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* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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// package java.util;
import java.util.Spliterator;
import java.util.function.Consumer;
import java.util.function.IntConsumer;
import java.util.function.LongConsumer;
import java.util.function.DoubleConsumer;
import java.util.stream.StreamSupport;
import java.util.stream.Stream;
/**
* This class provides much of the implementation of the
* {@code ArbitrarilyJumpableRng} interface, to minimize the effort
* required to implement that interface.
*
* To implement a pseudorandom number generator, the programmer needs
* only to extend this class and provide implementations for the
* methods {@code nextInt()}, {@code nextLong()}, {@code copy()},
* {@code jump(distance)}, {@code jumpPowerOfTwo(distance)},
* {@code defaultJumpDistance()}, and {@code defaultLeapDistance()}.
*
* (If the pseudorandom number generator also has the ability to split,
* then the programmer may wish to consider instead extending
* {@code AbstractSplittableArbitrarilyJumpableRng}.)
*
* The programmer should generally provide at least three constructors:
* one that takes no arguments, one that accepts a {@code long}
* seed value, and one that accepts an array of seed {@code byte} values.
* This class provides a public {@code initialSeed()} method that may
* be useful in initializing some static state from which to derive
* defaults seeds for use by the no-argument constructor.
*
* For the stream methods (such as {@code ints()} and {@code splits()}),
* this class provides {@code Spliterator}-based implementations that
* allow parallel execution when appropriate. In this respect
* {@code ArbitrarilyJumpableRng} differs from {@code JumpableRng},
* which provides very simple implementations that produce
* sequential streams only.
*
* <p>An implementation of the {@code AbstractArbitrarilyJumpableRng} class
* must provide concrete definitions for the methods {@code nextInt()},
* {@code nextLong}, {@code period()}, {@code copy()}, {@code jump(double)},
* {@code defaultJumpDistance()}, and {@code defaultLeapDistance()}.
* Default implementations are provided for all other methods.
*
* The documentation for each non-abstract method in this class
* describes its implementation in detail. Each of these methods may
* be overridden if the pseudorandom number generator being
* implemented admits a more efficient implementation.
*
* @author Guy Steele
* @since 1.9
*/
public abstract class AbstractArbitrarilyJumpableRng
extends AbstractSpliteratorRng implements ArbitrarilyJumpableRng {
/*
* Implementation Overview.
*
* This class provides most of the "user API" methods needed to satisfy
* the interface java.util.ArbitrarilyJumpableRng. Most of these methods
* are in turn inherited from AbstractRng and the non-public class
* AbstractSpliteratorRng; this file implements four versions of the
* jumps method and defines the spliterators necessary to support them.
*
* File organization: First the non-public methods needed by the class
* AbstractSpliteratorRng, then the main public methods, followed by some
* custom spliterator classes needed for stream methods.
*/
// IllegalArgumentException messages
static final String BadLogDistance = "logDistance must be non-negative";
// Methods required by class AbstractSpliteratorRng
Spliterator.OfInt makeIntsSpliterator(long index, long fence, int origin, int bound) {
return new RandomIntsSpliterator(this, index, fence, origin, bound);
}
Spliterator.OfLong makeLongsSpliterator(long index, long fence, long origin, long bound) {
return new RandomLongsSpliterator(this, index, fence, origin, bound);
}
Spliterator.OfDouble makeDoublesSpliterator(long index, long fence, double origin, double bound) {
return new RandomDoublesSpliterator(this, index, fence, origin, bound);
}
// Similar methods used by this class
Spliterator<Rng> makeJumpsSpliterator(long index, long fence, double distance) {
return new RandomJumpsSpliterator(this, index, fence, distance);
}
Spliterator<JumpableRng> makeLeapsSpliterator(long index, long fence, double distance) {
return new RandomLeapsSpliterator(this, index, fence, distance);
}
Spliterator<ArbitrarilyJumpableRng> makeArbitraryJumpsSpliterator(long index, long fence, double distance) {
return new RandomArbitraryJumpsSpliterator(this, index, fence, distance);
}
/* ---------------- public methods ---------------- */
/**
* Returns a new generator whose internal state is an exact copy
* of this generator (therefore their future behavior should be
* identical if subjected to the same series of operations).
*
* @return a new object that is a copy of this generator
*/
public abstract AbstractArbitrarilyJumpableRng copy();
// Stream methods for jumping
/**
* Returns an effectively unlimited stream of new pseudorandom
* number generators, each of which implements the {@code Rng}
* interface, produced by jumping copies of this generator
* by different integer multiples of the default jump distance.
*
* @implNote This method is implemented to be equivalent to
* {@code jumps(Long.MAX_VALUE)}.
*
* @return a stream of objects that implement the {@code Rng} interface
*/
public Stream<Rng> jumps() {
return StreamSupport.stream
(makeJumpsSpliterator(0L, Long.MAX_VALUE, defaultJumpDistance()),
false);
}
/**
* Returns a stream producing the given {@code streamSize} number of
* new pseudorandom number generators, each of which implements the
* {@code Rng} interface, produced by jumping copies of this generator
* by different integer multiples of the default jump distance.
*
* @param streamSize the number of generators to generate
* @return a stream of objects that implement the {@code Rng} interface
* @throws IllegalArgumentException if {@code streamSize} is
* less than zero
*/
public Stream<Rng> jumps(long streamSize) {
return StreamSupport.stream
(makeJumpsSpliterator(0L, streamSize, defaultJumpDistance()),
false);
}
/**
* Returns an effectively unlimited stream of new pseudorandom
* number generators, each of which implements the {@code Rng}
* interface, produced by jumping copies of this generator
* by different integer multiples of the specified jump distance.
*
* @implNote This method is implemented to be equivalent to
* {@code jumps(Long.MAX_VALUE)}.
*
* @param distance a distance to jump forward within the state cycle
* @return a stream of objects that implement the {@code Rng} interface
*/
public Stream<ArbitrarilyJumpableRng> jumps(double distance) {
return StreamSupport.stream
(makeArbitraryJumpsSpliterator(0L, Long.MAX_VALUE, distance),
false);
}
/**
* Returns a stream producing the given {@code streamSize} number of
* new pseudorandom number generators, each of which implements the
* {@code Rng} interface, produced by jumping copies of this generator
* by different integer multiples of the specified jump distance.
*
* @param streamSize the number of generators to generate
* @param distance a distance to jump forward within the state cycle
* @return a stream of objects that implement the {@code Rng} interface
* @throws IllegalArgumentException if {@code streamSize} is
* less than zero
*/
public Stream<ArbitrarilyJumpableRng> jumps(long streamSize, double distance) {
RngSupport.checkStreamSize(streamSize);
return StreamSupport.stream
(makeArbitraryJumpsSpliterator(0L, streamSize, distance),
false);
}
/**
* Alter the state of this pseudorandom number generator so as to
* jump forward a very large, fixed distance (typically 2<sup>128</sup>
* or more) within its state cycle. The distance used is that
* returned by method {@code defaultLeapDistance()}.
*/
public void leap() { jump(defaultLeapDistance()); }
// Stream methods for leaping
/**
* Returns an effectively unlimited stream of new pseudorandom
* number generators, each of which implements the {@code Rng}
* interface, produced by jumping copies of this generator
* by different integer multiples of the default leap distance.
*
* @implNote This method is implemented to be equivalent to
* {@code leaps(Long.MAX_VALUE)}.
*
* @return a stream of objects that implement the {@code Rng} interface
*/
public Stream<JumpableRng> leaps() {
return StreamSupport.stream
(makeLeapsSpliterator(0L, Long.MAX_VALUE, defaultLeapDistance()),
false);
}
/**
* Returns a stream producing the given {@code streamSize} number of
* new pseudorandom number generators, each of which implements the
* {@code Rng} interface, produced by jumping copies of this generator
* by different integer multiples of the default leap distance.
*
* @param streamSize the number of generators to generate
* @return a stream of objects that implement the {@code Rng} interface
* @throws IllegalArgumentException if {@code streamSize} is
* less than zero
*/
public Stream<JumpableRng> leaps(long streamSize) {
return StreamSupport.stream
(makeLeapsSpliterator(0L, streamSize, defaultLeapDistance()),
false);
}
/**
* Spliterator for int streams. We multiplex the four int
* versions into one class by treating a bound less than origin as
* unbounded, and also by treating "infinite" as equivalent to
* Long.MAX_VALUE. For splits, we choose to override the method
* {@code trySplit()} to try to optimize execution speed: instead of
* dividing a range in half, it breaks off the largest possible chunk
* whose size is a power of two such that the remaining chunk is not
* empty. In this way, the necessary jump distances will tend to be
* powers of two. The long and double versions of this class are
* identical except for types.
*/
static class RandomIntsSpliterator extends RngSupport.RandomSpliterator implements Spliterator.OfInt {
final ArbitrarilyJumpableRng generatingRng;
final int origin;
final int bound;
RandomIntsSpliterator(ArbitrarilyJumpableRng generatingRng, long index, long fence, int origin, int bound) {
super(index, fence);
this.origin = origin; this.bound = bound;
this.generatingRng = generatingRng;
}
public Spliterator.OfInt trySplit() {
long i = index, delta = Long.highestOneBit((fence - i) - 1), m = i + delta;
if (m <= i) return null;
index = m;
ArbitrarilyJumpableRng r = (ArbitrarilyJumpableRng) generatingRng;
return new RandomIntsSpliterator(r.copyAndJump((double)delta), i, m, origin, bound);
}
public boolean tryAdvance(IntConsumer consumer) {
if (consumer == null) throw new NullPointerException();
long i = index, f = fence;
if (i < f) {
consumer.accept(RngSupport.boundedNextInt(generatingRng, origin, bound));
index = i + 1;
return true;
}
else return false;
}
public void forEachRemaining(IntConsumer consumer) {
if (consumer == null) throw new NullPointerException();
long i = index, f = fence;
if (i < f) {
index = f;
ArbitrarilyJumpableRng r = generatingRng;
int o = origin, b = bound;
do {
consumer.accept(RngSupport.boundedNextInt(r, o, b));
} while (++i < f);
}
}
}
/**
* Spliterator for long streams.
*/
static class RandomLongsSpliterator extends RngSupport.RandomSpliterator implements Spliterator.OfLong {
final ArbitrarilyJumpableRng generatingRng;
final long origin;
final long bound;
RandomLongsSpliterator(ArbitrarilyJumpableRng generatingRng, long index, long fence, long origin, long bound) {
super(index, fence);
this.generatingRng = generatingRng;
this.origin = origin; this.bound = bound;
}
public Spliterator.OfLong trySplit() {
long i = index, delta = Long.highestOneBit((fence - i) - 1), m = i + delta;
if (m <= i) return null;
index = m;
ArbitrarilyJumpableRng r = (ArbitrarilyJumpableRng) generatingRng;
return new RandomLongsSpliterator(r.copyAndJump((double)delta), i, m, origin, bound);
}
public boolean tryAdvance(LongConsumer consumer) {
if (consumer == null) throw new NullPointerException();
long i = index, f = fence;
if (i < f) {
consumer.accept(RngSupport.boundedNextLong(generatingRng, origin, bound));
index = i + 1;
return true;
}
else return false;
}
public void forEachRemaining(LongConsumer consumer) {
if (consumer == null) throw new NullPointerException();
long i = index, f = fence;
if (i < f) {
index = f;
ArbitrarilyJumpableRng r = generatingRng;
long o = origin, b = bound;
do {
consumer.accept(RngSupport.boundedNextLong(r, o, b));
} while (++i < f);
}
}
}
/**
* Spliterator for double streams.
*/
static class RandomDoublesSpliterator extends RngSupport.RandomSpliterator implements Spliterator.OfDouble {
final ArbitrarilyJumpableRng generatingRng;
final double origin;
final double bound;
RandomDoublesSpliterator(ArbitrarilyJumpableRng generatingRng, long index, long fence, double origin, double bound) {
super(index, fence);
this.generatingRng = generatingRng;
this.origin = origin; this.bound = bound;
}
public Spliterator.OfDouble trySplit() {
long i = index, delta = Long.highestOneBit((fence - i) - 1), m = i + delta;
if (m <= i) return null;
index = m;
ArbitrarilyJumpableRng r = (ArbitrarilyJumpableRng) generatingRng;
return new RandomDoublesSpliterator(r.copyAndJump((double)delta), i, m, origin, bound);
}
public boolean tryAdvance(DoubleConsumer consumer) {
if (consumer == null) throw new NullPointerException();
long i = index, f = fence;
if (i < f) {
consumer.accept(RngSupport.boundedNextDouble(generatingRng, origin, bound));
index = i + 1;
return true;
}
else return false;
}
public void forEachRemaining(DoubleConsumer consumer) {
if (consumer == null) throw new NullPointerException();
long i = index, f = fence;
if (i < f) {
index = f;
ArbitrarilyJumpableRng r = generatingRng;
double o = origin, b = bound;
do {
consumer.accept(RngSupport.boundedNextDouble(r, o, b));
} while (++i < f);
}
}
}
// Spliterators for producing new generators by jumping or leaping. The
// complete implementation of each of these spliterators is right here.
// In the same manner as for the preceding spliterators, the method trySplit() is
// coded to optimize execution speed: instead of dividing a range
// in half, it breaks off the largest possible chunk whose
// size is a power of two such that the remaining chunk is not
// empty. In this way, the necessary jump distances will tend to be
// powers of two.
/**
* Spliterator for stream of generators of type Rng produced by jumps.
*/
static class RandomJumpsSpliterator extends RngSupport.RandomSpliterator implements Spliterator<Rng> {
ArbitrarilyJumpableRng generatingRng;
final double distance;
RandomJumpsSpliterator(ArbitrarilyJumpableRng generatingRng, long index, long fence, double distance) {
super(index, fence);
this.generatingRng = generatingRng; this.distance = distance;
}
public Spliterator<Rng> trySplit() {
long i = index, delta = Long.highestOneBit((fence - i) - 1), m = i + delta;
if (m <= i) return null;
index = m;
ArbitrarilyJumpableRng r = (ArbitrarilyJumpableRng) generatingRng;
// Because delta is a power of two, (distance * (double)delta) can always be computed exactly.
return new RandomJumpsSpliterator(r.copyAndJump(distance * (double)delta), i, m, distance);
}
public boolean tryAdvance(Consumer<? super Rng> consumer) {
if (consumer == null) throw new NullPointerException();
long i = index, f = fence;
if (i < f) {
consumer.accept(generatingRng.copyAndJump(distance));
index = i + 1;
return true;
}
return false;
}
public void forEachRemaining(Consumer<? super Rng> consumer) {
if (consumer == null) throw new NullPointerException();
long i = index, f = fence;
if (i < f) {
index = f;
ArbitrarilyJumpableRng r = generatingRng;
do {
consumer.accept(r.copyAndJump(distance));
} while (++i < f);
}
}
}
/**
* Spliterator for stream of generators of type Rng produced by leaps.
*/
static class RandomLeapsSpliterator extends RngSupport.RandomSpliterator implements Spliterator<JumpableRng> {
ArbitrarilyJumpableRng generatingRng;
final double distance;
RandomLeapsSpliterator(ArbitrarilyJumpableRng generatingRng, long index, long fence, double distance) {
super(index, fence);
this.generatingRng = generatingRng; this.distance = distance;
}
public Spliterator<JumpableRng> trySplit() {
long i = index, delta = Long.highestOneBit((fence - i) - 1), m = i + delta;
if (m <= i) return null;
index = m;
// Because delta is a power of two, (distance * (double)delta) can always be computed exactly.
return new RandomLeapsSpliterator(generatingRng.copyAndJump(distance * (double)delta), i, m, distance);
}
public boolean tryAdvance(Consumer<? super JumpableRng> consumer) {
if (consumer == null) throw new NullPointerException();
long i = index, f = fence;
if (i < f) {
consumer.accept(generatingRng.copyAndJump(distance));
index = i + 1;
return true;
}
return false;
}
public void forEachRemaining(Consumer<? super JumpableRng> consumer) {
if (consumer == null) throw new NullPointerException();
long i = index, f = fence;
if (i < f) {
index = f;
ArbitrarilyJumpableRng r = generatingRng;
do {
consumer.accept(r.copyAndJump(distance));
} while (++i < f);
}
}
}
/**
* Spliterator for stream of generators of type Rng produced by arbitrary jumps.
*/
static class RandomArbitraryJumpsSpliterator extends RngSupport.RandomSpliterator implements Spliterator<ArbitrarilyJumpableRng> {
ArbitrarilyJumpableRng generatingRng;
final double distance;
RandomArbitraryJumpsSpliterator(ArbitrarilyJumpableRng generatingRng, long index, long fence, double distance) {
super(index, fence);
this.generatingRng = generatingRng; this.distance = distance;
}
public Spliterator<ArbitrarilyJumpableRng> trySplit() {
long i = index, delta = Long.highestOneBit((fence - i) - 1), m = i + delta;
if (m <= i) return null;
index = m;
// Because delta is a power of two, (distance * (double)delta) can always be computed exactly.
return new RandomArbitraryJumpsSpliterator(generatingRng.copyAndJump(distance * (double)delta), i, m, distance);
}
public boolean tryAdvance(Consumer<? super ArbitrarilyJumpableRng> consumer) {
if (consumer == null) throw new NullPointerException();
long i = index, f = fence;
if (i < f) {
consumer.accept(generatingRng.copyAndJump(distance));
index = i + 1;
return true;
}
return false;
}
public void forEachRemaining(Consumer<? super ArbitrarilyJumpableRng> consumer) {
if (consumer == null) throw new NullPointerException();
long i = index, f = fence;
if (i < f) {
index = f;
ArbitrarilyJumpableRng r = generatingRng;
do {
consumer.accept(r.copyAndJump(distance));
} while (++i < f);
}
}
}
}