JDK 7 中的 Fork/Join 模式

参考1：http://www.ibm.com/developerworks/cn/java/j-lo-forkjoin/#list1

JDK 7 中的 Fork/Join 模式

参考2：http://www.ibm.com/developerworks/cn/java/j-jtp11137.html

Java 理论与实践: 应用 fork-join 框架

参考3：http://www.ibm.com/developerworks/cn/java/j-jtp03048.html

Java 理论与实践: 应用 fork-join 框架，第 2 部分

参考4：http://www.ibm.com/developerworks/cn/java/j-java7.html

Java 技术，IBM 风格: Java 技术的新纪元

看看了《JDK 7 中的 Fork/Join 模式》本来想试一试，结果没有试出来。盼高手指点：SortTask中找不到coInvoke函数了。

程序是：

public class TestForkJoinSimple {
	private static final int NARRAY = 16; //For demo only
    long[] array = new long[NARRAY];
    Random rand = new Random();

    @Before
    public void setUp() {
        for (int i = 0; i < array.length; i++) {
            array[i] = rand.nextLong()%100; //For demo only
        }
        System.out.println("Initial Array: " + Arrays.toString(array));
    }

    @Test
    public void testSort() throws Exception {
        ForkJoinTask sort = new SortTask(array);
        ForkJoinPool fjpool = new ForkJoinPool();
        fjpool.submit(sort);
        fjpool.shutdown();

        fjpool.awaitTermination(30, TimeUnit.SECONDS);

        assertTrue(checkSorted(array));
    }

    boolean checkSorted(long[] a) {
        for (int i = 0; i < a.length - 1; i++) {
            if (a[i] > (a[i + 1])) {
                return false;
            }
        }
        return true;
    }
}

class SortTask extends RecursiveAction {
    final long[] array;
    final int lo;
    final int hi;
    private int THRESHOLD = 0; //For demo only

    public SortTask(long[] array) {
        this.array = array;
        this.lo = 0;
        this.hi = array.length - 1;
    }

    public SortTask(long[] array, int lo, int hi) {
        this.array = array;
        this.lo = lo;
        this.hi = hi;
    }

    protected void compute() {
        if (hi - lo < THRESHOLD)
            sequentiallySort(array, lo, hi);
        else {
            int pivot = partition(array, lo, hi);
            System.out.println("\npivot = " + pivot + ", low = " + lo + ", high = " + hi);
			System.out.println("array" + Arrays.toString(array));
            coInvoke(new SortTask(array, lo, pivot - 1), new SortTask(array,
                    pivot + 1, hi));
        }
    }

    private int partition(long[] array, int lo, int hi) {
        long x = array[hi];
        int i = lo - 1;
        for (int j = lo; j < hi; j++) {
            if (array[j] <= x) {
                i++;
                swap(array, i, j);
            }
        }
        swap(array, i + 1, hi);
        return i + 1;
    }

    private void swap(long[] array, int i, int j) {
        if (i != j) {
            long temp = array[i];
            array[i] = array[j];
            array[j] = temp;
        }
    }

    private void sequentiallySort(long[] array, int lo, int hi) {
        Arrays.sort(array, lo, hi + 1);
    }
}

 

详细说明看参考1，需要jdk6和JSR-166y（http://g.oswego.edu/dl/concurrency-interest/）。

评论

2 楼 hj01kkk 2015-07-27  

1楼用法正解

1 楼 fish_no7 2015-04-09  

使用 new SortTask().fork()