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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.concurrent.ForkJoinPool; |
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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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static final class CumulateTask<T> 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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static final class LongCumulateTask 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 |
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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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long 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.applyAsLong(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.applyAsLong(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 (LongCumulateTask par;;) { // propagate |
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if ((par = (LongCumulateTask)t.getCompleter()) == 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; LongCumulateTask lt, rt; |
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if ((lt = par.left) != null && |
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(rt = par.right) != null) { |
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long lout = lt.out; |
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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); |
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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; |
| 337 |
if (refork != 0) |
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par.fork(); |
| 339 |
} |
| 340 |
} |
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else if (par.compareAndSetPendingCount(b, b|state)) |
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break outer; // sib not ready |
| 343 |
} |
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} |
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} |
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} |
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private static final long serialVersionUID = -5074099945909284273L; |
| 348 |
} |
| 349 |
|
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static final class DoubleCumulateTask extends CountedCompleter<Void> { |
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final double[] array; |
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final DoubleBinaryOperator function; |
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DoubleCumulateTask left, right; |
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double in, out; |
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final int lo, hi, origin, fence, threshold; |
| 356 |
|
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DoubleCumulateTask(DoubleCumulateTask parent, DoubleBinaryOperator function, |
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double[] 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; |
| 362 |
this.origin = origin; this.fence = fence; |
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this.threshold = threshold; |
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this.lo = lo; this.hi = hi; |
| 365 |
} |
| 366 |
|
| 367 |
public final void compute() { |
| 368 |
final DoubleBinaryOperator fn; |
| 369 |
final double[] a; |
| 370 |
if ((fn = this.function) == null || (a = this.array) == null) |
| 371 |
throw new NullPointerException(); // hoist checks |
| 372 |
int th = threshold, org = origin, fnc = fence, l, h; |
| 373 |
DoubleCumulateTask t = this; |
| 374 |
outer: while ((l = t.lo) >= 0 && (h = t.hi) <= a.length) { |
| 375 |
if (h - l > th) { |
| 376 |
DoubleCumulateTask lt = t.left, rt = t.right, f; |
| 377 |
if (lt == null) { // first pass |
| 378 |
int mid = (l + h) >>> 1; |
| 379 |
f = rt = t.right = |
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new DoubleCumulateTask(t, fn, a, org, fnc, th, mid, h); |
| 381 |
t = lt = t.left = |
| 382 |
new DoubleCumulateTask(t, fn, a, org, fnc, th, l, mid); |
| 383 |
} |
| 384 |
else { // possibly refork |
| 385 |
double pin = t.in; |
| 386 |
lt.in = pin; |
| 387 |
f = t = null; |
| 388 |
if (rt != null) { |
| 389 |
double lout = lt.out; |
| 390 |
rt.in = (l == org ? lout : |
| 391 |
fn.applyAsDouble(pin, lout)); |
| 392 |
for (int c;;) { |
| 393 |
if (((c = rt.getPendingCount()) & CUMULATE) != 0) |
| 394 |
break; |
| 395 |
if (rt.compareAndSetPendingCount(c, c|CUMULATE)){ |
| 396 |
t = rt; |
| 397 |
break; |
| 398 |
} |
| 399 |
} |
| 400 |
} |
| 401 |
for (int c;;) { |
| 402 |
if (((c = lt.getPendingCount()) & CUMULATE) != 0) |
| 403 |
break; |
| 404 |
if (lt.compareAndSetPendingCount(c, c|CUMULATE)) { |
| 405 |
if (t != null) |
| 406 |
f = t; |
| 407 |
t = lt; |
| 408 |
break; |
| 409 |
} |
| 410 |
} |
| 411 |
if (t == null) |
| 412 |
break; |
| 413 |
} |
| 414 |
if (f != null) |
| 415 |
f.fork(); |
| 416 |
} |
| 417 |
else { |
| 418 |
int state; // Transition to sum, cumulate, or both |
| 419 |
for (int b;;) { |
| 420 |
if (((b = t.getPendingCount()) & FINISHED) != 0) |
| 421 |
break outer; // already done |
| 422 |
state = ((b & CUMULATE) != 0 ? FINISHED : |
| 423 |
(l > org) ? SUMMED : (SUMMED|FINISHED)); |
| 424 |
if (t.compareAndSetPendingCount(b, b|state)) |
| 425 |
break; |
| 426 |
} |
| 427 |
|
| 428 |
double sum; |
| 429 |
if (state != SUMMED) { |
| 430 |
int first; |
| 431 |
if (l == org) { // leftmost; no in |
| 432 |
sum = a[org]; |
| 433 |
first = org + 1; |
| 434 |
} |
| 435 |
else { |
| 436 |
sum = t.in; |
| 437 |
first = l; |
| 438 |
} |
| 439 |
for (int i = first; i < h; ++i) // cumulate |
| 440 |
a[i] = sum = fn.applyAsDouble(sum, a[i]); |
| 441 |
} |
| 442 |
else if (h < fnc) { // skip rightmost |
| 443 |
sum = a[l]; |
| 444 |
for (int i = l + 1; i < h; ++i) // sum only |
| 445 |
sum = fn.applyAsDouble(sum, a[i]); |
| 446 |
} |
| 447 |
else |
| 448 |
sum = t.in; |
| 449 |
t.out = sum; |
| 450 |
for (DoubleCumulateTask par;;) { // propagate |
| 451 |
if ((par = (DoubleCumulateTask)t.getCompleter()) == null) { |
| 452 |
if ((state & FINISHED) != 0) // enable join |
| 453 |
t.quietlyComplete(); |
| 454 |
break outer; |
| 455 |
} |
| 456 |
int b = par.getPendingCount(); |
| 457 |
if ((b & state & FINISHED) != 0) |
| 458 |
t = par; // both done |
| 459 |
else if ((b & state & SUMMED) != 0) { // both summed |
| 460 |
int nextState; DoubleCumulateTask lt, rt; |
| 461 |
if ((lt = par.left) != null && |
| 462 |
(rt = par.right) != null) { |
| 463 |
double lout = lt.out; |
| 464 |
par.out = (rt.hi == fnc ? lout : |
| 465 |
fn.applyAsDouble(lout, rt.out)); |
| 466 |
} |
| 467 |
int refork = (((b & CUMULATE) == 0 && |
| 468 |
par.lo == org) ? CUMULATE : 0); |
| 469 |
if ((nextState = b|state|refork) == b || |
| 470 |
par.compareAndSetPendingCount(b, nextState)) { |
| 471 |
state = SUMMED; // drop finished |
| 472 |
t = par; |
| 473 |
if (refork != 0) |
| 474 |
par.fork(); |
| 475 |
} |
| 476 |
} |
| 477 |
else if (par.compareAndSetPendingCount(b, b|state)) |
| 478 |
break outer; // sib not ready |
| 479 |
} |
| 480 |
} |
| 481 |
} |
| 482 |
} |
| 483 |
private static final long serialVersionUID = -586947823794232033L; |
| 484 |
} |
| 485 |
|
| 486 |
static final class IntCumulateTask extends CountedCompleter<Void> { |
| 487 |
final int[] array; |
| 488 |
final IntBinaryOperator function; |
| 489 |
IntCumulateTask left, right; |
| 490 |
int in, out; |
| 491 |
final int lo, hi, origin, fence, threshold; |
| 492 |
|
| 493 |
IntCumulateTask(IntCumulateTask parent, IntBinaryOperator function, |
| 494 |
int[] array, int origin, int fence, int threshold, |
| 495 |
int lo, int hi) { |
| 496 |
super(parent); |
| 497 |
this.function = function; this.array = array; |
| 498 |
this.origin = origin; this.fence = fence; |
| 499 |
this.threshold = threshold; |
| 500 |
this.lo = lo; this.hi = hi; |
| 501 |
} |
| 502 |
|
| 503 |
public final void compute() { |
| 504 |
final IntBinaryOperator fn; |
| 505 |
final int[] a; |
| 506 |
if ((fn = this.function) == null || (a = this.array) == null) |
| 507 |
throw new NullPointerException(); // hoist checks |
| 508 |
int th = threshold, org = origin, fnc = fence, l, h; |
| 509 |
IntCumulateTask t = this; |
| 510 |
outer: while ((l = t.lo) >= 0 && (h = t.hi) <= a.length) { |
| 511 |
if (h - l > th) { |
| 512 |
IntCumulateTask lt = t.left, rt = t.right, f; |
| 513 |
if (lt == null) { // first pass |
| 514 |
int mid = (l + h) >>> 1; |
| 515 |
f = rt = t.right = |
| 516 |
new IntCumulateTask(t, fn, a, org, fnc, th, mid, h); |
| 517 |
t = lt = t.left = |
| 518 |
new IntCumulateTask(t, fn, a, org, fnc, th, l, mid); |
| 519 |
} |
| 520 |
else { // possibly refork |
| 521 |
int pin = t.in; |
| 522 |
lt.in = pin; |
| 523 |
f = t = null; |
| 524 |
if (rt != null) { |
| 525 |
int lout = lt.out; |
| 526 |
rt.in = (l == org ? lout : |
| 527 |
fn.applyAsInt(pin, lout)); |
| 528 |
for (int c;;) { |
| 529 |
if (((c = rt.getPendingCount()) & CUMULATE) != 0) |
| 530 |
break; |
| 531 |
if (rt.compareAndSetPendingCount(c, c|CUMULATE)){ |
| 532 |
t = rt; |
| 533 |
break; |
| 534 |
} |
| 535 |
} |
| 536 |
} |
| 537 |
for (int c;;) { |
| 538 |
if (((c = lt.getPendingCount()) & CUMULATE) != 0) |
| 539 |
break; |
| 540 |
if (lt.compareAndSetPendingCount(c, c|CUMULATE)) { |
| 541 |
if (t != null) |
| 542 |
f = t; |
| 543 |
t = lt; |
| 544 |
break; |
| 545 |
} |
| 546 |
} |
| 547 |
if (t == null) |
| 548 |
break; |
| 549 |
} |
| 550 |
if (f != null) |
| 551 |
f.fork(); |
| 552 |
} |
| 553 |
else { |
| 554 |
int state; // Transition to sum, cumulate, or both |
| 555 |
for (int b;;) { |
| 556 |
if (((b = t.getPendingCount()) & FINISHED) != 0) |
| 557 |
break outer; // already done |
| 558 |
state = ((b & CUMULATE) != 0 ? FINISHED : |
| 559 |
(l > org) ? SUMMED : (SUMMED|FINISHED)); |
| 560 |
if (t.compareAndSetPendingCount(b, b|state)) |
| 561 |
break; |
| 562 |
} |
| 563 |
|
| 564 |
int sum; |
| 565 |
if (state != SUMMED) { |
| 566 |
int first; |
| 567 |
if (l == org) { // leftmost; no in |
| 568 |
sum = a[org]; |
| 569 |
first = org + 1; |
| 570 |
} |
| 571 |
else { |
| 572 |
sum = t.in; |
| 573 |
first = l; |
| 574 |
} |
| 575 |
for (int i = first; i < h; ++i) // cumulate |
| 576 |
a[i] = sum = fn.applyAsInt(sum, a[i]); |
| 577 |
} |
| 578 |
else if (h < fnc) { // skip rightmost |
| 579 |
sum = a[l]; |
| 580 |
for (int i = l + 1; i < h; ++i) // sum only |
| 581 |
sum = fn.applyAsInt(sum, a[i]); |
| 582 |
} |
| 583 |
else |
| 584 |
sum = t.in; |
| 585 |
t.out = sum; |
| 586 |
for (IntCumulateTask par;;) { // propagate |
| 587 |
if ((par = (IntCumulateTask)t.getCompleter()) == null) { |
| 588 |
if ((state & FINISHED) != 0) // enable join |
| 589 |
t.quietlyComplete(); |
| 590 |
break outer; |
| 591 |
} |
| 592 |
int b = par.getPendingCount(); |
| 593 |
if ((b & state & FINISHED) != 0) |
| 594 |
t = par; // both done |
| 595 |
else if ((b & state & SUMMED) != 0) { // both summed |
| 596 |
int nextState; IntCumulateTask lt, rt; |
| 597 |
if ((lt = par.left) != null && |
| 598 |
(rt = par.right) != null) { |
| 599 |
int lout = lt.out; |
| 600 |
par.out = (rt.hi == fnc ? lout : |
| 601 |
fn.applyAsInt(lout, rt.out)); |
| 602 |
} |
| 603 |
int refork = (((b & CUMULATE) == 0 && |
| 604 |
par.lo == org) ? CUMULATE : 0); |
| 605 |
if ((nextState = b|state|refork) == b || |
| 606 |
par.compareAndSetPendingCount(b, nextState)) { |
| 607 |
state = SUMMED; // drop finished |
| 608 |
t = par; |
| 609 |
if (refork != 0) |
| 610 |
par.fork(); |
| 611 |
} |
| 612 |
} |
| 613 |
else if (par.compareAndSetPendingCount(b, b|state)) |
| 614 |
break outer; // sib not ready |
| 615 |
} |
| 616 |
} |
| 617 |
} |
| 618 |
} |
| 619 |
private static final long serialVersionUID = 3731755594596840961L; |
| 620 |
} |
| 621 |
|
| 622 |
} |
