Advanced Deep Learning Interview Questions, issue 7, Mar 28, 2026
The Vanishing Gradient Trap
Senior Machine Learning Engineer interview at Google DeepMind, and the interviewer asks:
“Your team is migrating a deep model’s hidden layers from Sigmoid to ReLU. Why are we doing this?”
Focusing only on gradient flow ignores that Sigmoid destroys forward-pass geometry, starving deeper layers of usable spatial signal.
The full answer, with the mechanism and the arithmetic, is for paid subscribers on Substack.