Fast Inference for Intractable Likelihood Problems using Variational Bayes

Variational Bayes (VB) is a popular estimation method for Bayesian inference. However, most existing VB algorithms are restricted to cases where the likelihood is tractable, which precludes their use in many important situations. Tran et al. (2017) extend the scope of application of VB to cases where the likelihood is intractable but can be estimated unbiasedly, and name the method Variational Bayes with Intractable Likelihood (VBIL). This paper presents a version of VBIL, named Variational Bayes with Intractable Log-Likelihood (VBILL), that is useful for cases as Big Data and Big Panel Data models, where unbiased estimators of the gradient of the log-likelihood are available. We demonstrate that such estimators can be easily obtained in many Big Data applications. The proposed method is exact in the sense that, apart from an extra Monte Carlo error which can be controlled, it is able to produce estimators as if the true likelihood, or full-data likelihood, is used. In particular, we develop a computationally efficient approach, based on data subsampling and the MapReduce programming technique, for analyzing massive datasets which cannot fit into the memory of a single desktop PC. We illustrate the method using several simulated datasets and a big real dataset based on the arrival time status of U. S. airlines.