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Comparing jsr166/src/main/java/util/SplittableRandom.java (file contents):
Revision 1.21 by dl, Thu Sep 19 23:19:43 2013 UTC vs.
Revision 1.29 by jsr166, Sun Sep 20 02:41:36 2015 UTC

#	Line 25 | Line 25
25
26		package java.util;
27
28	–	import java.security.SecureRandom;
29	–	import java.net.NetworkInterface;
30	–	import java.util.Enumeration;
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.function.DoubleConsumer;
35	<	import java.util.stream.StreamSupport;
32	>	import java.util.stream.DoubleStream;
33		import java.util.stream.IntStream;
34		import java.util.stream.LongStream;
35	<	import java.util.stream.DoubleStream;
35	>	import java.util.stream.StreamSupport;
36
37		/**
38		* A generator of uniform pseudorandom values applicable for use in
#	Line 55 | Line 52 | import java.util.stream.DoubleStream;
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>. </li>
55	>	* least 2<sup>64</sup>.
56		*
57	<	* <li> Method {@link #split} constructs and returns a new
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.  </li>
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
#	Line 74 | Line 71 | import java.util.stream.DoubleStream;
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.</li>
74	>	* stream.parallel()} mode.
75		*
76		* </ul>
77		*
#	Line 89 | Line 86 | import java.util.stream.DoubleStream;
86		* @author  Doug Lea
87		* @since   1.8
88		*/
89	<	public class SplittableRandom {
89	>	public final class SplittableRandom {
90
91		/*
92		* Implementation Overview.
#	Line 112 | Line 109 | public class SplittableRandom {
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
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		*
#	Line 142 | Line 139 | public class SplittableRandom {
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 and
143	<	* network interface address unless the java.util.secureRandomSeed
144	<	* property is set. This serves as a slimmed-down (and insecure)
145	<	* variant of SecureRandom that also avoids stalls that may occur
149	<	* when using /dev/random.
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
#	Line 168 | Line 164 | public class SplittableRandom {
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_ULP = 1.0 / (1L << 53);
167	>	private static final double DOUBLE_UNIT = 0x1.0p-53; // 1.0 / (1L << 53);
168
169		/**
170		* The seed. Updated only via method nextSeed.
#	Line 192 | Line 188 | public class SplittableRandom {
188		* Computes Stafford variant 13 of 64bit mix function.
189		*/
190		private static long mix64(long z) {
191	<	z *= 0xbf58476d1ce4e5b9L;
196	<	z = (z ^ (z >>> 32)) * 0x94d049bb133111ebL;
197	<	return z ^ (z >>> 32);
198	<	}
199	<
200	<	private static long xmix64(long z) {
201	<	z *= 0xbf58476d1ce4e5b9L;
191	>	z = (z ^ (z >>> 30)) * 0xbf58476d1ce4e5b9L;
192		z = (z ^ (z >>> 27)) * 0x94d049bb133111ebL;
193		return z ^ (z >>> 31);
194		}
#	Line 207 | Line 197 | public class SplittableRandom {
197		* Returns the 32 high bits of Stafford variant 4 mix64 function as int.
198		*/
199		private static int mix32(long z) {
200	<	z *= 0x62a9d9ed799705f5L;
200	>	z = (z ^ (z >>> 33)) * 0x62a9d9ed799705f5L;
201		return (int)(((z ^ (z >>> 28)) * 0xcb24d0a5c88c35b3L) >>> 32);
202		}
203
#	Line 215 | Line 205 | public class SplittableRandom {
205		* Returns the gamma value to use for a new split instance.
206		*/
207		private static long mixGamma(long z) {
208	<	z *= 0xff51afd7ed558ccdL;                   // MurmurHash3 mix constants
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
#	Line 245 | Line 235 | public class SplittableRandom {
235		s = (s << 8) | ((long)(seedBytes[i]) & 0xffL);
236		return s;
237		}
238	<	long h = 0L;
249	<	try {
250	<	Enumeration<NetworkInterface> ifcs =
251	<	NetworkInterface.getNetworkInterfaces();
252	<	boolean retry = false; // retry once if getHardwareAddress is null
253	<	while (ifcs.hasMoreElements()) {
254	<	NetworkInterface ifc = ifcs.nextElement();
255	<	if (!ifc.isVirtual()) { // skip fake addresses
256	<	byte[] bs = ifc.getHardwareAddress();
257	<	if (bs != null) {
258	<	int n = bs.length;
259	<	int m = Math.min(n >>> 1, 4);
260	<	for (int i = 0; i < m; ++i)
261	<	h = (h << 16) ^ (bs[i] << 8) ^ bs[n-1-i];
262	<	if (m < 4)
263	<	h = (h << 8) ^ bs[n-1-m];
264	<	h = mix64(h);
265	<	break;
266	<	}
267	<	else if (!retry)
268	<	retry = true;
269	<	else
270	<	break;
271	<	}
272	<	}
273	<	} catch (Exception ignore) {
274	<	}
275	<	return (h ^ mix64(System.currentTimeMillis()) ^
238	>	return (mix64(System.currentTimeMillis()) ^
239		mix64(System.nanoTime()));
240		}
241
242		// IllegalArgumentException messages
243	<	static final String BadBound = "bound must be positive";
244	<	static final String BadRange = "bound must be greater than origin";
245	<	static final String BadSize  = "size must be non-negative";
243	>	static final String BAD_BOUND = "bound must be positive";
244	>	static final String BAD_RANGE = "bound must be greater than origin";
245	>	static final String BAD_SIZE  = "size must be non-negative";
246
247		/*
248		* Internal versions of nextX methods used by streams, as well as
#	Line 381 | Line 344 | public class SplittableRandom {
344		* @return a pseudorandom value
345		*/
346		final double internalNextDouble(double origin, double bound) {
347	<	double r = (nextLong() >>> 11) * DOUBLE_ULP;
347	>	double r = (nextLong() >>> 11) * DOUBLE_UNIT;
348		if (origin < bound) {
349		r = r * (bound - origin) + origin;
350		if (r >= bound) // correct for rounding
#	Line 410 | Line 373 | public class SplittableRandom {
373		* may, and typically does, vary across program invocations.
374		*/
375		public SplittableRandom() { // emulate defaultGen.split()
376	<	long s = defaultGen.getAndAdd(2*GOLDEN_GAMMA);
376	>	long s = defaultGen.getAndAdd(2 * GOLDEN_GAMMA);
377		this.seed = mix64(s);
378		this.gamma = mixGamma(s + GOLDEN_GAMMA);
379		}
#	Line 453 | Line 416 | public class SplittableRandom {
416		*/
417		public int nextInt(int bound) {
418		if (bound <= 0)
419	<	throw new IllegalArgumentException(BadBound);
419	>	throw new IllegalArgumentException(BAD_BOUND);
420		// Specialize internalNextInt for origin 0
421		int r = mix32(nextSeed());
422		int m = bound - 1;
#	Line 481 | Line 444 | public class SplittableRandom {
444		*/
445		public int nextInt(int origin, int bound) {
446		if (origin >= bound)
447	<	throw new IllegalArgumentException(BadRange);
447	>	throw new IllegalArgumentException(BAD_RANGE);
448		return internalNextInt(origin, bound);
449		}
450
#	Line 505 | Line 468 | public class SplittableRandom {
468		*/
469		public long nextLong(long bound) {
470		if (bound <= 0)
471	<	throw new IllegalArgumentException(BadBound);
471	>	throw new IllegalArgumentException(BAD_BOUND);
472		// Specialize internalNextLong for origin 0
473		long r = mix64(nextSeed());
474		long m = bound - 1;
#	Line 533 | Line 496 | public class SplittableRandom {
496		*/
497		public long nextLong(long origin, long bound) {
498		if (origin >= bound)
499	<	throw new IllegalArgumentException(BadRange);
499	>	throw new IllegalArgumentException(BAD_RANGE);
500		return internalNextLong(origin, bound);
501		}
502
#	Line 545 | Line 508 | public class SplittableRandom {
508		*         (inclusive) and one (exclusive)
509		*/
510		public double nextDouble() {
511	<	return (mix64(nextSeed()) >>> 11) * DOUBLE_ULP;
511	>	return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT;
512		}
513
514		/**
#	Line 559 | Line 522 | public class SplittableRandom {
522		*/
523		public double nextDouble(double bound) {
524		if (!(bound > 0.0))
525	<	throw new IllegalArgumentException(BadBound);
526	<	double result = (mix64(nextSeed()) >>> 11) * DOUBLE_ULP * bound;
525	>	throw new IllegalArgumentException(BAD_BOUND);
526	>	double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound;
527		return (result < bound) ?  result : // correct for rounding
528		Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
529		}
#	Line 578 | Line 541 | public class SplittableRandom {
541		*/
542		public double nextDouble(double origin, double bound) {
543		if (!(origin < bound))
544	<	throw new IllegalArgumentException(BadRange);
544	>	throw new IllegalArgumentException(BAD_RANGE);
545		return internalNextDouble(origin, bound);
546		}
547
#	Line 606 | Line 569 | public class SplittableRandom {
569		*/
570		public IntStream ints(long streamSize) {
571		if (streamSize < 0L)
572	<	throw new IllegalArgumentException(BadSize);
572	>	throw new IllegalArgumentException(BAD_SIZE);
573		return StreamSupport.intStream
574		(new RandomIntsSpliterator
575		(this, 0L, streamSize, Integer.MAX_VALUE, 0),
#	Line 647 | Line 610 | public class SplittableRandom {
610		public IntStream ints(long streamSize, int randomNumberOrigin,
611		int randomNumberBound) {
612		if (streamSize < 0L)
613	<	throw new IllegalArgumentException(BadSize);
613	>	throw new IllegalArgumentException(BAD_SIZE);
614		if (randomNumberOrigin >= randomNumberBound)
615	<	throw new IllegalArgumentException(BadRange);
615	>	throw new IllegalArgumentException(BAD_RANGE);
616		return StreamSupport.intStream
617		(new RandomIntsSpliterator
618		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 673 | Line 636 | public class SplittableRandom {
636		*/
637		public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
638		if (randomNumberOrigin >= randomNumberBound)
639	<	throw new IllegalArgumentException(BadRange);
639	>	throw new IllegalArgumentException(BAD_RANGE);
640		return StreamSupport.intStream
641		(new RandomIntsSpliterator
642		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 692 | Line 655 | public class SplittableRandom {
655		*/
656		public LongStream longs(long streamSize) {
657		if (streamSize < 0L)
658	<	throw new IllegalArgumentException(BadSize);
658	>	throw new IllegalArgumentException(BAD_SIZE);
659		return StreamSupport.longStream
660		(new RandomLongsSpliterator
661		(this, 0L, streamSize, Long.MAX_VALUE, 0L),
#	Line 733 | Line 696 | public class SplittableRandom {
696		public LongStream longs(long streamSize, long randomNumberOrigin,
697		long randomNumberBound) {
698		if (streamSize < 0L)
699	<	throw new IllegalArgumentException(BadSize);
699	>	throw new IllegalArgumentException(BAD_SIZE);
700		if (randomNumberOrigin >= randomNumberBound)
701	<	throw new IllegalArgumentException(BadRange);
701	>	throw new IllegalArgumentException(BAD_RANGE);
702		return StreamSupport.longStream
703		(new RandomLongsSpliterator
704		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 759 | Line 722 | public class SplittableRandom {
722		*/
723		public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
724		if (randomNumberOrigin >= randomNumberBound)
725	<	throw new IllegalArgumentException(BadRange);
725	>	throw new IllegalArgumentException(BAD_RANGE);
726		return StreamSupport.longStream
727		(new RandomLongsSpliterator
728		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 778 | Line 741 | public class SplittableRandom {
741		*/
742		public DoubleStream doubles(long streamSize) {
743		if (streamSize < 0L)
744	<	throw new IllegalArgumentException(BadSize);
744	>	throw new IllegalArgumentException(BAD_SIZE);
745		return StreamSupport.doubleStream
746		(new RandomDoublesSpliterator
747		(this, 0L, streamSize, Double.MAX_VALUE, 0.0),
#	Line 821 | Line 784 | public class SplittableRandom {
784		public DoubleStream doubles(long streamSize, double randomNumberOrigin,
785		double randomNumberBound) {
786		if (streamSize < 0L)
787	<	throw new IllegalArgumentException(BadSize);
787	>	throw new IllegalArgumentException(BAD_SIZE);
788		if (!(randomNumberOrigin < randomNumberBound))
789	<	throw new IllegalArgumentException(BadRange);
789	>	throw new IllegalArgumentException(BAD_RANGE);
790		return StreamSupport.doubleStream
791		(new RandomDoublesSpliterator
792		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 847 | Line 810 | public class SplittableRandom {
810		*/
811		public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
812		if (!(randomNumberOrigin < randomNumberBound))
813	<	throw new IllegalArgumentException(BadRange);
813	>	throw new IllegalArgumentException(BAD_RANGE);
814		return StreamSupport.doubleStream
815		(new RandomDoublesSpliterator
816		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 862 | Line 825 | public class SplittableRandom {
825		* approach. The long and double versions of this class are
826		* identical except for types.
827		*/
828	<	static final class RandomIntsSpliterator implements Spliterator.OfInt {
828	>	private static final class RandomIntsSpliterator
829	>	implements Spliterator.OfInt {
830		final SplittableRandom rng;
831		long index;
832		final long fence;
#	Line 917 | Line 881 | public class SplittableRandom {
881		/**
882		* Spliterator for long streams.
883		*/
884	<	static final class RandomLongsSpliterator implements Spliterator.OfLong {
884	>	private static final class RandomLongsSpliterator
885	>	implements Spliterator.OfLong {
886		final SplittableRandom rng;
887		long index;
888		final long fence;
#	Line 973 | Line 938 | public class SplittableRandom {
938		/**
939		* Spliterator for double streams.
940		*/
941	<	static final class RandomDoublesSpliterator implements Spliterator.OfDouble {
941	>	private static final class RandomDoublesSpliterator
942	>	implements Spliterator.OfDouble {
943		final SplittableRandom rng;
944		long index;
945		final long fence;

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