Esteban Garces Arias
Also published as: Esteban Garces Arias
2026
Min-k Sampling: Decoupling Truncation from Temperature Scaling via Relative Logit Dynamics
Yuanhao Ding | Meimingwei Li | Esteban Garces Arias | Matthias A{\ss}enmacher | Christian Heumann | Chongsheng Zhang
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Yuanhao Ding | Meimingwei Li | Esteban Garces Arias | Matthias A{\ss}enmacher | Christian Heumann | Chongsheng Zhang
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
The quality of text generated by large language models depends critically on the decoding sampling strategy. While mainstream methods such as Top-k, Top-p, and Min-p achieve a balance between diversity and accuracy through probability-space truncation, they share an inherent limitation: extreme sensitivity to the temperature parameter. Recent logit-space approaches like Top-nđ achieve temperature invariance but rely on global statistics that are susceptible to long-tail noise, failing to capture fine-grained confidence structures among top candidates. We propose Min-k Sampling, a novel dynamic truncation strategy that analyzes the local shape of the sorted logit distribution to identify "semantic cliffs": sharp transitions from high-confidence core tokens to uncertain long-tail tokens. By computing a position-weighted relative decay rate, Min-k dynamically determines truncation boundaries at each generation step. We formally prove that Min-k achieves strict temperature invariance and empirically demonstrate its low sensitivity to hyperparameter choices. Experiments on multiple reasoning benchmarks, creative writing tasks, and human evaluation show that Min-k consistently improves text quality, maintaining robust performance even under extreme temperature settings where probability-based methods collapse. We make our code, models, and analysis tools publicly available.
Digitizing Nepalâs Written Heritage: A Comprehensive HTR Pipeline for Old Nepali Manuscripts
Anjali Sarawgi | Esteban Garces Arias | Christof Zotter
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Anjali Sarawgi | Esteban Garces Arias | Christof Zotter
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
This paper presents the first end-to-end pipeline for Handwritten Text Recognition (HTR) for Old Nepali, a historically significant but low-resource language. We adopt a line-level transcription approach and systematically explore encoder-decoder architectures and data-centric techniques to improve recognition accuracy. Our best model achieves a Character Error Rate (CER) of 4.9%. In addition, we implement and evaluate decoding strategies and analyze token-level confusions to better understand model behavior and error patterns. Although the evaluation dataset is confidential, we release our training code, model configurations, and evaluation scripts to support further research on HTR for low-resource historical scripts.
Self-Reinforcing Controllable Synthesis of Rare Relational Data via Bayesian Calibration
Chongsheng Zhang | Hao Wang | Zelong Yu | Esteban Garces Arias | Julian Rodemann | Zhanshuo Zhang | Qilong Li | Gaojuan Fan | Krikamol Muandet | Christian Heumann
Findings of the Association for Computational Linguistics: ACL 2026
Chongsheng Zhang | Hao Wang | Zelong Yu | Esteban Garces Arias | Julian Rodemann | Zhanshuo Zhang | Qilong Li | Gaojuan Fan | Krikamol Muandet | Christian Heumann
Findings of the Association for Computational Linguistics: ACL 2026
Imbalanced data are commonly present in real-world applications. While data synthesis can effectively mitigate data scarcity for rare classes, and LLMs have revolutionized text generation, the application of LLMs to the synthesis of relational/structured tabular data remains underexplored. Moreover, existing approaches lack an effective feedback mechanism to guide LLMs in continuously optimizing the quality of the generated data throughout the synthesis process. In this work, we propose RDDG, Relational Data generator with Dynamic Guidance, which is a unified in-context learning framework that employs progressive chain-of-thought (CoT) steps to generate tabular data for enhancing downstream imbalanced classification performance. RDDG first uses core set selection to identify representative samples from the original data, then utilizes in-context learning to discover the inherent patterns and correlations among attributes within the core set, and subsequently generates tabular data while preserving the aforementioned constraints. More importantly, it incorporates a self-reinforcing feedback mechanism that provides automatic assessments of the quality of the generated data, enabling continuous quality optimization throughout the generation process. Experimental results on multiple real and synthetic datasets demonstrate that RDDG outperforms existing approaches in both data fidelity and downstream imbalanced classification performance.
2025
The Geometry of Creative Variability: How Credal Sets Expose Calibration Gaps in Language Models
Esteban Garces Arias | Julian Rodemann | Christian Heumann
Proceedings of the 2nd Workshop on Uncertainty-Aware NLP (UncertaiNLP 2025)
Esteban Garces Arias | Julian Rodemann | Christian Heumann
Proceedings of the 2nd Workshop on Uncertainty-Aware NLP (UncertaiNLP 2025)
Understanding uncertainty in large language models remains a fundamental challenge, particularly in creative tasks where multiple valid outputs exist. We present a geometric framework using credal setsâconvex hulls of probability distributionsâto quantify and decompose uncertainty in neural text generation, calibrated against human creative variation. Analyzing 500 creative writing prompts from the dataset with 10 unique human continuations each, we evaluate four language models across five decoding strategies, generating 100,000 stories. Our credal set analysis reveals substantial gaps in capturing human creative variation, with the best model-human calibration reaching only 0.434 (Gemma-2B with temperature 0.7). We decompose total uncertainty into epistemic and aleatoric components, finding that the choice of decoding strategy contributes 39.4% to 72.0% of total epistemic uncertainty. Model scale shows weak correlation with calibration quality and no significant difference exists between base and instruction-tuned models in calibration quality. Our geometric framework provides actionable insights for improving generation systems for human-AI creative alignment. We release our complete experimental framework at https://github.com/EstebanGarces/uncertainHuman.
GUARD: Glocal Uncertainty-Aware Robust Decoding for Effective and Efficient Open-Ended Text Generation
Yuanhao Ding | Esteban Garces Arias | Meimingwei Li | Julian Rodemann | Matthias AĂenmacher | Danlu Chen | Gaojuan Fan | Christian Heumann | Chongsheng Zhang
Findings of the Association for Computational Linguistics: EMNLP 2025
Yuanhao Ding | Esteban Garces Arias | Meimingwei Li | Julian Rodemann | Matthias AĂenmacher | Danlu Chen | Gaojuan Fan | Christian Heumann | Chongsheng Zhang
Findings of the Association for Computational Linguistics: EMNLP 2025
Open-ended text generation faces a critical challenge: balancing coherence with diversity in LLM outputs. While contrastive search-based decoding strategies have emerged to address this trade-off, their practical utility is often limited by hyperparameter dependence and high computational costs. We introduce GUARD, a self-adaptive decoding method that effectively balances these competing objectives through a novel âGlocalâ uncertainty-driven framework. GUARD combines global entropy estimates with local entropy deviations to integrate both long-term and short-term uncertainty signals. We demonstrate that our proposed global entropy formulation effectively mitigates abrupt variations in uncertainty, such as sudden overconfidence or high entropy spikes, and provides theoretical guarantees of unbiasedness and consistency. To reduce computational overhead, we incorporate a simple yet effective token-count-based penalty into GUARD. Experimental results demonstrate that GUARD achieves a good balance between text diversity and coherence, while exhibiting substantial improvements in generation speed. In a more nuanced comparison study across different dimensions of text quality, both human and LLM evaluators validated its remarkable performance. Our code is available at https://github.com/YecanLee/GUARD.
Modern Models, Medieval Texts: A POS Tagging Study of Old Occitan
Matthias Schöffel | Marinus Wiedner | Esteban Garces Arias | Paula Ruppert | Christian Heumann | Matthias AĂenmacher
Proceedings of the 5th International Conference on Natural Language Processing for Digital Humanities
Matthias Schöffel | Marinus Wiedner | Esteban Garces Arias | Paula Ruppert | Christian Heumann | Matthias AĂenmacher
Proceedings of the 5th International Conference on Natural Language Processing for Digital Humanities
Large language models (LLMs) have demonstrated remarkable capabilities in natural language processing, yet their effectiveness in handling historical languages remains largely unexplored. This study examines the performance of open-source LLMs in part-of-speech (POS) tagging for Old Occitan, a historical language characterized by non-standardized orthography and significant diachronic variation. Through comparative analysis of two distinct corporaâhagiographical and medical textsâwe evaluate how current models handle the inherent challenges of processing a low-resource historical language. Our findings demonstrate critical limitations in LLM performance when confronted with extreme orthographic and syntactic variability. We provide detailed error analysis and specific recommendations for improving model performance in historical language processing. This research advances our understanding of LLM capabilities in challenging linguistic contexts while offering practical insights for both computational linguistics and historical language studies.
Statistical Multicriteria Evaluation of LLM-Generated Text
Esteban Garces Arias | Hannah Blocher | Julian Rodemann | Matthias Assenmacher | Christoph Jansen
Proceedings of the 18th International Natural Language Generation Conference
Esteban Garces Arias | Hannah Blocher | Julian Rodemann | Matthias Assenmacher | Christoph Jansen
Proceedings of the 18th International Natural Language Generation Conference
Assessing the quality of LLM-generated text remains a fundamental challenge in natural language processing. Current evaluation approaches often rely on isolated metrics or simplistic aggregations that fail to capture the nuanced trade-offs between coherence, diversity, fluency, and other relevant indicators of text quality. In this work, we adapt a recently proposed framework for statistical inference based on Generalized Stochastic Dominance (GSD) that addresses three critical limitations in existing benchmarking methodologies: the inadequacy of single-metric evaluation, the incompatibility between cardinal automatic metrics and ordinal human judgments, and the lack of inferential statistical guarantees. The GSD-front approach enables simultaneous evaluation across multiple quality dimensions while respecting their different measurement scales, building upon partial orders of decoding strategies, thus avoiding arbitrary weighting of the involved metrics. By applying this framework to evaluate common decoding strategies against human-generated text, we demonstrate its ability to identify statistically significant performance differences while accounting for potential deviations from the i.i.d. assumption of the sampling design.
Towards Better Open-Ended Text Generation: A Multicriteria Evaluation Framework
Esteban Garces Arias | Hannah Blocher | Julian Rodemann | Meimingwei Li | Christian Heumann | Matthias AĂenmacher
Proceedings of the Fourth Workshop on Generation, Evaluation and Metrics (GEMÂČ)
Esteban Garces Arias | Hannah Blocher | Julian Rodemann | Meimingwei Li | Christian Heumann | Matthias AĂenmacher
Proceedings of the Fourth Workshop on Generation, Evaluation and Metrics (GEMÂČ)
Open-ended text generation has become a prominent task in natural language processing due to the rise of powerful (large) language models. However, evaluating the quality of these models and the employed decoding strategies remains challenging due to trade-offs among widely used metrics such as coherence, diversity, and perplexity. This paper addresses the specific problem of multicriteria evaluation for open-ended text generation, proposing novel methods for both relative and absolute rankings of decoding methods. Specifically, we employ benchmarking approaches based on partial orderings and present a new summary metric to balance existing automatic indicators, providing a more holistic evaluation of text generation quality. Our experiments demonstrate that the proposed approaches offer a robust way to compare decoding strategies and serve as valuable tools to guide model selection for open-ended text generation tasks. We suggest future directions for improving evaluation methodologies in text generation and make our code, datasets, and models publicly available.
Decoding Decoded: Understanding Hyperparameter Effects in Open-Ended Text Generation
Esteban Garces Arias | Meimingwei Li | Christian Heumann | Matthias Assenmacher
Proceedings of the 31st International Conference on Computational Linguistics
Esteban Garces Arias | Meimingwei Li | Christian Heumann | Matthias Assenmacher
Proceedings of the 31st International Conference on Computational Linguistics
Decoding strategies for generative large language models (LLMs) are a critical but often underexplored aspect of text generation tasks. Guided by specific hyperparameters, these strategies aim to transform the raw probability distributions produced by language models into coherent, fluent text. In this study, we undertake a large-scale empirical assessment of a range of decoding methods, open-source LLMs, textual domains, and evaluation protocols to determine how hyperparameter choices shape the outputs. Our experiments include both factual (e.g., news) and creative (e.g., fiction) domains, and incorporate a broad suite of automatic evaluation metrics alongside human judgments. Through extensive sensitivity analyses, we distill practical recommendations for selecting and tuning hyperparameters, noting that optimal configurations vary across models and tasks. By synthesizing these insights, this study provides actionable guidance for refining decoding strategies, enabling researchers and practitioners to achieve higher-quality, more reliable, and context-appropriate text generation outcomes.
2024
Adaptive Contrastive Search: Uncertainty-Guided Decoding for Open-Ended Text Generation
Esteban Garces Arias | Julian Rodemann | Meimingwei Li | Christian Heumann | Matthias AĂenmacher
Findings of the Association for Computational Linguistics: EMNLP 2024
Esteban Garces Arias | Julian Rodemann | Meimingwei Li | Christian Heumann | Matthias AĂenmacher
Findings of the Association for Computational Linguistics: EMNLP 2024
Despite the remarkable capabilities of large language models, generating high-quality text remains a challenging task. Numerous decoding strategiesâsuch as beam search, sampling with temperature, topâk sampling, nucleus (topâp) sampling, typical decoding, contrastive decoding, and contrastive searchâhave been proposed to address these challenges by improving coherence, diversity, and resemblance to human-generated text. In this study, we introduce Adaptive Contrastive Search (ACS), a novel decoding strategy that extends contrastive search (CS) by incorporating an adaptive degeneration penalty informed by the modelâs estimated uncertainty at each generation step. ACS aims to enhance creativity and diversity while maintaining coherence to produce high-quality outputs. Extensive experiments across various model architectures, languages, and datasets demonstrate that our approach improves both creativity and coherence, underscoring its effectiveness in text-generation tasks. We release our code, datasets, and models to facilitate further research.
Challenging Error Correction in Recognised Byzantine Greek
John Pavlopoulos | Vasiliki Kougia | Esteban Garces Arias | Paraskevi Platanou | Stepan Shabalin | Konstantina Liagkou | Emmanouil Papadatos | Holger Essler | Jean-Baptiste Camps | Franz Fischer
Proceedings of the 1st Workshop on Machine Learning for Ancient Languages (ML4AL 2024)
John Pavlopoulos | Vasiliki Kougia | Esteban Garces Arias | Paraskevi Platanou | Stepan Shabalin | Konstantina Liagkou | Emmanouil Papadatos | Holger Essler | Jean-Baptiste Camps | Franz Fischer
Proceedings of the 1st Workshop on Machine Learning for Ancient Languages (ML4AL 2024)
Automatic correction of errors in Handwritten Text Recognition (HTR) output poses persistent challenges yet to be fully resolved. In this study, we introduce a shared task aimed at addressing this challenge, which attracted 271 submissions, yielding only a handful of promising approaches. This paper presents the datasets, the most effective methods, and an experimental analysis in error-correcting HTRed manuscripts and papyri in Byzantine Greek, the language that followed Classical and preceded Modern Greek. By using recognised and transcribed data from seven centuries, the two best-performing methods are compared, one based on a neural encoder-decoder architecture and the other based on engineered linguistic rules. We show that the recognition error rate can be reduced by both, up to 2.5 points at the level of characters and up to 15 at the level of words, while also elucidating their respective strengths and weaknesses.
2023
Automatic Transcription of Handwritten Old Occitan Language
Esteban Garces Arias | Vallari Pai | Matthias Schöffel | Christian Heumann | Matthias AĂenmacher
Proceedings of the 2023 Conference on Empirical Methods in Natural Language Processing
Esteban Garces Arias | Vallari Pai | Matthias Schöffel | Christian Heumann | Matthias AĂenmacher
Proceedings of the 2023 Conference on Empirical Methods in Natural Language Processing
While existing neural network-based approaches have shown promising results in Handwritten Text Recognition (HTR) for high-resource languages and standardized/machine-written text, their application to low-resource languages often presents challenges, resulting in reduced effectiveness. In this paper, we propose an innovative HTR approach that leverages the Transformer architecture for recognizing handwritten Old Occitan language. Given the limited availability of data, which comprises only word pairs of graphical variants and lemmas, we develop and rely on elaborate data augmentation techniques for both text and image data. Our model combines a custom-trained Swin image encoder with a BERT text decoder, which we pre-train using a large-scale augmented synthetic data set and fine-tune on the small human-labeled data set. Experimental results reveal that our approach surpasses the performance of current state-of-the-art models for Old Occitan HTR, including open-source Transformer-based models such as a fine-tuned TrOCR and commercial applications like Google Cloud Vision. To nurture further research and development, we make our models, data sets, and code publicly available.
A tailored Handwritten-Text-Recognition System for Medieval Latin
Philipp Koch | Gilary Vera Nuñez | Esteban Garces Arias | Christian Heumann | Matthias Schöffel | Alexander HÀberlin | Matthias Assenmacher
Proceedings of the Ancient Language Processing Workshop
Philipp Koch | Gilary Vera Nuñez | Esteban Garces Arias | Christian Heumann | Matthias Schöffel | Alexander HÀberlin | Matthias Assenmacher
Proceedings of the Ancient Language Processing Workshop
The Bavarian Academy of Sciences and Humanities aims to digitize the Medieval Latin Dictionary. This dictionary entails record cards referring to lemmas in medieval Latin, a low-resource language. A crucial step of the digitization process is the handwritten text recognition (HTR) of the handwritten lemmas on the record cards. In our work, we introduce an end-to-end pipeline, tailored for the medieval Latin dictionary, for locating, extracting, and transcribing the lemmas. We employ two state-of-the-art image segmentation models to prepare the initial data set for the HTR task. Further, we experiment with different transformer-based models and conduct a set of experiments to explore the capabilities of different combinations of vision encoders with a GPT-2 decoder. Additionally, we also apply extensive data augmentation resulting in a highly competitive model. The best-performing setup achieved a character error rate of 0.015, which is even superior to the commercial Google Cloud Vision model, and shows more stable performance.
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Co-authors
- Christian Heumann 10
- Matthias AĂenmacher 9
- Julian Rodemann 6
- Meimingwei Li 5
- Matthias Schöffel 3
- Chongsheng Zhang 3
- Hannah Blocher 2
- Yuanhao Ding 2
- Gaojuan Fan 2
- Jean-Baptiste Camps 1
- Danlu Chen 1
- Holger Essler 1
- Franz Fischer 1
- Alexander HĂ€berlin 1
- Christoph Jansen 1
- Philipp Koch 1
- Vasiliki Kougia 1
- Qilong Li 1
- Konstantina Liagkou 1
- Krikamol Muandet 1
- Gilary Vera Nuñez 1
- Vallari Pai 1
- Emmanouil Papadatos 1
- John Pavlopoulos 1
- Paraskevi Platanou 1
- Paula Ruppert 1
- Anjali Sarawgi 1
- Stepan Shabalin 1
- Hao Wang 1
- Marinus Wiedner 1
- Zelong Yu 1
- Zhanshuo Zhang 1
- Christof Zotter 1