Updating the model's memory at test time beat retraining its weights on all five discovery tasks and cut FLOPs by 82.8 to 84.6 percent
AspireAI community · arXiv (Liu, Chen, Zhao, Liu, Song, Wang & Bu)
Test-time training lets an open-weight model improve on a discovery task by updating its own weights mid-run, which is powerful and expensive. Test-Time Memory Evolution keeps the weights frozen and instead distills each experience into an external memory that steers the next attempt, and in a controlled comparison that swaps only the adaptation method it beat test-time training on all five mathematical discovery tasks while cutting compute by 82.8 to 84.6 percent in FLOPs and 47.7 to 58.4 percent in wall-clock runtime. The code is public on GitHub. The honest limit is scope: the five tasks are mathematical rather than general science, so the paper establishes an efficient alternative in those evaluated settings and not a replacement for weight updates everywhere.
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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.