Title
Optimization with Non-Differentiable Constraints with Applications to Fairness, Recall, Churn, and Other Goals
Abstract
We show that many machine learning goals can be expressed as "rate constraints" on a model's predictions. We study the problem of training non-convex models subject to these rate constraints (or other non-convex or non-differentiable constraints). In the non-convex setting, the standard approach of Lagrange multipliers may fail. Furthermore, if the constraints are non-differentiable, then one cannot optimize the Lagrangian with gradient-based methods. To solve these issues, we introduce a new "proxy-Lagrangian" formulation. This leads to an algorithm that, assuming access to an optimization oracle, produces a stochastic classifier by playing a two-player non-zero-sum game solving for what we call a semi-coarse correlated equilibrium, which in turn corresponds to an approximately optimal and feasible solution to the constrained optimization problem. We then give a procedure that shrinks the randomized solution down to a mixture of at most m + 1 deterministic solutions, given m constraints. This culminates in a procedure that can solve non-convex constrained optimization problems with possibly non-differentiable and non-convex constraints, and enjoys theoretical guarantees. We provide extensive experimental results covering a broad range of policy goals, including various fairness metrics, accuracy, coverage, recall, and churn.
Year
Venue
Keywords
2019
JOURNAL OF MACHINE LEARNING RESEARCH
constrained optimization,non-convex,fairness,churn,swap regret,non-zero-sum game
DocType
Volume
Issue
Journal
20
172
ISSN
Citations 
PageRank 
1532-4435
2
0.36
References 
Authors
0
7
Name
Order
Citations
PageRank
Andrew Cotter185178.35
Heinrich Jiang2329.45
Maya R. Gupta359549.62
Serena Wang444.09
Taman Narayan520.36
Seungil You6396.79
Karthik Sridharan7114576.94