| 9 |
|
/** |
| 10 |
|
* Adapted from FJTask version. |
| 11 |
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* Sample program using Guassian Quadrature for numerical integration. |
| 12 |
< |
* Inspired by a |
| 12 |
> |
* Inspired by a |
| 13 |
|
* <A href="http://www.cs.uga.edu/~dkl/filaments/dist.html"> Filaments</A> |
| 14 |
|
* demo program. |
| 15 |
< |
* |
| 15 |
> |
* |
| 16 |
|
*/ |
| 17 |
|
|
| 18 |
|
public class IntegrateGamma { |
| 30 |
|
start = new Double(args[1]).doubleValue(); |
| 31 |
|
if (args.length > 2) |
| 32 |
|
end = new Double(args[2]).doubleValue(); |
| 33 |
< |
if (args.length > 3) |
| 33 |
> |
if (args.length > 3) |
| 34 |
|
exp = Integer.parseInt(args[3]); |
| 35 |
|
} |
| 36 |
|
catch (Exception e) { |
| 38 |
|
return; |
| 39 |
|
} |
| 40 |
|
|
| 41 |
< |
ForkJoinPool g = procs == 0? new ForkJoinPool() : |
| 41 |
> |
ForkJoinPool g = procs == 0? new ForkJoinPool() : |
| 42 |
|
new ForkJoinPool(procs); |
| 43 |
|
|
| 44 |
|
System.out.println("Integrating from " + start + " to " + end + " exponent: " + exp + " parallelism " + g.getParallelism()); |
| 45 |
< |
|
| 45 |
> |
|
| 46 |
|
Function f = new SampleFunction(exp); |
| 47 |
|
for (int i = 0; i < 10; ++i) { |
| 48 |
|
Integrator integrator = new Integrator(f, 0.001, g); |
| 51 |
|
double elapsed = elapsedTime(last); |
| 52 |
|
System.out.printf("time: %7.3f", elapsed); |
| 53 |
|
System.out.println(" Answer = " + result); |
| 54 |
< |
} |
| 54 |
> |
} |
| 55 |
|
System.out.println(g); |
| 56 |
|
g.shutdown(); |
| 57 |
|
} |
| 116 |
|
return q.area; |
| 117 |
|
} |
| 118 |
|
|
| 119 |
< |
|
| 120 |
< |
/** |
| 119 |
> |
|
| 120 |
> |
/** |
| 121 |
|
* FJTask to recursively perform the quadrature. |
| 122 |
|
* Algorithm: |
| 123 |
|
* Compute the area from lower bound to the center point of interval, |
| 130 |
|
final double right; // upper bound |
| 131 |
|
final double f_left; // value of the function evaluated at left |
| 132 |
|
final double f_right; // value of the function evaluated at right |
| 133 |
< |
|
| 133 |
> |
|
| 134 |
|
// Area initialized with original estimate from left to right. |
| 135 |
|
// It is replaced with refined value. |
| 136 |
|
volatile double area; |
| 137 |
< |
|
| 138 |
< |
Quad(double left, double right, |
| 139 |
< |
double f_left, double f_right, |
| 137 |
> |
|
| 138 |
> |
Quad(double left, double right, |
| 139 |
> |
double f_left, double f_right, |
| 140 |
|
double area) { |
| 141 |
|
this.left = left; |
| 142 |
|
this.right = right; |
| 144 |
|
this.f_right = f_right; |
| 145 |
|
this.area = area; |
| 146 |
|
} |
| 147 |
< |
|
| 147 |
> |
|
| 148 |
|
public void compute() { |
| 149 |
|
double center = 0.5 * (left + right); |
| 150 |
< |
double f_center = f.compute(center); |
| 151 |
< |
|
| 152 |
< |
double leftArea = 0.5 * (center - left) * (f_left + f_center); |
| 150 |
> |
double f_center = f.compute(center); |
| 151 |
> |
|
| 152 |
> |
double leftArea = 0.5 * (center - left) * (f_left + f_center); |
| 153 |
|
double rightArea = 0.5 * (right - center) * (f_center + f_right); |
| 154 |
|
double sum = leftArea + rightArea; |
| 155 |
< |
|
| 155 |
> |
|
| 156 |
|
double diff = sum - area; |
| 157 |
|
if (diff < 0) diff = -diff; |
| 158 |
< |
|
| 159 |
< |
if (diff >= errorTolerance) { |
| 158 |
> |
|
| 159 |
> |
if (diff >= errorTolerance) { |
| 160 |
|
Quad q1 = new Quad(left, center, f_left, f_center, leftArea); |
| 161 |
|
q1.fork(); |
| 162 |
|
Quad q2 = new Quad(center, right, f_center, f_right, rightArea); |
| 163 |
|
q2.compute(); |
| 164 |
|
q1.join(); |
| 165 |
< |
sum = q1.area + q2.area; |
| 165 |
> |
sum = q1.area + q2.area; |
| 166 |
|
} |
| 167 |
< |
|
| 167 |
> |
|
| 168 |
|
area = sum; |
| 169 |
|
} |
| 170 |
|
} |
| 172 |
|
|
| 173 |
|
} |
| 174 |
|
|
| 175 |
< |
|
| 175 |
> |
|
