test/loops/ThreadPhaserJacobi.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/licenses/publicdomain
 */

// Barrier version of Jacobi iteration

import java.util.*;
import java.util.concurrent.*;
//import jsr166y.*;

public class ThreadPhaserJacobi {

    static final int nprocs = Runtime.getRuntime().availableProcessors();

    /**
     * The maximum submatrix length (both row-wise and column-wise)
     * for any Segment
     **/

    static final double EPSILON = 0.0001;  // convergence criterion

    static int dimGran;

    public static void main(String[] args) throws Exception {
        int n = 2048;
        int steps = 1000;
        try {
            if (args.length > 0)
                n = Integer.parseInt(args[0]);
            if (args.length > 1)
                steps = Integer.parseInt(args[1]);
        }

        catch (Exception e) {
            System.out.println("Usage: java ThreadPhaserJacobi <matrix size> <max steps>");
            return;
        }

        int granularity = n * n / nprocs;
        dimGran = (int)(Math.sqrt(granularity));

        // allocate enough space for edges
        int dim = n+2;
        int ncells = dim * dim;
        double[][] a = new double[dim][dim];
        double[][] b = new double[dim][dim];
        // Initialize interiors to small value
        double smallVal = 1.0/dim;
        for (int i = 1; i < dim-1; ++i) {
            for (int j = 1; j < dim-1; ++j)
                a[i][j] = smallVal;
        }

        int nreps = 3;
        for (int rep = 0; rep < nreps; ++rep) {
            // Fill all edges with 1's.
            for (int k = 0; k < dim; ++k) {
                a[k][0] += 1.0;
                a[k][n+1] += 1.0;
                a[0][k] += 1.0;
                a[n+1][k] += 1.0;
            }
            Driver driver = new Driver(a, b, 1, n, 1, n, steps);
            long startTime = System.currentTimeMillis();
            driver.compute();

            long time = System.currentTimeMillis() - startTime;
            double secs = ((double)time) / 1000.0;

            System.out.println("Compute Time: " + secs);
        }
    }

    static class Segment implements Runnable {

        double[][] A; // matrix to get old values from
        double[][] B; // matrix to put new values into

        // indices of current submatrix
        final int loRow;
        final int hiRow;
        final int loCol;
        final int hiCol;
        final int steps;
        final Phaser barrier;
        double maxDiff; // maximum difference between old and new values

        Segment(double[][] A, double[][] B,
                int loRow, int hiRow,
                int loCol, int hiCol,
                int steps,
                Phaser barrier) {
            this.A = A;   this.B = B;
            this.loRow = loRow; this.hiRow = hiRow;
            this.loCol = loCol; this.hiCol = hiCol;
            this.steps = steps;
            this.barrier = barrier;
            barrier.register();
        }


        public void run() {
            try {
                double[][] a = A;
                double[][] b = B;

                for (int i = 0; i < steps; ++i) {
                    maxDiff = update(a, b);
                    if (barrier.awaitAdvance(barrier.arrive()) < 0)
                        break;
                    double[][] tmp = a; a = b; b = tmp;
                }
            }
            catch(Exception ex) {
                ex.printStackTrace();
                return;
            }
        }

        double update(double[][] a, double[][] b) {
            double md = 0.0; // local for computing max diff

            for (int i = loRow; i <= hiRow; ++i) {
                for (int j = loCol; j <= hiCol; ++j) {
                    double v = 0.25 * (a[i-1][j] + a[i][j-1] +
                                       a[i+1][j] + a[i][j+1]);
                    b[i][j] = v;

                    double diff = v - a[i][j];
                    if (diff < 0) diff = -diff;
                    if (diff > md) md = diff;
                }
            }

            return md;
        }

    }


    static class Driver {
        double[][] A; // matrix to get old values from
        double[][] B; // matrix to put new values into

        final int loRow;   // indices of current submatrix
        final int hiRow;
        final int loCol;
        final int hiCol;
        final int steps;
        Segment[] allSegments;

        Driver(double[][] mat1, double[][] mat2,
               int firstRow, int lastRow,
               int firstCol, int lastCol,
               int steps) {

            this.A = mat1;   this.B = mat2;
            this.loRow = firstRow; this.hiRow = lastRow;
            this.loCol = firstCol; this.hiCol = lastCol;
            this.steps = steps;

            int rows = hiRow - loRow + 1;
            int cols = hiCol - loCol + 1;
            int rblocks = (int)(Math.round((float)rows / dimGran));
            int cblocks = (int)(Math.round((float)cols / dimGran));

            int n = rblocks * cblocks;

            Segment[] segs = new Segment[n];
            Phaser barrier = new Phaser();
            int k = 0;
            for (int i = 0; i < rblocks; ++i) {
                int lr = loRow + i * dimGran;
                int hr = lr + dimGran;
                if (i == rblocks-1) hr = hiRow;

                for (int j = 0; j < cblocks; ++j) {
                    int lc = loCol + j * dimGran;
                    int hc = lc + dimGran;
                    if (j == cblocks-1) hc = hiCol;

                    segs[k] = new Segment(A, B, lr, hr, lc, hc, steps, barrier);
                    ++k;
                }
            }
            System.out.println("Using " + n + " segments (threads)");
            allSegments = segs;
        }

        public void compute() throws InterruptedException {
            Segment[] segs = allSegments;
            int n = segs.length;
            Thread[] threads = new Thread[n];

            for (int k = 0; k < n; ++k) threads[k] = new Thread(segs[k]);
            for (int k = 0; k < n; ++k) threads[k].start();
            for (int k = 0; k < n; ++k) threads[k].join();

            double maxd = 0;
            for (int k = 0; k < n; ++k) {
                double md = segs[k].maxDiff;
                if (md > maxd) maxd = md;
            }

            System.out.println("Max diff after " + steps + " steps = " + maxd);
        }
    }


}
Revision:	1.3
Committed:	Fri Oct 30 14:15:04 2009 UTC (14 years, 6 months ago) by dl
Branch:	MAIN
Changes since 1.2:	+6 -0 lines
Log Message:	Missing file headers
#	User	Rev	Content
1	dl	1.3	/*
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/licenses/publicdomain
5			*/
6
7	dl	1.1	// Barrier version of Jacobi iteration
8
9			import java.util.*;
10			import java.util.concurrent.*;
11			//import jsr166y.*;
12
13			public class ThreadPhaserJacobi {
14
15			static final int nprocs = Runtime.getRuntime().availableProcessors();
16
17	jsr166	1.2	/**
18	dl	1.1	* The maximum submatrix length (both row-wise and column-wise)
19			* for any Segment
20			**/
21
22			static final double EPSILON = 0.0001; // convergence criterion
23
24			static int dimGran;
25
26			public static void main(String[] args) throws Exception {
27			int n = 2048;
28			int steps = 1000;
29			try {
30			if (args.length > 0)
31			n = Integer.parseInt(args[0]);
32			if (args.length > 1)
33			steps = Integer.parseInt(args[1]);
34			}
35	jsr166	1.2
36	dl	1.1	catch (Exception e) {
37			System.out.println("Usage: java ThreadPhaserJacobi <matrix size> <max steps>");
38			return;
39			}
40
41			int granularity = n * n / nprocs;
42			dimGran = (int)(Math.sqrt(granularity));
43
44			// allocate enough space for edges
45			int dim = n+2;
46			int ncells = dim * dim;
47			double[][] a = new double[dim][dim];
48			double[][] b = new double[dim][dim];
49			// Initialize interiors to small value
50	jsr166	1.2	double smallVal = 1.0/dim;
51	dl	1.1	for (int i = 1; i < dim-1; ++i) {
52			for (int j = 1; j < dim-1; ++j)
53			a[i][j] = smallVal;
54			}
55	jsr166	1.2
56	dl	1.1	int nreps = 3;
57			for (int rep = 0; rep < nreps; ++rep) {
58			// Fill all edges with 1's.
59			for (int k = 0; k < dim; ++k) {
60			a[k][0] += 1.0;
61			a[k][n+1] += 1.0;
62			a[0][k] += 1.0;
63			a[n+1][k] += 1.0;
64			}
65			Driver driver = new Driver(a, b, 1, n, 1, n, steps);
66			long startTime = System.currentTimeMillis();
67			driver.compute();
68	jsr166	1.2
69	dl	1.1	long time = System.currentTimeMillis() - startTime;
70			double secs = ((double)time) / 1000.0;
71	jsr166	1.2
72	dl	1.1	System.out.println("Compute Time: " + secs);
73			}
74			}
75
76			static class Segment implements Runnable {
77
78			double[][] A; // matrix to get old values from
79			double[][] B; // matrix to put new values into
80
81			// indices of current submatrix
82	jsr166	1.2	final int loRow;
83	dl	1.1	final int hiRow;
84			final int loCol;
85			final int hiCol;
86			final int steps;
87			final Phaser barrier;
88			double maxDiff; // maximum difference between old and new values
89
90	jsr166	1.2	Segment(double[][] A, double[][] B,
91	dl	1.1	int loRow, int hiRow,
92			int loCol, int hiCol,
93			int steps,
94			Phaser barrier) {
95			this.A = A; this.B = B;
96			this.loRow = loRow; this.hiRow = hiRow;
97			this.loCol = loCol; this.hiCol = hiCol;
98			this.steps = steps;
99			this.barrier = barrier;
100			barrier.register();
101			}
102
103
104			public void run() {
105			try {
106			double[][] a = A;
107			double[][] b = B;
108	jsr166	1.2
109	dl	1.1	for (int i = 0; i < steps; ++i) {
110			maxDiff = update(a, b);
111			if (barrier.awaitAdvance(barrier.arrive()) < 0)
112			break;
113			double[][] tmp = a; a = b; b = tmp;
114			}
115			}
116	jsr166	1.2	catch(Exception ex) {
117	dl	1.1	ex.printStackTrace();
118			return;
119			}
120			}
121
122			double update(double[][] a, double[][] b) {
123			double md = 0.0; // local for computing max diff
124
125			for (int i = loRow; i <= hiRow; ++i) {
126			for (int j = loCol; j <= hiCol; ++j) {
127			double v = 0.25 * (a[i-1][j] + a[i][j-1] +
128			a[i+1][j] + a[i][j+1]);
129			b[i][j] = v;
130
131			double diff = v - a[i][j];
132			if (diff < 0) diff = -diff;
133			if (diff > md) md = diff;
134			}
135			}
136
137			return md;
138			}
139	jsr166	1.2
140	dl	1.1	}
141
142	jsr166	1.2
143			static class Driver {
144	dl	1.1	double[][] A; // matrix to get old values from
145			double[][] B; // matrix to put new values into
146
147			final int loRow; // indices of current submatrix
148			final int hiRow;
149			final int loCol;
150			final int hiCol;
151			final int steps;
152			Segment[] allSegments;
153
154	jsr166	1.2	Driver(double[][] mat1, double[][] mat2,
155	dl	1.1	int firstRow, int lastRow,
156			int firstCol, int lastCol,
157			int steps) {
158	jsr166	1.2
159	dl	1.1	this.A = mat1; this.B = mat2;
160			this.loRow = firstRow; this.hiRow = lastRow;
161			this.loCol = firstCol; this.hiCol = lastCol;
162			this.steps = steps;
163
164			int rows = hiRow - loRow + 1;
165			int cols = hiCol - loCol + 1;
166			int rblocks = (int)(Math.round((float)rows / dimGran));
167			int cblocks = (int)(Math.round((float)cols / dimGran));
168	jsr166	1.2
169	dl	1.1	int n = rblocks * cblocks;
170	jsr166	1.2
171	dl	1.1	Segment[] segs = new Segment[n];
172			Phaser barrier = new Phaser();
173			int k = 0;
174			for (int i = 0; i < rblocks; ++i) {
175			int lr = loRow + i * dimGran;
176			int hr = lr + dimGran;
177			if (i == rblocks-1) hr = hiRow;
178	jsr166	1.2
179	dl	1.1	for (int j = 0; j < cblocks; ++j) {
180			int lc = loCol + j * dimGran;
181			int hc = lc + dimGran;
182			if (j == cblocks-1) hc = hiCol;
183	jsr166	1.2
184	dl	1.1	segs[k] = new Segment(A, B, lr, hr, lc, hc, steps, barrier);
185			++k;
186			}
187			}
188			System.out.println("Using " + n + " segments (threads)");
189			allSegments = segs;
190			}
191
192			public void compute() throws InterruptedException {
193			Segment[] segs = allSegments;
194			int n = segs.length;
195			Thread[] threads = new Thread[n];
196
197			for (int k = 0; k < n; ++k) threads[k] = new Thread(segs[k]);
198			for (int k = 0; k < n; ++k) threads[k].start();
199			for (int k = 0; k < n; ++k) threads[k].join();
200
201			double maxd = 0;
202			for (int k = 0; k < n; ++k) {
203			double md = segs[k].maxDiff;
204			if (md > maxd) maxd = md;
205			}
206
207			System.out.println("Max diff after " + steps + " steps = " + maxd);
208			}
209			}
210
211
212			}