MPJ Express-如何使用散布将对象数组发送到Java中的其他进程

我试图使用MPI.COMM_WORLD.Scatter（）将一个对象数组分成几个块并发送给其他进程，但它总是在分散线处出现空指针错误，有什么办法解决这个问题吗？我发现如果sendbuf是一个基元类型的数组，就不会有问题

import mpi.*

public class Demo {

    public static void main(String args[]) {

        MPI.Init(args);
        int rank = MPI.COMM_WORLD.Rank();
        int size = MPI.COMM_WORLD.Size();
        int master = 0;
        int num = 0;    

        ArrayList<Location> locationList = null;
        Location[] locationArray = null;

        if(rank == master) {
           locationList = XXX; // XXX means read data from a file and create Location object into the list, the number of the objects is unknown
           locationArray = locationList.toArray(new Location[locationList.size()]);
        }

        // num - calculate the number of objects that each process will get

        MPI.COMM_WORLD.Scatter(locationArray, 0, num, MPI.OBJECT, recvbuf, 0, num, MPI.OBJECT, 0); 

        // The others processes does some operations on the recvbuf

        MPI.COMM_WORLD.Gater(new_locationArray, 0, num, MPI.OBJECT, new_recvbuf, 0, num, MPI.OBJECT, 0); 

        // the master process does some operations on the new_recvbuf

        MPI.Finalize();
    }
}

---

如果

Location[]locationArray=null，则为井如何进行迭代？尝试
Location[]locationArray=新位置[100]@ScaryWombat Thx，谢谢你的回复。实际上，数组的长度以前是未知的。我从文件中读取数据并将Location对象创建到ArrayList中，然后将其转换到Location[]，我更新了上面的代码。我只关心根列的输入缓冲区参数。可能是
recvbuf
为
null
。
public class Location {
    int id;
    public Location(int id) {
        this.id = id;
    }
}