Syntax

   [a, aa, L, U] = schur_nflu(a, b, L, U, A12, A21, A22, varargin)

Description

   Performs a Schur complements with non fixed LU decomposition.

Inputs (required)

   a   = previous solution of the augmented problem.
   b   = independent vector of the system.
   L   = lower triangular factor from LU factorization of A.
   U   = upper triangular factor from LU factorization of A.
   A12 = right-upper block for augmented matrix.
   A21 = left-lower block for augmented matrix.
   A22 = right-lower block for augmented matrix.

Input (optional)

   precond = use precond or not ('no', 'ilu', 'diag').
             for 'ndiad' define: 'numbd' (number of diagonals);
             for 'ilu' define: 'milu', 'typeilu', 'droptol', 
                               'thresh' and 'udiag'.

Output

   a   = solution of the augmented problem.
   aa  = coefficients of the error estimation.
   L   = augmented matrix lower triangular factor.
   U   = augmented matrix upper triangular factor.

See also

  schur_luinc, schur_luinc2 and schur_iter.