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Diffstat (limited to 'src/forkjoin/scala/concurrent/forkjoin/ThreadLocalRandom.java')
-rw-r--r-- | src/forkjoin/scala/concurrent/forkjoin/ThreadLocalRandom.java | 197 |
1 files changed, 0 insertions, 197 deletions
diff --git a/src/forkjoin/scala/concurrent/forkjoin/ThreadLocalRandom.java b/src/forkjoin/scala/concurrent/forkjoin/ThreadLocalRandom.java deleted file mode 100644 index a7ef492057..0000000000 --- a/src/forkjoin/scala/concurrent/forkjoin/ThreadLocalRandom.java +++ /dev/null @@ -1,197 +0,0 @@ -/* - * Written by Doug Lea with assistance from members of JCP JSR-166 - * Expert Group and released to the public domain, as explained at - * http://creativecommons.org/publicdomain/zero/1.0/ - */ - -package scala.concurrent.forkjoin; - -import java.util.Random; - -/** - * A random number generator isolated to the current thread. Like the - * global {@link java.util.Random} generator used by the {@link - * java.lang.Math} class, a {@code ThreadLocalRandom} is initialized - * with an internally generated seed that may not otherwise be - * modified. When applicable, use of {@code ThreadLocalRandom} rather - * than shared {@code Random} objects in concurrent programs will - * typically encounter much less overhead and contention. Use of - * {@code ThreadLocalRandom} is particularly appropriate when multiple - * tasks (for example, each a {@link ForkJoinTask}) use random numbers - * in parallel in thread pools. - * - * <p>Usages of this class should typically be of the form: - * {@code ThreadLocalRandom.current().nextX(...)} (where - * {@code X} is {@code Int}, {@code Long}, etc). - * When all usages are of this form, it is never possible to - * accidentally share a {@code ThreadLocalRandom} across multiple threads. - * - * <p>This class also provides additional commonly used bounded random - * generation methods. - * - * @since 1.7 - * @author Doug Lea - */ -public class ThreadLocalRandom extends Random { - // same constants as Random, but must be redeclared because private - private static final long multiplier = 0x5DEECE66DL; - private static final long addend = 0xBL; - private static final long mask = (1L << 48) - 1; - - /** - * The random seed. We can't use super.seed. - */ - private long rnd; - - /** - * Initialization flag to permit calls to setSeed to succeed only - * while executing the Random constructor. We can't allow others - * since it would cause setting seed in one part of a program to - * unintentionally impact other usages by the thread. - */ - boolean initialized; - - // Padding to help avoid memory contention among seed updates in - // different TLRs in the common case that they are located near - // each other. - private long pad0, pad1, pad2, pad3, pad4, pad5, pad6, pad7; - - /** - * The actual ThreadLocal - */ - private static final ThreadLocal<ThreadLocalRandom> localRandom = - new ThreadLocal<ThreadLocalRandom>() { - protected ThreadLocalRandom initialValue() { - return new ThreadLocalRandom(); - } - }; - - - /** - * Constructor called only by localRandom.initialValue. - */ - ThreadLocalRandom() { - super(); - initialized = true; - } - - /** - * Returns the current thread's {@code ThreadLocalRandom}. - * - * @return the current thread's {@code ThreadLocalRandom} - */ - public static ThreadLocalRandom current() { - return localRandom.get(); - } - - /** - * Throws {@code UnsupportedOperationException}. Setting seeds in - * this generator is not supported. - * - * @throws UnsupportedOperationException always - */ - public void setSeed(long seed) { - if (initialized) - throw new UnsupportedOperationException(); - rnd = (seed ^ multiplier) & mask; - } - - protected int next(int bits) { - rnd = (rnd * multiplier + addend) & mask; - return (int) (rnd >>> (48-bits)); - } - - /** - * Returns a pseudorandom, uniformly distributed value between the - * given least value (inclusive) and bound (exclusive). - * - * @param least the least value returned - * @param bound the upper bound (exclusive) - * @throws IllegalArgumentException if least greater than or equal - * to bound - * @return the next value - */ - public int nextInt(int least, int bound) { - if (least >= bound) - throw new IllegalArgumentException(); - return nextInt(bound - least) + least; - } - - /** - * Returns a pseudorandom, uniformly distributed value - * between 0 (inclusive) and the specified value (exclusive). - * - * @param n the bound on the random number to be returned. Must be - * positive. - * @return the next value - * @throws IllegalArgumentException if n is not positive - */ - public long nextLong(long n) { - if (n <= 0) - throw new IllegalArgumentException("n must be positive"); - // Divide n by two until small enough for nextInt. On each - // iteration (at most 31 of them but usually much less), - // randomly choose both whether to include high bit in result - // (offset) and whether to continue with the lower vs upper - // half (which makes a difference only if odd). - long offset = 0; - while (n >= Integer.MAX_VALUE) { - int bits = next(2); - long half = n >>> 1; - long nextn = ((bits & 2) == 0) ? half : n - half; - if ((bits & 1) == 0) - offset += n - nextn; - n = nextn; - } - return offset + nextInt((int) n); - } - - /** - * Returns a pseudorandom, uniformly distributed value between the - * given least value (inclusive) and bound (exclusive). - * - * @param least the least value returned - * @param bound the upper bound (exclusive) - * @return the next value - * @throws IllegalArgumentException if least greater than or equal - * to bound - */ - public long nextLong(long least, long bound) { - if (least >= bound) - throw new IllegalArgumentException(); - return nextLong(bound - least) + least; - } - - /** - * Returns a pseudorandom, uniformly distributed {@code double} value - * between 0 (inclusive) and the specified value (exclusive). - * - * @param n the bound on the random number to be returned. Must be - * positive. - * @return the next value - * @throws IllegalArgumentException if n is not positive - */ - public double nextDouble(double n) { - if (n <= 0) - throw new IllegalArgumentException("n must be positive"); - return nextDouble() * n; - } - - /** - * Returns a pseudorandom, uniformly distributed value between the - * given least value (inclusive) and bound (exclusive). - * - * @param least the least value returned - * @param bound the upper bound (exclusive) - * @return the next value - * @throws IllegalArgumentException if least greater than or equal - * to bound - */ - public double nextDouble(double least, double bound) { - if (least >= bound) - throw new IllegalArgumentException(); - return nextDouble() * (bound - least) + least; - } - - private static final long serialVersionUID = -5851777807851030925L; -} |