Ant Group and the vLLM community open-sourced Humming, a kernel library for quantized inference across dense and MoE models
AspireAI community · vLLM / Ant Group
Quantized inference is increasingly the deployment constraint, especially for mixture-of-experts models where each token activates few experts but all weights must still be resident. Humming is a new open-source kernel library from Ant Group and the vLLM community, built on a unified quantization representation that covers combinations of weight and activation formats for dense and MoE workloads - WnA16, W8A8, W4A8 and W4A4 across integer and floating-point types, bit widths and scaling schemes - with per-workload JIT compilation and shared CUDA components across formats and architectures. It supports NVIDIA architectures from Turing onward plus CUDA-compatible devices such as T-Head's Zhenwu 810E, and the authors report it significantly outperforming existing implementations including vLLM's own Marlin kernels, with integration into vLLM. The published speedups are kernel microbenchmarks run by the community rather than end-to-end serving benchmarks.
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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.