Chapt 5 Basic Network Modeling

1. Chapt 5 Basic Network Modeling • Intro/ steps in the process • Single server queuing system • CREATE Node • TERMINATE Node • ASSIGN Node • GOON Node • COLCT Node • SELECT Node • EXAMPLES

2. Introduction • Using process orientation • What detail to represent • How to represent detail • Will want to iteratively develop model • Use graphic symbols…ie FBD

3. Introduction of a simple queue • Items arrive, wait, processed than depart system..ie a process • Entities flow thru process ie items • Entities are assigned attributes values that distinguish it ie time entered a system • Resources are what entities complete while flowing thru system ie servers, tools etc (busy/idle) • Use graphic symbols of SLAM to represent

4. Inspect Radios simple queue • Radio arrives @ inspection area • Queue of radios • Activity of the Inspection of radio • Inspected radio departs system Queue of Radios Arriving Radios Inspection station Inspected Radio

5. A Queue Node Activity or server # # parallel servers Modeling Queues & servers • Passage of Time is represented by a branch • Waiting occurs at queue IQ= Initial Number in queue QC= Max number in queue IFL=File # for storing waiting entities IQ Service Activity IFL QC N

6. Modeling Arrival of Entities • Generates entities into the system • TF = Time for First entity to be created • TBC = Time Between Creations of entities • MV = Variable to contain Mark time “time entity was created” • MC = Max # of entities created • M = Max # of branches TBC MV M MC TF When is 2nd entity created?

7. TC Modeling Departure of Entities • Entities leave the system • TC = # of entities arrivals to halt the analysis

8. Inspect Radios simple queue • Radio arrives @ inspection area • Queue of radios • Activity of the Inspection of radio • Inspected radio departs system Queue of Radios Arriving Radios Inspection station Inspected Radio

9. TBC =10 MV 1 MC Combine Modeling Concepts Take branch 1 TF=7 # of entities to terminate a run Service time 9 200 1 3 Queue Node # parallel servers Activity or server #

10. Create Node TBC, time bwtn =EXPON(1) TF, start time = 0 MV, mark time goes in attribute 1 MC, entities created infinite M, # of branches is 1 • Create, TBC,TF,MV,MC,M

11. Queue Node IFL, file # = 1 IQ, Initial # in queue = 10 QC, queue capacity = 20 Balk-entity routed to another node in network Block-entity waits for free space • Queue (IFL),IQ,QC Queue called “Awaitpaint” Hash mark for Queue

12. Terminate Node TC, termination count # of entities to process until stop, infinite • Terminate, TC (IFL),IQ,QC Called “Finished”

13. Assign Node • Used to prescribe values to the attributes of an entity passing thru an ASSIGN Node…duration of activities based on assigned values • ASSIGN, {{VAR, VALUE}, Repeats}, M # of branches P 2 5 10 The value of attribute 3 is assigned a value based on a triangular distribution Node Label/ name

14. Activities • Branches used to model activities…specific time delays prescribed of entities flowing thru network • ACTIVITY,A,DUR,CONDITION,NLBL,N,ID; A = activity #, DUR = duration, NLBL = end node label if end node is not listed, N = # of parallel servers, ID = activity id Condition Duration Activity #

15. 2 Parallel Servers Example • Create bank customers using exponential distribution start at 5 mins (10=mean), initially 2 entities in queue, max =10, 2 tellers in parallel, service time is uniform distribution btwen 6-12 mins, end sim when 100 entities have been processed. 2

16. Conditional & Probabilistic Branching Probability of a condition determines which path to take, ie from inspection 90% go to packing & 10% fail inspection, get reworked & then back to inspection What’s wrong?

17. GOON NodeGo - on • A continue node to assign direction or new attribute in series or parallel, can assign conditions

18. COLCT NodeCollect data/ statistics • Used to show mean, std dev, produce histograms • Example used to collect statistics on the completion time of a project, no histogram required, one branch from this node Label

19. COLCT NodeCollect data/ statistics • Example used to collect statistics on the completion time of a project, histogram required, 20 cells, width of 5, 1st cell is -infinity to 10, also 5 branches form this node Label

20. Control Statements • Provide info about the simulation experiment, 3 minimum statements, General, Limits & Finsih • General = GEN, NAME, PROJECT, DATE, NNRNS = NAME OF MODELER, P TITLE, DATE, # OF RUNS • Limits = LIM, MXX, MLL, MSZ, MATRIB, MLTRIB, MSTRIB, MNTRY = set max values for variables XX, LL, SZ, Attributes M, ML, MS & largest # of concurrent entities expected • Finish = FIN = end of visual slam statements

21. TV Production Ex • TVs in a production line get inspected, go to packing or need to be adjusted Packing Arriving TVs INSP Fixed TVs

22. TV Production Ex • TVs in a production line get inspected, go to packing or need to be adjusted

23. Select Node • Select are decisions on the routing of an entity, specify a Queue Selection Rule (QSR) or Server Selection Rule (SSR) Longest idle time from server Largest Average from Q Select looks ahead to choose direction

24. Exercises • 5-1 pg 157 develop a portion of the network which the time to traverse an activity is normally distributed with a mean of 10, std dev is 2, a min value of 7 and max value of 15

25. Exercises • 5-1 pg 157 develop a portion of the network which the time to traverse an activity is normally distributed with a mean of 10, std dev is 2, a min value of 7 and max value of 15

26. Chapt 5 Basic Network Modeling • Intro/ steps in the process • Single server queuing system • CREATE Node • TERMINATE Node • ASSIGN Node • GOON Node • COLCT Node • SELECT Node • EXAMPLES