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Latent Sparse Attention makes 10-million-token context tractable by clustering keys before scoring them

AspireAI community · arXiv
Sparse attention usually trades accuracy for speed once contexts get very long, or keeps a quadratic cost hidden in the indexer. Latent Sparse Attention (LSA) hierarchically clusters keys in a learned latent space and scores the cluster hierarchy instead of every key, with a distilled variant that drops into pre-trained models and a native variant trained on next-token loss alone. On GLM-5.3-FLASH (Qwen-3.8-27B) at 10M tokens, the distilled variant sped up one attention layer 22.7x (72.4x versus full attention) in prefill and 4.6x (42.5x) in decode, and the native variant matched full-attention accuracy with a 1.6x per-layer training speedup at 128k tokens. The results are single-model measurements on one architecture, so the gains still need to hold up across model families.
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One distance function matched sparse-autoencoder features across layers and compressed feature circuits into supernodes
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.
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