1 Simulation Implementation Using high-level languages Slide 2 2
Implementation of a Single- Server Queuing System Two Main Entities
SERVER: Busy= 0/1 QUEUE: Qsize= # Two Critical Events for customers
Arrival Complete Service (Depart) How do these entities interact?
Initialization? How are each of the variables affected? How should
simulation terminate? Slide 3 3 Snapshot or System Image State of
the system at a given time State variables Queue Future Events List
(FEL) Slide 4 4 Generating Future Events Bootstrapping: a method
for generating an arrival stream on an as you go basis As opposed
to generating all events at once a.k.a. on-the-fly Slide 5 5
Generating Future Events Process 1. Generate initial arrival; when
it is removed from FEL generate new interarrival time - add to
clock for arrival time- place next arrival on FEL 2. When item is
placed in service, generate service time - add to clock place
completion event on FEL Slide 6 6 DATA Structures Future Events
List (FEL) Queue (1 or more) What information is required for each
one? What information is not required but might be convenient? When
and how are insertions & deletions made? When are various units
of information generated (calculated)? Slide 7 7 Queue Standard
FIFO Customer identification Time entered queue Arrival time Type
of service being requested (if more than one) Slide 8 8 Future
Events List Array implementation Each row represents a specific
event Customer ID (identification number) Time of occurrence Search
for smallest time to get the next event Slide 9 9 Future Events
List Linked List ordered by time of occurrence Event Type Time of
Occurrence Identification of customer Slide 10 10 Generating
Arrivals Initialize at a fixed time or time zero One for each type
of arrival Subsequent arrivals are generated as arrival is removed
Remove arrival- generate IAT- add to current time (clock) - put on
FEL At any time, there should only be one arrival of any given type
Slide 11 11 Generating Departures Complete Service Generated when
customer enters the service that will cause the departure Not
necessarily upon arrival, not if enter queue, only when enter
service Enter service (from queue or from arrival) - generate
service time - add to current time (clock) - put on FEL Slide 12 12
Generating Events Terminate Event Only one: placed on FEL at
initialization Snapshot Event (Status Report) Initialize 1 st one
Remove from FEL- add time unit - return to FEL Slide 13 13 What? Me
Simulate? Paper by Dr. Halverson Slide 14 14 Generation of Events
Initialization of FEL One arrival (of each type) Snapshot Stop
event Generation of Arrival When removed from FEL, generate next
arrival Slide 15 15 MAIN Initialize FEL, statistical variables,
clock Remove next-event from FEL While not stop-event Clock =
next-event.time Case next-event of Arrival: produce next arrival
call ARRIVE Departure: call DEPART Snapshop: call SNAPSHOT Remove
next-event from FEL Stop-simulation: call STATS; call OUTPUT Slide
16 16 ARRIVE If server_status = busy Then call ENTER-QUEUE Else
call ENTER-SERVICE Slide 17 17 DEPART If queue = empty Then
server_status= free Else call REMOVE-FROM-QUEUE Slide 18 18
ENTER-SERVICE server_status = busy Generate departure event Update
service stats Slide 19 19 ENTER-QUEUE Add customer to queue Update
queue statistics Slide 20 20 REMOVE-FROM-QUEUE Update queue and
statistics Call ENTER-SERVICE Slide 21 21 STATS Compute final
averages, totals, etc. IAT, Service time, Utilization Queue length,
max, min, average Number arrivals, departures Wait time, Time in
system Slide 22 SNAPSHOT Generate next Snapshot event, place in FEL
Print State variables Print Queue Print FEL 22 Slide 23 23 OUTPUT
Print results Slide 24 PROJECT #1 Must follow the guidelines
presented in class for the form of your program. Must use object
oriented approach Print out of Code due in 1 week 24
