Uncertainty
Reviews: New Liftable Classes for First-Order Probabilistic Inference
This paper makes a concrete contribution to lifted probabilistic inference, showing that the domain recursion rule can be used to solve certain interesting problems that are intractable for state-of-the-art lifted inference software. The insights here seem likely to be incorporated into upcoming versions of those packages. However, some of the statements in the paper are not sufficiently precise. The description of the domain recursion rule itself (p. 5, top) is much less precise than the definition in the 2011 paper that introduced it. It's not clear what the preconditions are for applying the rule or exactly how it transforms the theory. Also, the description mentions caching (line 175), but it would be helpful to explain how the inference algorithm ends up making multiple calls to the cache.
Reviews: Stein Variational Gradient Descent: A General Purpose Bayesian Inference Algorithm
Overall, I found the paper interesting; the paper offers new theory as well as numerical results comparable to the state of the art on decently difficult datasets. Perhaps due to space constraints, an important part of the paper (section 3.2) - the inference algorithm - is poorly explained. In particular, I initially thought that the use of particles meant that the approximating distribution was a sum of Dirac delta functions - but that cannot be the case since, even with many particles, the'posterior' would degenerate into the MAP (note that in similar work, authors either use particles when p(x) involves discrete x variables, as in Kulkarni et al, or'smooth' the particles to approximate a continuous distribution, as in Gershman et al). Instead, it looks like the algorithm works directly on samples of the distribution q0, q1.. (hence the vague'for whatever distribution q that {xi}ni 1 currently represents'). It is tempting to consider q_i to be a kernel density estimate (mixture of normals with fixed width), and see if we can approximate equation 9 for that representation to be stable.
Reviews: A Bayesian method for reducing bias in neural representational similarity analysis
The paper explains well how computing RSA using estimates of regression weights can result in a biased similarity matrix. However, in many cases in neuroscience, the RSA is computed directly on the patterns of activity, and not the estimates of regression weights beta. This diminishes the relevance of this paper to the neuroscience field. The authors very briefly address this alternate way of computing RSA in lines 123-128. It is unclear how this alternative RSA computation is biased if it does not depend on a proxy for beta estimates, and needs to be addressed further.
Reviews: Confusions over Time: An Interpretable Bayesian Model to Characterize Trends in Decision Making
The authors motivate the proposed model with the setting in which items have "true" but unobserved labels/ratings and the observed labels/ratings given by evaluators are potentially incorrect. This differs from the very common problem in recommendation systems or collaborative filtering where evaluators provide their subjective ratings but there is not assumed to be any "true" rating (e.g., users of Netflix giving 1-5 star ratings to movies). This seems like a common but underexplored setting that is worthy of further study within machine learning. The authors are also right to highlight interpretability as a desired aspect of any machine learning solution that may yield post-hoc insights into common human biases and thus suggest corrective measures. This paper does a good job of motivating the proposed model and situating it within the crowdsourcing and human annotation literature.
Reviews: Near-Optimal Smoothing of Structured Conditional Probability Matrices
If my understanding is correct, Theorem 1 of the authors does not quite apply to their algorithm ADD-1/2-Smoothed Low-Rank. Instead, it applies to the non-computable algorithm where they assume that they have a minimizer of the objective function in Theorem 3. It is not clear if the alternating optimization algorithm proposed in the paper is guaranteed to converge to a minimizer of the objective in Theorem 3. If this is true, the authors should mention this before stating Theorem 1 to avoid misleading the reader. The "discounting" seems important from the Experiments section but this is not described in the main paper. If this is so important, the authors should make room for this in the main paper. The main results (Theorem 1 and 2) are not so surprising given that this is almost a parametric estimation problem with mk parameters (so the rates should be km/n).
Reviews: PAC-Bayesian Theory Meets Bayesian Inference
The paper is well written and theoretically strong. It's been conjectured in the past that there should be links between PAC-Bayes theory and Bayesian inference, but to my knowledge this is the first theoretically complete demonstration of such links. Some comments: - In eq(8) (and above) the notion of a prior with bounded likelihood is introduced. Am I right in thinking that this is a data-dependent prior, since it can only be known if the likelihood will be bounded for a given prior after observing the data? If this is not the case can you explain how such a prior is possible?
Reviews: Rényi Divergence Variational Inference
This is a very good and technically sound paper, containing a significant amount of material. The theoretical investigation of the properties of alpha-divergence minimization is thorough, clear and detailed. The paper provides significant theoretical insight and understanding into alpha-divergence minimization and optimization-based approximate inference in general. My biggest concern about the alpha-divergence framework is whether its theoretical richness and elegance actually translates to practical methods. In other words, I'm not sure that the practical aspects of it are appealing enough to convince practitioners of variational inference to switch to alpha-divergence minimization instead.
Reviews: Fast ε-free Inference of Simulation Models with Bayesian Conditional Density Estimation
The most original part of the paper is Proposition 1, which is quite interesting. However, I have some doubts regarding the assumptions leading to formula (2). As explained in the appendix, this formula holds if q_theta is complex enough to make so that the KL distance is zero. Now, in a realistic example and with finite sample size, q_theta can't be very complex, otherwise it would over-fit. Hence, (2) holds only approximately.
Reviews: Tractable Operations for Arithmetic Circuits of Probabilistic Models
The novelty is relatively low since the compilation algorithm presented here is very similar to the compilation algorithm for AND/OR Multi-Valued Decision Diagrams (AOMDDs), which are a special case of PSDDs. Theorem 6 follows directly from the similar theorem that already holds for AOMDDs. The multiplication algorithm in section 3 is essentially the same as the one for SDDs, and it is no surprise that it operates in polytime. The main novelty and significance is in the experimental results, which suggest that PSDD compilation is more effective than AOMDD compilation. The paper would be more interesting if it gave a deeper analysis of where these advantages come from.
Reviews: Reward Augmented Maximum Likelihood for Neural Structured Prediction
The paper is a superbly written account of a simple idea that appears to work very well. The approach can straightforwardly be applied to existing max-likelihood (ML) trained models in order to in principle take into account the task reward during training and is computationally much more efficient than alternative non ML based approaches. This work risks being underappreciated as proposing but a simple addition of artificial structured-label noise, but I think the specific link with structured output task reward is sufficiently original, and the paper also uncovers important theoretical insight by revealing the formal relationship between the proposed reward augmented ML and RL-based regularized expected reward objectives. So while it works surprisingly well, you haven't yet clearly demonstrated empirically that using a truly *task-reward derived* payoff distribution is beneficial. One way to convincingly demonstrate that would be if you did your envisioned BLEU importance reweighted sampling, and were able to show that it improves the BLEU test score over your current simpler edit-distance based label noise.