ReLU/SiLU have a zero-mean "bug" — fixing it improves LLM and ViT training

ZimingLiu11 · x · 2026-10-31

Ziming Liu (MIT) argues that common asymmetric activation functions (ReLU/SiLU/GeLU) suppress the negative side more than the positive, so post-activation distributions have positive mean even with zero-centered inputs. This small "bug" causes pathological loss landscapes, loss spikes, and representation overshooting; switching to shifted, symmetric activations improves training in both LLMs and ViTs.

Related event: Ziming Liu: Popular activations have non-zero mean; negative shift stabilizes training(8 posts)→

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