Lecture 11 expands a logistic unit into a multilayer network: linear layers produce z, activations produce a, and multiple neurons jointly learn a feature transform trained through a final loss.
Lecture 12 treats a network as a computation graph: the forward pass stores intermediates, the backward pass propagates upstream gradients, and local linear, activation, and softmax rules compute every parameter gradient efficiently.
Week 6 has two halves. The pre-recorded material teaches neural networks: how one unit computes, why hidden layers are needed, the softmax, classification and language modeling with word vectors, and backpropagation. The live lecture introduces large language models: what they are, the three architectures, why so many tasks can be recast as continuing text, how to sample, how pretraining works, and how a model becomes an assistant.
Lecture 3 decomposes neural-network training into computation graphs, local derivatives, and the chain rule: the forward pass computes a result; backprop accumulates gradients from the output so every parameter knows how to move.
HW5 avoids automatic differentiation so learners must track forward shapes, caches, and backward gradients themselves.
HW7 builds on HW5 backpropagation to address deep-model architecture and training failures, emphasizing diagnosis over merely adding layers.