Direct preconditioners

Dear NGSolve community,

up until now, I have been preconditioning my iterative solvers mainly with
BDDC and Block GS methods and wonder, whether there is an ILU directly available in NGSolve.
(I know, I could possibly use PETSc for this.)
I have read about the “direct preconditioner” in your tutorial, but reading the C++ code I cannot
see that, e.g., PARDISO is configured differently as preconditioner than being employed as
direct solver.
Did I miss something or means using a “direct preconditioner” that a direct solver is employed and
I refine the result afterwards with an iterative method, or are the direct solvers providing an ILU?

Best regards,

Hi Philipp,

There is no ILU directly in NGSolve. As you said, your best option is probably to use PETSc.

The “direct preconditioner” is the exact inverse, it is just packaged into a “preconditioner” so you can switch between direct solvers and preconditioners

Best, Lukas

Thanks for the clarification!