Wentong Cai

Nanyang Technological University, School of Computer Engineering, Faculty Member

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Papers by Wentong Cai

A cost calculus for parallel functional programming

Journal of Parallel and Distributed Computing, Jan 1, 1995

Building a cost calculus for a parallel program development environment is di cult because of the... more Building a cost calculus for a parallel program development environment is di cult because of the many degrees of freedom available in parallel implementations, and because of di culties with compositionality. We present a strategy for building cost calculi for skeleton-based programming languages which can be used for derivational software development and which deals in a pragmatic way with the di culties of composition. The approach is illustrated for the Bird-Meertens theory of lists, a parallel functional language with an associated equational transformation system.

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Transparent adaptation of single-user applications for multi-user real-time collaboration

ACM Transactions on …, Jan 1, 2006

Single-user interactive computer applications are pervasive in our daily lives and work. Leveragi... more

An auto-adaptive dead reckoning algorithm for distributed interactive simulation

pads, Jan 1, 1999

This paper describes a new, auto-adaptive algorith,m for dead reckoning in DIS. In general dead-r... more This paper describes a new, auto-adaptive algorith,m for dead reckoning in DIS. In general dead-reckoning algorithms use a fixed threshold to control the extmpolation errors. Since a fixed threshold cannot adequately han,dle the dynamic relationships between moving entities, a multi-level threshold scheme is proposed. The definition of threshold levels is based on the concepts of area of interest (AOI) and sensitive region (SR), and the levels of threshold are adaptively adjusted based on the relative distance between entities during the simv& tion. Various experiments were conducted. The results

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Distributed Supply Chain Simulation Across Enterprise Boundaries

… Conference Proceedings, 2000. …, Jan 1, 2000

The effective practice of supply chain management (SCM) is crucial to improve corporations' compe... more The effective practice of supply chain management (SCM) is crucial to improve corporations' competitive advantage. Many corporations have built simulation models to facilitate the application of simulation in designing, evaluating, and optimizing their supply chain. Traditionally, a supply chain involves only a single enterprise with multiple facilities and distribution centers. Hence, sharing of detailed simulation models is not a problem in this scenario. But in recent years, the scope of SCM has evolved to cross the enterprise boundaries. Applying simulation in designing, evaluating, and optimizing the supply chain becomes more difficult since the participating corporations might not be willing to share their simulation models with partners. In this paper, distributed simulation techniques are presented as an enabling technology that allows corporations to construct a cross enterprise simulation while hiding model details within the enterprise. This can be realized by either building the simulation on top of the Runtime Infrastructure of the High Level Architecture or building the simulation on top of a customized distributed discrete event simulation protocol. These alternative approaches are compared in terms of their performance and interoperability. The comparison of the performance is done through a benchmarking test of a semiconductor supply chain model.

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Time-space consistency in large-scale distributed virtual environments

ACM Transactions on Modeling …, Jan 1, 2004

Maintaining a consistent view of the simulated world among different simulation nodes is a fundam... more Maintaining a consistent view of the simulated world among different simulation nodes is a fundamental problem in large scale distributed virtual environments (DVEs). In this paper, we characterize this problem by quantifying the time-space inconsistency in a DVE. To this end, a metric is defined to measure the time-space inconsistency in a DVE. One major advantage of the metric is that it may be estimated based on some characteristic parameters of a DVE, such as clock asynchrony, message transmission delay, the accuracy of the dead reckoning algorithm, the kinetics of the moving entity and human factors. Thus the metric can be used to evaluate the time-space consistency property of a DVE without the actual execution of the DVE application, which is especially useful in the design stage of a DVE. Our work also clearly shows how the characteristic parameters of a DVE are interrelated in deciding the time-space inconsistency, so that we may fine-tune the DVE to make it as consistent as possible. To verify the effectiveness of the metric, a Ping-Pong game is developed. Experimental results show that the metric is effective in evaluating the time-space consistency property of the game.

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An Algorithm for Distributed Discrete-Event Simulation-The 'Carrier Null Message'Approach

Proceedings of the SCS Multiconference on Distributed …, Jan 1, 1990

A load management system for running HLA-based distributed simulations over the grid

Distributed Simulation and Real- …, Jan 1, 2002

Running a large-scale distributed simulation may need a large amount of computing resources at ge... more

How network topology affects dynamic loading balancing

Parallel & Distributed …, Jan 1, 1996

The authors compare the perJbrmances of five dynamic loadbalancing strategies. The simulator they... more The authors compare the perJbrmances of five dynamic loadbalancing strategies. The simulator they 'ue developed lets them measure these performances across a range of network topologies, including a 20 mesh, a 4 0 hypercube, a linear array, and a composite Fibonacci cube. multiprocessor network without load balancing processes processor-generated tasks locally with little or no sharing of computational resources. Load balancing, on the other hand, uses a multiprocessor network's inherently redundant A processing power by redistributing the workload among the processors to improve the application's overall performance.

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A scalable architecture for supporting interactive games on the internet

Proceedings of the sixteenth …, Jan 1, 2002

This paper presents a scalable archite ctur efor supporting large-scale inter active Internet gam... more This paper presents a scalable archite ctur efor supporting large-scale inter active Internet games. In order to support a large number of particip antsand to divide the workload, the virtual world is divided into partitions. Each partition is then assigned to a server. A client (i.e., a player or a particip ant)will join a server ac c ording to the position of the avatar it controls. Compared t o a c entr alized a r chite ctur e, this distribute d client-server archite ctur e i s m o r e s c alable. In addition, compared to a fully distribute d,peer-to-p eerarchite cture, it also provides a means for dete cting cheating in distribute dgames. Sinc einteractions and accounting information must be forwarded directly to one of the servers for quali cation and veri c ation,cheating amongst distribute dplayers of the game will be minimized. T o support secur ed c ommunication for interactions and accounting information as well as to speedup periodic update messages (e.g., position updates), a hybrid communication scheme using both TCP and IP multicast is used betwe enclients and the asso ciate d server. The communication among servers is enabled by the R un-TimeInfr astructure (R TI)services. The High Level Archite ctur e (HLA) Data Distribution Management (DDM) is employed to limit the amount of communication betwe enthe servers. In addition, the Ownership Management (OM) is also employed to implement the ne edfor transferring the avatars betwe en servers. In this p ap er, the design detail of the ar chite cture

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Servicing provisioning for hla-based distributed simulation on the grid

Proceedings of the 19th …, Jan 1, 2005

Modeling and simulation permeate all areas of business, science and engineering. With the increas... more Modeling and simulation permeate all areas of business, science and engineering. With the increase in the scale and complexity of simulations, large amounts of computational resources are required, and provisioning of the services is becoming increasingly difficult. The Grid provides a platform for coordinated resource sharing and application development and execution. In this paper, we focus on extending the High Level Architecture (HLA) to the Grid. More specifically, we propose a distributed simulation framework, called HLAGrid. The framework uses a Federate-Proxy-RTI architecture, which allows resources on the Grid to be utilized on demand by using Grid services. The architecture also supports federation discovery, security of the simulator logic, and flexible federation construction, such as hierarchical federations. The architecture hides the heterogeneity of the simulators, simulators' execution platforms, and how the simulators communicate with the RTI. All interfaces used in the framework comply with the standard HLA interface specification, which provides reusability to simulators. A prototype of the framework is implemented using DMSO's RTI 1.3NG version 6 and the Grid system runs the Globus Toolkit.

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Load balancing for conservative simulation on shared memory multiprocessor systems

… , 2000. PADS 2000. …, Jan 1, 2000

Load balancing is a crucial factor in achieving good performance for parallel discrete event simu... more Load balancing is a crucial factor in achieving good performance for parallel discrete event simulations. In this paper, we present a load balancing scheme that combines both static partitioning and dynamic load balancing. The static partitioning scheme maps simulation objects to logical processes before simulation starts while the dynamic load balancing scheme attempts to balance the load during runtime. The static scheme involves two steps. First, the simulation objects that contribute to small lookahead are merged together by using a merging algorithm. Then a partitioning algorithm is applied. The merging is needed to ensure a consistent performance for our dynamic scheme. Our dynamic scheme is tailor-made for an asynchronous simulation protocol that does not rely on null messages. The performance study on a supplychain simulation shows that the partitioning algorithm and dynamic load balancing are important in achieving good performance.

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Hierarchical federations: an architecture for information hiding

Parallel and Distributed Simulation …, Jan 1, 2001

In this paper, we discuss how hierarchical federations architectures can be used to tackle this p... more In this paper, we discuss how hierarchical federations architectures can be used to tackle this problem. The hierarchical federations architecture adopted in this paper differs from the existing architectures in that it is based on a hybrid approach for interoperability between simulation federations. To demonstrate the information hiding using the architecture, a distributed semiconductor supply-chain simulation is also described in the paper.

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Efficient parallel algorithms for tree accumulations

Science of Computer Programming, Jan 1, 1994

Accumulations are higher-order operations on structured objects; they leave the shape of an objec... more Accumulations are higher-order operations on structured objects; they leave the shape of an object unchanged, but replace elements of that object with accumulated information about other elements. Upwards and downwards accumulations on trees are two such operations; they form the basis of many tree algorithms. We present two Erew Pram algorithms for computing accumulations on trees taking O(logn) time on O(n= logn) processors, which is optimal.

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Adapting a supply-chain simulation for HLA

ds-rt, Jan 1, 2000

Supply-chain management covers the planning and management of material and information from the m... more Supply-chain management covers the planning and management of material and information from the manufacturer, through the distributors, and finally to the customer. With the globalization of markets, the optimization of supplychain management becomes more and more important. Simulation of supplychains can help in the optimization process by evaluating the impact of alternative policies. To support the reusability of existing simulation models in a supply-chain simulation, a common standard is required for enabling the interoperability amongst different simulation programs through a well-defined interface. The High Level Architecture (HLA) is an architecture for reuse and interoperation of simulations. This paper reports our experiences on adopting the HLA to support reusability and interoperability in semiconductor supplychain simulation. Our experiments show that by fine-tuning the integration of the application with the HLA Run-Time Infrastructure (RTI), considerable performance improvements can be achieved.

Dag consistent parallel simulation: a predictable and robust conservative algorithm

pads, Jan 1, 1997

This paper presents a novel approach to parallel discrete event simulation based on a provably e ... more This paper presents a novel approach to parallel discrete event simulation based on a provably e cient scheduler for multithreaded programming. The \Cilk" runtime system provides the user with an algorithmic model of performance which can be used to predict the runtime of a parallel application accurately. Moreover, a Cilk application can \scale down" to run on a single processor with nearly the same performance as serial code.

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Grid services and service discovery for HLA-based distributed simulation

Distributed Simulation and …, Jan 1, 2004

Abstract Modelling and simulation permeate all areas of business, science and engineering and inc... more

The Design and Implementation of an OGSA-based grid information service

Web Services, 2004. …, Jan 1, 2004

Abstract The information service is a key component of a grid environment and critical to the ope... more

A causality based time management mechanism for federated simulation

pads, Jan 1, 2001

One of the six categories of management services provided in the Run Time Infrastructure (RTI) to... more

Soar-dsgrid: Service-oriented architecture for distributed simulation on the grid

Principles of Advanced and …, Jan 1, 2006

Simulation is a low cost alternative to experimentation on real-world physical systems. Grid tech... more Simulation is a low cost alternative to experimentation on real-world physical systems. Grid technology enables coordinated use of and secure access to distributed computing resources and data sources. The service-oriented architecture (SOA) is an ideal paradigm for next generation computing. The loose coupling among services in the SOA relieves service consumers from detailed knowledge of implementation, implementation language, and execution platform of the services to be consumed. In this paper, we propose a framework for developing a component-based distributed simulation and executing the simulation in a service-oriented architecture on the Grid. This framework consists of the schemas for developing simulation components and simulation applications, and underlying base component service modules for constructing a simulation component as a service. The use of component interfaces and schemas enables collaborative development of simulation applications, and the deployment of simulation components as services takes advantage of the SOA (e.g., loose coupling, heterogeneity, and transport neutrality). This paper discusses the motivation for developing such a framework and describes the details of its development.

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Adaptive dead reckoning algorithms for distributed interactive simulation

International Journal of Simulation, Jan 1, 2000

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