OffQ: Taming Structured Outliers in LLM Quantization by Offsetting
OffQ introduces a novel quantization technique for large language models that addresses activation outliers through an offsetting mechanism, enabling efficient W4A4KV4 low-bit quantization. The method uses top-1 PCA to identify outlier subspaces and concentrates high-magnitude activations into a single channel via rotation, then converts this into a shared offset to reduce standard deviation. This approach maintains uniform-grid quantization while improving accuracy across diverse LLM architectures.