FWF Project P19170-N18

Runtime: 01.02.2007-31.01.2010

- Johannes Kraus (project leader)
- Erwin Karer

This project is concerned with Algebraic Multigrid (AMG) methods for the solution of large-scale systems of linear algebraic equations arising from finite element (FE) discretization of (systems of) elliptic partial differential equations (PDEs). In particular, we address differential operators with a large (near) nullspace.

Our general objectives are the design, analysis and implementation of new AMG and Algebraic Multilevel (AML) preconditioners that enable an efficient solution of direct field problems in this category: the main emphasis is on problems arising from the discretization of Maxwell's equations, solid and structural mechanical problems with bad parameters, and problems arising in computational fluid dynamics.

The research plan comprises the following components:

- Investigation of element-based AMG and AML methods regarding non-conforming FE and Discontinuous Galerkin (DG) discretizations.
- Development of element-, face-, and edge-based strategies for the generation of adequate coarse-grid problems.
- AMG for non-symmetric and indefinite matrices: Application to (scalar) convection-diffusion, Stokes, and Oseen equations.
- AMG for non-M matrices: Application to Maxwell's equations and elasticity problems.
- Implementation of algorithms: Development of a linear solver package (in C/C++).

The main purpose of this project is to contribute in filling the gap between symmetric and positive definite (SPD) M-matrices and general SPD matrices, and, what is even more challenging, between general SPD matrices and non-symmetric and/or indefinite matrices. Besides the investigation of new classes of linear solvers it is also planned to develop a powerful tool kit that can be integrated in other research and commercial software packages as an essential part of the solver kernel.

- Algebraic Multigrid
- Multilevel Methods
- Partial Differential Equations
- Finite Element discretization
- Preconditioning
- Linear Solvers

- E. Karer, J. Kraus: Algebraic multigrid for finite element elasticity equations: Determination of nodal dependence via edge matrices and two-level convergence, Int. J. Numer. Meth. Engng. 83, 642-670, 2012.
- B. Ayuso, I. Georgiev, J. Kraus, L. Zikatanov: A simple preconditioner for the SIPG discretization of linear elasticity equations. In I. Dimov, S. Dimova, and N. Kolkovska (Eds.): NMA 2010, LNCS, 6046, 353-360, Springer, 2011.
- J. Kraus, S. Tomar: Algebraic multilevel iteration method for lowest order Raviart-Thomas space and applications. Int. J. Numer. Meth. Engng. 86, 1175-1196, 2011.
- I. Georgiev, J. Kraus, S. Margenov: Multilevel preconditioning of rotated trilinear non-conforming finite element problems. In I. Lirkov, S. Margenov, and J. Wasniewski (Eds.): LSSC 2009, LNCS, 5910, 100-107, Springer, 2010.
- I. Georgiev, J. Kraus, S. Margenov, J. Schicho: Locally optimized MIC(0) preconditioning of Rannacher-Turek FEM systems, Appl. Numer. Math. 59, 2402-2415, 2009.
- I. Georgiev, J. Kraus, S. Margenov: Multilevel preconditioning of rotated trilinear non-conforming finite element problems. In I. Lirkov, S. Margenov, and J. Wasniewski (Eds.): LSSC 2007, LNCS, 4818, 86-95, Springer, 2008.

- E. Karer, Subspace Correction Methods for Linear Elasticity, PhD Thesis, Linz, November, 2011

- J. Kraus and S. Margenov: Robust Algebraic Multilevel Methods and Algorithms. Radon Series Comp. Appl. Math., vol. 5, Walter de Gruyter, Berlin/NewYork, 2009.
- J. Kraus: Algebraic multilevel methods for solving elliptic finite element equations with symmetric positive definite matrices. Habilitation thesis, Johannes Kepler University, 2008.
- J. Kraus and S. Margenov: Multilevel methods for anisotropic elliptic problems. In Lectures on Advanced Computational Methods in Mechanics, Radon Series Comp. Appl. Math., vol. 1, J. Kraus and U. Langer eds., pp. 47-88, 2007.