SQuAT cut vector-quantization training time 12.8x and scaled lattice quantization to 10B tokens on billion-parameter models
AspireAI community · arXiv (cs.LG) — Qualcomm AI Research
Quantization-aware training with vector quantization should give better rate-distortion trade-offs than plain integer quantization for low-bit LLMs, but how lattice-based VQ-QAT actually behaves at scale was poorly understood. Qualcomm AI Research's SQuAT splits each weight into direction and magnitude: directions are quantized with an E8-derived spherical codebook, gains with independent low-bit scalar quantizers, and separate straight-through estimators for the two produce implicit Riemannian updates on the direction. To make it scale they built a distributed exact nearest-neighbor assignment scheme where workers quantize disjoint weight blocks and exchange only discrete indices, which cut VQ-QAT training time 12.8x and allowed scaling to 10B tokens. Across instruction-tuned LLaMA-3.2-1B/3B, Qwen3-4B and base Qwen3-1.7B, SQuAT beat standard VQ-QAT under identical quantizers and initialization and reached state-of-the-art VQ-QAT accuracy. The limitation is that the reported models top out in the low single-digit billions of parameters.
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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.