Yong Meng Teo
Email Address
dcsteoym@nus.edu.sg
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Publication CODES: An integrated approach to composable modeling and simulation(2008) Teo, Y.M.; Szabo, C.; COMPUTER SCIENCEIn component-based simulation, models developed in different locations and for specific purposes can be selected and assembled in various combinations to meet diverse user requirements. This paper proposes CODES (COmposable Discrete-Event scalable Simulation), an approach to component-based modeling and simulation that supports model reuse across multiple application domains. A simulation component is viewed by the modeller as a black box with an in- and/or out-channel. The attributes and behavior of the component abstracted as a meta-component are described using COML (COmponent Markup Language), a markup language we propose for representing simulation components. The integrated approach, supported by a proposed COSMO (COmponent-oriented Simulation and Modeling Ontology) ontology, consists of four main steps. Component discovery returns a set of syntactically valid model components. Syntactic composability is determined by our proposed EBNF syntactic composition rules. Validation of semantic composability is performed using our proposed data and behavior alignment algorithms. The semantically valid simulation component is subsequently stored in a model repository for reuse. As proof of concept, we discuss a prototype implementation of the CODES framework using queueing system as an application domain example. © 2008 IEEE.Publication Effect of event orderings on memory requirement in parallel simulation(2001) Teo, Y.M.; Onggo, B.S.S.; Tay, S.C.; CTR FOR REM IMAGING,SENSING & PROCESSING; COMPUTER SCIENCEA new formal approach based on partial order set (poset) theory is proposed to analyze the space requirement of discrete-event parallel simulation. We divide the memory required by a simulation problem into memory to model the states of the real-world system, memory to maintain a list of future event occurrences, and memory required to implement the event synchronization protocol. We establish the relationship between poset theory and event orderings in simulation. Based on our framework, we analyze the space requirement using an open and a closed system as examples. Our analysis shows that apart from problem size and traffic intensity that affects the memory requirement, event ordering is an important factor that can be analyzed before implementation. In an open system, a weaker event ordered simulation requires more memory than strong ordering. However, the memory requirement is constant and independent of event ordering in closed systems.Publication An approach to achieve message efficient early-stopping uniform consensus protocols(2004) Wang, X.; Cao, J.; Teo, Y.M.; SINGAPORE-MIT ALLIANCE; COMPUTER SCIENCEExisting consensus protocols for synchronous distributed systems concentrate on the lower bound on the number of rounds required for achieving consensus. This paper proposes an approach to reduce the message complexity of some uniform consensus protocols significantly while achieving the same lower bound in which for any t-resilient consensus protocol only t + 1 processes engaging in sending messages in each round.Publication Supporting parallel computing on a distributed object architecture(2001) Wang, C.; Teo, Y.M.; COMPUTER SCIENCEThe availability of high-speed networks and increasingly powerful commodity microprocessors is making the usage of clusters, or networks, of computers an appealing platform for cost effective parallel computing. However, the ease of developing efficient high-performance parallel software to exploit these platforms presents a major challenge. Advances in distributed object software technology have made the management of distributed computing resources easier than before. This also brings many benefits for parallel computing. Firstly, distributed object technology facilitates the encapsulating of parallel computing resources into a uniform model despite their differences in implementations that are based on different languages executing on different platforms. Secondly, mature object-oriented analysis, design method, as well as component idea embodied in distributed object technology can enhance the reusability of parallel software. To support parallel computing in a distributed object-based computing platform, a uniform high performance distributed object architecture layer is necessary. In this paper, we propose a distributed object-based framework called DoHPC to support parallel computing on distributed object architectures. We present the use of dependence analysis technique to exploit intra-object parallelism and an interoperability model for supporting distributed parallel objects. Experimental results on a Fujitsu AP3000 workstation cluster consisting of a cluster of 32 UltraSPARC workstations show that the implementation of inter-object parallelism on a workstation cluster environment is efficient. With intra-object parallel computation speedup efficiency is greater than 90% and with overhead of less than 10% for large problem, and the interoperability model improves speedup by 20%.Publication An expressive framework for verifying deadlock freedom(2013) Le, D.-K.; Chin, W.-N.; Teo, Y.-M.; COMPUTER SCIENCEThis paper presents an expressive specification and verification framework for ensuring deadlock freedom of shared-memory concurrent programs that manipulate locks. We introduce a novel delayed lockset checking technique to guarantee deadlock freedom of programs with interactions between thread and lock operations. With disjunctive formulae, we highlight how an abstraction based on precise lockset can be supported in our framework. By combining our technique with locklevels, we form a unified formalism for ensuring deadlock freedom from (1) double lock acquisition, (2) interactions between thread and lock operations, and (3) unordered locking. The proposed framework is general, and can be integrated with existing specification logics such as separation logic. Specifically, we have implemented this framework into a prototype tool, called ParaHIP, to automatically verify deadlock freedom and correctness of concurrent programs against user-supplied specifications. © 2013 Springer International Publishing.Publication Performance analysis of parallel simulation on distributed systems(1996) Teo, Y.M.; Tay, S.C.; PHYSICS; INFORMATION SYSTEMS & COMPUTER SCIENCEThis paper presents an analytical model to evaluate the performance of parallel simulation on distributed computing platforms. The proposed model is formalized by two important time components in parallel and distributed processing: computation time and communication time. A conservative parallel simulation of multistage interconnection networks is used as an example in our analytical model. Performance metrics such as elapsed time, speedup and simulation bandwidth associated with different schemes for partitioning/mapping parallel simulation onto distributed processors are evaluated. Our mathematical analysis identifies the major constituents of simulation overheads in these mapping strategies necessary for improving parallel simulation efficiency. We also show that a perfectly balanced workload distribution may not necessarily translate into better performance. On the contrary, we have shown that a balanced mapping of workload may increase communication overheads resulting in a longer simulation elapsed time. Our performance model has been validated against implementation results from a parallel simulation model. The analytical framework is also practical to evaluate the runtime efficiency of other simulation applications which are based on the conservative paradigm. © 1996 The British Computer Society,.Publication GLAD: A system for developing and deploying large-scale bioinformatics grid(2005) Teo, Y.-M.; Wang, X.; Ng, Y.-K.; SINGAPORE-MIT ALLIANCE; COMPUTER SCIENCEMotivation: Grid computing is used to solve large-scale bioinformatics problems with gigabytes database by distributing the computation across multiple platforms. Untill now in developing bioinformatics grid applications, it is extremely tedious to design and implement the component algorithms and parallelization techniques for different classes of problems, and to access remotely located sequence database files of varying formats across the grid. In this study, we propose a grid programming toolkit, GLAD (Grid Life sciences Applications Developer), which facilitates the development and deployment of bioinformatics applications on a grid. Results: GLAD has been developed using ALiCE (Adaptive scaLable Internet-based Computing Engine), a Java-based grid middleware, which exploits the task-based parallelism. Two bioinformatics benchmark applications, such as distributed sequence comparison and distributed progressive multiple sequence alignment, have been developed using GLAD. © The Author 2004. Published by Oxford University Press. All rights reserved.Publication An objective-based approach for semantic validation of emergence in component-based simulation models(2012) Szabo, C.; Teo, Y.M.; COMPUTER SCIENCEComponent-based models have been shown to exhibit emergent properties but despite a plethora of definitions and methods to identify emergence, practical semantic validation approaches remain a key challenge. This paper proposes an objective-based approach for semantic validation of emergence in component-based simulation models. In contrast to current methods, our approach describes model components in terms of what they achieve rather than how they achieve it, and we exploit reconstruct ability analysis in the validation of emergence. This has the advantage of reducing the number of attributes used to describe each component, and thus facilitates the application of more rigorous mathematical formalisms for emergence validation. As an example, we detail how this methodology is integrated into the life-cycle of our component-based model development framework. © 2012 IEEE.Publication The time and energy efficiency of modern multicore systems(Elsevier BV, 2019-08-01) Loghin, D; Teo, YM; Dr Dumitrel Loghin; DEPARTMENT OF COMPUTER SCIENCE© 2019 Elsevier B.V. With the increasing adoption of homogeneous and heterogeneous shared-memory multicore systems, we aim to improve the understanding of their time and energy performance by extending the classic speedup laws proposed by Amdahl and Gustafson. We derive speedup equations for heterogeneous systems and introduce energy savings models for both homogeneous and heterogeneous multicores. These models use two key parameters, (i)the active power fraction (APF)of a core which represents the ratio between the core's average active power and the power of the idle system, and (ii)the inter-core speedup (ICS)representing the difference in speed among different types of cores in a heterogeneous system. Using both modeling and measurements, we show that energy savings are achievable, but limited by the APF on systems with large core counts and by both the APF and workload's sequential fraction on systems with low core counts. Our models are validated against measurements on modern multicore systems including two homogeneous servers with 48 cores which represent both traditional brawny x86/64 and emerging wimpy ARM nodes, and two heterogeneous wimpy systems with ARM big.LITTLE and NVIDIA Denver cores, respectively.Publication Multi-attribute range queries on read-only DHT(2006) March, V.; Teo, Y.M.; COMPUTER SCIENCER-DHT is a class of DHT whereby each node supports "read-only" accesses to its key-value pairs, but does not allow key-value pairs belonging to other nodes to be written on it. Recently, supporting efficient multi-attribute range queries on DHT has been an active area of research. This paper presents the design and evaluation of Midas, an approach to support multi-attribute range queries on R-DHT. Midas indexes multi-attribute resources using a d-to-one mapping scheme, and optimizes a range query by searching only for available keys. Our simulation results show that Midas on R-DHT achieves a higher lookup resiliency than conventional DHT, and it has a lower cost of query processing when the query selectivity is much larger than the number of query results. © 2006 IEEE.