matrixmultiplication.c

/*tHIS CODE MULTIPLY TWO MATRICES which are dymamiclly allocated AND PRINT THE OUTPUT*/
/*All matrices are dynamically allocated*/
/*Let there are 2 matrices mat1 of n1 * m1 & mat2 of n2 * m2. then for matrix to be multiplied m1 should be
equal to n2 (m1 == n2). After multiplication the product matrix will be of n1 * m2 type.*/

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

void display(int *mat,int row, int column);
int * multiply_matrix(int *mat1,int row1,int col1,int *mat2,int row2, int col2);


//taking all these as global variable because each function will use it

int main()
{   int *mat1, *mat2, *mat3;
    int n1,n2,m1,m2,i;
    srand(time(0));
    printf("Enter value of 'n' & 'm' for the first matrix (n * m):  ");
    scanf("%d %d",&n1,&m1);
    printf("Enter value of 'n' & 'm' for the second matrix (n * m):  ");
    scanf("%d %d",&n2,&m2);

    /*Dyanamically allocating memeory for both matrices*/
    mat1 = calloc(n1*m1, sizeof(int));
    mat2 = calloc(n2*m2,sizeof(int));
    /*Dynamically allocating memory for product matrix*/

    /*randomly generating first matrix*/
    for(i=0;i<n1*m1;i++)
        mat1[i] = rand()%9 + 1;//generating number between 1 to 9
    /*Randomly generating the second matrix*/
    for(i=0;i<n2*m2;i++)
        mat2[i] = rand()%9 + 1;

    /*multliplying both matrices*/
    mat3 = multiply_matrix(mat1,n1,m1,mat2,n2,m2);
     /*Displaying both the matrices*/
    display(mat1,n1,m1);
    display(mat2,n2,m2);
    /*displaying the product matrix*/
    display(mat3,n1,m2);

free(mat1);
free(mat2);
free(mat3);





return 0;
}//main

void display(int *mat,int row, int column)
    {   int i,j;

        for(i=0;i<row;i++)
            {
                for(j=0;j<column;j++)
                    printf("%-4d ",mat[i*column + j]);
                printf("\n");

            }
        printf("\n\n");

    }//display

int* multiply_matrix(int *mat1,int row1,int col1,int *mat2,int row2, int col2)
{   int i,j,k;
    int *prod;
    /*dynamically allocating the product matrix*/
    prod = calloc(row1 * col2, sizeof(int));
    /*Checking multiplication constrants*/
    if(col1 != row2)
       {
           printf("\nThese matrix can not be multiplied: ");
           exit(1);
       }
    for(i=0;i<row1;i++)
        {   for(j=0;j<col2;j++)
                {
                    for(k=0;k<row2;k++)
                        {   prod[i * col2 + j] = prod[i * col2 + j] + mat1[i * col1 + k] * mat2[k * col2 + j];/*quite tricky pay attention to it*/
                              //printf("%d ",prod[i * col2 + j]);
                        }
                }
        }
return prod;
}//end of multiply matrix