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Pooling

As explained in Graph Neural Networks in Action

A graph operation that reduces a collection of representations to a smaller representation, often for graph-level prediction.

Pooling reduces the size of learned representations so later learning tasks can work with a smaller output. In graph neural networks, it is mainly used to turn node-level outputs into representations for graph-level prediction. section 3.4.1 section 3.4.2

Use pooling as the size-reduction stage after feature transformation and activation:

  • A convolution or message-passing operation transforms local graph information into learned representations. section 3.4.1 section 3.4.2
  • An activation function adds the nonlinear transformation needed for a multilayer model to remain more expressive than a linear model. section 3.4.2
  • Pooling then reduces the overall output size for graph-level tasks; node-prediction workflows can omit it. section 3.4.2

Grid and graph intuition

In a CNN, a layer follows the pattern filter → activation function → pooling, reducing an image-derived representation for downstream classification. A GNN applies the analogous reduction after graph convolution or message passing when the target is a whole graph rather than an individual node. section 3.4.1 section 3.4.2

How Graph Neural Networks in Action covers it

How deep it goes
Defines pooling and places it in CNN and message-passing pipelines, but does not explain pooling operators or implementation details.
Examples
Illustrates pooling through CNN image processing and reduced graph representations for whole-graph prediction.
What you can do after
Evaluate whether a graph-learning pipeline needs size reduction for graph-level prediction or should omit pooling for node prediction.
How it connects
Connects pooling to convolution, activation functions, message passing, aggregation functions, node prediction, and graph-level learning.

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Related concepts

This explainer was generated by Manning's knowledge graph from the text of Graph Neural Networks in Action. The section links point to the parts of the book it draws on.