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Chapter 5 · Advanced Modeling and Deep Learning·v2.0.0·Updated 6/3/2026·~12 min

What's changed: Deepened MLS-C01 Chapter 5 (output-loss pairing/Adam/training diagnosis, CNN/RNN/Transformer internals & task mapping, transfer-learning stages/Ground Truth/distributed training/mixed precision + tables, scenarios, FAQ, traps; ja figures)

5.1Neural Network Fundamentals

Key points

The foundation of deep learning—understand layers and neurons, activation functions (ReLU/sigmoid/softmax), backpropagation, learning rate/epochs/batch, and the vanishing gradient.

A neural network is built from neurons arranged in layers, adds non-linearity via activation functions, and learns weights via backpropagation.

5.1.1Structure and training

Diagram of neural network basics: neurons in an input layer, hidden layer (ReLU activation), and output layer are connected; training does forward pass → loss + backpropagation → gradient descent to update weights, involving epochs, batch, and learning rate (LR); layers of neurons with activation add non-linearity and backprop learns the weights.
Neural network basics
  • Activation: ReLU (common in hidden layers), sigmoid (binary), softmax (multi-class probabilities).
  • Backprop + gradient descent: compute loss, backpropagate gradients, and update weights.
  • Learning rate/epochs/batch: too-high LR diverges, too-low is slow; epochs are passes over all data.
  • Vanishing gradient: deep nets lose gradients; mitigate with ReLU and batch normalization.
Exam point

Common on MLS-C01: multi-class output = softmax, binary = sigmoid, hidden activation = ReLU (resists vanishing gradient), and too-high learning rate = divergence/oscillating loss. If loss won’t decrease or oscillates, suspect the learning rate first.

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