Setting up your simulator

The parameters of a computer simulator are often poorly defined, and their ranges for a particular application can be mysterious. But the negative consequences of getting these ranges wrong, either too small or too large, endure through all subsequent uses. So ‘setting-up’, by which I mean the process of adjusting the individual ranges in the light of a few carefully-chosen observations, is a crucial first step. Happily there is a relatively straightforward process for setting-up, based on the notion of ‘implausibility’, and making use of simple calculations and visualisations. This process works much better if the analyst is able to proceed sequentially, through several waves of runs. The paper also considers the extension of this process to different types of simulator: simulators with large fields of parameters, stochastic simulators, and expensive-to-run simulators.