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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 1.36 by jsr166, Sun Nov 13 03:36:50 2016 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 229 | Line 219 | public class SplittableRandom {
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 = new AtomicLong(initialSeed());
231	<
232	<	private static long initialSeed() {
233	<	String pp = java.security.AccessController.doPrivileged(
234	<	new sun.security.action.GetPropertyAction(
235	<	"java.util.secureRandomSeed"));
236	<	if (pp != null && pp.equalsIgnoreCase("true")) {
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;
242	>	long s = (long)seedBytes[0] & 0xffL;
243		for (int i = 1; i < 8; ++i)
244	<	s = (s << 8) | ((long)(seedBytes[i]) & 0xffL);
245	<	return s;
247	<	}
248	<	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) {
244	>	s = (s << 8) | ((long)seedBytes[i] & 0xffL);
245	>	defaultGen.set(s);
246		}
275	–	return (h ^ mix64(System.currentTimeMillis()) ^
276	–	mix64(System.nanoTime()));
247		}
248
279	–	// IllegalArgumentException messages
280	–	static final String BadBound = "bound must be positive";
281	–	static final String BadRange = "bound must be greater than origin";
282	–	static final String BadSize  = "size must be non-negative";
283	–
249		/*
250		* Internal versions of nextX methods used by streams, as well as
251		* the public nextX(origin, bound) methods.  These exist mainly to
#	Line 381 | Line 346 | public class SplittableRandom {
346		* @return a pseudorandom value
347		*/
348		final double internalNextDouble(double origin, double bound) {
349	<	double r = (nextLong() >>> 11) * DOUBLE_ULP;
349	>	double r = (nextLong() >>> 11) * DOUBLE_UNIT;
350		if (origin < bound) {
351		r = r * (bound - origin) + origin;
352		if (r >= bound) // correct for rounding
#	Line 410 | Line 375 | public class SplittableRandom {
375		* may, and typically does, vary across program invocations.
376		*/
377		public SplittableRandom() { // emulate defaultGen.split()
378	<	long s = defaultGen.getAndAdd(2*GOLDEN_GAMMA);
378	>	long s = defaultGen.getAndAdd(2 * GOLDEN_GAMMA);
379		this.seed = mix64(s);
380		this.gamma = mixGamma(s + GOLDEN_GAMMA);
381		}
#	Line 453 | Line 418 | public class SplittableRandom {
418		*/
419		public int nextInt(int bound) {
420		if (bound <= 0)
421	<	throw new IllegalArgumentException(BadBound);
421	>	throw new IllegalArgumentException(BAD_BOUND);
422		// Specialize internalNextInt for origin 0
423		int r = mix32(nextSeed());
424		int m = bound - 1;
#	Line 481 | Line 446 | public class SplittableRandom {
446		*/
447		public int nextInt(int origin, int bound) {
448		if (origin >= bound)
449	<	throw new IllegalArgumentException(BadRange);
449	>	throw new IllegalArgumentException(BAD_RANGE);
450		return internalNextInt(origin, bound);
451		}
452
#	Line 505 | Line 470 | public class SplittableRandom {
470		*/
471		public long nextLong(long bound) {
472		if (bound <= 0)
473	<	throw new IllegalArgumentException(BadBound);
473	>	throw new IllegalArgumentException(BAD_BOUND);
474		// Specialize internalNextLong for origin 0
475		long r = mix64(nextSeed());
476		long m = bound - 1;
#	Line 533 | Line 498 | public class SplittableRandom {
498		*/
499		public long nextLong(long origin, long bound) {
500		if (origin >= bound)
501	<	throw new IllegalArgumentException(BadRange);
501	>	throw new IllegalArgumentException(BAD_RANGE);
502		return internalNextLong(origin, bound);
503		}
504
#	Line 545 | Line 510 | public class SplittableRandom {
510		*         (inclusive) and one (exclusive)
511		*/
512		public double nextDouble() {
513	<	return (mix64(nextSeed()) >>> 11) * DOUBLE_ULP;
513	>	return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT;
514		}
515
516		/**
#	Line 559 | Line 524 | public class SplittableRandom {
524		*/
525		public double nextDouble(double bound) {
526		if (!(bound > 0.0))
527	<	throw new IllegalArgumentException(BadBound);
528	<	double result = (mix64(nextSeed()) >>> 11) * DOUBLE_ULP * bound;
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	+	* Generates a pseudorandom number with the indicated number of
535	+	* low-order bits.  Because this class has no subclasses, this
536	+	* method cannot be invoked or overridden.
537	+	*
538	+	* @param  bits random bits
539	+	* @return the next pseudorandom value from this random number
540	+	*         generator's sequence
541	+	*/
542	+	protected int next(int bits) {
543	+	return nextInt() >>> (32 - bits);
544	+	}
545	+
546	+	/**
547		* Returns a pseudorandom {@code double} value between the specified
548		* origin (inclusive) and bound (exclusive).
549		*
#	Line 578 | Line 556 | public class SplittableRandom {
556		*/
557		public double nextDouble(double origin, double bound) {
558		if (!(origin < bound))
559	<	throw new IllegalArgumentException(BadRange);
559	>	throw new IllegalArgumentException(BAD_RANGE);
560		return internalNextDouble(origin, bound);
561		}
562
#	Line 606 | Line 584 | public class SplittableRandom {
584		*/
585		public IntStream ints(long streamSize) {
586		if (streamSize < 0L)
587	<	throw new IllegalArgumentException(BadSize);
587	>	throw new IllegalArgumentException(BAD_SIZE);
588		return StreamSupport.intStream
589		(new RandomIntsSpliterator
590		(this, 0L, streamSize, Integer.MAX_VALUE, 0),
#	Line 647 | Line 625 | public class SplittableRandom {
625		public IntStream ints(long streamSize, int randomNumberOrigin,
626		int randomNumberBound) {
627		if (streamSize < 0L)
628	<	throw new IllegalArgumentException(BadSize);
628	>	throw new IllegalArgumentException(BAD_SIZE);
629		if (randomNumberOrigin >= randomNumberBound)
630	<	throw new IllegalArgumentException(BadRange);
630	>	throw new IllegalArgumentException(BAD_RANGE);
631		return StreamSupport.intStream
632		(new RandomIntsSpliterator
633		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 673 | Line 651 | public class SplittableRandom {
651		*/
652		public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
653		if (randomNumberOrigin >= randomNumberBound)
654	<	throw new IllegalArgumentException(BadRange);
654	>	throw new IllegalArgumentException(BAD_RANGE);
655		return StreamSupport.intStream
656		(new RandomIntsSpliterator
657		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 692 | Line 670 | public class SplittableRandom {
670		*/
671		public LongStream longs(long streamSize) {
672		if (streamSize < 0L)
673	<	throw new IllegalArgumentException(BadSize);
673	>	throw new IllegalArgumentException(BAD_SIZE);
674		return StreamSupport.longStream
675		(new RandomLongsSpliterator
676		(this, 0L, streamSize, Long.MAX_VALUE, 0L),
#	Line 733 | Line 711 | public class SplittableRandom {
711		public LongStream longs(long streamSize, long randomNumberOrigin,
712		long randomNumberBound) {
713		if (streamSize < 0L)
714	<	throw new IllegalArgumentException(BadSize);
714	>	throw new IllegalArgumentException(BAD_SIZE);
715		if (randomNumberOrigin >= randomNumberBound)
716	<	throw new IllegalArgumentException(BadRange);
716	>	throw new IllegalArgumentException(BAD_RANGE);
717		return StreamSupport.longStream
718		(new RandomLongsSpliterator
719		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 759 | Line 737 | public class SplittableRandom {
737		*/
738		public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
739		if (randomNumberOrigin >= randomNumberBound)
740	<	throw new IllegalArgumentException(BadRange);
740	>	throw new IllegalArgumentException(BAD_RANGE);
741		return StreamSupport.longStream
742		(new RandomLongsSpliterator
743		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 778 | Line 756 | public class SplittableRandom {
756		*/
757		public DoubleStream doubles(long streamSize) {
758		if (streamSize < 0L)
759	<	throw new IllegalArgumentException(BadSize);
759	>	throw new IllegalArgumentException(BAD_SIZE);
760		return StreamSupport.doubleStream
761		(new RandomDoublesSpliterator
762		(this, 0L, streamSize, Double.MAX_VALUE, 0.0),
#	Line 821 | Line 799 | public class SplittableRandom {
799		public DoubleStream doubles(long streamSize, double randomNumberOrigin,
800		double randomNumberBound) {
801		if (streamSize < 0L)
802	<	throw new IllegalArgumentException(BadSize);
802	>	throw new IllegalArgumentException(BAD_SIZE);
803		if (!(randomNumberOrigin < randomNumberBound))
804	<	throw new IllegalArgumentException(BadRange);
804	>	throw new IllegalArgumentException(BAD_RANGE);
805		return StreamSupport.doubleStream
806		(new RandomDoublesSpliterator
807		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 847 | Line 825 | public class SplittableRandom {
825		*/
826		public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
827		if (!(randomNumberOrigin < randomNumberBound))
828	<	throw new IllegalArgumentException(BadRange);
828	>	throw new IllegalArgumentException(BAD_RANGE);
829		return StreamSupport.doubleStream
830		(new RandomDoublesSpliterator
831		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 862 | Line 840 | public class SplittableRandom {
840		* approach. The long and double versions of this class are
841		* identical except for types.
842		*/
843	<	static final class RandomIntsSpliterator implements Spliterator.OfInt {
843	>	private static final class RandomIntsSpliterator
844	>	implements Spliterator.OfInt {
845		final SplittableRandom rng;
846		long index;
847		final long fence;
#	Line 917 | Line 896 | public class SplittableRandom {
896		/**
897		* Spliterator for long streams.
898		*/
899	<	static final class RandomLongsSpliterator implements Spliterator.OfLong {
899	>	private static final class RandomLongsSpliterator
900	>	implements Spliterator.OfLong {
901		final SplittableRandom rng;
902		long index;
903		final long fence;
#	Line 973 | Line 953 | public class SplittableRandom {
953		/**
954		* Spliterator for double streams.
955		*/
956	<	static final class RandomDoublesSpliterator implements Spliterator.OfDouble {
956	>	private static final class RandomDoublesSpliterator
957	>	implements Spliterator.OfDouble {
958		final SplittableRandom rng;
959		long index;
960		final long fence;

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