在java中的main之外初始化MPI

【问题标题】：Initializing MPI outside of main in java在java中的main之外初始化MPI
【发布时间】：2020-01-05 02:16:36
【问题描述】：

我试图在 java 中创建一个分布式 MPI 类，它将为我做一些计算。不幸的是， MPI.Init 似乎需要主类中的 argv,argc。有没有办法在这个类中初始化 MPI？

public class distributed {

    public distributed(int mat[][],int n,int m) throws MPIException {

        MPI.Init(argv); // issue is here,i dont have "argv" to initialize with,causing null pointer exceptions in variables like "myrank"

        final int myrank = MPI.COMM_WORLD.Rank();
        final int size = MPI.COMM_WORLD.Size();

        final int rows = n;
        final int rowChunk = (rows+size-1)/size;

        final int startRow = myrank *rowChunk;
        int endRow = (myrank+1)*rowChunk;

        int[] newRow = new int[m];
           }
}

【问题讨论】：

标签： java mpi mpj-express

【解决方案1】：

为什么不在 main 方法中初始化 myrank 和 size。然后将它们作为Distributed 类构造函数的参数传递？

public class Distributed {

    public Distributed(int mat[][],int n,int m, int myrank, int size) {
        // These two variables are now parameters of the constructor
        // final int myrank = MPI.COMM_WORLD.Rank();
        // final int size = MPI.COMM_WORLD.Size();

        final int rows = n;
        final int rowChunk = (rows+size-1)/size;

        final int startRow = myrank *rowChunk;
        int endRow = (myrank+1)*rowChunk;

        int[] newRow = new int[m];
    }

    public static void main (String [] args) {
        MPI.Init(args, args.length); 
        final int myrank = MPI.COMM_WORLD.Rank();
        final int size = MPI.COMM_WORLD.Size();

        Distributed d = new Distributed (..., myrank, size);
    }
}

【讨论】：