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The spelled-out intro to neural networks and backpropagation: building micrograd
A 2.4-hour lecture by Andrej Karpathy about autodifferentiation, backpropagation and neural networks, on the AI shelf. It was posted to r/MachineLearning as “[P] The spelled-out intro to neural networks and backpropagation: building micrograd (Andrej Karpathy 2h25m lecture)”. It is pitched at advanced level.
Andrej Karpathy, Lecture, 2 h 26 min, 2022, on the AI shelf
Karpathy builds micrograd to explain automatic differentiation and neural-network training.
Study notes
Advanced, Built from scratch. Step 7 of 11 in From probability to modern AI
Helpful first
- Python
- Derivatives
- Basic neural networks
What it builds
- Build an automatic-gradient engine.
- Represent calculations as an expression graph.
- Apply the chain rule backwards through the graph.
Useful moments
- 0:48Micrograd and automatic gradients
- 1:22An example expression
- 3:19Backpropagation with the chain rule
Check yourself: How can a global derivative be assembled from local derivatives in a computation graph?
Notes are based on metadata, Reddit context and selected English caption passages. They are not a review of every claim in the video.







