SkewAdam Cuts MoE Memory by 97%
Key point
A new optimizer called SkewAdam reduces optimizer state memory for MoE training from 50.6GB to 1.29GB, enabling 6.78B MoE training on a single 40GB GPU.
Details
SkewAdam, proposed in a preprint paper published on arXiv, is a hierarchical optimizer designed to resolve the VRAM bottleneck in Mixture-of-Experts (MoE) model training.
While conventional AdamW requires 50.6GB of optimizer state memory for a 12.6GB model, SkewAdam applies differentiated precision based on parameter roles:
- Backbone (5% of total): Momentum + factored 2nd moment
- Experts (95% of total): Factored 2nd moment only
- Router (<0.01%): Exact 2nd moment
With this approach, optimizer state memory drops from 50.6GB → 1.29GB (97.4% reduction), and peak training memory drops from 81.4GB → 31.3GB, allowing a 6.78B MoE model to be trained on a single 40GB GPU without degradation in convergence quality or router stability, according to the report.
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