Reproduce “QK-Normed MLA: QK normalization without full key caching” on OpenResearch

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About this paper

Yizhou Han, Yao Zhao, Jun Zhou, Longfei Li, Ruoyu Sun

The paper introduces QK-Normed MLA, an algebraic rewrite that moves fixed RMS-normalization weights into the query projection and caches one inverse-RMS scalar per token and KV group instead of expanded keys. In matched 400M-parameter, 100B-token runs, it stays below QK-Clip in training loss; accuracy averages 46.33 versus 44.75, but results are not frontier-scale.

Key insights

  • RMSNorm can be decomposed into static, feature-wise affine weights and a dynamic, scalar Root Mean Square (RMS) statistic, which allows for separate handling.
  • The static affine weights of key-side QK RMSNorm can be absorbed into the query projection, shifting a key-dependent operation to the query side during computation.
  • Instead of caching full normalized keys, only a small scalar inverse-RMS statistic needs to be stored per token in the cache, preserving MLA's memory efficiency.

Summary by alphaXiv.

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