Communications on Applied Mathematics and Computation ›› 2025, Vol. 7 ›› Issue (5): 1848-1860.doi: 10.1007/s42967-024-00411-z

• ORIGINAL PAPERS • 上一篇    

An ADI Iteration Method for Solving Discretized Two-Dimensional Space-Fractional Diffusion Equations

Yu-Hong Ran, Qian-Qian Wu   

  1. Center for Nonlinear Studies, School of Mathematics, Northwest University, Xi'an, 710127, Shaanxi, China
  • 收稿日期:2023-11-30 修回日期:2024-03-04 接受日期:2024-04-05 出版日期:2024-09-20 发布日期:2024-09-20
  • 通讯作者: Yu-Hong Ran,E-mail:ranyh@nwu.edu.cn E-mail:ranyh@nwu.edu.cn

An ADI Iteration Method for Solving Discretized Two-Dimensional Space-Fractional Diffusion Equations

Yu-Hong Ran, Qian-Qian Wu   

  1. Center for Nonlinear Studies, School of Mathematics, Northwest University, Xi'an, 710127, Shaanxi, China
  • Received:2023-11-30 Revised:2024-03-04 Accepted:2024-04-05 Online:2024-09-20 Published:2024-09-20
  • Contact: Yu-Hong Ran,E-mail:ranyh@nwu.edu.cn E-mail:ranyh@nwu.edu.cn

摘要: The two-dimensional (2D) space-fractional diffusion equations can be effectively discretized by an implicit finite difference scheme with the shifted Grünwald formula. The coefficient matrices of the discretized linear systems are equal to the sum of the identity matrix and a block-Toeplitz with a Toeplitz-block matrix. In this paper, one variant of the alternating direction implicit (ADI) iteration method is proposed to solve the discretized linear systems. By making use of suitable permutations, each iteration of the ADI iteration method requires the solutions of two linear subsystems whose coefficient matrices are block diagonal matrices with diagonal blocks being Toeplitz matrices. These two linear subsystems can be solved block by block by fast or superfast direct methods. Theoretical analyses show that the ADI iteration method is convergent. In particular, we derive a sharp upper bound about its asymptotic convergence rate and deduce the optimal value of its iteration parameter. Numerical results exhibit that the corresponding ADI preconditioner can improve the computational efficiency of the Krylov subspace iteration methods.

关键词: Space-fractional diffusion equations, Block-Toeplitz with Toeplitz-block (BTTB) matrix, Alternating direction implicit (ADI) iteration, Preconditioning, Krylov subspace method

Abstract: The two-dimensional (2D) space-fractional diffusion equations can be effectively discretized by an implicit finite difference scheme with the shifted Grünwald formula. The coefficient matrices of the discretized linear systems are equal to the sum of the identity matrix and a block-Toeplitz with a Toeplitz-block matrix. In this paper, one variant of the alternating direction implicit (ADI) iteration method is proposed to solve the discretized linear systems. By making use of suitable permutations, each iteration of the ADI iteration method requires the solutions of two linear subsystems whose coefficient matrices are block diagonal matrices with diagonal blocks being Toeplitz matrices. These two linear subsystems can be solved block by block by fast or superfast direct methods. Theoretical analyses show that the ADI iteration method is convergent. In particular, we derive a sharp upper bound about its asymptotic convergence rate and deduce the optimal value of its iteration parameter. Numerical results exhibit that the corresponding ADI preconditioner can improve the computational efficiency of the Krylov subspace iteration methods.

Key words: Space-fractional diffusion equations, Block-Toeplitz with Toeplitz-block (BTTB) matrix, Alternating direction implicit (ADI) iteration, Preconditioning, Krylov subspace method