The PEST suite of programs includes SENSAN, a model-independent sensitivity analyzer. Like PEST, SENSAN communicates with a model through the model’s own input and output files. Thus SENSAN can be used without the user having to make any alterations to the model whatsoever.

Prior to running SENSAN a modeler simply identifies adjustable parameters on generated numbers in model input file(s) in which he/she is particularly interested. The user then provides SENSAN with different sets of parameter values and SENSAN runs the model for each set, recording parameter values and model outputs in spreadsheet format for easy later analysis. There is no upper limit to the number of sets. Relative model output variations as well as sensitivities of model outputs to parameter changes are also recorded.

While built for sensitivity analysis, SENSAN’s use is not restricted to this. SENSAN provides a modeler with the ability to carry out hundreds of model runs while leaving the computer unattended, keeping the computer busy all night or even all weekend. Furthermore SENSAN allows a user to complement each model run with a system command. Thus, if desired, output files corresponding to some or all model runs can be saved independently under separate names for later analysis.