Novel multilevel preconditioners for the systems arising from plane wave discretization of Helmholtz equations with large wave numbers

TL;DR

This paper develops novel multilevel parallel preconditioners tailored for efficient solution of large-scale Helmholtz systems from plane wave discretizations, demonstrating nearly stable convergence as wave numbers grow.

Contribution

The paper introduces new multilevel preconditioners based on space decomposition for plane wave discretizations of Helmholtz equations, improving solver efficiency for high wave numbers.

Findings

Preconditioners achieve nearly stable iteration counts with increasing wave number.

The proposed methods outperform standard multigrid preconditioners in stability.

Preconditioners are effective for both PWLS and PWDG discretizations.

Abstract

In this paper we are concerned with fast algorithms for the systems arising from the plane wave discretizations for two-dimensional Helmholtz equations with large wave numbers. We consider the plane wave weighted least squares (PWLS) method and the plane wave discontinuous Galerkin (PWDG) method. The main goal of this paper is to construct multilevel parallel preconditioners for solving the resulting Helmholtz systems. To this end, we first build a multilevel overlapping space decomposition for the plane wave discretization space based on a multilevel overlapping domain decomposition method. Then, corresponding to the space decomposition, we construct an additive multilevel preconditioner for the underlying Helmholtz systems. Further, we design both additive and multiplicative multilevel preconditioners with smoothers, which are different from the standard multigrid preconditioners. We apply the proposed multilevel preconditioners with a {\it constant} coarsest mesh size to solve two dimensional Helmholtz systems generated by PWLS method or PWDG method, and we find that the new preconditioners possess nearly stable convergence, i.e., the iteration counts of the preconditioned iterative methods (PCG or PGMRES) with the preconditioners increase very slowly when the wave number increases (and the fine mesh size decreases).