jdk-sandbox: comparison src/java.base/share/classes/java/util/random/L64X128MixRandom.java

equal deleted inserted replaced

-:b0c958c0e6c6
+:f02ffcb61dce
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
-package java.util;
+package java.util.random;
 import java.math.BigInteger;
 import java.util.concurrent.atomic.AtomicLong;
 /**
 * A generator of uniform pseudorandom values applicable for use in
 * (among other contexts) isolated parallel computations that may
-* generate subtasks.  Class {@code L64X128MixRandom} implements
+* generate subtasks.  Class {@link L64X128MixRandom} implements
-* interfaces {@link java.util.Rng} and {@link java.util.SplittableRng},
+* interfaces {@link RandomNumberGenerator} and {@link SplittableRNG},
 * and therefore supports methods for producing pseudorandomly chosen
 * numbers of type {@code int}, {@code long}, {@code float}, and {@code double}
-* as well as creating new split-off {@code L64X128MixRandom} objects,
+* as well as creating new split-off {@link L64X128MixRandom} objects,
 * with similar usages as for class {@link java.util.SplittableRandom}.
-*
+* <p>
-* <p>Series of generated values pass the TestU01 BigCrush and PractRand test suites
+* Series of generated values pass the TestU01 BigCrush and PractRand test suites
 * that measure independence and uniformity properties of random number generators.
 * (Most recently validated with
 * <a href="http://simul.iro.umontreal.ca/testu01/tu01.html">version 1.2.3 of TestU01</a>
 * and <a href="http://pracrand.sourceforge.net">version 0.90 of PractRand</a>.
 * Note that TestU01 BigCrush was used to test not only values produced by the {@code nextLong()}
 * method but also the result of bit-reversing each value produced by {@code nextLong()}.)
 * These tests validate only the methods for certain
 * types and ranges, but similar properties are expected to hold, at
 * least approximately, for others as well.
-*
+* <p>
-* <p>{@code L64X128MixRandom} is a specific member of the LXM family of algorithms
+* {@link L64X128MixRandom} is a specific member of the LXM family of algorithms
 * for pseudorandom number generators.  Every LXM generator consists of two
 * subgenerators; one is an LCG (Linear Congruential Generator) and the other is
 * an Xorshift generator.  Each output of an LXM generator is the sum of one
 * output from each subgenerator, possibly processed by a final mixing function
-* (and {@code L64X128MixRandom} does use a mixing function).
+* (and {@link L64X128MixRandom} does use a mixing function).
-*
+* <p>
-* <p>The LCG subgenerator for {@code L64X128MixRandom} has an update step of the
+* The LCG subgenerator for {@link L64X128MixRandom} has an update step of the
 * form {@code s = m * s + a}, where {@code s}, {@code m}, and {@code a} are all
 * of type {@code long}; {@code s} is the mutable state, the multiplier {@code m}
-* is fixed (the same for all instances of {@code L64X128MixRandom}}) and the addend
+* is fixed (the same for all instances of {@link L64X128MixRandom}}) and the addend
 * {@code a} is a parameter (a final field of the instance).  The parameter
 * {@code a} is required to be odd (this allows the LCG to have the maximal
 * period, namely 2<sup>64</sup>); therefore there are 2<sup>63</sup> distinct choices
 * of parameter.
-*
+* <p>
-* <p>The Xorshift subgenerator for {@code L64X128MixRandom} is the {@code xoroshiro128} algorithm,
+* The Xorshift subgenerator for {@link L64X128MixRandom} is the {@code xoroshiro128} algorithm,
 * version 1.0 (parameters 24, 16, 37), without any final scrambler such as "+" or "**".
 * Its state consists of two {@code long} fields {@code x0} and {@code x1},
 * which can take on any values provided that they are not both zero.
 * The period of this subgenerator is 2<sup>128</sup>-1.
-*
+* <p>
-* <p> The mixing function for {@code L64X128MixRandom} is the 64-bit "starstar(5,7,9)" function.
+* The mixing function for {@link L64X128MixRandom} is the 64-bit "starstar(5,7,9)" function.
-*
+* <p>
-* <p> Because the periods 2<sup>64</sup> and 2<sup>128</sup>-1 of the two subgenerators
+* Because the periods 2<sup>64</sup> and 2<sup>128</sup>-1 of the two subgenerators
-* are relatively prime, the <em>period</em> of any single {@code L64X128MixRandom} object
+* are relatively prime, the <em>period</em> of any single {@link L64X128MixRandom} object
 * (the length of the series of generated 64-bit values before it repeats) is the product
 * of the periods of the subgenerators, that is, 2<sup>64</sup>(2<sup>128</sup>-1),
 * which is just slightly smaller than 2<sup>192</sup>.  Moreover, if two distinct
-* {@code L64X128MixRandom} objects have different {@code a} parameters, then their
+* {@link L64X128MixRandom} objects have different {@code a} parameters, then their
 * cycles of produced values will be different.
-*
+* <p>
-* <p>The 64-bit values produced by the {@code nextLong()} method are exactly equidistributed.
+* The 64-bit values produced by the {@code nextLong()} method are exactly equidistributed.
-* For any specific instance of {@code L64X128MixRandom}, over the course of its cycle each
+* For any specific instance of {@link L64X128MixRandom}, over the course of its cycle each
 * of the 2<sup>64</sup> possible {@code long} values will be produced 2<sup>128</sup>-1 times.
 * The values produced by the {@code nextInt()}, {@code nextFloat()}, and {@code nextDouble()}
 * methods are likewise exactly equidistributed.
-*
+* <p>
-* <p>In fact, the 64-bit values produced by the {@code nextLong()} method are 2-equidistributed.
+* In fact, the 64-bit values produced by the {@code nextLong()} method are 2-equidistributed.
-* To be precise: for any specific instance of {@code L64X128MixRandom}, consider
+* To be precise: for any specific instance of {@link L64X128MixRandom}, consider
 * the (overlapping) length-2 subsequences of the cycle of 64-bit values produced by
 * {@code nextLong()} (assuming no other methods are called that would affect the state).
 * There are 2<sup>64</sup>(2<sup>128</sup>-1) such subsequences, and each subsequence,
 * which consists of 2 64-bit values, can have one of 2<sup>128</sup> values. Of those
 * 2<sup>128</sup> subsequence values, nearly all of them (2<sup>128</sup>-2<sup>64</sup>)
 * occur 2<sup>64</sup> times over the course of the entire cycle, and the other
 * 2<sup>64</sup> subsequence values occur only 2<sup>64</sup>-1 times.  So the ratio
 * of the probability of getting one of the less common subsequence values and the
 * probability of getting one of the more common subsequence values is 1-2<sup>-64</sup>.
 * (Note that the set of 2<sup>64</sup> less-common subsequence values will differ from
-* one instance of {@code L64X128MixRandom} to another, as a function of the additive
+* one instance of {@link L64X128MixRandom} to another, as a function of the additive
 * parameter of the LCG.)  The values produced by the {@code nextInt()}, {@code nextFloat()},
 * and {@code nextDouble()} methods are likewise 2-equidistributed.
-*
+* <p>
-* <p>Method {@link #split} constructs and returns a new {@code L64X128MixRandom}
+* Method {@link #split} constructs and returns a new {@link L64X128MixRandom}
 * 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 L64X128MixRandom} object.
+* generated by a single thread using a single {@link L64X128MixRandom} object.
-* This is because, with high probability, distinct {@code L64X128MixRandom} objects
+* This is because, with high probability, distinct {@link L64X128MixRandom} objects
 * have distinct {@code a} parameters and therefore use distinct members of the
 * algorithmic family; and even if their {@code a} parameters are the same, with
 * very high probability they will traverse different parts of their common state
 * cycle.
-*
+* <p>
-* <p>As with {@link java.util.SplittableRandom}, instances of
+* As with {@link java.util.SplittableRandom}, instances of
-* {@code L64X128MixRandom} are <em>not</em> thread-safe.
+* {@link L64X128MixRandom} are <em>not</em> thread-safe.
 * They are designed to be split, not shared, across threads. For
 * example, a {@link java.util.concurrent.ForkJoinTask} fork/join-style
 * computation using random numbers might include a construction
 * of the form {@code new Subtask(someL64X128MixRandom.split()).fork()}.
-*
+* <p>
-* <p>This class provides additional methods for generating random
+* This class provides additional methods for generating random
 * streams, that employ the above techniques when used in
 * {@code stream.parallel()} mode.
-*
+* <p>
-* <p>Instances of {@code L64X128MixRandom} are not cryptographically
+* Instances of {@link L64X128MixRandom} are not cryptographically
 * secure.  Consider instead using {@link java.security.SecureRandom}
 * in security-sensitive applications. Additionally,
 * default-constructed instances do not use a cryptographically random
 * seed unless the {@linkplain System#getProperty system property}
 * {@code java.util.secureRandomSeed} is set to {@code true}.
 *
-* @author  Guy Steele
+* @since 14
-* @since   1.9
 */
-public final class L64X128MixRandom extends AbstractSplittableRng {
+public final class L64X128MixRandom extends AbstractSplittableRNG {
 /*
 * Implementation Overview.
 *
 * The split operation uses the current generator to choose four new 64-bit
 * long values that are then used to initialize the parameter `a` and the
 * state variables `s`, `x0`, and `x1` for a newly constructed generator.
 *
 * With extremely high probability, no two generators so chosen
 * will have the same `a` parameter, and testing has indicated
-* that the values generated by two instances of {@code L64X128MixRandom}
+* that the values generated by two instances of {@link L64X128MixRandom}
 * will be (approximately) independent if have different values for `a`.
 *
 * The default (no-argument) constructor, in essence, uses
 * "defaultGen" to generate four new 64-bit values for the same
 * purpose.  Multiple generators created in this way will certainly
 * avoids stalls that may occur when using /dev/random.
 *
 * File organization: First static fields, then instance
 * fields, then constructors, then instance methods.
 */
 /* ---------------- static fields ---------------- */
 /**
 * The seed generator for default constructors.
 */
-private static final AtomicLong defaultGen = new AtomicLong(RngSupport.initialSeed());
+private static final AtomicLong defaultGen = new AtomicLong(RNGSupport.initialSeed());
 /*
 * The period of this generator, which is (2**128 - 1) * 2**64.
 */
-private static final BigInteger thePeriod =
+private static final BigInteger PERIOD =
-	BigInteger.ONE.shiftLeft(128).subtract(BigInteger.ONE).shiftLeft(64);
+BigInteger.ONE.shiftLeft(128).subtract(BigInteger.ONE).shiftLeft(64);
 /*
 * Multiplier used in the LCG portion of the algorithm, taken from
 * Pierre L'Ecuyer, Tables of linear congruential generators of
 * different sizes and good lattice structure, <em>Mathematics of
 * Computation</em> 68, 225 (January 1999), pages 249-260,
 * Table 4 (first multiplier for size 2<sup>64</sup>).
 */
-private static final long m = 2862933555777941757L;
+private static final long M = 2862933555777941757L;
 /* ---------------- instance fields ---------------- */
 /**
 * The parameter that is used as an additive constant for the LCG.
 * @param s initial state for the LCG
 * @param x0 first word of the initial state for the xorshift generator
 * @param x1 second word of the initial state for the xorshift generator
 */
 public L64X128MixRandom(long a, long s, long x0, long x1) {
-	// Force a to be odd.
+// Force a to be odd.
-this.a = a | 1;
-this.s = s;
-	this.x0 = x0;
-this.x1 = x1;
-	// If x0 and x1 are both zero, we must choose nonzero values.
-if ((x0 | x1) == 0) {
-	    // At least one of the two values generated here will be nonzero.
-	    this.x0 = RngSupport.mixStafford13(s += RngSupport.GOLDEN_RATIO_64);
-	    this.x1 = RngSupport.mixStafford13(s + RngSupport.GOLDEN_RATIO_64);
-	}
-}
-/**
-* Creates a new instance of {@code L64X128MixRandom} using the
-* specified {@code long} value as the initial seed. Instances of
-* {@code L64X128MixRandom} created with the same seed in the same
-* program generate identical sequences of values.
-*
-* @param seed the initial seed
-*/
-public L64X128MixRandom(long seed) {
-	// Using a value with irregularly spaced 1-bits to xor the seed
-	// argument tends to improve "pedestrian" seeds such as 0 or
-	// other small integers.  We may as well use SILVER_RATIO_64.
-	//
-	// The seed is hashed by mixMurmur64 to produce the `a` parameter.
-	// The seed is hashed by mixStafford13 to produce the initial `x0`,
-	// which will then be used to produce the first generated value.
-	// Then x1 is filled in as if by a SplitMix PRNG with
-	// GOLDEN_RATIO_64 as the gamma value and Stafford13 as the mixer.
-this(RngSupport.mixMurmur64(seed ^= RngSupport.SILVER_RATIO_64),
-	     1,
-	     RngSupport.mixStafford13(seed),
-	     RngSupport.mixStafford13(seed + RngSupport.GOLDEN_RATIO_64));
-}
-/**
-* Creates a new instance of {@code L64X128MixRandom} that is likely to
-* generate sequences of values that are statistically independent
-* of those of any other instances in the current program execution,
-* but may, and typically does, vary across program invocations.
-*/
-public L64X128MixRandom() {
-	// Using GOLDEN_RATIO_64 here gives us a good Weyl sequence of values.
-	this(defaultGen.getAndAdd(RngSupport.GOLDEN_RATIO_64));
-}
-/**
-* Creates a new instance of {@code L64X128MixRandom} using the specified array of
-* initial seed bytes. Instances of {@code L64X128MixRandom} created with the same
-* seed array in the same program execution generate identical sequences of values.
-*
-* @param seed the initial seed
-*/
-public L64X128MixRandom(byte[] seed) {
-	// Convert the seed to 4 long values, of which the last 2 are not all zero.
-	long[] data = RngSupport.convertSeedBytesToLongs(seed, 4, 2);
-	long a = data[0], s = data[1], x0 = data[2], x1 = data[3];
-	// Force a to be odd.
 this.a = a | 1;
 this.s = s;
 this.x0 = x0;
 this.x1 = x1;
+// If x0 and x1 are both zero, we must choose nonzero values.
+if ((x0 | x1) == 0) {
+// At least one of the two values generated here will be nonzero.
+this.x0 = RNGSupport.mixStafford13(s += RNGSupport.GOLDEN_RATIO_64);
+this.x1 = RNGSupport.mixStafford13(s + RNGSupport.GOLDEN_RATIO_64);
+}
+}
+/**
+* Creates a new instance of {@link L64X128MixRandom} using the
+* specified {@code long} value as the initial seed. Instances of
+* {@link L64X128MixRandom} created with the same seed in the same
+* program generate identical sequences of values.
+*
+* @param seed the initial seed
+*/
+public L64X128MixRandom(long seed) {
+// Using a value with irregularly spaced 1-bits to xor the seed
+// argument tends to improve "pedestrian" seeds such as 0 or
+// other small integers.  We may as well use SILVER_RATIO_64.
+//
+// The seed is hashed by mixMurmur64 to produce the `a` parameter.
+// The seed is hashed by mixStafford13 to produce the initial `x0`,
+// which will then be used to produce the first generated value.
+// Then x1 is filled in as if by a SplitMix PRNG with
+// GOLDEN_RATIO_64 as the gamma value and Stafford13 as the mixer.
+this(RNGSupport.mixMurmur64(seed ^= RNGSupport.SILVER_RATIO_64),
+1,
+RNGSupport.mixStafford13(seed),
+RNGSupport.mixStafford13(seed + RNGSupport.GOLDEN_RATIO_64));
+}
+/**
+* Creates a new instance of {@link L64X128MixRandom} that is likely to
+* generate sequences of values that are statistically independent
+* of those of any other instances in the current program execution,
+* but may, and typically does, vary across program invocations.
+*/
+public L64X128MixRandom() {
+// Using GOLDEN_RATIO_64 here gives us a good Weyl sequence of values.
+this(defaultGen.getAndAdd(RNGSupport.GOLDEN_RATIO_64));
+}
+/**
+* Creates a new instance of {@link L64X128MixRandom} using the specified array of
+* initial seed bytes. Instances of {@link L64X128MixRandom} created with the same
+* seed array in the same program execution generate identical sequences of values.
+*
+* @param seed the initial seed
+*/
+public L64X128MixRandom(byte[] seed) {
+// Convert the seed to 4 long values, of which the last 2 are not all zero.
+long[] data = RNGSupport.convertSeedBytesToLongs(seed, 4, 2);
+long a = data[0], s = data[1], x0 = data[2], x1 = data[3];
+// Force a to be odd.
+this.a = a | 1;
+this.s = s;
+this.x0 = x0;
+this.x1 = x1;
 }
 /* ---------------- public methods ---------------- */
 /**
-* Constructs and returns a new instance of {@code L64X128MixRandom}
+* Constructs and returns a new instance of {@link L64X128MixRandom}
 * that shares no mutable state with this instance.
 * However, with very high probability, the set of values collectively
 * generated by the two objects has the same statistical properties as if
 * same the quantity of values were generated by a single thread using
-* a single {@code L64X128MixRandom} object.  Either or both of the two
+* a single {@link L64X128MixRandom} object.  Either or both of the two
 * objects may be further split using the {@code split} method,
 * and the same expected statistical properties apply to the
 * entire set of generators constructed by such recursive splitting.
 *
-* @param source a {@code SplittableRng} instance to be used instead
+* @param source a {@link SplittableRNG} instance to be used instead
 *               of this one as a source of pseudorandom bits used to
 *               initialize the state of the new ones.
-* @return a new instance of {@code L64X128MixRandom}
+*
-*/
+* @return a new instance of {@link L64X128MixRandom}
-public L64X128MixRandom split(SplittableRng source) {
+*/
-	// Literally pick a new instance "at random".
+public L64X128MixRandom split(SplittableRNG source) {
+// Literally pick a new instance "at random".
 return new L64X128MixRandom(source.nextLong(), source.nextLong(),
-				    source.nextLong(), source.nextLong());
+source.nextLong(), source.nextLong());
 }
 /**
 * Returns a pseudorandom {@code long} value.
 *
 * @return a pseudorandom {@code long} value
 */
 public long nextLong() {
-	final long z = s + x0;
+final long z = s + x0;
-	s = m * s + a;  // LCG
+s = M * s + a;  // LCG
-	long q0 = x0, q1 = x1;
+long q0 = x0, q1 = x1;
-	{ q1 ^= q0; q0 = Long.rotateLeft(q0, 24); q0 = q0 ^ q1 ^ (q1 << 16); q1 = Long.rotateLeft(q1, 37); }  // xoroshiro128v1_0
+{ q1 ^= q0; q0 = Long.rotateLeft(q0, 24); q0 = q0 ^ q1 ^ (q1 << 16); q1 = Long.rotateLeft(q1, 37); }  // xoroshiro128v1_0
-	x0 = q0; x1 = q1;
+x0 = q0; x1 = q1;
-	return Long.rotateLeft(z * 5, 7) * 9;  // "starstar" mixing function
+return Long.rotateLeft(z * 5, 7) * 9;  // "starstar" mixing function
 }
-public BigInteger period() { return thePeriod; }
+public BigInteger period() {
+return PERIOD;
+}
 }

branch	JDK-8193209-branch
changeset 57437	f02ffcb61dce
parent 57436	b0c958c0e6c6
child 57547	56cbdc3ea079