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root/jsr166/jsr166/src/jsr166y/RecursiveAction.java
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Comparing jsr166/src/jsr166y/RecursiveAction.java (file contents):
Revision 1.4 by jsr166, Mon Jul 20 22:40:09 2009 UTC vs.
Revision 1.14 by dl, Sat Sep 18 19:53:08 2010 UTC

# Line 7 | Line 7
7   package jsr166y;
8  
9   /**
10 < * Recursive resultless ForkJoinTasks. This class establishes
11 < * conventions to parameterize resultless actions as {@code Void}
12 < * ForkJoinTasks. Because {@code null} is the only valid value of
13 < * {@code Void}, methods such as join always return {@code null}
14 < * upon completion.
10 > * A recursive resultless {@link ForkJoinTask}.  This class
11 > * establishes conventions to parameterize resultless actions as
12 > * {@code Void} {@code ForkJoinTask}s. Because {@code null} is the
13 > * only valid value of type {@code Void}, methods such as join always
14 > * return {@code null} upon completion.
15   *
16   * <p><b>Sample Usages.</b> Here is a sketch of a ForkJoin sort that
17   * sorts a given {@code long[]} array:
# Line 34 | Line 34 | package jsr166y;
34   *   }
35   * }}</pre>
36   *
37 < * You could then sort anArray by creating {@code new SortTask(anArray, 0,
38 < * anArray.length-1) } and invoking it in a ForkJoinPool.
39 < * As a more concrete simple example, the following task increments
40 < * each element of an array:
37 > * You could then sort {@code anArray} by creating {@code new
38 > * SortTask(anArray, 0, anArray.length-1) } and invoking it in a
39 > * ForkJoinPool.  As a more concrete simple example, the following
40 > * task increments each element of an array:
41   *  <pre> {@code
42   * class IncrementTask extends RecursiveAction {
43   *   final long[] array; final int lo; final int hi;
# Line 64 | Line 64 | package jsr166y;
64   * of each element of a double array, by subdividing out only the
65   * right-hand-sides of repeated divisions by two, and keeping track of
66   * them with a chain of {@code next} references. It uses a dynamic
67 < * threshold based on method {@code surplus}, but counterbalances
68 < * potential excess partitioning by directly performing leaf actions
69 < * on unstolen tasks rather than further subdividing.
67 > * threshold based on method {@code getSurplusQueuedTaskCount}, but
68 > * counterbalances potential excess partitioning by directly
69 > * performing leaf actions on unstolen tasks rather than further
70 > * subdividing.
71   *
72   *  <pre> {@code
73   * double sumOfSquares(ForkJoinPool pool, double[] array) {
74   *   int n = array.length;
75 < *   int seqSize = 1 + n / (8 * pool.getParallelism());
75 < *   Applyer a = new Applyer(array, 0, n, seqSize, null);
75 > *   Applyer a = new Applyer(array, 0, n, null);
76   *   pool.invoke(a);
77   *   return a.result;
78   * }
79   *
80   * class Applyer extends RecursiveAction {
81   *   final double[] array;
82 < *   final int lo, hi, seqSize;
82 > *   final int lo, hi;
83   *   double result;
84   *   Applyer next; // keeps track of right-hand-side tasks
85 < *   Applyer(double[] array, int lo, int hi, int seqSize, Applyer next) {
85 > *   Applyer(double[] array, int lo, int hi, Applyer next) {
86   *     this.array = array; this.lo = lo; this.hi = hi;
87 < *     this.seqSize = seqSize; this.next = next;
87 > *     this.next = next;
88   *   }
89   *
90 < *   double atLeaf(int l, int r) {
90 > *   double atLeaf(int l, int h) {
91   *     double sum = 0;
92   *     for (int i = l; i < h; ++i) // perform leftmost base step
93   *       sum += array[i] * array[i];
# Line 98 | Line 98 | package jsr166y;
98   *     int l = lo;
99   *     int h = hi;
100   *     Applyer right = null;
101 < *     while (h - l > 1 &&
102 < *        ForkJoinWorkerThread.getEstimatedSurplusTaskCount() <= 3) {
101 > *     while (h - l > 1 && getSurplusQueuedTaskCount() <= 3) {
102   *        int mid = (l + h) >>> 1;
103 < *        right = new Applyer(array, mid, h, seqSize, right);
103 > *        right = new Applyer(array, mid, h, right);
104   *        right.fork();
105   *        h = mid;
106   *     }
# Line 110 | Line 109 | package jsr166y;
109   *        if (right.tryUnfork()) // directly calculate if not stolen
110   *          sum += right.atLeaf(right.lo, right.hi);
111   *       else {
112 < *          right.helpJoin();
112 > *          right.join();
113   *          sum += right.result;
114   *        }
115   *        right = right.next;
# Line 118 | Line 117 | package jsr166y;
117   *     result = sum;
118   *   }
119   * }}</pre>
120 + *
121 + * @since 1.7
122 + * @author Doug Lea
123   */
124   public abstract class RecursiveAction extends ForkJoinTask<Void> {
125 +    private static final long serialVersionUID = 5232453952276485070L;
126  
127      /**
128       * The main computation performed by this task.
# Line 127 | Line 130 | public abstract class RecursiveAction ex
130      protected abstract void compute();
131  
132      /**
133 <     * Always returns null
133 >     * Always returns null.
134       */
135      public final Void getRawResult() { return null; }
136  
# Line 137 | Line 140 | public abstract class RecursiveAction ex
140      protected final void setRawResult(Void mustBeNull) { }
141  
142      /**
143 <     * Implements execution conventions for RecursiveActions
143 >     * Implements execution conventions for RecursiveActions.
144       */
145      protected final boolean exec() {
146          compute();

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