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Modeling Worldviews

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Event Scheduling Event Graphs State Machines Activity Scanning Event Graphs and Petri Nets Process Interaction Event Graphs and Block Diagrams – PowerPoint PPT presentation

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Title: Modeling Worldviews


1
Modeling Worldviews
  • Event Scheduling Event Graphs
  • State Machines
  • Activity Scanning Event Graphs
  • and Petri Nets
  • Process Interaction Event Graphs
  • and Block Diagrams

2
System Entities
Resident Entities Variables describe the
state. Focus on cycles. (busy-idle-busy...)
Transient Entities Variables describe state
and location. Focus on flow paths.
3
Block Languages
  • Process World View
  • Focus on Transient Entity Flow JOB DRIVEN.
  • Preprogrammed blocks of code.
  • Block execution is triggered by a
  • Transient Entity entering a block.
  • Execution Controlled by Job Moves.
  • Common Languages
  • Arena (Siman), AutoMod, GPSS, SLAM (AweSim)

4
Block Languages
  • Common Languages
  • SLAM
  • SIMAN
  • GPSS (fundamental Blocks)Generate -
    Transactions enter modelQueue - Transactions
    wait for facilitySeize - Transactions take
    resourceDepart - Transactions leave
    queueAdvance - Transactions are delayedRelease
    - Transactions release resourceTerminate -
    Transactions leave the model

5
Block Languages
  • Common Languages
  • SLAM
  • SIMAN (fundamental blocks)
  • GPSS Create - Entities enter modelQueue -
    Entities wait for facilitySeize - Entities take
    resourceDepart - Transactions leave queueDelay
    - Entities are delayedRelease - Entities release
    resource (Entities may leave using
    Dispose )

6
Single Queue
GPSS
SIMAN
GENERATE
CREATE
1
QUEUE
QUEUE
1
SEIZE
SEIZE
DEPART
1
1
DELAY
ADVANCE
RELEASE
RELEASE
1
TERMINATE
7
Main Event Scheduling Algorithm for Process
Interaction
State
Initialize
Event List
Advance Clock to Time of Next Event
Change State
Execute Event
Cancel Events
Schedule Events
Remove Event From List and move tokens until
blocked or delayed
Stop
Summary Statistics
Yes
No
8
Labor Modeling Machine Interference
tool1
tool2
Oper.
Time
9
Semiautomatic Machine
GENERATE
1
QUEUE
SEIZE
SEIZE
Worker is Resource 1 Machine is Resource 2
DEPART
1
Load
TERMINATE
RELEASE
10
Single Queue with Failures
SIMAN
CREATE
CREATE
TBF
IA time
QUEUE
1
QUEUE
1
HIGH PRIORITY JOB
SEIZE
SEIZE
1
1
DELAY
DELAY
TTR
Proc. time
RELEASE
RELEASE
1
1
(Failure Processing)
(Job Processing)
11
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12
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13
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14
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15
Siman Blocks View (File/Template/Attach/Blocks) T
his is what the Arena Processes
view generates.. Eventually you will need to
understand this to use Arena In a real problem...
16
Bank Queue with Jockeying
17
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18
  • Mechanical Failures
  • CREATE
  • ASSIGN J 0
  • DUPLICATENumSegs-1 !create
    entity for each segment
  • ASSIGN J J 1
    !increment counter
  • SegNum
    J !set segment number
  • MechLoop DELAY ED(MTBF(SegNum))
    !delay for mean time btwn failures
  • QUEUE, MechFail1_Q
    !wait for machine
  • SEIZE Mach(SegNum)
    !seize machine
  • ASSIGN MStat(SegNum) 6
    !segment status to mech fail
  • State 0
  • BRANCH,2 IF,TR_Policy.EQ.2.OR.T
    R_Policy.EQ.3,PM
  • ALWAYS,M_Rep
  • M_Rep ASSIGN DTime ED(MTR(SegNum))
    !assign mean time to repair
  • TALLY MechFail_1 SegNum - 1,
    DTime
  • DELAY DTime
    !delay for mean time to repair
  • BRANCH,1 IF,TR_Policy.EQ.2.OR.TR_
    Policy.EQ.3,PM_GetR

19
Block Languages
  • Process World View
  • Transient Entity Focus Helps Animation
  • Easy to Use for Simple Applications
  • -Limited to Pre-programmed blocks
  • -Difficult to Model Complex Logic
  • -Difficult to Model Resource Failure or (say, on
    amount of time worked.)
  • -Hard to Learn Well
  • -Simulation Slows (or stops) as the System
    Becomes Congested ! ! !

20
Block Languages
  • Why the simulation slows (or stops) as the system
    becomes congested.A record of each active
    transient entity
  • must be maintained during a run.
  • e.g. Process Flow in a semi-conductor
    fabrication facility.
  • A resident entity model will run hundreds of
    times faster.

21
Block Languages
  • Resident Entity models are required to have
    practical simulations of any system with many
    active transient entities.e.g.
  • Communications Networks
  • Large Scale Manufacturing Systemsand
  • Continuous Flow Processes

22
Screen Capture of ARENA Output Svc Time 1.85
Ref Kim Branch and Jay Gillespie
23
Maximum of 100 Entities Exceeded! (Svc Time
18.5)
What is the effect on Bias of ignoring runs that
did not terminate correctly?
24
Resource/Job Driven Simulations
25
RunTime Ratios
26
Speed comparisons with Automod ASAP
27
Little Slowdown from using PUT/GET
28
Using Activity Scanning to Develop Process Models
Color tokens that represent Transient Entities
- - track these tokens paths. Parse
Activities into SEIZE, DELAY and RELEASE
Blocks.
29
Process -gt EG Mapping
  • Process World View
  • Automated SLAM to Event Graphs (Woodward and
    Mackulak, ASU)
  • Resource deadlock detection
  • SIMAN to Event Graphs (Barton and Gonzalez, PSU)
  • Premature run termination

30
  • Notes
  • Model "footprint" is "number of servers" not
    "size of queue"
  • - insensitive to congestion
    complexity grows with resources!
  • 2. Q statistics are O.K. but what about Delays?
  • - ambiguity of the mystery
    blocks
  • - Use Little's Law or
    transient entity (PUT/GET) method.

31
Conventional EG Model
(Qgt0)
Ta
(Rgt0)
Ts
SEIZE
Release
QUEUE
QQ1
RR-1, QQ-1
RR1
32
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33
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34
NOTE Can change Distns.dat while model is
running!
//CREATE block 1 - interval .5TRI.5 //DELAY
block 1 - duration 2TRI.5 //DELAY block 2
-duration 23BET.5.5
35
(QI)

tA
(SI)
tS

Enter
QI--, SI--
I(Q0gt10), QI
SI
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