--- jsr166/src/main/java/util/SplittableRandom.java 2013/09/20 09:38:07 1.22 +++ jsr166/src/main/java/util/SplittableRandom.java 2016/11/12 03:15:13 1.34 @@ -25,17 +25,14 @@ package java.util; -import java.security.SecureRandom; -import java.net.NetworkInterface; -import java.util.Enumeration; import java.util.concurrent.atomic.AtomicLong; +import java.util.function.DoubleConsumer; import java.util.function.IntConsumer; import java.util.function.LongConsumer; -import java.util.function.DoubleConsumer; -import java.util.stream.StreamSupport; +import java.util.stream.DoubleStream; import java.util.stream.IntStream; import java.util.stream.LongStream; -import java.util.stream.DoubleStream; +import java.util.stream.StreamSupport; /** * A generator of uniform pseudorandom values applicable for use in @@ -55,15 +52,15 @@ import java.util.stream.DoubleStream; * types and ranges, but similar properties are expected to hold, at * least approximately, for others as well. The period * (length of any series of generated values before it repeats) is at - * least 264. + * least 264. * - *
  • Method {@link #split} constructs and returns a new + *
  • Method {@link #split} constructs and returns a new * SplittableRandom instance that shares no mutable state with the * current instance. However, with very high probability, the * values collectively generated by the two objects have the same * statistical properties as if the same quantity of values were * generated by a single thread using a single {@code - * SplittableRandom} object.
    • + * SplittableRandom} object. * *
  • Instances of SplittableRandom are not thread-safe. * They are designed to be split, not shared, across threads. For @@ -74,7 +71,7 @@ import java.util.stream.DoubleStream; * *
  • This class provides additional methods for generating random * streams, that employ the above techniques when used in {@code - * stream.parallel()} mode.
    • + * stream.parallel()} mode. * * * @@ -89,7 +86,7 @@ import java.util.stream.DoubleStream; * @author Doug Lea * @since 1.8 */ -public class SplittableRandom { +public final class SplittableRandom { /* * Implementation Overview. @@ -112,8 +109,8 @@ public class SplittableRandom { * For nextLong, the mix64 function is based on David Stafford's * (http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html) * "Mix13" variant of the "64-bit finalizer" function in Austin - * Appleby's MurmurHash3 algorithm See - * http://code.google.com/p/smhasher/wiki/MurmurHash3 . The mix32 + * Appleby's MurmurHash3 algorithm (see + * http://code.google.com/p/smhasher/wiki/MurmurHash3). The mix32 * function is based on Stafford's Mix04 mix function, but returns * the upper 32 bits cast as int. * @@ -142,11 +139,10 @@ public class SplittableRandom { * other cases, this split must be performed in a thread-safe * manner, so we use an AtomicLong to represent the seed rather * than use an explicit SplittableRandom. To bootstrap the - * defaultGen, we start off using a seed based on current time and - * network interface address unless the java.util.secureRandomSeed - * property is set. This serves as a slimmed-down (and insecure) - * variant of SecureRandom that also avoids stalls that may occur - * when using /dev/random. + * defaultGen, we start off using a seed based on current time + * unless the java.util.secureRandomSeed property is set. This + * serves as a slimmed-down (and insecure) variant of SecureRandom + * that also avoids stalls that may occur when using /dev/random. * * It is a relatively simple matter to apply the basic design here * to use 128 bit seeds. However, emulating 128bit arithmetic and @@ -168,7 +164,7 @@ public class SplittableRandom { * The least non-zero value returned by nextDouble(). This value * is scaled by a random value of 53 bits to produce a result. */ - private static final double DOUBLE_ULP = 1.0 / (1L << 53); + private static final double DOUBLE_UNIT = 0x1.0p-53; // 1.0 / (1L << 53); /** * The seed. Updated only via method nextSeed. @@ -192,16 +188,16 @@ public class SplittableRandom { * Computes Stafford variant 13 of 64bit mix function. */ private static long mix64(long z) { - z *= 0xbf58476d1ce4e5b9L; - z = (z ^ (z >>> 32)) * 0x94d049bb133111ebL; - return z ^ (z >>> 32); + z = (z ^ (z >>> 30)) * 0xbf58476d1ce4e5b9L; + z = (z ^ (z >>> 27)) * 0x94d049bb133111ebL; + return z ^ (z >>> 31); } /** * Returns the 32 high bits of Stafford variant 4 mix64 function as int. */ private static int mix32(long z) { - z *= 0x62a9d9ed799705f5L; + z = (z ^ (z >>> 33)) * 0x62a9d9ed799705f5L; return (int)(((z ^ (z >>> 28)) * 0xcb24d0a5c88c35b3L) >>> 32); } @@ -209,7 +205,7 @@ public class SplittableRandom { * Returns the gamma value to use for a new split instance. */ private static long mixGamma(long z) { - z *= 0xff51afd7ed558ccdL; // MurmurHash3 mix constants + z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL; // MurmurHash3 mix constants z = (z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L; z = (z ^ (z >>> 33)) | 1L; // force to be odd int n = Long.bitCount(z ^ (z >>> 1)); // ensure enough transitions @@ -223,58 +219,33 @@ public class SplittableRandom { return seed += gamma; } + // IllegalArgumentException messages + static final String BAD_BOUND = "bound must be positive"; + static final String BAD_RANGE = "bound must be greater than origin"; + static final String BAD_SIZE = "size must be non-negative"; + /** * The seed generator for default constructors. */ - private static final AtomicLong defaultGen = new AtomicLong(initialSeed()); - - private static long initialSeed() { - String pp = java.security.AccessController.doPrivileged( - new sun.security.action.GetPropertyAction( - "java.util.secureRandomSeed")); - if (pp != null && pp.equalsIgnoreCase("true")) { + private static final AtomicLong defaultGen + = new AtomicLong(mix64(System.currentTimeMillis()) ^ + mix64(System.nanoTime())); + + // at end of to survive static initialization circularity + static { + if (java.security.AccessController.doPrivileged( + new java.security.PrivilegedAction() { + public Boolean run() { + return Boolean.getBoolean("java.util.secureRandomSeed"); + }})) { byte[] seedBytes = java.security.SecureRandom.getSeed(8); - long s = (long)(seedBytes[0]) & 0xffL; + long s = (long)seedBytes[0] & 0xffL; for (int i = 1; i < 8; ++i) - s = (s << 8) | ((long)(seedBytes[i]) & 0xffL); - return s; + s = (s << 8) | ((long)seedBytes[i] & 0xffL); + defaultGen.set(s); } - long h = 0L; - try { - Enumeration ifcs = - NetworkInterface.getNetworkInterfaces(); - boolean retry = false; // retry once if getHardwareAddress is null - while (ifcs.hasMoreElements()) { - NetworkInterface ifc = ifcs.nextElement(); - if (!ifc.isVirtual()) { // skip fake addresses - byte[] bs = ifc.getHardwareAddress(); - if (bs != null) { - int n = bs.length; - int m = Math.min(n >>> 1, 4); - for (int i = 0; i < m; ++i) - h = (h << 16) ^ (bs[i] << 8) ^ bs[n-1-i]; - if (m < 4) - h = (h << 8) ^ bs[n-1-m]; - h = mix64(h); - break; - } - else if (!retry) - retry = true; - else - break; - } - } - } catch (Exception ignore) { - } - return (h ^ mix64(System.currentTimeMillis()) ^ - mix64(System.nanoTime())); } - // IllegalArgumentException messages - static final String BadBound = "bound must be positive"; - static final String BadRange = "bound must be greater than origin"; - static final String BadSize = "size must be non-negative"; - /* * Internal versions of nextX methods used by streams, as well as * the public nextX(origin, bound) methods. These exist mainly to @@ -375,7 +346,7 @@ public class SplittableRandom { * @return a pseudorandom value */ final double internalNextDouble(double origin, double bound) { - double r = (nextLong() >>> 11) * DOUBLE_ULP; + double r = (nextLong() >>> 11) * DOUBLE_UNIT; if (origin < bound) { r = r * (bound - origin) + origin; if (r >= bound) // correct for rounding @@ -404,7 +375,7 @@ public class SplittableRandom { * may, and typically does, vary across program invocations. */ public SplittableRandom() { // emulate defaultGen.split() - long s = defaultGen.getAndAdd(2*GOLDEN_GAMMA); + long s = defaultGen.getAndAdd(2 * GOLDEN_GAMMA); this.seed = mix64(s); this.gamma = mixGamma(s + GOLDEN_GAMMA); } @@ -447,7 +418,7 @@ public class SplittableRandom { */ public int nextInt(int bound) { if (bound <= 0) - throw new IllegalArgumentException(BadBound); + throw new IllegalArgumentException(BAD_BOUND); // Specialize internalNextInt for origin 0 int r = mix32(nextSeed()); int m = bound - 1; @@ -475,7 +446,7 @@ public class SplittableRandom { */ public int nextInt(int origin, int bound) { if (origin >= bound) - throw new IllegalArgumentException(BadRange); + throw new IllegalArgumentException(BAD_RANGE); return internalNextInt(origin, bound); } @@ -499,7 +470,7 @@ public class SplittableRandom { */ public long nextLong(long bound) { if (bound <= 0) - throw new IllegalArgumentException(BadBound); + throw new IllegalArgumentException(BAD_BOUND); // Specialize internalNextLong for origin 0 long r = mix64(nextSeed()); long m = bound - 1; @@ -527,7 +498,7 @@ public class SplittableRandom { */ public long nextLong(long origin, long bound) { if (origin >= bound) - throw new IllegalArgumentException(BadRange); + throw new IllegalArgumentException(BAD_RANGE); return internalNextLong(origin, bound); } @@ -539,7 +510,7 @@ public class SplittableRandom { * (inclusive) and one (exclusive) */ public double nextDouble() { - return (mix64(nextSeed()) >>> 11) * DOUBLE_ULP; + return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT; } /** @@ -553,13 +524,27 @@ public class SplittableRandom { */ public double nextDouble(double bound) { if (!(bound > 0.0)) - throw new IllegalArgumentException(BadBound); - double result = (mix64(nextSeed()) >>> 11) * DOUBLE_ULP * bound; + throw new IllegalArgumentException(BAD_BOUND); + double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound; return (result < bound) ? result : // correct for rounding Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1); } /** + * Generates a pseudorandom number with the indicated number of + * bits. Unlike in superclass @{link Random}, this method is never + * internally called or used by any other publicly accessible + * method. + * + * @param bits random bits + * @return the next pseudorandom value from this random number + * generator's sequence + */ + protected int next(int bits) { + return (int)(nextLong() >>> (64 - bits)); + } + + /** * Returns a pseudorandom {@code double} value between the specified * origin (inclusive) and bound (exclusive). * @@ -572,7 +557,7 @@ public class SplittableRandom { */ public double nextDouble(double origin, double bound) { if (!(origin < bound)) - throw new IllegalArgumentException(BadRange); + throw new IllegalArgumentException(BAD_RANGE); return internalNextDouble(origin, bound); } @@ -600,7 +585,7 @@ public class SplittableRandom { */ public IntStream ints(long streamSize) { if (streamSize < 0L) - throw new IllegalArgumentException(BadSize); + throw new IllegalArgumentException(BAD_SIZE); return StreamSupport.intStream (new RandomIntsSpliterator (this, 0L, streamSize, Integer.MAX_VALUE, 0), @@ -641,9 +626,9 @@ public class SplittableRandom { public IntStream ints(long streamSize, int randomNumberOrigin, int randomNumberBound) { if (streamSize < 0L) - throw new IllegalArgumentException(BadSize); + throw new IllegalArgumentException(BAD_SIZE); if (randomNumberOrigin >= randomNumberBound) - throw new IllegalArgumentException(BadRange); + throw new IllegalArgumentException(BAD_RANGE); return StreamSupport.intStream (new RandomIntsSpliterator (this, 0L, streamSize, randomNumberOrigin, randomNumberBound), @@ -667,7 +652,7 @@ public class SplittableRandom { */ public IntStream ints(int randomNumberOrigin, int randomNumberBound) { if (randomNumberOrigin >= randomNumberBound) - throw new IllegalArgumentException(BadRange); + throw new IllegalArgumentException(BAD_RANGE); return StreamSupport.intStream (new RandomIntsSpliterator (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), @@ -686,7 +671,7 @@ public class SplittableRandom { */ public LongStream longs(long streamSize) { if (streamSize < 0L) - throw new IllegalArgumentException(BadSize); + throw new IllegalArgumentException(BAD_SIZE); return StreamSupport.longStream (new RandomLongsSpliterator (this, 0L, streamSize, Long.MAX_VALUE, 0L), @@ -727,9 +712,9 @@ public class SplittableRandom { public LongStream longs(long streamSize, long randomNumberOrigin, long randomNumberBound) { if (streamSize < 0L) - throw new IllegalArgumentException(BadSize); + throw new IllegalArgumentException(BAD_SIZE); if (randomNumberOrigin >= randomNumberBound) - throw new IllegalArgumentException(BadRange); + throw new IllegalArgumentException(BAD_RANGE); return StreamSupport.longStream (new RandomLongsSpliterator (this, 0L, streamSize, randomNumberOrigin, randomNumberBound), @@ -753,7 +738,7 @@ public class SplittableRandom { */ public LongStream longs(long randomNumberOrigin, long randomNumberBound) { if (randomNumberOrigin >= randomNumberBound) - throw new IllegalArgumentException(BadRange); + throw new IllegalArgumentException(BAD_RANGE); return StreamSupport.longStream (new RandomLongsSpliterator (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), @@ -772,7 +757,7 @@ public class SplittableRandom { */ public DoubleStream doubles(long streamSize) { if (streamSize < 0L) - throw new IllegalArgumentException(BadSize); + throw new IllegalArgumentException(BAD_SIZE); return StreamSupport.doubleStream (new RandomDoublesSpliterator (this, 0L, streamSize, Double.MAX_VALUE, 0.0), @@ -815,9 +800,9 @@ public class SplittableRandom { public DoubleStream doubles(long streamSize, double randomNumberOrigin, double randomNumberBound) { if (streamSize < 0L) - throw new IllegalArgumentException(BadSize); + throw new IllegalArgumentException(BAD_SIZE); if (!(randomNumberOrigin < randomNumberBound)) - throw new IllegalArgumentException(BadRange); + throw new IllegalArgumentException(BAD_RANGE); return StreamSupport.doubleStream (new RandomDoublesSpliterator (this, 0L, streamSize, randomNumberOrigin, randomNumberBound), @@ -841,7 +826,7 @@ public class SplittableRandom { */ public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) { if (!(randomNumberOrigin < randomNumberBound)) - throw new IllegalArgumentException(BadRange); + throw new IllegalArgumentException(BAD_RANGE); return StreamSupport.doubleStream (new RandomDoublesSpliterator (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), @@ -856,7 +841,8 @@ public class SplittableRandom { * approach. The long and double versions of this class are * identical except for types. */ - static final class RandomIntsSpliterator implements Spliterator.OfInt { + private static final class RandomIntsSpliterator + implements Spliterator.OfInt { final SplittableRandom rng; long index; final long fence; @@ -911,7 +897,8 @@ public class SplittableRandom { /** * Spliterator for long streams. */ - static final class RandomLongsSpliterator implements Spliterator.OfLong { + private static final class RandomLongsSpliterator + implements Spliterator.OfLong { final SplittableRandom rng; long index; final long fence; @@ -967,7 +954,8 @@ public class SplittableRandom { /** * Spliterator for double streams. */ - static final class RandomDoublesSpliterator implements Spliterator.OfDouble { + private static final class RandomDoublesSpliterator + implements Spliterator.OfDouble { final SplittableRandom rng; long index; final long fence;