Halving the token budget made RLVR training faster AND better, by choosing both which prompts to sample and when to stop
AspireAI community · arXiv (NeurIPS 2026)
Reinforcement learning with verifiable rewards burns hundreds of thousands of tokens per training step, and most budget-aware methods control only one knob - either how many rollouts a prompt gets or how long each rollout runs. DUET is a lightweight layer over GRPO that tunes both together, using a pre-rollout surrogate of prompt informativeness to set rollout counts and a marker-gated abort rule with importance reweighting to decide when to stop them. On Qwen3-1.7B trained on MATH it beats full-budget GRPO and three budget-aware baselines for a 1.62x wall-clock speedup, and using only half the token budget it still outperforms every baseline running at full budget, reaching a 2.51x speedup. The authors check it on Qwen3 from 4B to 14B and on Llama-3.2-3B-Instruct, and report the gap over the strongest baseline widening as the budget tightens. It is only on par with the best baseline in the scientific Q&A domain, and the evaluation covers reasoning-style benchmarks rather than long-horizon agentic work.
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Two sparse-autoencoder analyses have resisted scaling: matching semantically similar features across layers, and compressing large feature circuits into interpretable supernodes. This paper argues both are the same underlying problem, estimating semantic distances between SAE features that sit on different activation manifolds. Its representation treats each feature not as a single decoder vector but as an activation-weighted distribution over the hidden states expressing it, projects those distributions into a shared reference space, and compares them with Wasserstein distance. The representation is proved invariant to activation rescaling and stable under perturbation, and recovers true matches under finite-sample margin conditions. Empirically it outperformed decoder-vector and LLM-based baselines and captured subtle functional distinctions between related features, and it compressed large feature circuits into interpretable supernodes automatically. The limitation is that this is interpretability tooling: the paper demonstrates better feature matching and circuit compression, not that downstream interpretability claims become more accurate.