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/** |
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* Adapted from FJTask version. |
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* Sample program using Guassian Quadrature for numerical integration. |
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* Inspired by a |
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* Inspired by a |
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* <A href="http://www.cs.uga.edu/~dkl/filaments/dist.html"> Filaments</A> |
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* demo program. |
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* |
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* |
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*/ |
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|
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public class IntegrateGamma { |
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start = new Double(args[1]).doubleValue(); |
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if (args.length > 2) |
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end = new Double(args[2]).doubleValue(); |
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< |
if (args.length > 3) |
33 |
> |
if (args.length > 3) |
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exp = Integer.parseInt(args[3]); |
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} |
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catch (Exception e) { |
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return; |
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} |
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|
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< |
ForkJoinPool g = procs == 0? new ForkJoinPool() : |
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> |
ForkJoinPool g = procs == 0? new ForkJoinPool() : |
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new ForkJoinPool(procs); |
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|
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System.out.println("Integrating from " + start + " to " + end + " exponent: " + exp + " parallelism " + g.getParallelism()); |
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|
45 |
> |
|
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Function f = new SampleFunction(exp); |
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for (int i = 0; i < 10; ++i) { |
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Integrator integrator = new Integrator(f, 0.001, g); |
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double elapsed = elapsedTime(last); |
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System.out.printf("time: %7.3f", elapsed); |
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System.out.println(" Answer = " + result); |
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< |
} |
54 |
> |
} |
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System.out.println(g); |
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g.shutdown(); |
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} |
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return q.area; |
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} |
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|
119 |
< |
|
120 |
< |
/** |
119 |
> |
|
120 |
> |
/** |
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* FJTask to recursively perform the quadrature. |
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* Algorithm: |
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* Compute the area from lower bound to the center point of interval, |
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final double right; // upper bound |
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final double f_left; // value of the function evaluated at left |
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final double f_right; // value of the function evaluated at right |
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|
133 |
> |
|
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// Area initialized with original estimate from left to right. |
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// It is replaced with refined value. |
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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 |
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double area) { |
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this.left = left; |
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this.right = right; |
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this.f_right = f_right; |
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this.area = area; |
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} |
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|
147 |
> |
|
148 |
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public void compute() { |
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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); |
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double rightArea = 0.5 * (right - center) * (f_center + f_right); |
154 |
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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 |
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Quad q2 = new Quad(center, right, f_center, f_right, rightArea); |
163 |
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q2.compute(); |
164 |
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q1.join(); |
165 |
< |
sum = q1.area + q2.area; |
165 |
> |
sum = q1.area + q2.area; |
166 |
|
} |
167 |
< |
|
167 |
> |
|
168 |
|
area = sum; |
169 |
|
} |
170 |
|
} |
172 |
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|
173 |
|
} |
174 |
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|
175 |
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|
175 |
> |
|