I don't mean any disrespect by asking this, but asking why this was done in C++ implies you believe some other option would have been better; or at least it gives me that impression. What language should this have been done in, in your opinion?

The code was written in C++ because of performance considerations of the ODE solvers.

Does it mean you tried something like python or r and discovered that it was to slow?

Would you please stop breaking the site guidelines? We ban accounts that keep doing this, and you've been doing it repeatedly.

If you wouldn't mind reviewing https://news.ycombinator.com/newsguidelines.html and taking the intended spirit of the site more to heart, we'd be grateful.