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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 1.41 by jsr166, Sun Dec 2 23:06:16 2018 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 83 | Line 80 | import java.util.stream.DoubleStream;
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}.
83	>	* {@systemProperty java.util.secureRandomSeed} is set to {@code true}.
84		*
85		* @author  Guy Steele
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;
244	>	s = (s << 8) | ((long)seedBytes[i] & 0xffL);
245	>	defaultGen.set(s);
246		}
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) {
274	–	}
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(GOLDEN_GAMMA << 1);
379		this.seed = mix64(s);
380		this.gamma = mixGamma(s + GOLDEN_GAMMA);
381		}
#	Line 434 | Line 399 | public class SplittableRandom {
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	+	*/
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
#	Line 453 | Line 438 | public class SplittableRandom {
438		*/
439		public int nextInt(int bound) {
440		if (bound <= 0)
441	<	throw new IllegalArgumentException(BadBound);
441	>	throw new IllegalArgumentException(BAD_BOUND);
442		// Specialize internalNextInt for origin 0
443		int r = mix32(nextSeed());
444		int m = bound - 1;
#	Line 481 | Line 466 | public class SplittableRandom {
466		*/
467		public int nextInt(int origin, int bound) {
468		if (origin >= bound)
469	<	throw new IllegalArgumentException(BadRange);
469	>	throw new IllegalArgumentException(BAD_RANGE);
470		return internalNextInt(origin, bound);
471		}
472
#	Line 505 | Line 490 | public class SplittableRandom {
490		*/
491		public long nextLong(long bound) {
492		if (bound <= 0)
493	<	throw new IllegalArgumentException(BadBound);
493	>	throw new IllegalArgumentException(BAD_BOUND);
494		// Specialize internalNextLong for origin 0
495		long r = mix64(nextSeed());
496		long m = bound - 1;
#	Line 533 | Line 518 | public class SplittableRandom {
518		*/
519		public long nextLong(long origin, long bound) {
520		if (origin >= bound)
521	<	throw new IllegalArgumentException(BadRange);
521	>	throw new IllegalArgumentException(BAD_RANGE);
522		return internalNextLong(origin, bound);
523		}
524
#	Line 545 | Line 530 | public class SplittableRandom {
530		*         (inclusive) and one (exclusive)
531		*/
532		public double nextDouble() {
533	<	return (mix64(nextSeed()) >>> 11) * DOUBLE_ULP;
533	>	return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT;
534		}
535
536		/**
#	Line 559 | Line 544 | public class SplittableRandom {
544		*/
545		public double nextDouble(double bound) {
546		if (!(bound > 0.0))
547	<	throw new IllegalArgumentException(BadBound);
548	<	double result = (mix64(nextSeed()) >>> 11) * DOUBLE_ULP * bound;
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		}
#	Line 578 | Line 563 | public class SplittableRandom {
563		*/
564		public double nextDouble(double origin, double bound) {
565		if (!(origin < bound))
566	<	throw new IllegalArgumentException(BadRange);
566	>	throw new IllegalArgumentException(BAD_RANGE);
567		return internalNextDouble(origin, bound);
568		}
569
#	Line 606 | Line 591 | public class SplittableRandom {
591		*/
592		public IntStream ints(long streamSize) {
593		if (streamSize < 0L)
594	<	throw new IllegalArgumentException(BadSize);
594	>	throw new IllegalArgumentException(BAD_SIZE);
595		return StreamSupport.intStream
596		(new RandomIntsSpliterator
597		(this, 0L, streamSize, Integer.MAX_VALUE, 0),
#	Line 647 | Line 632 | public class SplittableRandom {
632		public IntStream ints(long streamSize, int randomNumberOrigin,
633		int randomNumberBound) {
634		if (streamSize < 0L)
635	<	throw new IllegalArgumentException(BadSize);
635	>	throw new IllegalArgumentException(BAD_SIZE);
636		if (randomNumberOrigin >= randomNumberBound)
637	<	throw new IllegalArgumentException(BadRange);
637	>	throw new IllegalArgumentException(BAD_RANGE);
638		return StreamSupport.intStream
639		(new RandomIntsSpliterator
640		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 673 | Line 658 | public class SplittableRandom {
658		*/
659		public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
660		if (randomNumberOrigin >= randomNumberBound)
661	<	throw new IllegalArgumentException(BadRange);
661	>	throw new IllegalArgumentException(BAD_RANGE);
662		return StreamSupport.intStream
663		(new RandomIntsSpliterator
664		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 692 | Line 677 | public class SplittableRandom {
677		*/
678		public LongStream longs(long streamSize) {
679		if (streamSize < 0L)
680	<	throw new IllegalArgumentException(BadSize);
680	>	throw new IllegalArgumentException(BAD_SIZE);
681		return StreamSupport.longStream
682		(new RandomLongsSpliterator
683		(this, 0L, streamSize, Long.MAX_VALUE, 0L),
#	Line 733 | Line 718 | public class SplittableRandom {
718		public LongStream longs(long streamSize, long randomNumberOrigin,
719		long randomNumberBound) {
720		if (streamSize < 0L)
721	<	throw new IllegalArgumentException(BadSize);
721	>	throw new IllegalArgumentException(BAD_SIZE);
722		if (randomNumberOrigin >= randomNumberBound)
723	<	throw new IllegalArgumentException(BadRange);
723	>	throw new IllegalArgumentException(BAD_RANGE);
724		return StreamSupport.longStream
725		(new RandomLongsSpliterator
726		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 759 | Line 744 | public class SplittableRandom {
744		*/
745		public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
746		if (randomNumberOrigin >= randomNumberBound)
747	<	throw new IllegalArgumentException(BadRange);
747	>	throw new IllegalArgumentException(BAD_RANGE);
748		return StreamSupport.longStream
749		(new RandomLongsSpliterator
750		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 778 | Line 763 | public class SplittableRandom {
763		*/
764		public DoubleStream doubles(long streamSize) {
765		if (streamSize < 0L)
766	<	throw new IllegalArgumentException(BadSize);
766	>	throw new IllegalArgumentException(BAD_SIZE);
767		return StreamSupport.doubleStream
768		(new RandomDoublesSpliterator
769		(this, 0L, streamSize, Double.MAX_VALUE, 0.0),
#	Line 814 | Line 799 | public class SplittableRandom {
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
818	<	* @throws IllegalArgumentException if {@code randomNumberOrigin}
802	>	*         less than zero, or {@code randomNumberOrigin}
803		*         is greater than or equal to {@code randomNumberBound}
804		*/
805		public DoubleStream doubles(long streamSize, double randomNumberOrigin,
806		double randomNumberBound) {
807		if (streamSize < 0L)
808	<	throw new IllegalArgumentException(BadSize);
808	>	throw new IllegalArgumentException(BAD_SIZE);
809		if (!(randomNumberOrigin < randomNumberBound))
810	<	throw new IllegalArgumentException(BadRange);
810	>	throw new IllegalArgumentException(BAD_RANGE);
811		return StreamSupport.doubleStream
812		(new RandomDoublesSpliterator
813		(this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
#	Line 847 | Line 831 | public class SplittableRandom {
831		*/
832		public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
833		if (!(randomNumberOrigin < randomNumberBound))
834	<	throw new IllegalArgumentException(BadRange);
834	>	throw new IllegalArgumentException(BAD_RANGE);
835		return StreamSupport.doubleStream
836		(new RandomDoublesSpliterator
837		(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
#	Line 862 | Line 846 | public class SplittableRandom {
846		* approach. The long and double versions of this class are
847		* identical except for types.
848		*/
849	<	static final class RandomIntsSpliterator implements Spliterator.OfInt {
849	>	private static final class RandomIntsSpliterator
850	>	implements Spliterator.OfInt {
851		final SplittableRandom rng;
852		long index;
853		final long fence;
#	Line 917 | Line 902 | public class SplittableRandom {
902		/**
903		* Spliterator for long streams.
904		*/
905	<	static final class RandomLongsSpliterator implements Spliterator.OfLong {
905	>	private static final class RandomLongsSpliterator
906	>	implements Spliterator.OfLong {
907		final SplittableRandom rng;
908		long index;
909		final long fence;
#	Line 973 | Line 959 | public class SplittableRandom {
959		/**
960		* Spliterator for double streams.
961		*/
962	<	static final class RandomDoublesSpliterator implements Spliterator.OfDouble {
962	>	private static final class RandomDoublesSpliterator
963	>	implements Spliterator.OfDouble {
964		final SplittableRandom rng;
965		long index;
966		final long fence;

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