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Multiagent Metareasoning through Organizational Design
Sleight, Jason (University of Michigan) | Durfee, Edmund H. (University of Michigan)
We formulate an approach to multiagent metareasoning that uses organizational design to focus each agent's reasoning on the aspects of its local problem that let it make the most worthwhile contributions to joint behavior. By employing the decentralized Markov decision process framework, we characterize an organizational design problem that explicitly considers the quantitative impact that a design has on both the quality of the agents' behaviors and their reasoning costs. We describe an automated organizational design process that can approximately solve our organizational design problem via incremental search, and present techniques that efficiently estimate the incremental impact of a candidate organizational influence. Our empirical evaluation confirms that our process generates organizational designs that impart a desired metareasoning regime upon the agents.
Towards Topological-Transformation Robust Shape Comparison: A Sparse Representation Based Manifold Embedding Approach
Gao, Longwen (Fudan University) | Zhou, Shuigeng (Fudan University)
Non-rigid shape comparison based on manifold embeddingusing Generalized Multidimensional Scaling(GMDS) has attracted much attention for its highaccuracy. However, this method requires that shape surfaceis not elastic. In other words, it is sensitive totopological transformations such as stretching and compressing.To tackle this problem, we propose a new approachthat constructs a high-dimensional space to embedthe manifolds of shapes based on sparse representation,which is able to completely withstand rigid transformationsand considerably tolerate topological transformations.Experiments on TOSCA shapes validate theproposed approach.
Testable Implications of Linear Structural Equation Models
Chen, Bryant (University of California, Los Angeles) | Tian, Jin (Iowa State University) | Pearl, Judea (University of California, Los Angeles)
In causal inference, all methods of model learning rely on testable implications, namely, properties of the joint distribution that are dictated by the model structure. These constraints, if not satisfied in the data, allow us to reject or modify the model. Most common methods of testing a linear structural equation model (SEM) rely on the likelihood ratio or chi-square test which simultaneously tests all of the restrictions implied by the model. Local constraints, on the other hand, offer increased power (Bollen and Pearl, 2013; McDonald, 2002) and, in the case of failure, provide the modeler with insight for revising the model specification. One strategy of uncovering local constraints in linear SEMs is to search for overidentified path coefficients. While these overidentifying constraints are well known, no method has been given for systematically discovering them. In this paper, we extend the half-trek criterion of (Foygel et al., 2012) to identify a larger set of structural coefficients and use it to systematically discover overidentifying constraints. Still open is the question of whether our algorithm is complete.
Finding the k-best Equivalence Classes of Bayesian Network Structures for Model Averaging
Chen, Yetian (Iowa State University) | Tian, Jin (Iowa State University)
In this paper we develop an algorithm to find the k-best equivalence classes of Bayesian networks. Our algorithm is capable of finding much more best DAGs than the previous algorithm that directly finds the k-best DAGs (Tian, He and Ram 2010). We demonstrate our algorithm in the task of Bayesian model averaging. Empirical results show that our algorithm significantly outperforms the k-best DAG algorithm in both time and space to achieve the same quality of approximation. Our algorithm goes beyond the maximum-a-posteriori (MAP) model by listing the most likely network structures and their relative likelihood and therefore has important applications in causal structure discovery.
Gradient Descent with Proximal Average for Nonconvex and Composite Regularization
Zhong, Wenliang (Hong Kong University of Science and Technology) | Kwok, James T. (Hong Kong University of Science and Technology)
Sparse modeling has been highly successful in many real-world applications. While a lot of interests have been on convex regularization, recent studies show that nonconvexregularizers can outperform their convex counterparts in many situations.However, the resulting nonconvex optimization problems are often challenging, especiallyfor composite regularizers such as the nonconvex overlapping group lasso. In thispaper, byusing a recent mathematical tool known as the proximal average,we propose a novel proximal gradient descent method for optimization with a wide class of nonconvex and composite regularizers.Instead of directlysolving the proximal stepassociated with a composite regularizer, we average thesolutions from the proximal problems of the constituent regularizers. This simple strategy has guaranteed convergenceand low per-iteration complexity.Experimental results on a number of synthetic andreal-world data sets demonstrate the effectiveness and efficiency of theproposed optimization algorithm, and also the improved classification performanceresulting from thenonconvex regularizers.
Non-Linear Label Ranking for Large-Scale Prediction of Long-Term User Interests
Djuric, Nemanja (Yahoo! Labs) | Grbovic, Mihajlo (Yahoo! Labs) | Radosavljevic, Vladan (Yahoo! Labs) | Bhamidipati, Narayan (Yahoo! Labs) | Vucetic, Slobodan (Temple University)
We consider the problem of personalization of online services from the viewpoint of ad targeting, where we seek to find the best ad categories to be shown to each user, resulting in improved user experience and increased advertiser's revenue. We propose to address this problem as a task of ranking the ad categories depending on a user's preference, and introduce a novel label ranking approach capable of efficiently learning non-linear, highly accurate models in large-scale settings. Experiments on real-world advertising data set with more than 3.2 million users show that the proposed algorithm outperforms the existing solutions in terms of both rank loss and top-K retrieval performance, strongly suggesting the benefit of using the proposed model on large-scale ranking problems.
A Data Complexity Approach to Kernel Selection for Support Vector Machines
Valerio, Roberto (University of Houston) | Vilalta, Ricardo (University of Houston)
We describe a data complexity approach to kernel selection based on the behavior of polynomial and Gaussian kernels. Our resultsshow how the use of a Gaussian kernel produces a gram matrix with useful local information that has no equivalent counterpart inpolynomial kernels.By exploiting neighborhood information embedded by data complexity measures, we are able to carry out a form of meta-generalization.Our goal is to predict which data sets are more favorable to particular kernels (Gaussian or polynomial).The end result is a framework to improve the model selection process in Support Vector Machines.
Theory of Cooperation in Complex Social Networks
Ranjbar-Sahraei, Bijan (Maastricht University) | Ammar, Haitham Bou (University of Pennsylvania) | Bloembergen, Daan (Maastricht University) | Tuyls, Karl (University of Liverpool) | Weiss, Gerhard (Maastricht University)
This paper presents a theoretical as well as empirical study on the evolution of cooperation on complex social networks, following the continuous action iterated prisoner's dilemma (CAIPD) model. In particular, convergence to network-wide agreement is proven for both evolutionary networks with fixed interaction dynamics, as well as for coevolutionary networks where these dynamics change over time. Moreover, an extension to the CAIPD model is proposed that allows to model influence on the evolution of cooperation in social networks. As such, this work contributes to a better understanding of behavioral change on social networks, and provides a first step towards their active control.
A Multiarmed Bandit Incentive Mechanism for Crowdsourcing Demand Response in Smart Grids
Jain, Shweta (Indian Institute of Science, Bangalore) | Narayanaswamy, Balakrishnan (University of California, San Diego) | Narahari, Y. (Indian Institute of Science, Bangalore)
Demand response is a critical part of renewable integration and energy cost reduction goals across the world. Motivated by the need to reduce costs arising from electricity shortage and renewable energy fluctuations, we propose a novel multiarmed bandit mechanism for demand response (MAB-MDR) which makes monetary offers to strategic consumers who have unknown response characteristics, to incetivize reduction in demand. Our work is inspired by a novel connection we make to crowdsourcing mechanisms. The proposed mechanism incorporates realistic features of the demand response problem including time varying and quadratic cost function. The mechanism marries auctions, that allow users to report their preferences, with online algorithms, that allow distribution companies to learn user-specific parameters. We show that MAB-MDR is dominant strategy incentive compatible, individually rational, and achieves sublinear regret. Such mechanisms can be effectively deployed in smart grids using new information and control architecture innovations and lead to welcome savings in energy costs.
Synthesis of Geometry Proof Problems
Alvin, Chris (Louisiana State University, Baton Rouge) | Gulwani, Sumit (Microsoft Research) | Majumdar, Rupak (Max Planck Institute for Software Systems) | Mukhopadhyay, Supratik (Louisiana State University, Baton Rouge)
This paper presents a semi-automated methodology for generating geometric proof problems of the kind found in a high-school curriculum. We formalize the notion of a geometry proof problem and describe an algorithm for generating such problems over a user-provided figure. Our experimental results indicate that our problem generation algorithm can effectively generate proof problems in elementary geometry. On a corpus of 110 figures taken from popular geometry textbooks, our system generated an average of about 443 problems per figure in an average time of 4.7 seconds per figure.