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How Sparse Attention Approximates Exact Attention? Your Attention is Naturally n^C-Sparse

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arxiv 2404.02690 v2 pith:F2G5NSHZ submitted 2024-04-03 cs.LG cs.AIcs.CL

How Sparse Attention Approximates Exact Attention? Your Attention is Naturally n^C-Sparse

classification cs.LG cs.AIcs.CL
keywords attentionsparseentriesapproximatesbulletcomputationalphaefficient
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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Sparse Attention is a technique that approximates standard attention computation with sub-quadratic complexity. This is achieved by selectively ignoring smaller entries in the attention matrix during the softmax function computation. Variations of this technique, such as pruning KV cache, sparsity-based fast attention, and Sparse Transformer, have been extensively utilized for efficient Large Language Models (LLMs) deployment. Despite its widespread use, a theoretical understanding of the conditions under which sparse attention performs on par with traditional attention remains elusive. This work aims to $\textbf{bridge this gap by examining the inherent sparsity of standard attention processes}$. Our theoretical framework reveals several brand-new key insights: $\bullet$ Attention is $n^{C}$-sparse, implying that considering only the largest $\Omega(n^{C})$ entries out of all $n$ entries is sufficient for sparse attention to approximate the exact attention matrix with decreasing loss. Here, $n$ represents the input length and $C \in (0, 1)$ is a constant. $\bullet$ Stable $o(\log(n))$-sparse attention, which approximates attention computation with $\log(n)$ or fewer entries, may not be feasible since the error will persist at a minimum of $O(1)$. $\bullet$ An adaptive strategy ($\alpha \cdot n^C, \alpha \in \mathbb{R}$) for the window size of efficient attention methods rather than a fixed one is guaranteed to perform more accurately and efficiently in a task for inference on flexible context lengths.

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Forward citations

Cited by 6 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

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    HierEdit enables efficient 4K image editing via low-resolution proxy localization followed by hierarchical local-window diffusion that reuses unaltered regions as conditioning.

  2. Make Each Token Count: Towards Improving Long-Context Performance with KV Cache Eviction

    cs.LG 2026-05 unverdicted novelty 6.0

    A unified learnable KV eviction policy with cross-layer calibration reduces memory and matches or exceeds full-cache performance on long-context tasks by retaining useful tokens and limiting attention dilution.

  3. Unifying Sparse Attention with Hierarchical Memory for Scalable Long-Context LLM Serving

    cs.LG 2026-04 unverdicted novelty 6.0

    SPIN co-designs sparse attention with hierarchical memory to achieve 1.66-5.66x higher throughput, 7-9x lower TTFT, and up to 58% lower TPOT than vLLM and original sparse implementations.

  4. AdaCluster: Adaptive Query-Key Clustering for Sparse Attention in Video Generation

    cs.CV 2026-04 unverdicted novelty 6.0

    AdaCluster delivers a training-free adaptive query-key clustering framework for sparse attention in video DiTs, yielding 1.67-4.31x inference speedup with negligible quality loss on CogVideoX-2B, HunyuanVideo, and Wan-2.1.

  5. RetroInfer: A Vector Storage Engine for Scalable Long-Context LLM Inference

    cs.LG 2025-05 conditional novelty 6.0

    RetroInfer introduces the wave index and wave buffer to realize sparse KV-cache attention for long-context LLM inference with up to 4.4X throughput gains while matching full-attention accuracy.

  6. RetrievalAttention: Accelerating Long-Context LLM Inference via Vector Retrieval

    cs.LG 2024-09 conditional novelty 6.0

    RetrievalAttention approximates full attention in long-context LLMs by retrieving relevant KV vectors from CPU-based ANNS indexes with an attention-aware algorithm, achieving near-full accuracy while accessing only 1-...