test/loops/IntegrateGamma.java

/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/publicdomain/zero/1.0/
 */

import java.util.concurrent.*;

/**
 * Adapted from FJTask version.
 * Sample program using Guassian Quadrature for numerical integration.
 * Inspired by a
 * <A href="http://www.cs.uga.edu/~dkl/filaments/dist.html"> Filaments</A>
 * demo program.
 */

public class IntegrateGamma {
    /** for time conversion */
    static final long NPS = (1000L * 1000 * 1000);
    public static void main(String[] args) {
        int procs = 0;
        double start = 1.0;
        double end = 96.0;
        int exp = 5;
        try {
            if (args.length > 0)
                procs = Integer.parseInt(args[0]);
            if (args.length > 1)
                start = new Double(args[1]).doubleValue();
            if (args.length > 2)
                end = new Double(args[2]).doubleValue();
            if (args.length > 3)
                exp = Integer.parseInt(args[3]);
        }
        catch (Exception e) {
            System.out.println("Usage: java IntegrateGamma <threads> <lower bound> <upper bound> <exponent>\n (for example 2 1 48 5).");
            return;
        }

        ForkJoinPool g = (procs == 0) ? new ForkJoinPool() :
            new ForkJoinPool(procs);

        System.out.println("Integrating from " + start + " to " + end + " exponent: " + exp + " parallelism " + g.getParallelism());

        Function f = new SampleFunction(exp);
        for (int i = 0; i < 10; ++i) {
            Integrator integrator = new Integrator(f, 0.001, g);
            long last = System.nanoTime();
            double result = integrator.integral(start, end);
            double elapsed = elapsedTime(last);
            System.out.printf("time: %7.3f", elapsed);
            System.out.println(" Answer = " + result);
        }
        System.out.println(g);
        g.shutdown();
    }

    static double elapsedTime(long startTime) {
        return (double)(System.nanoTime() - startTime) / NPS;
    }

    /*
      This is all set up as if it were part of a more serious
      framework, but is for now just a demo, with all
      classes declared as static within Integrate
    */

    /** A function to be integrated */
    static interface Function {
        double compute(double x);
    }

    /**
     * Sample from filaments demo.
     * Computes (2*n-1)*(x^(2*n-1)) for all odd values.
     */
    static class SampleFunction implements Function {
        final int n;
        SampleFunction(int n) { this.n = n; }

        public double compute(double x) {
            double power = x;
            double xsq = x * x;
            double val = power;
            double di = 1.0;
            for (int i = n - 1; i > 0; --i) {
                di += 2.0;
                power *= xsq;
                val += di * power;
            }
            return val;
        }
    }


    static class Integrator {
        final Function f;      // The function to integrate
        final double errorTolerance;
        final ForkJoinPool g;

        Integrator(Function f, double errorTolerance, ForkJoinPool g) {
            this.f = f;
            this.errorTolerance = errorTolerance;
            this.g = g;
        }

        double integral(double lowerBound, double upperBound) {
            double f_lower = f.compute(lowerBound);
            double f_upper = f.compute(upperBound);
            double initialArea = 0.5 * (upperBound-lowerBound) * (f_upper + f_lower);
            Quad q = new Quad(lowerBound, upperBound,
                              f_lower, f_upper,
                              initialArea);
            g.invoke(q);
            return q.area;
        }


        /**
         * FJTask to recursively perform the quadrature.
         * Algorithm:
         *  Compute the area from lower bound to the center point of interval,
         *  and from the center point to the upper bound. If this
         *  differs from the value from lower to upper by more than
         *  the error tolerance, recurse on each half.
         */
        final class Quad extends RecursiveAction {
            final double left;       // lower bound
            final double right;      // upper bound
            final double f_left;     // value of the function evaluated at left
            final double f_right;    // value of the function evaluated at right

            // Area initialized with original estimate from left to right.
            // It is replaced with refined value.
            volatile double area;

            Quad(double left, double right,
                 double f_left, double f_right,
                 double area) {
                this.left = left;
                this.right = right;
                this.f_left = f_left;
                this.f_right = f_right;
                this.area = area;
            }

            public void compute() {
                double center = 0.5 * (left + right);
                double f_center = f.compute(center);

                double leftArea  = 0.5 * (center - left)  * (f_left + f_center);
                double rightArea = 0.5 * (right - center) * (f_center + f_right);
                double sum = leftArea + rightArea;

                double diff = sum - area;
                if (diff < 0) diff = -diff;

                if (diff >= errorTolerance) {
                    Quad q1 = new Quad(left,   center, f_left,   f_center, leftArea);
                    q1.fork();
                    Quad q2 = new Quad(center, right,  f_center, f_right,  rightArea);
                    q2.compute();
                    q1.join();
                    sum = q1.area + q2.area;
                }

                area = sum;
            }
        }
    }

}
Revision:	1.7
Committed:	Sun Oct 21 06:14:12 2012 UTC (11 years, 6 months ago) by jsr166
Branch:	MAIN
Changes since 1.6:	+0 -1 lines
Log Message:	delete trailing empty lines of javadoc
#	Content
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	import java.util.concurrent.*;
8
9	/**
10	* Adapted from FJTask version.
11	* Sample program using Guassian Quadrature for numerical integration.
12	* Inspired by a
13	* <A href="http://www.cs.uga.edu/~dkl/filaments/dist.html"> Filaments</A>
14	* demo program.
15	*/
16
17	public class IntegrateGamma {
18	/** for time conversion */
19	static final long NPS = (1000L * 1000 * 1000);
20	public static void main(String[] args) {
21	int procs = 0;
22	double start = 1.0;
23	double end = 96.0;
24	int exp = 5;
25	try {
26	if (args.length > 0)
27	procs = Integer.parseInt(args[0]);
28	if (args.length > 1)
29	start = new Double(args[1]).doubleValue();
30	if (args.length > 2)
31	end = new Double(args[2]).doubleValue();
32	if (args.length > 3)
33	exp = Integer.parseInt(args[3]);
34	}
35	catch (Exception e) {
36	System.out.println("Usage: java IntegrateGamma <threads> <lower bound> <upper bound> <exponent>\n (for example 2 1 48 5).");
37	return;
38	}
39
40	ForkJoinPool g = (procs == 0) ? new ForkJoinPool() :
41	new ForkJoinPool(procs);
42
43	System.out.println("Integrating from " + start + " to " + end + " exponent: " + exp + " parallelism " + g.getParallelism());
44
45	Function f = new SampleFunction(exp);
46	for (int i = 0; i < 10; ++i) {
47	Integrator integrator = new Integrator(f, 0.001, g);
48	long last = System.nanoTime();
49	double result = integrator.integral(start, end);
50	double elapsed = elapsedTime(last);
51	System.out.printf("time: %7.3f", elapsed);
52	System.out.println(" Answer = " + result);
53	}
54	System.out.println(g);
55	g.shutdown();
56	}
57
58	static double elapsedTime(long startTime) {
59	return (double)(System.nanoTime() - startTime) / NPS;
60	}
61
62	/*
63	This is all set up as if it were part of a more serious
64	framework, but is for now just a demo, with all
65	classes declared as static within Integrate
66	*/
67
68	/** A function to be integrated */
69	static interface Function {
70	double compute(double x);
71	}
72
73	/**
74	* Sample from filaments demo.
75	* Computes (2n-1)(x^(2*n-1)) for all odd values.
76	*/
77	static class SampleFunction implements Function {
78	final int n;
79	SampleFunction(int n) { this.n = n; }
80
81	public double compute(double x) {
82	double power = x;
83	double xsq = x * x;
84	double val = power;
85	double di = 1.0;
86	for (int i = n - 1; i > 0; --i) {
87	di += 2.0;
88	power *= xsq;
89	val += di * power;
90	}
91	return val;
92	}
93	}
94
95
96	static class Integrator {
97	final Function f; // The function to integrate
98	final double errorTolerance;
99	final ForkJoinPool g;
100
101	Integrator(Function f, double errorTolerance, ForkJoinPool g) {
102	this.f = f;
103	this.errorTolerance = errorTolerance;
104	this.g = g;
105	}
106
107	double integral(double lowerBound, double upperBound) {
108	double f_lower = f.compute(lowerBound);
109	double f_upper = f.compute(upperBound);
110	double initialArea = 0.5 * (upperBound-lowerBound) * (f_upper + f_lower);
111	Quad q = new Quad(lowerBound, upperBound,
112	f_lower, f_upper,
113	initialArea);
114	g.invoke(q);
115	return q.area;
116	}
117
118
119	/**
120	* FJTask to recursively perform the quadrature.
121	* Algorithm:
122	* Compute the area from lower bound to the center point of interval,
123	* and from the center point to the upper bound. If this
124	* differs from the value from lower to upper by more than
125	* the error tolerance, recurse on each half.
126	*/
127	final class Quad extends RecursiveAction {
128	final double left; // lower bound
129	final double right; // upper bound
130	final double f_left; // value of the function evaluated at left
131	final double f_right; // value of the function evaluated at right
132
133	// Area initialized with original estimate from left to right.
134	// It is replaced with refined value.
135	volatile double area;
136
137	Quad(double left, double right,
138	double f_left, double f_right,
139	double area) {
140	this.left = left;
141	this.right = right;
142	this.f_left = f_left;
143	this.f_right = f_right;
144	this.area = area;
145	}
146
147	public void compute() {
148	double center = 0.5 * (left + right);
149	double f_center = f.compute(center);
150
151	double leftArea = 0.5 * (center - left) * (f_left + f_center);
152	double rightArea = 0.5 * (right - center) * (f_center + f_right);
153	double sum = leftArea + rightArea;
154
155	double diff = sum - area;
156	if (diff < 0) diff = -diff;
157
158	if (diff >= errorTolerance) {
159	Quad q1 = new Quad(left, center, f_left, f_center, leftArea);
160	q1.fork();
161	Quad q2 = new Quad(center, right, f_center, f_right, rightArea);
162	q2.compute();
163	q1.join();
164	sum = q1.area + q2.area;
165	}
166
167	area = sum;
168	}
169	}
170	}
171
172	}