Fast Multipole Method Algorithm Research Articles

Fast Power Series Solution of Large 3-D Electrodynamic Integral Equation for PEC Scatterers

This paper presents a new fast power series solution method to solve the Hierarchal Method of Moment (MoM) matrix for a large complex, perfectly electric conducting (PEC) 3D structures. The proposed power series solution converges in just two (2) iterations which is faster than the conventional fast solver–based iterative solution. The method is purely algebraic in nature and, as such applicable to existing conventional methods. The method uses regular fast solver Hierarchal Matrix (H-Matrix) and can also be applied to Multilevel Fast Multipole Method Algorithm (MLFMA). In the proposed method, we use the scaling of the symmetric near-field matrix to develop a diagonally dominant overall matrix to enable a power series solution. Left and right block scaling coefficients are required for scaling near-field blocks to diagonal blocks using Schur’s complement method. However, only the right-hand scaling coefficients are computed for symmetric near-field matrix leading to saving of computation time and memory. Due to symmetric property, the left side-block scaling coefficients are just the transpose of the right-scaling blocks. Next, the near-field blocks are replaced by scaled near-field diagonal blocks. Now the scaled near-field blocks in combination with far-field and scaling coefficients are subjected to power series solution terminating after only two terms. As all the operations are performed on the near-field blocks, the complexity of scaling coefficient computation is retained as O(N)O⁢(N). The power series solution only involves the matrix-vector product of the far-field, scaling coefficients blocks, and inverse of scaled near-field blocks. Hence, the solution cost remains O(NlogN)O⁢(N⁢l⁢o⁢g⁢N). Several numerical results are presented to validate the efficiency and robustness of the proposed numerical method.

Fast multipole method for 3-D Poisson-Boltzmann equation in layered electrolyte-dielectric media

In this paper, we propose a fast multipole method (FMM) for 3-D linearized Poisson–Boltzmann (PB) equation in layered electrolyte-dielectric media. We will extend our previous work on FMMs for Helmholtz and Laplace equations in layered media [1,2] to the case of electrolyte and dielectric layered media for applications arising from biophysics and colloidal fluids, such as ion channel transport and Helmholtz double layers. Two key mathematical formulas are developed for this purpose: Firstly, a Funk–Hecke formula for purely imaginary wave numbers is derived, which facilitates the derivation of multipole expansions of the potential far fields of charges in layered electrolyte-dielectric media. Secondly, a recurrence formula is constructed for run-time computations of the Sommerfeld-type integrals used in the FMM algorithm. Numerical results show that the proposed FMM for interactions of charges embedded in layered media under screened PB potentials has the same accuracy and the O(N) computational complexity as the classic FMM for charge interactions in the free space.

Extension of the fast multipole method for the rectangular cells with an anisotropic partition tree structure.

The fast multipole method (FMM) is an order N method for the numerically rigorous calculation of the electrostatic interactions among point charges in a system of interest. The FMM is utilized for massively parallelized software for molecular dynamics (MD) calculations. However, an inconvenient limitation is imposed on the implementation of the FMM: In three-dimensional case, a cubic MD unit cell is hierarchically divided by the octree partitioning under isotropic periodic boundary conditions along three axes. Here, we extended the FMM algorithm adaptive to a rectangular MD unit cell with different periodicity along the axes by applying an anisotropic hierarchical partitioning. The algorithm was implemented into the parallelized general-purpose MD calculation software designed for a system with uniform distribution of point charges in the unit cell. The partition tree can be a mixture of binary and ternary branches, the branches being chosen arbitrarily with respect to the coordinate axes at any levels. Errors in the calculated electrostatic interactions are discussed in detail for a selected partition tree structure. The extension enables us to execute MD calculations under more general conditions for the shape of the unit cell, partition tree, and boundary conditions, keeping the accuracy of the calculated electrostatic interactions as high as that with the conventional FMM. An extension of the present FMM algorithm to other prime number branches, such as 5 and 7, is straightforward.

Super-fast multipole method for power frequency electric field in substations

Purpose – The purpose of this study is to calculate the frequency electric field in substation. Design/methodology/approach – The paper proposes a novel fast multipole method (FMM) called Super-FMM to solve the PFEF problems in substations. The paper substitutes the original approaches for analytic expansions and translations through equivalent density representations. Findings – The paper shows that the Super-FMM is more efficient in terms of the complexity of its storage spaces and computational costs compared with the best-known FMM when placed under scenarios with exactly the same error rates. Research limitations/implications – Using the fast Fourier transform algorithm can further improve the optimization algorithm and computational efficiency. Originality/value – A novel FMM called Super-FMM is proposed, which has a structure similar to that of the adaptive FMM algorithm, but the paper substitutes the original approaches for analytic expansions and translations through equivalent density representations.

A wideband FMBEM for 2D acoustic design sensitivity analysis based on direct differentiation method

This paper presents a wideband fast multipole boundary element method (FMBEM) for two dimensional acoustic design sensitivity analysis based on the direct differentiation method. The wideband fast multipole method (FMM) formed by combining the original FMM and the diagonal form FMM is used to accelerate the matrix-vector products in the boundary element analysis. The Burton---Miller formulation is used to overcome the fictitious frequency problem when using a single Helmholtz boundary integral equation for exterior boundary-value problems. The strongly singular and hypersingular integrals in the sensitivity equations can be evaluated explicitly and directly by using the piecewise constant discretization. The iterative solver GMRES is applied to accelerate the solution of the linear system of equations. A set of optimal parameters for the wideband FMBEM design sensitivity analysis are obtained by observing the performances of the wideband FMM algorithm in terms of computing time and memory usage. Numerical examples are presented to demonstrate the efficiency and validity of the proposed algorithm.

Calderón preconditioning approaches for PMCHWT formulations for Maxwell's equations

SUMMARYPreconditioning methods based on Calderón's formulae for the Poggio–Miller–Chang–Harrington–Wu–Tsai formulations for Maxwell's equations in 3D are discussed. Five different types of formulations are proposed. The first three use different basis functions for surface electric and magnetic currents. The first type is a preconditioning just by appropriately ordering the coefficient matrix using the Gramian matrix as the preconditioner. Other two types utilise preconditioners constructed using matrices needed in the main fast multipole method algorithms. The fourth and fifth types are similar to the second and third types, but they use the same basis functions for both surface electric and magnetic currents. We make several numerical experiments with proposed preconditioners to confirm the efficiency of these proposed methods. Copyright © 2012 John Wiley & Sons, Ltd.

Calderon's preconditioning for periodic fast multipole method for elastodynamics in 3D

SUMMARYPreconditioning methods based on Calderon's formulae for the periodic fast multipole method for elastodynamics in 3D are investigated. Three different types of formulations are proposed. The first type is a preconditioning just by appropriately ordering the coefficient matrix without multiplying preconditioners. The other two types utilise preconditioners constructed using matrices needed in the main fast multipole method algorithms. We make several numerical experiments with proposed preconditioners to confirm the efficiency of these proposed methods. We also conclude that the preconditioning of the first type is faster with respect to the computational time than other preconditioning methods discussed in this article. Copyright © 2012 John Wiley & Sons, Ltd.

A Fourier-series-based kernel-independent fast multipole method

We present in this paper a new kernel-independent fast multipole method (FMM), named as FKI-FMM, for pairwise particle interactions with translation-invariant kernel functions. FKI-FMM creates, using numerical techniques, sufficiently accurate and compressive representations of a given kernel function over multi-scale interaction regions in the form of a truncated Fourier series. It provides also economic operators for the multipole-to-multipole, multipole-to-local, and local-to-local translations that are typical and essential in the FMM algorithms. The multipole-to-local translation operator, in particular, is readily diagonal and does not dominate in arithmetic operations. FKI-FMM provides an alternative and competitive option, among other kernel-independent FMM algorithms, for an efficient application of the FMM, especially for applications where the kernel function consists of multi-physics and multi-scale components as those arising in recent studies of biological systems. We present the complexity analysis and demonstrate with experimental results the FKI-FMM performance in accuracy and efficiency.

A Wideband Fast Multipole Method for the two-dimensional complex Helmholtz equation

A Wideband Fast Multipole Method (FMM) for the 2D Helmholtz equation is presented. It can evaluate the interactions between N particles governed by the fundamental solution of 2D complex Helmholtz equation in a fast manner for a wide range of complex wave number k, which was not easy with the original FMM due to the instability of the diagonalized conversion operator. This paper includes the description of theoretical backgrounds, the FMM algorithm, software structures, and some test runs. Program summary Program title: 2D-WFMM Catalogue identifier: AEHI_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEHI_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 4636 No. of bytes in distributed program, including test data, etc.: 82 582 Distribution format: tar.gz Programming language: C Computer: Any Operating system: Any operating system with gcc version 4.2 or newer Has the code been vectorized or parallelized?: Multi-core processors with shared memory RAM: Depending on the number of particles N and the wave number k Classification: 4.8, 4.12 External routines: OpenMP ( http://openmp.org/wp/) Nature of problem: Evaluate interaction between N particles governed by the fundamental solution of 2D Helmholtz equation with complex k. Solution method: Multilevel Fast Multipole Algorithm in a hierarchical quad-tree structure with cutoff level which combines low frequency method and high frequency method. Running time: Depending on the number of particles N, wave number k, and number of cores in CPU. CPU time increases as N log N.

High scalability multipole method. Solving half billion of unknowns

Large electromagnetic simulations are needed for improvement of design in industry. Up to now, the previous limits in the scalability of the available codes were an important barrier. In this work, an efficient parallel implementation of the fast multipole method (FMM) combined with the fast Fourier transform (FFT) is presented. The good scalability of the parallel FMM-FFT, combined with some performance improvements, has shown to be very effective when using large parallel high performance supercomputers. A challenging problem with more than 0.5 billion unknowns has been solved in the Finis Terrae Supercomputer recently. This is the largest problem analyzed in computational electromagnetics to date, which confirms that the proposed implementation of the FMM-FFT constitutes a very interesting alternative to the more frequently used multilevel FMM algorithm (MLFMA).

Characterization of the accuracy of the fast multipole method in particle simulations

AbstractThe fast multipole method (FMM) is a fast summation algorithm capable of accelerating pairwise interaction calculations, known as N‐body problems, from an algorithmic complexity of 𝒪(N2) to 𝒪(N) for N particles. The algorithm has brought a dramatic increase in the capability of particle simulations in many application areas, such as electrostatics, particle formulations of fluid mechanics, and others. Although the literature on the subject provides theoretical error bounds for the FMM approximation, there are not many reports on the measured errors in a suite of computational experiments that characterize the accuracy of the method in relation with the different parameters available to the user. We have performed such an experimental investigation, and summarized the results of about 1500 calculations using the FMM algorithm, applied to the 2D vortex particle method. In addition to the more standard diagnostic of the maximum error, we supply illustrations of the spatial distribution of the errors, offering visual evidence of all the contributing factors to the overall approximation accuracy: multipole expansion, local expansion, hierarchical spatial decomposition (interaction lists, local domain, far domain). This presentation is a contribution to any researcher wishing to incorporate the FMM acceleration to their application code, as it aids in understanding where accuracy is gained or compromised. Copyright © 2009 John Wiley & Sons, Ltd.

An FMM for orthotropic periodic boundary value problems for Maxwell's equations

This paper presents a Fast Multipole Method (FMM) for orthotropic periodic problems for Maxwell's equations in 3D. We consider scattering problems where two-dimensional arrays of dielectric scatterers are arranged periodically with different periodic lengths in two orthogonal directions. The multipole and local expansions of the periodic Green function are used for accelerating the solution of the integral equations. We derive Fourier integral expressions for the periodic Green function and its derivatives, which are essential ingredients in our formulation. The cells used in the proposed FMM are not cubic because we identify the unit cell of the periodic structure with the ‘level 0 cell’ in the FMM tree. We show modifications required to the FMM algorithm for introducing non-cubic cells. Through numerical tests we conclude that the proposed method is efficient and accurate.

FMM에 의한 프랙탈 안테나 고속 해석

본 논문에서는 FMM(Fast Multipole Method)을 적용하여 평면형 다층 구조인 마이크로스트립 프랙탈 안테나 구조에 대한 고속 해석을 구현하였다. 우선 FMM 알고리즘에 이용되는 적분식인 MPIE(Mixed Potential Integral Equation)을 풀기 위해서 실수축 적 분 방법(RAIM: Real-Axis Integration Method)으로부터 정확한 공간 영역 그린함수를 구한다. 구해진 그린함수를 MoM(Method of Moment)을 이용하여 계산할 경우, 연산과 메모리 요구량 <TEX>$O(N^2)$</TEX>이 소요되는데, 이를 거대 구조의 해석에 대해 적용할 때나 높은 정확성을 위한 셀(미지수 N) 수의 증가하는 경우 계산량이 기하급수적으로 증가하여 구조 해석에 문제가 된다. FMM은 이와 같은 연산과 메모리 요구량의 문제점을 해결하기 위하여 개발되었다. FMM은 그린함수의 가법 정리(addition theorem)를 이용하여 행렬-벡터 곱의 복잡성을 줄여 연산과 메모리 요구량을 <TEX>$O(N^{1.5})$</TEX>으로 줄인다. 시어핀스키(Sierpinski) 프랙탈 안테나의 구조에 대해 MoM과 FMM를 적용, 상용 툴과 계산 결과의 정확성, 계산 시 메모리 크기, 해석 시간 등을 비교하여 효율성을 보여주었다. In this paper, we present a fast analysis of multilayer microstrip fractal structure by using the fast multipole method (FMM). In the analysis, accurate spatial green's functions from the real-axis integration method(RAIM) are employed to solve the mixed potential integral equation(MPIE) with FMM algorithm. MoM's iteration and memory requirement is <TEX>$O(N^2)$</TEX> in case of calculation using the green function. the problem is the unknown number N can be extremely large for calculation of large scale objects and high accuracy. To improve these problem is fast algorithm FMM. FMM use the addition theorem of green function. So, it reduce the complexity of a matrix-vector multiplication and reduce the cost of calculation to the order of <TEX>$O(N^{1.5})$</TEX>, The efficiency is proved from comparing calculation results of the moment method and Fast algorithm.

546 3次元Maxwell方程式直交異方性周期境界値問題における高速多重極境界要素法(OS12.境界要素法の高度化と最新応用(2),オーガナイズドセッション)

This presentation discusses an FMM (Fast Multipole Method) for orthotropic periodic boundary value problems for Maxwell's equations in 3D. We consider scattering problems where metallic or dielectric scatters are aligned periodically with different periodic lengths in two orthogonal directions. The multipole and local expansions of the periodic Green function are used for accelerating the solution of the integral equations. We derive Fourier integral expressions for the periodic Green function and its derivatives, which are essential ingredients in our formulation. The cells used in the proposed FMM are not cubic because all the cells in the FMM tree are geometrically similar to the unit cell of the periodic structure. We show modifications required to the FMM algorithm for introducing non-cubic cells. Through numerical tests we conclude that the proposed method is efficient and accurate.

A 3-D indirect boundary element method for bounded creeping flow of drops

The simulation of the flow of emulsions in porous media presents formidable challenges, due to the extremely complex evolving geometry. Methods based on boundary integral equations, suitable for creeping flows, reduce the effort dedicated to geometry representation, but can become computationally expensive. An efficient indirect boundary integral formulation representing deformable drops in a bounded Stokes flow, resulting in a set of Fredholm integral equations of the second kind, is presented. The boundary element method (BEM) based on the formulation employs an accurate numerical integration scheme for the singular kernels involved, an effective and accurate curvature and normal calculation method, and an adaptive remeshing method to simulate interfacial deformation of drops. Two benchmark problems are used to assess the accuracy of the method, and to investigate its behavior for large problems. The method is found to provide accurate results combined with well-posedness, making it suitable for use in accelerated fast multipole method algorithms.

Fast multipole method based solution of electrostatic and magnetostatic field problems

Applications of boundary element methods (BEM) to the solution of static field problems in electrical engineering are considered in this paper. The choice of a suitable BEM formulation for electrostatics, steady current flow fields or magnetostatics is discussed from user's point of view. The dense BEM matrix is compressed with an enhanced fast multipole method (FMM) which combines well-known BEM techniques with the FMM approach. An adaptive grouping scheme for problem oriented meshes is presented along with a discussion on the influence of the mesh to the efficiency of the FMM. The computational costs of the FMM algorithm are analyzed for typical problems in practice. Finally, some electrostatic and magnetostatic numerical examples demonstrate the simple usability and the efficiency of the FMM.

A fast multipole method for layered media based on the application of perfectly matched layers - the 2-D case

An efficient fast multipole method (FMM) formalism to model scattering from two-dimensional (2-D) microstrip structures is presented. The technique relies on a mixed potential integral equation (MPIE) formulation and a series expression for the Green functions, based on the use of perfectly matched layers (PML). In this way, a new FMM algorithm is developed to evaluate matrix-vector multiplications arising in the iterative solution of the scattering problem. Novel iteration schemes have been implemented and a computational complexity of order O(N) is achieved. The theory is validated by means of several illustrative, numerical examples. This paper aims at elucidating the PML-FMM-MPIE concept and can be seen as a first step toward a PML based multilevel fast multipole algorithm (MLFMA) for 3-D microstrip structures embedded in layered media.

Recent Development of Linear Scaling Quantum Theories in GAMESS

Linear scaling quantum theories are reviewed especially focusing on the method adopted in GAMESS. The three key translation equations of the fast multipole method (FMM) are deduced from the general polypolar expansions given earlier by Steinborn and Ruedenberg. Simplifications are introduced for the rotation-based FMM that lead to a very compact FMM formalism. The OPS (optimum parameter searching) procedure, a stable and efficient way of obtaining the optimum set of FMM parameters, is established with complete control over the tolerable error e. In addition, a new parallel FMM algorithm, requiring virtually no inter-node communication, is suggested which is suitable for the parallel construction of Fock matrices in electronic structure calculations.

New parallel optimal‐parameter fast multipole method (OPFMM)

AbstractThe three key translation equations of the fast multipole method (FMM) are deduced from the general polypolar expansions given earlier. Simplifications are introduced for the rotation‐based FMM that lead to a very compact FMM formalism. The optimum‐parameter searching procedure, a stable and efficient way of obtaining the optimum set of FMM parameters, is established with complete control over the tolerable error (ε). This new procedure optimizes the linear scaling with respect to the number of particles for a given ε. In addition, a new parallel FMM algorithm, which requires virtually no internode communication, is suggested that is suitable for the parallel construction of Fock matrices in electronic structure calculations. © 2001 John Wiley &amp; Sons, Inc. J Comput Chem 22: 1484–1501, 2001

Fast multipole method for scattering from an arbitrary PEC target above or buried in a lossy half space

The fast multipole method (FMM) was originally developed for perfect electric conductors (PECs) in free space, through exploitation of the spectral properties of the free-space Green's function. In the work reported here, the FMM is modified, for scattering from an arbitrary three-dimensional (3-D) PEC target above or buried in a lossy half space. The "near" terms in the FMM are handled via the original method-of-moments (MoM) analysis, wherein the half-space Green's function is evaluated efficiently and rigorously through application of the method of complex images. The "far" FMM interactions, which employ a clustering of expansion and testing functions, utilize an approximation to the Green's function dyadic via real image sources and far-field reflection dyadics. The half-space FMM algorithm is validated through comparison with results computed via a rigorous MoM analysis. Further, a detailed comparison is performed on the memory and computational requirements of the MoM and FMM algorithms for a target in the vicinity of a half-space interface.