Fast algorithms for Quadrature by Expansion I: Globally valid expansions

• Published in: Journal of computational physics Vol. 345; no. C; pp. 706 - 731
• Main Authors: Rachh, Manas, Klöckner, Andreas, O'Neil, Michael
• Format: Journal Article
• Language: English
• Published: Cambridge Elsevier Inc 15-09-2017; Elsevier Science Ltd; Elsevier
• Subjects: Algorithms; Boundary value problems; Computational physics; Computer Science; Fast multipole method; Helmholtz equations; High-order accuracy; Integral equations; Layer potentials; Linear systems; Nonlinear systems; Numerical methods; Operators (mathematics); Physics; Quadrature; Singular integrals; Translations; Quadrature; Singular integrals; Layer potentials; Fast multipole method; High-order accuracy; Integral equations
• ISSN: 0021-9991; 1090-2716
• DOI: 10.1016/j.jcp.2017.04.062

The use of integral equation methods for the efficient numerical solution of PDE boundary value problems requires two main tools: quadrature rules for the evaluation of layer potential integral operators with singular kernels, and fast algorithms for solving the resulting dense linear systems. Classically, these tools were developed separately. In this work, we present a unified numerical scheme based on coupling Quadrature by Expansion, a recent quadrature method, to a customized Fast Multipole Method (FMM) for the Helmholtz equation in two dimensions. The method allows the evaluation of layer potentials in linear-time complexity, anywhere in space, with a uniform, user-chosen level of accuracy as a black-box computational method.
Providing this capability requires geometric and algorithmic considerations beyond the needs of standard FMMs as well as careful consideration of the accuracy of multipole translations. We illustrate the speed and accuracy of our method with various numerical examples.