Abstract:Abstract:We consider the preconditioning of linear systems arising from four convection-diffusion model problems: scalar convection-diffusion problem, Stokes problem, Oseen problem, and NavierStokes problem. For these problems we identify an explicit Kronecker product structure of the coefficient matrices, in particular for the convection term. For the latter three model cases, the coefficient matrices have a 2 × 2 block structure, where each block is a Kronecker product or a summation of several Kronecker pro… Show more
“…Remark. The derivation of the Laplace-like system from the CP decomposition can be extended from the Helmholtz equation to convection diffusion problems of the form [4,10,65]. For these problems we define the CP-decomposition…”
Global spectral methods offer the potential to compute solutions of partial differential equations numerically to very high accuracy. In this work, we develop a novel global spectral method for linear partial differential equations on cubes by extending ideas of Chebop2 [Townsend and Olver, J. Comput. Phys., 299 (2015)] to the three-dimensional setting utilizing expansions in tensorized polynomial bases. Solving the discretized PDE involves a linear system that can be recast as a linear tensor equation. Under suitable additional assumptions, the structure of these equations admits for an efficient solution via the blocked recursive solver [Chen and Kressner, Numer. Algorithms, 84 (2020)]. In the general case, when these assumptions are not satisfied, this solver is used as a preconditioner to speed up computations.
“…Remark. The derivation of the Laplace-like system from the CP decomposition can be extended from the Helmholtz equation to convection diffusion problems of the form [4,10,65]. For these problems we define the CP-decomposition…”
Global spectral methods offer the potential to compute solutions of partial differential equations numerically to very high accuracy. In this work, we develop a novel global spectral method for linear partial differential equations on cubes by extending ideas of Chebop2 [Townsend and Olver, J. Comput. Phys., 299 (2015)] to the three-dimensional setting utilizing expansions in tensorized polynomial bases. Solving the discretized PDE involves a linear system that can be recast as a linear tensor equation. Under suitable additional assumptions, the structure of these equations admits for an efficient solution via the blocked recursive solver [Chen and Kressner, Numer. Algorithms, 84 (2020)]. In the general case, when these assumptions are not satisfied, this solver is used as a preconditioner to speed up computations.
“…The discretization of the partial differential equation leads to the following Sylvester tensor equation via the Tucker product 12,13 where the matrices and the right‐hand side tensor are known, and is the unknown tensor to be determined.…”
In this article, we propose some subspace methods such as the conjugate residual, generalized conjugate residual, biconjugate gradient, conjugate gradient squared and biconjugate gradient stabilized methods based on the tensor forms for solving the tensor equation involving the Einstein product. These proposed algorithms keep the tensor structure. The convergence analysis shows that the proposed methods converge to the solution of the tensor equation for any initial value. Some numerical results confirm the feasibility and applicability of the proposed algorithms in practice.
“…The system (1.1) arises from many areas of computational sciences and engineerings, for example, in certain finite element and finite difference discretization of Navier-Stokes equations, Oseen equations, and mixed finite element discretization of second order convection-diffusion problems (cf. [3,8,13,14,16,18,19]). For the saddle point problem, there exist many algorithms, for example, the Krylov iteration methods with block diagonal, triangular block or constraint preconditioners (see [3] and the references therein).…”
In this paper, we extend the inexact Uzawa algorithm in [Q. Hu, J. Zou, SIAM J. Matrix Anal., 23(2001), pp. 317-338] to the nonsymmetric generalized saddle point problem. The techniques used here are similar to those in [Bramble et al, Math. Comput. 69(1999), pp. 667-689], where the convergence of Uzawa type algorithm for solving nonsymmetric case depends on the spectrum of the preconditioners involved. The main contributions of this paper focus on a new linear Uzawa type algorithm for nonsymmetric generalized saddle point problems and its convergence. This new algorithm can always converge without any prior estimate on the spectrum of two preconditioned subsystems involved, which may not be easy to achieve in applications. Numerical results of the algorithm on the Navier-Stokes problem are also presented.
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