问MapReduce - 在java中实现多个进程

EN

final int cpuCores=4; //or Runtime.getRuntime().availableProcessors();

@Test
public void threadedOperation()
{
    int[] ints=new int[new Random().nextInt(2000)+4000];
    System.out.println("Array size="+ints.length);
    Arrays.fill(ints,2);
    int chunksize;
    final int arraysize=ints.length;
    final int remainder=arraysize % cpuCores;
    //checking if the work can be split among threads evenly
    if(remainder==0)
    {
        chunksize=arraysize/cpuCores;
    }
    else{
        //can't split evenly, so take the remainder into acoount
        int in=arraysize-remainder;
        chunksize=in/cpuCores;
        System.out.println("Remainder="+remainder);
    }
    System.out.println("Chunk size="+chunksize);
    System.out.println("Threads="+cpuCores);

    assert chunksize*cpuCores+remainder==arraysize;
    for (int core = 0; core < cpuCores; core++) {
        int start=core * chunksize;
        int end = start + chunksize;
        if(core==cpuCores-1)
        {
            //here I "add" the remainder to the last thread
            if (remainder != 0) {
                end=start+chunksize+remainder;
            }
        }

        System.out.println("Start="+start+" end="+end);
        int finalEnd = end;
        Thread thread=new Thread(() -> {
            for (int i = start; i < finalEnd; i++) {
                //do your work here, I'm just asserting that the array is filled
                assert ints[i]==2;
            }
        });
        thread.start();
    }
}