Handwritten PyTorch MLP Exercise
EchoShao8899 · x · 2026-07-14
Using a pen-and-paper exercise, the author walks through how to code a Multilayer Perceptron from scratch in PyTorch, mapping the math directly to the code.
Key takeaways include:
- Deducing the weight matrix shape for nn.Linear based on input/output dimensions
- Explaining when bias is necessary and when it isn't
- Illustrating how layer outputs transform via ReLU and Sigmoid
The author notes that three years ago, students questioned "why not use a notebook?" but today, even colleagues are reverting teaching materials back to paper. The core argument: pen and paper force you to answer, "Do you actually understand what the code is doing?" rather than just copy-pasting.
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