SynthLLM: An LLM-based Scalable Synthetic Data Generation Pipeline for Low-Resource Languages

Solmaz Panahi, Vasudevan Nedumpozhimana, John Kelleher


Abstract
Large Language Models (LLMs) have enabled scalable synthetic data generation, yet their effective adaptation to low-resource languages remains underexplored. We introduce an LLM-based generate and annotate paradigm to create synthetic datasets for low-resource NLP classification tasks. The framework employs a smaller model for text generation and a stronger model for automatic annotation. Using Farsi Natural Language Inference (NLI) as a case study, we construct a large-scale synthetic dataset of 100,000 labeled instances. We provide a systematic empirical analysis of annotation quality, label-distribution effects, and training regimes. We compare GPT-4o-mini, Aya-23-35B, and DeBERTa as annotators and examine how annotation variability propagates to downstream performance. Our results show that a warm-up phase with synthetic data consistently outperforms data mixing and reversed ordering. Notably, open-source annotation (Aya-23-35B) achieves comparable downstream performance to the proprietary model (GPT-4o-mini), with significant cost implications for deploying pipelines in low-resource settings. The dataset and code are publicly available at https://huggingface.co/datasets/Solmazp/text2entail.
Anthology ID:
2026.lrec-1.844
Volume:
Proceedings of the Fifteenth Language Resources and Evaluation Conference
Month:
May
Year:
2026
Address:
Palma de Mallorca, Spain
Editors:
Stelios Piperidis, Núria Bel, Henk van den Heuvel, Nancy Ide, Simon Krek, Antonio Toral
Venue:
LREC
SIG:
Publisher:
ELRA Language Resource Association
Note:
Pages:
10776–10791
Language:
External URL:
https://lrec.elra.info/lrec2026-main-844
DOI:
10.63317/36i5afj23ivf
Bibkey:
Cite (ACL):
Solmaz Panahi, Vasudevan Nedumpozhimana, and John Kelleher. 2026. SynthLLM: An LLM-based Scalable Synthetic Data Generation Pipeline for Low-Resource Languages. In Proceedings of the Fifteenth Language Resources and Evaluation Conference, pages 10776–10791, Palma de Mallorca, Spain. ELRA Language Resource Association.
Cite (Informal):
SynthLLM: An LLM-based Scalable Synthetic Data Generation Pipeline for Low-Resource Languages (Panahi et al., LREC 2026)
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