1 / 21

Discrete Event Simulation

Discrete Event Simulation. general principles. System Model System state Entities Attributes. Set Event Activity Delay. Concepts. Example - carhop system for fast food. System state: L q (t), the # of cars waiting to be served at time t

glenna-herring
Télécharger la présentation

Discrete Event Simulation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Discrete Event Simulation general principles

  2. System Model System state Entities Attributes Set Event Activity Delay Concepts

  3. Example- carhop system for fast food • System state: • Lq(t), the # of cars waiting to be served at time t • LA(t), 0 or 1 to indicate Able being ____ or ______ at time t • LB(t), o or 1 to indicate Baker being _____ or _______ at time t • Entities • Cars, Able, and Baker – related to system state • Events • Arrival event • Service completion time by Able • Service completion time by Baker • Activities • ___________ time, service time by Able, service time by Baker • Delay • The wait in _________ until Able or Baker becomes free

  4. Simulation System • Definition of the model ___________s • Provide _______ description of the model • Description of the ______ relationships and interactions between components. • Activities • Events • System states

  5. Questions must be answered • How does each _____ affect system state, entity attributes, and set contents? • How are ______ defined (deterministic or probabilistic)? • What ____ marks the beginning or end of each activity? • Can the activity begin regardless of ________________?

  6. Questions must be answered (cont.) • Which events trigger the beginning (and end) of each type of ________? • What is the system state at time 0? • What events should be generated at time 0 to “_______” the model – i.e., to get the simulation started?

  7. What is simulation • The modeling over ______ of a system all of whose state changes occur at __________ points in time • Those points when an ______ occurs. • Proceed by producing a sequence of system _________s.

  8. System Snapshot Future event list guarantees that all events occur in correct ___________ order when simulation time is advanced.

  9. Scheduling an event • At the instant an activity ________s, • Its _________ is computed • The end-activity event, together with its event time, is placed on the __________________. • Events are chronologically arranged • T < t1  t2 t3  …  tn • T is the value of CLOCK, the _____ value of simulation time. • The event associated with time t1 is called the _______ event; the next event to occur. • At CLOCK = t1, the imminent event is ______ from FEL and executed.

  10. Simulation run snapshot snapshot t1 t t2? New event may be __________ and insert to FEL. New snapshot is created based on snapshot at ___. CLOCK

  11. Event-scheduling/time-advance (ES/TA) algorithm • Remove __________ event from FEL • Advance ________ to imminent event time • Execute _______ event; update system _____, change entity _________s, and set membership as needed. • Generate _______ events (if necessary) and place on FEL in correct position. • Update cumulative _________ and counters.

  12. Example ES/TA

  13. Efficiency of Simulation Program • Efficient management of ___ have a major impact on simulation efficiency. • A ___ processing • Removal of _____ event • Insertion of ______ • Cancellation of events • Efficient operation of ______ removal and addition. • List processing too.

  14. List operation • _______ list • Top-down search from the list head • Bottom-up search • ___________ list

  15. Initial condition • System snapshot at time __ • Defined by the _____ conditions and exogenous events. • E.g., • Initial condition (5, 1, 6) at time 0; • Generate arrival event at 0, and • By producing interarrival time a*, the next arrival is at a*, etc. • Generating external arrivals is called _________.

  16. N n+1 arrival ……… Time 0 3.7 4.1 7.4 Clock = t t* a* Bootstrapping by external arrival stream A simulated time t, assumed to be the Instant of the nth arrival, generate ________l time a*, compute _____ and Schedule future arrival on ___ to occur At future time t* Between successive arrival events, other Types of events may occur, causing System state to change

  17. Stopping event • At time 0, schedule a ______ simulation event at a future time TE. • Run length TE is determined by the ___________ itself. • _________ of some specified event E.

  18. Event-scheduling simulation- single channel queue • System state • (Lq(t), Ls(t)) • Entities: • server and customers • Events: • arrival (A), departure (D), stopping event (E). • Activities: • interarrival time and service time. • Delay: • customer time spent in waiting time.

  19. Arrival event Occurs at CLOCK=t No Is Ls(t)=1 ? Yes Increase ____ By 1 Set ______ Generate service time s*; Schedule new _________ Event at time t+s* Generate interarrival time a*; Schedule next ______ event at time t+a* Collect statistics Return control to Time-advance routine To continue simulation

  20. departure event Occurs at CLOCK=t Yes No reduce Lq(t) By 1 Is Lq(t)>1 ? Set Ls(t)=0 Generate service time s*; Schedule new departure Event at time t+s* Collect statistics Return control to Time-advance routine To continue simulation

  21. Simulation table for checkout counter

More Related