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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 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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public class FilterDemo { |
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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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jsr166 |
1.2 |
static<T> List<T> seqFilter(T[] list, |
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dl |
1.1 |
Ops.Predicate<T> pred) { |
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ArrayList<T> result = new ArrayList<T>(); |
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int n = list.length; |
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for (int i = 0; i < n; ++i) { |
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T x = list[i]; |
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if (pred.op(x)) |
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result.add(x); |
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} |
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return result; |
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} |
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/** |
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* Slow/dumb prime check |
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*/ |
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static final class IsPrime implements Ops.Predicate<Rand> { |
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public boolean op(Rand r) { |
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long n = r.seed; |
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if ((n & 1) == 0) |
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return false; |
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int bound = (int)(Math.sqrt(n)); |
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for (int i = 3; i <= bound; i += 2) |
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if (n % i == 0) |
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return false; |
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return true; |
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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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static final class NextRand implements Ops.Procedure<Rand> { |
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public void op(Rand r) { |
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r.next(); |
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} |
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} |
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public static void main(String[] args) throws Exception { |
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int n = 1 << 9; |
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Rand[] array = new Rand[n]; |
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jsr166 |
1.2 |
for (int i = 0; i < n; ++i) |
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dl |
1.1 |
array[i] = new Rand(i); |
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final IsPrime pred = new IsPrime(); |
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final NextRand nextRand = new NextRand(); |
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long last, now; |
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double elapsed; |
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last = System.nanoTime(); |
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List<Rand> seqResult = null; |
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int resultLength = -1; |
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boolean checked = false; |
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for (int k = 0; k < 2; ++k) { |
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List<Rand> result = seqFilter(array, pred); |
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now = System.nanoTime(); |
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if (resultLength < 0) { |
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resultLength = result.size(); |
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seqResult = result; |
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} |
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else if (resultLength != result.size()) |
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throw new Error("wrong result size"); |
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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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jsr166 |
1.2 |
// for (Rand r : array) r.next(); |
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dl |
1.1 |
} |
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int pass = 0; |
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int ps = 2; |
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ForkJoinPool fjp = new ForkJoinPool(ps); |
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ParallelArray<Rand> pa = ParallelArray.createUsingHandoff(array, fjp); |
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for (;;) { |
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last = System.nanoTime(); |
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for (int k = 0; k < 4; ++k) { |
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List<Rand> result = pa.withFilter(pred).all().asList(); |
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now = System.nanoTime(); |
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if (!checked) { |
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checked = true; |
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if (!result.equals(seqResult)) |
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throw new Error("res" + result + " seq" + seqResult); |
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} |
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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", ps, elapsed); |
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} |
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if (pass == 0) { |
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jsr166 |
1.2 |
if (ps >= NCPU) |
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dl |
1.1 |
pass = 1; |
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else |
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ps <<= 1; |
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} |
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else { |
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if (ps == 1) |
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break; |
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else |
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ps >>>= 1; |
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} |
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// pa.apply(nextRand); |
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fjp.setParallelism(ps); |
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} |
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fjp.shutdownNow(); |
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fjp.awaitTermination(1, TimeUnit.SECONDS); |
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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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private final static long multiplier = 0x5DEECE66DL; |
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private final static long addend = 0xBL; |
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private final static long mask = (1L << 48) - 1; |
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private long seed; |
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Rand(long s) { |
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seed = s; |
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next(); |
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next(); |
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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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public String toString() { |
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jsr166 |
1.2 |
return String.valueOf(seed); |
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dl |
1.1 |
} |
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} |
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} |