Charting Flat Minima Using the Conserved Quantities of Gradient Flow

Empirical studies have revealed that many minima in the loss landscape of deep learning are connected and reside on a low-loss valley. Yet, little is known about the theoretical origin of these low-loss valleys. Ensemble models sampling different parts of a low-loss valley have reached state-of-the-art performance. However, we lack theoretical ways to measure what portions of low-loss valleys are being explored during training. We address these two aspects of low-loss valleys using symmetries and conserved quantities. We show that continuous symmetries in the parameter space of neural networks can give rise to low- loss valleys. We then show that conserved quantities associated with these symmetries can be used to define coordinates along low-loss valleys. These conserved quantities reveal that gradient flow only explores a small part of a low-loss valley. We use conserved quantities to explore other parts of the loss valley by proposing alternative initialization schemes.