Training the top 0.1% coordinates by Fisher info recovers ~85% of full PG gains

YouJiacheng · x · 2026-10-15

RichardYRLi summarizes a paper's core insight: on-policy, the score has zero mean, so |gi| <= sqrt(E[Var(r|x)]) sqrt(Fi) for any reward, where Fi depends only on the model.

That means you can rank coordinates before seeing rewards: training only the top 0.1% by initial Fisher information recovers 85% of the full gain on on-policy policy-gradient methods. YouJiacheng called it "very interesting."

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