A convolution kernel, or filter, is a learnable weighted operation that transforms input data to emphasize particular features. Its weights are optimized by an objective or loss function, producing representations that support downstream tasks such as classification or node-feature prediction. section 3.4.1
Use the kernel within a typical convolutional layer pipeline:
- Apply the filter to input data to highlight localized patterns. section 3.4.1
- Pass the filter output through an activation function for nonlinear transformation. section 3.4.1
- Optionally pool the result to reduce its size for later learning tasks. section 3.4.1
Grid and graph inputs
For an image, the kernel passes over a fixed pixel grid to identify visual patterns. In a graph convolutional network, convolution operates over graph nodes to identify patterns in graph structure or predict node features. Graph methods may be spatial, using a sliding window over the graph, or spectral, filtering a graph signal. section 3.4.1
Figure 3.11 A convolution of an input image (left). The kernel (middle) is passed over the image of an animal, resulting in a distinct representation (right) of the input image. In a deep learning process, the parameters of the filter (the numbers in the matrix) are learned parameters.
Inspect how a learned matrix passes over an image and produces a distinct representation. section 3.4.1










