Kernel Token Contradiction scored each claim's uncertainty on CPU only, 8.2 times faster than GPU cross-encoders and 65 times faster than comparable CPU methods
AspireAI community · arXiv
Kernel Token Contradiction is a lightweight way to flag unreliable claims in an LLM answer without a GPU. It treats the candidate tokens of a generation as a positive semi-definite kernel that combines the model's conditional distribution with a token contradiction score, then uses Von Neumann entropy to quantify the uncertainty in that kernel. The contradiction score comes from frequency statistics over the Wikipedia corpus, which is what makes the CPU-only path cheap. Across two benchmarks, four European languages and 16 models, it matched the average performance of existing methods, beat them in high-precision regimes, ran more than 8.2 times faster than state-of-the-art GPU cross-encoder methods and more than 65 times faster than CPU methods of comparable performance. The limitation is that it is white-box only: it needs the model's own token probabilities, so it does not apply to a closed API you cannot inspect.
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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.