OJBKQ: Objective-Joint Babai-Klein Quantization

Fuente: arXiv
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Main Authors: Wang, Xinyu, Zhao, Ziyu, Lu, Peng, Gu, Yu, Chang, Xiao-Wen
Format: Preprint
Published: 2026
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author Wang, Xinyu
Zhao, Ziyu
Lu, Peng
Gu, Yu
Chang, Xiao-Wen
author_facet Wang, Xinyu
Zhao, Ziyu
Lu, Peng
Gu, Yu
Chang, Xiao-Wen
contents Post-training quantization (PTQ) is widely used to compress large language models without retraining. However, many existing weight-only methods rely on heuristic objectives and greedy rounding, thus leading to noticeable degradation under low-bit quantization. In this work, we introduce OJBKQ (Objective-Joint Babai-Klein Quantization with K-Best Sampling), a layer-wise PTQ method that formulates weight quantization as a joint optimization problem over activations and weights. This formulation results in a multiple-right-hand-side box-constrained integer least squares (BILS) problem in each layer, which is NP-hard. For each column of the weight matrix, we apply an extended Babai nearest-plane algorithm and an extended version of Klein's randomized Babai algorithm to find the minimum-residual Babai-Klein point, a sub-optimal solution to the BILS problem. Experimental results on large language models show that OJBKQ achieves lower perplexity at 3-4 bits compared to existing PTQ approaches, while maintaining comparable computational cost.
format Preprint
id arxiv_https___arxiv_org_abs_2602_08376
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle OJBKQ: Objective-Joint Babai-Klein Quantization
Wang, Xinyu
Zhao, Ziyu
Lu, Peng
Gu, Yu
Chang, Xiao-Wen
Machine Learning
Post-training quantization (PTQ) is widely used to compress large language models without retraining. However, many existing weight-only methods rely on heuristic objectives and greedy rounding, thus leading to noticeable degradation under low-bit quantization. In this work, we introduce OJBKQ (Objective-Joint Babai-Klein Quantization with K-Best Sampling), a layer-wise PTQ method that formulates weight quantization as a joint optimization problem over activations and weights. This formulation results in a multiple-right-hand-side box-constrained integer least squares (BILS) problem in each layer, which is NP-hard. For each column of the weight matrix, we apply an extended Babai nearest-plane algorithm and an extended version of Klein's randomized Babai algorithm to find the minimum-residual Babai-Klein point, a sub-optimal solution to the BILS problem. Experimental results on large language models show that OJBKQ achieves lower perplexity at 3-4 bits compared to existing PTQ approaches, while maintaining comparable computational cost.
title OJBKQ: Objective-Joint Babai-Klein Quantization
topic Machine Learning
url https://arxiv.org/abs/2602.08376