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:	1.8
Committed:	Sun Oct 21 06:40:21 2012 UTC (11 years, 6 months ago) by jsr166
Branch:	MAIN
Changes since 1.7:	+0 -1 lines
Log Message:	no blank line between javadoc and corresponding code
#	User	Rev	Content
1	dl	1.1	/*
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	jsr166	1.5	* http://creativecommons.org/publicdomain/zero/1.0/
5	dl	1.1	*/
6
7			import java.util.concurrent.*;
8
9			/**
10			* Adapted from FJTask version.
11			* Sample program using Guassian Quadrature for numerical integration.
12	jsr166	1.2	* Inspired by a
13	dl	1.1	* <A href="http://www.cs.uga.edu/~dkl/filaments/dist.html"> Filaments</A>
14			* demo program.
15			*/
16			public class IntegrateGamma {
17			/** for time conversion */
18			static final long NPS = (1000L * 1000 * 1000);
19			public static void main(String[] args) {
20			int procs = 0;
21			double start = 1.0;
22			double end = 96.0;
23			int exp = 5;
24			try {
25			if (args.length > 0)
26			procs = Integer.parseInt(args[0]);
27			if (args.length > 1)
28			start = new Double(args[1]).doubleValue();
29			if (args.length > 2)
30			end = new Double(args[2]).doubleValue();
31	jsr166	1.2	if (args.length > 3)
32	dl	1.1	exp = Integer.parseInt(args[3]);
33			}
34			catch (Exception e) {
35			System.out.println("Usage: java IntegrateGamma <threads> <lower bound> <upper bound> <exponent>\n (for example 2 1 48 5).");
36			return;
37			}
38
39	jsr166	1.4	ForkJoinPool g = (procs == 0) ? new ForkJoinPool() :
40	dl	1.1	new ForkJoinPool(procs);
41
42			System.out.println("Integrating from " + start + " to " + end + " exponent: " + exp + " parallelism " + g.getParallelism());
43	jsr166	1.2
44	dl	1.1	Function f = new SampleFunction(exp);
45			for (int i = 0; i < 10; ++i) {
46			Integrator integrator = new Integrator(f, 0.001, g);
47			long last = System.nanoTime();
48			double result = integrator.integral(start, end);
49			double elapsed = elapsedTime(last);
50			System.out.printf("time: %7.3f", elapsed);
51			System.out.println(" Answer = " + result);
52	jsr166	1.2	}
53	dl	1.1	System.out.println(g);
54			g.shutdown();
55			}
56
57			static double elapsedTime(long startTime) {
58			return (double)(System.nanoTime() - startTime) / NPS;
59			}
60
61			/*
62			This is all set up as if it were part of a more serious
63			framework, but is for now just a demo, with all
64			classes declared as static within Integrate
65			*/
66
67	jsr166	1.3	/** A function to be integrated */
68	dl	1.1	static interface Function {
69			double compute(double x);
70			}
71
72			/**
73			* Sample from filaments demo.
74	jsr166	1.3	* Computes (2n-1)(x^(2*n-1)) for all odd values.
75			*/
76	dl	1.1	static class SampleFunction implements Function {
77			final int n;
78			SampleFunction(int n) { this.n = n; }
79
80	jsr166	1.3	public double compute(double x) {
81	dl	1.1	double power = x;
82			double xsq = x * x;
83			double val = power;
84			double di = 1.0;
85			for (int i = n - 1; i > 0; --i) {
86			di += 2.0;
87			power *= xsq;
88			val += di * power;
89			}
90			return val;
91			}
92			}
93
94
95			static class Integrator {
96			final Function f; // The function to integrate
97			final double errorTolerance;
98			final ForkJoinPool g;
99
100			Integrator(Function f, double errorTolerance, ForkJoinPool g) {
101			this.f = f;
102			this.errorTolerance = errorTolerance;
103			this.g = g;
104			}
105
106			double integral(double lowerBound, double upperBound) {
107			double f_lower = f.compute(lowerBound);
108			double f_upper = f.compute(upperBound);
109			double initialArea = 0.5 * (upperBound-lowerBound) * (f_upper + f_lower);
110			Quad q = new Quad(lowerBound, upperBound,
111			f_lower, f_upper,
112			initialArea);
113			g.invoke(q);
114			return q.area;
115			}
116
117	jsr166	1.2
118			/**
119	dl	1.1	* FJTask to recursively perform the quadrature.
120			* Algorithm:
121			* Compute the area from lower bound to the center point of interval,
122			* and from the center point to the upper bound. If this
123			* differs from the value from lower to upper by more than
124			* the error tolerance, recurse on each half.
125	jsr166	1.3	*/
126	dl	1.1	final class Quad extends RecursiveAction {
127			final double left; // lower bound
128			final double right; // upper bound
129			final double f_left; // value of the function evaluated at left
130			final double f_right; // value of the function evaluated at right
131	jsr166	1.2
132	dl	1.1	// Area initialized with original estimate from left to right.
133			// It is replaced with refined value.
134			volatile double area;
135	jsr166	1.2
136			Quad(double left, double right,
137			double f_left, double f_right,
138	dl	1.1	double area) {
139			this.left = left;
140			this.right = right;
141			this.f_left = f_left;
142			this.f_right = f_right;
143			this.area = area;
144			}
145	jsr166	1.2
146	dl	1.1	public void compute() {
147			double center = 0.5 * (left + right);
148	jsr166	1.2	double f_center = f.compute(center);
149
150			double leftArea = 0.5 * (center - left) * (f_left + f_center);
151	dl	1.1	double rightArea = 0.5 * (right - center) * (f_center + f_right);
152			double sum = leftArea + rightArea;
153	jsr166	1.2
154	dl	1.1	double diff = sum - area;
155			if (diff < 0) diff = -diff;
156	jsr166	1.2
157			if (diff >= errorTolerance) {
158	dl	1.1	Quad q1 = new Quad(left, center, f_left, f_center, leftArea);
159			q1.fork();
160			Quad q2 = new Quad(center, right, f_center, f_right, rightArea);
161			q2.compute();
162			q1.join();
163	jsr166	1.2	sum = q1.area + q2.area;
164	dl	1.1	}
165	jsr166	1.2
166	dl	1.1	area = sum;
167			}
168			}
169			}
170
171			}