Accurate Solution of Symmetric Positive Semi-Definite Linear Systems by the FETI Method

David Day

Organization 9222 MS 1110 Sandia National Laboratories PO Box 5800 Albuquerque, NM 87185-5800


To solve a symmetric positive semi-definite (SPSD) linear system using the FETI method, it is necessary to first compute the null space and then deflate it out. In the FETI (or dual interface domain decomposition) formulation, the null space of a SPSD matrix can be determined from the null space of the reduced coarse grid operator. To accurately solve the original SPSD system, the null space of the reduced coarse grid operator must be computed accurately. In this talk a stable algorithm for computing the null space of the reduced operator using the Lanczos algorithm will be presented. The effectiveness of the new algorithm will be illustrated using several complex structures.