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 = Math.round((float) rows / dimGran);
            int cblocks = 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:	1.7
Committed:	Sat Oct 16 16:22:57 2010 UTC (13 years, 7 months ago) by jsr166
Branch:	MAIN
Changes since 1.6:	+1 -2 lines
Log Message:	coding style
#	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/licenses/publicdomain
5	*/
6
7	// 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	/**
18	* The maximum submatrix length (both row-wise and column-wise)
19	* for any Segment
20	*/
21	static final double EPSILON = 0.0001; // convergence criterion
22
23	static int dimGran;
24
25	public static void main(String[] args) throws Exception {
26	int n = 2048;
27	int steps = 1000;
28	try {
29	if (args.length > 0)
30	n = Integer.parseInt(args[0]);
31	if (args.length > 1)
32	steps = Integer.parseInt(args[1]);
33	}
34
35	catch (Exception e) {
36	System.out.println("Usage: java ThreadPhaserJacobi <matrix size> <max steps>");
37	return;
38	}
39
40	int granularity = n * n / nprocs;
41	dimGran = (int) Math.sqrt(granularity);
42
43	// allocate enough space for edges
44	int dim = n+2;
45	int ncells = dim * dim;
46	double[][] a = new double[dim][dim];
47	double[][] b = new double[dim][dim];
48	// Initialize interiors to small value
49	double smallVal = 1.0/dim;
50	for (int i = 1; i < dim-1; ++i) {
51	for (int j = 1; j < dim-1; ++j)
52	a[i][j] = smallVal;
53	}
54
55	int nreps = 3;
56	for (int rep = 0; rep < nreps; ++rep) {
57	// Fill all edges with 1's.
58	for (int k = 0; k < dim; ++k) {
59	a[k][0] += 1.0;
60	a[k][n+1] += 1.0;
61	a[0][k] += 1.0;
62	a[n+1][k] += 1.0;
63	}
64	Driver driver = new Driver(a, b, 1, n, 1, n, steps);
65	long startTime = System.currentTimeMillis();
66	driver.compute();
67
68	long time = System.currentTimeMillis() - startTime;
69	double secs = (double) time / 1000.0;
70
71	System.out.println("Compute Time: " + secs);
72	}
73	}
74
75	static class Segment implements Runnable {
76
77	double[][] A; // matrix to get old values from
78	double[][] B; // matrix to put new values into
79
80	// indices of current submatrix
81	final int loRow;
82	final int hiRow;
83	final int loCol;
84	final int hiCol;
85	final int steps;
86	final Phaser barrier;
87	double maxDiff; // maximum difference between old and new values
88
89	Segment(double[][] A, double[][] B,
90	int loRow, int hiRow,
91	int loCol, int hiCol,
92	int steps,
93	Phaser barrier) {
94	this.A = A; this.B = B;
95	this.loRow = loRow; this.hiRow = hiRow;
96	this.loCol = loCol; this.hiCol = hiCol;
97	this.steps = steps;
98	this.barrier = barrier;
99	barrier.register();
100	}
101
102
103	public void run() {
104	try {
105	double[][] a = A;
106	double[][] b = B;
107
108	for (int i = 0; i < steps; ++i) {
109	maxDiff = update(a, b);
110	if (barrier.awaitAdvance(barrier.arrive()) < 0)
111	break;
112	double[][] tmp = a; a = b; b = tmp;
113	}
114	}
115	catch (Exception ex) {
116	ex.printStackTrace();
117	return;
118	}
119	}
120
121	double update(double[][] a, double[][] b) {
122	double md = 0.0; // local for computing max diff
123
124	for (int i = loRow; i <= hiRow; ++i) {
125	for (int j = loCol; j <= hiCol; ++j) {
126	double v = 0.25 * (a[i-1][j] + a[i][j-1] +
127	a[i+1][j] + a[i][j+1]);
128	b[i][j] = v;
129
130	double diff = v - a[i][j];
131	if (diff < 0) diff = -diff;
132	if (diff > md) md = diff;
133	}
134	}
135
136	return md;
137	}
138
139	}
140
141
142	static class Driver {
143	double[][] A; // matrix to get old values from
144	double[][] B; // matrix to put new values into
145
146	final int loRow; // indices of current submatrix
147	final int hiRow;
148	final int loCol;
149	final int hiCol;
150	final int steps;
151	Segment[] allSegments;
152
153	Driver(double[][] mat1, double[][] mat2,
154	int firstRow, int lastRow,
155	int firstCol, int lastCol,
156	int steps) {
157
158	this.A = mat1; this.B = mat2;
159	this.loRow = firstRow; this.hiRow = lastRow;
160	this.loCol = firstCol; this.hiCol = lastCol;
161	this.steps = steps;
162
163	int rows = hiRow - loRow + 1;
164	int cols = hiCol - loCol + 1;
165	int rblocks = Math.round((float) rows / dimGran);
166	int cblocks = Math.round((float) cols / dimGran);
167
168	int n = rblocks * cblocks;
169
170	Segment[] segs = new Segment[n];
171	Phaser barrier = new Phaser();
172	int k = 0;
173	for (int i = 0; i < rblocks; ++i) {
174	int lr = loRow + i * dimGran;
175	int hr = lr + dimGran;
176	if (i == rblocks-1) hr = hiRow;
177
178	for (int j = 0; j < cblocks; ++j) {
179	int lc = loCol + j * dimGran;
180	int hc = lc + dimGran;
181	if (j == cblocks-1) hc = hiCol;
182
183	segs[k] = new Segment(A, B, lr, hr, lc, hc, steps, barrier);
184	++k;
185	}
186	}
187	System.out.println("Using " + n + " segments (threads)");
188	allSegments = segs;
189	}
190
191	public void compute() throws InterruptedException {
192	Segment[] segs = allSegments;
193	int n = segs.length;
194	Thread[] threads = new Thread[n];
195
196	for (int k = 0; k < n; ++k) threads[k] = new Thread(segs[k]);
197	for (int k = 0; k < n; ++k) threads[k].start();
198	for (int k = 0; k < n; ++k) threads[k].join();
199
200	double maxd = 0;
201	for (int k = 0; k < n; ++k) {
202	double md = segs[k].maxDiff;
203	if (md > maxd) maxd = md;
204	}
205
206	System.out.println("Max diff after " + steps + " steps = " + maxd);
207	}
208	}
209
210
211	}