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Sample-adaptive Multiple Kernel Learning

AAAI Conferences

Existing multiple kernel learning (MKL) algorithms \textit{indiscriminately} apply a same set of kernel combination weights to all samples. However, the utility of base kernels could vary across samples and a base kernel useful for one sample could become noisy for another. In this case, rigidly applying a same set of kernel combination weights could adversely affect the learning performance. To improve this situation, we propose a sample-adaptive MKL algorithm, in which base kernels are allowed to be adaptively switched on/off with respect to each sample. We achieve this goal by assigning a latent binary variable to each base kernel when it is applied to a sample. The kernel combination weights and the latent variables are jointly optimized via margin maximization principle. As demonstrated on five benchmark data sets, the proposed algorithm consistently outperforms the comparable ones in the literature.


Preprocessing for Propositional Model Counting

AAAI Conferences

Chavira and Darwiche 2008; Apsel and Brafman 2012)) and forms of planning (see e.g., (Palacios et al. 2005; It and more importantly the variable elimination rule (replacing proves useful when the problem under consideration (e.g., in the input CNF formula all the clauses containing a the satisfiability issue) can be solved more efficiently when given variable x by the set of all their resolvents over x) or the input formula has been first preprocessed (of course, the blocked clause elimination rule (removing every clause the preprocessing time is taken into account in the global containing a literal such that every resolvent obtained by resolving solving time). Some preprocessing techniques are nowadays on it is a valid clause).


Efficient Generalized Fused Lasso and its Application to the Diagnosis of Alzheimerโ€™s Disease

AAAI Conferences

Generalized fused lasso (GFL) penalizes variables with L1 norms based both on the variables and their pairwise differences. GFL is useful when applied to data where prior information is expressed using a graph over the variables. However, the existing GFL algorithms incur high computational costs and they do not scale to high-dimensional problems. In this study, we propose a fast and scalable algorithm for GFL. Based on the fact that fusion penalty is the Lov'asz extension of a cut function, we show that the key building block of the optimization is equivalent to recursively solving parametric graph-cut problems. Thus, we use a parametric flow algorithm to solve GFL in an efficient manner. Runtime comparisons demonstrated a significant speed-up compared with the existing GFL algorithms. By exploiting the scalability of the proposed algorithm, we formulated the diagnosis of Alzheimer's disease as GFL. Our experimental evaluations demonstrated that the diagnosis performance was promising and that the selected critical voxels were well structured i.e., connected, consistent according to cross-validation and in agreement with prior clinical knowledge.


A Model Attention and Selection Framework for Estimation of Many Variables, with Applications to Estimating Object States in Large Spatial Environments

AAAI Conferences

Robots performing service tasks such as cooking and cleaning in human-centric environments require knowledge of certain environmental states in order to complete tasks successfully. While much effort has gone into developing various estimators for deriving distributions on values of unknown states, less attention has been placed on why the particular estimation problem arises. In this work, I argue that state estimation should no longer be treated as a black box. Estimating large sets of variables is computationally costly; just because a technique exists to estimate the values of certain variables does not justify its application. For robots whose ultimate mission is to complete tasks, only variables that are relevant to successful completion should be estimated. I propose to initially only track a minimal set of directly-relevant variables (attention), and gradually increase the sophistication of models on-demand (refinement), in a local fashion. This estimator refinement process is triggered by violations in expectations of task success (mismatch). This model selection framework is demonstrated through a proof-of-concept case study.


Coordination of Multiple Teams of Robots for an Optimal Global Plan

AAAI Conferences

Also, we do many application domains, ranging from search and rescue not assume that all teams are in the same workspace, or all operations to exploration missions, service robotics to cognitive robots are of the same sort. Moreover, our goal is not to find factories. In these domains, the goal is for all teams any coordination of teams that would allow decoupling of to complete their tasks as soon as possible, and should the their local plans, but to find a coordination of teams for an need arise, teams help each other by lending robots.


Lifetime Lexical Variation in Social Media

AAAI Conferences

As the rapid growth of online social media attracts a large number of Internet users, the large volume of content generated by these users also provides us with an opportunity to study the lexical variation of people of different ages. In this paper, we present a latent variable model that jointly models the lexical content of tweets and Twitter usersโ€™ ages. Our model inherently assumes that a topic has not only a word distribution but also an age distribution. We propose a Gibbs-EM algorithm to perform inference on our model. Empirical evaluation shows that our model can learn meaningful age-specific topics such as โ€œschoolโ€ for teenagers and โ€œhealthโ€ for older people. Our model can also be used for age prediction and performs better than a number of baseline methods.


Imputation, Social Choice, and Partial Preferences

AAAI Conferences

Within the field of Artificial Intelligence (AI) research, Vote (STV) select winners from sets of ballot. For example, the subfield of Computational Social Choice considers under plurality candidate X has won this election by virtue the application of AI techniques to problems in Social of having being at the top of the largest number of ballots. Under STV Y would win instead. Starting in the early 1990's, computer scientists began to In this work, we model voters as having partial orderings take an interest in social choice. Initial work was concerned over the candidates for their preferences, instead of linear with circumventing the impossibility results implied orderings.


Small-Variance Asymptotics for Dirichlet Process Mixtures of SVMs

AAAI Conferences

Infinite SVM (iSVM) is a Dirichlet process (DP) mixture of large-margin classifiers. Though flexible in learning nonlinear classifiers and discovering latent clustering structures, iSVM has a difficult inference task and existing methods could hinder its applicability to large-scale problems. This paper presents a small-variance asymptotic analysis to derive a simple and efficient algorithm, which monotonically optimizes a max-margin DP-means (M2DPM) problem, an extension of DP-means for both predictive learning and descriptive clustering. Our analysis is built on Gibbs infinite SVMs, an alternative DP mixture of large-margin machines, which admits a partially collapsed Gibbs sampler without truncation by exploring data augmentation techniques. Experimental results show that M2DPM runs much faster than similar algorithms without sacrificing prediction accuracies.


Coactive Learning for Locally Optimal Problem Solving

AAAI Conferences

Coactive learning is an online problem solving setting where the solutions provided by a solver are interactively improved by a domain expert, which in turn drives learning. In this paper we extend the study of coactive learning to problems where obtaining a globally optimal or near-optimal solution may be intractable or where an expert can only be expected to make small, local improvements to a candidate solution. The goal of learning in this new setting is to minimize the cost as measured by the expert effort over time. We first establish theoretical bounds on the average cost of the existing coactive Perceptron algorithm. In addition, we consider new online algorithms that use cost-sensitive and Passive-Aggressive (PA) updates, showing similar or improved theoretical bounds. We provide an empirical evaluation of the learners in various domains, which show that the Perceptron based algorithms are quite effective and that unlike the case for online classification, the PA algorithms do not yield significant performance gains.