
 


   n=1000;
   A = randn(n);
   x = randn(n,1);
   t = cputime;
   b1 = A*x;
   time1 = cputime - t
   for i = 1:n 
     b2(i,1) = 0;
     for j = 1:n
       b2(i,1) = b2(i,1) + A(i,j)*x(j,1);
     end
   end
   time2 = cputime - time1
  
