MPI 学习

一、编译MPI

mpic++ test.cc -o test

二、启动MPI

mpiexec -np 10 ./test

三、几个例子

第一个进程向第二个发一个数，第二个进程向第三个进程发送一个数。。。依次传递

#include "mpi.h"
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#include <iostream>
#include <unistd.h>


using namespace std;

int main(int argc, char **argv)
{
    int myid, numprocs, num;

    MPI_Init(&argc, &argv);
    MPI_Comm_rank(MPI_COMM_WORLD, &myid);
    MPI_Comm_size(MPI_COMM_WORLD, &numprocs);
    MPI_Status status;

    if (numprocs < 2) {
        printf("Processes must >= 2! 
");
        MPI_Abort(MPI_COMM_WORLD, 99);
    }

    do {
        //master
        if (myid == 0) {
            cout << "please input a number" << endl;
            cin >> num;
            //send number
            if (numprocs > 1) {
                MPI_Send(&num, 1, MPI_INT, myid + 1, 0, MPI_COMM_WORLD);
                cout << myid << " send " << num << " to " << myid + 1 << endl;
            }
        }
        //slave
        else {
            MPI_Recv(&num, 1, MPI_INT, myid - 1, 0, MPI_COMM_WORLD, &status);
            cout << myid << " receive " << num << " from " << myid - 1 << endl;
            if (myid < numprocs - 1) {
                MPI_Send(&num, 1, MPI_INT, myid + 1, 0, MPI_COMM_WORLD);
                cout << myid << " send " << num << " to " << myid + 1 << endl;
            }
        }
        MPI_Barrier(MPI_COMM_WORLD); // wait all pro finish
    } while (num > 0);

    MPI_Finalize();

    return 0;
}

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