| 1 |
/* |
| 2 |
* Written by Doug Lea with assistance from members of JCP JSR-166 |
| 3 |
* Expert Group and released to the public domain, as explained at |
| 4 |
* http://creativecommons.org/publicdomain/zero/1.0/ |
| 5 |
*/ |
| 6 |
|
| 7 |
// A CountedCompleter version of Fibonacci |
| 8 |
|
| 9 |
import java.util.concurrent.*; |
| 10 |
|
| 11 |
public abstract class CCFib extends CountedCompleter { |
| 12 |
static int sequentialThreshold; |
| 13 |
int number; |
| 14 |
int rnumber; |
| 15 |
|
| 16 |
public CCFib(CountedCompleter parent, int n) { |
| 17 |
super(parent, 1); |
| 18 |
this.number = n; |
| 19 |
} |
| 20 |
|
| 21 |
public final void compute() { |
| 22 |
CountedCompleter p; |
| 23 |
CCFib f = this; |
| 24 |
int n = number; |
| 25 |
while (n > sequentialThreshold) { |
| 26 |
new RCCFib(f, n - 2).fork(); |
| 27 |
f = new LCCFib(f, --n); |
| 28 |
} |
| 29 |
f.number = (n <= 1) ? n : seqFib(n); |
| 30 |
f.onCompletion(f); |
| 31 |
if ((p = f.getCompleter()) != null) |
| 32 |
p.tryComplete(); |
| 33 |
else |
| 34 |
f.quietlyComplete(); |
| 35 |
} |
| 36 |
|
| 37 |
static final class LCCFib extends CCFib { |
| 38 |
public LCCFib(CountedCompleter parent, int n) { |
| 39 |
super(parent, n); |
| 40 |
} |
| 41 |
public final void onCompletion(CountedCompleter caller) { |
| 42 |
CCFib p = (CCFib)getCompleter(); |
| 43 |
int n = number + rnumber; |
| 44 |
if (p != null) |
| 45 |
p.number = n; |
| 46 |
else |
| 47 |
number = n; |
| 48 |
} |
| 49 |
} |
| 50 |
|
| 51 |
static final class RCCFib extends CCFib { |
| 52 |
public RCCFib(CountedCompleter parent, int n) { |
| 53 |
super(parent, n); |
| 54 |
} |
| 55 |
public final void onCompletion(CountedCompleter caller) { |
| 56 |
CCFib p = (CCFib)getCompleter(); |
| 57 |
int n = number + rnumber; |
| 58 |
if (p != null) |
| 59 |
p.rnumber = n; |
| 60 |
else |
| 61 |
number = n; |
| 62 |
} |
| 63 |
} |
| 64 |
|
| 65 |
static long lastStealCount; |
| 66 |
|
| 67 |
public static void main(String[] args) throws Exception { |
| 68 |
int num = 45; |
| 69 |
sequentialThreshold = 5; |
| 70 |
try { |
| 71 |
if (args.length > 0) |
| 72 |
num = Integer.parseInt(args[0]); |
| 73 |
if (args.length > 1) |
| 74 |
sequentialThreshold = Integer.parseInt(args[1]); |
| 75 |
} |
| 76 |
catch (Exception e) { |
| 77 |
System.out.println("Usage: java CCFib <number> <threshold>]"); |
| 78 |
return; |
| 79 |
} |
| 80 |
|
| 81 |
ForkJoinPool g = ForkJoinPool.commonPool(); |
| 82 |
for (int reps = 0; reps < 2; ++reps) { |
| 83 |
lastStealCount = g.getStealCount(); |
| 84 |
for (int i = 0; i < 20; ++i) { |
| 85 |
test(g, num); |
| 86 |
} |
| 87 |
System.out.println(g); |
| 88 |
} |
| 89 |
} |
| 90 |
|
| 91 |
/** for time conversion */ |
| 92 |
static final long NPS = (1000L * 1000 * 1000); |
| 93 |
|
| 94 |
static void test(ForkJoinPool g, int num) throws Exception { |
| 95 |
int ps = g.getParallelism(); |
| 96 |
long start = System.nanoTime(); |
| 97 |
CCFib f = new LCCFib(null, num); |
| 98 |
f.invoke(); |
| 99 |
long time = System.nanoTime() - start; |
| 100 |
double secs = ((double)time) / NPS; |
| 101 |
long number = f.number; |
| 102 |
System.out.print("CCFib " + num + " = " + number); |
| 103 |
System.out.printf("\tTime: %9.3f", secs); |
| 104 |
long sc = g.getStealCount(); |
| 105 |
long ns = sc - lastStealCount; |
| 106 |
lastStealCount = sc; |
| 107 |
System.out.printf(" Steals/t: %5d", ns/ps); |
| 108 |
System.out.printf(" Workers: %8d", g.getPoolSize()); |
| 109 |
System.out.println(); |
| 110 |
} |
| 111 |
|
| 112 |
// Sequential version for arguments less than threshold |
| 113 |
static final int seqFib(int n) { // unroll left only |
| 114 |
int r = 1; |
| 115 |
do { |
| 116 |
int m = n - 2; |
| 117 |
r += m <= 1 ? m : seqFib(m); |
| 118 |
} while (--n > 1); |
| 119 |
return r; |
| 120 |
} |
| 121 |
|
| 122 |
} |
