CSci 405-01: Computer Simulation
CSci 581-01: Special Topics on Computer Simulation
Fall Semester 2001

Assignment #2
Due Monday, 5 November (Revised Date)

Sandwich Shop Simulation

Prepare this assignment by the above deadline in accordance with the instructions given in the Professional Conduct and Assignments sections of the Syllabus.

In this assignment your task is to develop a simulation model and program for a sandwich shop. (The picture I have in my mind is a Subway sandwich shop similar to the ones in Oxford or perhaps the Blimpie's sandwich counter in the Union Food Court.)

The goal is, of course, to maximize the long-term profit. In general, that means you want to be able to maximize the number of sandwich orders the shop can handle while keeping the cost of operation at a minimum (in particular the number of workers as small as possible). Assume the shop is in a situation where getting repeat business is important to long-term profitability. Thus customer satisfaction will be important issue. One factor in customer satisfaction is the speed with which an order is fulfilled.

In the shop, a customer waits until it is his or her turn, then places the order, then waits for the order to be prepared, then pays and leaves.

Behind the counter, the process of fulfilling sandwich orders consists of the following "sequence" of steps for each sandwich:

1. Accept the sandwich order.
2. Assemble the chosen bread, meats, and cheeses.
3. Heat the sandwich if required.
4. Dress the sandwich with the requested vegetables and condiments.
5. Package the sandwich order.
6. Accept payment for the order.

You make the following observations about the process of fulfilling sandwich orders:

• All steps of the process require a worker to carry it out, except perhaps the heating step, which only requires a worker at the beginning and the end of the step.
• Several sandwich orders may be in the process of being prepared at one time.
• At least one worker is required to fulfill an order. However, there may be several workers, each working on various steps of the process.
• It is possible for sandwich orders to be fulfilled in a different order than placed. For example. a hot sandwich may get behind a later cold sandwich order.

Given the goals stated above and perhaps other goals you want to investigate, define and collect appropriate performance measures.

Define and carry out a series of experiments to determine the optimum staffing given a particular workload. (I may give you information about workload later.)

Undergraduate students may assume that the supply of ingredients is unbounded, that no more than one sandwich may be in any one step of the process at time, that there is only one sandwich in each order, and that the interaction points with the customer are only at the beginning and the end.

When this assignment is complete, submit:

• a description of your model in text and drawings,
• a paper listing of your program source code and outputs from your experiments,
• a diskette containing your program source code and instructions on how to run your model.

Be sure that all items submitted are clearly labeled with your name, class, and the assignment number.

Additional Work for Graduate Students

Graduate students must add at least one of the following features into the model:

• The supply of ingredients is not unbounded. If an ingredient is depleted, then the process must be delayed until the ingredient is resupplied from the storeroom.
• More than one sandwich may be in work at a particular step at a particular time. For example, there may be two workers doing initial assembly of sandwiches or a worker may be dividing his or her time between two sandwiches.
• A sandwich order may consist of several sandwiches that work their way thru the process independently and are collected together in the packaging step.
• There are more interaction points with the customer. For example, in the "dressing" step, the worker may ask for further instructions on what items to include or in the packaging step the worker may ask what side items the customer wants.
• Structure the model so that various workflow policies can be investigated. For example, one policy would be for a worker to carry out all steps of an order fulfillment. Another policy might be assignment of workers to specific steps. Another policy might be, under heavy workload situations, to work on a cluster of orders at one time instead of working them singly. Etc. Investigate at least two different policies.

The model should be appropriately instrumented and appropriate experiments should be carried out.

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