Video diffusion transformers ran up to 2.32x faster when each attention tile got its own precision tier
AspireAI community · arXiv
Attention over tens of thousands of visual tokens dominates video diffusion transformer inference, and existing sparsity or low-precision methods use one precision for all kept tiles even though the resulting error varies widely across them. Triage is a training-free method that assigns each tile one of three approximation tiers, skipping it via block means, skimming it in NVFP4, or refining it with an NVFP4 residual correction, with a lightweight router moving a tile to a more accurate tier only when the predicted error reduction justifies the extra compute. A fused kernel executes all three tiers in one pass on RTX Blackwell FP4 tensor cores. Across Wan2.2, HunyuanVideo and LTX-2.5, Triage accelerated end-to-end generation by up to 2.32x over dense FlashAttention while running faster than every baseline in each of five settings and reaching 0.3 to 3.0 dB higher PSNR than the highest-PSNR baseline. The gains are measured on those three video models and Blackwell-class GPUs.
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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.