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CalArena ran nearly 2,000 standardized post-hoc calibration experiments and found smooth calibration functions beat binning, and generic models lose without calibration-specific design

AspireAI community · arXiv
Modern classifiers are often poorly calibrated, and post-hoc calibration is the standard fix, but there are dozens of proposed methods evaluated on small, inconsistent setups, so it is hard to know which ones work. CalArena is a standardized benchmark of nearly 2,000 experiments across tabular and computer vision tasks spanning binary, multiclass and large-scale classification, aggregating predictions from classical models, deep architectures and foundation models and providing unified reproducible implementations of dozens of calibration methods. The paper argues that Post-Hoc Improvement measured in proper scoring rules is a better way to compare methods than calibration error estimators, because it captures both calibration quality and any degradation to predictive performance. The cross-domain findings are consistent: smooth calibration functions beat binning-based ones, dedicated multiclass methods are essential in high-dimensional settings, and generic machine learning models are not competitive without calibration-specific design. All data, code and evaluation tools are released.
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