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A Lagrangian Perspective on Latent Variable Generative Models
Proceedings of the 34th Conference on Uncertainty in Artificial Intelligence, PMLR R16:1030-1040, 2018.
Abstract
A large number of objectives have been proposed to train latent variable generative models. We show that many of them are Lagrangian dual functions of the same primal optimization prob- lem. The primal problem optimizes the mutual information between latent and visible variables, subject to the constraints of accurately model- ing the data distribution and performing correct amortized inference. By choosing to maximize or minimize mutual information, and choosing different Lagrange multipliers, we obtain differ- ent objectives including InfoGAN, ALI/BiGAN, ALICE, CycleGAN, beta-VAE, adversarial au- toencoders, AVB, AS-VAE and InfoVAE. Based on this observation, we provide an exhaustive characterization of the statistical and computa- tional trade-offs made by all the training objec- tives in this class of Lagrangian duals. Next, we propose a dual optimization method where we optimize model parameters as well as the La- grange multipliers. This method achieves Pareto optimal solutions in terms of optimizing informa- tion and satisfying the constraints.