MPI学习二

1.规约

int MPI_Reduce(void * input_data_p, void * output_data_p, int count, MPI_Datatype datatype, MPI_Op operator, int dest_process, MPI_Comm comm)

#include <stdio.h>
#include <mpi.h>

int main(int argc, char **argv)
{
    int myid, numprocs;
    double local_num = 3.0; 

    MPI_Init(&argc, &argv);
    
    MPI_Comm_rank(MPI_COMM_WORLD, &myid);
    MPI_Comm_size(MPI_COMM_WORLD, &numprocs);
    
    double global_num;
    
    //your code here
    MPI_Reduce(&local_num, &global_num, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD);
    //end of your code
    
    if(myid == 0) {
        printf("Total sum = %f, avg = %f
", global_num, global_num / numprocs);
    }

    MPI_Finalize();
    return 0;
}

2.广播

int MPI_Bcast(void* buffer, int count, MPI_Datatype datatype, int source, MPI_Comm comm)

#include<stdio.h>
#include<mpi.h>

int main(int argc, char **argv)
{
    int myid, numprocs;
    int source = 0;
    int array[5]={1,2,3,4,5};
    int i;
    
    MPI_Init(&argc, &argv);
    
    MPI_Comm_rank(MPI_COMM_WORLD, &myid);
    MPI_Comm_size(MPI_COMM_WORLD, &numprocs);
    
    if(myid == source) {
        for(i = 1; i <= 5; i++)
            array[i] = i;
    }
    
    //your code here
    MPI_Bcast(array, 5, MPI_INT, source, MPI_COMM_WORLD);
    //end of your code
    
    if(myid != source) {
        printf("In process %d, ", myid);
        for(i = 0; i < 5; i++)
            printf("arr[%d]=%d	", i, array[i]);
        printf("
");
    }

    MPI_Finalize();
    return 0;
}

来自：MPI编程实训学习（超算习堂）