Simulation and Modelling (BSc CSIT, CSC317): the questions likely to come

Steps in a Sound Simulation Study

A disciplined simulation study follows a sequence of well-defined stages (Banks, Carson, Nelson & Nicol):

1. Problem formulation — State the problem clearly; analyst and client agree on objectives.
2. Setting of objectives and overall plan — Define questions to be answered, performance measures, resources, time and budget.
3. Model conceptualization — Abstract the real system into a conceptual model (entities, attributes, events, state variables). Start simple and add detail.
4. Data collection — Gather input data (e.g., inter-arrival and service times) and fit probability distributions.
5. Model translation — Code the model in a simulation language (GPSS, Arena) or a general language (C++/Python).
6. Verification — Check that the program correctly implements the conceptual model (debugging). Is the model built right?
7. Validation — Check that the model accurately represents the real system, often by comparing output with real data. Is it the right model? (Loop back to step 3/4 if invalid.)
8. Experimental design — Decide which alternatives to simulate, run length, number of replications, warm-up period.
9. Production runs and analysis — Execute runs and statistically analyze output to estimate performance measures.
10. More runs? — Decide whether additional runs/scenarios are needed (loop back if yes).
11. Documentation and reporting — Document the model (program and progress) and report results.
12. Implementation — Put the recommended solution into practice.

Flowchart (described in words)

          Problem Formulation
                  |
        Setting Objectives & Plan
                  |
        Model Conceptualization <----+
                  |                   |
           Data Collection           | (No)
                  |                   |
           Model Translation         |
                  |                   |
        Verification? --No--> (fix code)
                  | Yes               |
        Validation? --No--------------+
                  | Yes
           Experimental Design
                  |
        Production Runs & Analysis
                  |
           More Runs? --Yes--> (back to runs)
                  | No
        Documentation & Reporting
                  |
            Implementation

The verification and validation steps form feedback loops back to model building, and the "more runs?" decision loops back to production runs.