# {{Optim}} and {{Reopt}} modules

The **{{Optim}}** and **{{Reopt}}** libraries (cf [](#optimizer_module) and [](#reoptimizer_module)) 
are dedicated to optimisation and model calibration. Model calibration consists in setting up the 
"degrees of freedom" of a model so that future simulations will optimally fit an experimental 
database. The optimisation is a complex procedure and several techniques are available to perform 
single-criterion or multi criteria one, with and without constraint.