SimpleHC matches mHC performance with only 2.4% extra training time, study finds

dots-studio · hf · 2026-11-13

A systematic study of Hyper-Connections (HC) architectures from SJTU, Xiaohongshu's Dots Studio, PKU and others identifies two effective interaction groups: learned read/write gating without mixing, and unconstrained mixing with fixed gates—each alone matches mHC performance. Repeated access to the expanded residual state is pinpointed as the main source of training overhead. The resulting SimpleHC removes residual mixing and simplifies execution via shared memory access: layer-specific gates share a group-entry state enabling batched reads and deferred writes, with scalar corrections exactly preserving sublayer contributions. At the largest tested scale (15B–30B MoE), SimpleHC adds only 2.4% end-to-end training time over a vanilla residual baseline, matches mHC performance, and shows smoother gradient dynamics.

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