The Experts below are selected from a list of 141657 Experts worldwide ranked by ideXlab platform
Richard M. Fujimoto - One of the best experts on this subject based on the ideXlab platform.
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WSC - Time-Parallel Simulation of air traffic networks
2017 Winter Simulation Conference (WSC), 2017Co-Authors: Young Jin Kim, Dimitri N. Mavris, Richard M. FujimotoAbstract:Air traffic management is widely studied in several different fields because of its complexity and criticality to a variety of stakeholders. However, the exploding amount of air traffic in recent years has created new challenges to ensure effective management of the airspace. A fast time Simulation capability is essential to effectively explore the consequences of decisions of air traffic management. A new algorithm for simulating air traffic networks using a time-Parallel Simulation approach is proposed that distributes time segments of the Simulation scenarios across different processors. A Simulation model for the National Airspace System (NAS) is described and validated. The components of the simulator are described as well as the Parallel Simulation algorithms. Experimental results utilizing real-world traffic data for the continental U.S. are presented demonstrating the speed ups achieved by a prototype simulator. These results illustrate that time-Parallel Simulation can be used to significantly accelerate certain air traffic Simulations.
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Techniques for efficient Parallel Simulation and their application to large-scale telecommunication network models
1999Co-Authors: Kalyan S. Perumalla, Richard M. FujimotoAbstract:It is widely recognized that Parallel Simulation technology is necessary to address the new Simulation requirements of important applications such as large-scale network models. However, current Parallel Simulation techniques possess limitations in the type and sizes of models that can be efficiently simulated in Parallel. In particular, optimistic Parallel Simulation of fine-grained models have been plagued by large state saving overheads, both in event-oriented and process-oriented views, resulting in unsatisfactory Parallel execution speed for many important applications. In the absence of alternative solutions, it was generally believed that optimistic approaches are inapplicable in such applications. This thesis asserts that, by use of appropriately constructed novel techniques, it is indeed possible to perform fast optimistic Parallel Simulation of fine-grained models, using both event-oriented and process-oriented views. In support of this claim, techniques are presented here that significantly lower the overheads, thereby enabling the capability to efficiently simulate large-scale, fine-grained models in Parallel. On sample models, when compared to previously known approaches, the techniques presented here improve the Simulation speed by a factor of 3 or more, while simultaneously reducing the memory requirements by almost half. The first technique addresses the high overheads of state saving mechanisms that are traditionally used in supporting rollback operations in optimistic Parallel Simulation. An alternative approach called reverse computation is identified for realizing rollback, which is demonstrated to significantly improve the Parallel Simulation speed while greatly reducing the memory utilization of the Simulation. The next technique concerns the process-oriented worldview, which is extremely useful in many domains, such as telecommunication network protocol modeling. An approach called stack reconstruction is developed to address the high execution overheads traditionally associated with process-oriented views, and its effectiveness is demonstrated in achieving a high rate of process-context switching during optimistic Simulation. Additional contributions of this thesis include the identification and solution of other typical problems encountered in the design, development and Parallel Simulation of models for real-life telecommunication network protocols. This work serves to demonstrate the readiness and feasibility of applying Parallel Simulation technology to today's large and complex models. The Parallel Simulation techniques described in this thesis are applied and analyzed in the context of telecommunication network Simulation, using representative network models. The techniques, however, are not restricted to network Simulation, but are equally applicable to other domains as well. For example, the Parallel Simulation of any network of queues can benefit from the reverse computation system presented here. In fact, the reverse computation system is relevant to other application areas as well, such as in database recovery, and debugging environments. Similarly, the stack reconstruction approach is applicable to any multi-threaded system that requires an efficient incremental checkpointing facility for its thread states.
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Parallel Simulation techniques for large-scale networks
IEEE Communications Magazine, 1998Co-Authors: Sandeep N. Bhatt, Richard M. Fujimoto, Andrew T. Ogielski, Kalyan S. PerumallaAbstract:Simulation has always been an indispensable tool in the design and analysis of telecommunication networks. Due to performance limitations of the majority of simulators, usually network Simulations have been done for rather small network models and for short timescales. In contrast, many difficult design problems facing today's network engineers concern the behavior of very large hierarchical multihop networks carrying millions of multiprotocol flows over long timescales. Examples include scalability and stability of routing protocols, packet losses in core routers, of long-lasting transient behavior due to observed self-similarity of traffic patterns. Simulation of such systems would greatly benefit from application of Parallel computing technologies, especially now that multiprocessor workstations and servers have become commonly available. However, Parallel Simulation has not yet been widely embraced by the telecommunications community due to a number of difficulties. Based on our accumulated experience in Parallel network Simulation projects, we believe that Parallel Simulation technology has matured to the point that it is ready to be used in industrial practice of network Simulation. This article highlights work in Parallel Simulations of networks and their promise.
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Parallel Simulation of statistical multiplexers
Discrete Event Dynamic Systems, 1995Co-Authors: Richard M. Fujimoto, Ioanis Nikolaidis, C. Anthony CooperAbstract:The Simulation of high-speed telecommunication systems such as ATM (Asynchronous Transfer Mode) networks has generally required excessively long run times. This paper reviews alternative approaches using Parallelism to speed up Simulations of discrete event systems, and telecommunication networks in particular. Subsequently, a new Simulation method is introduced for the fast Parallel Simulation of a common network element, namely, a work-conserving finite capacity statistical multiplexer of bursty ON/OFF sources arriving on input links of equal peak rate. The primary performance measure of interest is the cell loss ratio, due to buffer overflows. The proposed method is based on two principal techniques: (1) the derivation of low-level (cell level) statistics from a higher level (burst level) Simulation and (2) Parallel execution of the burst level Simulation program. For the latter, atime-division Parallel Simulation method is used where Simulations operating at different intervals of simulated time are executed concurrently on different processors. Both techniques contribute to the overall speedup. Furthermore, these techniques support Simulations that are driven by traces of actual network traffic (trace-driven Simulation), in addition to standard models for source traffic. An analysis of this technique is described, indicating that it offers excellent potential for delivering good performance. Measurements of an implementation running on a 32 processor KSR-2 multiprocessor demonstrate that, for certain model parameter settings, the simulator is able to simulate up to 10 billion cell arrivals per second of wallclock time.
Mario Gerla - One of the best experts on this subject based on the ideXlab platform.
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glomosim a library for Parallel Simulation of large scale wireless networks
Workshop on Parallel and Distributed Simulation, 1998Co-Authors: Xiang Zeng, Rajive Bagrodia, Mario GerlaAbstract:A number of library based Parallel and sequential network simulators have been designed. The paper describes a library, called GloMoSim (Global Mobile system Simulator), for Parallel Simulation of wireless networks. GloMoSim has been designed to be extensible and composable: the communication protocol stack for wireless networks is divided into a set of layers, each with its own API. Models of protocols at one layer interact with those at a lower (or higher) layer only via these APIs. The modular implementation enables consistent comparison of multiple protocols at a given layer. The Parallel implementation of GloMoSim can be executed using a variety of conservative synchronization protocols, which include the null message and conditional event algorithms. The paper describes the GloMoSim library, addresses a number of issues relevant to its Parallelization, and presents a set of experimental results on the IBM 9076 SP, a distributed memory multicomputer. These experiments use models constructed from the library modules.
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Workshop on Parallel and Distributed Simulation - GloMoSim: a library for Parallel Simulation of large-scale wireless networks
1998Co-Authors: Xiang Zeng, Rajive Bagrodia, Mario GerlaAbstract:A number of library based Parallel and sequential network simulators have been designed. The paper describes a library, called GloMoSim (Global Mobile system Simulator), for Parallel Simulation of wireless networks. GloMoSim has been designed to be extensible and composable: the communication protocol stack for wireless networks is divided into a set of layers, each with its own API. Models of protocols at one layer interact with those at a lower (or higher) layer only via these APIs. The modular implementation enables consistent comparison of multiple protocols at a given layer. The Parallel implementation of GloMoSim can be executed using a variety of conservative synchronization protocols, which include the null message and conditional event algorithms. The paper describes the GloMoSim library, addresses a number of issues relevant to its Parallelization, and presents a set of experimental results on the IBM 9076 SP, a distributed memory multicomputer. These experiments use models constructed from the library modules.
Rajive Bagrodia - One of the best experts on this subject based on the ideXlab platform.
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Asynchronous Parallel Simulation of Parallel programs
IEEE Transactions on Software Engineering, 2000Co-Authors: Sundeep Prakash, Ewa Deelman, Rajive BagrodiaAbstract:Parallel Simulation of Parallel programs for large datasets has been shown to offer significant reduction in the execution time of many discrete event models. The paper describes the design and implementation of MPI-SIM, a library for the execution driven Parallel Simulation of task and data Parallel programs. MPI-SIM can be used to predict the performance of existing programs written using MPI for message passing, or written in UC, a data Parallel language, compiled to use message passing. The Simulation models can be executed sequentially or in Parallel. Parallel execution of the models are synchronized using a set of asynchronous conservative protocols. The paper demonstrates how protocol performance is improved by the use of application-level, runtime analysis. The analysis targets the communication patterns of the application. We show the application-level analysis for message passing and data Parallel languages. We present the validation and performance results for the simulator for a set of applications that include the NAS Parallel Benchmark suite. The application-level optimization described in the paper yielded significant performance improvements in the Simulation of Parallel programs, and in some cases completely eliminated the synchronizations in the Parallel execution of the Simulation model.
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Performance evaluation of conservative algorithms in Parallel Simulation languages
IEEE Transactions on Parallel and Distributed Systems, 2000Co-Authors: Rajive Bagrodia, M. TakaiAbstract:Parallel discrete event Simulation with conservative synchronization algorithms has been used as a high performance alternative to sequential Simulation. In this paper, we examine the performance of a set of Parallel conservative algorithms that have been implemented in the Maisie Parallel Simulation language. The algorithms include the asynchronous null message algorithm, the synchronous conditional event algorithm, and a new hybrid algorithm called Accelerated Null Message that combines features from the preceding algorithms. The performance of the algorithms is compared using the Ideal Simulation Protocol. This protocol provides a tight lower bound on the execution time of a Simulation model on a given architecture and serves as a useful base to compare the synchronization overheads of the different algorithms. The performance of the algorithms is compared as a function of various model characteristics that include model connectivity, computation granularity, load balance, and lookahead.
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Workshop on Parallel and Distributed Simulation - GloMoSim: a library for Parallel Simulation of large-scale wireless networks
1998Co-Authors: Xiang Zeng, Rajive Bagrodia, Mario GerlaAbstract:A number of library based Parallel and sequential network simulators have been designed. The paper describes a library, called GloMoSim (Global Mobile system Simulator), for Parallel Simulation of wireless networks. GloMoSim has been designed to be extensible and composable: the communication protocol stack for wireless networks is divided into a set of layers, each with its own API. Models of protocols at one layer interact with those at a lower (or higher) layer only via these APIs. The modular implementation enables consistent comparison of multiple protocols at a given layer. The Parallel implementation of GloMoSim can be executed using a variety of conservative synchronization protocols, which include the null message and conditional event algorithms. The paper describes the GloMoSim library, addresses a number of issues relevant to its Parallelization, and presents a set of experimental results on the IBM 9076 SP, a distributed memory multicomputer. These experiments use models constructed from the library modules.
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glomosim a library for Parallel Simulation of large scale wireless networks
Workshop on Parallel and Distributed Simulation, 1998Co-Authors: Xiang Zeng, Rajive Bagrodia, Mario GerlaAbstract:A number of library based Parallel and sequential network simulators have been designed. The paper describes a library, called GloMoSim (Global Mobile system Simulator), for Parallel Simulation of wireless networks. GloMoSim has been designed to be extensible and composable: the communication protocol stack for wireless networks is divided into a set of layers, each with its own API. Models of protocols at one layer interact with those at a lower (or higher) layer only via these APIs. The modular implementation enables consistent comparison of multiple protocols at a given layer. The Parallel implementation of GloMoSim can be executed using a variety of conservative synchronization protocols, which include the null message and conditional event algorithms. The paper describes the GloMoSim library, addresses a number of issues relevant to its Parallelization, and presents a set of experimental results on the IBM 9076 SP, a distributed memory multicomputer. These experiments use models constructed from the library modules.
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Parsec: a Parallel Simulation environment for complex systems
Computer, 1998Co-Authors: Rajive Bagrodia, Masaki Takai, Yu-an Chen, Xiang Zeng, R. Meyer, J. Martin, Ha Yoon SongAbstract:Design and development costs for extremely large systems could be significantly reduced if only there were efficient techniques for evaluating design alternatives and predicting their impact on overall system performance metrics. Due to the systems' analytical intractability, Simulation is the most common performance evaluation technique for such systems. However, the long execution times needed for sequential Simulation models often hampers evaluation. The slow speeds of sequential model execution have led to growing interest in the use of Parallel execution for simulating large-scale systems. Widespread use of Parallel Simulation, however; has been significantly hindered by a lack of tools for integrating Parallel model execution into the overall framework of system Simulation. Another drawback to widespread use of Simulations is the cost of model design and maintenance. The Simulation environment the authors developed at UCLA attempts to address some of these issues. It consists of three primary components: a Parallel Simulation language called Parsec (Parallel Simulation environment for complex systems), its GUI, called Pave, and the portable runtime system that implements the Simulation algorithms.
Kalyan S. Perumalla - One of the best experts on this subject based on the ideXlab platform.
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Techniques for efficient Parallel Simulation and their application to large-scale telecommunication network models
1999Co-Authors: Kalyan S. Perumalla, Richard M. FujimotoAbstract:It is widely recognized that Parallel Simulation technology is necessary to address the new Simulation requirements of important applications such as large-scale network models. However, current Parallel Simulation techniques possess limitations in the type and sizes of models that can be efficiently simulated in Parallel. In particular, optimistic Parallel Simulation of fine-grained models have been plagued by large state saving overheads, both in event-oriented and process-oriented views, resulting in unsatisfactory Parallel execution speed for many important applications. In the absence of alternative solutions, it was generally believed that optimistic approaches are inapplicable in such applications. This thesis asserts that, by use of appropriately constructed novel techniques, it is indeed possible to perform fast optimistic Parallel Simulation of fine-grained models, using both event-oriented and process-oriented views. In support of this claim, techniques are presented here that significantly lower the overheads, thereby enabling the capability to efficiently simulate large-scale, fine-grained models in Parallel. On sample models, when compared to previously known approaches, the techniques presented here improve the Simulation speed by a factor of 3 or more, while simultaneously reducing the memory requirements by almost half. The first technique addresses the high overheads of state saving mechanisms that are traditionally used in supporting rollback operations in optimistic Parallel Simulation. An alternative approach called reverse computation is identified for realizing rollback, which is demonstrated to significantly improve the Parallel Simulation speed while greatly reducing the memory utilization of the Simulation. The next technique concerns the process-oriented worldview, which is extremely useful in many domains, such as telecommunication network protocol modeling. An approach called stack reconstruction is developed to address the high execution overheads traditionally associated with process-oriented views, and its effectiveness is demonstrated in achieving a high rate of process-context switching during optimistic Simulation. Additional contributions of this thesis include the identification and solution of other typical problems encountered in the design, development and Parallel Simulation of models for real-life telecommunication network protocols. This work serves to demonstrate the readiness and feasibility of applying Parallel Simulation technology to today's large and complex models. The Parallel Simulation techniques described in this thesis are applied and analyzed in the context of telecommunication network Simulation, using representative network models. The techniques, however, are not restricted to network Simulation, but are equally applicable to other domains as well. For example, the Parallel Simulation of any network of queues can benefit from the reverse computation system presented here. In fact, the reverse computation system is relevant to other application areas as well, such as in database recovery, and debugging environments. Similarly, the stack reconstruction approach is applicable to any multi-threaded system that requires an efficient incremental checkpointing facility for its thread states.
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Parallel Simulation techniques for large-scale networks
IEEE Communications Magazine, 1998Co-Authors: Sandeep N. Bhatt, Richard M. Fujimoto, Andrew T. Ogielski, Kalyan S. PerumallaAbstract:Simulation has always been an indispensable tool in the design and analysis of telecommunication networks. Due to performance limitations of the majority of simulators, usually network Simulations have been done for rather small network models and for short timescales. In contrast, many difficult design problems facing today's network engineers concern the behavior of very large hierarchical multihop networks carrying millions of multiprotocol flows over long timescales. Examples include scalability and stability of routing protocols, packet losses in core routers, of long-lasting transient behavior due to observed self-similarity of traffic patterns. Simulation of such systems would greatly benefit from application of Parallel computing technologies, especially now that multiprocessor workstations and servers have become commonly available. However, Parallel Simulation has not yet been widely embraced by the telecommunications community due to a number of difficulties. Based on our accumulated experience in Parallel network Simulation projects, we believe that Parallel Simulation technology has matured to the point that it is ready to be used in industrial practice of network Simulation. This article highlights work in Parallel Simulations of networks and their promise.
Xiang Zeng - One of the best experts on this subject based on the ideXlab platform.
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Workshop on Parallel and Distributed Simulation - GloMoSim: a library for Parallel Simulation of large-scale wireless networks
1998Co-Authors: Xiang Zeng, Rajive Bagrodia, Mario GerlaAbstract:A number of library based Parallel and sequential network simulators have been designed. The paper describes a library, called GloMoSim (Global Mobile system Simulator), for Parallel Simulation of wireless networks. GloMoSim has been designed to be extensible and composable: the communication protocol stack for wireless networks is divided into a set of layers, each with its own API. Models of protocols at one layer interact with those at a lower (or higher) layer only via these APIs. The modular implementation enables consistent comparison of multiple protocols at a given layer. The Parallel implementation of GloMoSim can be executed using a variety of conservative synchronization protocols, which include the null message and conditional event algorithms. The paper describes the GloMoSim library, addresses a number of issues relevant to its Parallelization, and presents a set of experimental results on the IBM 9076 SP, a distributed memory multicomputer. These experiments use models constructed from the library modules.
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glomosim a library for Parallel Simulation of large scale wireless networks
Workshop on Parallel and Distributed Simulation, 1998Co-Authors: Xiang Zeng, Rajive Bagrodia, Mario GerlaAbstract:A number of library based Parallel and sequential network simulators have been designed. The paper describes a library, called GloMoSim (Global Mobile system Simulator), for Parallel Simulation of wireless networks. GloMoSim has been designed to be extensible and composable: the communication protocol stack for wireless networks is divided into a set of layers, each with its own API. Models of protocols at one layer interact with those at a lower (or higher) layer only via these APIs. The modular implementation enables consistent comparison of multiple protocols at a given layer. The Parallel implementation of GloMoSim can be executed using a variety of conservative synchronization protocols, which include the null message and conditional event algorithms. The paper describes the GloMoSim library, addresses a number of issues relevant to its Parallelization, and presents a set of experimental results on the IBM 9076 SP, a distributed memory multicomputer. These experiments use models constructed from the library modules.
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Parsec: a Parallel Simulation environment for complex systems
Computer, 1998Co-Authors: Rajive Bagrodia, Masaki Takai, Yu-an Chen, Xiang Zeng, R. Meyer, J. Martin, Ha Yoon SongAbstract:Design and development costs for extremely large systems could be significantly reduced if only there were efficient techniques for evaluating design alternatives and predicting their impact on overall system performance metrics. Due to the systems' analytical intractability, Simulation is the most common performance evaluation technique for such systems. However, the long execution times needed for sequential Simulation models often hampers evaluation. The slow speeds of sequential model execution have led to growing interest in the use of Parallel execution for simulating large-scale systems. Widespread use of Parallel Simulation, however; has been significantly hindered by a lack of tools for integrating Parallel model execution into the overall framework of system Simulation. Another drawback to widespread use of Simulations is the cost of model design and maintenance. The Simulation environment the authors developed at UCLA attempts to address some of these issues. It consists of three primary components: a Parallel Simulation language called Parsec (Parallel Simulation environment for complex systems), its GUI, called Pave, and the portable runtime system that implements the Simulation algorithms.
