Question

我有一个与我的C / C ++代码相关的问题。我尝试了一些研究，但没有针对我的问题的具体答案。我希望你能尽快回答我的问题。

以下是我在C语言中的完整代码：

 #include <omp.h>
#include <stdio.h>
#include <stdlib.h>
#include <iostream>
using namespace std;
#define M 500
#define N 500
int
main ()
{
  //set number of threads here
  //omp_set_num_threads(8);
  int i, j, k;
  double sum;
  double **A, **B, **C;

  A = malloc (M * sizeof (double *));
  B = malloc (M * sizeof (double *));
  C = malloc (M * sizeof (double *));
  for (i = 0; i < M; i++)
    {
      A[i] = malloc (N * sizeof (double));
      B[i] = malloc (N * sizeof (double));
      C[i] = malloc (N * sizeof (double));
    }
  double start, end;
  for (i = 0; i < M; i++)
    {
      for (j = 0; j < N; j++)
        {
          A[i][j] = j * 1;
          B[i][j] = i * j + 2;
          C[i][j] = j - i * 2;
        }
    }
  start = omp_get_wtime ();
  for (i = 0; i < M; i++)
    {
      for (j = 0; j < N; j++)
        {
          sum = 0;
          for (k = 0; k < M; k++)
            {

              sum += A[i][k] * B[k][j];
            }
          C[i][j] = sum;
        }
    }

  end = omp_get_wtime ();
  printf ("Time of computation: %f\n", end - start);

  cin.get ();
  return 0;
}

由于一些错误，代码终止。代码的结果在这里给出：

error C4700: uninitialized local variable 'A' used

error C4700: uninitialized local variable 'B' used

error C4700: uninitialized local variable 'C' used

请考虑我的问题：）

最诚挚的问候。

Answer 1

malloc（）返回一个void指针，你必须强制转换它：

  A = (double**) malloc (M * sizeof (double *));
  B = (double**) malloc (M * sizeof (double *));
  C = (double**) malloc (M * sizeof (double *));
  for (i = 0; i < M; i++)
    {
      A[i] = (double*) malloc (N * sizeof (double));
      B[i] = (double*) malloc (N * sizeof (double));
      C[i] = (double*) malloc (N * sizeof (double));
    }

如果您使用的是c ++，最好使用“new”而不是malloc：

  A = new double* [M];
  B = new double* [M];
  C = new double* [M];
  for (i = 0; i < M; i++)
    {
      A[i] = new double[N];
      B[i] = new double[N];
      C[i] = new double[N];
    }

错误C4700：未初始化的局部变量＆＃39; A＆＃39;用过的

1 个答案: