Nonsymmetric and highly indefinite linear systems can be quite difficult to solve by iterative methods. This paper combines ideas from the multilevel Schur low rank preconditioner developed by Y. Xi, R. Li, and Y. Saad [SIAM J. Matrix Anal., 37 (2016), pp. 235–259] with classic block preconditioning strategies in order to handle this case. The method to be described generates a tree structure T that represents a hierarchical decomposition of the original matrix. This decomposition gives rise to a block structured matrix at each level of T . An approximate inverse of the original matrix based on its block LU factorization is computed at each level via a low rank property that characterizes the difference between the inverses of the Schur complement and another block of the reordered matrix. The low rank correction matrix is computed by several steps of the Arnoldi process. Numerical results illustrate the robustness of the proposed preconditioner with respect to indefiniteness for a few discretized partial differential equations and publicly available test problems.
Bibliographical noteFunding Information:
This work was supported by NSF under grant DMS-1521573 and by the Minnesota Supercomputing Institute. The authors would like to thank the Minnesota Supercomputing Institute for the use of their extensive computing resources and the anonymous referees for their careful reading of this paper and helpful suggestions.
∗Submitted to the journal’s Methods and Algorithms for Scientific Computing section August 14, 2017; accepted for publication (in revised form) April 3, 2018; published electronically July 17, 2018. http://www.siam.org/journals/sisc/40-4/M114332.html Funding: This work was supported by NSF under grant DMS-1521573 and by the Minnesota Supercomputing Institute. †Department of Computer Science & Engineering, University of Minnesota, Twin Cities, Minneapolis, MN 55455 (email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org).
© 2018 Society for Industrial and Applied Mathematics.
- Block preconditioner
- Domain decomposition
- Krylov subspace methods
- Low rank approximation
- Nested dissection ordering
- Schur complements