Code associated with article: Halloran, L.J.S., P. Brunner, & D. Hunkeler (2019). "COMPEST, a PEST-COMSOL interface for inverse multiphysics modelling: Development and application to isotopic fractionation of groundwater contaminants," Computers and Geosciences. https://doi.org/10.1016/j.cageo.2019.02.001