Out-of-Distribution Checkpoint Selection Has a Resolution Problem: Auditing Sparse Exact Match with Token Likelihood

Kunhee Ryu, Keeheon Lee


Abstract
Exact match (EM) can make checkpoint selection ambiguous when a small labeled out of distribution (OOD) validation set leaves several checkpoints tied at zero or at the maximum. Without an explicit tie rule, the reported metric does not identify which checkpoint produced the final test score. We study this validation resolution problem in semantic parsing and morphological reinflection. Our protocol reports the reference budget, token likelihood choice under teacher forcing, and latest tied candidate, while using EM for a unique nonzero maximum. Across 600 draws from 30 runs, 8 references leave every early checkpoint at zero in 48% of draws and the maximum tied in 57%. Within tied draws, mean full split regret falls from 0.063 under random selection to 0.050 with token likelihood. The latest tied candidate performs better on average for mostly monotone trajectories, but token likelihood independently orders candidates that hard EM cannot distinguish. These results support reporting both orderings when small labeled OOD validation sets guide checkpoint selection.
Anthology ID:
2026.findings-emnlp.878
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
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SIGDAT
Publisher:
Association for Computational Linguistics
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Pages:
18535–18552
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URL:
https://aclanthology.org/2026.findings-emnlp.878/
DOI:
Bibkey:
Cite (ACL):
Kunhee Ryu and Keeheon Lee. 2026. Out-of-Distribution Checkpoint Selection Has a Resolution Problem: Auditing Sparse Exact Match with Token Likelihood. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 18535–18552, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Out-of-Distribution Checkpoint Selection Has a Resolution Problem: Auditing Sparse Exact Match with Token Likelihood (Ryu & Lee, Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.878.pdf