Design a program to implement ping-ping.

#include<stdio.h>
#include"mpi.h"
int main(int argc, char **argv)
{
    MPI_Comm comm = MPI_COMM_WORLD;
    int size, rank, num = 0;
    MPI_Status status;
    MPI_Init(&argc,&argv);
    MPI_Comm_size(comm,&size);
    MPI_Comm_rank(comm,&rank);
    while(num < 9)
    {
        if(rank == 0)
        {
            if(num == 0)
            {
                MPI_Send(&num,1,MPI_INT,1,99,comm);
                printf("Process 0 send %d to process 1.\n",num);
            }
            MPI_Recv(&num,1,MPI_INT,1,99,comm,&status);
            num += 1;
            MPI_Send(&num,1,MPI_INT,1,99,comm);
            printf("Process 0 send %d to process 1.\n",num);
        }
        else if (rank == 1)
        {
            MPI_Recv(&num,1,MPI_INT,0,99,comm,&status);
            num += 1;
            MPI_Send(&num,1,MPI_INT,0,99,comm);
            printf("Process 1 send %d to process 0.\n",num);
        }
    }
    MPI_Finalize();
    return 0;
}

注意send和recv函数第一个参数都是地址！！！