From Pixels to Tokens: Adaptive LLM Decoding and Reliability Analysis with Otsu Thresholding

Eleni Partalidou, Tatiana Passali, Chrysoula Zerva, Grigorios Tsoumakas, Sophia Ananiadou


Abstract
This paper investigates the relationship between generation-time uncertainty and output reliability in probabilistic Large Language Model (LLM) decoding. Specifically, we assess the correlation between several factuality, quality and certainty metrics to infer existing patterns across state-of-the-art decoding strategies, diverse tasks and instruction-tuned models. We also propose a novel, image processing-inspired decoding approach, Otsu Thresholding, that performs adaptive, parameter-free threshold selection directly from the next-token predictive confidence distribution. The proposed Otsu-based variants achieve competitive quality and factuality across tasks and models, while exhibiting concentrated predictive distributions comparable to strong truncation-based baselines. Furthermore, we employ a selective filtering setup to analyze the impact of removing highly uncertain instances on the quality and factuality metrics, ultimately revealing that filtering based on averaged token-level uncertainty metrics can be practically useful for identifying less reliable generations, with filtering frequently improving the quality or factuality of the retained outputs.
Anthology ID:
2026.uncertainlp-main.32
Volume:
The Proceedings of the Third Workshop on Uncertainty-Aware NLP
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Wilker Aziz, Jonathan Berant, Bryan Eikema, Evgenia Ilia, Marie-Catherine de Marneffe, Barbara Plank, Artem Shelmanov, Swabha Swayamdipta, Jörg Tiedemann, Artem Vazhentsev, Raúl Vázquez, Chrysoula Zerva
Venues:
UncertaiNLP | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
518–543
Language:
URL:
https://aclanthology.org/2026.uncertainlp-main.32/
DOI:
Bibkey:
Cite (ACL):
Eleni Partalidou, Tatiana Passali, Chrysoula Zerva, Grigorios Tsoumakas, and Sophia Ananiadou. 2026. From Pixels to Tokens: Adaptive LLM Decoding and Reliability Analysis with Otsu Thresholding. In The Proceedings of the Third Workshop on Uncertainty-Aware NLP, pages 518–543, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
From Pixels to Tokens: Adaptive LLM Decoding and Reliability Analysis with Otsu Thresholding (Partalidou et al., UncertaiNLP 2026)
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PDF:
https://aclanthology.org/2026.uncertainlp-main.32.pdf