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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 static extra166y.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 LongMapReduceDemo { |
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static final int NCPU = Runtime.getRuntime().availableProcessors(); |
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static final Random rng = new Random(); |
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|
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/** |
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* Sequential version, for performance comparison |
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*/ |
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static long seqMapReduce(long[] array, |
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LongOp mapper, |
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LongReducer reducer, |
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long base) { |
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long n = array.length; |
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long x = base; |
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for (int i = 0; i < n; ++i) |
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x = reducer.op(x, mapper.op(array[i])); |
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return x; |
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} |
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|
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// sample functions |
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static final class GetNext implements LongOp { |
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public long op(long seed) { |
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long x = seed; |
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x ^= x << 13; |
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x ^= x >>> 7; |
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x ^= (x << 17); |
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x ^= x << 13; |
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x ^= x >>> 7; |
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x ^= (x << 17); |
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x ^= x << 13; |
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x ^= x >>> 7; |
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x ^= (x << 17); |
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x ^= x << 13; |
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x ^= x >>> 7; |
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x ^= (x << 17); |
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return x; |
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} |
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} |
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|
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static final class Accum implements LongReducer { |
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public long op(long x, long y) { |
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return x + y; |
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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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int n = 1 << 18; |
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int reps = 1 << 10; |
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long[] array = new long[n]; |
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for (int i = 0; i < n; ++i) |
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array[i] = i + 1L; |
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ForkJoinPool fjp = new ForkJoinPool(); |
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ParallelLongArray pa = ParallelLongArray.createUsingHandoff(array, fjp); |
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final GetNext getNext = new GetNext(); |
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final Accum accum = new Accum(); |
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final long zero = 0L; |
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long last, now; |
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double elapsed; |
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for (int j = 0; j < 2; ++j) { |
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long rseed = rng.nextLong(); |
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resetSeeds(array, rseed); |
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long seqsum = 0; |
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last = System.nanoTime(); |
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for (int k = 0; k < reps; ++k) { |
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seqsum += seqMapReduce(array, getNext, accum, zero); |
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long tmp = array[k]; |
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array[k] = array[n - k - 1]; |
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array[n - k - 1] = tmp; |
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} |
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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("sequential: %7.3f\n", elapsed); |
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for (int i = NCPU; i >= 1; i >>>= 1) { |
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resetSeeds(array, rseed); |
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long sum = 0; |
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last = System.nanoTime(); |
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for (int k = 0; k < reps; ++k) { |
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sum += pa.withMapping(getNext).reduce(accum, zero); |
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long tmp = array[k]; |
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array[k] = array[n - k - 1]; |
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array[n - k - 1] = tmp; |
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} |
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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("poolSize %3d: %7.3f\n", fjp.getParallelism(), elapsed); |
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if (sum != seqsum) throw new Error("checksum"); |
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} |
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for (int i = 2; i <= NCPU; i <<= 1) { |
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resetSeeds(array, rseed); |
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long sum = 0; |
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// fjp.setParallelism(i); |
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last = System.nanoTime(); |
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for (int k = 0; k < reps; ++k) { |
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sum += pa.withMapping(getNext).reduce(accum, zero); |
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long tmp = array[k]; |
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array[k] = array[n - k - 1]; |
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array[n - k - 1] = tmp; |
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} |
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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("poolSize %3d: %7.3f\n", fjp.getParallelism(), elapsed); |
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if (sum != seqsum) throw new Error("checksum"); |
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} |
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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(100); |
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} |
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|
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static void resetSeeds(long[] array, long s) { |
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for (int i = 0; i < array.length; ++i) |
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array[i] = s++; |
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} |
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|
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} |
