REVIEW 4 major objections 4 minor 35 references
BASE-Q: Bias and Asymmetric Scaling Enhanced Rotational Quantization for Large Language Models
T0 review · 4 major / 4 minor · reviewed 2026-08-07 · deepseek-v4-flash
Pith's one-line read BASE-Q claims the residual errors in rotation-based LLM quantization are channel-mean misalignment and clipping energy loss, and fixes both with bias correction and asymmetric scaling.
desk verdict A genuinely useful 4-bit PTQ method with honest but subset-inflated headline numbers; worth refereeing. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The load-bearing identities are the variance decomposition $\sigma^2 = \frac{1}{n}\sum_j \sigma_j^2 + \mathrm{Var}(\mu_j)$, which shows that channel-mean variance survives orthogonal rotation, and the Gaussian tail-energy calculation showing that the best clipping threshold at about $2.2\sigma$ discards approximately 18.4% of activation energy. The mechanism is a learnable bias term fused around each activation quantizer, plus an asymmetric per-quantizer scaling factor that widens the usable range at inference time; both are tuned per block by minimizing the MSE between floating-point and quantized layer outputs while the global rotation matrix stays frozen.
What would settle it
Record the fraction of activation second-moment beyond the chosen clipping threshold per layer after Hadamard rotation across the models studied. If the average is far below 18.4% yet BASE-Q still improves accuracy, the Gaussian-energy rationale fails; if a model shows a large clipping energy loss but asymmetric scaling does not restore accuracy, the mechanism is incomplete.
Extended reading notes
Core claim
The central claim is that after a fixed Hadamard rotation, the dominant remaining quantization errors are not caused by a bad rotation but by two tractable terms: the variance of per-channel means, which can account for up to 85% of layer rounding error in Qwen2.5-3B, and the loss of roughly 18.4% of a layer's input energy when clipping near-Gaussian rotated activations at the best threshold. BASE-Q removes the mean-variance term by injecting a learnable bias before each activation quantizer and subtracting it after the layer, and it compensates the clipping energy loss by scaling activation magnitudes asymmetrically before clipping. With the global rotation fixed rather than learned, these blockwise corrections outperform methods that learn rotations, and they make a 70B model quantizable on a single GPU in about ten hours. This is a claim that the error structure, not the rotation, is the bottleneck.
Load-bearing premise
The predicted benefit of asymmetric scaling depends on rotated activations being approximately bell-shaped, so that the best clipping threshold removes about 18.4% of activation energy; if real distributions are not that shape, the benefit could shrink or disappear.
Editorial extensions
If this is right
- At W4A4KV4, the method closes 50.5%, 42.9%, and 29.2% of the accuracy gap to full precision relative to QuaRot, SpinQuant, and OSTQuant.
- Learned global rotations become unnecessary: standard, random, and learned Hadamard rotations produce nearly identical results inside BASE-Q, eliminating the main memory cost of rotation learning.
- Blockwise optimization means a 70B model can be quantized on one A800 GPU in about 10 hours instead of requiring multi-GPU full-model backpropagation.
- Bias correction and asymmetric scaling are additive with other quantization strategies, since they only wrap each activation quantizer.
Reading between the lines
- A testable extension of the paper's reasoning is that any rotation-based method clipping at a fixed range should lose roughly 18% of activation energy per layer, so per-layer gains should track how much of that loss is recovered.
- The paper's bias-correction result suggests RMSNorm's failure to align channel means is a general quantization liability; adding a learnable shift before normalization might remove the problem at its source rather than after rotation.
- If the near-Gaussian assumption holds across architectures, asymmetric scaling should transfer to other orthogonal transforms and to KV-cache quantization, not only the projections tested here.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper proposes BASE-Q, a W4A4KV4 post-training quantization method for LLMs that builds on fixed Hadamard rotations. It identifies two residual error sources after rotation—inter-channel mean variance contributing to rounding error (Eq. 6) and tail energy lost to clipping under near-Gaussian rotated activations (Eq. 8)—and addresses them with learnable blockwise bias correction and asymmetric scaling, together with a learned intra-block value rotation. The global residual rotation is fixed, enabling blockwise optimization without full-model backpropagation. Experiments on 12 LLMs report perplexity and zero-shot accuracy, with headline claims that BASE-Q closes 50.5%, 42.9%, and 29.2% of the accuracy gap to full precision relative to QuaRot, SpinQuant, and OSTQuant, respectively.
Significance. If the empirical results hold, BASE-Q is a practically relevant contribution: it appears to match or exceed learned-rotation methods at a fraction of the optimization cost, and its error decomposition is a useful way to think about why rotation-based PTQ plateaus. The variance decomposition in Eq. (6) and the 18.4% Gaussian tail-energy calculation in Eq. (8) are correct as mathematical statements. The paper also includes an ablation separating bias correction, asymmetric scaling, and rotation choice, and reports memory and latency comparisons. However, the theoretical connection from these calculations to actual quantization error is heuristic, and the headline aggregate is more favorable than a per-model reading of Table 1 suggests. These issues are addressable, but they affect the strength of the central claims.
major comments (4)
- [§5.1, Table 1] The abstract and introduction present the 50.5/42.9/29.2% gap-closure numbers without stating that they are computed only over the eight models for which OSTQuant does not OOM. Using the values in Table 1, if Qwen2.5-3B is removed from that eight-model subset, the aggregate gap closures drop to roughly 40%, 30%, and 16% relative to QuaRot, SpinQuant, and OSTQuant. The paper does not report per-model gap-closure percentages or any measure of dispersion, so the headline does not convey that the gain is substantially concentrated in models where the baselines collapse. Since the central quantitative claim is stated as a single set of percentages in the abstract, this presentation overstates the consistency of the improvement and should be revised with the common-model subset disclosed, per-model numbers, and a robustness check without the extreme Qwen2.5-3B case.
- [§3.4, Eq. (12)] The derivation of the optimal scaling factor appears to contain a dimensional error. With weights scaled by s and activations by 1/s, uniform-rounding errors in the original units have variances proportional to 1/s² for weights and s² for activations (or the reverse, depending on convention). Minimizing E[|w|²]Var(ε_a)+E[|a|²]Var(ε_w) then yields s² proportional to sqrt(E[|w|²]/E[|a|²]), not s² = E[|w|²]/E[|a|²] as stated. If the authors intend a different convention (e.g., error amplitude rather than variance, or scaling applied to quantization steps), it should be stated explicitly. As written, Eq. (12) does not follow from the AM-GM argument in the text.
- [§3.3, Eq. (8)] The 18.4% clip-energy loss is derived for a zero-mean Gaussian, and the paper motivates asymmetric scaling by the claim that rotated activations are 'more Gaussian-like.' The paper provides one illustrative example (Figure 3) and qualitative histograms in Appendix B, but no systematic test of Gaussianity across layers and models, and no sensitivity analysis showing how the predicted benefit degrades for heavier-tailed or skewed distributions. Because the theoretical case for asymmetric scaling rests on this approximation, the claim in Section 3.3 that clipping 'fundamentally breaks' rotational equivalence should be supported by distributional diagnostics or a robustness analysis. The empirical ablation (Table 2) does show consistent gains from asymmetric scaling, so this is a theoretical-support issue rather than a refutation of the method.
- [§3.2, Eqs. (5)–(6)] The decomposition in Eq. (6) is mathematically correct, but the claim that Var(μ_j) causes up to 85% of rounding error depends on the assumption that the quantization step is proportional to the pooled activation standard deviation σ. The actual deployment uses per-token asymmetric dynamic quantization for activations (Section 5), for which the relevant range is per-token min/max; the mean-variance term does not translate to rounding error in the same way for a per-channel zero-point quantizer. The paper should either derive the 85% figure under the quantizer actually used or state clearly that it is a heuristic estimate. This matters because the 85% number is the principal justification for the bias-correction component.
minor comments (4)
- [Table 1 vs. Appendix A] The LLaMA-3.2-1B row reports BASE-Q as 50.61 accuracy / 12.66 perplexity in Table 1 but 49.79 / 12.63 in Table 5 of Appendix A; the headline aggregate appears to rely on one of these values. These numbers should be reconciled.
- [Table 2] The column header 'Unpaired Scale Scale' and the row notation 'Rres Rqk Rdown Rv' are difficult to parse; please clarify which rotation is learned in each row and what 'unpaired scale' denotes.
- [Abstract and §1] The abstract states 'The code will be released soon' while the full text and the GitHub link in Section 1 imply the code is already available; please harmonize the availability statement.
- [Throughout] There are minor typos and notation inconsistencies, including 'Bias Corect.' in Table 2, 'Quarot' in Table 5, and inconsistent use of R_res vs. Rres; a careful proofread would improve readability.
Circularity Check
No circular derivation: BASE-Q's bias correction and asymmetric scaling are fitted blockwise but evaluated on held-out tasks; the theoretical error analysis is independent of the method's outputs.
full rationale
The derivation chain is self-contained. The Section 3 error analysis quantifies rounding error via Eqs. (5)-(6) and clipping energy loss via Eqs. (7)-(8) from the Gaussian approximation, and these quantities are measured from activations, not defined by BASE-Q's success. Bias correction (Eq. 14) and asymmetric scaling (Eq. 15) are introduced to target those identified terms, and the blockwise objective (Eq. 16) fits bias, scale, and clipping parameters to calibration MSE; this is ordinary PTQ calibration rather than a prediction that reduces to its own fit. The headline gap-closure percentages are computed from downstream Wikitext-2 and zero-shot accuracies after calibration, and the paper explicitly states that the baseline averages are computed over the eight models supported by all methods ('averaged over eight supported models'), so the comparison set is disclosed rather than hidden. The two self-citations ([8], [9]) appear only in the general quantization-related-work sentence and are not load-bearing for any claim; no uniqueness theorem or ansatz is imported from the authors' prior work. The Gaussianity assumption behind Eq. (8) is a stated modeling assumption with an empirical illustration, not a circular step. Therefore no step reduces by construction to its input.
Assumptions & free parameters
free parameters (5)
- Blockwise rotation Rv =
learned per-block orthogonal matrix
- Bias correction terms b_c (qkv, o, up, down) =
learned per-block bias vectors
- Symmetric scaling s_j =
learned per-layer scaling factors
- Asymmetric scaling s_a =
learned per-quantizer scaling factors
- Clipping thresholds alpha_i =
learned per-activation quantizer clipping factors
assumptions (6)
- domain assumption Post-rotation activations are approximately Gaussian (Section 3.3, Eq. 7-8).
- standard math Quantization error decomposes into independent rounding and clipping components (Section 3.1, Eq. 4).
- domain assumption The quantization step size is proportional to the standard deviation of activations (Eq. 5).
- domain assumption A single global rotation cannot simultaneously align channel means and suppress outliers (Section 3.2).
- standard math AM-GM optimal scaling formula s^2 = E[|w|^2]/E[|a|^2] (Eq. 12).
- domain assumption MSE-optimal clipping threshold is approximately 2.2 sigma for 4-bit Gaussian activations (Eq. 7).
Cite this review
Pith. "Pith review of BASE-Q: Bias and Asymmetric Scaling Enhanced Rotational Quantization for Large Language Models." pith.science (2026). https://pith.science/paper/3K4A7CCG
@misc{pith2026250615689,
author = {Pith},
title = {Pith review of: BASE-Q: Bias and Asymmetric Scaling Enhanced Rotational Quantization for Large Language Models},
year = {2026},
howpublished = {\url{https://pith.science/paper/3K4A7CCG}},
note = {Machine review of arXiv:2506.15689}
}
read the original abstract
Rotations have become essential to state-of-the-art quantization pipelines for large language models (LLMs) by effectively smoothing outliers in weights and activations. However, further optimizing the rotation parameters offers only limited performance gains and introduces significant training overhead: due to rotation parameter sharing, full-model must be loaded simultaneously to enable backpropagation, resulting in substantial memory consumption and limited practical utility. In this work, we identify two fundamental limitations of current rotational quantization methods: (i) rotation fails to align channel means, resulting in wider quantization bounds and increased rounding errors; and (ii) rotation makes the activation distribution more Gaussian-like, increasing energy loss caused by clipping errors. To address these issues, we introduce \textbf{BASE-Q}, a simple yet powerful approach that combines bias correction and asymmetric scaling to effectively reduce rounding and clipping errors. Furthermore, BASE-Q enables blockwise optimization, eliminating the need for memory-intensive full-model backpropagation. Extensive experiments on various LLMs and benchmarks demonstrate the effectiveness of BASE-Q, narrowing the accuracy gap to full-precision models by 50.5\%, 42.9\%, and 29.2\% compared to QuaRot, SpinQuant, and OSTQuant, respectively. The code will be released soon.
Figures
Figures from the paper (23 more)
Reference graph
Works this paper leans on
-
[1]
Llama: Open and efficient foundation language models
Hugo Touvron, Thibaut Lavril, Gautier Izacard, Xavier Martinet, Marie-Anne Lachaux, Timo- thée Lacroix, Baptiste Rozière, Naman Goyal, Eric Hambro, Faisal Azhar, et al. Llama: Open and efficient foundation language models. arXiv preprint arXiv:2302.13971, 2023
arXiv 2023
-
[2]
Jinze Bai and et al. Qwen technical report. ArXiv, abs/2309.16609, 2023
arXiv 2023
-
[3]
Abhimanyu Dubey and et al. The llama 3 herd of models. ArXiv, abs/2407.21783, 2024
arXiv 2024
-
[4]
Llama 2: Open foundation and fine-tuned chat models
Hugo Touvron and et al. Llama 2: Open foundation and fine-tuned chat models. ArXiv, abs/2307.09288, 2023
arXiv 2023
-
[5]
DeepSeek-AI. Deepseek-v3 technical report. ArXiv, abs/2412.19437, 2024
arXiv 2024
-
[6]
Up or down? adaptive rounding for post-training quantization
Markus Nagel, Rana Ali Amjad, Mart van Baalen, Christos Louizos, and Tijmen Blankevoort. Up or down? adaptive rounding for post-training quantization. ArXiv, abs/2004.10568, 2020
arXiv 2004
-
[7]
Brecq: Pushing the limit of post-training quantization by block reconstruction
Yuhang Li, Ruihao Gong, Xu Tan, Yang Yang, Peng Hu, Qi Zhang, Fengwei Yu, Wei Wang, and Shi Gu. Brecq: Pushing the limit of post-training quantization by block reconstruction. ArXiv, abs/2102.05426, 2021. 10
arXiv 2021
-
[8]
Noisyquant: Noisy bias-enhanced post-training activation quantization for vision transformers
Yijiang Liu, Huanrui Yang, Zhen Dong, Kurt Keutzer, Li Du, and Shanghang Zhang. Noisyquant: Noisy bias-enhanced post-training activation quantization for vision transformers. 2023 IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR), pages 20321– 20330, 2022
work page 2023
Show all 35 references
-
[9]
Fbquant: Feedback quantization for large language models
Yijiang Liu, Hengyu Fang, Liulu He, Rongyu Zhang, Yichuan Bai, Yuan Du, and Li Du. Fbquant: Feedback quantization for large language models. ArXiv, abs/2501.16385, 2025
2025 arXiv
-
[10]
Outlier suppression+: Accurate quantization of large language models by equivalent and optimal shifting and scaling
Xiuying Wei, Yunchen Zhang, Yuhang Li, Xiangguo Zhang, Ruihao Gong, Jinyang Guo, and Xianglong Liu. Outlier suppression+: Accurate quantization of large language models by equivalent and optimal shifting and scaling. ArXiv, abs/2304.09145, 2023
2023 arXiv
-
[11]
Llm.int8(): 8-bit matrix multiplication for transformers at scale
Tim Dettmers, Mike Lewis, Younes Belkada, and Luke Zettlemoyer. Llm.int8(): 8-bit matrix multiplication for transformers at scale. ArXiv, abs/2208.07339, 2022
2022 arXiv
-
[12]
Smoothquant: Accu- rate and efficient post-training quantization for large language models
Guangxuan Xiao, Ji Lin, Mickael Seznec, Julien Demouth, and Song Han. Smoothquant: Accu- rate and efficient post-training quantization for large language models. ArXiv, abs/2211.10438, 2022
2022 arXiv
-
[13]
Croci, Bo Li, Martin Jaggi, Dan Alistarh, Torsten Hoefler, and James Hensman
Saleh Ashkboos, Amirkeivan Mohtashami, Maximilian L. Croci, Bo Li, Martin Jaggi, Dan Alistarh, Torsten Hoefler, and James Hensman. Quarot: Outlier-free 4-bit inference in rotated llms. ArXiv, abs/2404.00456, 2024
2024 arXiv
-
[14]
Spinquant: Llm quantization with learned rotations
Zechun Liu, Changsheng Zhao, Igor Fedorov, Bilge Soran, Dhruv Choudhary, Raghuraman Krishnamoorthi, Vikas Chandra, Yuandong Tian, and Tijmen Blankevoort. Spinquant: Llm quantization with learned rotations. ArXiv, abs/2405.16406, 2024
2024 arXiv
-
[15]
Ostquant: Refining large language model quantization with orthogonal and scaling transformations for better distribution fitting
Xing Hu, Yuan Cheng, Dawei Yang, Zukang Xu, Zhihang Yuan, Jiangyong Yu, Chen Xu, Zhe Jiang, and Sifan Zhou. Ostquant: Refining large language model quantization with orthogonal and scaling transformations for better distribution fitting. ArXiv, abs/2501.13987, 2025
2025 arXiv
-
[16]
Awq: Activation-aware weight quantization for on-device llm compression and acceleration
Ji Lin, Jiaming Tang, Haotian Tang, Shang Yang, Wei-Ming Chen, Wei-Chen Wang, Guangxuan Xiao, Xingyu Dang, Chuang Gan, and Song Han. Awq: Activation-aware weight quantization for on-device llm compression and acceleration. Proceedings of Machine Learning and Systems, 6:87–100, 2024
2024
-
[17]
Omniquant: Omnidirectionally calibrated quantization for large language models
Wenqi Shao, Mengzhao Chen, Zhaoyang Zhang, Peng Xu, Lirui Zhao, Zhiqiang Li, Kaipeng Zhang, Peng Gao, Yu Jiao Qiao, and Ping Luo. Omniquant: Omnidirectionally calibrated quantization for large language models. ArXiv, abs/2308.13137, 2023
2023 arXiv
-
[18]
Affinequant: Affine transformation quantization for large language models
Yuexiao Ma, Huixia Li, Xiawu Zheng, Feng Ling, Xuefeng Xiao, Rui Wang, Shilei Wen, Fei Chao, and Rongrong Ji. Affinequant: Affine transformation quantization for large language models. ArXiv, abs/2403.12544, 2024
2024 arXiv
-
[19]
Quip: 2-bit quantiza- tion of large language models with guarantees
Jerry Chee, Yaohui Cai, V olodymyr Kuleshov, and Christopher M De Sa. Quip: 2-bit quantiza- tion of large language models with guarantees. Advances in Neural Information Processing Systems, 36:4396–4429, 2023
2023
-
[20]
Quip#: Even better llm quantization with hadamard incoherence and lattice codebooks
Albert Tseng, Jerry Chee, Qingyao Sun, V olodymyr Kuleshov, and Christopher De Sa. Quip#: Even better llm quantization with hadamard incoherence and lattice codebooks. arXiv preprint arXiv:2402.04396, 2024
2024 arXiv
-
[21]
Duquant: Distributing outliers via dual transformation makes stronger quantized llms
Haokun Lin, Haobo Xu, Yichen Wu, Jingzhi Cui, Yingtao Zhang, Linzhan Mou, Linqi Song, Zhenan Sun, and Ying Wei. Duquant: Distributing outliers via dual transformation makes stronger quantized llms. Advances in Neural Information Processing Systems, 37:87766–87800, 2024
2024
-
[22]
Flatquant: Flatness matters for llm quantization
Yuxuan Sun, Ruikang Liu, Haoli Bai, Han Bao, Kang Zhao, Yuening Li, Jiaxin Hu, Xianzhi Yu, Lu Hou, Chun Yuan, et al. Flatquant: Flatness matters for llm quantization. arXiv preprint arXiv:2410.09426, 2024
2024 arXiv
-
[23]
An Yang, Baosong Yang, Beichen Zhang, Binyuan Hui, Bo Zheng, Bowen Yu, Chengyuan Li, Dayiheng Liu, Fei Huang, Haoran Wei, et al. Qwen2. 5 technical report. arXiv preprint arXiv:2412.15115, 2024. 11
2024 arXiv
-
[24]
Pointer sentinel mixture models
Stephen Merity, Caiming Xiong, James Bradbury, and Richard Socher. Pointer sentinel mixture models. arXiv preprint arXiv:1609.07843, 2016
2016 arXiv
-
[25]
Think you have solved question answering? try arc, the ai2 reasoning challenge
Peter Clark, Isaac Cowhey, Oren Etzioni, Tushar Khot, Ashish Sabharwal, Carissa Schoenick, and Oyvind Tafjord. Think you have solved question answering? try arc, the ai2 reasoning challenge. arXiv preprint arXiv:1803.05457, 2018
2018 arXiv
-
[26]
Boolq: Exploring the surprising difficulty of natural yes/no questions
Christopher Clark, Kenton Lee, Ming-Wei Chang, Tom Kwiatkowski, Michael Collins, and Kristina Toutanova. Boolq: Exploring the surprising difficulty of natural yes/no questions. arXiv preprint arXiv:1905.10044, 2019
1905 arXiv
-
[27]
Hellaswag: Can a machine really finish your sentence? arXiv preprint arXiv:1905.07830, 2019
Rowan Zellers, Ari Holtzman, Yonatan Bisk, Ali Farhadi, and Yejin Choi. Hellaswag: Can a machine really finish your sentence? arXiv preprint arXiv:1905.07830, 2019
1905 arXiv
-
[28]
Language models are unsupervised multitask learners
Alec Radford, Jeffrey Wu, Rewon Child, David Luan, Dario Amodei, Ilya Sutskever, et al. Language models are unsupervised multitask learners. OpenAI blog, 1(8):9, 2019
2019
-
[29]
Can a suit of armor conduct electricity? a new dataset for open book question answering
Todor Mihaylov, Peter Clark, Tushar Khot, and Ashish Sabharwal. Can a suit of armor conduct electricity? a new dataset for open book question answering. arXiv preprint arXiv:1809.02789, 2018
2018 arXiv
-
[30]
Piqa: Reasoning about phys- ical commonsense in natural language
Yonatan Bisk, Rowan Zellers, Jianfeng Gao, Yejin Choi, et al. Piqa: Reasoning about phys- ical commonsense in natural language. In Proceedings of the AAAI conference on artificial intelligence, volume 34, pages 7432–7439, 2020
2020
-
[31]
Socialiqa: Com- monsense reasoning about social interactions
Maarten Sap, Hannah Rashkin, Derek Chen, Ronan LeBras, and Yejin Choi. Socialiqa: Com- monsense reasoning about social interactions. arXiv preprint arXiv:1904.09728, 2019
1904 arXiv
-
[32]
Winogrande: An adversarial winograd schema challenge at scale
Keisuke Sakaguchi, Ronan Le Bras, Chandra Bhagavatula, and Yejin Choi. Winogrande: An adversarial winograd schema challenge at scale. Communications of the ACM, 64(9):99–106, 2021
2021
-
[33]
The language model evaluation harness, 07 2024
Leo Gao, Jonathan Tow, Baber Abbasi, Stella Biderman, Sid Black, Anthony DiPofi, Charles Foster, Laurence Golding, Jeffrey Hsu, Alain Le Noac’h, Haonan Li, Kyle McDonell, Niklas Muennighoff, Chris Ociepa, Jason Phang, Laria Reynolds, Hailey Schoelkopf, Aviya Skowron, Lintang S...
2024
-
[34]
Gptq: Accurate post-training quantization for generative pre-trained transformers
Elias Frantar, Saleh Ashkboos, Torsten Hoefler, and Dan Alistarh. Gptq: Accurate post-training quantization for generative pre-trained transformers. ArXiv, abs/2210.17323, 2022
2022 arXiv
-
[35]
fast-hadamard-transform, 2023
Tri Dao. fast-hadamard-transform, 2023. https://github.com/Dao-AILab/ fast-hadamard-transform. 12 A Full quantization results We present comprehensive quantization results in this section, including perplexity on WikiText2 and zero-shot accuracy on nine evaluation datasets. Al...
2023
Reviewed August 7, 2026 · model on record in the stance chip above.
Discussion (0). Sign in to comment.