1 /* 2 * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package java.util; 27 28 import java.util.concurrent.atomic.AtomicLong; 29 import java.util.function.DoubleConsumer; 30 import java.util.function.IntConsumer; 31 import java.util.function.LongConsumer; 32 import java.util.stream.DoubleStream; 33 import java.util.stream.IntStream; 34 import java.util.stream.LongStream; 35 import java.util.stream.StreamSupport; 36 37 /** 38 * A generator of uniform pseudorandom values applicable for use in 39 * (among other contexts) isolated parallel computations that may 40 * generate subtasks. Class {@code SplittableRandom} supports methods for 41 * producing pseudorandom numbers of type {@code int}, {@code long}, 42 * and {@code double} with similar usages as for class 43 * {@link java.util.Random} but differs in the following ways: 44 * 45 * <ul> 46 * 47 * <li>Series of generated values pass the DieHarder suite testing 48 * independence and uniformity properties of random number generators. 49 * (Most recently validated with <a 50 * href="http://www.phy.duke.edu/~rgb/General/dieharder.php"> version 51 * 3.31.1</a>.) These tests validate only the methods for certain 52 * types and ranges, but similar properties are expected to hold, at 53 * least approximately, for others as well. The <em>period</em> 54 * (length of any series of generated values before it repeats) is at 55 * least 2<sup>64</sup>. 56 * 57 * <li>Method {@link #split} constructs and returns a new 58 * SplittableRandom instance that shares no mutable state with the 59 * current instance. However, with very high probability, the 60 * values collectively generated by the two objects have the same 61 * statistical properties as if the same quantity of values were 62 * generated by a single thread using a single {@code 63 * SplittableRandom} object. 64 * 65 * <li>Instances of SplittableRandom are <em>not</em> thread-safe. 66 * They are designed to be split, not shared, across threads. For 67 * example, a {@link java.util.concurrent.ForkJoinTask 68 * fork/join-style} computation using random numbers might include a 69 * construction of the form {@code new 70 * Subtask(aSplittableRandom.split()).fork()}. 71 * 72 * <li>This class provides additional methods for generating random 73 * streams, that employ the above techniques when used in {@code 74 * stream.parallel()} mode. 75 * 76 * </ul> 77 * 78 * <p>Instances of {@code SplittableRandom} are not cryptographically 79 * secure. Consider instead using {@link java.security.SecureRandom} 80 * in security-sensitive applications. Additionally, 81 * default-constructed instances do not use a cryptographically random 82 * seed unless the {@linkplain System#getProperty system property} 83 * {@code java.util.secureRandomSeed} is set to {@code true}. 84 * 85 * @author Guy Steele 86 * @author Doug Lea 87 * @since 1.8 88 */ 89 public final class SplittableRandom { 90 91 /* 92 * Implementation Overview. 93 * 94 * This algorithm was inspired by the "DotMix" algorithm by 95 * Leiserson, Schardl, and Sukha "Deterministic Parallel 96 * Random-Number Generation for Dynamic-Multithreading Platforms", 97 * PPoPP 2012, as well as those in "Parallel random numbers: as 98 * easy as 1, 2, 3" by Salmon, Morae, Dror, and Shaw, SC 2011. It 99 * differs mainly in simplifying and cheapening operations. 100 * 101 * The primary update step (method nextSeed()) is to add a 102 * constant ("gamma") to the current (64 bit) seed, forming a 103 * simple sequence. The seed and the gamma values for any two 104 * SplittableRandom instances are highly likely to be different. 105 * 106 * Methods nextLong, nextInt, and derivatives do not return the 107 * sequence (seed) values, but instead a hash-like bit-mix of 108 * their bits, producing more independently distributed sequences. 109 * For nextLong, the mix64 function is based on David Stafford's 110 * (http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html) 111 * "Mix13" variant of the "64-bit finalizer" function in Austin 112 * Appleby's MurmurHash3 algorithm (see 113 * http://code.google.com/p/smhasher/wiki/MurmurHash3). The mix32 114 * function is based on Stafford's Mix04 mix function, but returns 115 * the upper 32 bits cast as int. 116 * 117 * The split operation uses the current generator to form the seed 118 * and gamma for another SplittableRandom. To conservatively 119 * avoid potential correlations between seed and value generation, 120 * gamma selection (method mixGamma) uses different 121 * (Murmurhash3's) mix constants. To avoid potential weaknesses 122 * in bit-mixing transformations, we restrict gammas to odd values 123 * with at least 24 0-1 or 1-0 bit transitions. Rather than 124 * rejecting candidates with too few or too many bits set, method 125 * mixGamma flips some bits (which has the effect of mapping at 126 * most 4 to any given gamma value). This reduces the effective 127 * set of 64bit odd gamma values by about 2%, and serves as an 128 * automated screening for sequence constant selection that is 129 * left as an empirical decision in some other hashing and crypto 130 * algorithms. 131 * 132 * The resulting generator thus transforms a sequence in which 133 * (typically) many bits change on each step, with an inexpensive 134 * mixer with good (but less than cryptographically secure) 135 * avalanching. 136 * 137 * The default (no-argument) constructor, in essence, invokes 138 * split() for a common "defaultGen" SplittableRandom. Unlike 139 * other cases, this split must be performed in a thread-safe 140 * manner, so we use an AtomicLong to represent the seed rather 141 * than use an explicit SplittableRandom. To bootstrap the 142 * defaultGen, we start off using a seed based on current time 143 * unless the java.util.secureRandomSeed property is set. This 144 * serves as a slimmed-down (and insecure) variant of SecureRandom 145 * that also avoids stalls that may occur when using /dev/random. 146 * 147 * It is a relatively simple matter to apply the basic design here 148 * to use 128 bit seeds. However, emulating 128bit arithmetic and 149 * carrying around twice the state add more overhead than appears 150 * warranted for current usages. 151 * 152 * File organization: First the non-public methods that constitute 153 * the main algorithm, then the main public methods, followed by 154 * some custom spliterator classes needed for stream methods. 155 */ 156 157 /** 158 * The golden ratio scaled to 64bits, used as the initial gamma 159 * value for (unsplit) SplittableRandoms. 160 */ 161 private static final long GOLDEN_GAMMA = 0x9e3779b97f4a7c15L; 162 163 /** 164 * The least non-zero value returned by nextDouble(). This value 165 * is scaled by a random value of 53 bits to produce a result. 166 */ 167 private static final double DOUBLE_UNIT = 0x1.0p-53; // 1.0 / (1L << 53); 168 169 /** 170 * The seed. Updated only via method nextSeed. 171 */ 172 private long seed; 173 174 /** 175 * The step value. 176 */ 177 private final long gamma; 178 179 /** 180 * Internal constructor used by all others except default constructor. 181 */ SplittableRandom(long seed, long gamma)182 private SplittableRandom(long seed, long gamma) { 183 this.seed = seed; 184 this.gamma = gamma; 185 } 186 187 /** 188 * Computes Stafford variant 13 of 64bit mix function. 189 */ mix64(long z)190 private static long mix64(long z) { 191 z = (z ^ (z >>> 30)) * 0xbf58476d1ce4e5b9L; 192 z = (z ^ (z >>> 27)) * 0x94d049bb133111ebL; 193 return z ^ (z >>> 31); 194 } 195 196 /** 197 * Returns the 32 high bits of Stafford variant 4 mix64 function as int. 198 */ mix32(long z)199 private static int mix32(long z) { 200 z = (z ^ (z >>> 33)) * 0x62a9d9ed799705f5L; 201 return (int)(((z ^ (z >>> 28)) * 0xcb24d0a5c88c35b3L) >>> 32); 202 } 203 204 /** 205 * Returns the gamma value to use for a new split instance. 206 */ mixGamma(long z)207 private static long mixGamma(long z) { 208 z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL; // MurmurHash3 mix constants 209 z = (z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L; 210 z = (z ^ (z >>> 33)) | 1L; // force to be odd 211 int n = Long.bitCount(z ^ (z >>> 1)); // ensure enough transitions 212 return (n < 24) ? z ^ 0xaaaaaaaaaaaaaaaaL : z; 213 } 214 215 /** 216 * Adds gamma to seed. 217 */ nextSeed()218 private long nextSeed() { 219 return seed += gamma; 220 } 221 222 // IllegalArgumentException messages 223 static final String BAD_BOUND = "bound must be positive"; 224 static final String BAD_RANGE = "bound must be greater than origin"; 225 static final String BAD_SIZE = "size must be non-negative"; 226 227 /** 228 * The seed generator for default constructors. 229 */ 230 private static final AtomicLong defaultGen 231 = new AtomicLong(mix64(System.currentTimeMillis()) ^ 232 mix64(System.nanoTime())); 233 234 // at end of <clinit> to survive static initialization circularity 235 static { 236 if (java.security.AccessController.doPrivileged( 237 new java.security.PrivilegedAction<Boolean>() { 238 public Boolean run() { 239 return Boolean.getBoolean("java.util.secureRandomSeed"); 240 }})) { 241 byte[] seedBytes = java.security.SecureRandom.getSeed(8); 242 long s = (long)seedBytes[0] & 0xffL; 243 for (int i = 1; i < 8; ++i) 244 s = (s << 8) | ((long)seedBytes[i] & 0xffL); 245 defaultGen.set(s); 246 } 247 } 248 249 /* 250 * Internal versions of nextX methods used by streams, as well as 251 * the public nextX(origin, bound) methods. These exist mainly to 252 * avoid the need for multiple versions of stream spliterators 253 * across the different exported forms of streams. 254 */ 255 256 /** 257 * The form of nextLong used by LongStream Spliterators. If 258 * origin is greater than bound, acts as unbounded form of 259 * nextLong, else as bounded form. 260 * 261 * @param origin the least value, unless greater than bound 262 * @param bound the upper bound (exclusive), must not equal origin 263 * @return a pseudorandom value 264 */ internalNextLong(long origin, long bound)265 final long internalNextLong(long origin, long bound) { 266 /* 267 * Four Cases: 268 * 269 * 1. If the arguments indicate unbounded form, act as 270 * nextLong(). 271 * 272 * 2. If the range is an exact power of two, apply the 273 * associated bit mask. 274 * 275 * 3. If the range is positive, loop to avoid potential bias 276 * when the implicit nextLong() bound (2<sup>64</sup>) is not 277 * evenly divisible by the range. The loop rejects candidates 278 * computed from otherwise over-represented values. The 279 * expected number of iterations under an ideal generator 280 * varies from 1 to 2, depending on the bound. The loop itself 281 * takes an unlovable form. Because the first candidate is 282 * already available, we need a break-in-the-middle 283 * construction, which is concisely but cryptically performed 284 * within the while-condition of a body-less for loop. 285 * 286 * 4. Otherwise, the range cannot be represented as a positive 287 * long. The loop repeatedly generates unbounded longs until 288 * obtaining a candidate meeting constraints (with an expected 289 * number of iterations of less than two). 290 */ 291 292 long r = mix64(nextSeed()); 293 if (origin < bound) { 294 long n = bound - origin, m = n - 1; 295 if ((n & m) == 0L) // power of two 296 r = (r & m) + origin; 297 else if (n > 0L) { // reject over-represented candidates 298 for (long u = r >>> 1; // ensure nonnegative 299 u + m - (r = u % n) < 0L; // rejection check 300 u = mix64(nextSeed()) >>> 1) // retry 301 ; 302 r += origin; 303 } 304 else { // range not representable as long 305 while (r < origin || r >= bound) 306 r = mix64(nextSeed()); 307 } 308 } 309 return r; 310 } 311 312 /** 313 * The form of nextInt used by IntStream Spliterators. 314 * Exactly the same as long version, except for types. 315 * 316 * @param origin the least value, unless greater than bound 317 * @param bound the upper bound (exclusive), must not equal origin 318 * @return a pseudorandom value 319 */ internalNextInt(int origin, int bound)320 final int internalNextInt(int origin, int bound) { 321 int r = mix32(nextSeed()); 322 if (origin < bound) { 323 int n = bound - origin, m = n - 1; 324 if ((n & m) == 0) 325 r = (r & m) + origin; 326 else if (n > 0) { 327 for (int u = r >>> 1; 328 u + m - (r = u % n) < 0; 329 u = mix32(nextSeed()) >>> 1) 330 ; 331 r += origin; 332 } 333 else { 334 while (r < origin || r >= bound) 335 r = mix32(nextSeed()); 336 } 337 } 338 return r; 339 } 340 341 /** 342 * The form of nextDouble used by DoubleStream Spliterators. 343 * 344 * @param origin the least value, unless greater than bound 345 * @param bound the upper bound (exclusive), must not equal origin 346 * @return a pseudorandom value 347 */ internalNextDouble(double origin, double bound)348 final double internalNextDouble(double origin, double bound) { 349 double r = (nextLong() >>> 11) * DOUBLE_UNIT; 350 if (origin < bound) { 351 r = r * (bound - origin) + origin; 352 if (r >= bound) // correct for rounding 353 r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1); 354 } 355 return r; 356 } 357 358 /* ---------------- public methods ---------------- */ 359 360 /** 361 * Creates a new SplittableRandom instance using the specified 362 * initial seed. SplittableRandom instances created with the same 363 * seed in the same program generate identical sequences of values. 364 * 365 * @param seed the initial seed 366 */ SplittableRandom(long seed)367 public SplittableRandom(long seed) { 368 this(seed, GOLDEN_GAMMA); 369 } 370 371 /** 372 * Creates a new SplittableRandom instance that is likely to 373 * generate sequences of values that are statistically independent 374 * of those of any other instances in the current program; and 375 * may, and typically does, vary across program invocations. 376 */ SplittableRandom()377 public SplittableRandom() { // emulate defaultGen.split() 378 long s = defaultGen.getAndAdd(GOLDEN_GAMMA << 1); 379 this.seed = mix64(s); 380 this.gamma = mixGamma(s + GOLDEN_GAMMA); 381 } 382 383 /** 384 * Constructs and returns a new SplittableRandom instance that 385 * shares no mutable state with this instance. However, with very 386 * high probability, the set of values collectively generated by 387 * the two objects has the same statistical properties as if the 388 * same quantity of values were generated by a single thread using 389 * a single SplittableRandom object. Either or both of the two 390 * objects may be further split using the {@code split()} method, 391 * and the same expected statistical properties apply to the 392 * entire set of generators constructed by such recursive 393 * splitting. 394 * 395 * @return the new SplittableRandom instance 396 */ split()397 public SplittableRandom split() { 398 return new SplittableRandom(nextLong(), mixGamma(nextSeed())); 399 } 400 401 /** 402 * Fills a user-supplied byte array with generated pseudorandom bytes. 403 * 404 * @param bytes the byte array to fill with pseudorandom bytes 405 * @throws NullPointerException if bytes is null 406 * @since 10 407 */ nextBytes(byte[] bytes)408 public void nextBytes(byte[] bytes) { 409 int i = 0; 410 int len = bytes.length; 411 for (int words = len >> 3; words--> 0; ) { 412 long rnd = nextLong(); 413 for (int n = 8; n--> 0; rnd >>>= Byte.SIZE) 414 bytes[i++] = (byte)rnd; 415 } 416 if (i < len) 417 for (long rnd = nextLong(); i < len; rnd >>>= Byte.SIZE) 418 bytes[i++] = (byte)rnd; 419 } 420 421 /** 422 * Returns a pseudorandom {@code int} value. 423 * 424 * @return a pseudorandom {@code int} value 425 */ nextInt()426 public int nextInt() { 427 return mix32(nextSeed()); 428 } 429 430 /** 431 * Returns a pseudorandom {@code int} value between zero (inclusive) 432 * and the specified bound (exclusive). 433 * 434 * @param bound the upper bound (exclusive). Must be positive. 435 * @return a pseudorandom {@code int} value between zero 436 * (inclusive) and the bound (exclusive) 437 * @throws IllegalArgumentException if {@code bound} is not positive 438 */ nextInt(int bound)439 public int nextInt(int bound) { 440 if (bound <= 0) 441 throw new IllegalArgumentException(BAD_BOUND); 442 // Specialize internalNextInt for origin 0 443 int r = mix32(nextSeed()); 444 int m = bound - 1; 445 if ((bound & m) == 0) // power of two 446 r &= m; 447 else { // reject over-represented candidates 448 for (int u = r >>> 1; 449 u + m - (r = u % bound) < 0; 450 u = mix32(nextSeed()) >>> 1) 451 ; 452 } 453 return r; 454 } 455 456 /** 457 * Returns a pseudorandom {@code int} value between the specified 458 * origin (inclusive) and the specified bound (exclusive). 459 * 460 * @param origin the least value returned 461 * @param bound the upper bound (exclusive) 462 * @return a pseudorandom {@code int} value between the origin 463 * (inclusive) and the bound (exclusive) 464 * @throws IllegalArgumentException if {@code origin} is greater than 465 * or equal to {@code bound} 466 */ nextInt(int origin, int bound)467 public int nextInt(int origin, int bound) { 468 if (origin >= bound) 469 throw new IllegalArgumentException(BAD_RANGE); 470 return internalNextInt(origin, bound); 471 } 472 473 /** 474 * Returns a pseudorandom {@code long} value. 475 * 476 * @return a pseudorandom {@code long} value 477 */ nextLong()478 public long nextLong() { 479 return mix64(nextSeed()); 480 } 481 482 /** 483 * Returns a pseudorandom {@code long} value between zero (inclusive) 484 * and the specified bound (exclusive). 485 * 486 * @param bound the upper bound (exclusive). Must be positive. 487 * @return a pseudorandom {@code long} value between zero 488 * (inclusive) and the bound (exclusive) 489 * @throws IllegalArgumentException if {@code bound} is not positive 490 */ nextLong(long bound)491 public long nextLong(long bound) { 492 if (bound <= 0) 493 throw new IllegalArgumentException(BAD_BOUND); 494 // Specialize internalNextLong for origin 0 495 long r = mix64(nextSeed()); 496 long m = bound - 1; 497 if ((bound & m) == 0L) // power of two 498 r &= m; 499 else { // reject over-represented candidates 500 for (long u = r >>> 1; 501 u + m - (r = u % bound) < 0L; 502 u = mix64(nextSeed()) >>> 1) 503 ; 504 } 505 return r; 506 } 507 508 /** 509 * Returns a pseudorandom {@code long} value between the specified 510 * origin (inclusive) and the specified bound (exclusive). 511 * 512 * @param origin the least value returned 513 * @param bound the upper bound (exclusive) 514 * @return a pseudorandom {@code long} value between the origin 515 * (inclusive) and the bound (exclusive) 516 * @throws IllegalArgumentException if {@code origin} is greater than 517 * or equal to {@code bound} 518 */ nextLong(long origin, long bound)519 public long nextLong(long origin, long bound) { 520 if (origin >= bound) 521 throw new IllegalArgumentException(BAD_RANGE); 522 return internalNextLong(origin, bound); 523 } 524 525 /** 526 * Returns a pseudorandom {@code double} value between zero 527 * (inclusive) and one (exclusive). 528 * 529 * @return a pseudorandom {@code double} value between zero 530 * (inclusive) and one (exclusive) 531 */ nextDouble()532 public double nextDouble() { 533 return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT; 534 } 535 536 /** 537 * Returns a pseudorandom {@code double} value between 0.0 538 * (inclusive) and the specified bound (exclusive). 539 * 540 * @param bound the upper bound (exclusive). Must be positive. 541 * @return a pseudorandom {@code double} value between zero 542 * (inclusive) and the bound (exclusive) 543 * @throws IllegalArgumentException if {@code bound} is not positive 544 */ nextDouble(double bound)545 public double nextDouble(double bound) { 546 if (!(bound > 0.0)) 547 throw new IllegalArgumentException(BAD_BOUND); 548 double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound; 549 return (result < bound) ? result : // correct for rounding 550 Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1); 551 } 552 553 /** 554 * Returns a pseudorandom {@code double} value between the specified 555 * origin (inclusive) and bound (exclusive). 556 * 557 * @param origin the least value returned 558 * @param bound the upper bound (exclusive) 559 * @return a pseudorandom {@code double} value between the origin 560 * (inclusive) and the bound (exclusive) 561 * @throws IllegalArgumentException if {@code origin} is greater than 562 * or equal to {@code bound} 563 */ nextDouble(double origin, double bound)564 public double nextDouble(double origin, double bound) { 565 if (!(origin < bound)) 566 throw new IllegalArgumentException(BAD_RANGE); 567 return internalNextDouble(origin, bound); 568 } 569 570 /** 571 * Returns a pseudorandom {@code boolean} value. 572 * 573 * @return a pseudorandom {@code boolean} value 574 */ nextBoolean()575 public boolean nextBoolean() { 576 return mix32(nextSeed()) < 0; 577 } 578 579 // stream methods, coded in a way intended to better isolate for 580 // maintenance purposes the small differences across forms. 581 582 /** 583 * Returns a stream producing the given {@code streamSize} number 584 * of pseudorandom {@code int} values from this generator and/or 585 * one split from it. 586 * 587 * @param streamSize the number of values to generate 588 * @return a stream of pseudorandom {@code int} values 589 * @throws IllegalArgumentException if {@code streamSize} is 590 * less than zero 591 */ ints(long streamSize)592 public IntStream ints(long streamSize) { 593 if (streamSize < 0L) 594 throw new IllegalArgumentException(BAD_SIZE); 595 return StreamSupport.intStream 596 (new RandomIntsSpliterator 597 (this, 0L, streamSize, Integer.MAX_VALUE, 0), 598 false); 599 } 600 601 /** 602 * Returns an effectively unlimited stream of pseudorandom {@code int} 603 * values from this generator and/or one split from it. 604 * 605 * @implNote This method is implemented to be equivalent to {@code 606 * ints(Long.MAX_VALUE)}. 607 * 608 * @return a stream of pseudorandom {@code int} values 609 */ ints()610 public IntStream ints() { 611 return StreamSupport.intStream 612 (new RandomIntsSpliterator 613 (this, 0L, Long.MAX_VALUE, Integer.MAX_VALUE, 0), 614 false); 615 } 616 617 /** 618 * Returns a stream producing the given {@code streamSize} number 619 * of pseudorandom {@code int} values from this generator and/or one split 620 * from it; each value conforms to the given origin (inclusive) and bound 621 * (exclusive). 622 * 623 * @param streamSize the number of values to generate 624 * @param randomNumberOrigin the origin (inclusive) of each random value 625 * @param randomNumberBound the bound (exclusive) of each random value 626 * @return a stream of pseudorandom {@code int} values, 627 * each with the given origin (inclusive) and bound (exclusive) 628 * @throws IllegalArgumentException if {@code streamSize} is 629 * less than zero, or {@code randomNumberOrigin} 630 * is greater than or equal to {@code randomNumberBound} 631 */ ints(long streamSize, int randomNumberOrigin, int randomNumberBound)632 public IntStream ints(long streamSize, int randomNumberOrigin, 633 int randomNumberBound) { 634 if (streamSize < 0L) 635 throw new IllegalArgumentException(BAD_SIZE); 636 if (randomNumberOrigin >= randomNumberBound) 637 throw new IllegalArgumentException(BAD_RANGE); 638 return StreamSupport.intStream 639 (new RandomIntsSpliterator 640 (this, 0L, streamSize, randomNumberOrigin, randomNumberBound), 641 false); 642 } 643 644 /** 645 * Returns an effectively unlimited stream of pseudorandom {@code 646 * int} values from this generator and/or one split from it; each value 647 * conforms to the given origin (inclusive) and bound (exclusive). 648 * 649 * @implNote This method is implemented to be equivalent to {@code 650 * ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. 651 * 652 * @param randomNumberOrigin the origin (inclusive) of each random value 653 * @param randomNumberBound the bound (exclusive) of each random value 654 * @return a stream of pseudorandom {@code int} values, 655 * each with the given origin (inclusive) and bound (exclusive) 656 * @throws IllegalArgumentException if {@code randomNumberOrigin} 657 * is greater than or equal to {@code randomNumberBound} 658 */ ints(int randomNumberOrigin, int randomNumberBound)659 public IntStream ints(int randomNumberOrigin, int randomNumberBound) { 660 if (randomNumberOrigin >= randomNumberBound) 661 throw new IllegalArgumentException(BAD_RANGE); 662 return StreamSupport.intStream 663 (new RandomIntsSpliterator 664 (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), 665 false); 666 } 667 668 /** 669 * Returns a stream producing the given {@code streamSize} number 670 * of pseudorandom {@code long} values from this generator and/or 671 * one split from it. 672 * 673 * @param streamSize the number of values to generate 674 * @return a stream of pseudorandom {@code long} values 675 * @throws IllegalArgumentException if {@code streamSize} is 676 * less than zero 677 */ longs(long streamSize)678 public LongStream longs(long streamSize) { 679 if (streamSize < 0L) 680 throw new IllegalArgumentException(BAD_SIZE); 681 return StreamSupport.longStream 682 (new RandomLongsSpliterator 683 (this, 0L, streamSize, Long.MAX_VALUE, 0L), 684 false); 685 } 686 687 /** 688 * Returns an effectively unlimited stream of pseudorandom {@code 689 * long} values from this generator and/or one split from it. 690 * 691 * @implNote This method is implemented to be equivalent to {@code 692 * longs(Long.MAX_VALUE)}. 693 * 694 * @return a stream of pseudorandom {@code long} values 695 */ longs()696 public LongStream longs() { 697 return StreamSupport.longStream 698 (new RandomLongsSpliterator 699 (this, 0L, Long.MAX_VALUE, Long.MAX_VALUE, 0L), 700 false); 701 } 702 703 /** 704 * Returns a stream producing the given {@code streamSize} number of 705 * pseudorandom {@code long} values from this generator and/or one split 706 * from it; each value conforms to the given origin (inclusive) and bound 707 * (exclusive). 708 * 709 * @param streamSize the number of values to generate 710 * @param randomNumberOrigin the origin (inclusive) of each random value 711 * @param randomNumberBound the bound (exclusive) of each random value 712 * @return a stream of pseudorandom {@code long} values, 713 * each with the given origin (inclusive) and bound (exclusive) 714 * @throws IllegalArgumentException if {@code streamSize} is 715 * less than zero, or {@code randomNumberOrigin} 716 * is greater than or equal to {@code randomNumberBound} 717 */ longs(long streamSize, long randomNumberOrigin, long randomNumberBound)718 public LongStream longs(long streamSize, long randomNumberOrigin, 719 long randomNumberBound) { 720 if (streamSize < 0L) 721 throw new IllegalArgumentException(BAD_SIZE); 722 if (randomNumberOrigin >= randomNumberBound) 723 throw new IllegalArgumentException(BAD_RANGE); 724 return StreamSupport.longStream 725 (new RandomLongsSpliterator 726 (this, 0L, streamSize, randomNumberOrigin, randomNumberBound), 727 false); 728 } 729 730 /** 731 * Returns an effectively unlimited stream of pseudorandom {@code 732 * long} values from this generator and/or one split from it; each value 733 * conforms to the given origin (inclusive) and bound (exclusive). 734 * 735 * @implNote This method is implemented to be equivalent to {@code 736 * longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. 737 * 738 * @param randomNumberOrigin the origin (inclusive) of each random value 739 * @param randomNumberBound the bound (exclusive) of each random value 740 * @return a stream of pseudorandom {@code long} values, 741 * each with the given origin (inclusive) and bound (exclusive) 742 * @throws IllegalArgumentException if {@code randomNumberOrigin} 743 * is greater than or equal to {@code randomNumberBound} 744 */ longs(long randomNumberOrigin, long randomNumberBound)745 public LongStream longs(long randomNumberOrigin, long randomNumberBound) { 746 if (randomNumberOrigin >= randomNumberBound) 747 throw new IllegalArgumentException(BAD_RANGE); 748 return StreamSupport.longStream 749 (new RandomLongsSpliterator 750 (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), 751 false); 752 } 753 754 /** 755 * Returns a stream producing the given {@code streamSize} number of 756 * pseudorandom {@code double} values from this generator and/or one split 757 * from it; each value is between zero (inclusive) and one (exclusive). 758 * 759 * @param streamSize the number of values to generate 760 * @return a stream of {@code double} values 761 * @throws IllegalArgumentException if {@code streamSize} is 762 * less than zero 763 */ doubles(long streamSize)764 public DoubleStream doubles(long streamSize) { 765 if (streamSize < 0L) 766 throw new IllegalArgumentException(BAD_SIZE); 767 return StreamSupport.doubleStream 768 (new RandomDoublesSpliterator 769 (this, 0L, streamSize, Double.MAX_VALUE, 0.0), 770 false); 771 } 772 773 /** 774 * Returns an effectively unlimited stream of pseudorandom {@code 775 * double} values from this generator and/or one split from it; each value 776 * is between zero (inclusive) and one (exclusive). 777 * 778 * @implNote This method is implemented to be equivalent to {@code 779 * doubles(Long.MAX_VALUE)}. 780 * 781 * @return a stream of pseudorandom {@code double} values 782 */ doubles()783 public DoubleStream doubles() { 784 return StreamSupport.doubleStream 785 (new RandomDoublesSpliterator 786 (this, 0L, Long.MAX_VALUE, Double.MAX_VALUE, 0.0), 787 false); 788 } 789 790 /** 791 * Returns a stream producing the given {@code streamSize} number of 792 * pseudorandom {@code double} values from this generator and/or one split 793 * from it; each value conforms to the given origin (inclusive) and bound 794 * (exclusive). 795 * 796 * @param streamSize the number of values to generate 797 * @param randomNumberOrigin the origin (inclusive) of each random value 798 * @param randomNumberBound the bound (exclusive) of each random value 799 * @return a stream of pseudorandom {@code double} values, 800 * each with the given origin (inclusive) and bound (exclusive) 801 * @throws IllegalArgumentException if {@code streamSize} is 802 * less than zero, or {@code randomNumberOrigin} 803 * is greater than or equal to {@code randomNumberBound} 804 */ doubles(long streamSize, double randomNumberOrigin, double randomNumberBound)805 public DoubleStream doubles(long streamSize, double randomNumberOrigin, 806 double randomNumberBound) { 807 if (streamSize < 0L) 808 throw new IllegalArgumentException(BAD_SIZE); 809 if (!(randomNumberOrigin < randomNumberBound)) 810 throw new IllegalArgumentException(BAD_RANGE); 811 return StreamSupport.doubleStream 812 (new RandomDoublesSpliterator 813 (this, 0L, streamSize, randomNumberOrigin, randomNumberBound), 814 false); 815 } 816 817 /** 818 * Returns an effectively unlimited stream of pseudorandom {@code 819 * double} values from this generator and/or one split from it; each value 820 * conforms to the given origin (inclusive) and bound (exclusive). 821 * 822 * @implNote This method is implemented to be equivalent to {@code 823 * doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. 824 * 825 * @param randomNumberOrigin the origin (inclusive) of each random value 826 * @param randomNumberBound the bound (exclusive) of each random value 827 * @return a stream of pseudorandom {@code double} values, 828 * each with the given origin (inclusive) and bound (exclusive) 829 * @throws IllegalArgumentException if {@code randomNumberOrigin} 830 * is greater than or equal to {@code randomNumberBound} 831 */ doubles(double randomNumberOrigin, double randomNumberBound)832 public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) { 833 if (!(randomNumberOrigin < randomNumberBound)) 834 throw new IllegalArgumentException(BAD_RANGE); 835 return StreamSupport.doubleStream 836 (new RandomDoublesSpliterator 837 (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), 838 false); 839 } 840 841 /** 842 * Spliterator for int streams. We multiplex the four int 843 * versions into one class by treating a bound less than origin as 844 * unbounded, and also by treating "infinite" as equivalent to 845 * Long.MAX_VALUE. For splits, it uses the standard divide-by-two 846 * approach. The long and double versions of this class are 847 * identical except for types. 848 */ 849 private static final class RandomIntsSpliterator 850 implements Spliterator.OfInt { 851 final SplittableRandom rng; 852 long index; 853 final long fence; 854 final int origin; 855 final int bound; RandomIntsSpliterator(SplittableRandom rng, long index, long fence, int origin, int bound)856 RandomIntsSpliterator(SplittableRandom rng, long index, long fence, 857 int origin, int bound) { 858 this.rng = rng; this.index = index; this.fence = fence; 859 this.origin = origin; this.bound = bound; 860 } 861 trySplit()862 public RandomIntsSpliterator trySplit() { 863 long i = index, m = (i + fence) >>> 1; 864 return (m <= i) ? null : 865 new RandomIntsSpliterator(rng.split(), i, index = m, origin, bound); 866 } 867 estimateSize()868 public long estimateSize() { 869 return fence - index; 870 } 871 characteristics()872 public int characteristics() { 873 return (Spliterator.SIZED | Spliterator.SUBSIZED | 874 Spliterator.NONNULL | Spliterator.IMMUTABLE); 875 } 876 tryAdvance(IntConsumer consumer)877 public boolean tryAdvance(IntConsumer consumer) { 878 if (consumer == null) throw new NullPointerException(); 879 long i = index, f = fence; 880 if (i < f) { 881 consumer.accept(rng.internalNextInt(origin, bound)); 882 index = i + 1; 883 return true; 884 } 885 return false; 886 } 887 forEachRemaining(IntConsumer consumer)888 public void forEachRemaining(IntConsumer consumer) { 889 if (consumer == null) throw new NullPointerException(); 890 long i = index, f = fence; 891 if (i < f) { 892 index = f; 893 SplittableRandom r = rng; 894 int o = origin, b = bound; 895 do { 896 consumer.accept(r.internalNextInt(o, b)); 897 } while (++i < f); 898 } 899 } 900 } 901 902 /** 903 * Spliterator for long streams. 904 */ 905 private static final class RandomLongsSpliterator 906 implements Spliterator.OfLong { 907 final SplittableRandom rng; 908 long index; 909 final long fence; 910 final long origin; 911 final long bound; RandomLongsSpliterator(SplittableRandom rng, long index, long fence, long origin, long bound)912 RandomLongsSpliterator(SplittableRandom rng, long index, long fence, 913 long origin, long bound) { 914 this.rng = rng; this.index = index; this.fence = fence; 915 this.origin = origin; this.bound = bound; 916 } 917 trySplit()918 public RandomLongsSpliterator trySplit() { 919 long i = index, m = (i + fence) >>> 1; 920 return (m <= i) ? null : 921 new RandomLongsSpliterator(rng.split(), i, index = m, origin, bound); 922 } 923 estimateSize()924 public long estimateSize() { 925 return fence - index; 926 } 927 characteristics()928 public int characteristics() { 929 return (Spliterator.SIZED | Spliterator.SUBSIZED | 930 Spliterator.NONNULL | Spliterator.IMMUTABLE); 931 } 932 tryAdvance(LongConsumer consumer)933 public boolean tryAdvance(LongConsumer consumer) { 934 if (consumer == null) throw new NullPointerException(); 935 long i = index, f = fence; 936 if (i < f) { 937 consumer.accept(rng.internalNextLong(origin, bound)); 938 index = i + 1; 939 return true; 940 } 941 return false; 942 } 943 forEachRemaining(LongConsumer consumer)944 public void forEachRemaining(LongConsumer consumer) { 945 if (consumer == null) throw new NullPointerException(); 946 long i = index, f = fence; 947 if (i < f) { 948 index = f; 949 SplittableRandom r = rng; 950 long o = origin, b = bound; 951 do { 952 consumer.accept(r.internalNextLong(o, b)); 953 } while (++i < f); 954 } 955 } 956 957 } 958 959 /** 960 * Spliterator for double streams. 961 */ 962 private static final class RandomDoublesSpliterator 963 implements Spliterator.OfDouble { 964 final SplittableRandom rng; 965 long index; 966 final long fence; 967 final double origin; 968 final double bound; RandomDoublesSpliterator(SplittableRandom rng, long index, long fence, double origin, double bound)969 RandomDoublesSpliterator(SplittableRandom rng, long index, long fence, 970 double origin, double bound) { 971 this.rng = rng; this.index = index; this.fence = fence; 972 this.origin = origin; this.bound = bound; 973 } 974 trySplit()975 public RandomDoublesSpliterator trySplit() { 976 long i = index, m = (i + fence) >>> 1; 977 return (m <= i) ? null : 978 new RandomDoublesSpliterator(rng.split(), i, index = m, origin, bound); 979 } 980 estimateSize()981 public long estimateSize() { 982 return fence - index; 983 } 984 characteristics()985 public int characteristics() { 986 return (Spliterator.SIZED | Spliterator.SUBSIZED | 987 Spliterator.NONNULL | Spliterator.IMMUTABLE); 988 } 989 tryAdvance(DoubleConsumer consumer)990 public boolean tryAdvance(DoubleConsumer consumer) { 991 if (consumer == null) throw new NullPointerException(); 992 long i = index, f = fence; 993 if (i < f) { 994 consumer.accept(rng.internalNextDouble(origin, bound)); 995 index = i + 1; 996 return true; 997 } 998 return false; 999 } 1000 forEachRemaining(DoubleConsumer consumer)1001 public void forEachRemaining(DoubleConsumer consumer) { 1002 if (consumer == null) throw new NullPointerException(); 1003 long i = index, f = fence; 1004 if (i < f) { 1005 index = f; 1006 SplittableRandom r = rng; 1007 double o = origin, b = bound; 1008 do { 1009 consumer.accept(r.internalNextDouble(o, b)); 1010 } while (++i < f); 1011 } 1012 } 1013 } 1014 1015 } 1016