Robuta

https://openreview.net/forum?id=D8WJ7gQEG1 Sion's Minimax Theorem in Geodesic Metric Spaces and a Riemannian Extragradient Algorithm |... Deciding whether saddle points exist or are approximable for nonconvex-nonconcave problems is usually intractable. We take a step toward understanding a broad... sion s minimax theorem