Verification is the process of building the model correctly and implementing it with good input and structure.
Figure above illustrates Model Building, Verification and Validation
After the phase of model building, the purpose is to ensure that the conceptual model is represented accurately in computerized representation or computer simulation.
I) Program Testing
Verify initial condition
Independent tester for testing a model
Walk through or trace program
Follow good programming practices
Use graphical representation
Create internal model partitions
II) Simulation knowledge
- When to monitor and display information
- Attention to a particular block or entity
- Values of which components are required
- When to suspend or pause simulation
- Close examination of model o/p
Different ways to verify are:
A) Examination of model output for Reasonableness
- Test simulation model for reasonableness under extreme value conditions
- Test simulation model under variation in parameter
- Does response follow direction of the change?
- Examine inputs and outputs of subsystems
- compare test conditions to analytical results
- Check current contents and total counts
B) Current contents and total counts
- Current contents refer to no of transactions in each of the system at a given time.
- Total count refers to number of transactions that have entered each part of system at a given time.
If current contents in some part of s/m is high $\rightarrow$ Large no of transactions are delayed
If current contents increases in linear fashion $\rightarrow$ queue is unstable
Total count of subsystem is zero $\rightarrow$ No transactions entered the subsystem
Current count = total count - 1 $\rightarrow$ Entity captured resource but never freed it
C) Performance measure
The aim of simulation is to estimate long run measure of performance.
If a simulation is predicting one performance measure correctly, then there is an increase in confidence in the model's prediction ability for related performance measures.
Model builder should
- Comment for operational model
- Definition for all variables and parameters
- Description of each major section of the operational model
It clarifies logic of a model.
It is detailed computer printout of the stale of the simulation model over a period of time. It is design for use in simulation program to get value of selected variables each time the simulation clock is advanced selective trace includes.
- Trace set for specific location
- Trace set for particular entity
- Trace set for occurrence of a particular condition.