Using process reward scores to steer candidate resampling let a 20B open model beat a 120B model on AIME25, HMMT25 and GPQA Diamond
AspireAI community · arXiv
Deep-think pipelines generate, refine and aggregate populations of candidate solutions, but they can amplify errors when the correctness signal at inference time is unreliable, suppressing correct minority solutions and burning compute for nothing. PRISM introduces a process-reward-model-guided inference algorithm that uses step-level verification to drive population resampling, proposal acceptance and solution aggregation, with a companion PRM-score-vote method for the aggregation step. Paired together, the authors report 90.0 percent on AIME25, 75.4 percent on HMMT25 and 71.4 percent on GPQA Diamond with gpt-oss-20b, exceeding the much larger gpt-oss-120b on all three, while preserving competitive accuracy even when the initial population contains few correct candidates. The practical caveat is that the gains lean on a process reward model doing the verification, so the extra inference cost and the reward model's own blind spots are part of the trade.
Read the story and explore more from the AspireAI community.
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.