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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 jsr166y.*; |
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import extra166y.*; |
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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 ApplyDemo { |
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static final int NCPU = Runtime.getRuntime().availableProcessors(); |
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/** |
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* Sequential version, for performance comparison |
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*/ |
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static <T> void seqApply(T[] array, Ops.Procedure<T> f) { |
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int n = array.length; |
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for (int i = 0; i < n; ++i) |
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f.op(array[i]); |
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} |
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|
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/** |
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* A sample procedure to apply |
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*/ |
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static final class Proc implements Ops.Procedure<Rand> { |
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public void op(Rand x) { |
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for (int k = 0; k < (1 << 10); ++k) |
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x.next(); |
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} |
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} |
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|
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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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public static void main(String[] args) throws Exception { |
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test(); |
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test(); |
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} |
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|
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public static void test() throws Exception { |
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int n = 1 << 18; |
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Rand[] array = new Rand[n]; |
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for (int i = 0; i < n; ++i) |
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array[i] = new Rand(i); |
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final Proc proc = new Proc(); |
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long last, now; |
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double elapsed; |
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last = System.nanoTime(); |
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for (int k = 0; k < 2; ++k) { |
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for (int j = 0; j < (1 << 3); ++j) |
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seqApply(array, proc); |
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now = System.nanoTime(); |
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elapsed = (double)(now - last) / NPS; |
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last = now; |
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System.out.printf("seq: %7.3f\n", elapsed); |
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} |
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for (int i = 1; i <= NCPU; i <<= 1) { |
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ForkJoinPool fjp = new ForkJoinPool(i); |
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ParallelArray pa = ParallelArray.createUsingHandoff(array, fjp); |
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last = System.nanoTime(); |
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for (int k = 0; k < 2; ++k) { |
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for (int j = 0; j < (1 << 3); ++j) |
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pa.apply(proc); |
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now = System.nanoTime(); |
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elapsed = (double)(now - last) / NPS; |
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last = now; |
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System.out.printf("ps %2d: %7.3f\n", fjp.getParallelism(), elapsed); |
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} |
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fjp.shutdownNow(); |
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fjp.awaitTermination(1, TimeUnit.SECONDS); |
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Thread.sleep(10); |
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} |
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int sum = 0; |
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for (int i = 0; i < array.length; ++i) sum += array[i].seed; |
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if (sum == 0) |
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System.out.print(" "); |
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} |
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|
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/** |
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* Unsynchronized version of java.util.Random algorithm. |
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*/ |
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static final class Rand { |
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static final long multiplier = 0x5DEECE66DL; |
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static final long addend = 0xBL; |
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static final long mask = (1L << 48) - 1; |
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long seed; |
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|
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Rand(long s) { |
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seed = s; |
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} |
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public int next() { |
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long nextseed = (seed * multiplier + addend) & mask; |
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seed = nextseed; |
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return ((int)(nextseed >>> 17)) & 0x7FFFFFFF; |
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} |
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} |
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|
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} |
