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Implementation of divide-and-conquer method including Hartree-Fock exchange interaction

JOURNAL OF COMPUTATIONAL CHEMISTRY 2007年第12期28卷 2003-2012页

作者： Akama, Tomoko Kobayashi, Masato Nakai, Hiromi Waseda Univ Sch Sci & Engn Dept Chem Tokyo 1698555 Japan

The divide-and-conquer (DC) method, which is one of the linear-scaling methods avoiding explicit diagonalization of the Fock matrix. has been applied mainly to pure density functional theory (DFT) or semiempirical molecular orbital calculations so far. The present study applies the DC method to such calculations including the Hartree-Fock (HF) exchange terms as the HF and hybrid HF/DFT. Reliability of the DC-HF and DC-hybrid HF/DFT is found to be strongly dependent oil the cut-off radius, which defines the localization region in the DC formalism. This dependence on the cut-off radius is assessed from various points of view: that is, total energy, energy components, local energies, and density of states. Additionally, to accelerate the self-consistent field convergence in DC calculations, a new convergence technique is proposed. (c) 2007 Wiley, Periodicals, Inc.

关键词： divide-and-conquer method Hartree-Fock exchange linear-scaling method local energy density of states

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Two-Level Hierarchical Parallelization of Second-Order Moller-Plesset Perturbation Calculations in divide-and-conquer method

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JOURNAL OF COMPUTATIONAL CHEMISTRY 2011年第13期32卷 2756-2764页

作者： Katouda, Michio Kobayashi, Masato Nakai, Hiromi Nagase, Shigeru Inst Mol Sci Dept Theoret & Computat Mol Sci Okazaki Aichi 4448585 Japan Waseda Univ Sch Adv Sci & Engn Dept Chem & Biochem Tokyo 1698555 Japan Waseda Univ Res Inst Sci & Engn Tokyo 1698555 Japan Japan Sci & Technol Agcy CREST Tokyo 1020075 Japan

A two-level hierarchical parallelization scheme including the second-order Moller-Plesset perturbation (MP2) theory in the divide-and-conquer method is presented. The scheme is a combination of coarse-grain parallelization assigning each subsystem to a group of processors, with fine-grain parallelization, where the computational tasks for evaluating MP2 correlation energy of the assigned subsystem are distributed among processors in the group. Test calculations demonstrate that the present scheme shows high parallel efficiency and makes MP2 calculations practical for very large molecules. (C) 2011 Wiley Periodicals, Inc. J Comput Chem 32: 2756-2764, 2011

关键词： divide-and-conquer method second-order Moller-Plesset perturbation theory parallel implementation parallel algorithm parallel performance granularity linear-scaling method electron correlation large molecule extended system

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Linear-scaling electronic structure calculation program based on divide-and-conquer method

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Procedia Computer Science 2011年 4卷 1145-1150页

作者： Hiromi Nakai Masato Kobayashi Department of Chemistry and Biochemistry School of Advanced Science and EngineeringWaseda University Tokyo 169-8555 Japan Research Institute for Science and Engineering (RISE) Waseda University Tokyo 169-8555 Japan CREST Japan Science and Technology Agency 5 Sanbancho Chiyoda-ku Tokyo 102-0075 Japan Department of Theoretical and Computational Molecular Science Institute for Molecular ScienceOkazaki 444-8585 Japan

In 2009, the authors implemented the linear-scaling divide-and-conquer (DC) methods into the GAMESS quantum chemistry package. This program enabled fast energy calculations of closed-shell large molecules with high accuracy in Hartree-Fock (HF), density functional theory, and post-HF levels of theory. After the first implementation, we extended the applicability of the DC scheme into several directions. In this Paper, we summarized recent and future developments in the DC code in GAMESS, namely, the energy gradient methods and open-shell treatments.

关键词： divide-and-conquer method self-consistent field calculation open-shell system electron correlation energy gradient

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A divide-and-conquer fast finite difference method for space-time fractional partial differential equation

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COMPUTERS & MATHEMATICS WITH APPLICATIONS 2017年第6期73卷 1233-1242页

作者： Fu, Hongfei Ng, Michael K. Wang, Hong China Univ Petr Coll Sci Qingdao 266580 Shandong Peoples R China Hong Kong Baptist Univ Dept Math Kowloon Tong Hong Kong Peoples R China Univ South Carolina Dept Math Columbia SC 29208 USA

Fractional partial differential equations (FPDEs) provide better modeling capabilities for challenging phenomena with long-range time memory and spatial interaction than integer-order PDEs do. A conventional numerical discretization of space time FPDEs requires O(N2 MN) memory and 0 (MN3 M2N) computational work, where N is the number of spatial freedoms per time step and M is the number of time steps. We develop a fast finite difference method (FDM) for space time FPDE: (i) We utilize the Toeplitz-like structure of the coefficient matrix to develop a matrix-free preconditioned fast Krylov subspace iterative solver to invert the coefficient matrix at each time step. (ii) We utilize a divide -and -conquer strategy, a recursive direct solver, to handle the temporal coupling of the numerical scheme. The fast method has an optimal memory requirement of 0(MN) and an approximately linear computational complexity of phi(NM(log N+log(2) M)), without resorting to any lossy compression. Numerical experiments show the utility of the method. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： Anomalous diffusion divide-and-conquer method Finite difference method Krylov subspace iterative solver Space-time fractional partial differential equation

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divide-and-conquer Hartree-Fock-Bogoliubov method and Its Application to Conjugated Diradical Systems

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CHEMISTRY LETTERS 2016年第11期45卷 1268-1270页

作者： Kobayashi, Masato Taketsugu, Tetsuya Hokkaido Univ Dept Chem Fac Sci Sapporo Hokkaido 0600810 Japan Kyoto Univ ESICB Kyoto 6158520 Japan Japan Sci & Technol Agcy PRESTO Kawaguchi Saitama 3320012 Japan

The Hartree-Fock-Bogoliubov (HFB) theory has recently attracted considerable attention in quantum chemistry as a novel strategy to account for the static electron correlation, which plays an essential role when breaking chemical bonds and treating diradical systems. The linear-scaling divide-and-conquer (DC) method is applied to the HFB method to treat large-scale bond-breaking and/or diradical systems with reasonable computational effort.

关键词： Hartree-Fock-Bogoliubov (HFB) theory divide-and-conquer method Conjugated diradical

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SA-FPN: Scale-aware attention-guided feature pyramid network for small object detection on surface defect detection of steel strips

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MEASUREMENT 2025年 249卷

作者： Han, Lu Li, Nan Li, Jiahe Gao, Bingbing Niu, Dong Northwestern Polytech Univ Sch Automat Xian 710129 Peoples R China Xidian Univ State Key Lab Electromech Integrated Mfg High perf Xian 710071 Peoples R China Northwestern Polytech Univ Shenzhen Res Inst Shenzhen 518057 Peoples R China Xian Elect Engn Res Inst Xian 710072 Peoples R China

In recent years, the production of steel products has escalated significantly, leading to a substantial increase in defects, with smaller target imperfections becoming increasingly challenging to identify. Consequently, industries and enterprises are at a heightened risk of incurring significant economic losses, which may adversely affect their brand reputation. This paper presents a Scale-Aware Feature Pyramid Network (SA-FPN) that integrates a Scale-Aware Attention-Guided Module (SAGM) for nonlinear adjustment of neighboring features while maintaining information integrity. Additionally, SAGM utilizes an attention mechanism to reduce semantic disparities across pyramid levels. The Feature Refinement Module (FRM) further harmonizes and consolidates multi-scale features from various layers through a straightforward feature refinement process. Extensive experiments conducted on the KolektorSDD, NEU-DET, and GC10-Det surface defect datasets demonstrate the effectiveness of our approach, as indicated by the mean average precision (mAP) results of the SA-FPN, which are 100%, 86.8%, and 74.4%, respectively. Our code is made available at https://***/HL-Louis/SA-FPN.

关键词： Surface defect detection divide-and-conquer method Small object detection

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Parallel Implementation of Efficient Charge-Charge Interaction Evaluation Scheme in Periodic divide-and-conquer Density-Functional Tight-Binding Calculations

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JOURNAL OF COMPUTATIONAL CHEMISTRY 2018年第2期39卷 105-116页

作者： Nishimura, Yoshifumi Nakai, Hiromi Waseda Univ Res Inst Sci & Engn Shinjuku Ku 3-4-1 Okubo Tokyo 1698555 Japan Waseda Univ Sch Adv Sci & Engn Dept Chem & Biochem Shinjuku Ku 3-4-1 Okubo Tokyo 1698555 Japan Japan Sci & Technol Agcy CREST 4-1-8 Honcho Kawaguchi Saitama 3320012 Japan Kyoto Univ ESICB Kyoto 6158520 Japan

A low-computational-cost algorithm and its parallel implementation for periodic divide-and-conquer density-functional tightbinding (DC-DFTB) calculations are presented. The developed algorithm enables rapid computation of the interaction between atomic partial charges, which is the bottleneck for applications to large systems, by means of multipole- and interpolation-based approaches for long- and short-range contributions. The numerical errors of energy and forces with respect to the conventional Ewald-based technique can be under the control of the multipole expansion order, level of unit cell replication, and interpolation grid size. The parallel performance of four different evaluation schemes combining previous approaches and the proposed one are assessed using test calculations of a cubic water box on the K computer. The largest benchmark system consisted of 3,295,500 atoms. DC-DFTB energy and forces for this system were obtained in only a few minutes when the proposed algorithm was activated and parallelized over 16,000 nodes in the K computer. The high performance using a single node workstation was also confirmed. In addition to liquid water systems, the feasibility of the present method was examined by testing solid systems such as diamond form of carbon, face-centered cubic form of copper, and rock salt form of sodium chloride. (C) 2017 Wiley Periodicals, Inc.

关键词： density-functional tight-binding method divide-and-conquer method periodic boundary condition multipole expansion massively parallel calculation

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Unsupervised contaminated user profile identification against shilling attack in recommender system

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INTELLIGENT DATA ANALYSIS 2024年第6期28卷 1411-1426页

作者： Zhang, Fei Chan, Patrick P. K. He, Zhi-Min Yeung, Daniel S. Henan Normal Univ Coll Comp & Informat Engn Xinxiang Henan Peoples R China Key Lab Artificial Intelligence & Personalized Lea Xinxiang Henan Peoples R China South China Univ Technol Shien Ming Wu Sch Intelligent Engn Guangzhou Guangdong Peoples R China Foshan Univ Sch Elect & Informat Engn Foshan Guangdong Peoples R China

A recommender system is susceptible to manipulation through the injection of carefully crafted profiles. Some recent profile identification methods only perform well in specific attack scenarios. A general attack detection method is usually complicated or requires label samples. Such methods are prone to overtraining easily, and the process of annotation incurs high expenses. This study proposes an unsupervised divide-and-conquer method aiming to identify attack profiles, utilizing specifically designed model for each kind of shilling attack. Initially, our method categorizes the profile set into two attack types, namely Standard and Obfuscated Behavior Attacks. Subsequently, profiles are separated into clusters within the extracted feature space based on the identified attack type. The selection of attack profiles is then determined through target item analysis within the suspected cluster. Notably, our method offers the advantage of requiring no prior knowledge or annotation. Furthermore, the precision is heightened as the identification method is designed to a specific attack type, employing a less complicated model. The outstanding performance of our model, validated through experimental results on MovieLens-100K and Netflix under various attack settings, demonstrates superior accuracy and reduced running time compared to current detection methods in identifying Standard and Obfuscated Behavior Attacks.

关键词： PCA item popularity shilling attack detection divide-and-conquer method

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MILP Formulation for Aircraft Path Planning in Persistent Surveillance

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IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS 2020年第5期56卷 3796-3811页

作者： Zuo, Yan Tharmarasa, Ratnasingham Jassemi-Zargani, Rahim Kashyap, Nathan Thiyagalingam, Jeyarajan Kirubarajan, Thiagalingam T. Hangzhou Dianzi Univ Inst Informat & Control Hangzhou 310018 Peoples R China McMaster Univ ECE Dept Hamilton ON L8S 4L8 Canada DRDC Ottawa Res Ctr Ottawa Ottawa ON K2K 2Y7 Canada Rutherford Appleton Lab Sci & Technol Facil Council Didcot Oxon England

Persistent surveillance systems using manned or unmanned aerial vehicles play a crucial role in modern intelligence, surveillance, and reconnaissance missions. One of the crucial aspects that determine the quality of these systems is path planning. Path planning often attempts to optimize one or two objective metrics, such as coverage area, cost, or time, while meeting several constraints that would challenge these missions, such as weather, downtime, and amount of information gathered. A number of approaches have been proposed in the literature to address the path planning problem. However, the majority of these approaches are often based on a single objective measure, such as minimizing cost, maximizing travel distance, or maximizing coverage time. In cases where combined measures are considered, the formulations are often nondeterministic polynomial-time hard, leading to solutions that are computationally intractable. In this article, a mixed integer linear programming model with two conflicting objective functions-namely, maximizing coverage area and coverage time, has been developed. We propose a two-stage method to handle missions that involve multiple periods, multiple vehicles, and multiple dispersed areas while meeting a number of operational constraints, such as refueling and downtimes. Evaluations based on a number of simulated, yet realistic, scenarios show that our formulation leads to very promising outputs and performance.

关键词： Aircraft Path planning Surveillance Planning Aerospace electronics Base stations Unmanned aerial vehicles divide-and-conquer method mixed integer linear programming (MILP) multiobjective optimization path planning persistent surveillance

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Hierarchical parallelization of divide-and-conquer density functional tight-binding molecular dynamics and metadynamics simulations

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JOURNAL OF COMPUTATIONAL CHEMISTRY 2020年第19期41卷 1759-1772页

作者： Nishimura, Yoshifumi Nakai, Hiromi Waseda Univ Waseda Res Inst Sci & Engn Tokyo Japan Waseda Univ Sch Adv Sci & Engn Dept Chem & Biochem Tokyo Japan Kyoto Univ Elements Strategy Initiat Catalysts & Batteries Kyoto Japan

Massively parallel divide-and-conquer density functional tight-binding (DC-DFTB) molecular dynamics and metadynamics simulations are efficient approaches for describing various chemical reactions and dynamic processes of large complex systems via quantum mechanics. In this study, DC-DFTB simulations were combined with multi-replica techniques. Specifically, multiple walkers metadynamics, replica exchange molecular dynamics, and parallel tempering metadynamics methods were implemented hierarchically into the in-house Dcdftbmd program. Test simulations in an aqueous phase of the internal rotation of formamide and conformational changes of dialanine showed that the newly developed extensions increase the sampling efficiency and the exploration capabilities in DC-DFTB configuration space.

关键词： density functional tight-binding method divide-and-conquer method metadynamics molecular dynamics replica exchange method

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