1. Parallel DEVS & DEVSJAVA
Presented by
Ximeng Sun
Mar 16, 2005

2. References Bernard P. Zergler, Herbert Praehofer, and Tag Gon Kim.
Theory of Modeling and Simulation.
Academic Press, 2000.
Bernard P. Zergler, Hessam S. Sarjoughian. Introduction to DEVS Modeling and Simulation with JAVA.

3. Outline Classic DEVS quick review Why Parallel DEVS
Parallel DEVS Formalism
Atomic Model
Coupled Model
Closure under Coupling
Parallel DEVS Simulation Protocol
DEVSJAVA

4. Classic DEVS quick review Why Parallel DEVS Parallel DEVS Formalism
Atomic Model
Coupled Model
Closure under Coupling
Parallel DEVS Simulation Protocol
DEVSJAVA

5. Classic DEVS formalism

6. DEVS in action

7. Classic DEVS Coupled Model.
D : the set of the components names.
Md : component DEVS models
EIC : external input coupling connects external inputs to component inputs
EOC : external output coupling connects component outputs to external outputs
IC : internal coupling connects component outputs to component inputs

8. Classic DEVS quick review Why Parallel DEVS Parallel DEVS Formalism
Atomic Model
Coupled Model
Closure under Coupling
Parallel DEVS Simulation Protocol
DEVSJAVA

9. Simple Pipeline model

10. In Action

11. Simultaneous events Q? For p1 which one is correct: δ int –> δ ext
δ ext –> δ int

12. Indirect control
In Classic DEVS, only one would be chosen to execute by Select function.
Select: s –> p1 ≡ internal-transition-first
Select: s –> p0 ≡ external-transition-first

13. If there’s a feedback…

14. Lose input anyway
In Classic DEVS, always make the same choice among imminent components.
Select: s –> p0|p1 ≡ p0|p1 loses input

15. Classic DEVS quick review Why Parallel DEVS Parallel DEVS Formalism
Atomic Model
Coupled Model
Closure under Coupling
Parallel DEVS Simulation Protocol
DEVSJAVA

16. Parallel DEVS Atomic Model
Xb is a set of bags over elements in X.

17. Extensions of Classic DEVS
Allowing bags of inputs to the external function
Inputs may arrive in any order
Inputs with the same identity may arrive from one or more sources
Introducing confluent transition function
Localize collision tie-breaking control

18. Confluent Transition Function
Collision: e = ta(s)
Classic DEVS: by Select function, at coupled model level – Global decision
Parallel DEVS: by , to each individual component – Local decision
Default: δcon(s,x) =δext(δint(s),0,x)
Or: δcon(s,x) =δint(δext(s,ta(s),x))

19. Parallel DEVS Coupled Model.
Identical to Classic DEVS, except for the absence of the Select function
X : a set of input events
Y : a set of output events
D : a set of component references
Md : a Parallel DEVS model, for each
Id : a set of influencers of d ,
for each
Zi,d : a set of output-to-input translation functions, for each

20. Previous example

21. Handling of imminent components in Parallel DEVS

22. Problem in Classic DEVS solved

23. Closure under Coupling of Parallel DEVS
Resultant of the coupled model:
Partition components into 4 sets: .
imminent components
components about to
receive inputs
(confluent components)
(imminent components
receiving no input)
(components receiving input
but not imminent)
(remaining components)

24. Closure under Coupling of Parallel DEVS
Functions of the Resultant:
Output Function:
Internal Transition Function:

25. Closure under Coupling of Parallel DEVS
External Transition Function:

26. Confluent Transition Function:

27. Generic Transition Function
Component is ?
Confluent:
Imminent only:
Recipient only:

28. Classic DEVS quick review Why Parallel DEVS Parallel DEVS Formalism
Atomic Model
Coupled Model
Closure under Coupling
Parallel DEVS Simulation Protocol
DEVSJAVA

29. Hierarchical Model coordinator Coupled Model simulator Coupled Model
Atomic Model
simulator
simulator
Atomic Model
Atomic Model

30. Atomic Model Simulator

31. Coupled Model Simulator

32. Classic DEVS quick review Why Parallel DEVS Parallel DEVS Formalism
Atomic Model
Coupled Model
Closure under Coupling
Parallel DEVS Simulation Protocol
DEVSJAVA

33. DEVSJAVA
DEVS-based, Object-Oriented Modeling and Simulation environment.
Written in Java and supports parallel execution on a uni-processor
Simulation Viewer for animating simulation in V2.7

34. Package Diagram

35. DEVSJAVA Class hierarchy of container classes

36. DEVSJAVA Class hierarchy of DEVS classes

37. Simple Pipeline in DEVSJAVA

38. Simulation Viewer

39. More complicated example

40. Sources
DEVSJAVA - Modeling and Simulation environment for developing DEVS-based models by Hessam Sarjoughian, Bernard Zeigler.
(need a license)

41. Question?