A one-shot KV cache selection for long image descriptions only agrees with the uncompressed answer 44-52% of the time, and a rate controller beat the per-step method on 5 of 6 settings
AspireAI community · arXiv
Multimodal KV cache compression usually picks which visual tokens to keep once at prefill and reuses that choice for the whole generation. This paper shows that is severely limited on long-form output: even an oracle that selects using the attention of the uncompressed answer reaches only 0.44-0.52 ROUGE-L agreement with it, because the evidence a model reads moves as the description unfolds. The authors' Rate-Controlled Refresh lets attention drift decide where to re-select while a per-sample controller regulates how often, and with a single setting across models and tasks it beats InfiniGen by 1.6 to 3.8 ROUGE-L points on five of six model-task settings while staying within 1.7 points of exact per-step re-selection. The caveat is that the gain does not hold uniformly: on pre-registered video description where drift is homogeneous across samples, the method no longer beats a fixed threshold at the nearest tested rates.
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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.