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 26package java.util; 27 28import java.util.concurrent.atomic.AtomicLong; 29import java.util.function.DoubleConsumer; 30import java.util.function.IntConsumer; 31import java.util.function.LongConsumer; 32import java.util.stream.DoubleStream; 33import java.util.stream.IntStream; 34import java.util.stream.LongStream; 35import 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 */ 89public 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 */ 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 */ 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 */ 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 */ 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 */ 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 */ 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 */ 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 */ 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 */ 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 */ 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 */ 397 public SplittableRandom split() { 398 return new SplittableRandom(nextLong(), mixGamma(nextSeed())); 399 } 400 401 /** 402 * Returns a pseudorandom {@code int} value. 403 * 404 * @return a pseudorandom {@code int} value 405 */ 406 public int nextInt() { 407 return mix32(nextSeed()); 408 } 409 410 /** 411 * Returns a pseudorandom {@code int} value between zero (inclusive) 412 * and the specified bound (exclusive). 413 * 414 * @param bound the upper bound (exclusive). Must be positive. 415 * @return a pseudorandom {@code int} value between zero 416 * (inclusive) and the bound (exclusive) 417 * @throws IllegalArgumentException if {@code bound} is not positive 418 */ 419 public int nextInt(int bound) { 420 if (bound <= 0) 421 throw new IllegalArgumentException(BAD_BOUND); 422 // Specialize internalNextInt for origin 0 423 int r = mix32(nextSeed()); 424 int m = bound - 1; 425 if ((bound & m) == 0) // power of two 426 r &= m; 427 else { // reject over-represented candidates 428 for (int u = r >>> 1; 429 u + m - (r = u % bound) < 0; 430 u = mix32(nextSeed()) >>> 1) 431 ; 432 } 433 return r; 434 } 435 436 /** 437 * Returns a pseudorandom {@code int} value between the specified 438 * origin (inclusive) and the specified bound (exclusive). 439 * 440 * @param origin the least value returned 441 * @param bound the upper bound (exclusive) 442 * @return a pseudorandom {@code int} value between the origin 443 * (inclusive) and the bound (exclusive) 444 * @throws IllegalArgumentException if {@code origin} is greater than 445 * or equal to {@code bound} 446 */ 447 public int nextInt(int origin, int bound) { 448 if (origin >= bound) 449 throw new IllegalArgumentException(BAD_RANGE); 450 return internalNextInt(origin, bound); 451 } 452 453 /** 454 * Returns a pseudorandom {@code long} value. 455 * 456 * @return a pseudorandom {@code long} value 457 */ 458 public long nextLong() { 459 return mix64(nextSeed()); 460 } 461 462 /** 463 * Returns a pseudorandom {@code long} value between zero (inclusive) 464 * and the specified bound (exclusive). 465 * 466 * @param bound the upper bound (exclusive). Must be positive. 467 * @return a pseudorandom {@code long} value between zero 468 * (inclusive) and the bound (exclusive) 469 * @throws IllegalArgumentException if {@code bound} is not positive 470 */ 471 public long nextLong(long bound) { 472 if (bound <= 0) 473 throw new IllegalArgumentException(BAD_BOUND); 474 // Specialize internalNextLong for origin 0 475 long r = mix64(nextSeed()); 476 long m = bound - 1; 477 if ((bound & m) == 0L) // power of two 478 r &= m; 479 else { // reject over-represented candidates 480 for (long u = r >>> 1; 481 u + m - (r = u % bound) < 0L; 482 u = mix64(nextSeed()) >>> 1) 483 ; 484 } 485 return r; 486 } 487 488 /** 489 * Returns a pseudorandom {@code long} value between the specified 490 * origin (inclusive) and the specified bound (exclusive). 491 * 492 * @param origin the least value returned 493 * @param bound the upper bound (exclusive) 494 * @return a pseudorandom {@code long} value between the origin 495 * (inclusive) and the bound (exclusive) 496 * @throws IllegalArgumentException if {@code origin} is greater than 497 * or equal to {@code bound} 498 */ 499 public long nextLong(long origin, long bound) { 500 if (origin >= bound) 501 throw new IllegalArgumentException(BAD_RANGE); 502 return internalNextLong(origin, bound); 503 } 504 505 /** 506 * Returns a pseudorandom {@code double} value between zero 507 * (inclusive) and one (exclusive). 508 * 509 * @return a pseudorandom {@code double} value between zero 510 * (inclusive) and one (exclusive) 511 */ 512 public double nextDouble() { 513 return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT; 514 } 515 516 /** 517 * Returns a pseudorandom {@code double} value between 0.0 518 * (inclusive) and the specified bound (exclusive). 519 * 520 * @param bound the upper bound (exclusive). Must be positive. 521 * @return a pseudorandom {@code double} value between zero 522 * (inclusive) and the bound (exclusive) 523 * @throws IllegalArgumentException if {@code bound} is not positive 524 */ 525 public double nextDouble(double bound) { 526 if (!(bound > 0.0)) 527 throw new IllegalArgumentException(BAD_BOUND); 528 double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound; 529 return (result < bound) ? result : // correct for rounding 530 Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1); 531 } 532 533 /** 534 * Returns a pseudorandom {@code double} value between the specified 535 * origin (inclusive) and bound (exclusive). 536 * 537 * @param origin the least value returned 538 * @param bound the upper bound (exclusive) 539 * @return a pseudorandom {@code double} value between the origin 540 * (inclusive) and the bound (exclusive) 541 * @throws IllegalArgumentException if {@code origin} is greater than 542 * or equal to {@code bound} 543 */ 544 public double nextDouble(double origin, double bound) { 545 if (!(origin < bound)) 546 throw new IllegalArgumentException(BAD_RANGE); 547 return internalNextDouble(origin, bound); 548 } 549 550 /** 551 * Returns a pseudorandom {@code boolean} value. 552 * 553 * @return a pseudorandom {@code boolean} value 554 */ 555 public boolean nextBoolean() { 556 return mix32(nextSeed()) < 0; 557 } 558 559 // stream methods, coded in a way intended to better isolate for 560 // maintenance purposes the small differences across forms. 561 562 /** 563 * Returns a stream producing the given {@code streamSize} number 564 * of pseudorandom {@code int} values from this generator and/or 565 * one split from it. 566 * 567 * @param streamSize the number of values to generate 568 * @return a stream of pseudorandom {@code int} values 569 * @throws IllegalArgumentException if {@code streamSize} is 570 * less than zero 571 */ 572 public IntStream ints(long streamSize) { 573 if (streamSize < 0L) 574 throw new IllegalArgumentException(BAD_SIZE); 575 return StreamSupport.intStream 576 (new RandomIntsSpliterator 577 (this, 0L, streamSize, Integer.MAX_VALUE, 0), 578 false); 579 } 580 581 /** 582 * Returns an effectively unlimited stream of pseudorandom {@code int} 583 * values from this generator and/or one split from it. 584 * 585 * @implNote This method is implemented to be equivalent to {@code 586 * ints(Long.MAX_VALUE)}. 587 * 588 * @return a stream of pseudorandom {@code int} values 589 */ 590 public IntStream ints() { 591 return StreamSupport.intStream 592 (new RandomIntsSpliterator 593 (this, 0L, Long.MAX_VALUE, Integer.MAX_VALUE, 0), 594 false); 595 } 596 597 /** 598 * Returns a stream producing the given {@code streamSize} number 599 * of pseudorandom {@code int} values from this generator and/or one split 600 * from it; each value conforms to the given origin (inclusive) and bound 601 * (exclusive). 602 * 603 * @param streamSize the number of values to generate 604 * @param randomNumberOrigin the origin (inclusive) of each random value 605 * @param randomNumberBound the bound (exclusive) of each random value 606 * @return a stream of pseudorandom {@code int} values, 607 * each with the given origin (inclusive) and bound (exclusive) 608 * @throws IllegalArgumentException if {@code streamSize} is 609 * less than zero, or {@code randomNumberOrigin} 610 * is greater than or equal to {@code randomNumberBound} 611 */ 612 public IntStream ints(long streamSize, int randomNumberOrigin, 613 int randomNumberBound) { 614 if (streamSize < 0L) 615 throw new IllegalArgumentException(BAD_SIZE); 616 if (randomNumberOrigin >= randomNumberBound) 617 throw new IllegalArgumentException(BAD_RANGE); 618 return StreamSupport.intStream 619 (new RandomIntsSpliterator 620 (this, 0L, streamSize, randomNumberOrigin, randomNumberBound), 621 false); 622 } 623 624 /** 625 * Returns an effectively unlimited stream of pseudorandom {@code 626 * int} values from this generator and/or one split from it; each value 627 * conforms to the given origin (inclusive) and bound (exclusive). 628 * 629 * @implNote This method is implemented to be equivalent to {@code 630 * ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. 631 * 632 * @param randomNumberOrigin the origin (inclusive) of each random value 633 * @param randomNumberBound the bound (exclusive) of each random value 634 * @return a stream of pseudorandom {@code int} values, 635 * each with the given origin (inclusive) and bound (exclusive) 636 * @throws IllegalArgumentException if {@code randomNumberOrigin} 637 * is greater than or equal to {@code randomNumberBound} 638 */ 639 public IntStream ints(int randomNumberOrigin, int randomNumberBound) { 640 if (randomNumberOrigin >= randomNumberBound) 641 throw new IllegalArgumentException(BAD_RANGE); 642 return StreamSupport.intStream 643 (new RandomIntsSpliterator 644 (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), 645 false); 646 } 647 648 /** 649 * Returns a stream producing the given {@code streamSize} number 650 * of pseudorandom {@code long} values from this generator and/or 651 * one split from it. 652 * 653 * @param streamSize the number of values to generate 654 * @return a stream of pseudorandom {@code long} values 655 * @throws IllegalArgumentException if {@code streamSize} is 656 * less than zero 657 */ 658 public LongStream longs(long streamSize) { 659 if (streamSize < 0L) 660 throw new IllegalArgumentException(BAD_SIZE); 661 return StreamSupport.longStream 662 (new RandomLongsSpliterator 663 (this, 0L, streamSize, Long.MAX_VALUE, 0L), 664 false); 665 } 666 667 /** 668 * Returns an effectively unlimited stream of pseudorandom {@code 669 * long} values from this generator and/or one split from it. 670 * 671 * @implNote This method is implemented to be equivalent to {@code 672 * longs(Long.MAX_VALUE)}. 673 * 674 * @return a stream of pseudorandom {@code long} values 675 */ 676 public LongStream longs() { 677 return StreamSupport.longStream 678 (new RandomLongsSpliterator 679 (this, 0L, Long.MAX_VALUE, Long.MAX_VALUE, 0L), 680 false); 681 } 682 683 /** 684 * Returns a stream producing the given {@code streamSize} number of 685 * pseudorandom {@code long} values from this generator and/or one split 686 * from it; each value conforms to the given origin (inclusive) and bound 687 * (exclusive). 688 * 689 * @param streamSize the number of values to generate 690 * @param randomNumberOrigin the origin (inclusive) of each random value 691 * @param randomNumberBound the bound (exclusive) of each random value 692 * @return a stream of pseudorandom {@code long} values, 693 * each with the given origin (inclusive) and bound (exclusive) 694 * @throws IllegalArgumentException if {@code streamSize} is 695 * less than zero, or {@code randomNumberOrigin} 696 * is greater than or equal to {@code randomNumberBound} 697 */ 698 public LongStream longs(long streamSize, long randomNumberOrigin, 699 long randomNumberBound) { 700 if (streamSize < 0L) 701 throw new IllegalArgumentException(BAD_SIZE); 702 if (randomNumberOrigin >= randomNumberBound) 703 throw new IllegalArgumentException(BAD_RANGE); 704 return StreamSupport.longStream 705 (new RandomLongsSpliterator 706 (this, 0L, streamSize, randomNumberOrigin, randomNumberBound), 707 false); 708 } 709 710 /** 711 * Returns an effectively unlimited stream of pseudorandom {@code 712 * long} values from this generator and/or one split from it; each value 713 * conforms to the given origin (inclusive) and bound (exclusive). 714 * 715 * @implNote This method is implemented to be equivalent to {@code 716 * longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. 717 * 718 * @param randomNumberOrigin the origin (inclusive) of each random value 719 * @param randomNumberBound the bound (exclusive) of each random value 720 * @return a stream of pseudorandom {@code long} values, 721 * each with the given origin (inclusive) and bound (exclusive) 722 * @throws IllegalArgumentException if {@code randomNumberOrigin} 723 * is greater than or equal to {@code randomNumberBound} 724 */ 725 public LongStream longs(long randomNumberOrigin, long randomNumberBound) { 726 if (randomNumberOrigin >= randomNumberBound) 727 throw new IllegalArgumentException(BAD_RANGE); 728 return StreamSupport.longStream 729 (new RandomLongsSpliterator 730 (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), 731 false); 732 } 733 734 /** 735 * Returns a stream producing the given {@code streamSize} number of 736 * pseudorandom {@code double} values from this generator and/or one split 737 * from it; each value is between zero (inclusive) and one (exclusive). 738 * 739 * @param streamSize the number of values to generate 740 * @return a stream of {@code double} values 741 * @throws IllegalArgumentException if {@code streamSize} is 742 * less than zero 743 */ 744 public DoubleStream doubles(long streamSize) { 745 if (streamSize < 0L) 746 throw new IllegalArgumentException(BAD_SIZE); 747 return StreamSupport.doubleStream 748 (new RandomDoublesSpliterator 749 (this, 0L, streamSize, Double.MAX_VALUE, 0.0), 750 false); 751 } 752 753 /** 754 * Returns an effectively unlimited stream of pseudorandom {@code 755 * double} values from this generator and/or one split from it; each value 756 * is between zero (inclusive) and one (exclusive). 757 * 758 * @implNote This method is implemented to be equivalent to {@code 759 * doubles(Long.MAX_VALUE)}. 760 * 761 * @return a stream of pseudorandom {@code double} values 762 */ 763 public DoubleStream doubles() { 764 return StreamSupport.doubleStream 765 (new RandomDoublesSpliterator 766 (this, 0L, Long.MAX_VALUE, Double.MAX_VALUE, 0.0), 767 false); 768 } 769 770 /** 771 * Returns a stream producing the given {@code streamSize} number of 772 * pseudorandom {@code double} values from this generator and/or one split 773 * from it; each value conforms to the given origin (inclusive) and bound 774 * (exclusive). 775 * 776 * @param streamSize the number of values to generate 777 * @param randomNumberOrigin the origin (inclusive) of each random value 778 * @param randomNumberBound the bound (exclusive) of each random value 779 * @return a stream of pseudorandom {@code double} values, 780 * each with the given origin (inclusive) and bound (exclusive) 781 * @throws IllegalArgumentException if {@code streamSize} is 782 * less than zero, or {@code randomNumberOrigin} 783 * is greater than or equal to {@code randomNumberBound} 784 */ 785 public DoubleStream doubles(long streamSize, double randomNumberOrigin, 786 double randomNumberBound) { 787 if (streamSize < 0L) 788 throw new IllegalArgumentException(BAD_SIZE); 789 if (!(randomNumberOrigin < randomNumberBound)) 790 throw new IllegalArgumentException(BAD_RANGE); 791 return StreamSupport.doubleStream 792 (new RandomDoublesSpliterator 793 (this, 0L, streamSize, randomNumberOrigin, randomNumberBound), 794 false); 795 } 796 797 /** 798 * Returns an effectively unlimited stream of pseudorandom {@code 799 * double} values from this generator and/or one split from it; each value 800 * conforms to the given origin (inclusive) and bound (exclusive). 801 * 802 * @implNote This method is implemented to be equivalent to {@code 803 * doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. 804 * 805 * @param randomNumberOrigin the origin (inclusive) of each random value 806 * @param randomNumberBound the bound (exclusive) of each random value 807 * @return a stream of pseudorandom {@code double} values, 808 * each with the given origin (inclusive) and bound (exclusive) 809 * @throws IllegalArgumentException if {@code randomNumberOrigin} 810 * is greater than or equal to {@code randomNumberBound} 811 */ 812 public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) { 813 if (!(randomNumberOrigin < randomNumberBound)) 814 throw new IllegalArgumentException(BAD_RANGE); 815 return StreamSupport.doubleStream 816 (new RandomDoublesSpliterator 817 (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), 818 false); 819 } 820 821 /** 822 * Spliterator for int streams. We multiplex the four int 823 * versions into one class by treating a bound less than origin as 824 * unbounded, and also by treating "infinite" as equivalent to 825 * Long.MAX_VALUE. For splits, it uses the standard divide-by-two 826 * approach. The long and double versions of this class are 827 * identical except for types. 828 */ 829 private static final class RandomIntsSpliterator 830 implements Spliterator.OfInt { 831 final SplittableRandom rng; 832 long index; 833 final long fence; 834 final int origin; 835 final int bound; 836 RandomIntsSpliterator(SplittableRandom rng, long index, long fence, 837 int origin, int bound) { 838 this.rng = rng; this.index = index; this.fence = fence; 839 this.origin = origin; this.bound = bound; 840 } 841 842 public RandomIntsSpliterator trySplit() { 843 long i = index, m = (i + fence) >>> 1; 844 return (m <= i) ? null : 845 new RandomIntsSpliterator(rng.split(), i, index = m, origin, bound); 846 } 847 848 public long estimateSize() { 849 return fence - index; 850 } 851 852 public int characteristics() { 853 return (Spliterator.SIZED | Spliterator.SUBSIZED | 854 Spliterator.NONNULL | Spliterator.IMMUTABLE); 855 } 856 857 public boolean tryAdvance(IntConsumer consumer) { 858 if (consumer == null) throw new NullPointerException(); 859 long i = index, f = fence; 860 if (i < f) { 861 consumer.accept(rng.internalNextInt(origin, bound)); 862 index = i + 1; 863 return true; 864 } 865 return false; 866 } 867 868 public void forEachRemaining(IntConsumer consumer) { 869 if (consumer == null) throw new NullPointerException(); 870 long i = index, f = fence; 871 if (i < f) { 872 index = f; 873 SplittableRandom r = rng; 874 int o = origin, b = bound; 875 do { 876 consumer.accept(r.internalNextInt(o, b)); 877 } while (++i < f); 878 } 879 } 880 } 881 882 /** 883 * Spliterator for long streams. 884 */ 885 private static final class RandomLongsSpliterator 886 implements Spliterator.OfLong { 887 final SplittableRandom rng; 888 long index; 889 final long fence; 890 final long origin; 891 final long bound; 892 RandomLongsSpliterator(SplittableRandom rng, long index, long fence, 893 long origin, long bound) { 894 this.rng = rng; this.index = index; this.fence = fence; 895 this.origin = origin; this.bound = bound; 896 } 897 898 public RandomLongsSpliterator trySplit() { 899 long i = index, m = (i + fence) >>> 1; 900 return (m <= i) ? null : 901 new RandomLongsSpliterator(rng.split(), i, index = m, origin, bound); 902 } 903 904 public long estimateSize() { 905 return fence - index; 906 } 907 908 public int characteristics() { 909 return (Spliterator.SIZED | Spliterator.SUBSIZED | 910 Spliterator.NONNULL | Spliterator.IMMUTABLE); 911 } 912 913 public boolean tryAdvance(LongConsumer consumer) { 914 if (consumer == null) throw new NullPointerException(); 915 long i = index, f = fence; 916 if (i < f) { 917 consumer.accept(rng.internalNextLong(origin, bound)); 918 index = i + 1; 919 return true; 920 } 921 return false; 922 } 923 924 public void forEachRemaining(LongConsumer consumer) { 925 if (consumer == null) throw new NullPointerException(); 926 long i = index, f = fence; 927 if (i < f) { 928 index = f; 929 SplittableRandom r = rng; 930 long o = origin, b = bound; 931 do { 932 consumer.accept(r.internalNextLong(o, b)); 933 } while (++i < f); 934 } 935 } 936 937 } 938 939 /** 940 * Spliterator for double streams. 941 */ 942 private static final class RandomDoublesSpliterator 943 implements Spliterator.OfDouble { 944 final SplittableRandom rng; 945 long index; 946 final long fence; 947 final double origin; 948 final double bound; 949 RandomDoublesSpliterator(SplittableRandom rng, long index, long fence, 950 double origin, double bound) { 951 this.rng = rng; this.index = index; this.fence = fence; 952 this.origin = origin; this.bound = bound; 953 } 954 955 public RandomDoublesSpliterator trySplit() { 956 long i = index, m = (i + fence) >>> 1; 957 return (m <= i) ? null : 958 new RandomDoublesSpliterator(rng.split(), i, index = m, origin, bound); 959 } 960 961 public long estimateSize() { 962 return fence - index; 963 } 964 965 public int characteristics() { 966 return (Spliterator.SIZED | Spliterator.SUBSIZED | 967 Spliterator.NONNULL | Spliterator.IMMUTABLE); 968 } 969 970 public boolean tryAdvance(DoubleConsumer consumer) { 971 if (consumer == null) throw new NullPointerException(); 972 long i = index, f = fence; 973 if (i < f) { 974 consumer.accept(rng.internalNextDouble(origin, bound)); 975 index = i + 1; 976 return true; 977 } 978 return false; 979 } 980 981 public void forEachRemaining(DoubleConsumer consumer) { 982 if (consumer == null) throw new NullPointerException(); 983 long i = index, f = fence; 984 if (i < f) { 985 index = f; 986 SplittableRandom r = rng; 987 double o = origin, b = bound; 988 do { 989 consumer.accept(r.internalNextDouble(o, b)); 990 } while (++i < f); 991 } 992 } 993 } 994 995} 996