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Determinate Composition of FMUs for Co-Simulation
David Broman, Christopher Brooks, Lev Greenberg, Edward A. Lee, Michael Masin, Stavros Tripakis, Michael Wetter

Citation
David Broman, Christopher Brooks, Lev Greenberg, Edward A. Lee, Michael Masin, Stavros Tripakis, Michael Wetter. "Determinate Composition of FMUs for Co-Simulation". 13th International Conference on Embedded Software (EMSOFT), Montreal, 29, September, 2013.

Abstract
In this paper, we explain how to achieve deterministic execution of FMUs (Functional Mockup Units) under the FMI (Functional Mockup Interface) standard. In particular, we focus on co-simulation, where an FMU either contains its own internal simulation algorithm or serves as a gateway to a simulation tool. We give conditions on the design of FMUs and master algorithms (which orchestrate the execution of FMUs) to achieve deterministic co-simulation. We show that with the current version of the standard, these conditions demand capabilities from FMUs that are optional in the standard and rarely provided by an FMU in practice. When FMUs lacking these required capabilities are used to compose a model, many basic modeling capabilities become unachievable, including simple discrete-event simulation and variable-step-size numerical integration algorithms. We propose a small extension to the standard and a policy for designing FMUs that enables deterministic execution for a much broader class of models. The extension enables a master algorithm to query an FMU for the time of events that are expected in the future. We show that a model can be executed deterministically if all FMUs in the model are either memoryless or implement one of rollback or step-size prediction. We show further that such a model can contain at most one "legacy" FMU that is not memoryless and provides neither rollback nor step-size prediction.

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Citation formats  
  • HTML
    David Broman, Christopher Brooks, Lev Greenberg, Edward A.
    Lee, Michael Masin, Stavros Tripakis, Michael Wetter. <a
    href="http://chess.eecs.berkeley.edu/pubs/1002.html"
    >Determinate Composition of FMUs for
    Co-Simulation</a>, 13th International Conference on
    Embedded Software (EMSOFT), Montreal, 29, September, 2013.
  • Plain text
    David Broman, Christopher Brooks, Lev Greenberg, Edward A.
    Lee, Michael Masin, Stavros Tripakis, Michael Wetter.
    "Determinate Composition of FMUs for
    Co-Simulation". 13th International Conference on
    Embedded Software (EMSOFT), Montreal, 29, September, 2013.
  • BibTeX
    @inproceedings{BromanBrooksGreenbergLeeMasinTripakisWetter13_DeterminateCompositionOfFMUsForCoSimulation,
        author = {David Broman and Christopher Brooks and Lev
                  Greenberg and Edward A. Lee and Michael Masin and
                  Stavros Tripakis and Michael Wetter},
        title = {Determinate Composition of FMUs for Co-Simulation},
        booktitle = {13th International Conference on Embedded Software
                  (EMSOFT), Montreal},
        day = {29},
        month = {September},
        year = {2013},
        abstract = {In this paper, we explain how to achieve
                  deterministic execution of FMUs (Functional Mockup
                  Units) under the FMI (Functional Mockup Interface)
                  standard. In particular, we focus on
                  co-simulation, where an FMU either contains its
                  own internal simulation algorithm or serves as a
                  gateway to a simulation tool. We give conditions
                  on the design of FMUs and master algorithms (which
                  orchestrate the execution of FMUs) to achieve
                  deterministic co-simulation. We show that with the
                  current version of the standard, these conditions
                  demand capabilities from FMUs that are optional in
                  the standard and rarely provided by an FMU in
                  practice. When FMUs lacking these required
                  capabilities are used to compose a model, many
                  basic modeling capabilities become unachievable,
                  including simple discrete-event simulation and
                  variable-step-size numerical integration
                  algorithms. We propose a small extension to the
                  standard and a policy for designing FMUs that
                  enables deterministic execution for a much broader
                  class of models. The extension enables a master
                  algorithm to query an FMU for the time of events
                  that are expected in the future. We show that a
                  model can be executed deterministically if all
                  FMUs in the model are either memoryless or
                  implement one of rollback or step-size prediction.
                  We show further that such a model can contain at
                  most one "legacy" FMU that is not memoryless and
                  provides neither rollback nor step-size
                  prediction. },
        URL = {http://chess.eecs.berkeley.edu/pubs/1002.html}
    }
    

Posted by David Broman on 12 Aug 2013.
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