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arXiv 2201.07325math.NAcs.NAphysics.comp-ph
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FMM-LU:三维多尺度边界积分方程的快速直接解法

FMM-LU: A fast direct solver for multiscale boundary integral equations in three dimensions

Daria Sushnikova, Leslie Greengard, Michael O'Neil, Manas Rachh

摘要:

我们提出了一个快速直接求解三维复杂曲面上的边界积分方程,使用最近推出的递归强迭代格式的扩展。对于不是高度振荡的问题,我们的算法计算的密集系统矩阵的${LU}$样的层次因式分解,允许应用程序的逆在$\mathcal O(n)$时间,其中$n$是表面上的未知数的数量。因子分解本身也与系统大小成线性关系,尽管有一个更大的常数。该方案是建立在一个水平限制的自适应八叉树数据结构,因此,它是高度非均匀离散化兼容。此外,该计划是与高阶精度的局部校正Nyström积分方法集成的奇异和弱奇异格林函数中使用的整表示。我们的方法有直接的应用程序在计算物理中的各种问题。我们在这里集中研究其性能在低到中等频率的声散射(由亥姆霍兹方程),并提供严格的理由通过代理表面的子矩阵压缩。

英文摘要:

We present a fast direct solver for boundary integral equations on complex surfaces in three dimensions using an extension of the recently introduced recursive strong skeletonization scheme. For problems that are not highly oscillatory, our algorithm computes an ${LU}$-like hierarchical factorization of the dense system matrix, permitting application of the inverse in $\mathcal O(n)$ time, where $n$ is the number of unknowns on the surface. The factorization itself also scales linearly with the system size, albeit with a somewhat larger constant. The scheme is built on a level-restricted adaptive octree data structure, and therefore it is compatible with highly nonuniform discretizations. Furthermore, the scheme is coupled with high-order accurate locally-corrected Nyström quadrature methods to integrate the singular and weakly-singular Green's functions used in the integral representations. Our method has immediate applications to a variety of problems in computational physics. We concentrate here on studying its performance in acoustic scattering (governed by the Helmholtz equation) at low to moderate frequencies, and provide rigorous justification for compression of submatrices via proxy surfaces.

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