| 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]; |
| 100 |
|
* Applyer right = null; |
| 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 |
|
* } |
| 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; |
| 130 |
|
protected abstract void compute(); |
| 131 |
|
|
| 132 |
|
/** |
| 133 |
< |
* Always returns null. |
| 133 |
> |
* Always returns {@code null}. |
| 134 |
> |
* |
| 135 |
> |
* @return {@code null} always |
| 136 |
|
*/ |
| 137 |
|
public final Void getRawResult() { return null; } |
| 138 |
|
|
