A preconditioning technique for an all-at-once system from Volterra subdiffusion equations with graded time steps

YL Zhao, XM Gu, A Ostermann - Journal of Scientific Computing, 2021 - Springer
Volterra subdiffusion problems with weakly singular kernel describe the dynamics of
subdiffusion processes well. The graded L 1 scheme is often chosen to discretize such …

Exponential-sum-approximation technique for variable-order time-fractional diffusion equations

JL Zhang, ZW Fang, HW Sun - Journal of Applied Mathematics and …, 2022 - Springer
In this paper, we study the variable-order (VO) time-fractional diffusion equations. For a VO
function α (t) ∈ (0, 1) α (t)∈(0, 1), we develop an exponential-sum-approximation (ESA) …

A note on parallel preconditioning for the all-at-once solution of Riesz fractional diffusion equations

XM Gu, YL Zhao, XL Zhao, B Carpentieri… - arXiv preprint arXiv …, 2020 - arxiv.org
The $ p $-step backwards difference formula (BDF) for solving the system of ODEs can result
in a kind of all-at-once linear systems, which are solved via the parallel-in-time …

A preconditioned fast finite element approximation to variable-order time-fractional diffusion equations in multiple space dimensions

J Jia, H Wang, X Zheng - Applied Numerical Mathematics, 2021 - Elsevier
We develop a preconditioned fast divided-and-conquer finite element approximation for the
initial-boundary value problem of variable-order time-fractional diffusion equations. Due to …

A fast method for variable-order space-fractional diffusion equations

J Jia, X Zheng, H Fu, P Dai, H Wang - Numerical Algorithms, 2020 - Springer
We develop a fast divide-and-conquer indirect collocation method for the homogeneous
Dirichlet boundary value problem of variable-order space-fractional diffusion equations. Due …

Fast second-order evaluation for variable-order Caputo fractional derivative with applications to fractional sub-diffusion equations

JL Zhang, ZW Fang, HW Sun - arXiv preprint arXiv:2102.02960, 2021 - arxiv.org
In this paper, we propose a fast second-order approximation to the variable-order (VO)
Caputo fractional derivative, which is developed based on $ L2 $-$1 _\sigma $ formula and …

A fast collocation approximation to a two-sided variable-order space-fractional diffusion equation and its analysis

J Jia, H Wang, X Zheng - Journal of Computational and Applied …, 2021 - Elsevier
We develop a fast indirect collocation method for a two-sided variable-order space-fractional
diffusion equation, which models, eg, the superdiffusive transport of solute in a …

Robust fast method for variable-order time-fractional diffusion equations without regularity assumptions of the true solutions

J Zhang, ZW Fang, HW Sun - Applied Mathematics and Computation, 2022 - Elsevier
A robust fast method for mobile-immobile variable-order (VO) time-fractional diffusion
equations (tFDEs) is developed, superiorly handling the cases of small or vanishing lower …

[HTML][HTML] All-at-once multigrid approaches for one-dimensional space-fractional diffusion equations

M Donatelli, R Krause, M Mazza, K Trotti - Calcolo, 2021 - Springer
We focus on a time-dependent one-dimensional space-fractional diffusion equation with
constant diffusion coefficients. An all-at-once rephrasing of the discretized problem, obtained …

Divide-and-Conquer Solver in Tensor-Train Format for d-Dimensional Time-Space Fractional Diffusion Equations

YC Huang, LK Chou, SL Lei - Journal of Scientific Computing, 2023 - Springer
A divide-and-conquer solver coupled with Tensor-Train (TT) format is proposed for solving
the d-dimensional time-space fractional diffusion equations with alternating direction implicit …