Country
A Multi-Agent Control Architecture for a Rescue Robot
Haber, Adam (University of New South Wales)
Despite many years of research and progress in the field tecture, the testing environment in which the implementation of artificial intelligence, there is still no universally accepted will be embedded, and then describes the work completed so definition of the word intelligence. Finally we will address the body of work still to be completed identified a multitude of tasks, skills, and behaviours that and plans for future research. Much A.I research is focused Although the initial thrust multiplicity, heterogeneity, and adaptability. of A.I in the 1950s was towards this kind of integrated system, Multiplicity. One of the few points of consensus within in recent times the problem of integration has become cognitive architecture research is that architectures must be conspicuous by its absence in the field, but is essential to improve composed of modular, independent components. This is a our design of complete intelligent systems, and consequently consequence of the multifaceted nature of information processing, our understanding of our own brains.
CCE: A Coupled Framework of Clustering Ensembles
She, Zhong (University of Technology, Sydney) | Wang, Can (University of Technology, Sydney) | Cao, Longbing (University of Technology, Sydney)
Clustering ensemble mainly relies on the pairwise similarity to capture the consensus function. However, it usually considers each base clustering independently, and treats the similarity measure roughly with either 0 or 1. To address these two issues, we propose a coupled framework of clustering ensembles CCE, and exemplify it with the coupled version CCSPA for CSPA. Experiments demonstrate the superiority of CCSPA over baseline approaches in terms of the clustering accuracy.
Bayesian Unification of Sound Source Localization and Separation with Permutation Resolution
Otsuka, Takuma (Kyoto University) | Ishiguro, Katsuhiko (NTT Corporation) | Sawada, Hiroshi (NTT Corporation) | Okuno, Hiroshi G. (Kyoto University)
Sound source localization and separation with permutation resolution are essential for achieving a computational auditory scene analysis system that can extract useful information from a mixture of various sounds. Because existing methods cope separately with these problems despite their mutual dependence, the overall result with these approaches can be degraded by any failure in one of these components. This paper presents a unified Bayesian framework to solve these problems simultaneously where localization and separation are regarded as a clustering problem. Experimental results confirm that our method outperforms state-of-the-art methods in terms of the separation quality with various setups including practical reverberant environments.
Catch Me If You Can: Pursuit and Capture in Polygonal Environments with Obstacles
Klein, Kyle (University of California, Santa Barbara) | Suri, Subhash (University of California, Santa Barbara)
We resolve a several-years old open question in visibility-based pursuit evasion:ย how many pursuers are needed to capture an evader in an arbitrary polygonalย environment with obstacles? The evader is assumed to be adversarial, moves withย the same maximum speed as pursuers, and is "sensed'' by a pursuer only when it lies inline-of-sight of that pursuer. The players move in discrete time steps, and theย capture occurs when a pursuer reaches the position of the evader on its move.ย Our main result is that O( โ h + log n ) pursuers can always win the gameย with a deterministic search strategy in any polygon with n vertices and h obstacles (holes). In order to achieve this bound, however, we argueย that the environment must satisfy a minimum feature size property,ย which essentially requires the minimum distance between any two verticesย to be of the same order as the speed of the players. Without theย minimum feature size assumption, we show that ฮฉ < ( โ( n /log n )) pursuersย are needed in the worst-case even for simply-connected (hole-free)ย polygons of n vertices! ย This reveals an unexpected subtlety that seems to have been overlookedin previous work claiming that O(log n ) pursuers can always win insimply-connected n -gons. ย Our lower bound also shows that capturing an evader is inherently more difficult than just "seeing" it because O(log n ) pursuers are provably sufficient for line-of-sight detection even against an arbitrarily fast evaderin simple n -gons.
Symbolic Variable Elimination for Discrete and Continuous Graphical Models
Sanner, Scott (NICTA and Australian National University) | Abbasnejad, Ehsan (Australian National Universityย and NICTA)
Probabilistic reasoning in the real-world often requires inference incontinuous variable graphical models, yet there are few methods for exact, closed-form inference when joint distributions are non-Gaussian. To address this inferential deficit, we introduce SVE -- a symbolic extension of the well-known variable elimination algorithm to perform exact inference in an expressive class of mixed discrete and continuous variable graphical models whose conditional probability functions can be well-approximated as piecewise combinations of polynomials with bounded support. Using this representation, we show that we can compute all of the SVE operations exactly and in closed-form, which crucially includes definite integration w.r.t. multivariate piecewise polynomial functions. To aid in the efficient computation and compact representation of this solution, we use an extended algebraic decision diagram (XADD) data structure that supports all SVE operations. We provide illustrative results for SVE on probabilistic inference queries inspired by robotics localization and tracking applications that mix various continuous distributions; this represents the first time a general closed-form exact solution has been proposed for this expressive class of discrete/continuous graphical models.
Sequential Decision Making with Rank Dependent Utility: A Minimax Regret Approach
Jeantet, Gildas (AiRPX) | Perny, Patrice (University Pierre and Marie Curie and CNRS) | Spanjaard, Olivier (University Pierre and Marie Curie and CNRS)
This paper is devoted to sequential decision making with Rank Dependent expected Utility (RDU). This decision criterion generalizes Expected Utility and enables to model a wider range of observed (rational) behaviors. In such a sequential decision setting, two conflicting objectives can be identified in the assessment of a strategy: maximizing the performance viewed from the initial state (optimality), and minimizing the incentive to deviate during implementation (deviation-proofness). In this paper, we propose a minimax regret approach taking these two aspects into account, and we provide a search procedure to determine an optimal strategy for this model. Numerical results are presented to show the interest of the proposed approach in terms of optimality, deviation-proofness and computability.
Covering Number as a Complexity Measure for POMDP Planning and Learning
Zhang, Zongzhang (University of Science and Technology of China) | Littman, Michael (Rutgers University) | Chen, Xiaoping (University of Science and Technology of China)
Finding a meaningful way of characterizing the difficulty of partially observable Markov decision processes (POMDPs) is a core theoretical problem in POMDP research. State-space size is often used as a proxy for POMDP difficulty, but it is a weak metric at best. Existing work has shown that the covering number for the reachable belief space, which is a set of belief points that are reachable from the initial belief point, has interesting links with the complexity of POMDP planning, theoretically. In this paper, we present empirical evidence that the covering number for the reachable belief space (or just ``covering number", for brevity) is a far better complexity measure than the state-space size for both planning and learning POMDPs on several small-scale benchmark problems. We connect the covering number to the complexity of learning POMDPs by proposing a provably convergent learning algorithm for POMDPs without reset given knowledge of the covering number.
MAXSAT Heuristics for Cost Optimal Planning
Zhang, Lei (Nanjing University) | Bacchus, Fahiem (University of Toronto)
The cost of an optimal delete relaxed plan, known as h+, is a powerful admissible heuristic but is in general intractable to compute. In this paper we examine the problem of computing h+ by encoding it as a MAXSAT problem. We develop a new encoding that utilizes constraint generation to support the computation of a sequence of increasing lower bounds on h+. We show a close connection between the computations performed by a recent approach for solving MAXSAT and a hitting set approach recently proposed for computing h+. Using this connection we observe that our MAXSAT computation can be initialized with a set of landmarks computed by LM-cut. By judicious use of MAXSAT solving along with a technique of lazy heuristic evaluation we obtain speedups for finding optimal plans over LM-cut on a number of domains. Our approach enables the exploitation of continued progress in MAXSAT solving, and also makes it possible to consider computing or approximating heuristics that are even more informed that h+ by, for example, adding some information about deletes back into the encoding.
Improving Hierarchical Planning Performance by the Use of Landmarks
Elkawkagy, Mohamed (Ulm University) | Bercher, Pascal (Ulm University) | Schattenberg, Bernd (Ulm University) | Biundo, Susanne (Ulm University)
In hierarchical planning, landmarks are tasks that occur on any search path leading from the initial plan to a solution. In this work, we present novel domain-independent planning strategies based on such hierarchical landmarks. Our empirical evaluation on four benchmark domains shows that these landmark-aware strategies outperform established search strategies in many cases.
Heart Rate Topic Models
Esbroeck, Alexander Van (University of Michigan) | Chia, Chih-Chun (University of Michigan) | Syed, Zeeshan (University of Michigan)
A key challenge in reducing the burden of cardiovascular disease is matching patients to treatments that are most appropriate for them. Different cardiac assessment tools have been developed to address this goal. Recent research has focused on heart rate motifs, i.e., short-term heart rate sequences that are over- or under-represented in long-term electrocardiogram (ECG) recordings of patients experiencing cardiovascular outcomes, which provide novel and valuable information for risk stratification. However, this approach can leverage only a small number of motifs for prediction and results in difficult to interpret models. We address these limitations by identifying latent structure in the large numbers of motifs found in long-term ECG recordings. In particular, we explore the application of topic models to heart rate time series to identify functional sets of heart rate sequences and to concisely describe patients using task-independent features for various cardiovascular outcomes. We evaluate the approach on a large collection of real-world ECG data, and investigate the performance of topic mixture features for the prediction of cardiovascular mortality. The topics provided an interpretable representation of the recordings and maintained valuable information for clinical assessment when compared with motif frequencies, even after accounting for commonly used clinical risk scores.