AB-Attention Speeds Up Video Diffusion Transformers with Training-Free Accurate Block-Sparse Attention

Bin Xu · hf · 2026-10-30

A multi-institution team proposes AB-Attention, a training-free method that approximates dense 3D attention in video diffusion transformers at high sparsity. Its Intra-Block Clustering Selector estimates block importance cheaply by clustering queries only within each query block without permuting tokens, addressing fidelity loss of prior block-sparse methods under aggressive sparsity, complemented by weighted sampling and fine-grained kernel gathering for both speed and fidelity gains.

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