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Classification head

As explained in Deep Learning with Python, Third Edition

The final neural-network layer that maps learned representations to class predictions.

A classification head is the task-specific ending of a neural network: it receives learned representations and turns them into class predictions. The earlier network can remain a reusable backbone, while the head adapts it to a particular classification problem. section 15.4.2 section 8.3.1

IMDb sentiment classification

A RoBERTa backbone produces a sequence of contextual token representations. Selecting the first token's representation supplies one vector per review; dropout and a 768-unit ReLU Dense layer refine it, and a final Dense layer with one sigmoid output predicts the binary label. section 15.4.4

A practical classification head commonly involves:

  • Condense the backbone output to one representation per sample, using contextual first-token selection for RoBERTa or global average pooling for convolutional features. section 15.4.4
  • Treat the head as a tunable design choice: vary representation-layer count, unit count, activation, or loss and compare validation and test accuracy. section 4.1.6

How Deep Learning with Python, Third Edition covers it

How deep it goes
Explains pooling, projection, dropout, activation, loss, and architecture experiments, but does not derive classifier internals mathematically.
Examples
Uses IMDb sentiment classification with RoBERTa and binary image classification with an Xception feature extractor.
What it assumes
Assumes familiarity with neural-network layers and training while demonstrating representation pooling and head construction concretely.
What you can do after
Build it from scratch by attaching pooling, Dense, dropout, activation, and loss components to a model backbone.
How it connects
Connects classification heads with backbones, feature extraction, pooling, pretrained models, and fine-tuning.

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This explainer was generated by Manning's knowledge graph from the text of Deep Learning with Python, Third Edition. The section links point to the parts of the book it draws on.