• Proceedings of the Korea Society for Simulation Conference
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• 1998.03a
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• pp.91-95
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• 1998

기존의 이산 사건 시스템 시뮬레이션 환경들은 Interoperability의 문제, Portability 문제로 인하여 Internet과 Web상에서 분산 시뮤레이션이 불가능하다. 본 논문에서는 이러한 제약을 해결하고자 자바를 사용하여 DEVS(Discrete Event Systems Specification)형식혼을 구현하여 Internet/Web 상에서 시뮬레이션이 가능한 DEVSim-Java 환경을 설계하고 구현하였다. DEVSim-Java를 사용하여 시뮬레이션 환경을 구현함으로써 원격지에서 개발된 시뮬레이션 모델들을 인터넷을 통하여 재사용 하는 remote model-base(RMB) 개념을 제안된다. DEVSim-Java는 자바의 장점을 이용하여 시뮬레이션 과정을 애니메이션으로 잘 나타낼수 있고, 시뮬레이션의 결과를 Graphical Analyzer를 통해 분석할 수 있게 된다.

• Proceedings of the Korea Society for Simulation Conference
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• 2002.05a
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• pp.253-258
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• 2002

This paper proposes a methodology for development of protocol models. The methodology attempts to employ two modeling environments in models development, NS2 and DEVSim++, which will interoperate during simulation. NS2 is a widely used network simulator in protocol research, which employs an informal modeling approach. Within the approach time and state information of protocol models are not explicitly described, thus being hard to validate model. On the other hand the DEVS formalism is a mathematical framework for modeling a discrete event system in a hierarchical, modular manner. In DEVS, model's time and state information is described explicitly, By using DEVS formalism, models can easily be validated and errors in the modeling stage can be reduced. However, the DEVS simulator, DEVSim++, supports a small amount of models library which are required to build simulation models of general communication network. Although NS2 employs an informal modeling approach and models validation is difficult, it supports abundant models library validated by experimental users. Thus, combination of DEVS models and NS2 models may be an effective solution for network modeling. Such combination requires interoperation between DEVSim++ simulator and NS2 simulator. This paper develops an environment for such interoperation. Correctness and effectiveness of the implemented interoperation environment have been validated by simulation of UDP and TCP models.

• Proceedings of the Korea Society for Simulation Conference
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• 1993.10a
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• pp.9-10
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• 1993

• Journal of the Korea Society of Computer and Information
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• v.18 no.4
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• pp.131-140
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• 2013

This paper deals with the design and implementation of an interface for interoperation between DiskSim, a well-known disk simulator, and a system-level simulator based on DEVSim++. Such inter-operational simulation aims at evaluation of an overall performance of storage systems which consist of multiple computer nodes with a variety of I/O level specifications. A well-known system-level simulation framework, DEVSim++ environment is based on the DEVS formalism, which provides a sound semantics of modular and hierarchical modeling methodology at the discrete event systems level such as multi-node computer systems. For maintainability we assume that there is no change of the source codes for two heterogeneous simulation engines. Thus, we adopt a notion of simulators interoperation in which there should be a means to synchronize simulation times as well as to exchange messages between simulators. As an interface for such interoperation DiskSimManager is designed and implemented. Various experiments, comparing the results of the standalone DiskSim simulation and the interoperation simulation using the proposed interface of DiskSimManager, proved that DiskSimManager works correctly as an interface for interoperation between DEVSim++ and DiskSim.

• Proceedings of the Korea Society for Simulation Conference
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• 2002.11a
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• pp.79-83
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• 2002

High Level Architecture (HLA)는 이기종 시뮬레이터 간의 연동을 위한 미들웨어이다. 본 논문에서는 Discrete Event System Specification (DEVS) 형식론을 바탕으로 한 DEVS 모델의 시뮬레이션을 HLA 기반에서 수행하는 방법에 대하여 제시한다. DEVS 시뮬레이션 메시지를 HLA의 서비스를 사용하여 변환하여 기존의 시뮬레이션 알고리즘을 그대로 사용하여 분산 시뮬레이션 할 수 있는 방식에 대하여 기술한다. 또한 모델 사이의 연결 정보를 HLA 환경에서 이용하는 방식에 대하여 기술한다. 제안된 방식을 구현한 DEVSimHLA 시뮬레이션 환경의 구조 및 동작 방식에 대하여 알아보고 이를 이용한 간단한 예제를 보인다.

• Journal of the Korea Society for Simulation
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• v.2 no.1
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• pp.31-44
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• 1993

Zeigler's DEVS(Discrete Event Systems Specification) formalism supports formal specification of discrete event systems in a hierarchical , modular manner. Associated are hierarchical, distributed simulation algorithms, called abstract simulators, which interpret dynamics of DEVS models. This paper deals with performance evaluation of P-DEVSIM ++, a parallel simulation environment which implements the DEVS formalism and associated simulation algorithms in a parallel environment. Performance simulator has been developed and used to experiment models of parallel simulation executions in different conditions. The experimental result shows that simulation time depends on both the number of processors in the parallel system and the communication overheads among such processors.

• Journal of the Korea Society for Simulation
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• v.5 no.2
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• pp.41-58
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• 1996

The Discrete Event Systems Specification(DEVS) formalism specifies a discrete event system in a hierarchical, modular form. This paper presents a distributed simulation environment D-DEVSim++ for models specified by the DEVS formalism. D-DEVSim++ employs a new simulation scheme which is a hybrid algorithm of the hierarchical simulation and Time Warp mechanisms. The scheme can utilize both the hierarchical scheduling parallelism and the inherent parallelism of DEVS models. This hierarchical scheduling parallelism is investigated through analysis. Performance of the proposed methodology is evaluated through benchmark simulation on a 5-dimensional hypercube parallel machine. The performance results indicate that the methodology can achieve significant speedup. Also, it is shown that the analyzed speedup for the hierarchical scheduling time corresponds the experiment.

• Proceedings of the Korea Society for Simulation Conference
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• 1992.10a
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• pp.5-5
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• 1992

The DEVS(discrete event system specification) formalism describes a discrete event system in a hierarchical, modular form. DEVSIM++ is C++ based general purpose DEVS abstract simulator which can simulate systems to be modeled by the DEVS formalism in a sequential environment. We implement P-DEVSIM++ which is a parallel version of DEVSIM++. In P-DEVSIM++, the external and internal event of models can be processed in parallel. To process in parallel, we introduce a hierarchical distributed simulation technique and some optimistic distributed simulation techniques. But in our algorithm, the rollback of a model is localized itself in contrast to the Time Warp approach. To evaluate its performance, we simulate a single bus multiprocessor architecture system with an external common memory. Simulation result shows that significant speedup is made possible with our algorithm in a parallel environment.

• Journal of the Korea Society for Simulation
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• v.1 no.1
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• pp.64-76
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• 1992

The DEVS(discrete event system specificaition) formalism specifies a discrete event system in a hierarchical, modular form. DEVSIM++ is a C++based general purpose DEVS abstract simulator which can simulate systems modeled by the DEVS formalism in a sequential environment. This paper describes P-DEVSIM++which is a parallel version of DEVSIM++ . In P-DEVSIM++, the external and internal event of DEVS models can by processed in parallel. For such processing, we propose a parallel, distributed optimistic simulation algorithm based on the Time Warp approach. However, the proposed algorithm localizes the rollback of a model within itself, not possible in the standard Time Warp approach. An advantage of such localization is that the simulation time may be reduced. To evaluate its performance, we simulate a single bus multiprocessor architecture system with an external common memory. Simulation result shows that significant speedup is made possible with our algorithm in a parallel environment.

• Proceedings of the Korea Society for Simulation Conference
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• 1994.06a
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• pp.0.2-0
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• 1994