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 Uncertainty







Model-based RL with Optimistic Posterior Sampling: Structural Conditions and Sample Complexity Alekh Agarwal Google Research Tong Zhang Google Research and HKUST

Neural Information Processing Systems

We propose a general framework to design posterior sampling methods for model-based RL. We show that the proposed algorithms can be analyzed by reducing regret to Hellinger distance in conditional probability estimation. We further show that optimistic posterior sampling can control this Hellinger distance, when we measure model error via data likelihood. This technique allows us to design and analyze unified posterior sampling algorithms with state-of-the-art sample complexity guarantees for many model-based RL settings. We illustrate our general result in many special cases, demonstrating the versatility of our framework.




Variational Gaussian Processes For Linear Inverse Problems: Supplementary material

Neural Information Processing Systems

The results from one experiment are presented in Figure 2. We plot the resulting variational approximation of the posterior for The conclusions we draw from this experiment are the same as those in Section 4. With the optimal On the left-hand side of Figure 3, we also report the computation times of the methods, and we highlight that the true posterior takes much longer than any of the variational approximations. Again, similar conclusions can be drawn as in the previous sections. Computed T omography (CT) Imaging and Medical Single Photon Emission Computed T omography (SPECT): In CT scans, X-ray measurements are taken from different angles around a patient, and the Radon transform is used to reconstruct a cross-sectional image (slice) of the patient's body. This helps doctors visualize internal structures and diagnose various medical conditions. The Radon transform is used in the image reconstruction process for SPECT.