VeriFastScore: Speeding up long-form factuality evaluation

Rishanth Rajendhran, Amir Zadeh, Matthew Sarte, Chuan Li, Mohit Iyyer


Abstract
Metrics like FactScore and VeriScore that evaluate long-form factuality operate by decomposing an input response into atomic claims and then individually verifying each claim. While effective and interpretable, these methods incur numerous LLM calls and can take upwards of 100s to evaluate a single response, limiting their practicality in large-scale evaluation and training scenarios. To address this, we propose VeriFastScore, which leverages synthetic data to fine-tune Llama3.1 8B for simultaneously extracting and verifying all verifiable claims within a given text based on evidence from Google Search. We show that this task cannot be solved via few-shot prompting with closed LLMs due to its complexity: the model receives 4K tokens of evidence on average and needs to concurrently decompose claims, judge their verifiability, and verify them against noisy evidence. However, our fine-tuned VeriFastScore model demonstrates strong correlation with the original VeriScore pipeline at both the example level (r=0.80) and system level (r=0.94) while achieving an overall speedup of 6.6× (9.9 × excluding evidence retrieval) over VeriScore. To facilitate future factuality research, we publicly release our VeriFastScore model and synthetic datasets.
Anthology ID:
2025.findings-emnlp.491
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2025
Month:
November
Year:
2025
Address:
Suzhou, China
Editors:
Christos Christodoulopoulos, Tanmoy Chakraborty, Carolyn Rose, Violet Peng
Venue:
Findings
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
9234–9259
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URL:
https://aclanthology.org/2025.findings-emnlp.491/
DOI:
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Cite (ACL):
Rishanth Rajendhran, Amir Zadeh, Matthew Sarte, Chuan Li, and Mohit Iyyer. 2025. VeriFastScore: Speeding up long-form factuality evaluation. In Findings of the Association for Computational Linguistics: EMNLP 2025, pages 9234–9259, Suzhou, China. Association for Computational Linguistics.
Cite (Informal):
VeriFastScore: Speeding up long-form factuality evaluation (Rajendhran et al., Findings 2025)
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https://aclanthology.org/2025.findings-emnlp.491.pdf
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