GFlowNet-EM for learning compositional latent variable models

• URL: http://arxiv.org/abs/2302.06576v2
• Date: Sat, 3 Jun 2023 18:02:08 GMT
• Title: GFlowNet-EM for learning compositional latent variable models
• Authors: Edward J. Hu, Nikolay Malkin, Moksh Jain, Katie Everett, Alexandros Graikos, Yoshua Bengio
• Abstract summary: A key tradeoff in modeling the posteriors over latents is between expressivity and tractable optimization. We propose the use of GFlowNets, algorithms for sampling from an unnormalized density. By training GFlowNets to sample from the posterior over latents, we take advantage of their strengths as amortized variational algorithms.
• Score: 115.96660869630227
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Latent variable models (LVMs) with discrete compositional latents are an important but challenging setting due to a combinatorially large number of possible configurations of the latents. A key tradeoff in modeling the posteriors over latents is between expressivity and tractable optimization. For algorithms based on expectation-maximization (EM), the E-step is often intractable without restrictive approximations to the posterior. We propose the use of GFlowNets, algorithms for sampling from an unnormalized density by learning a stochastic policy for sequential construction of samples, for this intractable E-step. By training GFlowNets to sample from the posterior over latents, we take advantage of their strengths as amortized variational inference algorithms for complex distributions over discrete structures. Our approach, GFlowNet-EM, enables the training of expressive LVMs with discrete compositional latents, as shown by experiments on non-context-free grammar induction and on images using discrete variational autoencoders (VAEs) without conditional independence enforced in the encoder.

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