A1 matrix for testing A=LU-decomposition
  3
  4.0001   1.0000   2.0000 
 10.0000  -0.1000   3.0000
  5.0000   3.0000   1.0000
  4.0001  12.8000  12.0000


Output matrices L and U are stored in the input matrix A 
    4.0001    1.0000    2.0000
    2.4999   -2.5999   -1.9999
    1.2500   -0.6731   -2.8461

Matrices L, U for A=LU in [L U P=I]=lu(A)