Reliable Evaluation Protocol for Low-Precision Retrieval
Paper · 2026 · Kisu Yang, Yoonna Jang, Hwanseok Jang et al.
Summary
When retrieval models run in reduced numerical formats such as BF16 or FP16, the coarser set of representable values makes many different relevance scores round to the same number. Standard toolkits like MTEB break these artificial ties in an arbitrary order, for example by document ID, so reported metrics can swing with no change in the model. The authors propose a two-part evaluation protocol. High-Precision Scoring (HPS) casts only the logits to FP32 before the final scoring function (softmax, sigmoid or pairwise product). This is roughly a one-line code change and needs no retraining. Tie-aware Retrieval Metric (TRM) gives the closed-form expectation of a metric over all orderings inside tie groups, plus the best-to-worst range and the bias of the naive score. Tests cover five rerankers and embedding models on MIRACLReranking, AskUbuntuDupQuestions and ten MTEB-R datasets. They show that naive BF16 evaluation inflates scores and can even reverse model rankings, while HPS with TRM restores stability close to FP32 at negligible cost.
Key points
- In full BF16, Qwen3-Reranker-0.6B (softmax) on MIRACLReranking showed tie-induced ranges of 25.59%p (nDCG@10) and 38.03%p (MRR@10). HPS cut these to 1.13 and 1.21%p.
- Every BF16 bias was positive, meaning naive metrics overestimated performance by up to +9.08%p. The authors attribute this to relevant items tending to appear earlier in the dataset order.
- Naive BF16 nDCG@10 ranked Qwen3-Reranker above gte-multilingual-reranker-base (75.04 vs 74.48). The expected value reversed this (68.38 vs 74.22), and HPS confirmed the reversal (73.35 vs 74.34).
- With HPS, bi-encoders using pairwise product (Qwen3-Embedding-0.6B, multilingual-e5-large) became fully deterministic, with zero range and zero bias. Sigmoid rerankers such as bge-reranker-v2-m3 saw ranges shrink by about tenfold.
- The code is released at github.com/kisuyang/tie-aware-retrieval-metrics. The study covers the inference stage only and does not address low-precision training.
Fields, topics and concepts
📚 Shelves 5The field of science this work belongs to (OpenAlex fields).Computer Science · 18,614 worksArtificial Intelligence · 17,965 worksArts and Humanities · 17,450 worksLanguage and Linguistics · 17,296 worksInformation Systems · 1,730 works
🧭 Topics 2Research subjects and languages the work is about.Evaluation & benchmarks · 1,341 worksInformation retrieval & search · 552 works
Cite
Cite as Kisu Yang, Yoonna Jang, Hwanseok Jang, Kenneth Choi, Isabelle Augenstein and Heuiseok Lim. 2026. Reliable Evaluation Protocol for Low-Precision Retrieval. Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 2: Short Papers).
@inproceedings{yang2026reliable,
title = {{Reliable Evaluation Protocol for Low-Precision Retrieval}},
author = {Kisu Yang, Yoonna Jang, Hwanseok Jang, Kenneth Choi, Isabelle Augenstein and Heuiseok Lim},
booktitle = {Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 2: Short Papers)},
year = {2026},
doi = {10.18653/v1/2026.acl-short.33},
url = {https://doi.org/10.18653/v1/2026.acl-short.33}
}References
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