Latent Dirichlet Allocation

Blei et al., 2003, Latent Dirichlet Allocation (Journal of Machine Learning Research)

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5.1 Inference

  1. Why is exact posterior inference in LDA intractable?
    The posterior \(p(\theta, \mathbf{z} \mid \mathbf{w}, \alpha, \beta)\) needs the normalizer \(p(\mathbf{w} \mid \alpha, \beta)\), which couples \(\theta\) and \(\beta\) in the sum over latent topics inside the integral. Approximations include Laplace, variational methods and MCMC.

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