Question

我正在尝试使用 MPI 集体通信 MPI_Scatter 和 MPI_Gather 在C语言中将两个矩阵相乘。 / p>

我的代码以正确的结果执行，但是当我在MPI_Scatter之后测试进程时，我在每个进程上得到零。

因此，我认为 MPI_Scatter 和 MPI_Gather 中的 sendcount 和 recevecount 参数存在问题功能。

感谢您的帮助：）

// matrix multiplication using MPI_Scatter/MPI_Gather

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

#define N 10

int main(int argc, char *argv[])
{
  int a[N][N], b[N][N], c[N][N], r1, c1, r2, c2, i, j, k, rank, size;


  MPI_Init (&argc, &argv);
  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
  MPI_Comm_size(MPI_COMM_WORLD, &size);

  // min number of processes must be 2
  if(size < 2){
    fprintf(stderr, "Number of processes must be min 2 for %s\n", argv[0]);
    MPI_Abort(MPI_COMM_WORLD, 1);
  }

  // if rank of process is zero, initialize matrix a and b
  if(rank == 0){
    printf("Insert number of rows and columns for matrix a: ");
    scanf("%d %d", &r1, &c1);

    printf("Insert number of rows and columns for matrix b: ");
    scanf("%d %d",&r2, &c2);

    // If the number of columns of matrix a isn't equal to the number of rows of matrix b
    // ask user to insert again number of rows and columns
    while (c1!=r2){
      printf("Error! number of columns of matrix a isn't equal to number of rows of matrix b\n\n");

      printf("Enter rows and column for matrix a: ");
      scanf("%d %d", &r1, &c1);

      printf("Enter rows and column for matrix b: ");
      scanf("%d %d",&r2, &c2);
    }

    // Enter elements of matrix a
    printf("\nEnter elements of matrix a:\n");
    for(i = 0; i < r1; ++i){
      for(j = 0; j < c1; ++j){
        printf("Enter elements of matrix a%d%d: ",i+1, j+1);
        scanf("%d", &a[i][j]);
      }
    }

    // Enter elements of matrix b
    printf("\nEnter elements of matrix b:\n");
    for(i = 0; i < r2; ++i){
      for(j = 0; j < c2; ++j){
        printf("Enter elements of matrix b%d%d: ",i+1, j+1);
        scanf("%d",&b[i][j]);
      }
    }
  }

  // send one row of matrix a to every process in the group    
  MPI_Scatter(a, N*N/size, MPI_INT, a, N*N/size, MPI_INT, 0, MPI_COMM_WORLD);

  MPI_Bcast(b, N*N, MPI_INT, 0, MPI_COMM_WORLD);

  for(i=0; i<r1; ++i){
    for(j=0; j<c2; ++j){
      // initialization of matrix c(result matrix)
        c[i][j]=0;
        for(k=0; k<c1; ++k)
          c[i][j]+= a[i][k]*b[k][j]; // multiplication of matrix a and matrix b, save result in matrix c
    }
  }

  MPI_Gather(c, N*N/size, MPI_INT, c, N*N/size, MPI_INT, 0, MPI_COMM_WORLD);

  // print result
  if(rank == 0){
    printf("\nResult of matrix multiplication:\n");
    for(i = 0; i < r1; ++i){
      for(j = 0; j < c2; ++j){
          printf("%d ", c[i][j]);
        if(j == c2-1){
          printf("\n\n");
        }
        }
    }
  }

  MPI_Finalize();
}

如何使用MPI_Scatter / MPI_Gather将MPI中的两个矩阵相乘

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