25 |
|
|
26 |
|
package java.util; |
27 |
|
|
28 |
+ |
import java.security.SecureRandom; |
29 |
+ |
import java.net.NetworkInterface; |
30 |
+ |
import java.util.Enumeration; |
31 |
|
import java.util.concurrent.atomic.AtomicLong; |
29 |
– |
import java.util.Spliterator; |
32 |
|
import java.util.function.IntConsumer; |
33 |
|
import java.util.function.LongConsumer; |
34 |
|
import java.util.function.DoubleConsumer; |
40 |
|
/** |
41 |
|
* A generator of uniform pseudorandom values applicable for use in |
42 |
|
* (among other contexts) isolated parallel computations that may |
43 |
< |
* generate subtasks. Class SplittableRandom supports methods for |
43 |
> |
* generate subtasks. Class {@code SplittableRandom} supports methods for |
44 |
|
* producing pseudorandom numbers of type {@code int}, {@code long}, |
45 |
|
* and {@code double} with similar usages as for class |
46 |
|
* {@link java.util.Random} but differs in the following ways: |
53 |
|
* href="http://www.phy.duke.edu/~rgb/General/dieharder.php"> version |
54 |
|
* 3.31.1</a>.) These tests validate only the methods for certain |
55 |
|
* types and ranges, but similar properties are expected to hold, at |
56 |
< |
* least approximately, for others as well. </li> |
56 |
> |
* least approximately, for others as well. The <em>period</em> |
57 |
> |
* (length of any series of generated values before it repeats) is at |
58 |
> |
* least 2<sup>64</sup>. </li> |
59 |
|
* |
60 |
|
* <li> Method {@link #split} constructs and returns a new |
61 |
|
* SplittableRandom instance that shares no mutable state with the |
78 |
|
* |
79 |
|
* </ul> |
80 |
|
* |
81 |
+ |
* <p>Instances of {@code SplittableRandom} are not cryptographically |
82 |
+ |
* secure. Consider instead using {@link java.security.SecureRandom} |
83 |
+ |
* in security-sensitive applications. Additionally, |
84 |
+ |
* default-constructed instances do not use a cryptographically random |
85 |
+ |
* seed unless the {@linkplain System#getProperty system property} |
86 |
+ |
* {@code java.util.secureRandomSeed} is set to {@code true}. |
87 |
+ |
* |
88 |
|
* @author Guy Steele |
89 |
|
* @author Doug Lea |
90 |
|
* @since 1.8 |
92 |
|
public class SplittableRandom { |
93 |
|
|
94 |
|
/* |
84 |
– |
* File organization: First the non-public methods that constitute |
85 |
– |
* the main algorithm, then the main public methods, followed by |
86 |
– |
* some custom spliterator classes needed for stream methods. |
87 |
– |
* |
88 |
– |
* Credits: Primary algorithm and code by Guy Steele. Stream |
89 |
– |
* support methods by Doug Lea. Documentation jointly produced |
90 |
– |
* with additional help from Brian Goetz. |
91 |
– |
*/ |
92 |
– |
|
93 |
– |
/* |
95 |
|
* Implementation Overview. |
96 |
|
* |
97 |
|
* This algorithm was inspired by the "DotMix" algorithm by |
98 |
|
* Leiserson, Schardl, and Sukha "Deterministic Parallel |
99 |
|
* Random-Number Generation for Dynamic-Multithreading Platforms", |
100 |
< |
* PPoPP 2012, but improves and extends it in several ways. |
100 |
> |
* PPoPP 2012, as well as those in "Parallel random numbers: as |
101 |
> |
* easy as 1, 2, 3" by Salmon, Morae, Dror, and Shaw, SC 2011. It |
102 |
> |
* differs mainly in simplifying and cheapening operations. |
103 |
> |
* |
104 |
> |
* The primary update step (method nextSeed()) is to add a |
105 |
> |
* constant ("gamma") to the current (64 bit) seed, forming a |
106 |
> |
* simple sequence. The seed and the gamma values for any two |
107 |
> |
* SplittableRandom instances are highly likely to be different. |
108 |
> |
* |
109 |
> |
* Methods nextLong, nextInt, and derivatives do not return the |
110 |
> |
* sequence (seed) values, but instead a hash-like bit-mix of |
111 |
> |
* their bits, producing more independently distributed sequences. |
112 |
> |
* For nextLong, the mix64 function is based on David Stafford's |
113 |
> |
* (http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html) |
114 |
> |
* "Mix13" variant of the "64-bit finalizer" function in Austin |
115 |
> |
* Appleby's MurmurHash3 algorithm See |
116 |
> |
* http://code.google.com/p/smhasher/wiki/MurmurHash3 . The mix32 |
117 |
> |
* function is based on Stafford's Mix04 mix function, but returns |
118 |
> |
* the upper 32 bits cast as int. |
119 |
> |
* |
120 |
> |
* The split operation uses the current generator to form the seed |
121 |
> |
* and gamma for another SplittableRandom. To conservatively |
122 |
> |
* avoid potential correlations between seed and value generation, |
123 |
> |
* gamma selection (method mixGamma) uses different |
124 |
> |
* (Murmurhash3's) mix constants. To avoid potential weaknesses |
125 |
> |
* in bit-mixing transformations, we restrict gammas to odd values |
126 |
> |
* with at least 24 0-1 or 1-0 bit transitions. Rather than |
127 |
> |
* rejecting candidates with too few or too many bits set, method |
128 |
> |
* mixGamma flips some bits (which has the effect of mapping at |
129 |
> |
* most 4 to any given gamma value). This reduces the effective |
130 |
> |
* set of 64bit odd gamma values by about 2%, and serves as an |
131 |
> |
* automated screening for sequence constant selection that is |
132 |
> |
* left as an empirical decision in some other hashing and crypto |
133 |
> |
* algorithms. |
134 |
> |
* |
135 |
> |
* The resulting generator thus transforms a sequence in which |
136 |
> |
* (typically) many bits change on each step, with an inexpensive |
137 |
> |
* mixer with good (but less than cryptographically secure) |
138 |
> |
* avalanching. |
139 |
> |
* |
140 |
> |
* The default (no-argument) constructor, in essence, invokes |
141 |
> |
* split() for a common "defaultGen" SplittableRandom. Unlike |
142 |
> |
* other cases, this split must be performed in a thread-safe |
143 |
> |
* manner, so we use an AtomicLong to represent the seed rather |
144 |
> |
* than use an explicit SplittableRandom. To bootstrap the |
145 |
> |
* defaultGen, we start off using a seed based on current time and |
146 |
> |
* network interface address unless the java.util.secureRandomSeed |
147 |
> |
* property is set. This serves as a slimmed-down (and insecure) |
148 |
> |
* variant of SecureRandom that also avoids stalls that may occur |
149 |
> |
* when using /dev/random. |
150 |
> |
* |
151 |
> |
* It is a relatively simple matter to apply the basic design here |
152 |
> |
* to use 128 bit seeds. However, emulating 128bit arithmetic and |
153 |
> |
* carrying around twice the state add more overhead than appears |
154 |
> |
* warranted for current usages. |
155 |
|
* |
156 |
< |
* The primary update step (see method nextSeed()) is simply to |
157 |
< |
* add a constant ("gamma") to the current seed, modulo a prime |
158 |
< |
* ("George"). However, the nextLong and nextInt methods do not |
104 |
< |
* return this value, but instead the results of bit-mixing |
105 |
< |
* transformations that produce more uniformly distributed |
106 |
< |
* sequences. |
107 |
< |
* |
108 |
< |
* "George" is the otherwise nameless (because it cannot be |
109 |
< |
* represented) prime number 2^64+13. Using a prime number larger |
110 |
< |
* than can fit in a long ensures that all possible long values |
111 |
< |
* can occur, plus 13 others that just get skipped over when they |
112 |
< |
* are encountered; see method addGammaModGeorge. For this to |
113 |
< |
* work, initial gamma values must be at least 13. |
114 |
< |
* |
115 |
< |
* The value of gamma differs for each instance across a series of |
116 |
< |
* splits, and is generated using a slightly stripped-down variant |
117 |
< |
* of the same algorithm, but operating across calls to split(), |
118 |
< |
* not calls to nextSeed(): Each instance carries the state of |
119 |
< |
* this generator as nextSplit, and uses mix64(nextSplit) as its |
120 |
< |
* own gamma value. Computations of gammas themselves use a fixed |
121 |
< |
* constant as the second argument to the addGammaModGeorge |
122 |
< |
* function, GAMMA_GAMMA, a "genuinely random" number from a |
123 |
< |
* radioactive decay reading (obtained from |
124 |
< |
* http://www.fourmilab.ch/hotbits/) meeting the above range |
125 |
< |
* constraint. Using a fixed constant maintains the invariant that |
126 |
< |
* the value of gamma is the same for every instance that is at |
127 |
< |
* the same split-distance from their common root. (Note: there is |
128 |
< |
* nothing especially magic about obtaining this constant from a |
129 |
< |
* "truly random" physical source rather than just choosing one |
130 |
< |
* arbitrarily; using "hotbits" was merely an aesthetically pleasing |
131 |
< |
* choice. In either case, good statistical behavior of the |
132 |
< |
* algorithm should be, and was, verified by using the DieHarder |
133 |
< |
* test suite.) |
134 |
< |
* |
135 |
< |
* The mix64 bit-mixing function called by nextLong and other |
136 |
< |
* methods computes the same value as the "64-bit finalizer" |
137 |
< |
* function in Austin Appleby's MurmurHash3 algorithm. See |
138 |
< |
* http://code.google.com/p/smhasher/wiki/MurmurHash3 , which |
139 |
< |
* comments: "The constants for the finalizers were generated by a |
140 |
< |
* simple simulated-annealing algorithm, and both avalanche all |
141 |
< |
* bits of 'h' to within 0.25% bias." It also appears to work to |
142 |
< |
* use instead any of the variants proposed by David Stafford at |
143 |
< |
* http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html |
144 |
< |
* but these variants have not yet been tested as thoroughly |
145 |
< |
* in the context of the implementation of SplittableRandom. |
146 |
< |
* |
147 |
< |
* The mix32 function used for nextInt just consists of two of the |
148 |
< |
* five lines of mix64; avalanche testing shows that the 64-bit result |
149 |
< |
* has its top 32 bits avalanched well, though not the bottom 32 bits. |
150 |
< |
* DieHarder tests show that it is adequate for generating one |
151 |
< |
* random int from the 64-bit result of nextSeed. |
152 |
< |
* |
153 |
< |
* Support for the default (no-argument) constructor relies on an |
154 |
< |
* AtomicLong (defaultSeedGenerator) to help perform the |
155 |
< |
* equivalent of a split of a statically constructed |
156 |
< |
* SplittableRandom. Unlike other cases, this split must be |
157 |
< |
* performed in a thread-safe manner. We use |
158 |
< |
* AtomicLong.compareAndSet as the (typically) most efficient |
159 |
< |
* mechanism. To bootstrap, we start off using System.nanotime(), |
160 |
< |
* and update using another "genuinely random" constant |
161 |
< |
* DEFAULT_SEED_GAMMA. The default constructor uses GAMMA_GAMMA, |
162 |
< |
* not 0, for its splitSeed argument (addGammaModGeorge(0, |
163 |
< |
* GAMMA_GAMMA) == GAMMA_GAMMA) to reflect that each is split from |
164 |
< |
* this root generator, even though the root is not explicitly |
165 |
< |
* represented as a SplittableRandom. |
166 |
< |
*/ |
167 |
< |
|
168 |
< |
/** |
169 |
< |
* The "genuinely random" value for producing new gamma values. |
170 |
< |
* The value is arbitrary, subject to the requirement that it be |
171 |
< |
* greater or equal to 13. |
172 |
< |
*/ |
173 |
< |
private static final long GAMMA_GAMMA = 0xF2281E2DBA6606F3L; |
174 |
< |
|
175 |
< |
/** |
176 |
< |
* The "genuinely random" seed update value for default constructors. |
177 |
< |
* The value is arbitrary, subject to the requirement that it be |
178 |
< |
* greater or equal to 13. |
156 |
> |
* File organization: First the non-public methods that constitute |
157 |
> |
* the main algorithm, then the main public methods, followed by |
158 |
> |
* some custom spliterator classes needed for stream methods. |
159 |
|
*/ |
180 |
– |
private static final long DEFAULT_SEED_GAMMA = 0xBD24B73A95FB84D9L; |
160 |
|
|
161 |
|
/** |
162 |
< |
* The least non-zero value returned by nextDouble(). This value |
163 |
< |
* is scaled by a random value of 53 bits to produce a result. |
162 |
> |
* The golden ratio scaled to 64bits, used as the initial gamma |
163 |
> |
* value for (unsplit) SplittableRandoms. |
164 |
|
*/ |
165 |
< |
private static final double DOUBLE_UNIT = 1.0 / (1L << 53); |
165 |
> |
private static final long GOLDEN_GAMMA = 0x9e3779b97f4a7c15L; |
166 |
|
|
167 |
|
/** |
168 |
< |
* The next seed for default constructors. |
168 |
> |
* The least non-zero value returned by nextDouble(). This value |
169 |
> |
* is scaled by a random value of 53 bits to produce a result. |
170 |
|
*/ |
171 |
< |
private static final AtomicLong defaultSeedGenerator = |
192 |
< |
new AtomicLong(System.nanoTime()); |
171 |
> |
private static final double DOUBLE_ULP = 1.0 / (1L << 53); |
172 |
|
|
173 |
|
/** |
174 |
< |
* The seed, updated only via method nextSeed. |
174 |
> |
* The seed. Updated only via method nextSeed. |
175 |
|
*/ |
176 |
|
private long seed; |
177 |
|
|
178 |
|
/** |
179 |
< |
* The constant value added to seed (mod George) on each update. |
179 |
> |
* The step value. |
180 |
|
*/ |
181 |
|
private final long gamma; |
182 |
|
|
183 |
|
/** |
184 |
< |
* The next seed to use for splits. Propagated using |
206 |
< |
* addGammaModGeorge across instances. |
184 |
> |
* Internal constructor used by all others except default constructor. |
185 |
|
*/ |
186 |
< |
private final long nextSplit; |
187 |
< |
|
188 |
< |
/** |
211 |
< |
* Adds the given gamma value, g, to the given seed value s, mod |
212 |
< |
* George (2^64+13). We regard s and g as unsigned values |
213 |
< |
* (ranging from 0 to 2^64-1). We add g to s either once or twice |
214 |
< |
* (mod George) as necessary to produce an (unsigned) result less |
215 |
< |
* than 2^64. We require that g must be at least 13. This |
216 |
< |
* guarantees that if (s+g) mod George >= 2^64 then (s+g+g) mod |
217 |
< |
* George < 2^64; thus we need only a conditional, not a loop, |
218 |
< |
* to be sure of getting a representable value. |
219 |
< |
* |
220 |
< |
* @param s a seed value |
221 |
< |
* @param g a gamma value, 13 <= g (as unsigned) |
222 |
< |
*/ |
223 |
< |
private static long addGammaModGeorge(long s, long g) { |
224 |
< |
long p = s + g; |
225 |
< |
if (Long.compareUnsigned(p, g) >= 0) |
226 |
< |
return p; |
227 |
< |
long q = p - 13L; |
228 |
< |
return (Long.compareUnsigned(p, 13L) >= 0) ? q : (q + g); |
186 |
> |
private SplittableRandom(long seed, long gamma) { |
187 |
> |
this.seed = seed; |
188 |
> |
this.gamma = gamma; |
189 |
|
} |
190 |
|
|
191 |
|
/** |
192 |
< |
* Returns a bit-mixed transformation of its argument. |
233 |
< |
* See above for explanation. |
192 |
> |
* Computes Stafford variant 13 of 64bit mix function. |
193 |
|
*/ |
194 |
|
private static long mix64(long z) { |
195 |
< |
z ^= (z >>> 33); |
196 |
< |
z *= 0xff51afd7ed558ccdL; |
197 |
< |
z ^= (z >>> 33); |
198 |
< |
z *= 0xc4ceb9fe1a85ec53L; |
199 |
< |
z ^= (z >>> 33); |
200 |
< |
return z; |
195 |
> |
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; |
202 |
> |
z = (z ^ (z >>> 27)) * 0x94d049bb133111ebL; |
203 |
> |
return z ^ (z >>> 31); |
204 |
|
} |
205 |
|
|
206 |
|
/** |
207 |
< |
* Returns a bit-mixed int transformation of its argument. |
246 |
< |
* See above for explanation. |
207 |
> |
* Returns the 32 high bits of Stafford variant 4 mix64 function as int. |
208 |
|
*/ |
209 |
|
private static int mix32(long z) { |
210 |
< |
z ^= (z >>> 33); |
211 |
< |
z *= 0xc4ceb9fe1a85ec53L; |
251 |
< |
return (int)(z >>> 32); |
210 |
> |
z *= 0x62a9d9ed799705f5L; |
211 |
> |
return (int)(((z ^ (z >>> 28)) * 0xcb24d0a5c88c35b3L) >>> 32); |
212 |
|
} |
213 |
|
|
214 |
|
/** |
215 |
< |
* Internal constructor used by all other constructors and by |
256 |
< |
* method split. Establishes the initial seed for this instance, |
257 |
< |
* and uses the given splitSeed to establish gamma, as well as the |
258 |
< |
* nextSplit to use by this instance. The loop to skip ineligible |
259 |
< |
* gammas very rarely iterates, and does so at most 13 times. |
215 |
> |
* Returns the gamma value to use for a new split instance. |
216 |
|
*/ |
217 |
< |
private SplittableRandom(long seed, long splitSeed) { |
218 |
< |
this.seed = seed; |
219 |
< |
long s = splitSeed, g; |
220 |
< |
do { // ensure gamma >= 13, considered as an unsigned integer |
221 |
< |
s = addGammaModGeorge(s, GAMMA_GAMMA); |
222 |
< |
g = mix64(s); |
267 |
< |
} while (Long.compareUnsigned(g, 13L) < 0); |
268 |
< |
this.gamma = g; |
269 |
< |
this.nextSplit = s; |
217 |
> |
private static long mixGamma(long z) { |
218 |
> |
z *= 0xff51afd7ed558ccdL; // MurmurHash3 mix constants |
219 |
> |
z = (z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L; |
220 |
> |
z = (z ^ (z >>> 33)) | 1L; // force to be odd |
221 |
> |
int n = Long.bitCount(z ^ (z >>> 1)); // ensure enough transitions |
222 |
> |
return (n < 24) ? z ^ 0xaaaaaaaaaaaaaaaaL : z; |
223 |
|
} |
224 |
|
|
225 |
|
/** |
226 |
< |
* Updates in-place and returns seed. |
274 |
< |
* See above for explanation. |
226 |
> |
* Adds gamma to seed. |
227 |
|
*/ |
228 |
|
private long nextSeed() { |
229 |
< |
return seed = addGammaModGeorge(seed, gamma); |
229 |
> |
return seed += gamma; |
230 |
|
} |
231 |
|
|
232 |
|
/** |
233 |
< |
* Atomically updates and returns next seed for default constructor. |
233 |
> |
* The seed generator for default constructors. |
234 |
|
*/ |
235 |
< |
private static long nextDefaultSeed() { |
236 |
< |
long oldSeed, newSeed; |
237 |
< |
do { |
238 |
< |
oldSeed = defaultSeedGenerator.get(); |
239 |
< |
newSeed = addGammaModGeorge(oldSeed, DEFAULT_SEED_GAMMA); |
240 |
< |
} while (!defaultSeedGenerator.compareAndSet(oldSeed, newSeed)); |
241 |
< |
return mix64(newSeed); |
235 |
> |
private static final AtomicLong defaultGen = new AtomicLong(initialSeed()); |
236 |
> |
|
237 |
> |
private static long initialSeed() { |
238 |
> |
String pp = java.security.AccessController.doPrivileged( |
239 |
> |
new sun.security.action.GetPropertyAction( |
240 |
> |
"java.util.secureRandomSeed")); |
241 |
> |
if (pp != null && pp.equalsIgnoreCase("true")) { |
242 |
> |
byte[] seedBytes = java.security.SecureRandom.getSeed(8); |
243 |
> |
long s = (long)(seedBytes[0]) & 0xffL; |
244 |
> |
for (int i = 1; i < 8; ++i) |
245 |
> |
s = (s << 8) | ((long)(seedBytes[i]) & 0xffL); |
246 |
> |
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) { |
274 |
> |
} |
275 |
> |
return (h ^ mix64(System.currentTimeMillis()) ^ |
276 |
> |
mix64(System.nanoTime())); |
277 |
|
} |
278 |
|
|
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 |
+ |
|
284 |
|
/* |
285 |
|
* Internal versions of nextX methods used by streams, as well as |
286 |
|
* the public nextX(origin, bound) methods. These exist mainly to |
356 |
|
int r = mix32(nextSeed()); |
357 |
|
if (origin < bound) { |
358 |
|
int n = bound - origin, m = n - 1; |
359 |
< |
if ((n & m) == 0L) |
359 |
> |
if ((n & m) == 0) |
360 |
|
r = (r & m) + origin; |
361 |
|
else if (n > 0) { |
362 |
|
for (int u = r >>> 1; |
381 |
|
* @return a pseudorandom value |
382 |
|
*/ |
383 |
|
final double internalNextDouble(double origin, double bound) { |
384 |
< |
double r = (nextLong() >>> 11) * DOUBLE_UNIT; |
384 |
> |
double r = (nextLong() >>> 11) * DOUBLE_ULP; |
385 |
|
if (origin < bound) { |
386 |
|
r = r * (bound - origin) + origin; |
387 |
|
if (r >= bound) // correct for rounding |
395 |
|
/** |
396 |
|
* Creates a new SplittableRandom instance using the specified |
397 |
|
* initial seed. SplittableRandom instances created with the same |
398 |
< |
* seed generate identical sequences of values. |
398 |
> |
* seed in the same program generate identical sequences of values. |
399 |
|
* |
400 |
|
* @param seed the initial seed |
401 |
|
*/ |
402 |
|
public SplittableRandom(long seed) { |
403 |
< |
this(seed, 0); |
403 |
> |
this(seed, GOLDEN_GAMMA); |
404 |
|
} |
405 |
|
|
406 |
|
/** |
409 |
|
* of those of any other instances in the current program; and |
410 |
|
* may, and typically does, vary across program invocations. |
411 |
|
*/ |
412 |
< |
public SplittableRandom() { |
413 |
< |
this(nextDefaultSeed(), GAMMA_GAMMA); |
412 |
> |
public SplittableRandom() { // emulate defaultGen.split() |
413 |
> |
long s = defaultGen.getAndAdd(2*GOLDEN_GAMMA); |
414 |
> |
this.seed = mix64(s); |
415 |
> |
this.gamma = mixGamma(s + GOLDEN_GAMMA); |
416 |
|
} |
417 |
|
|
418 |
|
/** |
430 |
|
* @return the new SplittableRandom instance |
431 |
|
*/ |
432 |
|
public SplittableRandom split() { |
433 |
< |
return new SplittableRandom(nextSeed(), nextSplit); |
433 |
> |
return new SplittableRandom(nextLong(), mixGamma(nextSeed())); |
434 |
|
} |
435 |
|
|
436 |
|
/** |
446 |
|
* Returns a pseudorandom {@code int} value between zero (inclusive) |
447 |
|
* and the specified bound (exclusive). |
448 |
|
* |
449 |
< |
* @param bound the bound on the random number to be returned. Must be |
456 |
< |
* positive. |
449 |
> |
* @param bound the upper bound (exclusive). Must be positive. |
450 |
|
* @return a pseudorandom {@code int} value between zero |
451 |
|
* (inclusive) and the bound (exclusive) |
452 |
< |
* @throws IllegalArgumentException if the bound is less than zero |
452 |
> |
* @throws IllegalArgumentException if {@code bound} is not positive |
453 |
|
*/ |
454 |
|
public int nextInt(int bound) { |
455 |
|
if (bound <= 0) |
456 |
< |
throw new IllegalArgumentException("bound must be positive"); |
456 |
> |
throw new IllegalArgumentException(BadBound); |
457 |
|
// Specialize internalNextInt for origin 0 |
458 |
|
int r = mix32(nextSeed()); |
459 |
|
int m = bound - 1; |
460 |
< |
if ((bound & m) == 0L) // power of two |
460 |
> |
if ((bound & m) == 0) // power of two |
461 |
|
r &= m; |
462 |
|
else { // reject over-represented candidates |
463 |
|
for (int u = r >>> 1; |
481 |
|
*/ |
482 |
|
public int nextInt(int origin, int bound) { |
483 |
|
if (origin >= bound) |
484 |
< |
throw new IllegalArgumentException("bound must be greater than origin"); |
484 |
> |
throw new IllegalArgumentException(BadRange); |
485 |
|
return internalNextInt(origin, bound); |
486 |
|
} |
487 |
|
|
498 |
|
* Returns a pseudorandom {@code long} value between zero (inclusive) |
499 |
|
* and the specified bound (exclusive). |
500 |
|
* |
501 |
< |
* @param bound the bound on the random number to be returned. Must be |
509 |
< |
* positive. |
501 |
> |
* @param bound the upper bound (exclusive). Must be positive. |
502 |
|
* @return a pseudorandom {@code long} value between zero |
503 |
|
* (inclusive) and the bound (exclusive) |
504 |
< |
* @throws IllegalArgumentException if {@code bound} is less than zero |
504 |
> |
* @throws IllegalArgumentException if {@code bound} is not positive |
505 |
|
*/ |
506 |
|
public long nextLong(long bound) { |
507 |
|
if (bound <= 0) |
508 |
< |
throw new IllegalArgumentException("bound must be positive"); |
508 |
> |
throw new IllegalArgumentException(BadBound); |
509 |
|
// Specialize internalNextLong for origin 0 |
510 |
|
long r = mix64(nextSeed()); |
511 |
|
long m = bound - 1; |
533 |
|
*/ |
534 |
|
public long nextLong(long origin, long bound) { |
535 |
|
if (origin >= bound) |
536 |
< |
throw new IllegalArgumentException("bound must be greater than origin"); |
536 |
> |
throw new IllegalArgumentException(BadRange); |
537 |
|
return internalNextLong(origin, bound); |
538 |
|
} |
539 |
|
|
542 |
|
* (inclusive) and one (exclusive). |
543 |
|
* |
544 |
|
* @return a pseudorandom {@code double} value between zero |
545 |
< |
* (inclusive) and one (exclusive) |
545 |
> |
* (inclusive) and one (exclusive) |
546 |
|
*/ |
547 |
|
public double nextDouble() { |
548 |
< |
return (nextLong() >>> 11) * DOUBLE_UNIT; |
548 |
> |
return (mix64(nextSeed()) >>> 11) * DOUBLE_ULP; |
549 |
|
} |
550 |
|
|
551 |
|
/** |
552 |
|
* Returns a pseudorandom {@code double} value between 0.0 |
553 |
|
* (inclusive) and the specified bound (exclusive). |
554 |
|
* |
555 |
< |
* @param bound the bound on the random number to be returned. Must be |
564 |
< |
* positive. |
555 |
> |
* @param bound the upper bound (exclusive). Must be positive. |
556 |
|
* @return a pseudorandom {@code double} value between zero |
557 |
|
* (inclusive) and the bound (exclusive) |
558 |
< |
* @throws IllegalArgumentException if {@code bound} is less than zero |
558 |
> |
* @throws IllegalArgumentException if {@code bound} is not positive |
559 |
|
*/ |
560 |
|
public double nextDouble(double bound) { |
561 |
|
if (!(bound > 0.0)) |
562 |
< |
throw new IllegalArgumentException("bound must be positive"); |
563 |
< |
double result = nextDouble() * bound; |
562 |
> |
throw new IllegalArgumentException(BadBound); |
563 |
> |
double result = (mix64(nextSeed()) >>> 11) * DOUBLE_ULP * bound; |
564 |
|
return (result < bound) ? result : // correct for rounding |
565 |
|
Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1); |
566 |
|
} |
570 |
|
* origin (inclusive) and bound (exclusive). |
571 |
|
* |
572 |
|
* @param origin the least value returned |
573 |
< |
* @param bound the upper bound |
573 |
> |
* @param bound the upper bound (exclusive) |
574 |
|
* @return a pseudorandom {@code double} value between the origin |
575 |
|
* (inclusive) and the bound (exclusive) |
576 |
|
* @throws IllegalArgumentException if {@code origin} is greater than |
578 |
|
*/ |
579 |
|
public double nextDouble(double origin, double bound) { |
580 |
|
if (!(origin < bound)) |
581 |
< |
throw new IllegalArgumentException("bound must be greater than origin"); |
581 |
> |
throw new IllegalArgumentException(BadRange); |
582 |
|
return internalNextDouble(origin, bound); |
583 |
|
} |
584 |
|
|
585 |
+ |
/** |
586 |
+ |
* Returns a pseudorandom {@code boolean} value. |
587 |
+ |
* |
588 |
+ |
* @return a pseudorandom {@code boolean} value |
589 |
+ |
*/ |
590 |
+ |
public boolean nextBoolean() { |
591 |
+ |
return mix32(nextSeed()) < 0; |
592 |
+ |
} |
593 |
+ |
|
594 |
|
// stream methods, coded in a way intended to better isolate for |
595 |
|
// maintenance purposes the small differences across forms. |
596 |
|
|
597 |
|
/** |
598 |
< |
* Returns a stream producing the given {@code streamSize} number of |
599 |
< |
* pseudorandom {@code int} values. |
598 |
> |
* Returns a stream producing the given {@code streamSize} number |
599 |
> |
* of pseudorandom {@code int} values from this generator and/or |
600 |
> |
* one split from it. |
601 |
|
* |
602 |
|
* @param streamSize the number of values to generate |
603 |
|
* @return a stream of pseudorandom {@code int} values |
606 |
|
*/ |
607 |
|
public IntStream ints(long streamSize) { |
608 |
|
if (streamSize < 0L) |
609 |
< |
throw new IllegalArgumentException("negative Stream size"); |
609 |
> |
throw new IllegalArgumentException(BadSize); |
610 |
|
return StreamSupport.intStream |
611 |
|
(new RandomIntsSpliterator |
612 |
|
(this, 0L, streamSize, Integer.MAX_VALUE, 0), |
615 |
|
|
616 |
|
/** |
617 |
|
* Returns an effectively unlimited stream of pseudorandom {@code int} |
618 |
< |
* values. |
618 |
> |
* values from this generator and/or one split from it. |
619 |
|
* |
620 |
|
* @implNote This method is implemented to be equivalent to {@code |
621 |
|
* ints(Long.MAX_VALUE)}. |
630 |
|
} |
631 |
|
|
632 |
|
/** |
633 |
< |
* Returns a stream producing the given {@code streamSize} number of |
634 |
< |
* pseudorandom {@code int} values, each conforming to the given |
635 |
< |
* origin and bound. |
633 |
> |
* Returns a stream producing the given {@code streamSize} number |
634 |
> |
* of pseudorandom {@code int} values from this generator and/or one split |
635 |
> |
* from it; each value conforms to the given origin (inclusive) and bound |
636 |
> |
* (exclusive). |
637 |
|
* |
638 |
|
* @param streamSize the number of values to generate |
639 |
< |
* @param randomNumberOrigin the origin of each random value |
640 |
< |
* @param randomNumberBound the bound of each random value |
639 |
> |
* @param randomNumberOrigin the origin (inclusive) of each random value |
640 |
> |
* @param randomNumberBound the bound (exclusive) of each random value |
641 |
|
* @return a stream of pseudorandom {@code int} values, |
642 |
< |
* each with the given origin and bound |
642 |
> |
* each with the given origin (inclusive) and bound (exclusive) |
643 |
|
* @throws IllegalArgumentException if {@code streamSize} is |
644 |
|
* less than zero, or {@code randomNumberOrigin} |
645 |
|
* is greater than or equal to {@code randomNumberBound} |
647 |
|
public IntStream ints(long streamSize, int randomNumberOrigin, |
648 |
|
int randomNumberBound) { |
649 |
|
if (streamSize < 0L) |
650 |
< |
throw new IllegalArgumentException("negative Stream size"); |
650 |
> |
throw new IllegalArgumentException(BadSize); |
651 |
|
if (randomNumberOrigin >= randomNumberBound) |
652 |
< |
throw new IllegalArgumentException("bound must be greater than origin"); |
652 |
> |
throw new IllegalArgumentException(BadRange); |
653 |
|
return StreamSupport.intStream |
654 |
|
(new RandomIntsSpliterator |
655 |
|
(this, 0L, streamSize, randomNumberOrigin, randomNumberBound), |
658 |
|
|
659 |
|
/** |
660 |
|
* Returns an effectively unlimited stream of pseudorandom {@code |
661 |
< |
* int} values, each conforming to the given origin and bound. |
661 |
> |
* int} values from this generator and/or one split from it; each value |
662 |
> |
* conforms to the given origin (inclusive) and bound (exclusive). |
663 |
|
* |
664 |
|
* @implNote This method is implemented to be equivalent to {@code |
665 |
|
* ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. |
666 |
|
* |
667 |
< |
* @param randomNumberOrigin the origin of each random value |
668 |
< |
* @param randomNumberBound the bound of each random value |
667 |
> |
* @param randomNumberOrigin the origin (inclusive) of each random value |
668 |
> |
* @param randomNumberBound the bound (exclusive) of each random value |
669 |
|
* @return a stream of pseudorandom {@code int} values, |
670 |
< |
* each with the given origin and bound |
670 |
> |
* each with the given origin (inclusive) and bound (exclusive) |
671 |
|
* @throws IllegalArgumentException if {@code randomNumberOrigin} |
672 |
|
* is greater than or equal to {@code randomNumberBound} |
673 |
|
*/ |
674 |
|
public IntStream ints(int randomNumberOrigin, int randomNumberBound) { |
675 |
|
if (randomNumberOrigin >= randomNumberBound) |
676 |
< |
throw new IllegalArgumentException("bound must be greater than origin"); |
676 |
> |
throw new IllegalArgumentException(BadRange); |
677 |
|
return StreamSupport.intStream |
678 |
|
(new RandomIntsSpliterator |
679 |
|
(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), |
681 |
|
} |
682 |
|
|
683 |
|
/** |
684 |
< |
* Returns a stream producing the given {@code streamSize} number of |
685 |
< |
* pseudorandom {@code long} values. |
684 |
> |
* Returns a stream producing the given {@code streamSize} number |
685 |
> |
* of pseudorandom {@code long} values from this generator and/or |
686 |
> |
* one split from it. |
687 |
|
* |
688 |
|
* @param streamSize the number of values to generate |
689 |
|
* @return a stream of pseudorandom {@code long} values |
692 |
|
*/ |
693 |
|
public LongStream longs(long streamSize) { |
694 |
|
if (streamSize < 0L) |
695 |
< |
throw new IllegalArgumentException("negative Stream size"); |
695 |
> |
throw new IllegalArgumentException(BadSize); |
696 |
|
return StreamSupport.longStream |
697 |
|
(new RandomLongsSpliterator |
698 |
|
(this, 0L, streamSize, Long.MAX_VALUE, 0L), |
700 |
|
} |
701 |
|
|
702 |
|
/** |
703 |
< |
* Returns an effectively unlimited stream of pseudorandom {@code long} |
704 |
< |
* values. |
703 |
> |
* Returns an effectively unlimited stream of pseudorandom {@code |
704 |
> |
* long} values from this generator and/or one split from it. |
705 |
|
* |
706 |
|
* @implNote This method is implemented to be equivalent to {@code |
707 |
|
* longs(Long.MAX_VALUE)}. |
717 |
|
|
718 |
|
/** |
719 |
|
* Returns a stream producing the given {@code streamSize} number of |
720 |
< |
* pseudorandom {@code long} values, each conforming to the |
721 |
< |
* given origin and bound. |
720 |
> |
* pseudorandom {@code long} values from this generator and/or one split |
721 |
> |
* from it; each value conforms to the given origin (inclusive) and bound |
722 |
> |
* (exclusive). |
723 |
|
* |
724 |
|
* @param streamSize the number of values to generate |
725 |
< |
* @param randomNumberOrigin the origin of each random value |
726 |
< |
* @param randomNumberBound the bound of each random value |
725 |
> |
* @param randomNumberOrigin the origin (inclusive) of each random value |
726 |
> |
* @param randomNumberBound the bound (exclusive) of each random value |
727 |
|
* @return a stream of pseudorandom {@code long} values, |
728 |
< |
* each with the given origin and bound |
728 |
> |
* each with the given origin (inclusive) and bound (exclusive) |
729 |
|
* @throws IllegalArgumentException if {@code streamSize} is |
730 |
|
* less than zero, or {@code randomNumberOrigin} |
731 |
|
* is greater than or equal to {@code randomNumberBound} |
733 |
|
public LongStream longs(long streamSize, long randomNumberOrigin, |
734 |
|
long randomNumberBound) { |
735 |
|
if (streamSize < 0L) |
736 |
< |
throw new IllegalArgumentException("negative Stream size"); |
736 |
> |
throw new IllegalArgumentException(BadSize); |
737 |
|
if (randomNumberOrigin >= randomNumberBound) |
738 |
< |
throw new IllegalArgumentException("bound must be greater than origin"); |
738 |
> |
throw new IllegalArgumentException(BadRange); |
739 |
|
return StreamSupport.longStream |
740 |
|
(new RandomLongsSpliterator |
741 |
|
(this, 0L, streamSize, randomNumberOrigin, randomNumberBound), |
744 |
|
|
745 |
|
/** |
746 |
|
* Returns an effectively unlimited stream of pseudorandom {@code |
747 |
< |
* long} values, each conforming to the given origin and bound. |
747 |
> |
* long} values from this generator and/or one split from it; each value |
748 |
> |
* conforms to the given origin (inclusive) and bound (exclusive). |
749 |
|
* |
750 |
|
* @implNote This method is implemented to be equivalent to {@code |
751 |
|
* longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. |
752 |
|
* |
753 |
< |
* @param randomNumberOrigin the origin of each random value |
754 |
< |
* @param randomNumberBound the bound of each random value |
753 |
> |
* @param randomNumberOrigin the origin (inclusive) of each random value |
754 |
> |
* @param randomNumberBound the bound (exclusive) of each random value |
755 |
|
* @return a stream of pseudorandom {@code long} values, |
756 |
< |
* each with the given origin and bound |
756 |
> |
* each with the given origin (inclusive) and bound (exclusive) |
757 |
|
* @throws IllegalArgumentException if {@code randomNumberOrigin} |
758 |
|
* is greater than or equal to {@code randomNumberBound} |
759 |
|
*/ |
760 |
|
public LongStream longs(long randomNumberOrigin, long randomNumberBound) { |
761 |
|
if (randomNumberOrigin >= randomNumberBound) |
762 |
< |
throw new IllegalArgumentException("bound must be greater than origin"); |
762 |
> |
throw new IllegalArgumentException(BadRange); |
763 |
|
return StreamSupport.longStream |
764 |
|
(new RandomLongsSpliterator |
765 |
|
(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), |
768 |
|
|
769 |
|
/** |
770 |
|
* Returns a stream producing the given {@code streamSize} number of |
771 |
< |
* pseudorandom {@code double} values, each between zero |
772 |
< |
* (inclusive) and one (exclusive). |
771 |
> |
* pseudorandom {@code double} values from this generator and/or one split |
772 |
> |
* from it; each value is between zero (inclusive) and one (exclusive). |
773 |
|
* |
774 |
|
* @param streamSize the number of values to generate |
775 |
|
* @return a stream of {@code double} values |
778 |
|
*/ |
779 |
|
public DoubleStream doubles(long streamSize) { |
780 |
|
if (streamSize < 0L) |
781 |
< |
throw new IllegalArgumentException("negative Stream size"); |
781 |
> |
throw new IllegalArgumentException(BadSize); |
782 |
|
return StreamSupport.doubleStream |
783 |
|
(new RandomDoublesSpliterator |
784 |
|
(this, 0L, streamSize, Double.MAX_VALUE, 0.0), |
787 |
|
|
788 |
|
/** |
789 |
|
* Returns an effectively unlimited stream of pseudorandom {@code |
790 |
< |
* double} values, each between zero (inclusive) and one |
791 |
< |
* (exclusive). |
790 |
> |
* double} values from this generator and/or one split from it; each value |
791 |
> |
* is between zero (inclusive) and one (exclusive). |
792 |
|
* |
793 |
|
* @implNote This method is implemented to be equivalent to {@code |
794 |
|
* doubles(Long.MAX_VALUE)}. |
804 |
|
|
805 |
|
/** |
806 |
|
* Returns a stream producing the given {@code streamSize} number of |
807 |
< |
* pseudorandom {@code double} values, each conforming to the |
808 |
< |
* given origin and bound. |
807 |
> |
* pseudorandom {@code double} values from this generator and/or one split |
808 |
> |
* from it; each value conforms to the given origin (inclusive) and bound |
809 |
> |
* (exclusive). |
810 |
|
* |
811 |
|
* @param streamSize the number of values to generate |
812 |
< |
* @param randomNumberOrigin the origin of each random value |
813 |
< |
* @param randomNumberBound the bound of each random value |
812 |
> |
* @param randomNumberOrigin the origin (inclusive) of each random value |
813 |
> |
* @param randomNumberBound the bound (exclusive) of each random value |
814 |
|
* @return a stream of pseudorandom {@code double} values, |
815 |
< |
* each with the given origin and bound |
815 |
> |
* each with the given origin (inclusive) and bound (exclusive) |
816 |
|
* @throws IllegalArgumentException if {@code streamSize} is |
817 |
< |
* less than zero |
817 |
> |
* less than zero |
818 |
|
* @throws IllegalArgumentException if {@code randomNumberOrigin} |
819 |
|
* is greater than or equal to {@code randomNumberBound} |
820 |
|
*/ |
821 |
|
public DoubleStream doubles(long streamSize, double randomNumberOrigin, |
822 |
|
double randomNumberBound) { |
823 |
|
if (streamSize < 0L) |
824 |
< |
throw new IllegalArgumentException("negative Stream size"); |
824 |
> |
throw new IllegalArgumentException(BadSize); |
825 |
|
if (!(randomNumberOrigin < randomNumberBound)) |
826 |
< |
throw new IllegalArgumentException("bound must be greater than origin"); |
826 |
> |
throw new IllegalArgumentException(BadRange); |
827 |
|
return StreamSupport.doubleStream |
828 |
|
(new RandomDoublesSpliterator |
829 |
|
(this, 0L, streamSize, randomNumberOrigin, randomNumberBound), |
832 |
|
|
833 |
|
/** |
834 |
|
* Returns an effectively unlimited stream of pseudorandom {@code |
835 |
< |
* double} values, each conforming to the given origin and bound. |
835 |
> |
* double} values from this generator and/or one split from it; each value |
836 |
> |
* conforms to the given origin (inclusive) and bound (exclusive). |
837 |
|
* |
838 |
|
* @implNote This method is implemented to be equivalent to {@code |
839 |
|
* doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. |
840 |
|
* |
841 |
< |
* @param randomNumberOrigin the origin of each random value |
842 |
< |
* @param randomNumberBound the bound of each random value |
841 |
> |
* @param randomNumberOrigin the origin (inclusive) of each random value |
842 |
> |
* @param randomNumberBound the bound (exclusive) of each random value |
843 |
|
* @return a stream of pseudorandom {@code double} values, |
844 |
< |
* each with the given origin and bound |
844 |
> |
* each with the given origin (inclusive) and bound (exclusive) |
845 |
|
* @throws IllegalArgumentException if {@code randomNumberOrigin} |
846 |
|
* is greater than or equal to {@code randomNumberBound} |
847 |
|
*/ |
848 |
|
public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) { |
849 |
|
if (!(randomNumberOrigin < randomNumberBound)) |
850 |
< |
throw new IllegalArgumentException("bound must be greater than origin"); |
850 |
> |
throw new IllegalArgumentException(BadRange); |
851 |
|
return StreamSupport.doubleStream |
852 |
|
(new RandomDoublesSpliterator |
853 |
|
(this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), |
862 |
|
* approach. The long and double versions of this class are |
863 |
|
* identical except for types. |
864 |
|
*/ |
865 |
< |
static class RandomIntsSpliterator implements Spliterator.OfInt { |
865 |
> |
static final class RandomIntsSpliterator implements Spliterator.OfInt { |
866 |
|
final SplittableRandom rng; |
867 |
|
long index; |
868 |
|
final long fence; |
905 |
|
long i = index, f = fence; |
906 |
|
if (i < f) { |
907 |
|
index = f; |
908 |
+ |
SplittableRandom r = rng; |
909 |
|
int o = origin, b = bound; |
910 |
|
do { |
911 |
< |
consumer.accept(rng.internalNextInt(o, b)); |
911 |
> |
consumer.accept(r.internalNextInt(o, b)); |
912 |
|
} while (++i < f); |
913 |
|
} |
914 |
|
} |
917 |
|
/** |
918 |
|
* Spliterator for long streams. |
919 |
|
*/ |
920 |
< |
static class RandomLongsSpliterator implements Spliterator.OfLong { |
920 |
> |
static final class RandomLongsSpliterator implements Spliterator.OfLong { |
921 |
|
final SplittableRandom rng; |
922 |
|
long index; |
923 |
|
final long fence; |
960 |
|
long i = index, f = fence; |
961 |
|
if (i < f) { |
962 |
|
index = f; |
963 |
+ |
SplittableRandom r = rng; |
964 |
|
long o = origin, b = bound; |
965 |
|
do { |
966 |
< |
consumer.accept(rng.internalNextLong(o, b)); |
966 |
> |
consumer.accept(r.internalNextLong(o, b)); |
967 |
|
} while (++i < f); |
968 |
|
} |
969 |
|
} |
973 |
|
/** |
974 |
|
* Spliterator for double streams. |
975 |
|
*/ |
976 |
< |
static class RandomDoublesSpliterator implements Spliterator.OfDouble { |
976 |
> |
static final class RandomDoublesSpliterator implements Spliterator.OfDouble { |
977 |
|
final SplittableRandom rng; |
978 |
|
long index; |
979 |
|
final long fence; |
1016 |
|
long i = index, f = fence; |
1017 |
|
if (i < f) { |
1018 |
|
index = f; |
1019 |
+ |
SplittableRandom r = rng; |
1020 |
|
double o = origin, b = bound; |
1021 |
|
do { |
1022 |
< |
consumer.accept(rng.internalNextDouble(o, b)); |
1022 |
> |
consumer.accept(r.internalNextDouble(o, b)); |
1023 |
|
} while (++i < f); |
1024 |
|
} |
1025 |
|
} |