Abstract:Citation:Pan, X.-M., and X.-Q. Sheng (2014) Abstract The inherent difficulties of traditional preconditioning techniques are revealed by numerically analyzing characteristics of method of moments systems with respect to multiscale dynamic electromagnetic applications. Techniques are developed to solve these difficulties for the traditional sparse approximate inverse preconditioner. The proposed techniques include a skeleton-based filtering strategy aiming to overcome the awkward filtering strategy extensively … Show more
“…Owing to its inherent parallelism and attractive numerical stability, the SPAI preconditioner has become a popular choice in the electromagnetic community, being used for solving extremely large dense matrix problems [13,18,19]. …”
“…Another strategy positively investigated to relax the limita tions due to the lack of global couplings is to utilize the inter polative decomposition "skeletonization," which is equivalent to ranking and ordering principal basis/testing functions according to their capability of radiation/receiving [19].…”
The boundary-element method is a popular approach for solving electromagnetic applications. It can reduce a threedimensional problem to solving a two-dimensional surface problem, simplifying considerably the mesh generation, and limiting grid-dispersion errors. The Method of Moments discretization of boundary integral equations leads to a very large and dense linear systems. It is mandatory to use iterative methods and robust preconditioning for the solution. Identifying the best class of method with respect to numerical stability, inherent parallelism, and good scalability with respect to the frequency of the problem is still an open research issue.
“…Owing to its inherent parallelism and attractive numerical stability, the SPAI preconditioner has become a popular choice in the electromagnetic community, being used for solving extremely large dense matrix problems [13,18,19]. …”
“…Another strategy positively investigated to relax the limita tions due to the lack of global couplings is to utilize the inter polative decomposition "skeletonization," which is equivalent to ranking and ordering principal basis/testing functions according to their capability of radiation/receiving [19].…”
The boundary-element method is a popular approach for solving electromagnetic applications. It can reduce a threedimensional problem to solving a two-dimensional surface problem, simplifying considerably the mesh generation, and limiting grid-dispersion errors. The Method of Moments discretization of boundary integral equations leads to a very large and dense linear systems. It is mandatory to use iterative methods and robust preconditioning for the solution. Identifying the best class of method with respect to numerical stability, inherent parallelism, and good scalability with respect to the frequency of the problem is still an open research issue.
“…Different strategies have been presented to overcome the dense-discretization breakdown. A first class of techniques relies on algebraic strategies such as the incomplete LU factorization [12,13], sparse approximate inverse [14,15], or near-range preconditioners [16]. While they improve the conditioning, the condition number still grows with decreasing h.…”
We present a Calderón preconditioner for the electric field integral equation (EFIE), which does not require a barycentric refinement of the mesh and which yields a Hermitian, positive definite (HPD) system matrix allowing for the usage of the conjugate gradient (CG) solver. The resulting discrete equation system is immune to the low-frequency and the dense-discretization breakdown and, in contrast to existing Calderón preconditioners, no second discretization of the EFIE operator with Buffa-Christiansen (BC) functions is necessary. This preconditioner is obtained by leveraging on spectral equivalences between (scalar) integral operators, namely the single layer and the hypersingular operator known from electrostatics, on the one hand, and the Laplace-Beltrami operator on the other hand. Since our approach incorporates Helmholtz projectors, there is no search for global loops necessary and thus our method remains stable on multiply connected geometries. The numerical results demonstrate the effectiveness of this approach for both canonical and realistic (multi-scale) problems.
“…Thus, alleviation of any difficulty along the implementation of an analytical model in a numerically stable fashion has utmost importance. The relevant concerns in the past five decades are issued in the context of implementation of the analytical formulations efficiently in computer [Bates, 1975;Ivanov, 1968;Poyedinchuk et al, 2000;Yiğit and Dikmen, 2011;Bruno and Lintner, 2012;Dikmen et al, 2013;Sever et al, 2014;Sandström and Akeab, 2014;Pan and Sheng, 2014].…”
Section: Introductionmentioning
confidence: 99%
“…Despite the excessive memory and processor resources of the modern computers, these criteria are circumstantial [Poyedinchuk et al, 2000] because the only practical way to obtain a reliable and stable solution avoiding the round-off errors is making sure that the condition number of the truncated algebraic system does not reach (preferably) or exceed (meaning, no significant digits are obtained) the power of the mantissa length (i.e., 2 53 ≈ 10 16 for standard PC) [Poyedinchuk et al, 2000;Wilkinson, 1975]. This problem was elaborated in Sever et al [2014] for a pair of impedance circular cylinders; in Poyedinchuk et al [2000], Sandström and Akeab [2014], and Pan and Sheng [2014] for a wider class of geometries; in [Yiğit and Dikmen [2011] and Bruno and Lintner [2012] for open 2-D geometries; and in Ivanov [1968] for pairs of canonic shapes. Basically, they aim at reducing the LAES1 into a linear algebraic equation system of the second kind (LAES2) in l 2 (i.e., the functional space of square summable sequences).…”
The new regularization of the well-known analytical formulation of the monochromatic electromagnetic wave scattering by a few eccentrically multilayered homogenous circular cylinders is presented. It is found out that a regularization of this formulation is absolutely necessary. The two-sided regularization that we made is based on the integral formulation of the mentioned problem. The polarization of the fields are parallel to the longitudinal axes of the cylinders; thus, a two dimensional problem for each both polarizations are under consideration. The condition number of the resulting algebraic system is uniformly bounded while its truncation number increases. The numerical results are validated by existing results such as near and far fields obtained under various geometrical and electrical parameters of the scattering problem. Numerical results including the condition numbers of the regularized and nonregularized systems show that only regularized system gives numerically stable results with any desired accuracy in a wide range of frequencies from quasistatic to rather high-frequency range, limited only by the capabilities of the computer with the guarantee of the physical reliability of the solution.
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