C：尺寸大于 1000 的二维数组相乘会导致分段错误

Question

我正在乘以二维数组并在初始化数组时使用动态分配（但我不知道实现是否正确）。我正在使用 CodeBlock16.0 编译我的代码。该程序运行适用于小于 200 的矩阵，但我希望此代码运行适用于大于 1000 的矩阵。

这是代码：

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

int main(){
    int **matriks1=NULL,**matriks2=NULL,**result=NULL, r1=0, c1=0, r2=0, c2=0, i, j, k;


    printf("Enter rows and column for first matrix: ");//input size for matrix 1
    scanf("%d %d", &r1, &c1);
    matriks1=(int **)malloc(r1*sizeof(int*));
    for(int i=0;i<r1;++i) matriks1[i]=(int*)malloc(c1*sizeof(int));
    result=(int**)calloc(r1,sizeof(int*));


    printf("Enter rows and column for second matrix: ");//input size for matrix 2
    scanf("%d %d",&r2, &c2);
    matriks2=(int **)malloc(r2*sizeof(int*));
    for(int i=0;i<r2;++i) matriks2[i]=(int*)malloc(c2*sizeof(int));
    for(int i=0;i<c2;++i) result[i]=(int*)calloc(c2,sizeof(int));
    srand(time(NULL));


    // Column of first matrix should be equal to column of second matrix and
    while (c1 != r2)
    {
        printf("Error! Kolom matriks pertama tidak sama dengan baris matriks kedua.\n\n");
        printf("Enter rows and column for first matrix: ");
        scanf("%d %d", &r1, &c1);
        printf("Enter rows and column for second matrix: ");
        scanf("%d %d",&r2, &c2);
    }

    // Storing elements of first matrix.
    printf("\nElements of matrix 1:\n");
    for(i=0; i<r1; ++i)
        for(j=0; j<c1; ++j){
            printf("Elements a%d%d: ",i+1, j+1);
            matriks1[i][j]=rand()%10;
            printf("%d ",matriks1[i][j]);
            //scanf("%d", &a[i][j]);
        }

    // Storing elements of second matrix.
    printf("\nElements of matrix 2:\n");
    for(i=0; i<r2; ++i)
        for(j=0; j<c2; ++j){
            printf("Enter elements b%d%d: ",i+1, j+1);
            matriks2[i][j]=rand()%10;
            printf("%d ",matriks2[i][j]);
    }

    // Initializing all elements of result matrix to 0
    for(i=0; i<r1; ++i)
        for(j=0; j<c2; ++j)
        {
            result[i][j] = 0;
        }

    // Multiplying matrices a and b and
    // storing result in result matrix
    for(i=0; i<r1; ++i)
        for(j=0; j<c2; ++j)
            for(k=0; k<c1; ++k)
            {
                result[i][j]+=matriks1[i][k]*matriks2[k][j];
            }

    // Displaying the result
    printf("\nOutput Matrix:\n");
    for(i=0; i<r1; ++i)
        for(j=0; j<c2; ++j)
        {
            printf("%d  ", result[i][j]);
            if(j == c2-1)
                printf("\n\n");
        }
    for(int i=0;i<r1;i++){
        free(matriks1[i]);
        free(matriks2[i]);
        free(result[i]);
    }
    free(matriks1);
    free(matriks2);
    free(result);
    return 0;
}

Answer 1

result = calloc(r1,sizeof(int*)); //<== `r1` count declared in array
//for(int i = 0; i<c2; ++i)  //<== remove
for(int i = 0; i < r1; ++i)  //<== should allocate up to `r1`
    result[i] = (int*)calloc(c2, sizeof(int));

for 循环显然是要计数到 r1，而不是 c2。你也不需要用 C 语言进行转换。

显然并非所有数组的大小都相同。根据大小释放数组，如下所示：

//for(int i=0;i<r1;i++){ <= remove
//    free(matriks1[i]);
//    free(matriks2[i]);
//    free(result[i]);
//}

for(int i = 0; i < r1; i++) free(matriks1[i]);
for(int i = 0; i < r2; i++) free(matriks2[i]);
for(int i = 0; i < r1; i++) free(result[i]);
free(matriks1);
free(matriks2);
free(result);

C：尺寸大于 1000 的二维数组相乘会导致分段错误

C: Multiplication of 2D arrays of sizes greater than 1000 results in a segmentation fault

c

matrix-multiplication

dynamic-allocation