arXiv Machine Learning

PrismQuant: Optimal Null-Space Rotations for Grouped Quantizers

PrismQuant introduces a rotation framework that aligns the leading activation eigenspace with the constant group subspace of asymmetric grouped INT4 quantizers, optimizing the alignment via Ky Fan trace maximization and providing a closed‑form solution. The method employs compact Householder transformations for efficient, gradient‑free construction and applies a predictive range law to relate unaligned activation energy and group size to quantization variation. Experiments on large language models up to 70B parameters show PrismQuant achieving state‑of‑the‑art perplexity and accuracy, while delivering significant speedups and memory reductions in deployment scenarios.

arXiv AI
Sep 30

ThinQuant: Scalable Rotation Learning for Weight and Activation Quantization of LLMs

ThinQuant introduces efficient rotation learning for low‑bit weight and activation quantization of large language models by reducing calibration data through a geometric selection of activations and solving a lower‑dimensional optimization problem via an ADMM algorithm. The method achieves comparable or better quantization performance with dramatically fewer calibration points, completing rotation calibration for Llama‑3‑70B in under 12 minutes and for Llama‑3.1‑405B in just over 2 hours on a single GPU. ThinQuant outperforms existing gradient‑free approaches such as DartQuant and gradient‑based SpinQuant in both speed and perplexity metrics on WikiText‑2.

By Mehdi Makni, Ryan Lucas, Rahul Mazumder
arXiv AI
Sep 4

HARP: Hadamard-Preconditioned Adaptive Rotation Processor for Extreme LLM Quantization

HARP (Hadamard‑Preconditioned Adaptive Rotation Processor) is a learnable, structured two‑sided orthogonal processor that replaces fixed randomized Hadamard transforms in post‑training quantization of large language models. By representing rotations as sparse butterfly‑like block‑orthogonal stages and supporting mixed‑radix schedules, HARP adapts the quantization basis to each layer and calibration distribution while maintaining full‑precision equivalence. Across 2–4‑bit settings on Llama models from 1B to 70B, HARP consistently improves perplexity, delivers the strongest zero‑shot gains at 2 bits, and preserves deployment efficiency—achieving 128 tokens per second on Llama 2 7B at 2 bits, roughly 90% of RHT throughput and over twice the speed of FP16.

By Artur Zagitov, Gleb Molodtsov, Aleksandr Beznosikov
arXiv Machine Learning
Oct 3

ConQuR: Corner Aligned Activation Quantization via Optimized Rotations for LLMs

ConQuR introduces a lightweight post‑training rotation calibration for large language model activation quantization. By learning orthogonal rotations that align normalized activations with the corners of an inscribed hypercube, the method distributes activation energy evenly and can be updated online without storing activations. Experiments on Llama‑2 and Llama‑3 models (3B–70B) show competitive or improved perplexity and reasoning performance while avoiding costly training or large offline storage.

By Chayne Thrash, Ali Abbasi, Soheil Kolouri