(Created 2011-09-01.)

MULTIGRID METHODS FOR DIFFERENTIAL EQUATIONS | FMNN15 |

**Aim**

Many important phenomena in science and engineering are described by partial differential equations. When these equations are solved numerically one uses discretization methods, which give rise to (often enormously) large systems of equations. It is not unusual that these systems have several million unknowns. Due to the size of the systems it is necessary to use iterative methods, with multigrid methods belonging to the most efficient techniques.

The course builds directly on FMNN10 Numerical Solution of Differential Equations, and is focused on multigrid methods for elliptic equations. The aim is to give an elementary introduction to multigrid, starting from the self-adjoint two-point boundary value problems studied in FMNN10. Then the technique is applied to more general elliptic equations, and different variants such as V- and W-iterations are used.

*Knowledge and understanding*

For a passing grade the student must

- understand the ideas behind different variants of multigrid, such as V- and W-iterations.

- have a basic understanding of the convergence of multigrid methods.

*Skills and abilities*

For a passing grade the student must

- be able to interpret the convergence of multigrid iterations in practice and assess the results.

- be able to solve simple elliptic applied problems with a multigrid method.

*Judgement and approach*

For a passing grade the student must

**Contents**

- Convergence of linear iterations in relation to the spectral properties of the differential or difference operator.
- Multigrid iteration, V cycles, W cycles.
- Poisson's equation with multigrid, preconditioning.

**Literature**

Briggs, W.L. A Multigrid tutorial, 2nd ed. SIAM 2000. ISBN 978-0898714623.

Supplementary material from the department.