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/* |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain, as explained at |
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* http://creativecommons.org/publicdomain/zero/1.0/ |
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*/ |
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|
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package java.util; |
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|
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import java.util.concurrent.CountedCompleter; |
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import java.util.function.BinaryOperator; |
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import java.util.function.DoubleBinaryOperator; |
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import java.util.function.IntBinaryOperator; |
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import java.util.function.LongBinaryOperator; |
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|
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/** |
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* ForkJoin tasks to perform Arrays.parallelPrefix operations. |
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* |
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* @author Doug Lea |
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* @since 1.8 |
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*/ |
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class ArrayPrefixHelpers { |
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private ArrayPrefixHelpers() {} // non-instantiable |
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|
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/* |
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* Parallel prefix (aka cumulate, scan) task classes |
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* are based loosely on Guy Blelloch's original |
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* algorithm (http://www.cs.cmu.edu/~scandal/alg/scan.html): |
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* Keep dividing by two to threshold segment size, and then: |
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* Pass 1: Create tree of partial sums for each segment |
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* Pass 2: For each segment, cumulate with offset of left sibling |
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* |
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* This version improves performance within FJ framework mainly by |
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* allowing the second pass of ready left-hand sides to proceed |
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* even if some right-hand side first passes are still executing. |
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* It also combines first and second pass for leftmost segment, |
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* and skips the first pass for rightmost segment (whose result is |
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* not needed for second pass). It similarly manages to avoid |
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* requiring that users supply an identity basis for accumulations |
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* by tracking those segments/subtasks for which the first |
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* existing element is used as base. |
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* |
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* Managing this relies on ORing some bits in the pendingCount for |
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* phases/states: CUMULATE, SUMMED, and FINISHED. CUMULATE is the |
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* main phase bit. When false, segments compute only their sum. |
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* When true, they cumulate array elements. CUMULATE is set at |
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* root at beginning of second pass and then propagated down. But |
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* it may also be set earlier for subtrees with lo==0 (the left |
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* spine of tree). SUMMED is a one bit join count. For leafs, it |
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* is set when summed. For internal nodes, it becomes true when |
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* one child is summed. When the second child finishes summing, |
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* we then moves up tree to trigger the cumulate phase. FINISHED |
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* is also a one bit join count. For leafs, it is set when |
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* cumulated. For internal nodes, it becomes true when one child |
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* is cumulated. When the second child finishes cumulating, it |
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* then moves up tree, completing at the root. |
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* |
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* To better exploit locality and reduce overhead, the compute |
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* method loops starting with the current task, moving if possible |
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* to one of its subtasks rather than forking. |
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* |
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* As usual for this sort of utility, there are 4 versions, that |
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* are simple copy/paste/adapt variants of each other. (The |
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* double and int versions differ from long version solely by |
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* replacing "long" (with case-matching)). |
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*/ |
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|
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// see above |
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static final int CUMULATE = 1; |
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static final int SUMMED = 2; |
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static final int FINISHED = 4; |
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|
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/** The smallest subtask array partition size to use as threshold */ |
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static final int MIN_PARTITION = 16; |
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|
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private static final class CumulateTask<T> |
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extends CountedCompleter<Void> { |
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final T[] array; |
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final BinaryOperator<T> function; |
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CumulateTask<T> left, right; |
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T in, out; |
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final int lo, hi, origin, fence, threshold; |
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|
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CumulateTask(CumulateTask<T> parent, BinaryOperator<T> function, |
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T[] array, int origin, int fence, int threshold, |
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int lo, int hi) { |
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super(parent); |
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this.function = function; this.array = array; |
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this.origin = origin; this.fence = fence; |
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this.threshold = threshold; |
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this.lo = lo; this.hi = hi; |
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} |
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|
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public final void compute() { |
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final BinaryOperator<T> fn; |
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final T[] a; |
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if ((fn = this.function) == null || (a = this.array) == null) |
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throw new NullPointerException(); // hoist checks |
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int th = threshold, org = origin, fnc = fence, l, h; |
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CumulateTask<T> t = this; |
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outer: while ((l = t.lo) >= 0 && (h = t.hi) <= a.length) { |
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if (h - l > th) { |
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CumulateTask<T> lt = t.left, rt = t.right, f; |
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if (lt == null) { // first pass |
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int mid = (l + h) >>> 1; |
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f = rt = t.right = |
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new CumulateTask<T>(t, fn, a, org, fnc, th, mid, h); |
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t = lt = t.left = |
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new CumulateTask<T>(t, fn, a, org, fnc, th, l, mid); |
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} |
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else { // possibly refork |
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T pin = t.in; |
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lt.in = pin; |
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f = t = null; |
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if (rt != null) { |
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T lout = lt.out; |
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rt.in = (l == org ? lout : |
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fn.apply(pin, lout)); |
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for (int c;;) { |
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if (((c = rt.getPendingCount()) & CUMULATE) != 0) |
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break; |
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if (rt.compareAndSetPendingCount(c, c|CUMULATE)){ |
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t = rt; |
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break; |
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} |
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} |
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} |
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for (int c;;) { |
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if (((c = lt.getPendingCount()) & CUMULATE) != 0) |
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break; |
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if (lt.compareAndSetPendingCount(c, c|CUMULATE)) { |
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if (t != null) |
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f = t; |
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t = lt; |
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break; |
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} |
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} |
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if (t == null) |
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break; |
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} |
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if (f != null) |
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f.fork(); |
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} |
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else { |
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int state; // Transition to sum, cumulate, or both |
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for (int b;;) { |
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if (((b = t.getPendingCount()) & FINISHED) != 0) |
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break outer; // already done |
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state = ((b & CUMULATE) != 0 ? FINISHED : |
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(l > org) ? SUMMED : (SUMMED|FINISHED)); |
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if (t.compareAndSetPendingCount(b, b|state)) |
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break; |
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} |
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|
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T sum; |
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if (state != SUMMED) { |
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int first; |
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if (l == org) { // leftmost; no in |
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sum = a[org]; |
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first = org + 1; |
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} |
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else { |
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sum = t.in; |
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first = l; |
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} |
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for (int i = first; i < h; ++i) // cumulate |
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a[i] = sum = fn.apply(sum, a[i]); |
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} |
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else if (h < fnc) { // skip rightmost |
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sum = a[l]; |
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for (int i = l + 1; i < h; ++i) // sum only |
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sum = fn.apply(sum, a[i]); |
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} |
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else |
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sum = t.in; |
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t.out = sum; |
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for (CumulateTask<T> par;;) { // propagate |
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@SuppressWarnings("unchecked") CumulateTask<T> partmp |
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= (CumulateTask<T>)t.getCompleter(); |
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if ((par = partmp) == null) { |
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if ((state & FINISHED) != 0) // enable join |
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t.quietlyComplete(); |
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break outer; |
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} |
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int b = par.getPendingCount(); |
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if ((b & state & FINISHED) != 0) |
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t = par; // both done |
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else if ((b & state & SUMMED) != 0) { // both summed |
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int nextState; CumulateTask<T> lt, rt; |
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if ((lt = par.left) != null && |
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(rt = par.right) != null) { |
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T lout = lt.out; |
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par.out = (rt.hi == fnc ? lout : |
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fn.apply(lout, rt.out)); |
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} |
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int refork = (((b & CUMULATE) == 0 && |
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par.lo == org) ? CUMULATE : 0); |
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if ((nextState = b|state|refork) == b || |
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par.compareAndSetPendingCount(b, nextState)) { |
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state = SUMMED; // drop finished |
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t = par; |
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if (refork != 0) |
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par.fork(); |
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} |
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} |
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else if (par.compareAndSetPendingCount(b, b|state)) |
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break outer; // sib not ready |
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} |
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} |
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} |
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} |
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private static final long serialVersionUID = 5293554502939613543L; |
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} |
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|
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private static final class LongCumulateTask |
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extends CountedCompleter<Void> { |
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final long[] array; |
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final LongBinaryOperator function; |
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LongCumulateTask left, right; |
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long in, out; |
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final int lo, hi, origin, fence, threshold; |
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|
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LongCumulateTask(LongCumulateTask parent, LongBinaryOperator function, |
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long[] array, int origin, int fence, int threshold, |
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int lo, int hi) { |
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super(parent); |
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this.function = function; this.array = array; |
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this.origin = origin; this.fence = fence; |
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this.threshold = threshold; |
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this.lo = lo; this.hi = hi; |
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} |
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|
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public final void compute() { |
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final LongBinaryOperator fn; |
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final long[] a; |
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if ((fn = this.function) == null || (a = this.array) == null) |
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throw new NullPointerException(); // hoist checks |
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int th = threshold, org = origin, fnc = fence, l, h; |
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LongCumulateTask t = this; |
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outer: while ((l = t.lo) >= 0 && (h = t.hi) <= a.length) { |
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if (h - l > th) { |
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LongCumulateTask lt = t.left, rt = t.right, f; |
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if (lt == null) { // first pass |
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int mid = (l + h) >>> 1; |
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f = rt = t.right = |
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new LongCumulateTask(t, fn, a, org, fnc, th, mid, h); |
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t = lt = t.left = |
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new LongCumulateTask(t, fn, a, org, fnc, th, l, mid); |
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} |
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else { // possibly refork |
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long pin = t.in; |
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lt.in = pin; |
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f = t = null; |
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if (rt != null) { |
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long lout = lt.out; |
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rt.in = (l == org ? lout : |
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fn.applyAsLong(pin, lout)); |
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for (int c;;) { |
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if (((c = rt.getPendingCount()) & CUMULATE) != 0) |
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break; |
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if (rt.compareAndSetPendingCount(c, c|CUMULATE)){ |
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t = rt; |
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break; |
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} |
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} |
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} |
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for (int c;;) { |
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if (((c = lt.getPendingCount()) & CUMULATE) != 0) |
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break; |
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if (lt.compareAndSetPendingCount(c, c|CUMULATE)) { |
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if (t != null) |
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f = t; |
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t = lt; |
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break; |
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} |
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} |
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if (t == null) |
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break; |
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} |
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if (f != null) |
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f.fork(); |
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} |
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else { |
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int state; // Transition to sum, cumulate, or both |
284 |
for (int b;;) { |
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if (((b = t.getPendingCount()) & FINISHED) != 0) |
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break outer; // already done |
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state = ((b & CUMULATE) != 0 ? FINISHED : |
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(l > org) ? SUMMED : (SUMMED|FINISHED)); |
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if (t.compareAndSetPendingCount(b, b|state)) |
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break; |
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} |
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|
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long sum; |
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if (state != SUMMED) { |
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int first; |
296 |
if (l == org) { // leftmost; no in |
297 |
sum = a[org]; |
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first = org + 1; |
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} |
300 |
else { |
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sum = t.in; |
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first = l; |
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} |
304 |
for (int i = first; i < h; ++i) // cumulate |
305 |
a[i] = sum = fn.applyAsLong(sum, a[i]); |
306 |
} |
307 |
else if (h < fnc) { // skip rightmost |
308 |
sum = a[l]; |
309 |
for (int i = l + 1; i < h; ++i) // sum only |
310 |
sum = fn.applyAsLong(sum, a[i]); |
311 |
} |
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else |
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sum = t.in; |
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t.out = sum; |
315 |
for (LongCumulateTask par;;) { // propagate |
316 |
if ((par = (LongCumulateTask)t.getCompleter()) == null) { |
317 |
if ((state & FINISHED) != 0) // enable join |
318 |
t.quietlyComplete(); |
319 |
break outer; |
320 |
} |
321 |
int b = par.getPendingCount(); |
322 |
if ((b & state & FINISHED) != 0) |
323 |
t = par; // both done |
324 |
else if ((b & state & SUMMED) != 0) { // both summed |
325 |
int nextState; LongCumulateTask lt, rt; |
326 |
if ((lt = par.left) != null && |
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(rt = par.right) != null) { |
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long lout = lt.out; |
329 |
par.out = (rt.hi == fnc ? lout : |
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fn.applyAsLong(lout, rt.out)); |
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} |
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int refork = (((b & CUMULATE) == 0 && |
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par.lo == org) ? CUMULATE : 0); |
334 |
if ((nextState = b|state|refork) == b || |
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par.compareAndSetPendingCount(b, nextState)) { |
336 |
state = SUMMED; // drop finished |
337 |
t = par; |
338 |
if (refork != 0) |
339 |
par.fork(); |
340 |
} |
341 |
} |
342 |
else if (par.compareAndSetPendingCount(b, b|state)) |
343 |
break outer; // sib not ready |
344 |
} |
345 |
} |
346 |
} |
347 |
} |
348 |
private static final long serialVersionUID = -5074099945909284273L; |
349 |
} |
350 |
|
351 |
private static final class DoubleCumulateTask |
352 |
extends CountedCompleter<Void> { |
353 |
final double[] array; |
354 |
final DoubleBinaryOperator function; |
355 |
DoubleCumulateTask left, right; |
356 |
double in, out; |
357 |
final int lo, hi, origin, fence, threshold; |
358 |
|
359 |
DoubleCumulateTask(DoubleCumulateTask parent, DoubleBinaryOperator function, |
360 |
double[] array, int origin, int fence, int threshold, |
361 |
int lo, int hi) { |
362 |
super(parent); |
363 |
this.function = function; this.array = array; |
364 |
this.origin = origin; this.fence = fence; |
365 |
this.threshold = threshold; |
366 |
this.lo = lo; this.hi = hi; |
367 |
} |
368 |
|
369 |
public final void compute() { |
370 |
final DoubleBinaryOperator fn; |
371 |
final double[] a; |
372 |
if ((fn = this.function) == null || (a = this.array) == null) |
373 |
throw new NullPointerException(); // hoist checks |
374 |
int th = threshold, org = origin, fnc = fence, l, h; |
375 |
DoubleCumulateTask t = this; |
376 |
outer: while ((l = t.lo) >= 0 && (h = t.hi) <= a.length) { |
377 |
if (h - l > th) { |
378 |
DoubleCumulateTask lt = t.left, rt = t.right, f; |
379 |
if (lt == null) { // first pass |
380 |
int mid = (l + h) >>> 1; |
381 |
f = rt = t.right = |
382 |
new DoubleCumulateTask(t, fn, a, org, fnc, th, mid, h); |
383 |
t = lt = t.left = |
384 |
new DoubleCumulateTask(t, fn, a, org, fnc, th, l, mid); |
385 |
} |
386 |
else { // possibly refork |
387 |
double pin = t.in; |
388 |
lt.in = pin; |
389 |
f = t = null; |
390 |
if (rt != null) { |
391 |
double lout = lt.out; |
392 |
rt.in = (l == org ? lout : |
393 |
fn.applyAsDouble(pin, lout)); |
394 |
for (int c;;) { |
395 |
if (((c = rt.getPendingCount()) & CUMULATE) != 0) |
396 |
break; |
397 |
if (rt.compareAndSetPendingCount(c, c|CUMULATE)){ |
398 |
t = rt; |
399 |
break; |
400 |
} |
401 |
} |
402 |
} |
403 |
for (int c;;) { |
404 |
if (((c = lt.getPendingCount()) & CUMULATE) != 0) |
405 |
break; |
406 |
if (lt.compareAndSetPendingCount(c, c|CUMULATE)) { |
407 |
if (t != null) |
408 |
f = t; |
409 |
t = lt; |
410 |
break; |
411 |
} |
412 |
} |
413 |
if (t == null) |
414 |
break; |
415 |
} |
416 |
if (f != null) |
417 |
f.fork(); |
418 |
} |
419 |
else { |
420 |
int state; // Transition to sum, cumulate, or both |
421 |
for (int b;;) { |
422 |
if (((b = t.getPendingCount()) & FINISHED) != 0) |
423 |
break outer; // already done |
424 |
state = ((b & CUMULATE) != 0 ? FINISHED : |
425 |
(l > org) ? SUMMED : (SUMMED|FINISHED)); |
426 |
if (t.compareAndSetPendingCount(b, b|state)) |
427 |
break; |
428 |
} |
429 |
|
430 |
double sum; |
431 |
if (state != SUMMED) { |
432 |
int first; |
433 |
if (l == org) { // leftmost; no in |
434 |
sum = a[org]; |
435 |
first = org + 1; |
436 |
} |
437 |
else { |
438 |
sum = t.in; |
439 |
first = l; |
440 |
} |
441 |
for (int i = first; i < h; ++i) // cumulate |
442 |
a[i] = sum = fn.applyAsDouble(sum, a[i]); |
443 |
} |
444 |
else if (h < fnc) { // skip rightmost |
445 |
sum = a[l]; |
446 |
for (int i = l + 1; i < h; ++i) // sum only |
447 |
sum = fn.applyAsDouble(sum, a[i]); |
448 |
} |
449 |
else |
450 |
sum = t.in; |
451 |
t.out = sum; |
452 |
for (DoubleCumulateTask par;;) { // propagate |
453 |
if ((par = (DoubleCumulateTask)t.getCompleter()) == null) { |
454 |
if ((state & FINISHED) != 0) // enable join |
455 |
t.quietlyComplete(); |
456 |
break outer; |
457 |
} |
458 |
int b = par.getPendingCount(); |
459 |
if ((b & state & FINISHED) != 0) |
460 |
t = par; // both done |
461 |
else if ((b & state & SUMMED) != 0) { // both summed |
462 |
int nextState; DoubleCumulateTask lt, rt; |
463 |
if ((lt = par.left) != null && |
464 |
(rt = par.right) != null) { |
465 |
double lout = lt.out; |
466 |
par.out = (rt.hi == fnc ? lout : |
467 |
fn.applyAsDouble(lout, rt.out)); |
468 |
} |
469 |
int refork = (((b & CUMULATE) == 0 && |
470 |
par.lo == org) ? CUMULATE : 0); |
471 |
if ((nextState = b|state|refork) == b || |
472 |
par.compareAndSetPendingCount(b, nextState)) { |
473 |
state = SUMMED; // drop finished |
474 |
t = par; |
475 |
if (refork != 0) |
476 |
par.fork(); |
477 |
} |
478 |
} |
479 |
else if (par.compareAndSetPendingCount(b, b|state)) |
480 |
break outer; // sib not ready |
481 |
} |
482 |
} |
483 |
} |
484 |
} |
485 |
private static final long serialVersionUID = -586947823794232033L; |
486 |
} |
487 |
|
488 |
private static final class IntCumulateTask |
489 |
extends CountedCompleter<Void> { |
490 |
final int[] array; |
491 |
final IntBinaryOperator function; |
492 |
IntCumulateTask left, right; |
493 |
int in, out; |
494 |
final int lo, hi, origin, fence, threshold; |
495 |
|
496 |
IntCumulateTask(IntCumulateTask parent, IntBinaryOperator function, |
497 |
int[] array, int origin, int fence, int threshold, |
498 |
int lo, int hi) { |
499 |
super(parent); |
500 |
this.function = function; this.array = array; |
501 |
this.origin = origin; this.fence = fence; |
502 |
this.threshold = threshold; |
503 |
this.lo = lo; this.hi = hi; |
504 |
} |
505 |
|
506 |
public final void compute() { |
507 |
final IntBinaryOperator fn; |
508 |
final int[] a; |
509 |
if ((fn = this.function) == null || (a = this.array) == null) |
510 |
throw new NullPointerException(); // hoist checks |
511 |
int th = threshold, org = origin, fnc = fence, l, h; |
512 |
IntCumulateTask t = this; |
513 |
outer: while ((l = t.lo) >= 0 && (h = t.hi) <= a.length) { |
514 |
if (h - l > th) { |
515 |
IntCumulateTask lt = t.left, rt = t.right, f; |
516 |
if (lt == null) { // first pass |
517 |
int mid = (l + h) >>> 1; |
518 |
f = rt = t.right = |
519 |
new IntCumulateTask(t, fn, a, org, fnc, th, mid, h); |
520 |
t = lt = t.left = |
521 |
new IntCumulateTask(t, fn, a, org, fnc, th, l, mid); |
522 |
} |
523 |
else { // possibly refork |
524 |
int pin = t.in; |
525 |
lt.in = pin; |
526 |
f = t = null; |
527 |
if (rt != null) { |
528 |
int lout = lt.out; |
529 |
rt.in = (l == org ? lout : |
530 |
fn.applyAsInt(pin, lout)); |
531 |
for (int c;;) { |
532 |
if (((c = rt.getPendingCount()) & CUMULATE) != 0) |
533 |
break; |
534 |
if (rt.compareAndSetPendingCount(c, c|CUMULATE)){ |
535 |
t = rt; |
536 |
break; |
537 |
} |
538 |
} |
539 |
} |
540 |
for (int c;;) { |
541 |
if (((c = lt.getPendingCount()) & CUMULATE) != 0) |
542 |
break; |
543 |
if (lt.compareAndSetPendingCount(c, c|CUMULATE)) { |
544 |
if (t != null) |
545 |
f = t; |
546 |
t = lt; |
547 |
break; |
548 |
} |
549 |
} |
550 |
if (t == null) |
551 |
break; |
552 |
} |
553 |
if (f != null) |
554 |
f.fork(); |
555 |
} |
556 |
else { |
557 |
int state; // Transition to sum, cumulate, or both |
558 |
for (int b;;) { |
559 |
if (((b = t.getPendingCount()) & FINISHED) != 0) |
560 |
break outer; // already done |
561 |
state = ((b & CUMULATE) != 0 ? FINISHED : |
562 |
(l > org) ? SUMMED : (SUMMED|FINISHED)); |
563 |
if (t.compareAndSetPendingCount(b, b|state)) |
564 |
break; |
565 |
} |
566 |
|
567 |
int sum; |
568 |
if (state != SUMMED) { |
569 |
int first; |
570 |
if (l == org) { // leftmost; no in |
571 |
sum = a[org]; |
572 |
first = org + 1; |
573 |
} |
574 |
else { |
575 |
sum = t.in; |
576 |
first = l; |
577 |
} |
578 |
for (int i = first; i < h; ++i) // cumulate |
579 |
a[i] = sum = fn.applyAsInt(sum, a[i]); |
580 |
} |
581 |
else if (h < fnc) { // skip rightmost |
582 |
sum = a[l]; |
583 |
for (int i = l + 1; i < h; ++i) // sum only |
584 |
sum = fn.applyAsInt(sum, a[i]); |
585 |
} |
586 |
else |
587 |
sum = t.in; |
588 |
t.out = sum; |
589 |
for (IntCumulateTask par;;) { // propagate |
590 |
if ((par = (IntCumulateTask)t.getCompleter()) == null) { |
591 |
if ((state & FINISHED) != 0) // enable join |
592 |
t.quietlyComplete(); |
593 |
break outer; |
594 |
} |
595 |
int b = par.getPendingCount(); |
596 |
if ((b & state & FINISHED) != 0) |
597 |
t = par; // both done |
598 |
else if ((b & state & SUMMED) != 0) { // both summed |
599 |
int nextState; IntCumulateTask lt, rt; |
600 |
if ((lt = par.left) != null && |
601 |
(rt = par.right) != null) { |
602 |
int lout = lt.out; |
603 |
par.out = (rt.hi == fnc ? lout : |
604 |
fn.applyAsInt(lout, rt.out)); |
605 |
} |
606 |
int refork = (((b & CUMULATE) == 0 && |
607 |
par.lo == org) ? CUMULATE : 0); |
608 |
if ((nextState = b|state|refork) == b || |
609 |
par.compareAndSetPendingCount(b, nextState)) { |
610 |
state = SUMMED; // drop finished |
611 |
t = par; |
612 |
if (refork != 0) |
613 |
par.fork(); |
614 |
} |
615 |
} |
616 |
else if (par.compareAndSetPendingCount(b, b|state)) |
617 |
break outer; // sib not ready |
618 |
} |
619 |
} |
620 |
} |
621 |
} |
622 |
private static final long serialVersionUID = 3731755594596840961L; |
623 |
} |
624 |
|
625 |
} |