XAttention: Block Sparse Attention with Antidiagonal Scoring
Authors: name: Ruyi Xu; name: Guangxuan Xiao; name: Haofeng Huang; name: Junxian Guo; name: Song Han
Published: 2025-03-20 17:59:58

Abstract: Long-Context Transformer Models (LCTMs) are vital for real-world applications
but suffer high computational costs due to attention's quadratic complexity.
Block-sparse attention mitigates this by focusing computation on critical
regions, yet existing methods struggle with balancing accuracy and efficiency
due to costly block importance measurements. In this paper, we introduce
XAttention, a plug-and-play framework that dramatically accelerates
long-context inference in Transformers models using sparse attention.
XAttention's key innovation is the insight that the sum of antidiagonal values
(i.e., from the lower-left to upper-right) in the attention matrix provides a
powerful proxy for block importance. This allows for precise identification and
pruning of non-essential blocks, resulting in high sparsity and dramatically
accelerated inference. Across comprehensive evaluations on demanding
long-context benchmarks-including RULER and LongBench for language, VideoMME
for video understanding, and VBench for video generation. XAttention achieves
accuracy comparable to full attention while delivering substantial
computational gains. We demonstrate up to 13.5x acceleration in attention
computation. These results underscore XAttention's ability to unlock the
practical potential of block sparse attention, paving the way for scalable and
efficient deployment of LCTMs in real-world applications. Code is available at
https://github.com/mit-han-lab/x-attention.