FIGURE
13 Three-stage Saak architecture
Multiple Saab structures were used in cascade in PixelHop architecture.
The purpose is to learn features from different neighborhood sizes
(hop). Like Saab, earlier layers use a higher energy ratio, while later
layers use a low energy ratio. Frobenius norms of the difference of the
two-covariance matrix were used for faster filter convergence, which
rapidly converges to zero. For the CIFAR-10 dataset, four cascaded Saab
structures were implemented. The patch and filter sizes were 4x4, 4x4,
2x2, and 2x2 for all the PixelHop units starting from the first to the
fourth structure.