store int cols as int and not double (View(transpose(POP[, lapply(.SD, pryr::object_size)], keep.names = "rn")[, V1 := V1/1024^2])). Ensure that c++ side gets the col type it is expecting.
Pass a seed for random number instead of the column to the c++ side.
Check whether disease status needs to be stored in .fst for the initial synthpop. I.e. it may get recalculated for the baseline scenario