arXiv Machine Learning
2d ago

Common-Mode Collapse and Recovery in Direct Feedback Alignment

Direct feedback alignment (DFA) trains hidden layers via fixed random projections of output error, but with tanh hidden units and independent sigmoid outputs, plain stochastic gradient descent can stall near a constant predictor of class frequencies. This stall is traced to the error’s common mode—a rank‑one component shared across inputs—that drives tanh units toward saturation. The study shows that calibration of the baseline readout to class priors suppresses collapse and speeds learning, while other interventions such as using Adam, adjusting feedback strength, or subtracting batch means affect the severity and recovery of collapse across MNIST, CIFAR‑10, and deeper networks.

By Varun Reddy, Bernardo L. Sabatini, Houman Safaai
arXiv AI
Sep 10

Equivariance Breaks the Learning Rate

arXiv:2609.08381v1 Announce Type: cross Abstract: Equivariant networks are commonly trained with Adam, yet recent work reports that matrix-structured optimizers such as Muon can perform better on the...

By Andrei Manolache, Mathias Niepert