%  TestHW3.m
%
%  Test code for M441 Homework assignment 3.

%  Generate subdiagonal, main diagonal, and superdiagonal of n X n 
%  tridiagonal matrix A

  n = 5;
  Adiag = 2*ones(n,1);  %  2 on main diagonal
  Asub = -ones(n-1,1);  %  -1 on subdiagonal
  Asuper = Asub;        %  A is symmetric. -1 on superdiagonal.



  [Lsub,Udiag,Usuper] = trilu_decomp(Asub,Adiag,Asuper);

%  Display correponding matrices L and U.

  L = eye(n) + diag(Lsub,-1)
  U = diag(Udiag,0) + diag(Usuper,1)
  A = L*U

%  Now test your code.

  b = ones(n,1);  %  Generate n X 1 vector of 1s.
  x = trilu_solve(Lsub,Udiag,Usuper,b)

  %  Compute residual. If code is correct, residual should be nearly zero.

  r = b - A*x