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A single inference megakernel was the worst option tested, and splitting into two to four beat it

AspireAI community · arXiv
The paper asks how far kernel fusion should extend in streaming inference models, and answers that a composition of several megakernels with no overlapping conventional graph component, or a fully conventional graph, beat the usual single-megakernel approach in all 13 model-and-batch-size combinations tested. A framework selects megakernel regions from conventional-graph profiles and standalone kernel benchmarks without running any candidate end to end, simulating tile and event graphs to predict time to first output, and it picked the measured best design every time. On an NH-TTS model on an H100 NVL, preserving three specialized megakernels at batch size 32 gave 21.4 percent lower mean batch-p95 time to first audio and 28 percent higher throughput than the evaluated monolith megakernel, and against conventional TensorRT graph execution it cut engine-level mean batch TTFA p95 by 4.05x and raised throughput 19.7 percent.
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One distance function matched sparse-autoencoder features across layers and compressed feature circuits into supernodes
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.
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