Improved pythonDEVS simulator

• Team
  • Fei Men
  • fei.men@mail.mcgill.ca
  
  
• Motivation
  The existing version of pythonDEVS simulator didn't fully match DEVS formalism. The exist version is functional but there is some part we can improve to enhance scalability and reusability of the simulator.
  
  
  Basically,I enhanced the initialization,reset and termination control of simulation. What's more,I implemented couplings as objects, which would allow a modeller to specify output-input transfer functions, thus the model become much more reusable.
  
  
• Proposal/Requirements
  Implement all the following functions in the new simulator:
  • Initialize the model by default function or customize function
  • Set the termination conditions including end_time conditions or end_state conditions
  • Simulate the model until termination conditions satisfied
  • Terminate the experiment properly
  • Provide output-input transfer functions(Z-function)
  
  
• Design/Models

  1.work flow:

  

  2.Steps:

  Initialize the model by default function or customize function

  Set the termination conditions including end_time conditions or end_state conditions

  Simulate the model until termination conditions satisfied

  Terminate the experiment

  Reset time or reset time and initialization

  
  
• Implementation

  1.Functions added in Simulator:

  
  • Typically, new functions can be found in class Simulator(AtomicSolver, CoupledSolver) except Z-function.To implement Z-function, the change in Simulator.py is in class CoupledSolver where transfer data according to the Z-function of different ConnectPorts

    2.Changes in Model:

  • for submodel TrafficLight, just make sure not much exception when doing state transfer.
  • for submodel Policeman,an input port and extTransition are added for the implemetation of Z-function.
  • for TrafficSystem model, Z-function of the ConnectPorts are given.

    3.Changes in DEVS:

    in class CoupledDEVS,Function connectPorts is extended by adding "func".
  
  
• Experiments

  In Experiment.py:

  • the steps we ask Simulator to do:

    Here the model which will be simulated is "trafficSystem". The submodel trafficLight will start in "green" state at time 0.5 and submodel policeman will start by default.

    In the first round,the experiment will stop at time 500.Before that there will be two input events coming at time 60 and time 150.

    In the second round, which is started by reset, with policeman will be "working" at time 6. Stop at time 650 or when state become "green"

  • the term-condition function:

    the definations of all the termCondition functions.

  
  
• Conclusions

  1.Results:

  Result

  2.Analysis:

  • The result shows that everything goes as we expected.Here just talk about the handling of input event and Z-function.

    At time 60, the first input event arrived. As we have connect the input port of trafficSystem to the input port of policeman and the Z-function of them is to opposite the coming signal, so policeman got the signal "towork" and was going to change at time 160

    At time 150, the other input event arrived, so policeman model discarded the former schedule at time 160, implement input event 150, and going to chage state to idle at time 350

    So at time 350, policeman state changed and then trafficLight got the interrupt signal from policeman.At last, the first round stop at end-time 500.

    the second round started at time 6 and stopped at state "green" as we expected.

  
  
• References

  1.Background:

  PyDEVS

  2.source code:

  • Project.zip

    Simulator.py

    DEVS.py

    3. test case:TrafficSystem

    Model.py Experiment.py
  
  
• Presentation
  Presentation