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Researchers propose Joint Subspace Sparse Attention for faster long-context decoding

A new paper on arXiv introduces Joint Subspace Sparse Attention (JSSA), a method to speed up long-context decoding in large language models. The technique reduces KV-cache traffic—a bottleneck for long prompts—by selecting tokens at a fine granularity while preserving accuracy. Unlike prior methods, JSSA avoids latency trade-offs by learning a shared low-dimensional subspace for query-key…

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Key points

  • JSSA learns a shared query-key subspace to improve token selection accuracy without retraining models
  • Method achieves **6.43× faster decoding** than full-KV attention at **128K context** on NVIDIA B200 GPUs
  • Works across GQA, hybrid sliding-window, and MLA architectures with **96–99% throughput retention** at 700B scale

On an NVIDIA B200 GPU, JSSA achieves 6.43× faster decoding than full-KV attention at 128K context length while maintaining reasoning accuracy comparable to model-native DSA. It also scales efficiently to 700B-scale models, retaining 96–99% of full-KV throughput even at high context lengths. The authors claim the method avoids generation-length inflation and architecture-dependent failures seen in competing sparse attention approaches.

Read the original at arXiv cs.CL · by Jiwon Song, Yoongon Kim, Jae-Joon Kim primary sourceOpen source ↗

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