Pivot Gradient Scaling: Reducing Dwell Time to Stabilize Extreme Low-Bit Quantization-aware Training

Vinnam Kim, Junhan Kim, Seungjae Shin, Jung Hyun Lee, Jaeseong You, An Chen, Jungwook Choi


Abstract
Extreme low-bit quantization-aware training (QAT) is often unstable due to synchronized bin transitions, which can trigger catastrophic loss spikes. While prior works rely on scale-side controls to mitigate this fragility, we demonstrate that restricting pivot movement alone is insufficient. Instead, we identify a critical weight-side state governing low-bit QAT stability: pivot-proximal residence, where latent weights persistently linger near quantization pivots. We formalize this duration as dwell time and show that long dwell times accumulate a large, vulnerable population of weights prone to synchronized mass flips. To resolve this vulnerability, we propose Pivot Gradient Scaling (PGS) as a principled modification to the Straight-Through Estimator (STE) that leaves the forward pass intact and selectively amplifies latent-weight gradients within a localized pivot band. Crucially, we provide a mathematical guarantee proving that this sign-preserving amplification increases pivot-proximal mobility and systematically shortens expected dwell time under both SGD and Adam. Exhaustive empirical evaluations across Llama 3.2 and Qwen3 model families under full-training regimes up to 30 billion tokens demonstrate that PGS structurally stabilizes optimization, attenuates transition bursts, and delivers substantial downstream accuracy gains.
Anthology ID:
2026.findings-emnlp.1947
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
41511–41531
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.1947/
DOI:
Bibkey:
Cite (ACL):
Vinnam Kim, Junhan Kim, Seungjae Shin, Jung Hyun Lee, Jaeseong You, An Chen, and Jungwook Choi. 2026. Pivot Gradient Scaling: Reducing Dwell Time to Stabilize Extreme Low-Bit Quantization-aware Training. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 41511–41531, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Pivot Gradient Scaling: Reducing Dwell Time to Stabilize Extreme Low-Bit Quantization-aware Training (Kim et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.1947.pdf