test/loops/NQueensCS.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
 */

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

public final class NQueensCS extends RecursiveAction {

    static long lastStealCount;
    static int boardSize;

    static final int[] expectedSolutions = new int[] {
        0, 1, 0, 0, 2, 10, 4, 40, 92, 352, 724, 2680, 14200,
        73712, 365596, 2279184, 14772512, 95815104, 666090624
    }; // see http://www.durangobill.com/N_Queens.html

    static final int FIRST_SIZE = 8; // smaller ones too short to measure well
    static final int LAST_SIZE = 15; // bigger ones too long to wait for

    /** for time conversion */
    static final long NPS = (1000L * 1000 * 1000);

    public static void main(String[] args) throws Exception {
        int procs = 0;
        try {
            if (args.length > 0)
                procs = Integer.parseInt(args[0]);
        }
        catch (Exception e) {
            System.out.println("Usage: java NQueensCS <threads> ");
            return;
        }
        for (int reps = 0; reps < 2; ++reps) {
            ForkJoinPool g = (procs == 0) ? new ForkJoinPool() :
                new ForkJoinPool(procs);
            lastStealCount = g.getStealCount();
            for (int i = FIRST_SIZE; i <= LAST_SIZE; i++)
                test(g, i);
            System.out.println(g);
            g.shutdown();
        }
    }

    static void test(ForkJoinPool g, int i) throws Exception {
        boardSize = i;
        int ps = g.getParallelism();
        long start = System.nanoTime();
        NQueensCS task = new NQueensCS(new int[0]);
        g.invoke(task);
        int solutions = task.solutions;
        long time = System.nanoTime() - start;
        double secs = ((double)time) / NPS;
        if (solutions != expectedSolutions[i])
            throw new Error();
        System.out.printf("NQueensCS %3d", i);
        System.out.printf(" Time: %7.3f", secs);
        long sc = g.getStealCount();
        long ns = sc - lastStealCount;
        lastStealCount = sc;
        System.out.printf(" Steals/t: %5d", ns/ps);
        System.out.println();
    }

    // Boards are represented as arrays where each cell
    // holds the column number of the queen in that row

    final int[] sofar;
    NQueensCS nextSubtask; // to link subtasks
    int solutions;
    NQueensCS(int[] a) {
        this.sofar = a;
    }

    public final void compute() {
        NQueensCS subtasks;
        int bs = boardSize;
        if (sofar.length >= bs)
            solutions = 1;
        else if ((subtasks = explore(sofar, bs)) != null)
            solutions = processSubtasks(subtasks);
    }

    private static NQueensCS explore(int[] array, int bs) {
        int row = array.length;
        NQueensCS s = null; // subtask list
        outer:
        for (int q = 0; q < bs; ++q) {
            for (int i = 0; i < row; i++) {
                int p = array[i];
                if (q == p || q == p - (row - i) || q == p + (row - i))
                    continue outer; // attacked
            }
            NQueensCS first = s; // lag forks to ensure 1 kept
            if (first != null)
                first.fork();
            int[] next = Arrays.copyOf(array, row+1);
            next[row] = q;
            NQueensCS subtask = new NQueensCS(next);
            subtask.nextSubtask = first;
            s = subtask;
        }
        return s;
    }

    private static int processSubtasks(NQueensCS s) {
        // Always run first the task held instead of forked
        s.compute();
        int ns = s.solutions;
        s = s.nextSubtask;
        // Then the unstolen ones
        while (s != null && s.tryUnfork()) {
            s.compute();
            ns += s.solutions;
            s = s.nextSubtask;
        }
        // Then wait for the stolen ones
        while (s != null) {
            s.join();
            ns += s.solutions;
            s = s.nextSubtask;
        }
        return ns;
    }
}
Revision:	1.7
Committed:	Mon Nov 29 20:58:07 2010 UTC (13 years, 5 months ago) by jsr166
Branch:	MAIN
Changes since 1.6:	+1 -1 lines
Log Message:	consistent ternary operator style
#	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			* http://creativecommons.org/licenses/publicdomain
5			*/
6
7			//import jsr166y.*;
8			import java.util.*;
9			import java.util.concurrent.*;
10
11			public final class NQueensCS extends RecursiveAction {
12
13			static long lastStealCount;
14			static int boardSize;
15
16			static final int[] expectedSolutions = new int[] {
17			0, 1, 0, 0, 2, 10, 4, 40, 92, 352, 724, 2680, 14200,
18			73712, 365596, 2279184, 14772512, 95815104, 666090624
19			}; // see http://www.durangobill.com/N_Queens.html
20
21			static final int FIRST_SIZE = 8; // smaller ones too short to measure well
22			static final int LAST_SIZE = 15; // bigger ones too long to wait for
23
24			/** for time conversion */
25			static final long NPS = (1000L * 1000 * 1000);
26	jsr166	1.6
27	dl	1.1	public static void main(String[] args) throws Exception {
28			int procs = 0;
29			try {
30			if (args.length > 0)
31			procs = Integer.parseInt(args[0]);
32			}
33			catch (Exception e) {
34			System.out.println("Usage: java NQueensCS <threads> ");
35			return;
36			}
37			for (int reps = 0; reps < 2; ++reps) {
38	jsr166	1.7	ForkJoinPool g = (procs == 0) ? new ForkJoinPool() :
39	dl	1.1	new ForkJoinPool(procs);
40			lastStealCount = g.getStealCount();
41			for (int i = FIRST_SIZE; i <= LAST_SIZE; i++)
42			test(g, i);
43			System.out.println(g);
44	jsr166	1.6	g.shutdown();
45	dl	1.1	}
46			}
47
48			static void test(ForkJoinPool g, int i) throws Exception {
49			boardSize = i;
50			int ps = g.getParallelism();
51			long start = System.nanoTime();
52			NQueensCS task = new NQueensCS(new int[0]);
53			g.invoke(task);
54			int solutions = task.solutions;
55			long time = System.nanoTime() - start;
56	dl	1.5	double secs = ((double)time) / NPS;
57	dl	1.1	if (solutions != expectedSolutions[i])
58			throw new Error();
59			System.out.printf("NQueensCS %3d", i);
60			System.out.printf(" Time: %7.3f", secs);
61			long sc = g.getStealCount();
62			long ns = sc - lastStealCount;
63			lastStealCount = sc;
64			System.out.printf(" Steals/t: %5d", ns/ps);
65			System.out.println();
66	jsr166	1.6	}
67	dl	1.1
68	jsr166	1.6	// Boards are represented as arrays where each cell
69	dl	1.1	// holds the column number of the queen in that row
70
71			final int[] sofar;
72			NQueensCS nextSubtask; // to link subtasks
73			int solutions;
74	jsr166	1.6	NQueensCS(int[] a) {
75			this.sofar = a;
76	dl	1.1	}
77
78			public final void compute() {
79			NQueensCS subtasks;
80			int bs = boardSize;
81			if (sofar.length >= bs)
82			solutions = 1;
83			else if ((subtasks = explore(sofar, bs)) != null)
84			solutions = processSubtasks(subtasks);
85			}
86
87			private static NQueensCS explore(int[] array, int bs) {
88			int row = array.length;
89			NQueensCS s = null; // subtask list
90			outer:
91			for (int q = 0; q < bs; ++q) {
92			for (int i = 0; i < row; i++) {
93			int p = array[i];
94			if (q == p \|\| q == p - (row - i) \|\| q == p + (row - i))
95			continue outer; // attacked
96			}
97			NQueensCS first = s; // lag forks to ensure 1 kept
98			if (first != null)
99			first.fork();
100			int[] next = Arrays.copyOf(array, row+1);
101			next[row] = q;
102			NQueensCS subtask = new NQueensCS(next);
103			subtask.nextSubtask = first;
104			s = subtask;
105			}
106			return s;
107			}
108
109			private static int processSubtasks(NQueensCS s) {
110			// Always run first the task held instead of forked
111	jsr166	1.6	s.compute();
112	dl	1.1	int ns = s.solutions;
113			s = s.nextSubtask;
114			// Then the unstolen ones
115			while (s != null && s.tryUnfork()) {
116			s.compute();
117			ns += s.solutions;
118			s = s.nextSubtask;
119			}
120			// Then wait for the stolen ones
121			while (s != null) {
122			s.join();
123			ns += s.solutions;
124			s = s.nextSubtask;
125			}
126			return ns;
127			}
128			}