arXiv Machine Learning

Auditing Conformal Prediction for Language Models Under Inference-Time Model Shift

The paper investigates how changes in inference-time settings—such as quantization and temperature—affect conformal prediction (CP) for language models. It introduces the concept of inference-time model shift, showing that such shifts break split-conformal exchangeability even when the underlying model and data distribution remain unchanged. Experiments on eight language models, four benchmarks, and twelve inference configurations reveal that matched evaluation protocols can significantly overestimate deployment-time coverage, with effects varying across models and datasets.

arXiv Machine Learning
Aug 4

Conformalized Large Language Models under Configuration Shift

arXiv:2608. 01460v1 Announce Type: new Abstract: Conformal prediction (CP) is a distribution-free framework for uncertainty quantification that has recently been adapted to large language models (LLMs), providing prediction sets with finite-sample coverage guarantees under exchangeability.

By Yuqicheng Zhu, Jialin Yu, Lin Li, Gengyuan Zhang, Zhen Yang, Steffen Staab, Puneet Dokania, Philip Torr, Jie Tang, Evgeny Kharlamov
arXiv AI
Oct 15

Scaling Point-in-Time Language Models: Enabling Economic Evaluation of Embeddings

The paper introduces point‑in‑time language models that are trained only on text available up to each calendar date, thereby eliminating lookahead bias that plagues standard large language models. By scaling decoder‑only transformers to 4 billion parameters and training on 1 trillion chronologically filtered tokens from FineWeb, the authors produce monthly checkpoints from 2013 to 2024 that achieve performance close to unconstrained models of similar size on common‑sense reasoning and language understanding tasks. Instruction fine‑tuning with LoRA further enhances downstream usability, and the authors release the full pipeline—including dataset construction, training infrastructure, and evaluation code—for reproducible research.

By Bryan Kelly, Semyon Malamud, Johannes Schwab, Teng Andrea Xu
arXiv AI
Jul 15

Scaling Point-in-Time Language Models

arXiv:2607. 11889v1 Announce Type: cross Abstract: Large language models trained on unrestricted internet corpora inevitably embed information from the future, introducing lookahead bias that compromises the validity of backtests and causal inference in finance and the social sciences.

By Bryan Kelly, Semyon Malamud, Johannes Schwab, Teng Andrea Xu
arXiv Machine Learning
Sep 24

Rolling Conformal Prediction in Sequential Model Training

Rolling Conformal Prediction (rolling‑CP) is a distribution‑free predictive inference method designed for sequential model training. It calibrates each incoming observation against the current predictor and incorporates it into future training, eliminating the need for data splitting. For exchangeable data, rolling‑CP guarantees marginal coverage with a universal factor‑two bound, and for i.i.d. streams it provides high‑probability training‑conditional validity over time, improving to the target level under stability conditions.

By Chen Cheng, Ruiting Liang, Rina Foygel Barber
arXiv AI
Sep 30

OTROPE: Optimal Transport-based Robust Off-policy Evaluation for Large Language Models

The paper introduces OTROPE, a likelihood‑free method for off‑policy evaluation of large language models (LLMs) that uses optimal transport to align labeled samples from a behavior model with unlabeled samples from a target model in a semantic space. OTROPE corrects human‑labeled residuals with proxy predictors, achieving a doubly robust evaluation without requiring behavior‑policy modeling or density‑ratio estimation. The authors provide theoretical guarantees for consistency and convergence, and demonstrate through synthetic and real LLM tasks that OTROPE outperforms existing baselines and can elevate weaker evaluators to match or exceed stronger ones.

By Liner Xiang, Wenbo Zhang, Hengrui Cai