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dl |
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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/licenses/publicdomain |
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*/ |
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import java.util.*; |
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import java.util.concurrent.*; |
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// Based very loosely on cilksort |
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class ScalarLongSort { |
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static final long NPS = (1000L * 1000 * 1000); // time conversion |
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static int THRESHOLD; |
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static final boolean warmup = true; |
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jsr166 |
1.3 |
public static void main(String[] args) throws Exception { |
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dl |
1.1 |
int n = 1 << 22; |
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int sreps = 2; |
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int reps = 20; |
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long[] a = new long[n]; |
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if (warmup) { |
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System.out.printf("Sorting %d longs, %d replications\n", n, 1); |
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seqRandomFill(a, 0, n); |
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long last = System.nanoTime(); |
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java.util.Arrays.sort(a); |
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double elapsed = (double)(System.nanoTime() - last) / NPS; |
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System.out.printf("Arrays.sort time: %7.3f\n", elapsed); |
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checkSorted(a); |
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} |
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ForkJoinPool pool = new ForkJoinPool(); |
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// for now hardwire 8 * #CPUs leaf tasks |
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THRESHOLD = 1 + ((n + 7) >>> 3) / pool.getParallelism(); |
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// THRESHOLD = 1 + ((n + 15) >>> 4) / pool.getParallelism(); |
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// THRESHOLD = 1 + ((n + 31) >>> 5) / pool.getParallelism(); |
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System.out.printf("Sorting %d longs, %d replications\n", n, reps); |
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for (int i = 0; i < reps; ++i) { |
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pool.invoke(new RandomFiller(a, 0, n)); |
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long last = System.nanoTime(); |
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pool.invoke(new Sorter(a, new long[n], 0, n)); |
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double elapsed = (double)(System.nanoTime() - last) / NPS; |
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System.out.printf("Parallel sort time: %7.3f\n", elapsed); |
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if (i == 0) |
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checkSorted(a); |
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} |
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System.out.println(pool); |
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System.out.printf("Sorting %d longs, %d replications\n", n, sreps); |
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for (int i = 0; i < sreps; ++i) { |
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pool.invoke(new RandomFiller(a, 0, n)); |
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long last = System.nanoTime(); |
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java.util.Arrays.sort(a); |
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double elapsed = (double)(System.nanoTime() - last) / NPS; |
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System.out.printf("Arrays.sort time: %7.3f\n", elapsed); |
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if (i == 0) |
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checkSorted(a); |
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} |
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System.out.println(pool); |
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pool.shutdown(); |
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} |
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static final class Sorter extends RecursiveAction { |
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jsr166 |
1.2 |
final long[] a; |
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dl |
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final long[] w; |
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jsr166 |
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final int origin; |
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final int n; |
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Sorter(long[] a, long[] w, int origin, int n) { |
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this.a = a; this.w = w; this.origin = origin; this.n = n; |
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} |
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public void compute() { |
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int l = origin; |
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if (n <= THRESHOLD) |
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Arrays.sort(a, l, l+n); |
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else { // divide in quarters to ensure sorted array in a not w |
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SubSorter rs; |
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int h = n >>> 1; |
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int q = n >>> 2; |
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int u = h + q; |
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(rs = new SubSorter |
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(new Sorter(a, w, l+h, q), |
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new Sorter(a, w, l+u, n-u), |
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new Merger(a, w, l+h, q, l+u, n-u, l+h, null))).fork(); |
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(new SubSorter |
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(new Sorter(a, w, l, q), |
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new Sorter(a, w, l+q, h-q), |
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new Merger(a, w, l, q, l+q, h-q, l, null))).compute(); |
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rs.join(); |
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new Merger(w, a, l, h, l+h, n-h, l, null).compute(); |
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} |
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} |
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} |
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jsr166 |
1.2 |
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dl |
1.1 |
static final class SubSorter extends RecursiveAction { |
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final Sorter left; |
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final Sorter right; |
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final Merger merger; |
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SubSorter(Sorter left, Sorter right, Merger merger) { |
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this.left = left; this.right = right; this.merger = merger; |
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} |
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public void compute() { |
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right.fork(); |
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left.compute(); |
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right.join(); |
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merger.compute(); |
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} |
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} |
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static final class Merger extends RecursiveAction { |
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final long[] a; final long[] w; |
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final int lo; final int ln; final int ro; final int rn; final int wo; |
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final Merger next; |
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Merger(long[] a, long[] w, int lo, int ln, int ro, int rn, int wo, |
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Merger next) { |
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this.a = a; this.w = w; |
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this.lo = lo; this.ln = ln; |
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this.ro = ro; this.rn = rn; |
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this.wo = wo; |
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this.next = next; |
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} |
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/** |
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* Merge left and right by splitting left in half, |
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* and finding index of right closest to split point. |
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* Uses left-spine decomposition to generate all |
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* merge tasks before bottomming out at base case. |
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jsr166 |
1.2 |
* |
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dl |
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*/ |
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public void compute() { |
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Merger rights = null; |
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int nleft = ln; |
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int nright = rn; |
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while (nleft > THRESHOLD) { // && nright > (THRESHOLD >>> 3)) { |
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int lh = nleft >>> 1; |
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int splitIndex = lo + lh; |
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long split = a[splitIndex]; |
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int rl = 0; |
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int rh = nright; |
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while (rl < rh) { |
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int mid = (rl + rh) >>> 1; |
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if (split <= a[ro + mid]) |
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rh = mid; |
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else |
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rl = mid + 1; |
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} |
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(rights = new Merger(a, w, splitIndex, nleft-lh, ro+rh, |
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nright-rh, wo+lh+rh, rights)).fork(); |
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nleft = lh; |
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nright = rh; |
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} |
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// Base case -- merge left and right |
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int l = lo; |
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int lFence = lo + nleft; |
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int r = ro; |
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int rFence = ro + nright; |
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int k = wo; |
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while (l < lFence && r < rFence) { |
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long al = a[l]; |
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long ar = a[r]; |
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long t; |
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if (al <= ar) { ++l; t = al; } else { ++r; t = ar; } |
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w[k++] = t; |
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} |
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while (l < lFence) |
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w[k++] = a[l++]; |
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while (r < rFence) |
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w[k++] = a[r++]; |
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jsr166 |
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dl |
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while (rights != null) { |
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rights.join(); |
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rights = rights.next; |
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} |
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} |
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} |
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jsr166 |
1.3 |
static void checkSorted(long[] a) { |
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dl |
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int n = a.length; |
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for (int i = 0; i < n - 1; i++) { |
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if (a[i] > a[i+1]) { |
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jsr166 |
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throw new Error("Unsorted at " + i + ": " + |
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a[i] + " / " + a[i+1]); |
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} |
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} |
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} |
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static void seqRandomFill(long[] array, int lo, int hi) { |
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ThreadLocalRandom rng = ThreadLocalRandom.current(); |
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for (int i = lo; i < hi; ++i) |
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array[i] = rng.nextLong(); |
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} |
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static final class RandomFiller extends RecursiveAction { |
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final long[] array; |
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final int lo, hi; |
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RandomFiller(long[] array, int lo, int hi) { |
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this.array = array; this.lo = lo; this.hi = hi; |
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} |
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public void compute() { |
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if (hi - lo <= THRESHOLD) |
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seqRandomFill(array, lo, hi); |
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else { |
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int mid = (lo + hi) >>> 1; |
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RandomFiller r = new RandomFiller(array, mid, hi); |
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r.fork(); |
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(new RandomFiller(array, lo, mid)).compute(); |
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r.join(); |
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} |
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} |
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} |
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} |