DiscoverLessWrong (30+ Karma)“How Well Does RL Scale?” by Toby_Ord
“How Well Does RL Scale?” by Toby_Ord

“How Well Does RL Scale?” by Toby_Ord

Update: 2025-10-22
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Description

This is the latest in a series of essays on AI Scaling.
You can find the others on my site.

Summary: RL-training for LLMs scales surprisingly poorly. Most of its gains are from allowing LLMs to productively use longer chains of thought, allowing them to think longer about a problem. There is some improvement for a fixed length of answer, but not enough to drive AI progress. Given the scaling up of pre-training compute also stalled, we'll see less AI progress via compute scaling than you might have thought, and more of it will come from inference scaling (which has different effects on the world). That lengthens timelines and affects strategies for AI governance and safety.

The current era of improving AI capabilities using reinforcement learning (from verifiable rewards) involves two key types of scaling:

  1. Scaling the amount of compute used for RL during training
  2. Scaling [...]

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Outline:

(09:46 ) How do these compare to pre-training scaling?

(14:16 ) Conclusion

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First published:

October 22nd, 2025



Source:

https://www.lesswrong.com/posts/xpj6KhDM9bJybdnEe/how-well-does-rl-scale


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Narrated by TYPE III AUDIO.


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Images from the article:

Bar graph titled
Graph comparing GPT-5 and OpenAI o3 accuracy on PhD science questions.
Graph comparing GPT-5 and OpenAI o3 software engineering performance across token lengths.
Arc AGI-1 leaderboard showing AI model performance versus cost per task.
Graph titled
Two scatter plots showing
Graph comparing estimated inference costs against AI model performance (AME 2025) metrics.  The plot shows two model series (o1 and o3) with different performance levels (low/medium/high) and their costs, with a
Performance graph titled
Two line graphs showing
Graph showing math performance comparing base model versus RL post-training.  The graph displays performance improvements across token usage, with

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“How Well Does RL Scale?” by Toby_Ord

“How Well Does RL Scale?” by Toby_Ord