lie below the curve? |
|
1093 long Udiff = U2 - U1; |
|
1094 if (Udiff >= DoubleZigguratTables.normalConvexMargin) { |
|
1095 break; // The chosen point is way below the curve; accept it. |
|
1096 } |
|
1097 if (Udiff <= -DoubleZigguratTables.normalConcaveMargin) { |
|
1098 continue; // The chosen point is way above the curve; reject it. |
|
1099 } |
|
1100 // Compute the actual y-coordinate of the randomly chosen point. |
|
1101 double y = (Y[j] * 0x1.0p63) + ((Y[j] - Y[j-1]) * (double)U2); |
|
1102 // Now see how that y-coordinate compares to the curve |
|
1103 if (y <= Math.exp(-0.5*x*x)) { |
|
1104 break; // The chosen point is below the curve; accept it. |
|
1105 } |
|
1106 // Otherwise, we reject this sample and have to try again. |
|
1107 } |
|
1108 } |
|
1109 return signBit*x; |
|
1110 } |
|
1111 |
|
1112 /** |
|
1113 * This class overrides the stream-producing methods (such as {@code ints()}) |
|
1114 * in class {@link AbstractGenerator} to provide {@link Spliterator}-based |
|
1115 * implmentations that support potentially parallel execution. |
|
1116 * |
|
1117 * To implement a pseudorandom number generator, the programmer needs |
|
1118 * only to extend this class and provide implementations for the methods |
|
1119 * {@code nextInt()}, {@code nextLong()}, {@code makeIntsSpliterator}, |
|
1120 * {@code makeLongsSpliterator}, and {@code makeDoublesSpliterator}. |
|
1121 * |
|
1122 * This class is not public; it provides shared code to the public |
|
1123 * classes {@link AbstractSplittableGenerator}, {@link AbstractSharedGenerator}, |
|
1124 * and {@link AbstractArbitrarilyJumpableGenerator}. |
|
1125 * |
|
1126 * @since 14 |
|
1127 */ |
|
1128 public abstract static class AbstractSpliteratorGenerator implements RandomGenerator { |
|
1129 /* |
|
1130 * Implementation Overview. |
|
1131 * |
|
1132 * This class provides most of the "user API" methods needed to |
|
1133 * satisfy the interface RandomGenerator. An implementation of this |
|
1134 * interface need only extend this class and provide implementations |
|
1135 * of six methods: nextInt, nextLong, and nextDouble (the versions |
|
1136 * that take no arguments) and makeIntsSpliterator, |
|
1137 * makeLongsSpliterator, and makeDoublesSpliterator. |
|
1138 * |
|
1139 * File organization: First the non-public abstract methods needed |
|
1140 * to create spliterators, then the main public methods. |
|
1141 */ |
|
1142 |
|
1143 /** |
|
1144 * Create an instance of {@link Spliterator.OfInt} that for each traversal position |
|
1145 * between the specified index (inclusive) and the specified fence (exclusive) generates |
|
1146 * a pseudorandomly chosen {@code int} value between the specified origin (inclusive) and |
|
1147 * the specified bound (exclusive). |
|
1148 * |
|
1149 * @param index the (inclusive) lower bound on traversal positions |
|
1150 * @param fence the (exclusive) upper bound on traversal positions |
|
1151 * @param origin the (inclusive) lower bound on the pseudorandom values to be generated |
|
1152 * @param bound the (exclusive) upper bound on the pseudorandom values to be generated |
|
1153 * @return an instance of {@link Spliterator.OfInt} |
|
1154 */ |
|
1155 public abstract Spliterator.OfInt makeIntsSpliterator(long index, long fence, int origin, int bound); |
|
1156 |
|
1157 /** |
|
1158 * Create an instance of {@link Spliterator.OfLong} that for each traversal position |
|
1159 * between the specified index (inclusive) and the specified fence (exclusive) generates |
|
1160 * a pseudorandomly chosen {@code long} value between the specified origin (inclusive) and |
|
1161 * the specified bound (exclusive). |
|
1162 * |
|
1163 * @param index the (inclusive) lower bound on traversal positions |
|
1164 * @param fence the (exclusive) upper bound on traversal positions |
|
1165 * @param origin the (inclusive) lower bound on the pseudorandom values to be generated |
|
1166 * @param bound the (exclusive) upper bound on the pseudorandom values to be generated |
|
1167 * @return an instance of {@link Spliterator.OfLong} |
|
1168 */ |
|
1169 public abstract Spliterator.OfLong makeLongsSpliterator(long index, long fence, long origin, long bound); |
|
1170 |
|
1171 /** |
|
1172 * Create an instance of {@link Spliterator.OfDouble} that for each traversal position |
|
1173 * between the specified index (inclusive) and the specified fence (exclusive) generates |
|
1174 * a pseudorandomly chosen {@code double} value between the specified origin (inclusive) and |
|
1175 * the specified bound (exclusive). |
|
1176 * |
|
1177 * @param index the (inclusive) lower bound on traversal positions |
|
1178 * @param fence the (exclusive) upper bound on traversal positions |
|
1179 * @param origin the (inclusive) lower bound on the pseudorandom values to be generated |
|
1180 * @param bound the (exclusive) upper bound on the pseudorandom values to be generated |
|
1181 * @return an instance of {@link Spliterator.OfDouble} |
|
1182 */ |
|
1183 public abstract Spliterator.OfDouble makeDoublesSpliterator(long index, long fence, double origin, double bound); |
|
1184 |
|
1185 /* ---------------- public methods ---------------- */ |
|
1186 |
|
1187 // stream methods, coded in a way intended to better isolate for |
|
1188 // maintenance purposes the small differences across forms. |
|
1189 |
|
1190 private static IntStream intStream(Spliterator.OfInt srng) { |
|
1191 return StreamSupport.intStream(srng, false); |
|
1192 } |
|
1193 |
|
1194 private static LongStream longStream(Spliterator.OfLong srng) { |
|
1195 return StreamSupport.longStream(srng, false); |
|
1196 } |
|
1197 |
|
1198 private static DoubleStream doubleStream(Spliterator.OfDouble srng) { |
|
1199 return StreamSupport.doubleStream(srng, false); |
|
1200 } |
|
1201 |
|
1202 /** |
|
1203 * Returns a stream producing the given {@code streamSize} number of pseudorandom {@code int} |
|
1204 * values from this generator and/or one split from it. |
|
1205 * |
|
1206 * @param streamSize the number of values to generate |
|
1207 * |
|
1208 * @return a stream of pseudorandom {@code int} values |
|
1209 * |
|
1210 * @throws IllegalArgumentException if {@code streamSize} is less than zero |
|
1211 */ |
|
1212 public IntStream ints(long streamSize) { |
|
1213 RandomSupport.checkStreamSize(streamSize); |
|
1214 return intStream(makeIntsSpliterator(0L, streamSize, Integer.MAX_VALUE, 0)); |
|
1215 } |
|
1216 |
|
1217 /** |
|
1218 * Returns an effectively unlimited stream of pseudorandomly chosen |
|
1219 * {@code int} values. |
|
1220 * |
|
1221 * @implNote The implementation of this method is effectively |
|
1222 * equivalent to {@code ints(Long.MAX_VALUE)}. |
|
1223 * |
|
1224 * @return a stream of pseudorandomly chosen {@code int} values |
|
1225 */ |
|
1226 |
|
1227 public IntStream ints() { |
|
1228 return intStream(makeIntsSpliterator(0L, Long.MAX_VALUE, Integer.MAX_VALUE, 0)); |
|
1229 } |
|
1230 |
|
1231 /** |
|
1232 * Returns a stream producing the given {@code streamSize} number of pseudorandom {@code int} |
|
1233 * values from this generator and/or one split from it; each value conforms to the given origin |
|
1234 * (inclusive) and bound (exclusive). |
|
1235 * |
|
1236 * @param streamSize the number of values to generate |
|
1237 * @param randomNumberOrigin the origin (inclusive) of each random value |
|
1238 * @param randomNumberBound the bound (exclusive) of each random value |
|
1239 * |
|
1240 * @return a stream of pseudorandom {@code int} values, each with the given origin (inclusive) |
|
1241 * and bound (exclusive) |
|
1242 * |
|
1243 * @throws IllegalArgumentException if {@code streamSize} is less than zero, or {@code |
|
1244 * randomNumberOrigin} is greater than or equal to {@code |
|
1245 * randomNumberBound} |
|
1246 */ |
|
1247 public IntStream ints(long streamSize, int randomNumberOrigin, int randomNumberBound) { |
|
1248 RandomSupport.checkStreamSize(streamSize); |
|
1249 RandomSupport.checkRange(randomNumberOrigin, randomNumberBound); |
|
1250 return intStream(makeIntsSpliterator(0L, streamSize, randomNumberOrigin, randomNumberBound)); |
|
1251 } |
|
1252 |
|
1253 /** |
|
1254 * Returns an effectively unlimited stream of pseudorandom {@code int} values from this |
|
1255 * generator and/or one split from it; each value conforms to the given origin (inclusive) and |
|
1256 * bound (exclusive). |
|
1257 * |
|
1258 * @param randomNumberOrigin the origin (inclusive) of each random value |
|
1259 * @param randomNumberBound the bound (exclusive) of each random value |
|
1260 * |
|
1261 * @return a stream of pseudorandom {@code int} values, each with the given origin (inclusive) |
|
1262 * and bound (exclusive) |
|
1263 * |
|
1264 * @throws IllegalArgumentException if {@code randomNumberOrigin} is greater than or equal to |
|
1265 * {@code randomNumberBound} |
|
1266 * |
|
1267 * @implNote This method is implemented to be equivalent to {@code ints(Long.MAX_VALUE, |
|
1268 * randomNumberOrigin, randomNumberBound)}. |
|
1269 */ |
|
1270 public IntStream ints(int randomNumberOrigin, int randomNumberBound) { |
|
1271 RandomSupport.checkRange(randomNumberOrigin, randomNumberBound); |
|
1272 return intStream(makeIntsSpliterator(0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)); |
|
1273 } |
|
1274 |
|
1275 /** |
|
1276 * Returns a stream producing the given {@code streamSize} number of pseudorandom {@code long} |
|
1277 * values from this generator and/or one split from it. |
|
1278 * |
|
1279 * @param streamSize the number of values to generate |
|
1280 * |
|
1281 * @return a stream of pseudorandom {@code long} values |
|
1282 * |
|
1283 * @throws IllegalArgumentException if {@code streamSize} is less than zero |
|
1284 */ |
|
1285 public LongStream longs(long streamSize) { |
|
1286 RandomSupport.checkStreamSize(streamSize); |
|
1287 return longStream(makeLongsSpliterator(0L, streamSize, Long.MAX_VALUE, 0L)); |
|
1288 } |
|
1289 |
|
1290 /** |
|
1291 * Returns an effectively unlimited stream of pseudorandom {@code long} values from this |
|
1292 * generator and/or one split from it. |
|
1293 * |
|
1294 * @return a stream of pseudorandom {@code long} values |
|
1295 * |
|
1296 * @implNote This method is implemented to be equivalent to {@code |
|
1297 * longs(Long.MAX_VALUE)}. |
|
1298 */ |
|
1299 public LongStream longs() { |
|
1300 return longStream(makeLongsSpliterator(0L, Long.MAX_VALUE, Long.MAX_VALUE, 0L)); |
|
1301 } |
|
1302 |
|
1303 /** |
|
1304 * Returns a stream producing the given {@code streamSize} number of pseudorandom {@code long} |
|
1305 * values from this generator and/or one split from it; each value conforms to the given origin |
|
1306 * (inclusive) and bound (exclusive). |
|
1307 * |
|
1308 * @param streamSize the number of values to generate |
|
1309 * @param randomNumberOrigin the origin (inclusive) of each random value |
|
1310 * @param randomNumberBound the bound (exclusive) of each random value |
|
1311 * |
|
1312 * @return a stream of pseudorandom {@code long} values, each with the given origin (inclusive) |
|
1313 * and bound (exclusive) |
|
1314 * |
|
1315 * @throws IllegalArgumentException if {@code streamSize} is less than zero, or {@code |
|
1316 * randomNumberOrigin} is greater than or equal to {@code |
|
1317 * randomNumberBound} |
|
1318 */ |
|
1319 public LongStream longs(long streamSize, long randomNumberOrigin, |
|
1320 long randomNumberBound) { |
|
1321 RandomSupport.checkStreamSize(streamSize); |
|
1322 RandomSupport.checkRange(randomNumberOrigin, randomNumberBound); |
|
1323 return longStream(makeLongsSpliterator(0L, streamSize, randomNumberOrigin, randomNumberBound)); |
|
1324 } |
|
1325 |
|
1326 /** |
|
1327 * Returns an effectively unlimited stream of pseudorandom {@code long} values from this |
|
1328 * generator and/or one split from it; each value conforms to the given origin (inclusive) and |
|
1329 * bound (exclusive). |
|
1330 * |
|
1331 * @param randomNumberOrigin the origin (inclusive) of each random value |
|
1332 * @param randomNumberBound the bound (exclusive) of each random value |
|
1333 * |
|
1334 * @return a stream of pseudorandom {@code long} values, each with the given origin (inclusive) |
|
1335 * and bound (exclusive) |
|
1336 * |
|
1337 * @throws IllegalArgumentException if {@code randomNumberOrigin} is greater than or equal to |
|
1338 * {@code randomNumberBound} |
|
1339 * |
|
1340 * @implNote This method is implemented to be equivalent to {@code longs(Long.MAX_VALUE, |
|
1341 * randomNumberOrigin, randomNumberBound)}. |
|
1342 */ |
|
1343 public LongStream longs(long randomNumberOrigin, long randomNumberBound) { |
|
1344 RandomSupport.checkRange(randomNumberOrigin, randomNumberBound); |
|
1345 return StreamSupport.longStream |
|
1346 (makeLongsSpliterator(0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), |
|
1347 false); |
|
1348 } |
|
1349 |
|
1350 /** |
|
1351 * Returns a stream producing the given {@code streamSize} number of pseudorandom {@code double} |
|
1352 * values from this generator and/or one split from it; each value is between zero (inclusive) |
|
1353 * and one (exclusive). |
|
1354 * |
|
1355 * @param streamSize the number of values to generate |
|
1356 * |
|
1357 * @return a stream of {@code double} values |
|
1358 * |
|
1359 * @throws IllegalArgumentException if {@code streamSize} is less than zero |
|
1360 */ |
|
1361 public DoubleStream doubles(long streamSize) { |
|
1362 RandomSupport.checkStreamSize(streamSize); |
|
1363 return doubleStream(makeDoublesSpliterator(0L, streamSize, Double.MAX_VALUE, 0.0)); |
|
1364 } |
|
1365 |
|
1366 /** |
|
1367 * Returns an effectively unlimited stream of pseudorandom {@code double} values from this |
|
1368 * generator and/or one split from it; each value is between zero (inclusive) and one |
|
1369 * (exclusive). |
|
1370 * |
|
1371 * @return a stream of pseudorandom {@code double} values |
|
1372 * |
|
1373 * @implNote This method is implemented to be equivalent to {@code |
|
1374 * doubles(Long.MAX_VALUE)}. |
|
1375 */ |
|
1376 public DoubleStream doubles() { |
|
1377 return doubleStream(makeDoublesSpliterator(0L, Long.MAX_VALUE, Double.MAX_VALUE, 0.0)); |
|
1378 } |
|
1379 |
|
1380 /** |
|
1381 * Returns a stream producing the given {@code streamSize} number of pseudorandom {@code double} |
|
1382 * values from this generator and/or one split from it; each value conforms to the given origin |
|
1383 * (inclusive) and bound (exclusive). |
|
1384 * |
|
1385 * @param streamSize the number of values to generate |
|
1386 * @param randomNumberOrigin the origin (inclusive) of each random value |
|
1387 * @param randomNumberBound the bound (exclusive) of each random value |
|
1388 * |
|
1389 * @return a stream of pseudorandom {@code double} values, each with the given origin |
|
1390 * (inclusive) and bound (exclusive) |
|
1391 * |
|
1392 * @throws IllegalArgumentException if {@code streamSize} is less than zero |
|
1393 * @throws IllegalArgumentException if {@code randomNumberOrigin} is greater than or equal to |
|
1394 * {@code randomNumberBound} |
|
1395 */ |
|
1396 public DoubleStream doubles(long streamSize, double randomNumberOrigin, double randomNumberBound) { |
|
1397 RandomSupport.checkStreamSize(streamSize); |
|
1398 RandomSupport.checkRange(randomNumberOrigin, randomNumberBound); |
|
1399 return doubleStream(makeDoublesSpliterator(0L, streamSize, randomNumberOrigin, randomNumberBound)); |
|
1400 } |
|
1401 |
|
1402 /** |
|
1403 * Returns an effectively unlimited stream of pseudorandom {@code double} values from this |
|
1404 * generator and/or one split from it; each value conforms to the given origin (inclusive) and |
|
1405 * bound (exclusive). |
|
1406 * |
|
1407 * @param randomNumberOrigin the origin (inclusive) of each random value |
|
1408 * @param randomNumberBound the bound (exclusive) of each random value |
|
1409 * |
|
1410 * @return a stream of pseudorandom {@code double} values, each with the given origin |
|
1411 * (inclusive) and bound (exclusive) |
|
1412 * |
|
1413 * @throws IllegalArgumentException if {@code randomNumberOrigin} is greater than or equal to |
|
1414 * {@code randomNumberBound} |
|
1415 * |
|
1416 * @implNote This method is implemented to be equivalent to {@code |
|
1417 * doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. |
|
1418 */ |
|
1419 public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) { |
|
1420 RandomSupport.checkRange(randomNumberOrigin, randomNumberBound); |
|
1421 return doubleStream(makeDoublesSpliterator(0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)); |
|
1422 } |
|
1423 |
|
1424 } |
|
1425 |
|
1426 /** |
|
1427 * This class provides much of the implementation of the |
|
1428 * {@link ArbitrarilyJumpableGenerator} interface, to minimize the effort |
|
1429 * required to implement that interface. |
|
1430 * |
|
1431 * To implement a pseudorandom number generator, the programmer needs |
|
1432 * only to extend this class and provide implementations for the |
|
1433 * methods {@link #nextInt()}, {@link #nextLong()}, {@link #copy()}, |
|
1434 * {@link #jump(double)}, {@link #jumpPowerOfTwo(int)}, |
|
1435 * {@link #defaultJumpDistance()}, and {@link #defaultLeapDistance()}. |
|
1436 * |
|
1437 * (If the pseudorandom number generator also has the ability to split, |
|
1438 * then the programmer may wish to consider instead extending |
|
1439 * {@link AbstractSplittableGenerator}.) |
|
1440 * |
|
1441 * The programmer should generally provide at least three constructors: |
|
1442 * one that takes no arguments, one that accepts a {@code long} |
|
1443 * seed value, and one that accepts an array of seed {@code byte} values. |
|
1444 * This class provides a public {@code initialSeed()} method that may |
|
1445 * be useful in initializing some static state from which to derive |
|
1446 * defaults seeds for use by the no-argument constructor. |
|
1447 * |
|
1448 * For the stream methods (such as {@code ints()} and {@code splits()}), |
|
1449 * this class provides {@link Spliterator}-based implementations that |
|
1450 * allow parallel execution when appropriate. In this respect |
|
1451 * {@link ArbitrarilyJumpableGenerator} differs from {@link JumpableGenerator}, |
|
1452 * which provides very simple implementations that produce |
|
1453 * sequential streams only. |
|
1454 * |
|
1455 * <p>An implementation of the {@link AbstractArbitrarilyJumpableGenerator} class |
|
1456 * must provide concrete definitions for the methods {@code nextInt()}, |
|
1457 * {@code nextLong}, {@code period()}, {@code copy()}, {@code jump(double)}, |
|
1458 * {@code defaultJumpDistance()}, and {@code defaultLeapDistance()}. |
|
1459 * Default implementations are provided for all other methods. |
|
1460 * |
|
1461 * The documentation for each non-abstract method in this class |
|
1462 * describes its implementation in detail. Each of these methods may |
|
1463 * be overridden if the pseudorandom number generator being |
|
1464 * implemented admits a more efficient implementation. |
|
1465 * |
|
1466 * @since 14 |
|
1467 */ |
|
1468 public abstract static class AbstractArbitrarilyJumpableGenerator |
|
1469 extends AbstractSpliteratorGenerator implements RandomGenerator.ArbitrarilyJumpableGenerator { |
|
1470 |
|
1471 /* |
|
1472 * Implementation Overview. |
|
1473 * |
|
1474 * This class provides most of the "user API" methods needed to satisfy |
|
1475 * the interface ArbitrarilyJumpableGenerator. Most of these methods |
|
1476 * are in turn inherited from AbstractGenerator and the non-public class |
|
1477 * AbstractSpliteratorGenerator; this file implements four versions of the |
|
1478 * jumps method and defines the spliterators necessary to support them. |
|
1479 * |
|
1480 * File organization: First the non-public methods needed by the class |
|
1481 * AbstractSpliteratorGenerator, then the main public methods, followed by some |
|
1482 * custom spliterator classes needed for stream methods. |
|
1483 */ |
|
1484 |
|
1485 // IllegalArgumentException messages |
|
1486 static final String BadLogDistance = "logDistance must be non-negative"; |
|
1487 |
|
1488 // Methods required by class AbstractSpliteratorGenerator |
|
1489 public Spliterator.OfInt makeIntsSpliterator(long index, long fence, int origin, int bound) { |
|
1490 return new RandomIntsSpliterator(this, index, fence, origin, bound); |
|
1491 } |
|
1492 public Spliterator.OfLong makeLongsSpliterator(long index, long fence, long origin, long bound) { |
|
1493 return new RandomLongsSpliterator(this, index, fence, origin, bound); |
|
1494 } |
|
1495 public Spliterator.OfDouble makeDoublesSpliterator(long index, long fence, double origin, double bound) { |
|
1496 return new RandomDoublesSpliterator(this, index, fence, origin, bound); |
|
1497 } |
|
1498 |
|
1499 // Similar methods used by this class |
|
1500 Spliterator<RandomGenerator> makeJumpsSpliterator(long index, long fence, double distance) { |
|
1501 return new RandomJumpsSpliterator(this, index, fence, distance); |
|
1502 } |
|
1503 Spliterator<JumpableGenerator> makeLeapsSpliterator(long index, long fence, double distance) { |
|
1504 return new RandomLeapsSpliterator(this, index, fence, distance); |
|
1505 } |
|
1506 Spliterator<ArbitrarilyJumpableGenerator> makeArbitraryJumpsSpliterator(long index, long fence, double distance) { |
|
1507 return new RandomArbitraryJumpsSpliterator(this, index, fence, distance); |
|
1508 } |
|
1509 |
|
1510 /* ---------------- public methods ---------------- */ |
|
1511 |
|
1512 /** |
|
1513 * Returns a new generator whose internal state is an exact copy |
|
1514 * of this generator (therefore their future behavior should be |
|
1515 * identical if subjected to the same series of operations). |
|
1516 * |
|
1517 * @return a new object that is a copy of this generator |
|
1518 */ |
|
1519 public abstract AbstractArbitrarilyJumpableGenerator copy(); |
|
1520 |
|
1521 // Stream methods for jumping |
|
1522 |
|
1523 private static <T> Stream<T> stream(Spliterator<T> srng) { |
|
1524 return StreamSupport.stream(srng, false); |
|
1525 } |
|
1526 |
|
1527 /** |
|
1528 * Returns an effectively unlimited stream of new pseudorandom number generators, each of which |
|
1529 * implements the {@link RandomGenerator} interface, produced by jumping copies of this |
|
1530 * generator by different integer multiples of the default jump distance. |
|
1531 * |
|
1532 * @return a stream of objects that implement the {@link RandomGenerator} interface |
|
1533 * |
|
1534 * @implNote This method is implemented to be equivalent to {@code |
|
1535 * jumps(Long.MAX_VALUE)}. |
|
1536 */ |
|
1537 public Stream<RandomGenerator> jumps() { |
|
1538 return stream(makeJumpsSpliterator(0L, Long.MAX_VALUE, defaultJumpDistance())); |
|
1539 } |
|
1540 |
|
1541 /** |
|
1542 * Returns a stream producing the given {@code streamSize} number of |
|
1543 * new pseudorandom number generators, each of which implements the |
|
1544 * {@link RandomGenerator} interface, produced by jumping copies of this generator |
|
1545 * by different integer multiples of the default jump distance. |
|
1546 * |
|
1547 * @param streamSize the number of generators to generate |
|
1548 * |
|
1549 * @return a stream of objects that implement the {@link RandomGenerator} interface |
|
1550 * |
|
1551 * @throws IllegalArgumentException if {@code streamSize} is less than zero |
|
1552 */ |
|
1553 public Stream<RandomGenerator> jumps(long streamSize) { |
|
1554 RandomSupport.checkStreamSize(streamSize); |
|
1555 return stream(makeJumpsSpliterator(0L, streamSize, defaultJumpDistance())); |
|
1556 } |
|
1557 |
|
1558 /** |
|
1559 * Returns an effectively unlimited stream of new pseudorandom number generators, each of which |
|
1560 * implements the {@link RandomGenerator} interface, produced by jumping copies of this |
|
1561 * generator by different integer multiples of the specified jump distance. |
|
1562 * |
|
1563 * @param distance a distance to jump forward within the state cycle |
|
1564 * |
|
1565 * @return a stream of objects that implement the {@link RandomGenerator} interface |
|
1566 * |
|
1567 * @implNote This method is implemented to be equivalent to {@code |
|
1568 * jumps(Long.MAX_VALUE)}. |
|
1569 */ |
|
1570 public Stream<ArbitrarilyJumpableGenerator> jumps(double distance) { |
|
1571 return stream(makeArbitraryJumpsSpliterator(0L, Long.MAX_VALUE, distance)); |
|
1572 } |
|
1573 |
|
1574 /** |
|
1575 * Returns a stream producing the given {@code streamSize} number of new pseudorandom number |
|
1576 * generators, each of which implements the {@link RandomGenerator} interface, produced by |
|
1577 * jumping copies of this generator by different integer multiples of the specified jump |
|
1578 * distance. |
|
1579 * |
|
1580 * @param streamSize the number of generators to generate |
|
1581 * @param distance a distance to jump forward within the state cycle |
|
1582 * |
|
1583 * @return a stream of objects that implement the {@link RandomGenerator} interface |
|
1584 * |
|
1585 * @throws IllegalArgumentException if {@code streamSize} is less than zero |
|
1586 */ |
|
1587 public Stream<ArbitrarilyJumpableGenerator> jumps(long streamSize, double distance) { |
|
1588 RandomSupport.checkStreamSize(streamSize); |
|
1589 return stream(makeArbitraryJumpsSpliterator(0L, streamSize, distance)); |
|
1590 } |
|
1591 |
|
1592 /** |
|
1593 * Alter the state of this pseudorandom number generator so as to |
|
1594 * jump forward a very large, fixed distance (typically 2<sup>128</sup> |
|
1595 * or more) within its state cycle. The distance used is that |
|
1596 * returned by method {@code defaultLeapDistance()}. |
|
1597 */ |
|
1598 public void leap() { |
|
1599 jump(defaultLeapDistance()); |
|
1600 } |
|
1601 |
|
1602 // Stream methods for leaping |
|
1603 |
|
1604 /** |
|
1605 * Returns an effectively unlimited stream of new pseudorandom number generators, each of which |
|
1606 * implements the {@link RandomGenerator} interface, produced by jumping copies of this |
|
1607 * generator by different integer multiples of the default leap distance. |
|
1608 * |
|
1609 * @implNote This method is implemented to be equivalent to {@code leaps(Long.MAX_VALUE)}. |
|
1610 * |
|
1611 * @return a stream of objects that implement the {@link RandomGenerator} interface |
|
1612 */ |
|
1613 public Stream<JumpableGenerator> leaps() { |
|
1614 return stream(makeLeapsSpliterator(0L, Long.MAX_VALUE, defaultLeapDistance())); |
|
1615 } |
|
1616 |
|
1617 /** |
|
1618 * Returns a stream producing the given {@code streamSize} number of new pseudorandom number |
|
1619 * generators, each of which implements the {@link RandomGenerator} interface, produced by |
|
1620 * jumping copies of this generator by different integer multiples of the default leap |
|
1621 * distance. |
|
1622 * |
|
1623 * @param streamSize the number of generators to generate |
|
1624 * |
|
1625 * @return a stream of objects that implement the {@link RandomGenerator} interface |
|
1626 * |
|
1627 * @throws IllegalArgumentException if {@code streamSize} is less than zero |
|
1628 */ |
|
1629 public Stream<JumpableGenerator> leaps(long streamSize) { |
|
1630 return stream(makeLeapsSpliterator(0L, streamSize, defaultLeapDistance())); |
|
1631 } |
|
1632 |
|
1633 |
|
1634 /** |
|
1635 * Spliterator for int streams. We multiplex the four int versions into one class by treating a |
|
1636 * bound less than origin as unbounded, and also by treating "infinite" as equivalent to |
|
1637 * {@code Long.MAX_VALUE}. For splits, we choose to override the method {@code trySplit()} to |
|
1638 * try to optimize execution speed: instead of dividing a range in half, it breaks off the |
|
1639 * largest possible chunk whose size is a power of two such that the remaining chunk is not |
|
1640 * empty. In this way, the necessary jump distances will tend to be powers of two. The long |
|
1641 * and double versions of this class are identical except for types. |
|
1642 */ |
|
1643 static class RandomIntsSpliterator extends RandomSupport.RandomSpliterator implements Spliterator.OfInt { |
|
1644 final ArbitrarilyJumpableGenerator generatingGenerator; |
|
1645 final int origin; |
|
1646 final int bound; |
|
1647 |
|
1648 RandomIntsSpliterator(ArbitrarilyJumpableGenerator generatingGenerator, long index, long fence, int origin, int bound) { |
|
1649 super(index, fence); |
|
1650 this.origin = origin; this.bound = bound; |
|
1651 this.generatingGenerator = generatingGenerator; |
|
1652 } |
|
1653 |
|
1654 public Spliterator.OfInt trySplit() { |
|
1655 long i = index, delta = Long.highestOneBit((fence - i) - 1), m = i + delta; |
|
1656 if (m <= i) return null; |
|
1657 index = m; |
|
1658 ArbitrarilyJumpableGenerator r = generatingGenerator; |
|
1659 return new RandomIntsSpliterator(r.copyAndJump((double)delta), i, m, origin, bound); |
|
1660 } |
|
1661 |
|
1662 public boolean tryAdvance(IntConsumer consumer) { |
|
1663 if (consumer == null) throw new NullPointerException(); |
|
1664 long i = index, f = fence; |
|
1665 if (i < f) { |
|
1666 consumer.accept(RandomSupport.boundedNextInt(generatingGenerator, origin, bound)); |
|
1667 index = i + 1; |
|
1668 return true; |
|
1669 } |
|
1670 else return false; |
|
1671 } |
|
1672 |
|
1673 public void forEachRemaining(IntConsumer consumer) { |
|
1674 if (consumer == null) throw new NullPointerException(); |
|
1675 long i = index, f = fence; |
|
1676 if (i < f) { |
|
1677 index = f; |
|
1678 ArbitrarilyJumpableGenerator r = generatingGenerator; |
|
1679 int o = origin, b = bound; |
|
1680 do { |
|
1681 consumer.accept(RandomSupport.boundedNextInt(r, o, b)); |
|
1682 } while (++i < f); |
|
1683 } |
|
1684 } |
|
1685 } |
|
1686 |
|
1687 /** |
|
1688 * Spliterator for long streams. |
|
1689 */ |
|
1690 static class RandomLongsSpliterator extends RandomSupport.RandomSpliterator implements Spliterator.OfLong { |
|
1691 final ArbitrarilyJumpableGenerator generatingGenerator; |
|
1692 final long origin; |
|
1693 final long bound; |
|
1694 |
|
1695 RandomLongsSpliterator(ArbitrarilyJumpableGenerator generatingGenerator, long index, long fence, long origin, long bound) { |
|
1696 super(index, fence); |
|
1697 this.generatingGenerator = generatingGenerator; |
|
1698 this.origin = origin; this.bound = bound; |
|
1699 } |
|
1700 |
|
1701 public Spliterator.OfLong trySplit() { |
|
1702 long i = index, delta = Long.highestOneBit((fence - i) - 1), m = i + delta; |
|
1703 if (m <= i) return null; |
|
1704 index = m; |
|
1705 ArbitrarilyJumpableGenerator r = generatingGenerator; |
|
1706 return new RandomLongsSpliterator(r.copyAndJump((double)delta), i, m, origin, bound); |
|
1707 } |
|
1708 |
|
1709 public boolean tryAdvance(LongConsumer consumer) { |
|
1710 if (consumer == null) throw new NullPointerException(); |
|
1711 long i = index, f = fence; |
|
1712 if (i < f) { |
|
1713 consumer.accept(RandomSupport.boundedNextLong(generatingGenerator, origin, bound)); |
|
1714 index = i + 1; |
|
1715 return true; |
|
1716 } |
|
1717 else return false; |
|
1718 } |
|
1719 |
|
1720 public void forEachRemaining(LongConsumer consumer) { |
|
1721 if (consumer == null) throw new NullPointerException(); |
|
1722 long i = index, f = fence; |
|
1723 if (i < f) { |
|
1724 index = f; |
|
1725 ArbitrarilyJumpableGenerator r = generatingGenerator; |
|
1726 long o = origin, b = bound; |
|
1727 do { |
|
1728 consumer.accept(RandomSupport.boundedNextLong(r, o, b)); |
|
1729 } while (++i < f); |
|
1730 } |
|
1731 } |
|
1732 } |
|
1733 |
|
1734 /** |
|
1735 * Spliterator for double streams. |
|
1736 */ |
|
1737 static class RandomDoublesSpliterator extends RandomSupport.RandomSpliterator implements Spliterator.OfDouble { |
|
1738 final ArbitrarilyJumpableGenerator generatingGenerator; |
|
1739 final double origin; |
|
1740 final double bound; |
|
1741 |
|
1742 RandomDoublesSpliterator(ArbitrarilyJumpableGenerator generatingGenerator, long index, long fence, double origin, double bound) { |
|
1743 super(index, fence); |
|
1744 this.generatingGenerator = generatingGenerator; |
|
1745 this.origin = origin; this.bound = bound; |
|
1746 } |
|
1747 |
|
1748 public Spliterator.OfDouble trySplit() { |
|
1749 |
|
1750 long i = index, delta = Long.highestOneBit((fence - i) - 1), m = i + delta; |
|
1751 if (m <= i) return null; |
|
1752 index = m; |
|
1753 ArbitrarilyJumpableGenerator r = generatingGenerator; |
|
1754 return new RandomDoublesSpliterator(r.copyAndJump((double)delta), i, m, origin, bound); |
|
1755 } |
|
1756 |
|
1757 public boolean tryAdvance(DoubleConsumer consumer) { |
|
1758 if (consumer == null) throw new NullPointerException(); |
|
1759 long i = index, f = fence; |
|
1760 if (i < f) { |
|
1761 consumer.accept(RandomSupport.boundedNextDouble(generatingGenerator, origin, bound)); |
|
1762 index = i + 1; |
|
1763 return true; |
|
1764 } |
|
1765 else return false; |
|
1766 } |
|
1767 |
|
1768 public void forEachRemaining(DoubleConsumer consumer) { |
|
1769 if (consumer == null) throw new NullPointerException(); |
|
1770 long i = index, f = fence; |
|
1771 if (i < f) { |
|
1772 index = f; |
|
1773 ArbitrarilyJumpableGenerator r = generatingGenerator; |
|
1774 double o = origin, b = bound; |
|
1775 do { |
|
1776 consumer.accept(RandomSupport.boundedNextDouble(r, o, b)); |
|
1777 } while (++i < f); |
|
1778 } |
|
1779 } |
|
1780 } |
|
1781 |
|
1782 // Spliterators for producing new generators by jumping or leaping. The |
|
1783 // complete implementation of each of these spliterators is right here. |
|
1784 // In the same manner as for the preceding spliterators, the method trySplit() is |
|
1785 // coded to optimize execution speed: instead of dividing a range |
|
1786 // in half, it breaks off the largest possible chunk whose |
|
1787 // size is a power of two such that the remaining chunk is not |
|
1788 // empty. In this way, the necessary jump distances will tend to be |
|
1789 // powers of two. |
|
1790 |
|
1791 /** |
|
1792 * Spliterator for stream of generators of type RandomGenerator produced by jumps. |
|
1793 */ |
|
1794 static class RandomJumpsSpliterator extends RandomSupport.RandomSpliterator implements Spliterator<RandomGenerator> { |
|
1795 ArbitrarilyJumpableGenerator generatingGenerator; |
|
1796 final double distance; |
|
1797 |
|
1798 RandomJumpsSpliterator(ArbitrarilyJumpableGenerator generatingGenerator, long index, long fence, double distance) { |
|
1799 super(index, fence); |
|
1800 this.generatingGenerator = generatingGenerator; this.distance = distance; |
|
1801 } |
|
1802 |
|
1803 public Spliterator<RandomGenerator> trySplit() { |
|
1804 long i = index, delta = Long.highestOneBit((fence - i) - 1), m = i + delta; |
|
1805 if (m <= i) return null; |
|
1806 index = m; |
|
1807 ArbitrarilyJumpableGenerator r = generatingGenerator; |
|
1808 // Because delta is a power of two, (distance * (double)delta) can always be computed exactly. |
|
1809 return new RandomJumpsSpliterator(r.copyAndJump(distance * (double)delta), i, m, distance); |
|
1810 } |
|
1811 |
|
1812 public boolean tryAdvance(Consumer<? super RandomGenerator> consumer) { |
|
1813 if (consumer == null) throw new NullPointerException(); |
|
1814 long i = index, f = fence; |
|
1815 if (i < f) { |
|
1816 consumer.accept(generatingGenerator.copyAndJump(distance)); |
|
1817 index = i + 1; |
|
1818 return true; |
|
1819 } |
|
1820 return false; |
|
1821 } |
|
1822 |
|
1823 public void forEachRemaining(Consumer<? super RandomGenerator> consumer) { |
|
1824 if (consumer == null) throw new NullPointerException(); |
|
1825 long i = index, f = fence; |
|
1826 if (i < f) { |
|
1827 index = f; |
|
1828 ArbitrarilyJumpableGenerator r = generatingGenerator; |
|
1829 do { |
|
1830 consumer.accept(r.copyAndJump(distance)); |
|
1831 } while (++i < f); |
|
1832 } |
|
1833 } |
|
1834 } |
|
1835 |
|
1836 /** |
|
1837 * Spliterator for stream of generators of type RandomGenerator produced by leaps. |
|
1838 */ |
|
1839 static class RandomLeapsSpliterator extends RandomSupport.RandomSpliterator implements Spliterator<JumpableGenerator> { |
|
1840 ArbitrarilyJumpableGenerator generatingGenerator; |
|
1841 final double distance; |
|
1842 |
|
1843 RandomLeapsSpliterator(ArbitrarilyJumpableGenerator generatingGenerator, long index, long fence, double distance) { |
|
1844 super(index, fence); |
|
1845 this.generatingGenerator = generatingGenerator; this.distance = distance; |
|
1846 } |
|
1847 |
|
1848 public Spliterator<JumpableGenerator> trySplit() { |
|
1849 long i = index, delta = Long.highestOneBit((fence - i) - 1), m = i + delta; |
|
1850 if (m <= i) return null; |
|
1851 index = m; |
|
1852 // Because delta is a power of two, (distance * (double)delta) can always be computed exactly. |
|
1853 return new RandomLeapsSpliterator(generatingGenerator.copyAndJump(distance * (double)delta), i, m, distance); |
|
1854 } |
|
1855 |
|
1856 public boolean tryAdvance(Consumer<? super JumpableGenerator> consumer) { |
|
1857 if (consumer == null) throw new NullPointerException(); |
|
1858 long i = index, f = fence; |
|
1859 if (i < f) { |
|
1860 consumer.accept(generatingGenerator.copyAndJump(distance)); |
|
1861 index = i + 1; |
|
1862 return true; |
|
1863 } |
|
1864 return false; |
|
1865 } |
|
1866 |
|
1867 public void forEachRemaining(Consumer<? super JumpableGenerator> consumer) { |
|
1868 if (consumer == null) throw new NullPointerException(); |
|
1869 long i = index, f = fence; |
|
1870 if (i < f) { |
|
1871 index = f; |
|
1872 ArbitrarilyJumpableGenerator r = generatingGenerator; |
|
1873 do { |
|
1874 consumer.accept(r.copyAndJump(distance)); |
|
1875 } while (++i < f); |
|
1876 } |
|
1877 } |
|
1878 } |
|
1879 |
|
1880 /** |
|
1881 * Spliterator for stream of generators of type RandomGenerator produced by arbitrary jumps. |
|
1882 */ |
|
1883 static class RandomArbitraryJumpsSpliterator extends RandomSupport.RandomSpliterator implements Spliterator<ArbitrarilyJumpableGenerator> { |
|
1884 ArbitrarilyJumpableGenerator generatingGenerator; |
|
1885 final double distance; |
|
1886 |
|
1887 RandomArbitraryJumpsSpliterator(ArbitrarilyJumpableGenerator generatingGenerator, long index, long fence, double distance) { |
|
1888 super(index, fence); |
|
1889 this.generatingGenerator = generatingGenerator; this.distance = distance; |
|
1890 } |
|
1891 |
|
1892 public Spliterator<ArbitrarilyJumpableGenerator> trySplit() { |
|
1893 long i = index, delta = Long.highestOneBit((fence - i) - 1), m = i + delta; |
|
1894 if (m <= i) return null; |
|
1895 index = m; |
|
1896 // Because delta is a power of two, (distance * (double)delta) can always be computed exactly. |
|
1897 return new RandomArbitraryJumpsSpliterator(generatingGenerator.copyAndJump(distance * (double)delta), i, m, distance); |
|
1898 } |
|
1899 |
|
1900 public boolean tryAdvance(Consumer<? super ArbitrarilyJumpableGenerator> consumer) { |
|
1901 if (consumer == null) throw new NullPointerException(); |
|
1902 long i = index, f = fence; |
|
1903 if (i < f) { |
|
1904 consumer.accept(generatingGenerator.copyAndJump(distance)); |
|
1905 index = i + 1; |
|
1906 return true; |
|
1907 } |
|
1908 return false; |
|
1909 } |
|
1910 |
|
1911 public void forEachRemaining(Consumer<? super ArbitrarilyJumpableGenerator> consumer) { |
|
1912 if (consumer == null) throw new NullPointerException(); |
|
1913 long i = index, f = fence; |
|
1914 if (i < f) { |
|
1915 index = f; |
|
1916 ArbitrarilyJumpableGenerator r = generatingGenerator; |
|
1917 do { |
|
1918 consumer.accept(r.copyAndJump(distance)); |
|
1919 } while (++i < f); |
|
1920 } |
|
1921 } |
|
1922 } |
|
1923 |
|
1924 } |
|
1925 |
|
1926 /** |
|
1927 * This class provides much of the implementation of the {@link SplittableGenerator} interface, to |
|
1928 * minimize the effort required to implement this interface. |
|
1929 * <p> |
|
1930 * To implement a pseudorandom number generator, the programmer needs only to extend this class and |
|
1931 * provide implementations for the methods {@code nextInt()}, {@code nextLong()}, {@code period()}, |
|
1932 * and {@code split(SplittableGenerator)}. |
|
1933 * <p> |
|
1934 * (If the pseudorandom number generator also has the ability to jump an arbitrary |
|
1935 * specified distance, then the programmer may wish to consider instead extending the |
|
1936 * class {@link AbstractArbitrarilyJumpableGenerator}. See also the class |
|
1937 * {@link AbstractSplittableWithBrineGenerator}.) |
|
1938 * <p> |
|
1939 * The programmer should generally provide at least three constructors: one that takes no arguments, |
|
1940 * one that accepts a {@code long} seed value, and one that accepts an array of seed {@code byte} |
|
1941 * values. This class provides a public {@code initialSeed()} method that may be useful in |
|
1942 * initializing some static state from which to derive defaults seeds for use by the no-argument |
|
1943 * constructor. |
|
1944 * <p> |
|
1945 * For the stream methods (such as {@code ints()} and {@code splits()}), this class provides |
|
1946 * {@link Spliterator}-based implementations that allow parallel execution when appropriate. |
|
1947 * <p> |
|
1948 * The documentation for each non-abstract method in this class describes its implementation in |
|
1949 * detail. Each of these methods may be overridden if the pseudorandom number generator being |
|
1950 * implemented admits a more efficient implementation. |
|
1951 * |
|
1952 * @since 14 |
|
1953 */ |
|
1954 public abstract static class AbstractSplittableGenerator extends AbstractSpliteratorGenerator implements SplittableGenerator { |
|
1955 |
|
1956 /* |
|
1957 * Implementation Overview. |
|
1958 * |
|
1959 * This class provides most of the "user API" methods needed to |
|
1960 * satisfy the interface SplittableGenerator. Most of these methods |
|
1961 * are in turn inherited from AbstractGenerator and the non-public class |
|
1962 * AbstractSpliteratorGenerator; this class provides two versions of the |
|
1963 * splits method and defines the spliterators necessary to support |
|
1964 * them. |
|
1965 * |
|
1966 * File organization: First the non-public methods needed by the class |
|
1967 * AbstractSpliteratorGenerator, then the main public methods, followed by some |
|
1968 * custom spliterator classes. |
|
1969 */ |
|
1970 |
|
1971 public Spliterator.OfInt makeIntsSpliterator(long index, long fence, int origin, int bound) { |
|
1972 return new RandomIntsSpliterator(this, index, fence, origin, bound); |
|
1973 } |
|
1974 |
|
1975 public Spliterator.OfLong makeLongsSpliterator(long index, long fence, long origin, long bound) { |
|
1976 return new RandomLongsSpliterator(this, index, fence, origin, bound); |
|
1977 } |
|
1978 |
|
1979 public Spliterator.OfDouble makeDoublesSpliterator(long index, long fence, double origin, double bound) { |
|
1980 return new RandomDoublesSpliterator(this, index, fence, origin, bound); |
|
1981 } |
|
1982 |
|
1983 Spliterator<SplittableGenerator> makeSplitsSpliterator(long index, long fence, SplittableGenerator source) { |
|
1984 return new RandomSplitsSpliterator(source, index, fence, this); |
|
1985 } |
|
1986 |
|
1987 /* ---------------- public methods ---------------- */ |
|
1988 |
|
1989 /** |
|
1990 * Implements the @code{split()} method as {@code this.split(this)}. |
|
1991 * |
|
1992 * @return the new {@link SplittableGenerator} instance |
|
1993 */ |
|
1994 public SplittableGenerator split() { |
|
1995 return this.split(this); |
|
1996 } |
|
1997 |
|
1998 // Stream methods for splittings |
|
1999 |
|
2000 /** |
|
2001 * Returns an effectively unlimited stream of new pseudorandom number generators, each of which |
|
2002 * implements the {@link SplittableGenerator} interface. |
|
2003 * <p> |
|
2004 * This pseudorandom number generator provides the entropy used to seed the new ones. |
|
2005 * |
|
2006 * @return a stream of {@link SplittableGenerator} objects |
|
2007 * |
|
2008 * @implNote This method is implemented to be equivalent to {@code splits(Long.MAX_VALUE)}. |
|
2009 */ |
|
2010 public Stream<SplittableGenerator> splits() { |
|
2011 return this.splits(Long.MAX_VALUE, this); |
|
2012 } |
|
2013 |
|
2014 /** |
|
2015 * Returns a stream producing the given {@code streamSize} number of new pseudorandom number |
|
2016 * generators, each of which implements the {@link SplittableGenerator} interface. |
|
2017 * <p> |
|
2018 * This pseudorandom number generator provides the entropy used to seed the new ones. |
|
2019 * |
|
2020 * @param streamSize the number of values to generate |
|
2021 * |
|
2022 * @return a stream of {@link SplittableGenerator} objects |
|
2023 * |
|
2024 * @throws IllegalArgumentException if {@code streamSize} is less than zero |
|
2025 */ |
|
2026 public Stream<SplittableGenerator> splits(long streamSize) { |
|
2027 return this.splits(streamSize, this); |
|
2028 } |
|
2029 |
|
2030 /** |
|
2031 * Returns an effectively unlimited stream of new pseudorandom number generators, each of which |
|
2032 * implements the {@link SplittableGenerator} interface. |
|
2033 * |
|
2034 * @param source a {@link SplittableGenerator} instance to be used instead of this one as a source of |
|
2035 * pseudorandom bits used to initialize the state of the new ones. |
|
2036 * |
|
2037 * @return a stream of {@link SplittableGenerator} objects |
|
2038 * |
|
2039 * @implNote This method is implemented to be equivalent to {@code splits(Long.MAX_VALUE)}. |
|
2040 */ |
|
2041 public Stream<SplittableGenerator> splits(SplittableGenerator source) { |
|
2042 return this.splits(Long.MAX_VALUE, source); |
|
2043 } |
|
2044 |
|
2045 /** |
|
2046 * Returns a stream producing the given {@code streamSize} number of new pseudorandom number |
|
2047 * generators, each of which implements the {@link SplittableGenerator} interface. |
|
2048 * |
|
2049 * @param streamSize the number of values to generate |
|
2050 * @param source a {@link SplittableGenerator} instance to be used instead of this one as a source |
|
2051 * of pseudorandom bits used to initialize the state of the new ones. |
|
2052 * |
|
2053 * @return a stream of {@link SplittableGenerator} objects |
|
2054 * |
|
2055 * @throws IllegalArgumentException if {@code streamSize} is less than zero |
|
2056 */ |
|
2057 public Stream<SplittableGenerator> splits(long streamSize, SplittableGenerator source) { |
|
2058 RandomSupport.checkStreamSize(streamSize); |
|
2059 return StreamSupport.stream(makeSplitsSpliterator(0L, streamSize, source), false); |
|
2060 } |
|
2061 |
|
2062 /** |
|
2063 * Spliterator for int streams. We multiplex the four int versions into one class by treating a |
|
2064 * bound less than origin as unbounded, and also by treating "infinite" as equivalent to |
|
2065 * {@code Long.MAX_VALUE}. For splits, it uses the standard divide-by-two approach. The long and |
|
2066 * double versions of this class are identical except for types. |
|
2067 */ |
|
2068 static class RandomIntsSpliterator extends RandomSupport.RandomSpliterator implements Spliterator.OfInt { |
|
2069 final SplittableGenerator generatingGenerator; |
|
2070 final int origin; |
|
2071 final int bound; |
|
2072 |
|
2073 RandomIntsSpliterator(SplittableGenerator generatingGenerator, long index, long fence, int origin, int bound) { |
|
2074 super(index, fence); |
|
2075 this.generatingGenerator = generatingGenerator; |
|
2076 this.origin = origin; this.bound = bound; |
|
2077 } |
|
2078 |
|
2079 public Spliterator.OfInt trySplit() { |
|
2080 long i = index, m = (i + fence) >>> 1; |
|
2081 if (m <= i) return null; |
|
2082 index = m; |
|
2083 return new RandomIntsSpliterator(generatingGenerator.split(), i, m, origin, bound); |
|
2084 } |
|
2085 |
|
2086 public boolean tryAdvance(IntConsumer consumer) { |
|
2087 if (consumer == null) throw new NullPointerException(); |
|
2088 long i = index, f = fence; |
|
2089 if (i < f) { |
|
2090 consumer.accept(RandomSupport.boundedNextInt(generatingGenerator, origin, bound)); |
|
2091 index = i + 1; |
|
2092 return true; |
|
2093 } |
|
2094 else return false; |
|
2095 } |
|
2096 |
|
2097 public void forEachRemaining(IntConsumer consumer) { |
|
2098 if (consumer == null) throw new NullPointerException(); |
|
2099 long i = index, f = fence; |
|
2100 if (i < f) { |
|
2101 index = f; |
|
2102 RandomGenerator r = generatingGenerator; |
|
2103 int o = origin, b = bound; |
|
2104 do { |
|
2105 consumer.accept(RandomSupport.boundedNextInt(r, o, b)); |
|
2106 } while (++i < f); |
|
2107 } |
|
2108 } |
|
2109 } |
|
2110 |
|
2111 /** |
|
2112 * Spliterator for long streams. |
|
2113 */ |
|
2114 static class RandomLongsSpliterator extends RandomSupport.RandomSpliterator implements Spliterator.OfLong { |
|
2115 final SplittableGenerator generatingGenerator; |
|
2116 final long origin; |
|
2117 final long bound; |
|
2118 |
|
2119 RandomLongsSpliterator(SplittableGenerator generatingGenerator, long index, long fence, long origin, long bound) { |
|
2120 super(index, fence); |
|
2121 this.generatingGenerator = generatingGenerator; |
|
2122 this.origin = origin; this.bound = bound; |
|
2123 } |
|
2124 |
|
2125 public Spliterator.OfLong trySplit() { |
|
2126 long i = index, m = (i + fence) >>> 1; |
|
2127 if (m <= i) return null; |
|
2128 index = m; |
|
2129 return new RandomLongsSpliterator(generatingGenerator.split(), i, m, origin, bound); |
|
2130 } |
|
2131 |
|
2132 public boolean tryAdvance(LongConsumer consumer) { |
|
2133 if (consumer == null) throw new NullPointerException(); |
|
2134 long i = index, f = fence; |
|
2135 if (i < f) { |
|
2136 consumer.accept(RandomSupport.boundedNextLong(generatingGenerator, origin, bound)); |
|
2137 index = i + 1; |
|
2138 return true; |
|
2139 } |
|
2140 else return false; |
|
2141 } |
|
2142 |
|
2143 public void forEachRemaining(LongConsumer consumer) { |
|
2144 if (consumer == null) throw new NullPointerException(); |
|
2145 long i = index, f = fence; |
|
2146 if (i < f) { |
|
2147 index = f; |
|
2148 RandomGenerator r = generatingGenerator; |
|
2149 long o = origin, b = bound; |
|
2150 do { |
|
2151 consumer.accept(RandomSupport.boundedNextLong(r, o, b)); |
|
2152 } while (++i < f); |
|
2153 } |
|
2154 } |
|
2155 } |
|
2156 |
|
2157 /** |
|
2158 * Spliterator for double streams. |
|
2159 */ |
|
2160 static class RandomDoublesSpliterator extends RandomSupport.RandomSpliterator implements Spliterator.OfDouble { |
|
2161 final SplittableGenerator generatingGenerator; |
|
2162 final double origin; |
|
2163 final double bound; |
|
2164 |
|
2165 RandomDoublesSpliterator(SplittableGenerator generatingGenerator, long index, long fence, double origin, double bound) { |
|
2166 super(index, fence); |
|
2167 this.generatingGenerator = generatingGenerator; |
|
2168 this.origin = origin; this.bound = bound; |
|
2169 } |
|
2170 |
|
2171 public Spliterator.OfDouble trySplit() { |
|
2172 long i = index, m = (i + fence) >>> 1; |
|
2173 if (m <= i) return null; |
|
2174 index = m; |
|
2175 return new RandomDoublesSpliterator(generatingGenerator.split(), i, m, origin, bound); |
|
2176 } |
|
2177 |
|
2178 public boolean tryAdvance(DoubleConsumer consumer) { |
|
2179 if (consumer == null) throw new NullPointerException(); |
|
2180 long i = index, f = fence; |
|
2181 if (i < f) { |
|
2182 consumer.accept(RandomSupport.boundedNextDouble(generatingGenerator, origin, bound)); |
|
2183 index = i + 1; |
|
2184 return true; |
|
2185 } |
|
2186 else return false; |
|
2187 } |
|
2188 |
|
2189 public void forEachRemaining(DoubleConsumer consumer) { |
|
2190 if (consumer == null) throw new NullPointerException(); |
|
2191 long i = index, f = fence; |
|
2192 if (i < f) { |
|
2193 index = f; |
|
2194 RandomGenerator r = generatingGenerator; |
|
2195 double o = origin, b = bound; |
|
2196 do { |
|
2197 consumer.accept(RandomSupport.boundedNextDouble(r, o, b)); |
|
2198 } while (++i < f); |
|
2199 } |
|
2200 } |
|
2201 } |
|
2202 |
|
2203 /** |
|
2204 * Spliterator for stream of generators of type SplittableGenerator. We multiplex the two |
|
2205 * versions into one class by treating "infinite" as equivalent to Long.MAX_VALUE. |
|
2206 * For splits, it uses the standard divide-by-two approach. |
|
2207 */ |
|
2208 static class RandomSplitsSpliterator extends RandomSpliterator implements Spliterator<SplittableGenerator> { |
|
2209 final SplittableGenerator generatingGenerator; |
|
2210 final SplittableGenerator constructingGenerator; |
|
2211 |
|
2212 RandomSplitsSpliterator(SplittableGenerator generatingGenerator, |
|
2213 long index, long fence, |
|
2214 SplittableGenerator constructingGenerator) { |
|
2215 super(index, fence); |
|
2216 this.generatingGenerator = generatingGenerator; |
|
2217 this.constructingGenerator = constructingGenerator; |
|
2218 } |
|
2219 |
|
2220 public Spliterator<SplittableGenerator> trySplit() { |
|
2221 long i = index, m = (i + fence) >>> 1; |
|
2222 if (m <= i) return null; |
|
2223 index = m; |
|
2224 return new RandomSplitsSpliterator(generatingGenerator.split(), i, m, constructingGenerator); |
|
2225 } |
|
2226 |
|
2227 public boolean tryAdvance(Consumer<? super SplittableGenerator> consumer) { |
|
2228 if (consumer == null) throw new NullPointerException(); |
|
2229 long i = index, f = fence; |
|
2230 if (i < f) { |
|
2231 consumer.accept(constructingGenerator.split(generatingGenerator)); |
|
2232 index = i + 1; |
|
2233 return true; |
|
2234 } |
|
2235 else return false; |
|
2236 } |
|
2237 |
|
2238 public void forEachRemaining(Consumer<? super SplittableGenerator> consumer) { |
|
2239 if (consumer == null) throw new NullPointerException(); |
|
2240 long i = index, f = fence; |
|
2241 if (i < f) { |
|
2242 index = f; |
|
2243 SplittableGenerator c = constructingGenerator; |
|
2244 SplittableGenerator r = generatingGenerator; |
|
2245 do { |
|
2246 consumer.accept(c.split(r)); |
|
2247 } while (++i < f); |
|
2248 } |
|
2249 } |
|
2250 } |
|
2251 |
|
2252 } |
|
2253 |
|
2254 /** |
|
2255 * This class provides much of the implementation of the {@link SplittableGenerator} interface, to |
|
2256 * minimize the effort required to implement this interface. It is similar to the class |
|
2257 * {@link AbstractSplittableGenerator} but makes use of the brine technique for ensuring that |
|
2258 * distinct generators created by a single call to a {@code splits} method have distinct state cycles. |
|
2259 * <p> |
|
2260 * To implement a pseudorandom number generator, the programmer needs only to extend this class and |
|
2261 * provide implementations for the methods {@code nextInt()}, {@code nextLong()}, {@code period()}, |
|
2262 * and {@code split(SplittableGenerator, long)}. |
|
2263 * <p> |
|
2264 * The programmer should generally provide at least three constructors: one that takes no arguments, |
|
2265 * one that accepts a {@code long} seed value, and one that accepts an array of seed {@code byte} |
|
2266 * values. This class provides a public {@code initialSeed()} method that may be useful in |
|
2267 * initializing some static state from which to derive defaults seeds for use by the no-argument |
|
2268 * constructor. |
|
2269 * <p> |
|
2270 * For the stream methods (such as {@code ints()} and {@code splits()}), this class provides |
|
2271 * {@link Spliterator}-based implementations that allow parallel execution when appropriate. |
|
2272 * <p> |
|
2273 * The documentation for each non-abstract method in this class describes its implementation in |
|
2274 * detail. Each of these methods may be overridden if the pseudorandom number generator being |
|
2275 * implemented admits a more efficient implementation. |
|
2276 * |
|
2277 * @since 14 |
|
2278 */ |
|
2279 public abstract static class AbstractSplittableWithBrineGenerator |
|
2280 extends AbstractSplittableGenerator { |
|
2281 |
|
2282 /* |
|
2283 * Implementation Overview. |
|
2284 * |
|
2285 * This class provides most of the "user API" methods needed to |
|
2286 * satisfy the interface SplittableGenerator. Most of these methods |
|
2287 * are in turn inherited from AbstractSplittableGenerator and the non-public class |
|
2288 * AbstractSpliteratorGenerator; this class provides four versions of the |
|
2289 * splits method and defines the spliterators necessary to support |
|
2290 * them. |
|
2291 * |
|
2292 * File organization: First the non-public methods needed by the class |
|
2293 * AbstractSplittableWithBrineGenerator, then the main public methods, |
|
2294 * followed by some custom spliterator classes needed for stream methods. |
|
2295 */ |
|
2296 |
|
2297 // The salt consists groups of bits each SALT_SHIFT in size, starting from |
|
2298 // the left-hand (high-order) end of the word. We can regard them as |
|
2299 // digits base (1 << SALT_SHIFT). If SALT_SHIFT does not divide 64 |
|
2300 // evenly, then any leftover bits at the low end of the word are zero. |
|
2301 // The lowest digit of the salt is set to the largest possible digit |
|
2302 // (all 1-bits, or ((1 << SALT_SHIFT) - 1)); all other digits are set |
|
2303 // to a randomly chosen value less than that largest possible digit. |
|
2304 // The salt may be shifted left by SALT_SHIFT any number of times. |
|
2305 // If any salt remains in the word, its right-hand end can be identified |
|
2306 // by searching from left to right for an occurrence of a digit that is |
|
2307 // all 1-bits (not that we ever do that; this is simply a proof that one |
|
2308 // can identify the boundary between the salt and the index if any salt |
|
2309 // remains in the word). The idea is that before computing the bitwise OR |
|
2310 // of an index and the salt, one can first check to see whether the |
|
2311 // bitwise AND is nonzero; if so, one can shift the salt left by |
|
2312 // SALT_SHIFT and try again. In this way, when the bitwise OR is |
|
2313 // computed, if the salt is nonzero then its rightmost 1-bit is to the |
|
2314 // left of the leftmost 1-bit of the index. |
|
2315 |
|
2316 // We need 2 <= SALT_SHIFT <= 63 (3 through 8 are good values; 4 is probably best) |
|
2317 static final int SALT_SHIFT = 4; |
|
2318 |
|
2319 // Methods required by class AbstractSpliteratorGenerator (override) |
|
2320 Spliterator<SplittableGenerator> makeSplitsSpliterator(long index, long fence, SplittableGenerator source) { |
|
2321 // This little algorithm to generate a new salt value is carefully |
|
2322 // designed to work even if SALT_SHIFT does not evenly divide 64 |
|
2323 // (the number of bits in a long value). |
|
2324 long bits = nextLong(); |
|
2325 long multiplier = (1 << SALT_SHIFT) - 1; |
|
2326 long salt = multiplier << (64 - SALT_SHIFT); |
|
2327 while ((salt & multiplier) != 0) { |
|
2328 long digit = Math.multiplyHigh(bits, multiplier); |
|
2329 salt = (salt >>> SALT_SHIFT) | (digit << (64 - SALT_SHIFT)); |
|
2330 bits *= multiplier; |
|
2331 } |
|
2332 // This is the point at which newly generated salt gets injected into |
|
2333 // the root of a newly created brine-generating splits-spliterator. |
|
2334 return new RandomSplitsSpliteratorWithSalt(source, index, fence, this, salt); |
|
2335 } |
|
2336 |
|
2337 /* ---------------- public methods ---------------- */ |
|
2338 |
|
2339 // Stream methods for splitting |
|
2340 |
|
2341 /** |
|
2342 * Constructs and returns a new instance of {@code AbstractSplittableWithBrineGenerator} |
|
2343 * that shares no mutable state with this instance. However, with very high |
|
2344 * probability, the set of values collectively generated by the two objects |
|
2345 * should have the same statistical properties as if the same quantity of |
|
2346 * values were generated by a single thread using a single may be |
|
2347 * {@code AbstractSplittableWithBrineGenerator} object. Either or both of the two objects |
|
2348 * further split using the {@code split()} method, and the same expected |
|
2349 * statistical properties apply to the entire set of generators constructed |
|
2350 * by such recursive splitting. |
|
2351 * |
|
2352 * @param brine a long value, of which the low 63 bits provide a unique id |
|
2353 * among calls to this method for constructing a single series of Generator objects. |
|
2354 * |
|
2355 * @return the new {@code AbstractSplittableWithBrineGenerator} instance |
|
2356 */ |
|
2357 public SplittableGenerator split(long brine) { |
|
2358 return this.split(this, brine); |
|
2359 } |
|
2360 |
|
2361 /** |
|
2362 * Constructs and returns a new instance of {@code L64X128MixRandom} |
|
2363 * that shares no mutable state with this instance. |
|
2364 * However, with very high probability, the set of values collectively |
|
2365 * generated by the two objects has the same statistical properties as if |
|
2366 * same the quantity of values were generated by a single thread using |
|
2367 * a single {@code L64X128MixRandom} object. Either or both of the two |
|
2368 * objects may be further split using the {@code split} method, |
|
2369 * and the same expected statistical properties apply to the |
|
2370 * entire set of generators constructed by such recursive splitting. |
|
2371 * |
|
2372 * @param source a {@code SplittableGenerator} instance to be used instead |
|
2373 * of this one as a source of pseudorandom bits used to |
|
2374 * initialize the state of the new ones. |
|
2375 * @return a new instance of {@code L64X128MixRandom} |
|
2376 */ |
|
2377 public SplittableGenerator split(SplittableGenerator source) { |
|
2378 // It's a one-off: supply randomly chosen brine |
|
2379 return this.split(source, source.nextLong()); |
|
2380 } |
|
2381 |
|
2382 /** |
|
2383 * Constructs and returns a new instance of {@code AbstractSplittableWithBrineGenerator} |
|
2384 * that shares no mutable state with this instance. However, with very high |
|
2385 * probability, the set of values collectively generated by the two objects |
|
2386 * should have the same statistical properties as if the same quantity of |
|
2387 * values were generated by a single thread using a single may be |
|
2388 * {@code AbstractSplittableWithBrineGenerator} object. Either or both of the two objects |
|
2389 * further split using the {@code split()} method, and the same expected |
|
2390 * statistical properties apply to the entire set of generators constructed |
|
2391 * by such recursive splitting. |
|
2392 * |
|
2393 * @param source a {@code SplittableGenerator} instance to be used instead |
|
2394 * of this one as a source of pseudorandom bits used to |
|
2395 * initialize the state of the new ones. |
|
2396 * @param brine a long value, of which the low 63 bits provide a unique id |
|
2397 * among calls to this method for constructing a single series of |
|
2398 * {@code RandomGenerator} objects. |
|
2399 * |
|
2400 * @return the new {@code AbstractSplittableWithBrineGenerator} instance |
|
2401 */ |
|
2402 public abstract SplittableGenerator split(SplittableGenerator source, long brine); |
|
2403 |
|
2404 |
|
2405 /* ---------------- spliterator ---------------- */ |
|
2406 /** |
|
2407 * Alternate spliterator for stream of generators of type SplittableGenerator. We multiplex |
|
2408 * the two versions into one class by treating "infinite" as equivalent to Long.MAX_VALUE. |
|
2409 * For splits, it uses the standard divide-by-two approach. |
|
2410 * |
|
2411 * This differs from {@code SplittableGenerator.RandomSplitsSpliterator} in that it provides |
|
2412 * a brine argument (a mixture of salt and an index) when calling the {@code split} method. |
|
2413 */ |
|
2414 static class RandomSplitsSpliteratorWithSalt |
|
2415 extends RandomSpliterator implements Spliterator<SplittableGenerator> { |
|
2416 |
|
2417 final SplittableGenerator generatingGenerator; |
|
2418 final AbstractSplittableWithBrineGenerator constructingGenerator; |
|
2419 long salt; |
|
2420 |
|
2421 // Important invariant: 0 <= index <= fence |
|
2422 |
|
2423 // Important invariant: if salt and index are both nonzero, |
|
2424 // the rightmost 1-bit of salt is to the left of the leftmost 1-bit of index. |
|
2425 // If necessary, the salt can be leftshifted by SALT_SHIFT as many times as |
|
2426 // necessary to maintain the invariant. |
|
2427 |
|
2428 RandomSplitsSpliteratorWithSalt(SplittableGenerator generatingGenerator, long index, long fence, |
|
2429 AbstractSplittableWithBrineGenerator constructingGenerator, long salt) { |
|
2430 super(index, fence); |
|
2431 this.generatingGenerator = generatingGenerator; |
|
2432 this.constructingGenerator = constructingGenerator; |
|
2433 while ((salt != 0) && (Long.compareUnsigned(salt & -salt, index) <= 0)) { |
|
2434 salt = salt << SALT_SHIFT; |
|
2435 } |
|
2436 this.salt = salt; |
|
2437 } |
|
2438 |
|
2439 public Spliterator<SplittableGenerator> trySplit() { |
|
2440 long i = index, m = (i + fence) >>> 1; |
|
2441 if (m <= i) return null; |
|
2442 RandomSplitsSpliteratorWithSalt result = |
|
2443 new RandomSplitsSpliteratorWithSalt(generatingGenerator.split(), i, m, constructingGenerator, salt); |
|
2444 index = m; |
|
2445 while ((salt != 0) && (Long.compareUnsigned(salt & -salt, index) <= 0)) { |
|
2446 salt = salt << SALT_SHIFT; |
|
2447 } |
|
2448 return result; |
|
2449 } |
|
2450 |
|
2451 public boolean tryAdvance(Consumer<? super SplittableGenerator> consumer) { |
|
2452 if (consumer == null) throw new NullPointerException(); |
|
2453 long i = index, f = fence; |
|
2454 if (i < f) { |
|
2455 consumer.accept(constructingGenerator.split(generatingGenerator, salt | i)); |
|
2456 ++i; |
|
2457 index = i; |
|
2458 if ((i & salt) != 0) salt <<= SALT_SHIFT; |
|
2459 return true; |
|
2460 } |
|
2461 return false; |
|
2462 } |
|
2463 |
|
2464 public void forEachRemaining(Consumer<? super SplittableGenerator> consumer) { |
|
2465 if (consumer == null) throw new NullPointerException(); |
|
2466 long i = index, f = fence; |
|
2467 if (i < f) { |
|
2468 index = f; |
|
2469 AbstractSplittableWithBrineGenerator c = constructingGenerator; |
|
2470 SplittableGenerator r = generatingGenerator; |
|
2471 do { |
|
2472 consumer.accept(c.split(r, salt | i)); |
|
2473 ++i; |
|
2474 if ((i & salt) != 0) salt <<= SALT_SHIFT; |
|
2475 } while (i < f); |
|
2476 } |
|
2477 } |
|
2478 } |
|
2479 |
|
2480 } |
|
2481 |
|
2482 } |