@RDunn Sorry… I made a big misunderstanding for so long
Of course, the parameter “t” passed to Trunc should be the future timestep already.
As the logic goes by, in trunc() the main_code() is called and fed by the parameter “t”, and it just does not make sense to use old “t”. And *timestep simply means the delta_t from “t” and the “t_prev”
Thus, I need to modify my trunc() in all of my C-block and put this note…