matrix multiplication using malloc without user input - matrix

Question

I am trying to use Malloc function to dynamically allocate memory but I also want to specify my data entry for operation rather than taking the user input.
I have found this code here which works fine, but I am working with a large data set and taking user input is not an option, so I want to keep using MALLOC but also define the data set.
like instead of following,
//Input Matrix1
for (i = 0; i < r1; i++)
for (j = 0; j < c1; j++)
scanf_s("%d", &mat1[i][j]);
I want something like
//mat1[2][2] = { {1,2},{2,3} }
to be inputed in the code
What would be the way to do it? I would really appreciate some advice. Thanks
#include<stdio.h>
#include<stdlib.h>
int main() {
int **mat1, **mat2, **res, i, j,k, r1, c1, r2, c2;
printf("\nEnter the Order of the First matrix...\n");
scanf_s("%d %d", &r1, &c1);
printf("\nEnter the Order of the Second matrix...\n");
scanf_s("%d %d", &r2, &c2);
if (c1 != r2) {
printf("Invalid Order of matrix");
exit(EXIT_SUCCESS);
}
mat1 = (int**)malloc(r1 * sizeof(int*));
for (i = 0; i < c1; i++)
mat1[i] = (int*)malloc(c1 * sizeof(int));
mat2 = (int**)malloc(r2 * sizeof(int*));
for (i = 0; i < c2; i++)
mat2[i] = (int*)malloc(c2 * sizeof(int));
res = (int**)calloc(r1, sizeof(int*));
for (i = 0; i < c2; i++)
res[i] = (int*)calloc(c2, sizeof(int));
/**/
//Input Matrix1
for (i = 0; i < r1; i++)
for (j = 0; j < c1; j++)
scanf_s("%d", &mat1[i][j]);
//Input Matrix2
for (i = 0; i < r2; i++)
for (j = 0; j < c2; j++)
scanf_s("%d", &mat2[i][j]);
//Printing Input Matrix 1 and 2
printf("\n Entered Matrix 1: \n");
for (i = 0; i < r1; i++) {
for (j = 0; j < c1; j++)
printf("%d ", mat1[i][j]);
printf("\n");
}
printf("\n Entered Matrix 2: \n");
for (i = 0; i < r2; i++) {
for (j = 0; j < c2; j++)
printf("%d ", mat2[i][j]);
printf("\n");
}
//int mat1[2][2] = { {1,2},{2,3} };
//int mat2[2][2] = { {1,3},{2,4} };
//Computation
//Multiplication
for (i = 0; i < r1; i++) {
for (j = 0; j < c2; j++) {
res[i][j] = 0;
for (k = 0; k < c1; k++)
res[i][j] += mat1[i][k] * mat2[k][j];
}
printf("\n");
}
printf("\nThe Multiplication of two matrix is\n");
for (i = 0; i < r1; i++) {
printf("\n");
for (j = 0; j < c2; j++)
printf("%d\t", res[i][j]);
}
printf("\n");
/* Addition
for(i=0;i<r1;i++)
for(j=0;j<c2;j++)
res[i][j]=mat1[i][j]+mat2[i][j];
printf("\nThe Addition of two matrix is\n");
for(i=0;i<r1;i++){
printf("\n");
for(j=0;j<c2;j++)
printf("%d\t",res[i][j]);
}
*/
return 0;
}

Answer 1

Please specify the format of your input data. Is it a csv file?
You can only specify data in the format int b[4] = {1, 2, 3, 4} when the size of b is fixed, i.e. known at compile time. But if all you matrices are known at compile time anyway, why bother doing dynamic allocation?
Also I cleaned up your code a bit:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define index(x, y, r) (x+r*y)
struct matrix {
int cols;
int rows;
double * data;
};
void print_mat(struct matrix * mat) {
int i, j;
for (i = 0; i < mat->rows; i++) {
for (j = 0; j < mat->cols; j++) {
printf("%f \t", mat->data[index(i, j, mat->rows)]);
}
printf("\n");
}
}
int mat_alloc(struct matrix *mat) {
mat->data = (double*)malloc(mat->rows*mat->cols*sizeof(double));
}
int read_mat(struct matrix *mat) {
int i, j;
for (i = 0; i < mat->rows; i++) {
for (j = 0; j < mat->cols; j++) {
scanf("%lf", &(mat->data[index(i, j, mat->rows)]));
}
}
}
int multiply(struct matrix * a, struct matrix * b, struct matrix * res) {
if(a->cols != b->rows){
printf("Matrix dimensions do not match!\n");
return 0;
}
res->rows = a->rows;
res->cols = b->cols;
mat_alloc(res);
memset(res->data, 0, res->cols*res->rows*sizeof(double));
int i, j, k;
for (i = 0; i < res->rows; i++) {
for (j = 0; j < res->cols; j++) {
for (k = 0; k < a->cols; k++) {
res->data[index(i, j, res->rows)] += a->data[index(i, k, a->rows)] * b->data[index(k, j, b->rows)];
}
}
}
}
int main() {
struct matrix mat1, mat2, res;
printf("\nEnter the Order of the First matrix...\n");
scanf("%d %d", &mat1.rows, &mat1.cols);
printf("\nEnter the Order of the Second matrix...\n");
scanf("%d %d", &mat2.rows, &mat2.cols);
mat_alloc(&mat1);
mat_alloc(&mat2);
read_mat(&mat1);
read_mat(&mat2);
printf("Scanned matrices: \n");
print_mat(&mat1);
printf("\n");
print_mat(&mat2);
printf("\n");
multiply(&mat1, &mat2, &res);
printf("Calculated result: \n");
print_mat(&res);
return 0;
}