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    An approximation algorithm for computing the visibility region of a point on a terrain and visibility testing

    , Article VISAPP 2014 - Proceedings of the 9th International Conference on Computer Vision Theory and Applications ; Vol. 3, issue , January , 2014 , p. 699-704 Alipour, S ; Ghodsi, M ; Gudukbay, U ; Golkari, M ; Sharif University of Technology
    Given a terrain and a query point p on or above it, we want to count the number of triangles of terrain that are visible from p. We present an approximation algorithm to solve this problem. We implement the algorithm and then we run it on the real data sets. The experimental results show that our approximation solution is very close to the real solution and compare to the other similar works, the running time of our algorithm is better than their algorithm. The analysis of time complexity of algorithm is also presented. Also, we consider visibility testing problem, where the goal is to test whether p and a given triangle of train are visible or not. We propose an algorithm for this problem... 

    A safe stopping protocol to enable reliable reconfiguration for component-based distributed systems

    , Article 6th International Conference on Fundamentals of Software Engineering, FSEN 2015, 22 April 2015 through 24 April 2015 ; Volume 9392 , November , 2015 , Pages 100-109 ; 03029743 (ISSN) ; 9783319246437 (ISBN) Ghafari, M ; Heydarnoori, A ; Haghighi, H ; Sharif University of Technology
    Springer Verlag  2015
    Despite the need for change, highly available software systems cannot be stopped to perform changes because disruption in their services may consequent irrecoverable losses. Current work on runtime evolution are either too disruptive, e.g., "blackouts" in unnecessary components in the quiescence criterion approach or presume restrictive assumptions such as the "black-box design" in the tranquility approach. In this paper, an architecture-based approach, called SAFER, is proposed which provides a better timeliness by relaxing any precondition required to start reconfiguration. We demonstrate the validity of the SAFER through model checking and a realization of the approach on a component... 

    Improved algorithms for edit distance and LCS: Beyond worst case

    , Article 31st Annual ACM-SIAM Symposium on Discrete Algorithms, SODA 2020, 5 January 2020 through 8 January 2020 ; Volume 2020-January , 2020 , Pages 1601-1620 Boroujeni, M ; Seddighin, M ; Seddighin, S ; ACM Special Interest Group on Algorithms and Computation Theory (SIGACT); SIAM Activity Group on Discrete Mathematics ; Sharif University of Technology
    Association for Computing Machinery  2020
    Edit distance and longest common subsequence are among the most fundamental problems in combinatorial optimization. Recent developments have proven strong lower bounds against subquadratic time solutions for both problems. Moreover, the best approximation factors for subquadratic time solutions have been limited to 3 for edit distance and super constant for longest common subsequence. Improved approximation algorithms for these problems1 are some of the biggest open questions in combinatorial optimization. In this work, we present improved algorithms for both edit distance and longest common subsequence. The running times are truly subquadratic, though we obtain 1 + o(1) approximate... 

    Improved MPC algorithms for Edit distance and Ulam distance

    , Article IEEE Transactions on Parallel and Distributed Systems ; Volume 32, Issue 11 , 2021 , Pages 2764-2776 ; 10459219 (ISSN) Boroujeni, M ; Ghodsi, M ; Seddighin, S ; Sharif University of Technology
    IEEE Computer Society  2021
    Edit distance is one of the most fundamental problems in combinatorial optimization to measure the similarity between strings. Ulam distance is a special case of edit distance where no character is allowed to appear more than once in a string. Recent developments have been very fruitful for obtaining fast and parallel algorithms for both edit distance and Ulam distance. In this work, we present an almost optimal MPC (massively parallel computation) algorithm for Ulam distance and improve MPC algorithms for edit distance. Our algorithm for Ulam distance is almost optimal in the sense that (1) the approximation factor of our algorithm is $1+epsilon$1+ϵ, (2) the round complexity of our... 

    Hardware Trojan Detection Based on Logical Testing

    , Ph.D. Dissertation Sharif University of Technology Bazzazi, Amin (Author) ; Manzuri, Mohmmad Taghi (Supervisor) ; Hemmatyar, Ali Mohammad Afshin (Supervisor)
    In recent years, hardware Trojans (HTs) have become one of the main challenging concerns within the chain of manufacturing digital integrated circuit chips. Because of their diversity in chips, HTs are difficult to detect and locate. This thesis attempted to propose a new improved method for detection and localization of HTs based on the real-time logical values of nodes. The algorithm extracts the nodes with special attributes. At the next stage, the nodes with the greatest similarity in terms of logical value are selected as targets. Depending on the size of the circuit, the extraction continues until a sufficient number of similar nodes has been selected. The logical relationship between... 

    Improved algorithms for partial curve matching

    , Article Algorithmica ; Vol. 69, issue. 3 , 2014 , p. 641-657 Maheshwari, A ; Sack, J. R ; Shahbaz, K ; Zarrabi-Zadeh, H ; Sharif University of Technology
    We revisit the problem of deciding whether a given curve resembles some part of a larger curve under a fixed Fréchet distance, achieving a running time of O(nm), for n and m being the number of segments in the two curves. This improves the long-standing result of Alt and Godau by an O(log(nm)) factor. Our solution is based on constructing a simple data structure which we call free-space map. Using this data structure, we obtain improved algorithms for several variants of the Fréchet distance problem, including the Fréchet distance between two closed curves, and the so-called minimum/maximum walk problems. We also improve the map matching algorithm of Alt et al. for the particular case in... 

    Improved algorithms for partial Curve matching

    , Article Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 5 September 2011 through 9 September 2011 ; Volume 6942 LNCS , September , 2011 , Pages 518-529 ; 03029743 (ISSN) ; 9783642237188 (ISBN) Maheshwari, A ; Sack, J. R ; Shahbaz, K ; Zarrabi Zadeh, H ; Sharif University of Technology
    Back in 1995, Alt and Godau gave an efficient algorithm for deciding whether a given curve resembles some part of a larger curve under a fixed Fréchet distance, achieving a running time of O(nm log(nm)), for n and m being the number of segments in the two curves, respectively. We improve this long-standing result by presenting an algorithm that solves this decision problem in O(nm) time. Our solution is based on constructing a simple data structure which we call free-space map. Using this data structure, we obtain improved algorithms for several variants of the Fréchet distance problem, including the Fréchet distance between two closed curves, and the so-called minimum/maximum walk problems.... 

    Solving graph coloring problems using cultural algorithms

    , Article Proceedings of the 24th International Florida Artificial Intelligence Research Society, FLAIRS - 24, 18 May 2011 through 20 May 2011 ; May , 2011 , Pages 3-8 ; 9781577355014 (ISBN) Abbasian, R ; Mouhoub, M ; Jula, A ; Sharif University of Technology
    In this paper, we combine a novel Sequential Graph Coloring Heuristic Algorithm (SGCHA) with a non-systematic method based on a cultural algorithm to solve the graph coloring problem (GCP). The GCP involves finding the minimum number of colors for coloring the graph vertices such that adjacent vertices have distinct colors. In our solving approach, we first use an estimator which is implemented with SGCHA to predict the minimum colors. Then, in the non-systematic part which has been designed using cultural algorithms, we improve the prediction. Various components of the cultural algorithm have been implemented to solve the GCP with a self adaptive behavior in an efficient manner. As a result... 

    A real-time clearance-based approach for motion planning of mobile robots

    , Article 7th IEEE International Conference on Cognitive Informatics, ICCI 2008, Stanford University, CA, 14 August 2008 through 16 August 2008 ; 2008 , Pages 394-401 ; 9781424425389 (ISBN) Naderan Tahan, M ; Iraji, R ; Manzuri Shalmani, M. T ; Sharif University of Technology
    In this paper, two different important quality metrics, clearance and execution time, for motion planning of mobile robots are studied. Then a new approach, called Clearance-Based Probabilistic Roadmap Method (CBPRM (c)), is proposed which in contrast to VV(c) method, Visibility-Voronoi with clearance c, beside satisfaction of a predefined clearance is very efficient in running time. This provides the CBPRM (c) to be applicable in dynamic environments which require realtime approaches. Experiments showed that the CBPRM(c) is able to generate paths with very low execution time considering determined clearance. © 2008 IEEE  

    Synthesis of Reo circuits for implementation of component-connector automata specifications

    , Article 7th International Conference on Coordination Models and Languages, COORDINATION 2005, Namur, 20 April 2005 through 23 April 2005 ; Volume 3454 , 2005 , Pages 236-251 ; 03029743 (ISSN) Arbab, F ; Baier, C ; De Boer, F ; Rutten, J ; Sirjani, M ; Sharif University of Technology
    Springer Verlag  2005
    Composition of a concurrent system out of components involves coordination of their mutual interactions. In component-based construction, this coordination becomes the responsibility of the glue-code language and its underlying run-time middle-ware. Reo offers an expressive glue-language for construction of coordinating component connectors out of primitive channels. In this paper we consider the problem of synthesizing Reo coordination code from a specification of a behavior as a relation on scheduled-data streams. The specification is given as a constraint automaton that describes the desired input/output behavior at the ports of the components. The main contribution in this paper is an... 

    Reconfigurable Architecture For Cryptanalysis Applications

    , M.Sc. Thesis Sharif University of Technology Noshadravan, Mohammad Reza (Author) ; Jahangir, Amir Hossein (Supervisor)
    Nowadays, the significance of securing data and information is undeniable. Cryptography is being used to provide data security. In addition, cryptanalysis is required to evaluate the effectiveness of cryptography methods, and hence, it is an essential concept for securing data. In general, the cryptography functions shall be designed in a way to impose a high load of time-intensive operations to prevent an adversary from accessing the main data from the encrypted data. As a result, cryptography and cryptanalysis algorithms need high performance computations. So far, a number of methods have been proposed to support the required performance. These methods include: distributed computing and... 

    Hyperion: a wearable augmented reality system for text extraction and manipulation in the air

    , Article Proceedings of the 8th ACM Multimedia Systems Conference, MMSys 2017, 20 June 2017 through 23 June 2017 ; 2017 , Pages 284-295 ; 9781450350020 (ISBN) Chatzopoulos, D ; Bermejo, C ; Huang, Z ; Butabayeva, A ; Zheng, R ; Golkarifard, M ; Hui, P ; Sharif University of Technology
    We develop Hyperion a Wearable Augmented Reality (WAR) system based on Google Glass to access text information in the ambient environment. Hyperion is able to retrieve text content from users' current view and deliver the content to them in different ways according to their context.We design four work modalities for different situations that mobile users encounter in their daily activities. In addition, user interaction interfaces are provided to adapt to different application scenarios. Although Google Glass may be constrained by its poor computational capabilities and its limited battery capacity, we utilize code-level offloading to companion mobile devices to improve the runtime... 

    Hardware Trojan detection and localization based on local detectors

    , Article Turkish Journal of Electrical Engineering and Computer Sciences ; Volume 26, Issue 3 , 2018 , Pages 1403-1416 ; 13000632 (ISSN) Bazzazi, A ; Manzuri Shalmani, M. T ; Hemmatyar, A. M. A ; Sharif University of Technology
    Turkiye Klinikleri Journal of Medical Sciences  2018
    Hardware Trojans are one of the serious threats with detrimental, irreparable effects on the functionality, security, and performance of digital integrated circuits. It is difficult to detect Trojans because of their diversity in size and performance. While the majority of current methods focus on Trojan detection during chip testing, run-time techniques can be employed to gain unique advantages. This paper proposes a method based on the online scalable detection technique, which eliminates the need for a reference chip. Involving local detectors, this technique assesses the variations in the logical values of each node to find out whether there are Trojans. This method excludes time and... 

    Toward on-chip network security using runtime isolation mapping

    , Article ACM Transactions on Architecture and Code Optimization ; Volume 16, Issue 3 , 2019 ; 15443566 (ISSN) Bayat Sarmadi, M ; Sarmadi, S. B ; Hessabi, S ; Sharif University of Technology
    Association for Computing Machinery  2019
    Many-cores execute a large number of diverse applications concurrently. Inter-Application interference can lead to a security threat as timing channel attack in the on-chip network. A non-interference communication in the shared on-chip network is a dominant necessity for secure many-core platforms to leverage the concepts of the cloud and embedded system-on-chip. The current non-interference techniques are limited to static scheduling and need router modification at micro-Architecture level. Mapping of applications can effectively determine the interference among applications in on-chip network. In this work, we explore non-interference approaches through run-Time mapping at software and... 

    Focus on What is Needed: Area and Power Efficient FPGAs Using Turn-Restricted Switch Boxes

    , Article 18th IEEE Computer Society Annual Symposium on VLSI, ISVLSI 2019, 15 July 2019 through 17 July 2019 ; Volume 2019-July , 2019 , Pages 615-620 ; 21593469 (ISSN) ; 9781538670996 (ISBN) Serajeh Hassani, F ; Sadrosadati, M ; Pointner, S ; Wille, R ; Sarbazi Azad, H ; Technical Committee on VLSI (TCVLSI) of IEEE Computer Society (CS) ; Sharif University of Technology
    IEEE Computer Society  2019
    Field-Programmable Gate Arrays (FPGAs) employ a significant amount of SRAM cells in order to provide a flexible routing architecture. While this flexibility allows for a rather easy realization of arbitrary functionality, the respectively required cells significantly increase the area and power consumption of the FPGA. At the same time, it can be observed that full routing flexibility is frequently not needed in order to efficiently realize the desired functionality. In this work, we are proposing an FPGA realization which focuses on what is needed and realizes only a subset of the possible routing options using what we call Turn-Restricted Switch-Boxes. While this may yield a slight... 

    Supporting non-contiguous processor allocation in mesh-based chip multiprocessors using virtual point-to-point links

    , Article IET Computers and Digital Techniques ; Vol. 6, issue. 5 , September , 2012 , pp. 302-317 ; ISSN: 17518601 Asadinia, M ; Modarressi, M ; Sarbazi-Azad, H ; Sharif University of Technology
    In this study, the authors propose a processor allocation mechanism for run-time assignment of a set of communicating tasks of input applications onto the processing nodes of a chip multiprocessor, when the arrival order and execution lifetime of the input applications are not known a priori. This mechanism targets the on-chip communication and aims to reduce the power and latency of the network-on-chip employed as the communication infrastructure. In this work, the authors benefit from the advantages of non-contiguous processor allocation mechanisms, by allowing the tasks of the input application mapped onto disjoint regions (submeshes) and then virtually connecting them by bypassing the... 

    A new simple method for analysing of thermal noise in switched-capacitor filters

    , Article International Journal of Electronics ; Volume 99, Issue 12 , Feb , 2012 , Pages 1729-1737 ; 00207217 (ISSN) Rashtian, M ; Hemmatyar, A. M. A ; Hashemipour, O ; Sharif University of Technology
    Thermal noise is one of the most important challenges in analogue integrated circuits design. This problem is more crucial in switched-capacitor (SC) filters due to the aliasing effect of wide-band thermal noise. In this article, a new simple method is proposed for estimating the power spectrum density of output thermal noise in SC filters, which have acceptable accuracy and short running time. In the proposed method, first using HSPICE simulator, accurate value of accumulated sampled noise on sampler capacitors in each clock state is achieved. Next, using difference equations of the SC filter, frequency response of the SC filter is shaped by time domain analysis. Based on the proposed... 

    Coordinated actors for reliable self-adaptive systems

    , Article Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 19 October 2016 through 21 October 2016 ; Volume 10231 LNCS , 2017 , Pages 241-259 ; 03029743 (ISSN) ; 9783319576657 (ISBN) Bagheri, M ; Akkaya, I ; Khamespanah, E ; Khakpour, N ; Sirjani, M ; Movaghar, A ; Lee, E. A ; Khosravi, R ; Kouchnarenko, O ; Sharif University of Technology
    Self-adaptive systems are systems that automatically adapt in response to environmental and internal changes, such as possible failures and variations in resource availability. Such systems are often realized by a MAPE-K feedback loop, where Monitor, Analyze, Plan and Execute components have access to a runtime model of the system and environment which is kept in the Knowledge component. In order to provide guarantees on the correctness of a self-adaptive system at runtime, the MAPE-K feedback loop needs to be extended with assurance techniques. To address this issue, we propose a coordinated actor-based approach to build a reusable and scalable model@runtime for self-adaptive systems in the... 

    Lightweight secure IP address auto-configuration based on VASM

    , Article Proceedings - International Conference on Advanced Information Networking and Applications, AINA, 26 May 2009 through 29 May 2009, Bradford ; 2009 , Pages 176-180 ; 1550445X (ISSN); 9780769536392 (ISBN) Tajamolian, M ; Taghiloo, M ; Tajamolian, M ; Sharif University of Technology
    Mobile ad hoc networks allow to create very dynamic communication systems, which are independent from any fixed infrastructure. One of the most important issues regarding the management of an ad hoc network is the configuration of the system according to the way users move. Since a centralized control structure does not exist, we need to determine how the IP addresses must be assigned to the nodes in the network. In this paper we add a security mechanism to VASM protocol based on zero knowledge approach. A hash function has very low running time. So this so this scheme is very light-weight. The VASM protocol uses coordinate value of point in main address sheet for generating addresses. The... 

    A formal approach for debugging arithmetic circuits

    , Article IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems ; Volume 28, Issue 5 , 2009 , Pages 742-754 ; 02780070 (ISSN) Sarbishei, O ; Tabandeh, M ; Alizadeh, B ; Fujita, M ; Sharif University of Technology
    This paper presents a novel automatic debugging algorithm for a postsynthesis combinational arithmetic circuit. The approach is robust under wide varieties of arithmetic circuit architectures and design optimizations. The debugging algorithm in this paper consists of three phases of partial product initialization, xor extraction, and carry-signal mapping. The run-time complexity of conventional carry-signal-mapping algorithms, such as the approach described by Stoffel and Kunz, is exponential. However, in the proposed algorithm, by making use of some important design issues, we categorize the extracted xors into half/full-adders to make a very fast debugging algorithm. This approach is...