Better Approximate Inference for Partial Likelihood Models with a Latent Structure
This addresses inference challenges for researchers in survival analysis and temporal modeling, though it appears incremental as it builds on existing partial likelihood frameworks.
The paper tackles the problem of intractable marginalization in Temporal Point Processes with partial likelihoods and latent structures by proposing a novel MLE approach that minimizes a tight upper bound on the approximation gap, reducing inference complexity from O(|Z|^c) to O(|Z|) and showing improved results in Survival Analysis models.
Temporal Point Processes (TPP) with partial likelihoods involving a latent structure often entail an intractable marginalization, thus making inference hard. We propose a novel approach to Maximum Likelihood Estimation (MLE) involving approximate inference over the latent variables by minimizing a tight upper bound on the approximation gap. Given a discrete latent variable $Z$, the proposed approximation reduces inference complexity from $O(|Z|^c)$ to $O(|Z|)$. We use convex conjugates to determine this upper bound in a closed form and show that its addition to the optimization objective results in improved results for models assuming proportional hazards as in Survival Analysis.