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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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import java.util.*; |
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import java.util.concurrent.*; |
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|
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public final class LeftSpineFib extends RecursiveAction { |
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|
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// Performance-tuning constant: |
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static int sequentialThreshold; |
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static long lastStealCount; |
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|
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public static void main(String[] args) throws Exception { |
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int procs = 0; |
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int num = 45; |
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sequentialThreshold = 2; |
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try { |
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if (args.length > 0) |
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procs = Integer.parseInt(args[0]); |
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if (args.length > 1) |
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num = Integer.parseInt(args[1]); |
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if (args.length > 2) |
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sequentialThreshold = Integer.parseInt(args[2]); |
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} |
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catch (Exception e) { |
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System.out.println("Usage: java LeftSpineFib <threads> <number> [<sequntialThreshold>]"); |
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return; |
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} |
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|
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for (int reps = 0; reps < 2; ++reps) { |
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ForkJoinPool g = (procs == 0) ? ForkJoinPool.commonPool() : |
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new ForkJoinPool(procs); |
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lastStealCount = g.getStealCount(); |
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for (int i = 0; i < 20; ++i) { |
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test(g, num); |
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Thread.sleep(100); |
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} |
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System.out.println(g); |
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if (g != ForkJoinPool.commonPool()) |
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g.shutdown(); |
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Thread.sleep(500); |
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} |
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} |
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|
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static void test(ForkJoinPool g, int num) throws Exception { |
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int ps = g.getParallelism(); |
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long start = System.currentTimeMillis(); |
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LeftSpineFib f = new LeftSpineFib(num, null); |
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g.invoke(f); |
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long time = System.currentTimeMillis() - start; |
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double secs = ((double)time) / 1000.0; |
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long result = f.getAnswer(); |
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System.out.print("JLSFib " + num + " = " + result); |
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System.out.printf("\tTime: %7.3f", secs); |
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long sc = g.getStealCount(); |
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long ns = sc - lastStealCount; |
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lastStealCount = sc; |
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System.out.printf(" Steals/t: %5d", ns/ps); |
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// System.out.printf(" Workers: %8d", g.getRunningThreadCount()); |
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System.out.printf(" Workers: %8d", g.getPoolSize()); |
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System.out.println(); |
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} |
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|
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// Initialized with argument; replaced with result |
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int number; |
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LeftSpineFib next; |
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|
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LeftSpineFib(int n, LeftSpineFib nxt) { number = n; next = nxt; } |
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|
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int getAnswer() { |
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return number; |
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} |
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|
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public final void compute() { |
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int n = number; |
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if (n > 1) { |
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LeftSpineFib rt = null; |
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int r = 0; |
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while (n > sequentialThreshold) { |
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int m = n - 2; |
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if (m <= 1) |
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r += m; |
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else |
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(rt = new LeftSpineFib(m, rt)).fork(); |
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n -= 1; |
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} |
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r += n <= 1 ? n : seqFib(n); |
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if (rt != null) |
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r += collectRights(rt); |
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number = r; |
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} |
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} |
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|
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static final int collectRights(LeftSpineFib rt) { |
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int r = 0; |
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while (rt != null) { |
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LeftSpineFib rn = rt.next; |
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rt.next = null; |
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if (rt.tryUnfork()) rt.compute(); else rt.join(); |
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// rt.join(); |
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r += rt.number; |
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rt = rn; |
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} |
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return r; |
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} |
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|
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// Sequential version for arguments less than threshold |
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static final int seqFib(int n) { // unroll left only |
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int r = 1; |
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do { |
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int m = n - 2; |
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r += m <= 1 ? m : seqFib(m); |
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} while (--n > 1); |
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return r; |
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} |
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|
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} |
