Extendsim Examples

Extendsim Examples
Activity blocks
Transaction block
allow for parallel processing
Activity Multiple block
allow for parallel processing
used to model transportation
activities like mailing, emailing,
faxing docs
Model Building Steps
Determine goals
Understand process to be modeled
Draw a block diagram of process
Specifiy parameter values
Define logic of model and connections
Validate the model
Add data collection and
graphical analysis
Analyze output and draw conclusions
Measures
wait time
queue modeling blocks
utilization
resource blocks
Count Items block
number of items that route
through a certain path
various statistics blocks
don't need to be connected;
just present
collect data from blocks that
have a delay or processing
time (Operation, Stack, etc.)
Queue Stats block
from DE lib
ave queue length, max Q
length, ave wait, max wait time
Resource Stats block
from DE lib
collects from resourcetype
blocks like Repository, Labor
Pool
resource utilization
Costs Stats block
from DE lib
info on costing blocks like Operations
cost per item, cost per unit of
time, total cost
Cost by Item block
from DE lib
cost info for every block that passes
through the block (must be
connected)
cost of each item
connectors
average cost
current cost
total cost
Mean & Variance block
calcs average and std dev for
the simulation
connect to plotter to see ave over time
Activity Stats
Plotters
Plotter, DE block
four inputs on discrete events
value
time value (when it happened)
use Show Instantaneous Length
option if connected to L on
Stack
Histogram
connect L from Stack
Length column is length of queue
adjust bins; often 6
Block types
model activities
model resources
model routing
collect data
calculate stats
display output
Models share certain concepts
Selection of time units
Length of a run
Number of runs
Model verification
Model validation
Items
Import block
generates arrivals
specify arrival pattern
specify amount per arrival
alternative would be Generator block
Input Data block
changing arrival rate based
on exponential distribution
Program block
schedule specific arrivals at
specific times
Attributes
set via
Input block
easiest
Operation block
Repository block
Labor Pool block
Program block
Set Attribute blocks
carry through entire process
Prioritizing items
Stack block
choose type of stack
other methods?
Repository block
holding area (think inbox)
can start with some items
assign attribute and priority as
they leave
can't measure wait time; use
Stack block instead
items leave FIFO
Export block
Operations block
simulates an activity
delays item passing through
delay time constant unless
Input Random Number is
attached
Transaction block
alternative to Operations for
modeling parallel servers
also used to model multiple
simultaneous activities
Batching
Operation block
Batch block
batch up to three items into a
single output
Unbatch block
separate up to three item
used to separate resource from the item so
item can go forward and resource back to
pool
when batch/unbatch, check
Preserve Uniqueness
Special Blocks
Executive
must farthest to the left
required for all simulations
controls timing and passing of events
Input Random Number block
from Generic lib
uses probability distributions
connect to D input on
Operations block (delay)
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