LAB 2 ISEN 424: SYSTEMS SIMULATION

Dr. Eduardo Perez-Roman

Dept. of Industrial & Systems Engineering

Texas A&M University

Email: eduardopr@tamu.edu

Basics of Simulation: Terminology

• Entity – object of interest in the system

• Attribute – property of an entity

• priority

• job type

• color

• size

• arrival time

• Variable – information representing some system

characteristic

• cost

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Setup Working Environment

• Create an isen424 folder in your Home Directory, e.g.

H:/Documents/isen424

• Create a folder for the current lab, e.g.

H:/Documents/isen424/lab2

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Start & Setup Arena • Open ARENA from the Start Menu

• Save the file to your lab directory with the following convention:

lab#-lastname.doe, e.g. H:\Documents\isen424\lab2\lab2-

perez.doe

• On the top toolbar, select Run / Setup…

• Project Parameters: Project Title: lab; Analyst Name: First Last;

Description: empty; Statistics Collection: select none

• Reports: At the end of the simulation run, display default report…

Always, Default Report: SIMAN Summary Report (.out file)

• Replication Parameters: Change based on the assignment/task

• Close this dialog box

• Deselect Run / Run Control / Batch Run (No Animation)

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Arena Modules

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Attributes Element

• Property of an entity (color, size, arrival time)

Attributes

Assign Block Assign

• The ASSIGN block allows the assignment of a value to user-defined entity attribute.

• TNOW- miscellaneous system variable – current clock time – used to calculate cycle times

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Assign: Attributes • Property of an entity, possessive

• Examples: priority, type, arrival time

• Suggested Naming Scheme: lowercase first word, no

spaces, uppercase first letters of next words

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Assign

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Branch Block

• Controls the flow of an entity

through a set of branches.

Maximum number of

branches to take

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Statistics

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Statistics

• Types:

1. Count

2. Tally

3. Time Average Statistics / Time

Persistent Statistics

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Statistics • Tally: data for which there is a natural first, second, third ….

observations

• Since values of them are “tallied” when they are observed, Arena

called them tally statistics (i.e. cycle time)

• TAVG: defined by Arena to obtain the average across replications of

tally statistics.

• Time Average Statistics

• Weighted average of the WIP weighted by the proportion of time

during the run that the system had that WIP

• DAVG defined by Arena to obtain the average across replications of

Time Average Statistics

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Counters Elements

• The COUNT block increments the counter specified by

Counter ID by the value of the operand Counter

Increment

• Examples: number of units completed

ctPart1

ctPart2

ctPart3

ct

Tallies

Count Block Tally

• The COUNTERS element specifies parameters for

counters that may be used to keep integer count statistics

on events occurring in the model

Counters

Count

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Tallies Elements

• The TALLIES element defines all information needed

for TALLY blocks in a SIMAN model.

ctPart1

ctPart2

ctPart3

ct

Tallies

Tally Block Tally

• This block tallies the complete set of internal cost and

time attributes for the entity.

• Examples: cycle time, cost

• Arena defined variable TNOW for cycle time

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Sets Element

• Defines a group that may be referenced via a common

name and a unique index.

• Can be used in combination with tallies element

ctByPart

Sets

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DStats Element

NR(machine1)

NR(machine2)

NR(inspector)

DStats

• Used to obtain time-persistent statistics in a discrete

system. • Example : resource utilization, work in process

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Statistics – Multiple experiments

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Statistics

• Replications

• Use several independent, statistically identical runs and investigate

how the results change from run to run

• Each run uses separate input random numbers to generate the data

used to drive the simulation (i.e. inter-arrival and service times)

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Outputs Element • DAVG for time persistent stats

• TAVG for tallies and counters

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