动态矩阵分配程序

Question

我正在学习C。我有一个程序，可以动态创建和填充两个矩阵X和Y，使用随机数使用rand（），如下所示

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

void main(){

 int i, j, k, m, n;
 double **x;
 double **y;
 printf("Enter a number as the size of two square matrices\n");
 scanf("%d", &m);
 x = (double**)malloc(m * sizeof(double));  
 y = (double**)malloc(m * sizeof(double));
 /* initialize random seed: */
 srand(time(NULL));
 for(i = 0; i < m; i++) {
    x[i] = (double*)malloc(m * sizeof(double));
    y[i] = (double*)malloc(m * sizeof(double));
    for(i = 0; i < m; i++) {
        for(j = 0; j < m; j++) {
            x[i][j] = rand();
            y[i][j] = rand();
        }
        printf("\n");
    }
  }
  printf("\n\n");
}

当我运行这个程序并给出2作为我的矩阵的大小时，我看到“分离故障”是错误。请注意，我们的想法是用双精度类型的随机元素填充两个矩阵。如果上面的代码是正确的，请告诉我。

更正：编辑1

 x = (double**)malloc(m * sizeof(double*)); 
 y = (double**)malloc(m * sizeof(double*));
 /* initialize random seed: */
 srand(time(NULL));
 for(i = 0; i < m; i++) {
    x[i] = (double*)malloc(m * sizeof(double));
    y[i] = (double*)malloc(m * sizeof(double));

    for(j = 0; j < m; j++) {
        x[i][j] = rand();
        y[i][j] = rand();
    }
    printf("\n");

  }
  printf("\n\n");
}

以上功能现在正常工作。需要解释x=（double**）malloc（m*sizeof（double*））；并且x[i]=（double*）malloc（m*sizeof（double））；

为什么*用于x=（双**）malloc（m*sizeof（双*））中的sizeof（双*）；

编辑2

void main(){

 int i, j, k, m, n; 
 printf("Enter a number as the size of two square matrices\n");
 scanf("%d", &m);

 double (*x)[m] = malloc(sizeof(double[m][m]));
 double (*y)[m] = malloc(sizeof(double[m][m]));
 /* initialize random seed: */
 srand(time(NULL));
 for(i = 0; i < m; i++) {
    for(j = 0; j < m; j++) {
        x[i][j] = rand();
        y[i][j] = rand();
    }
    printf("\n");

  }
  printf("\n\n");
}

根据Jens Gustedt矩阵分配更改…我已删除

 double **x;
 double **y;
 x = (double**)malloc(m * sizeof(double*)); 
 y = (double**)malloc(m * sizeof(double*));
 x[i] = (double*)malloc(m * sizeof(double));
 y[i] = (double*)malloc(m * sizeof(double));

Answer 1

这些只是假的矩阵，这项技术属于博物馆。在现代C语言中，从C99开始，只需将2D矩阵分配为double（*matrix）[m]=malloc（sizeof（double[m][m]） 。因此，只需对整个矩阵调用一次malloc，就可以将其全部存储在连续内存中
–Jens Gustedt