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arXiv · 1703.10240

Optimal interpolation and Compatible Relaxation in Classical Algebraic Multigrid

James Brannick·Fei Cao·Karsten Kahl·Rob Falgout·Xiaozhe Hu
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Abstract

In this paper, we consider a classical form of optimal algebraic multigrid (AMG) interpolation that directly minimizes the two-grid convergence rate and compare it with the so-called ideal form that minimizes a certain weak approximation property of the coarse space. We study compatible relaxation type estimates for the quality of the coarse grid and derive a new sharp measure using optimal interpolation that provides a guaranteed lower bound on the convergence rate of the resulting two-grid method for a given grid. In addition, we design a generalized bootstrap algebraic multigrid setup algorithm that computes a sparse approximation to the optimal interpolation matrix. We demonstrate numerically that the BAMG method with sparse interpolation matrix (and spanning multiple levels) outperforms the two-grid method with the standard ideal interpolation (a dense matrix) for various scalar diffusion problems with highly varying diffusion coefficient.

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James Brannick, Fei Cao, Karsten Kahl, Rob Falgout, Xiaozhe Hu. 2017-03-29. Optimal interpolation and Compatible Relaxation in Classical Algebraic Multigrid. https://arxiv.org/abs/1703.10240

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