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我对 MPI 的东西真的很陌生。我只需要完成我的大学任务。有人可以帮助我吗？

任务是在 N*M 矩阵中找到最小值和最大值。进程计数必须等于 N。我尝试使用最小值和最大值来查找，MPI_Reduce但我得到错误结果。这是我的代码。

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

const int n = 5;
const int m = 4;

void fill_matrix_randomly(int matrix[n][m], int max_value);
void write_matrix(int matrix[n][m]);
int find_max(int* vector, int vector_size);
int find_min(int* vector, int vector_size);
void write_vector(int* vector, int vector_size);

int main(int argc, char* argv[])
{
    int my_rank = 0;
    int comm_size = 0;

    int a[n][m];
    int receive_buffer[m];
    int partial_max[m];
    int partial_min[m];

    MPI_Init(&argc, &argv);

    MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);
    MPI_Comm_size(MPI_COMM_WORLD, &comm_size);

    if (comm_size != n)
    {
        printf("Please set process count = %d and run again.", n);
        MPI_Finalize();
        return 0;
    }

    if (my_rank == 0)
    {
        fill_matrix_randomly(a, 10);
        write_matrix(a);    
    }
    /* MPI Scatter(address of send buffer, number of elements sent to each process, data type of send buffer, address of receive buffer, number of elements in receive buffer, data type of receive buffer, rank of sending process, communicators space) */
    MPI_Scatter(a, n, MPI_INT, receive_buffer, n, MPI_INT, 0, MPI_COMM_WORLD);
    /* MPI_Reduce(address of send buffer, address of receive buffer, number of elements in send buffer, data type of elements in send buffer, reduce operation, rank of root process, communicators space) */
    MPI_Reduce(receive_buffer, partial_max, n, MPI_INT, MPI_MAX, 0, MPI_COMM_WORLD);
    MPI_Reduce(receive_buffer, partial_min, n, MPI_INT, MPI_MIN, 0, MPI_COMM_WORLD);
    if (my_rank == 0)
    {
        printf("Vector of partial max values.\n");
        write_vector(partial_max, n);
        printf("Vector of partial min values.\n");
        write_vector(partial_min, n);

        int max = find_max(partial_max, n);
        int min = find_min(partial_min, n);
        printf("Matrix boundaries = [%d..%d]\n", min, max);
    }
    MPI_Barrier(MPI_COMM_WORLD);
    MPI_Finalize();

    return 0;
}

int find_max(int* vector, int vector_size)
{
    int max = vector[0];
    int i = 0;  
    for (i = 0; i < vector_size; i++)
    {
        if (vector[i] > max)
        {
            max = vector[i];
        }       
    }
    return max;
}

int find_min(int* vector, int vector_size)
{
    int min = vector[0];
    int i = 0;
    for (i = 0; i < vector_size; i++)
    {
        if (vector[i] < min)
        {
            min = vector[i];
        }
    }
    return min;
}

void fill_matrix_randomly(int matrix[n][m], int max_value)
{
    int i = 0;
    int j = 0; 
    srand(time(NULL));
    for (i = 0; i < n; i++)
    {
        for (j = 0; j < m; j++)
        {
            matrix[i][j] = rand() % max_value;
        }
    }   
}

void write_matrix(int matrix[n][m])
{
    int i = 0;
    int j = 0;
    for (i = 0; i < n; i++)
    {
        for (j = 0; j < m; j++)
        {
            printf("%4d", matrix[i][j]);            
        }
        printf("\n");
    }
}

void write_vector(int* vector, int vector_size)
{
    int i = 0;
    for (i = 0; i < vector_size; i++)
    {
        printf("vector[%d] = %d\n", i, vector[i]);
    }
}

这是输出。

$ mpiexec -n 5 ./main
   8   1   3   9
   1   0   3   1
   4   9   5   5
   1   7   4   9
   8   5   7   4
Vector of partial max values.
vector[0] = 9
vector[1] = 8
vector[2] = 5
vector[3] = 9
vector[4] = 16
Vector of partial min values.
vector[0] = -1
vector[1] = -1
vector[2] = -1
vector[3] = -1
vector[4] = 1
Matrix boundaries = [-1..16]

我哪里错了？我应该改变什么？我整天都在寻找解决方案。

4

1 回答 1

2

您的矩阵是n逐m列的。当您将此矩阵分配给n进程时，每个进程都必须处理m元素，但您n在所有向量调用中使用计数。你应该传递一个长度m：

  • MPI_Scatter通话；
  • 两个MPI_Reduce电话；
  • 两个write_vector电话；
  • 和find_max调用find_min。

请注意，您已正确地将,receive_buffer声明为元素。partial_maxpartial_minm

于 2012-12-13T15:54:13.483 回答