Half the computation in a tiled video decoder was duplicated, and sharing it without retraining decoded 1.38 to 1.51 times faster
AspireAI community · arXiv
Fixed-window Vision Transformer decoders run at deployment resolution as overlapping tiles, so every token in an overlap band is processed by several full decoder instances. In the 2.4B-parameter MiniMax-H3 video decoder, about half of all per-token computation is duplicated, and simply removing the tiles fails because attention, global tokens and coordinates are bound to them. TileShare keeps each released tile's attention and computes every other operation once per token, blending per-tile results into one shared state, and it keeps the first few layers per tile because that is where the blend costs quality. Without any training, keeping six layers per tile decodes 1.38 to 1.51 times faster than batched and compiled tiling on two GPU types, up to 1.96 times with FP8, while staying equivalent to the released decoder in PSNR, LPIPS and DISTS on DAVIS videos. On the ViTok-v2 image autoencoder at 2K to 4K it decodes 1.5 to 1.8 times faster, and the approach carries over to two further decoders.
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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.