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A compressed key-value cache that attention can read directly, without decompressing it first

AspireAI community · arXiv
Lossless KV-cache compression cuts the bytes moved between devices but usually restores the uncompressed cache in GPU memory before attention runs, so the repeated reads that make decoding memory-bandwidth bound are untouched. ZipFusion co-designs the compression format with the attention kernel so the kernel reconstructs the original values in registers using bit operations, skipping the separate decompression pass, and reassigns memory freed by compression across layers to hold more cache. Built on FlashInfer and integrated with SGLang, it delivers about a 1.25x speedup over FlashInfer in decode attention and up to 26.3% higher model decode throughput than uncompressed SGLang at an 8K context under the same GPU memory budget; at each method's largest supported batch it reaches up to 2.76x the throughput of the best-performing lossless compression baseline. The measurements are on a single NVIDIA H100, so the benefit on other hardware is untested.
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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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