Java并发编程--fork-join framework(a parallelizable algorithm)

数组归并排序代码实现（ForkJoin版）:

/**

*

*/

package concurrent.forkjoin;

import java.util.Arrays;

import java.util.concurrent.ForkJoinPool;

import java.util.concurrent.RecursiveAction;

import algorithm.sort.MergeSortAlgorithm;

/**

* A merge sort demonstration algorithm with the fork-join framework(a parallelizable algorithm)

*

* 数组归并排序: http://blog.csdn.net/yang_net/archive/2010/08/01/5781012.aspx
*

* @author yangwm Aug 12, 2010 11:15:47 AM

*/

public class MergeSortForkJoin extends RecursiveAction {

/**

*

*/

private static final long serialVersionUID = -7490351302704617127L;

private static final int THRESHOLD = 4;

private final int[] number;

private int[] result;

public MergeSortForkJoin(int[] number) {

this.number = number;

}

@Override

protected void compute() {

if (number.length <= THRESHOLD) {

result = MergeSortAlgorithm.mergeSort(number);

} else {

int middle = number.length / 2;

/*

* Partition the list into two lists and sort them recursively

*/

int left[] = new int[middle];

for (int i = 0; i < middle; i++) {

left[i] = number[i];

}

int right[] = new int[number.length - middle];

for (int i = 0; i < number.length - middle; i++) {

right[i] = number[middle + i];

}

/*

* Merge the two sorted lists

*/

MergeSortForkJoin leftForkJoin = new MergeSortForkJoin(left);

MergeSortForkJoin rightForkJoin = new MergeSortForkJoin(right);

invokeAll(leftForkJoin, rightForkJoin); // coInvoke(leftForkJoin, rightForkJoin);

result = MergeSortAlgorithm.merge(leftForkJoin.result, rightForkJoin.result);

}

}

public int[] merge(int left[], int right[]) {

int[] result = new int[left.length + right.length];

int leftPos = 0;

int rightPos = 0;

int resultPos = 0;

while (leftPos < left.length && rightPos < right.length) {

/* Merge sorted sublists */

if (left[leftPos] <= right[rightPos]) {

result[resultPos++] = left[leftPos++];

} else {

result[resultPos++] = right[rightPos++];

}

}

if (leftPos < left.length) {

/* append left to result */

while (leftPos < left.length) {

result[resultPos++] = left[leftPos++];

}

} else {

/* append right to result */

while (rightPos < right.length) {

result[resultPos++] = right[rightPos++];

}

}

return result;

}

public static void main(String[] args) {

int[] number = { 4, 2, 1, 2, 7, 3, 9, 0, 0, 11, 10, 6, 15, 8 };

MergeSortForkJoin mergeSortForkJoin = new MergeSortForkJoin(number);

ForkJoinPool forkJoinPool = new ForkJoinPool();

forkJoinPool.invoke(mergeSortForkJoin);

System.out.println(Arrays.toString(mergeSortForkJoin.result));

}

}

输出：

[0, 0, 1, 2, 2, 3, 4, 6, 7, 8, 9, 10, 11, 15]

学习参考资料：

Stick a fork in it, Part I & Stick a fork in it, Part II : http://www.briangoetz.com/pubs.html
A Java ForkJoin Framework: http://gee.cs.oswego.edu/dl/papers/fj.pdf
JDK 7 中的 Fork/Join 模式 : http://www.ibm.com/developerworks/cn/java/j-lo-forkjoin/
RecursiveAction (Java Platform SE 7) : http://download.java.net/jdk7/docs/api/java/util/concurrent/RecursiveAction.html