PRC: An Efficient and Unified Framework for Evaluating Robustness and Controllability of Large Language Models on Few-shot Prompt Variations

Chunpeng Ma


Abstract
Understanding the impact of prompt variations on large language model (LLM) outputs is critical. Despite extensive research, two challenges persist: conflated terminology stemming from loosely defined concepts, and inefficient evaluations reliant on output generation. To address these, we first formalize prompt categorization to clearly define prompt robustness and controllability. We then introduce the prompt vector (PV), a compact internal representation that reformulates these properties at the representation level. Building on PV, we propose PRC, an efficient and unified framework to systematically evaluate LLMs under few-shot prompt variations without requiring costly autoregressive decoding. Experiments across diverse instruction-tuned LLMs demonstrate that PRC tightly correlates with traditional output-based metrics while substantially reducing computational overhead. Overall, PRC offers a principled and highly efficient tool for diagnosing LLM behavior.
Anthology ID:
2026.aacl-long.10
Volume:
Proceedings of the 15th International Joint Conference on Natural Language Processing and the 5th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics (Volume 1: Long Papers)
Month:
November
Year:
2026
Address:
Hengqin, China
Editors:
Yue Zhang, Ruifeng Xu, Ayu Purwarianti, Tong Rong, Jun Suzuki
Venues:
AACL | IJCNLP
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
204–222
Language:
URL:
https://aclanthology.org/2026.aacl-long.10/
DOI:
Bibkey:
Cite (ACL):
Chunpeng Ma. 2026. PRC: An Efficient and Unified Framework for Evaluating Robustness and Controllability of Large Language Models on Few-shot Prompt Variations. In Proceedings of the 15th International Joint Conference on Natural Language Processing and the 5th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics (Volume 1: Long Papers), pages 204–222, Hengqin, China. Association for Computational Linguistics.
Cite (Informal):
PRC: An Efficient and Unified Framework for Evaluating Robustness and Controllability of Large Language Models on Few-shot Prompt Variations (Ma, AACL-IJCNLP 2026)
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PDF:
https://aclanthology.org/2026.aacl-long.10.pdf