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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 jsr166y.forkjoin.*; |
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import static jsr166y.forkjoin.Ops.*; |
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import java.util.*; |
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import java.util.concurrent.*; |
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|
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public class LongCumulateDemo { |
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static final int NCPU = Runtime.getRuntime().availableProcessors(); |
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/** for time conversion */ |
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static final long NPS = (1000L * 1000 * 1000); |
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|
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static final boolean reportSteals = false; |
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|
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public static void main(String[] args) throws Exception { |
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int n = 1 << 19; |
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int reps = 1 << 9; |
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int tests = 4; |
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long[] array = new long[n]; |
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long last, now; |
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double elapsed; |
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|
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for (int j = 0; j < tests; ++j) { |
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seqFill(array); |
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last = System.nanoTime(); |
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for (int k = 0; k < reps; ++k) { |
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seqCumulate(array); |
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if (j == 0 && k == 0) |
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check(array); |
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} |
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now = System.nanoTime(); |
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elapsed = (double)(now - last) / (NPS); |
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System.out.printf("seq : %9.5f\n", elapsed); |
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} |
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|
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ForkJoinPool fjp = new ForkJoinPool(2); |
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for (int sweeps = 0; sweeps < 2; ++sweeps) { |
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for (int i = 2; i <= NCPU; i <<= 1) { |
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fjp.setPoolSize(i); |
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oneRun(fjp, array, i, reps, tests); |
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} |
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for (int i = NCPU; i >= 1; i >>>= 1) { |
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fjp.setPoolSize(i); |
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oneRun(fjp, array, i, reps, tests); |
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} |
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} |
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fjp.shutdown(); |
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} |
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|
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static void oneRun(ForkJoinPool fjp, |
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long[] array, int nthreads, |
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int reps, int tests) throws Exception { |
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ParallelLongArray pa = ParallelLongArray.createUsingHandoff(array, fjp); |
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long last, now; |
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long steals = fjp.getStealCount(); |
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// long syncs = fjp.getSyncCount(); |
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for (int j = 0; j < tests; ++j) { |
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pa.replaceWithValue(1); |
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last = System.nanoTime(); |
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for (int k = 0; k < reps; ++k) { |
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pa.cumulateSum(); |
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if (j == 0 && k == 0) |
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check(array); |
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} |
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now = System.nanoTime(); |
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double elapsed = (double)(now - last) / (NPS); |
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last = now; |
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System.out.printf("ps %2d: %9.5f", nthreads, elapsed); |
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if (reportSteals) { |
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long sc = fjp.getStealCount(); |
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long scount = (sc - steals) / reps; |
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steals = sc; |
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System.out.printf(" Steals:%6d", scount); |
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} |
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System.out.println(); |
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} |
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Thread.sleep(100); |
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} |
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|
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static void check(long[] array) { |
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for (int i = 0; i < array.length; ++i) { |
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long sum = i + 1; |
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if (array[i] != sum) { |
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System.out.println("i: " + i + " sum: " + sum + " element:" + array[i]); |
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throw new Error(); |
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} |
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} |
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} |
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|
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static void seqFill(long[] array) { |
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for (int i = 0; i < array.length; ++i) |
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array[i] = 1; |
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} |
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|
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static long seqCumulate(long[] array) { |
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long sum = 0; |
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for (int i = 0; i < array.length; ++i) |
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sum = array[i] += sum; |
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return sum; |
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} |
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} |
