Defining a loss function comes to mind. Checkout JAX[1] or Autograd[2]. As this is essentially a different programming paradigm there are a ton of opportunities, but it is fresh enough such that there is little to no history of software engineering differentiable programs. Design patterns, rules of thumb, and standard practices have yet to be defined.

[1] https://github.com/google/jax

[2] https://github.com/HIPS/autograd