#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/time.h>

struct timeval t1, t2;

void  naive_mm(int size, double *a, double *b, double *c) 
{
  int i, j, k;
    for (i=0; i<size; i++)
      for (j=0; j < size; j++)
        for (k=0; k<size; k++) {
          *(c+i*size + j) = *(c+i*size + j) + *(a+i*size + k) *  *(b +k*size + j);
	}
}


int
main( int argc, char *argv[])
{
  double *A, *B, *C, *W, *Z, *WORK;
  int  N, M, i;

  if (argc != 3) {
    printf("Usage: a.out matrix_size iter\n");
    exit(0);
  }

  N= atoi(argv[1]);
  M = atoi(argv[2]);

  srand48(100);

  A = malloc(N*N*sizeof(double));
  B = malloc(N*N*sizeof(double));
  C = malloc(N*N*sizeof(double));
  for (i=0; i<N*N; ++i) {
    A[i] = drand48();
    B[i] = drand48();
  }

  
  gettimeofday(&t1, NULL);
  for (i=0; i<M; i++) {
    naive_mm(N, B, A, C);
  }
  gettimeofday(&t2, NULL);

  printf("Time for the matrix multiplication is %d milliseconds\n",
         (t2.tv_sec - t1.tv_sec)*1000 + 
         (t2.tv_usec - t1.tv_usec) / 1000);

#ifdef CHECK
 {
   FILE *fd;
   if ((fd = fopen("tmp333", "w")) == NULL) {
     printf("Cannot open tmp333\n"); exit(0);
   }
   
   for (i=0; i<N*N; i++)
     fprintf(fd, "%6.2lf\n", C[i]);
   fclose(fd);
 }
#endif
  
  return 0;
}