Firstly,a review is given by classifying the existing fast algorithms for solving large-scale discrete linear systems arising from the Multi-Group Radiation Diffusion(MGRD)equations.Secondly,based on our recent work on parallel algebraic multigrid(AMG),two preconditioning algorithms and related theoretical frameworks are developed on a higher level.One is the approximate Schur complement type based on physical quantities and the other is the combined type based on physical and algebraic features,and the relevant components of these works are portrayed within these frameworks.Based on the above framework,a approximate Schur complement preconditioner with fundamental approximation property and low computational complexity is designed,and the corresponding spectral equivalence theory is established.Numerical experiments show that the new preconditioner has better robustness and computational efficiency.Finally,several issues that need to be further addressed are presented.
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