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


void MatrixMult(int *A, int *B, int *C, int n) {

   for (int i = 0 ; i < n ; i++) {
      for (int j = 0 ; j < n ; j++) {
         int sum = 0 ;
         for (int k = 0 ; k < n ; k++) {
            sum += A[i*n+k] * B[k*n+j] ; 
         }
         C[i*n+j] = sum ;
      }
   }
}



int main() {
   int n = 1000  ;
   int *A = new int[n*n] ;
   int *B = new int[n*n] ;
   int *C = new int[n*n] ;

   struct timeval tp;
   gettimeofday(&tp, NULL);
   long int ms = tp.tv_sec * 1000 + tp.tv_usec / 1000;
   printf("Random seed set to: %ld\n\n", ms) ;
   srand(ms) ;   // other uses

   for (int i=0 ; i < n*n ; i++) {
     A[i] = rand()%100 + 1 ;
     B[i] = rand()%100 + 1 ;
   }

   gettimeofday(&tp, NULL);
   double beginTime = tp.tv_sec * 1000.0 + tp.tv_usec / 1000.0;
   printf("Start time = %lf ms\n\n", beginTime) ;

   MatrixMult(A,B,C,n) ;

   gettimeofday(&tp, NULL);
   double endTime = tp.tv_sec * 1000.0 + tp.tv_usec / 1000.0;
   printf("Start time = %lf ms\n", endTime) ;
   printf("Elapsed time = %lf ms\n", endTime - beginTime) ;
 
/*
   for (int i=0 ; i < n ; i++) {
      for (int j=0 ; j < n ; j++) {
         printf("%3d", A[i*n+j]) ;
      }
      printf("   ") ;
      for (int j=0 ; j < n ; j++) {
         printf("%3d", B[i*n+j]) ;
      }
      printf("   ") ;
      for (int j=0 ; j < n ; j++) {
         printf("%3d ", C[i*n+j]) ;
      }
      printf("\n") ;
   }
*/

   delete [] A ;
   delete [] B ;
   delete [] C ;

   return 0 ;
}