Researchers introduce SkewAdam, an optimizer designed for mixture-of-experts (MoE) models that allocates different state types to distinct parameter populations to drastically reduce memory usage. By assigning float32 momentum and factored second moments to the backbone, factored second moments to experts, and exact second moments to the router, SkewAdam reduces optimizer state from 50.6 GB to 1.29 GB for a 6.78B-parameter model.
- Peak training memory drops from 81.4 GB to 31.3 GB, fitting within a 40 GB accelerator budget.
- SkewAdam achieves a validation perplexity of 108.4 over 82M tokens, outperforming AdamW (126.8), Muon (120.2), and Lion (393.7).
- The memory savings are achieved without accuracy loss; the performance gain stems from retaining momentum rather than the tiered allocation itself.
The results suggest that where optimizer state is allocated matters as much as its volume, enabling efficient training on hardware with limited memory.