A Variational Estimator for L_p Calibration Errors
Eugène Berta, Sacha Braun, David Holzmüller, Francis Bach, Michael I. Jordan
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Abstract
Calibrationx2014the problem of ensuring that predicted probabilities align with observed class frequenciesx2014is a basic desideratum for reliable prediction with machine learning systems. Calibration error is traditionally assessed via a divergence function, using the expected divergence between predictions and empirical frequencies. Accurately estimating this quantity is challenging, especially in the multiclass setting. Here, we show how to extend a recent variational framework for estimating calibration errors beyond divergences induced induced by proper losses, to cover a broad class of calibration errors induced by L_p divergences. Our method can separate over- and under-confidence and, unlike non-variational approaches, avoids overestimation. We provide extensive experiments and integrate our code in the open-source package probmetrics (https://github.com/dholzmueller/probmetrics) for evaluating calibration errors.