/* matrix.c - Let's practice matrix operations.
 * The user supplies the number of rows/cols of a SQUARE matrix.
 * The program will generate random values for two n*n matrices.
 * We'll add and multiply them.
 * This is a only a serial implementation.
 */
#include <stdio.h>
#include <stdlib.h>
#include <time.h>


// Each number is printed in a field width of 4.
// Feel free to reduce this for larger arrays.
void print_array(int ** a, int size)
{
  int i, j;
  
  for (i = 0; i < size; ++i)
  {
    for (j = 0; j < size; ++j)
      printf("%4d", a[i][j]);
    printf("\n");
  }
  printf("\n");
}


main(int argc, char **argv)
{
  int n, **a, **b, **sum, **prod, i, j, k;
  
  if (argc != 2)
  {
    printf("You need to tell me the matrix size.\n");
    exit(1);
  }
  
  n = atoi(argv[1]);
  srand(time(NULL));
  
  // Initialize
  a = (int **) malloc (n * sizeof (int *));
  b = (int **) malloc (n * sizeof (int *));
  sum = (int **) malloc (n * sizeof (int *));
  prod = (int **) malloc (n * sizeof (int *));  
  for (i = 0; i < n; ++i)
  {
    a[i] = (int *) malloc (n * sizeof (int));
    b[i] = (int *) malloc (n * sizeof (int));
    sum[i] = (int *) malloc (n * sizeof (int));
    prod[i] = (int *) malloc (n * sizeof (int));
    for (j = 0; j < n; ++j)
    {
      a[i][j] = rand() % 4;
      b[i][j] = rand() % 4;
      // If desired, could also initialize sum and prod entries to zero.
    }
  }



  // Sum
  for (i = 0; i < n; ++i)
    for (j = 0; j < n; ++j)
      sum[i][j] = a[i][j] + b[i][j];
  
  // Product
  for (i = 0; i < n; ++i)
    for (j = 0; j < n; ++j)
    {
      prod[i][j] = 0;
      for (k = 0; k < n; ++k)
        prod[i][j] += a[i][k] * b[k][j];
    }
  
  // Output
  print_array(a, n);
  print_array(b, n);
  print_array(sum, n);
  print_array(prod, n);

  // De-allocate or free the memory!
  for (i = 0; i < n; ++i)
  {
    free(a[i]);
    free(b[i]);
    free(sum[i]);
    free(prod[i]);
  }
  free(a);
  free(b);
  free(sum);
  free(prod);
}

/* Example output:
   3   2   3
   3   1   0
   2   1   1

   1   2   2
   0   2   2
   0   3   0

   4   4   5
   3   3   2
   2   4   1

   3  19  10
   3   8   8
   2   9   6
*/