Before describing how you specify the properties of an External pathway, it is useful to summarize the general information flow between GoldSim and the External pathway function.
The following information is automatically passed by GoldSim to the External pathway function when it is called:
•any (optional) input arguments that you wish to send to the function (you will always need to pass the current time, but need not send any additional inputs);
•the number of species in the model;
•the number of mass flux links into the pathway;
•the number of mass flux links which GoldSim expects to be returned from the pathway;
•a flag indicating whether all species fluxes in the mass flux links into the pathways are zero for the current call (which you could use to internally instruct the External pathway to skip various calculations); and
•a vector for each mass flux link into the External pathway indicating the quantity of mass of each species passed to the External pathway since the last time it was called (typically one timestep).
GoldSim expects the following information to be returned from the External pathway function when it is called:
•any (optional) output arguments that you wish to return from the function (you need not return any additional outputs);
•a vector for each mass flux link out of the External pathway indicating the quantity of mass of each species passed from the External pathway since the last time it was called (typically one timestep).
The details regarding the manner in which this information is passed is provided in Appendix C of the Contaminant Transport Module User’s Guide.