This paper presents the SEEDS simulation environment for the evaluation of distributed traffic control systems. Starting with an overview of the general simulator architecture, the software modules and the derived har...
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This paper presents the SEEDS simulation environment for the evaluation of distributed traffic control systems. Starting with an overview of the general simulator architecture, the software modules and the derived hardware architecture of the simulation environment are described with respect to performance requirements. The communication architecture of the SEEDS simulator is based on the CORBA standard and the DIS simulation protocol. With the SEEDS prototype simulating airport ground-traffic, performance measurements evaluating critical design and implementation decisions are described. The main aspects of the performance analysis are the attained application performance using CORBA and DIS as communication middleware, and the scalability of the overall approach. The evaluation shows the appropriateness of the design of the simulation environment and the derived hard- and software architecture, which is flexible and open to further extensions. Moreover the combination of CORBA and DIS provides a suited platform for distributed interactive simulation purposes because of the adequate performance, high scalability, and the high-level programming model which allows to rapidly develop and maintain complex distributed applications with high-performance requirements.
During the last few years, online analytical processing (OLAP) has emerged as a valuable tool for the analysis, navigation and reporting of hierarchically organized data from data warehouses. Still, it remains a chall...
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During the last few years, online analytical processing (OLAP) has emerged as a valuable tool for the analysis, navigation and reporting of hierarchically organized data from data warehouses. Still, it remains a challenging task to implement and deploy an OLAP system, since no standardized architecture exists, which describes the common components and functionality of OLAP systems. Additionally the formal models in use disregard the need for easily implemented and clearly defined interfaces between these components. The paper presents a model for OLAP engines, which permits the development of modular systems based on a simple data representation using sets and vectors. The functional units of the query processor are implemented in CORBA as independent modules with firm interfaces and exchange data and messages communicate across a software bus.
The GRISSLi coupling interface is a runtime library designed for the coupled computation of grid-based multidisciplinary applications. Established simulation programs, which are devoted to a single discipline, can be ...
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The GRISSLi coupling interface is a runtime library designed for the coupled computation of grid-based multidisciplinary applications. Established simulation programs, which are devoted to a single discipline, can be interconnected to a complex simulation system via the GRISSLi coupling interface without recoding the participating programs. We introduce a data model to establish the links between the (dynamic) grids and the attached coupling values in a single application program and to establish the mappings between grids and coupling values among different application programs. The user-specified consistency model is realized using asynchronous communication based on the MPI message passing standard. Efficient communication is achieved by pre-computing an optimized communication schedule and overlapping communication with computation. Flexible coupling algorithms with adaptive grids and branches are supported in GRISSLi. We have developed a prototype implementation, which provides language bindings in ANSI C and Fortran, and runs currently on IBM RS/6000 SP, Gray T3E, SGI Origin/Octane and HP-V Class. We verify the functionality and evaluate the performance of our library using an industry relevant pilot application, the steel strip production process.
Interval temporal logic (ITL) is a real-time logic for specifying and verifying real-time systems. In this paper, ITL is used to specify a concurrent real-time system: an assembly line which is an abstract model of in...
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Interval temporal logic (ITL) is a real-time logic for specifying and verifying real-time systems. In this paper, ITL is used to specify a concurrent real-time system: an assembly line which is an abstract model of industrial robot control systems. We can specify the abstract properties of the system in ITL as well as the system design using the executable subset of ITL, Tempura. Compared with other approaches, the first advantage of this methodology is that the concurrent real-time systems can be naturally specified in a true concurrent model rather than an interleaving model. The second is that the specification of the system design is executable so that the simulation can be obtained in the same formal framework. Therefore, both the properties of the system and the consistency of the specification can be checked before verification.
The Extended Air Defense Testbed (EADTB), is a comprehensive, high- and mixed-level-of-detail, environment for modeling weapon system entities and interactions. Due to the complexity of the models and large scenario s...
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The Extended Air Defense Testbed (EADTB), is a comprehensive, high- and mixed-level-of-detail, environment for modeling weapon system entities and interactions. Due to the complexity of the models and large scenario sizes, in its current single-threaded form, EADTB is limited in run-time speed. Our goal is to speed up the simulation without re-architecture or re-implementation of the models which comprise 1.76 million lines of Ada code, and without altering model behavior or compromising repeatability and causality. Our work demonstrates that the use of optimistic scheduling techniques and its derivatives, offers the best alternative for object-based systems like EADTB. Specifically we have retrofitted and integrated the same representative pseudo-EADTB prototype with two different object-oriented optimistic scheduling engines (SPEEDES and TEMPO/Thema). We discuss the required architectural and behavioral features of a simulation to allow this retrofit, the issues of C++ to Ada language interfaces, and the employment of the basic services of the optimistic scheduling engines in this environment. Experimental results suggest that order-of-magnitude speed-up is feasible through parallelization, and is scalable to larger experiments simply by adding hardware.
There are at least three major obstacles thwarting wide-spread adoption of parallel discrete-event simulation (a) lack of need, (b) lack of tools, (c) lack of predictability in behavior and performance. The plain trut...
ISBN:
(纸本)9780769501550
There are at least three major obstacles thwarting wide-spread adoption of parallel discrete-event simulation (a) lack of need, (b) lack of tools, (c) lack of predictability in behavior and performance. The plain truth is that most simulation studies can be adequately done on ordinary serial computers. parallelsimulation tools are products of re-search efforts, and simply don't stand up to the demands of modern software engineering. The results of 20 years of research in parallelsimulation reveal it to be a highly complex endevour, with performance results very much dependent on implementation details and model characteristics.
Most successful examples of parallelsimulation models were developed for parallel execution, from the beginning. A number of simulation models are designed only for sequential simulation, even in languages like PARSE...
ISBN:
(纸本)9780769501550
Most successful examples of parallelsimulation models were developed for parallel execution, from the beginning. A number of simulation models are designed only for sequential simulation, even in languages like PARSEC, that support both sequential and parallelsimulation algorithms. Converting such simulation models to a form that yields good performance with a parallel implementation can be non-trivial. In this paper we describe a case study showing this conversion process for a simulation model of replicated file systems. The details of the major steps taken in converting the simulation into a parallelsimulation are presented: correctness changes; performance changes such as communication topology simplification and lookahead specification; and modeling changes to eliminate performance bottlenecks. The details and performance improvements of each step are presented in this paper.
Traditionally, parallel discrete-event simulators based on the Time Warp synchronization protocol have been implemented using either the shared memory programming model or the distributed memory, message passing progr...
ISBN:
(纸本)9780769501550
Traditionally, parallel discrete-event simulators based on the Time Warp synchronization protocol have been implemented using either the shared memory programming model or the distributed memory, message passing programming model. This was because the preferred hardware platform was either a shared memory multiprocessor workstation or a network of uniprocessor workstations. However, with the advent of "clumps" (cluster of shared memory multiprocessors), a change in this dichotomous view becomes necessary. This paper explores the design and implementation issues involved in exploiting this new platform for Time Warp simulations. Specifically, this paper presents two generic strategies for implementing Time Warp simulators on clumps. In addition, we present our experiences in implementing these strategies on an extant distributed memory, message passing Time Warp simulator (WARPED). Preliminary performance results comparing the modified clump-specific simulation kernel to the unmodified distributed memory, message passing simulation kernel are also presented.
In this paper, we present a parallel simulator (SWiMNet) for PCS networks using a combination of optimistic and conservative paradigms. The proposed methodology exploits event precomputation permitted by model indepen...
ISBN:
(纸本)9780769501550
In this paper, we present a parallel simulator (SWiMNet) for PCS networks using a combination of optimistic and conservative paradigms. The proposed methodology exploits event precomputation permitted by model independence within the PCS components. The low percentage of blocked calls is exploited in the channel allocation simulation of precomputed events by means of an optimistic approach. %To illustrate and verify the developed approach, Experiments were conducted with various call arrival rates and mobile host densities on a cluster of Pentium workstations. Performance results indicate that the SWiMNet achieves a speedup of 6 employing 8 workstations, and a speedup of 12 with 16 workstations.
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