SPEEDES

1. SPEEDES Charles Lenk, James Timmerman

2. Outline • SPEEDES - What is it? • What has it been used for? • SPEEDES Object • SPEEDES Event • Example Code • Two Simulation Modes • Rollback • Parallel Computation • The Event Horizon • Advantages • Disadvantages • SPEEDES vs Time Warp • Contributions / Improvements

3. SPEEDES Synchronous Parallel Environment for Emulation and Discrete- Event Simulation

4. What has it been used for? • Airspace simulation • Missile defense

5. SPEEDES Object • Can be physical objects that change or move • The simulation object can be anything, as long as it can have events that change it • Objects inherit from SpSimObj

6. SPEEDES Event • An event is a C++ function that can modify the simulated object • You can schedule events to take place at a future time and SPEEDES takes care of applying the event Event: Butterfly flaps its wings Weather Object: State changed to hurricane

7. Example Code // S_HelloWorld.H #include "SpSimObj.H" #include "SpDefineSimObj.H" #include "SpDefineEvent.H" class S_HelloWorld : public SpSimObj { public: S_HelloWorld() {} virtual void Init(); void HelloWorldEvent(); }; DEFINE_SIMOBJ(S_HelloWorld, 1, SCATTER); DEFINE_SIMOBJ_EVENT_0_ARG(HelloWorldEvent, S_HelloWorld, HelloWorldEvent);

8. Example Code Continued // S_HelloWorld.C #include "S_HelloWorld.H" void S_HelloWorld::Init() { if (SpGetSimObjKindId() == 0) { SCHEDULE_HelloWorldEvent(0.0, SpGetObjHandle()); } } void S_HelloWorld::HelloWorldEvent() { cout << "Hello World" << endl; }

9. Two Simulation Modes • Conservative • Limits how simulation objects interact • Guarantees that no rollback is ever required • Optimistic • Nodes process events with the hope that an event with an earlier timestamp won’t arrive • Rollbacks may be required

10. Rollback SPEEDES provides special rollbackable data types • RB_int • RB_double • RB_SpString • RB_voidPtr • RB_ostream • RB_cout

11. Parallel Computation • One SPEEDES node is one thread of execution • Nodes can be distributed • Multiple CPUs • Multiple networked systems • You can specify the number of nodes as a parameter to the resulting (compiled) program

12. How does SPEEDES split the work? • Objects can be assigned to nodes (SPEEDES threads) • Nodes execute the events on their respective objects

13. The Event Horizon • What is it? • Black holes hold on to matter and energy • SPEEDES holds on to messages

14. Event Horizon in Action • Events in white have been executed this cycle • Events in grey are unreleased messages • Events in black are already scheduled future events

15. Event Horizon Example Events being executed Unreleased Messages O1 O2 O3

16. Event Horizon Example Events being executed Unreleased Messages O1 O2 O3

17. Event Horizon Example Events being executed Unreleased Messages O1 O2 O3

18. Event Horizon Example Events being executed Unreleased Messages O1 O2 O3

19. Advantages • SPEEDES is fast • Less computationally expensive than time-stepped simulations • Data structures informed by the event horizon • Reduced anti-messages, no cascading rollback • Supports dynamic simulation object creation • Multiple modes of execution • Conservative • Optimistic

20. Disadvantages / Limitations • An event can only modify the state of one object • Limited to C++ • Not truly risk-free • Anti-messages • Rollbacks

21. SPEEDES vs Time Warp

22. Research Discussion Contributions: • The event horizon model used by SPEEDES can be leveraged by other discrete-event simulators • Increases data structure performance • Greatly reduces anti-messages Suggested Improvements: • Notes on SPEEDES’s event horizon compromises • Comparisons between SPEEDES’s and other’s data structures

23. Questions?