Google Research

Optimizing Blackbox Metrics with Iterative Example Weighting

  • Gaurush Hiranandani
  • Hari Narasimhan
  • Jatin Mathur
  • Mahdi Milani Fard
  • Sanmi Koyejo
Proceedings of the 38th International Conference on Machine Learning (ICML), 2021

Abstract

We consider learning to optimize a classification metric defined by a black-box function of the confusion matrix. Such black-box learning settings are ubiquitous, for example, when the learner only has query access to the metric of interest, or in noisy-label and domain adaptation applications where the learner must evaluate the metric via performance evaluation using a small validation sample. Our approach is to adaptively learn example weights on the training dataset such that the resulting weighted objective best approximates the metric on the validation sample. We show how to model and estimate the example weights and use them to iteratively post-shift a pre-trained class probability estimator to construct a classifier and analyze the resulting procedure's statistical properties. Experiments on various label noise, domain shift, and fair classification setups confirm that our proposal is better than the individual state-of-the-art baselines for each application.

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