A data type for discretized time representation in DEVS

Vicino, Damian; Dalle, Olivier; Wainer, Gabriel

doi:10.4108/icst.simutools.2014.254803

Cited by 10 publications

(13 citation statements)

References 5 publications

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“…In some cases, rounding errors may cause events to be reordered. 2 However, as we observe in Section 3, the presence of multiple time scales dramatically increases the likelihood and severity of time-related inaccuracies. The underlying issue is that the magnitude of the largest temporal rounding errors is determined by the longest time scales, whereas the tolerance of the simulation to these errors is constrained by the shortest time scales.…”

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confidence: 84%

Multiscale representation of simulated time

et al. 2017

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To better support multiscale modeling and simulation, we present a multiscale time representation consisting of data types, data structures, and algorithms that collectively support the recording of past events and scheduling of future events in a discrete event simulation. Our approach addresses the drawbacks of conventional time representations: limited range in the case of 32-or 64-bit fixed-point time values; problematic rounding errors in the case of floating-point numbers; and the lack of a universally acceptable precision level in the case of brute force approaches. The proposed representation provides both extensive range and fine resolution in the timing of events, yet it stores and manipulates the majority of event times as standard 64-bit numbers. When adopted for simulation purposes, the representation allows a domain expert to choose a precision level for his/her model. This time precision is honored by the simulator even when the model is integrated with other models of vastly different time scales. Making use of C++11 programming language features and the Discrete Event System Specification formalism, we implemented a simulator to test the time representation and inform a discussion on its implications for collaborative multiscale modeling efforts.

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confidence: 84%

Multiscale representation of simulated time

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“…This unnecessarily denies users the option of performing error-free discrete event simulations in applications where errors can be avoided. 41 Vicino et al 42 list many other problems with floating-point time representations. OMNeT++ was originally developed using floating-point time, yet was switched to a fixed-point representation for similar reasons as explained by Varga 39 : Why did OMNeT++ switch to -based simulation time?…”

Section: Best Practicesmentioning

confidence: 99%

Practical aspects of the DesignDEVS simulation environment

2017

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DesignDEVS is a simulation development environment based on the Discrete Event System Specification (DEVS) formalism. This paper provides an in-depth overview of the software while focusing on the practical considerations influencing its design. Practitioners who stand to benefit from systems engineering will approach formalism-based simulation tools with little knowledge of the underlying theory. It is therefore important that theoretical principles, such as the separation of model and simulator, be emphasized by the user interface. Other practical aspects of DesignDEVS include the simplicity of atomic model code, a focus on coupling for collaboration purposes, the enforcement of essential modeling constraints, and a reliance on best practices in cases where strict enforcement might inconvenience users. In DesignDEVS, an issue we refer to as the Insidious Pointer Problem is aggressively tackled through run-time error handling. By contrast, the separation of output values from state transitions is left as a best practice for the sake of user convenience. The design decisions explained in this paper are relevant to developers of other formalism-based tools seeking widespread adoption of scalable modeling and simulation practices.

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“…This finding supports the use of fixed-point over floating-point computer representations of time. More exact digital representations have recently been explored as a possibility for discrete event simulation Wainer 2014, Vicino, Dalle, andWainer 2016).…”

Section: Time Granularitymentioning

confidence: 99%

A Taxonomy of Event Time Representations

2017

TMS/DEVS Symposium on Theory of Modeling &Amp; Simulation (TMS/DEVS 2017)

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Terms such as "simulated time", "simulation time", "virtual time", "logical time", and "real time" appear throughout the modeling and simulation literature as a means of describing the timing, ordering, and/or processing of events. Unfortunately, this vocabulary can become a source of confusion due to subtle inconsistencies in how the terms are interpreted. Here we categorize mathematical representations of event times, review their formal properties such as causal consistency and causal characterization, identify formal relationships among the representations, and present a taxonomy to clarify the proper meanings of the most common notions of time in a simulation context. A thorough look at the various event time representations suggests new research opportunities, such as the repurposing of distributed computing techniques for debugging both parallel and sequential discrete event simulations.

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A data type for discretized time representation in DEVS

Cited by 10 publications

References 5 publications

Multiscale representation of simulated time

Multiscale representation of simulated time

Practical aspects of the DesignDEVS simulation environment

A Taxonomy of Event Time Representations

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