In this part, "Automatic differentiation" is regarded to be superior to naively inlining all definitions. I did a little search, trying to understand what is all about.
My understanding: Technically, it's not Symbolic Differentiation, for it's not doing the symbol manipulation directly. It's more like one innovative method to accomplish Symbolic Differentiation. Since computer is very fast for dealing with elementary arithmetic, the efficiency is pretty high.
The attempt to express the ODEs has no positive result so far.
Mingkun Yang
