At the time I worked in Machine Learning (94-95) I was unaware of AD and my professor who built the objective function also determined its analytic derivative m

At the time I worked in Machine Learning (94-95) I was unaware of AD and my professor who built the objective function also determined its analytic derivative manually. I didn't learn about it until a few years ago and was amazed because I spend much of the late 90's learning enough Mathematica to make my own analytic derivatives.