Nathan Copenhaver
Simulation Modeling and Analysis
2/5/2002
Homework #3 (Lab 3. Part III)
Lab 3
Introduction
The purpose of lab 3 was to finally build a simulation model using ProModel.
The main model that I used was of a barber shop (Fantastic Dan) to simulate a general
queue problem with varying times of arrivals of customers and varying times of cutting
the person’s hair. The model was constructed following the book’s directions and then
was analyzed by following the provided questions at the end of the chapter.
Analysis
The following screen shot is from the running of my simulation.
Exercises
1.) After running the simulation for one full year:
a.) How many customers does Dan serve each day? On the average 53.26 customers a
day
b.) Average # of customers waiting? 6.38
Maximum # of customers? 15 customers
c.) Average time spent by customer? 38.49 minutes
Maximum time? 48 minutes
d.) How busy is Dan? Utilization = over 99%
Dan is busy over 99% of the time which is very good
e.) Dan should have about 3 chairs for people waiting for a haircut.
3.) The differences between occurrences and frequency is that occurrences relate to how
many people arrive at a given location and the frequency is how often or the time in
between when people arrive at the location. In the example with Fantastic Dan, the
number of occurrences was set to infinite so that customers would continuously arrive.
The frequency of the arrivals was set as a random time between 7 and 9 minutes that was
distributed in a certain manner.
4.) When developing a model you can use time units of seconds, minutes, hours and
days. These can be adjusted under the simulation options menu. In addition, to simulate
a year, for example, like we did in the Fantastic Dan simulation, you can set the number
of repetitions of the simulation to be as many as you want. I used one 8 hour day and
repeated the simulation 250 times.
5.) The two processing tables are: process and routing for customers. The process table
lets you specify who is going where and in what manner. For the Fantastic Dan example,
it specified that the customer was first going to the queue line and then to the barber after
waiting. The other table, the routing for customers table, tells where the person goes to.
For the person waiting in the queue line, it tells them to go to the barber and after they are
done with the barber, it tells them to exit the system.
6.) When an entity has gone through the entire system, it should be exited from the
system. When this happens it is eliminated from the memory of the computer but it’s
statistics remain for later computation.
7a) Entity vs. Location
The entity is the item that is going through the process (i.e. the customer) while
the location defines where the entity is at a given point in time.
b.) Locations vs. Resources
The location locates where the entity is during a certain point in time where as the
resources are items that are used up or delivered at a certain location.
c.) Attributes vs. Variables
Variables are the different things that can be changed to affect the results of the
simulation. # of customers, haircut time, etc. are examples of variables where as
attributes define the variables. Each variable has different attributes. For example, the
haircut time has the attribute that it is a random number between 7 and 9 minutes.
d.) Save vs. Save as
Save enables the user to save an existing model under the same name it was
originally saved as. Save as enables the user to change the name of the model that is
going to be saved.
After I went through the Fantastic Dan simulation, I continued on to the Poly Furniture
Factory example.
I digressed from the book on this simulation and learned how to use the gauge and
counter options to record information.
Conclusions
This lab gave me the first real look at building simulation models. I began to get
a better understanding of some of the little nuances of ProModel. Although there are
some frustrating things, I am getting better at predicting when they are going to happen.
Although I followed the book’s suggestions for this lab, I think that some investigation
on my own will result in new findings with ProModel. I am starting to see the
possibilities that I can create with the software and am starting to think about final project
topics.