CSC 222: Computer Programming II
Spring 2005

HW6: Queues and Simulation

For this assignment, you are to complete the bank simulation project, which uses a queue to simulate customers arriving and being served in a small bank. Recall the following assumptions:

The following classes have been provided for you: Customer, Server, and BankSimulator.

Part 1: Implementing ServiceCenter

To complete the simulation, you are to implement the ServiceCenter class. An object of this class contains a single Server object for serving customers, and a queue of customers waiting to be served. The addCustomer method should create a new customer, add him/her to the waiting queue, and display information about the customer. The doBusiness method should increment the current time and perform a step in the simulation, checking to see if the teller has finished with a customer and, if so, whether a new customer can be served. It should also display a message if the teller finishes or begins serving a customer. In addition, the getTime method should return the current simulation time, and customersRemaining should return true if there are any customers currently in the system.

For example, the output of the simulation should look like the following:

What is the time duration (in minutes) to be simulated? 10 What percentage of the time (0-100) does a customer arrive? 30 2: Adding customer 1 (job length = 4) 2: Serving customer 1 (finish at 6) 4: Adding customer 2 (job length = 3) 5: Adding customer 3 (job length = 1) 6: Finished customer 1 6: Serving customer 2 (finish at 9) 9: Adding customer 4 (job length = 3) 9: Finished customer 2 9: Serving customer 3 (finish at 10) 10: Finished customer 3 10: Serving customer 4 (finish at 13) 13: Finished customer 4

Part 2: Maintaining Statistics

Once you have the simulation working correctly, add a method named displayStats that displays statistics on the simulation. You should modify the ServiceCenter class so that it keeps track of:

  1. the number of customers whose jobs have been completed,
  2. the average waiting time for all customers whose jobs have been completed, and
  3. the longest waiting time for any customer whose job has been completed.

The displayStats member function, when called, should display these statistics in a readable form. Add a call to the main method of BankSimulator so that displayStats is called at the end of the simulation to display statistics.

Part 3: Analysis

Once you have your bank simulation program working, answer these questions:
  1. Assuming a banking day of 8 hours (480 minutes), how many customers would you expect to serve if the arrival probability were 20%. Do your simulations support this answer?
  2. Assuming a banking day of 8 hours and an arrival probability of 15%, what is the average wait time for customers at the bank. Run several simulations and comment on the consistency of the results.
  3. Assuming a banking day of 8 hours, what arrival probability can the bank handle and still keep the maximum wait time for customers under 10 minutes. Explain how you came up with this number.