Ranking Attention Heads by Gradient Norm Enables Sparse RL Fine-Tuning

SimonShaoleiDu · x · 2026-10-28

An arXiv paper (Shi, Yang, Wang, Zhu, Fazel; shared by Simon Du) studies sparse and continual RL fine-tuning of LMs via attention-head ranking and partitioning. Heads ranked by gradient norm, when fine-tuned, consistently beat lower-ranked heads and often match dense baselines across math, instruction-following, and coding tasks. Partitioning heads across tasks reduces cross-task interference, improving retention while preserving adaptation. Includes theory linking gradient norm to training effectiveness.

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