equivalence relation
Embeddings as Probabilistic Equivalence in Logic Programs
The integration of logic programs with embedding models resulted in a class of neurosymbolic frameworks that jointly learn symbolic rules and representations for the symbols in the logic (constant or predicate). The key idea that enabled this integration was the differentiable relaxation of unification, the algorithm for variable instantiation during inference in logic programs. Unlike unification, its relaxed counterpart exploits the similarity between symbols in the embedding space to decide when two symbols are semantically equivalent. We show that this similarity between symbols violates the transitive law of equivalence, leading to undesirable side effects in learning and inference. To alleviate those side effects, we are the first to revamp the well-known possible world semantics of probabilistic logic programs into new semantics called equivalence semantics. In our semantics, a probabilistic logic program induces a probability distribution over all possible equivalence relations between symbols, instead of a probability distribution over all possible subsets of probabilistic facts. We propose a factorization of the equivalence distribution using latent random variables and characterize its expressivity. Additionally, we propose both exact and approximate techniques for reasoning in our semantics. Experiments on well-known benchmarks show that the equivalence semantics leads to neurosymbolic models with up to 42% higher results than state-of-the-art baselines.
e8a642ed6a9ad20fb159472950db3d65-Supplemental.pdf
Methods for handling missing data has been extensively studied in the past few decades. Those methods can be roughly classified into two categories: complete case analysis (CCA) based, and imputationbasedmethods. CCAbasedmethods,suchaslistwisedeletion[1]andpairwisedeletion [31] focuses on deleting data instances that contains missing entries, and keeping those that are complete. Standardtechniquesof single imputation include mean/zero imputation, regression-based imputation [1], no-parametric methods [15,54]. For the factorized priorp(Z|U) of the i-VAE component of GINA, we used 15 a linear network with one auxiliary input (which is set to be fully observed dimension,X1).
Heuristics for Combinatorial Optimization via Value-based Reinforcement Learning: A Unified Framework and Analysis
Davidovich, Orit, Shtern, Shimrit, Wasserkrug, Segev, Megiddo, Nimrod
Since the 1990s, considerable empirical work has been carried out to train statistical models, such as neural networks (NNs), as learned heuristics for combinatorial optimization (CO) problems. When successful, such an approach eliminates the need for experts to design heuristics per problem type. Due to their structure, many hard CO problems are amenable to treatment through reinforcement learning (RL). Indeed, we find a wealth of literature training NNs using value-based, policy gradient, or actor-critic approaches, with promising results, both in terms of empirical optimality gaps and inference runtimes. Nevertheless, there has been a paucity of theoretical work undergirding the use of RL for CO problems. To this end, we introduce a unified framework to model CO problems through Markov decision processes (MDPs) and solve them using RL techniques. We provide easy-to-test assumptions under which CO problems can be formulated as equivalent undiscounted MDPs that provide optimal solutions to the original CO problems. Moreover, we establish conditions under which value-based RL techniques converge to approximate solutions of the CO problem with a guarantee on the associated optimality gap. Our convergence analysis provides: (1) a sufficient rate of increase in batch size and projected gradient descent steps at each RL iteration; (2) the resulting optimality gap in terms of problem parameters and targeted RL accuracy; and (3) the importance of a choice of state-space embedding. Together, our analysis illuminates the success (and limitations) of the celebrated deep Q-learning algorithm in this problem context.