Search results for "Approximate"

Hits ?▲	Authors	Title	Venue	Year	Link	Author keywords
84	Patrick Cousot, Radhia Cousot	Systematic Design of Program Analysis Frameworks.	POPL	1979	DBLP DOI BibTeX RDF
64	Hennie Poulisse	Computational communicative algebra.	ISSAC	2006	DBLP DOI BibTeX RDF	approximate commutative algebra
58	Liyong Shen, Falai Chen, Bert Jüttler, Jiansong Deng	Approximate µ-Bases of Rational Curves and Surfaces.	GMP	2006	DBLP DOI BibTeX RDF	approximate ?-bases, approximate implicitization
46	Rolly Intan, Masao Mukaidono	Fuzzy Functional Dependency and Its Application to Approximate Data Querying.	IDEAS	2000	DBLP DOI BibTeX RDF	partial fuzzy functional dependency, approximate data querying, approximate data reduction, fuzzy integrity constraints, fuzzy query relations, extended query system, relational databases, projection, fuzzy set theory, conditional probability, approximate joins
45	Barbara Fryc, Krzysztof Pancerz, Zbigniew Suraj	Approximate Petri Nets for Rule-Based Decision Making.	Rough Sets and Current Trends in Computing	2004	DBLP DOI BibTeX RDF	approximate Petri nets, approximate reasoning, decision systems
43	Surender Baswana, Ramesh Hariharan, Sandeep Sen	Maintaining all-pairs approximate shortest paths under deletion of edges.	SODA	2003	DBLP BibTeX RDF
38	Krishna V. Palem, Lakshmi N. Chakrapani, Zvi M. Kedem, Lingamneni Avinash, Kirthi Krishna Muntimadugu	Sustaining moore's law in embedded computing through probabilistic and approximate design: retrospects and prospects.	CASES	2009	DBLP DOI BibTeX RDF	approximate arithmetic, approximate design, probabilistic CMOS, probabilistic arithmetic, probabilistic design, digital signal processing
38	Yiyong Xiao, Ikou Kaku, Wenbing Chang	Phi-Rough Sets Theory and Its Usage on Mining Approximate Dependencies.	ICIC (2)	2008	DBLP DOI BibTeX RDF	Approximate dependency, Partial approximate dependency, Database, Functional dependency, Rough set theory
38	George A. Gravvanis, Konstantinos M. Giannoutakis, Michael P. Bekakos, Odysseas Efremides	Parallel and Systolic Solution of Normalized Explicit Approximate Inverse Preconditioning.	J. Supercomput.	2004	DBLP DOI BibTeX RDF	finite difference systems, normalized approximate factorization, normalized approximate inverses, rate of convergence and complexity, parallel computations, preconditioning, parallel iterative methods
38	George A. Gravvanis	On the Solution of Boundary Value Problems by Using Fast Generalized Approximate Inverse Banded Matrix Techniques.	J. Supercomput.	2003	DBLP DOI BibTeX RDF	approximate factorization procedures, approximate inverse matrix techniques, computational complexity, preconditioning, rate of convergence, parallel iterative methods, banded matrix
38	Chongyan Gu, Yuqin Dou, Weiqiang Liu 0001, Máire O'Neill	Security Vulnerabilities and Countermeasures for Approximate Circuits.	Approximate Computing	2022	DBLP DOI BibTeX RDF
38	Tingting Zhang, Honglan Jiang, Weiqiang Liu 0001, Fabrizio Lombardi, Leibo Liu, Seok-Bum Ko, Jie Han 0001	Majority Logic-Based Approximate Multipliers for Error-Tolerant Applications.	Approximate Computing	2022	DBLP DOI BibTeX RDF
38	Ke Chen 0018, Weiqiang Liu 0001, Fabrizio Lombardi	Approximate Arithmetic Circuits: Design and Applications.	Approximate Computing	2022	DBLP DOI BibTeX RDF
38	Zhiyuan Xiang, Niyiqiu Liu, Yue Yao, Fan Yang, Cheng Zhuo, Weikang Qian	Approximate Logic Synthesis for FPGA by Decomposition.	Approximate Computing	2022	DBLP DOI BibTeX RDF
38	Mohammadreza Asadikouhanjani, Hao Zhang 0041, Kyunghwan Cho, Young-Jin Park, Seok-Bum Ko	Efficient Approximate DNN Accelerators for Edge Devices: An Experimental Study.	Approximate Computing	2022	DBLP DOI BibTeX RDF
38	Sourav Sanyal, Shubham Negi, Anand Raghunathan, Kaushik Roy 0001	Approximate Computing for Machine Learning Workloads: A Circuits and Systems Perspective.	Approximate Computing	2022	DBLP DOI BibTeX RDF
38	Qiaoyan Yu, Pruthvy Yellu, Landon Buell	Towards Securing Approximate Computing Systems: Security Threats and Attack Mitigation.	Approximate Computing	2022	DBLP DOI BibTeX RDF
38	Bo Liu, Hao Cai, Zhen Wang, Jun Yang	Approximate Computing for Energy-Constrained DNN-Based Speech Recognition.	Approximate Computing	2022	DBLP DOI BibTeX RDF
38	Marzieh Vaeztourshizi, Hassan Afzali-Kusha, Mehdi Kamal, Massoud Pedram	Design Techniques for Approximate Realization of Data-Flow Graphs.	Approximate Computing	2022	DBLP DOI BibTeX RDF
38	Chuan Zhang 0001, Huizheng Wang	Approximate Computation for Baseband Processing.	Approximate Computing	2022	DBLP DOI BibTeX RDF
38	Dur-e-Shahwar Kundi, Ayesha Khalid, Song Bian 0001, Weiqiang Liu 0001	Approximate Computing for Cryptography.	Approximate Computing	2022	DBLP DOI BibTeX RDF
38	You Wang 0002, Hao Cai, Kaili Zhang, Bo Wu, Bo Liu, Deming Zhang, Weisheng Zhao	Spintronic Solutions for Approximate Computing.	Approximate Computing	2022	DBLP DOI BibTeX RDF
38	Hao Zhang 0041, Mohammadreza Asadikouhanjani, Jie Han 0001, Deivalakshmi Subbian, Seok-Bum Ko	Approximate Computing for Efficient Neural Network Computation: A Survey.	Approximate Computing	2022	DBLP DOI BibTeX RDF
38	Zheyu Liu, Qin Li 0016, Xinghua Yang, Fei Qiao	Cross-Level Design of Approximate Computing for Continuous Perception System.	Approximate Computing	2022	DBLP DOI BibTeX RDF
38	Haroon Waris, Chenghua Wang, Weiqiang Liu 0001	An Automated Logic-Level Framework for Approximate Modular Arithmetic Circuits.	Approximate Computing	2022	DBLP DOI BibTeX RDF
38	Marcello Traiola, Bastien Deveautour, Alberto Bosio, Patrick Girard 0001, Arnaud Virazel	Test and Reliability of Approximate Hardware.	Approximate Computing	2022	DBLP DOI BibTeX RDF
38	Junqi Huang, Haider Abbas F. Almurib, Thulasiraman Nandha Kumar, Fabrizio Lombardi	Approximate Computing in Image Compression and Denoising.	Approximate Computing	2022	DBLP DOI BibTeX RDF
38	Ying Wu, Chuangtao Chen 0001, Chenyi Wen, Weikang Qian, Xunzhao Yin, Cheng Zhuo	Approximate Multiplier Design for Energy Efficiency: From Circuit to Algorithm.	Approximate Computing	2022	DBLP DOI BibTeX RDF
38	Ashish Ranjan 0001, Swagath Venkataramani, Shubham Jain, Younghoon Kim, Shankar Ganesh Ramasubramanian, Arnab Raha, Kaushik Roy 0001, Anand Raghunathan	Automatic Synthesis Techniques for Approximate Circuits.	Approximate Circuits	2019	DBLP DOI BibTeX RDF
38	Arnab Raha, Vijay Raghunathan	Approximate Systems: Synergistically Approximating Sensing, Computing, Memory, and Communication Subsystems for Energy Efficiency.	Approximate Circuits	2019	DBLP DOI BibTeX RDF
38	Semeen Rehman, Bharath Srinivas Prabakaran, Walaa El-Harouni, Muhammad Shafique 0001, Jörg Henkel	Heterogeneous Approximate Multipliers: Architectures and Design Methodologies.	Approximate Circuits	2019	DBLP DOI BibTeX RDF
38	Bharath Srinivas Prabakaran, Walaa El-Harouni, Semeen Rehman, Muhammad Shafique 0001	Approximate Multi-Accelerator Tiled Architecture for Energy-Efficient Motion Estimation.	Approximate Circuits	2019	DBLP DOI BibTeX RDF
38	Natalie D. Enright Jerger, Joshua San Miguel	Approximate Cache Architectures.	Approximate Circuits	2019	DBLP DOI BibTeX RDF
38	Jungwook Choi, Swagath Venkataramani	Approximate Computing Techniques for Deep Neural Networks.	Approximate Circuits	2019	DBLP DOI BibTeX RDF
38	Sana Mazahir, Muhammad Kamran Ayub, Osman Hasan, Muhammad Shafique 0001	Probabilistic Error Analysis of Approximate Adders and Multipliers.	Approximate Circuits	2019	DBLP DOI BibTeX RDF
38	Saman Fröhlich, Daniel Große, Rolf Drechsler	Approximate Hardware Generation Using Formal Techniques.	Approximate Circuits	2019	DBLP DOI BibTeX RDF
38	Muhammad Abdullah Hanif, Rehan Hafiz, Muhammad Shafique 0001	Configurable Models and Design Space Exploration for Low-Latency Approximate Adders.	Approximate Circuits	2019	DBLP DOI BibTeX RDF
38	Honglan Jiang, Leibo Liu, Fabrizio Lombardi, Jie Han 0001	Approximate Arithmetic Circuits: Design and Evaluation.	Approximate Circuits	2019	DBLP DOI BibTeX RDF
38	Seogoo Lee, Andreas Gerstlauer	Approximate High-Level Synthesis of Custom Hardware.	Approximate Circuits	2019	DBLP DOI BibTeX RDF
38	Amir Yazdanbakhsh, Gennady Pekhimenko, Hadi Esmaeilzadeh, Onur Mutlu, Todd C. Mowry	Towards Breaking the Memory Bandwidth Wall Using Approximate Value Prediction.	Approximate Circuits	2019	DBLP DOI BibTeX RDF
38	Weng-Fai Wong, Pooja Roy, Rajashi Ray, Nhut-Minh Ho	Compilation and Other Software Techniques Enabling Approximate Computing.	Approximate Circuits	2019	DBLP DOI BibTeX RDF
38	Nam Sung Kim, Ulya R. Karpuzcu	Approximate Ultra-Low Voltage Many-Core Processor Design.	Approximate Circuits	2019	DBLP DOI BibTeX RDF
38	Hokchhay Tann, Soheil Hashemi, Sherief Reda	Lightweight Deep Neural Network Accelerators Using Approximate SW/HW Techniques.	Approximate Circuits	2019	DBLP DOI BibTeX RDF
38	Hokchhay Tann, Soheil Hashemi, Francesco Buttafuoco, Sherief Reda	Approximate Computing for Iris Recognition Systems.	Approximate Circuits	2019	DBLP DOI BibTeX RDF
38	Deepashree Sengupta, Jiang Hu, Sachin S. Sapatnekar	Error Analysis and Optimization in Approximate Arithmetic Circuits.	Approximate Circuits	2019	DBLP DOI BibTeX RDF
38	Soheil Hashemi, Sherief Reda	Approximate Multipliers and Dividers Using Dynamic Bit Selection.	Approximate Circuits	2019	DBLP DOI BibTeX RDF
38	Soheil Hashemi, Hokchhay Tann, Sherief Reda	Approximate Logic Synthesis Using Boolean Matrix Factorization.	Approximate Circuits	2019	DBLP DOI BibTeX RDF
38	Mohsen Imani, Tajana Simunic Rosing	Approximate CPU and GPU Design Using Emerging Memory Technologies.	Approximate Circuits	2019	DBLP DOI BibTeX RDF
37	Yalin Zheng, Changshui Zhang, Xin Yao 0003	Type-I Topological Logic C1I and Approximate Reasoning.	FSKD (1)	2005	DBLP DOI BibTeX RDF
35	Erich L. Kaltofen, Zhengfeng Yang, Lihong Zhi	Approximate greatest common divisors of several polynomials with linearly constrained coefficients and singular polynomials.	ISSAC	2006	DBLP DOI BibTeX RDF	approximate multiple root, approximate polynomial gcd, multivariate polynomial gcd, singular polynomial, linear constraint, symbolic/numeric hybrid method
34	Christof Fetzer, Michel Raynal	Approximate Real-Time Clocks for Scheduled Events.	Symposium on Object-Oriented Real-Time Distributed Computing	2002	DBLP DOI BibTeX RDF	Approximate time, real-time consistency, adaptation, real-time, leader election, virtual time
34	Kaushik Chakrabarti, Minos N. Garofalakis, Rajeev Rastogi, Kyuseok Shim	Approximate query processing using wavelets.	VLDB J.	2001	DBLP DOI BibTeX RDF	Query processing, Wavelet decomposition, Approximate query answers, Data synopses
34	Erich L. Kaltofen, Lihong Zhi	Hybrid symbolic-numeric computation.	ISSAC	2006	DBLP DOI BibTeX RDF	symbolic/numeric hybrid methods
33	Simon Y. Berkovich, Mohammad Inayatullah	Improving approximate matching capabilities for Meta Map Transfer applications.	PPPJ	2004	DBLP DOI BibTeX RDF
33	Surender Baswana, Sandeep Sen	Approximate distance oracles for unweighted graphs in Õ(n2) time.	SODA	2004	DBLP BibTeX RDF
32	Jiaheng Lu, Jialong Han, Xiaofeng Meng 0001	Efficient algorithms for approximate member extraction using signature-based inverted lists.	CIKM	2009	DBLP DOI BibTeX RDF	approximate member extraction, filtration-verification, approximate string matching, incremental computation
32	Pengcheng Zhang, Xin Xu 0001, Chunming Liu, Qiping Yuan	Reinforcement Learning Control of a Real Mobile Robot Using Approximate Policy Iteration.	ISNN (3)	2009	DBLP DOI BibTeX RDF	Approximate policy iteration, Approximate dynamic programming, Reinforcement learning, Mobile robots, Path following
32	Alexander A. Sherstov	Approximate Inclusion-Exclusion for Arbitrary Symmetric Functions.	CCC	2008	DBLP DOI BibTeX RDF	Approximate inclusion/exclusion, approximate degree of Boolean functions, linear-programming duality, Chebyshev polynomials
32	Tjavdar Ivanov, Vladimir Maz'ya, Gunther Schmidt 0002	Boundary layer approximate approximations and cubature of potentials in domains.	Adv. Comput. Math.	1999	DBLP DOI BibTeX RDF	volume potentials, semi-analytic cubature formulae, approximate approximations, approximate multi-resolution, 65N38, 65D32, 65D15
32	Jeffrey S. Beis, David G. Lowe	Shape Indexing Using Approximate Nearest-Neighbour Search in High-Dimensional Spaces.	CVPR	1997	DBLP DOI BibTeX RDF	Approximate nearest-neighbour search, Approximate k-d tree search, Object recognition, High-dimensional indexing, Shape indexing
31	Georgios Zervakis 0001, Iraklis Anagnostopoulos, Hussam Amrouch, Jörg Henkel	Enabling Efficient Inference of Convolutional Neural Networks via Approximation.	Approximate Computing	2022	DBLP DOI BibTeX RDF
31	Amir Sabbagh Molahosseini, Leonel Sousa, Azadeh Alsadat Emrani Zarandi, Hans Vandierendonck	Low-Precision Floating-Point Formats: From General-Purpose to Application-Specific.	Approximate Computing	2022	DBLP DOI BibTeX RDF
31	Qian Xu, Md Tanvir Arafin, Gang Qu 0001	Approximation on Data Flow Graph Execution for Energy Efficiency.	Approximate Computing	2022	DBLP DOI BibTeX RDF
31	Md Tanvir Arafin, Qian Xu, Gang Qu 0001	Voltage Overscaling Techniques for Security Applications.	Approximate Computing	2022	DBLP DOI BibTeX RDF
31	Vladik Kreinovich, Olga Kosheleva, Michael Zakharevich	Z-Numbers: How They Describe Student Confidence and How They Can Explain (and Improve) Laplacian and Schroedinger Eigenmap Dimension Reduction in Data Analysis.	Fuzzy Approaches for Soft Computing and Approximate Reasoning	2021	DBLP DOI BibTeX RDF
31	Punit Rathore, James C. Bezdek, Marimuthu Palaniswami	Fast Cluster Tendency Assessment for Big, High-Dimensional Data.	Fuzzy Approaches for Soft Computing and Approximate Reasoning	2021	DBLP DOI BibTeX RDF
31	Giulianella Coletti	Decision Rules Under Vague and Uncertain Information.	Fuzzy Approaches for Soft Computing and Approximate Reasoning	2021	DBLP DOI BibTeX RDF
31	Óscar Ibáñez, Carmen Campomanes-Álvarez, B. Rosario Campomanes-Álvarez, Rubén Martos, Inmaculada Alemán, Sergio Damas, Oscar Cordón	Forensic Identification by Craniofacial Superimposition Using Fuzzy Set Theory.	Fuzzy Approaches for Soft Computing and Approximate Reasoning	2021	DBLP DOI BibTeX RDF
31	Mika Sato-Ilic	Fuzzy Clustering Models and Their Related Concepts.	Fuzzy Approaches for Soft Computing and Approximate Reasoning	2021	DBLP DOI BibTeX RDF
31	Thierry-Marie Guerra, Miguel Angel Bernal	Control: Advances on Fuzzy Model-Based Observers.	Fuzzy Approaches for Soft Computing and Approximate Reasoning	2021	DBLP DOI BibTeX RDF
31	Francesc Esteva, Lluís Godo, Sandra A. Sandri	A Similarity-Based Three-Valued Modal Logic Approach to Reason with Prototypes and Counterexamples.	Fuzzy Approaches for Soft Computing and Approximate Reasoning	2021	DBLP DOI BibTeX RDF
31	Marcin Detyniecki	Interpolative Reasoning: Valid, Specificity-Gradual and Similarity-Based.	Fuzzy Approaches for Soft Computing and Approximate Reasoning	2021	DBLP DOI BibTeX RDF
31	Marek Z. Reformat	Semantic Web: Graphs, Imprecision and Knowledge Generation.	Fuzzy Approaches for Soft Computing and Approximate Reasoning	2021	DBLP DOI BibTeX RDF
31	Michio Sugeno	The Fuzzy Theoretic Turn.	Fuzzy Approaches for Soft Computing and Approximate Reasoning	2021	DBLP DOI BibTeX RDF
31	Humberto Bustince, Radko Mesiar, Graçaliz Pereira Dimuro, Javier Fernández 0002, Benjamín R. C. Bedregal	The Evolution of the Notion of Overlap Functions.	Fuzzy Approaches for Soft Computing and Approximate Reasoning	2021	DBLP DOI BibTeX RDF
31	Fernando A. C. Gomide, André P. Lemos, Walmir M. Caminhas	Evolving Systems.	Fuzzy Approaches for Soft Computing and Approximate Reasoning	2021	DBLP DOI BibTeX RDF
31	Charles Tijus	Analogy.	Fuzzy Approaches for Soft Computing and Approximate Reasoning	2021	DBLP DOI BibTeX RDF
31	Luis Magdalena	Fuzzy Systems Interpretability: What, Why and How.	Fuzzy Approaches for Soft Computing and Approximate Reasoning	2021	DBLP DOI BibTeX RDF
31	Olivier Strauss, Kevin Loquin, Florentin Kucharczak	On Maxitive Image Processing.	Fuzzy Approaches for Soft Computing and Approximate Reasoning	2021	DBLP DOI BibTeX RDF
31	Anne Laurent	Graduality in Data Sciences: Gradual Patterns.	Fuzzy Approaches for Soft Computing and Approximate Reasoning	2021	DBLP DOI BibTeX RDF
31	Ronald R. Yager	An Introduction to Linguistic Summaries.	Fuzzy Approaches for Soft Computing and Approximate Reasoning	2021	DBLP DOI BibTeX RDF
31	Irina Perfilieva	F-Transform Representation of Nonlocal Operators with Applications to Image Restoration.	Fuzzy Approaches for Soft Computing and Approximate Reasoning	2021	DBLP DOI BibTeX RDF
31	Dan A. Ralescu, Anca L. Ralescu	Abstract Models for Systems Identification.	Fuzzy Approaches for Soft Computing and Approximate Reasoning	2021	DBLP DOI BibTeX RDF
31	Olivier Pivert, Grégory Smits	Fuzzy Extensions of Databases.	Fuzzy Approaches for Soft Computing and Approximate Reasoning	2021	DBLP DOI BibTeX RDF
31	Szilvia Nagy, Ferenc Lilik, Brigita Sziová, Melinda Kovács, László T. Kóczy	On the Applicability of Fuzzy Rule Interpolation and Wavelet Analysis in Colorectal Image Segment Classification.	Fuzzy Approaches for Soft Computing and Approximate Reasoning	2021	DBLP DOI BibTeX RDF
31	Didier Dubois, Henri Prade	Membership Functions.	Fuzzy Approaches for Soft Computing and Approximate Reasoning	2021	DBLP DOI BibTeX RDF
31	Alexander Dockhorn, Chris Saxton, Rudolf Kruse	Association Rule Mining for Unknown Video Games.	Fuzzy Approaches for Soft Computing and Approximate Reasoning	2021	DBLP DOI BibTeX RDF
31	María T. Lamata, David A. Pelta, José Luis Verdegay Galdeano	The Role of the Context in Decision and Optimization Problems.	Fuzzy Approaches for Soft Computing and Approximate Reasoning	2021	DBLP DOI BibTeX RDF
31	Lukás Sekanina, Zdenek Vasícek, Vojtech Mrazek	Automated Search-Based Functional Approximation for Digital Circuits.	Approximate Circuits	2019	DBLP DOI BibTeX RDF
31	Muhammad Abdullah Hanif, Muhammad Usama Javed, Rehan Hafiz, Semeen Rehman, Muhammad Shafique 0001	Hardware-Software Approximations for Deep Neural Networks.	Approximate Circuits	2019	DBLP DOI BibTeX RDF
31	Ravi Nair	Models for energy-efficient approximate computing.	ISLPED	2010	DBLP DOI BibTeX RDF	energy-efficient computing, prediction systems, approximate computing
31	Lianwen Wang	Approximate controllability results of semilinear integrodifferential equations with infinite delays.	Sci. China Ser. F Inf. Sci.	2009	DBLP DOI BibTeX RDF	approximate controllability, semilinear control systems, integrodifferential equations, infinite delays
31	Joshua Spiegel, Neoklis Polyzotis	TuG synopses for approximate query answering.	ACM Trans. Database Syst.	2009	DBLP DOI BibTeX RDF	approximate query processing, selectivity estimation, Data synopses
31	Xiangyang Wang, Wanggen Wan, Xiaoqing Yu	Rough set approximate entropy reducts with order based particle swarm optimization.	GEC Summit	2009	DBLP DOI BibTeX RDF	approximate entropy reducts, hybrid algorithm., order-based particle swarm optimization, rough set, particle swarm optimization
31	Graham Cormode, Minos N. Garofalakis	Approximate continuous querying over distributed streams.	ACM Trans. Database Syst.	2008	DBLP DOI BibTeX RDF	Continuous distributed monitoring, approximate query processing, data synopses, data stream algorithms
31	Liang Jin, Chen Li 0001, Rares Vernica	SEPIA: estimating selectivities of approximate string predicates in large Databases.	VLDB J.	2008	DBLP DOI BibTeX RDF	SEPIA, Approximate, Estimation, Selectivity, String
31	Rohit Gupta 0003, Gang Fang, Blayne Field, Michael S. Steinbach, Vipin Kumar 0001	Quantitative evaluation of approximate frequent pattern mining algorithms.	KDD	2008	DBLP DOI BibTeX RDF	approximate frequent itemsets, error tolerance, quantitative evaluation, association analysis
31	Tomás Skopal	Unified framework for fast exact and approximate search in dissimilarity spaces.	ACM Trans. Database Syst.	2007	DBLP DOI BibTeX RDF	approximate and exact search, Similarity retrieval
31	Surender Baswana, Sandeep Sen	Approximate distance oracles for unweighted graphs in expected O(n2) time.	ACM Trans. Algorithms	2006	DBLP DOI BibTeX RDF	Approximate distance oracles, distance queries, shortest paths, distances, spanners
31	Minkoo Seo, Sanghyun Park 0003, Jung-Im Won	CSI: Clustered Segment Indexing for Efficient Approximate Searching on the Secondary Structure of Protein Sequences.	ISMIS	2005	DBLP DOI BibTeX RDF	Secondary structure of proteins, Indexing method, Approximate searching