Backpropagation from scratch in NumPy: let the shapes do the work
You can use PyTorch for years without ever having to write a backward pass. Then someone asks you for one in plain NumPy, on a two-layer network, and the chain rule you know on paper turns into a fight with matrix shapes. Here's how I'd write it, along with the trick that'll keep those shapes strai…
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- 2026-11-08 09:05 · DEV Community — Machine Learning
Backpropagation from scratch in NumPy: let the shapes do the work