Statistical Learning
Decision-Theoretic Clustering of Strategies
Bard, Nolan (University of Alberta) | Nicholas, Deon (University of Waterloo) | Szepesvári, Csaba (University of Alberta) | Bowling, Michael (University of Alberta)
Clustering agents by their behaviour can be crucial for building effective agent models. Traditional clustering typically aims to group entities together based on a distance metric, where a desirable clustering is one where the entities in a cluster are spatially close together. Instead, one may desire to cluster based on actionability, or the capacity for the clusters to suggest how an agent should respond to maximize their utility with respect to the entities. Segmentation problems examine this decision-theoretic clustering task. Although finding optimal solutions to these problems is computationally hard, greedy-based approximation algorithms exist. However, in settings where the agent has a combinatorially large number of candidate responses whose utilities must be considered, these algorithms are often intractable. In this work, we show that in many cases the utility function can be factored to allow for an efficient greedy algorithm even when there are exponentially large response spaces. We evaluate our technique theoretically, proving approximation bounds, and empirically using extensive-form games by clustering opponent strategies in toy poker games. Our results demonstrate that these techniques yield dramatically improved clusterings compared to a traditional distance-based clustering approach in terms of both subjective quality and utility obtained by responding to the clusters.
Contract Bridge Bidding by Learning
Ho, Chun-Yen (National Taiwan University) | Lin, Hsuan-Tien (National Taiwan University)
Contract bridge is an example of an incomplete information game for which computers typically do not perform better than expert human bridge players. In particular, the typical bidding decisions of human bridge players are difficult to mimic with a computer program, and thus automatic bridge bidding remains to be a challenging research problem. Currently, the possibility of automatic bidding without mimicking human players has not been fully studied. In this work, we take an initiative to study such a possibility for the specific problem of bidding without competition. We propose a novel learning framework to let a computer program learn its own bidding decisions. The framework transforms the bidding problem into a learning problem, and then solves the problem with a carefully designed model that consists of cost-sensitive classifiers and upper-confidence-bound algorithms. We validate the proposed model and find that it performs competitively to the champion computer bridge program that mimics human bidding decisions.
Real-Time Optimal Selection of Multirobot Coalition Formation Algorithms Using Conceptual Clustering
Sen, Sayan Dev (Vanderbilt University) | Adams, Julie Ann (Vanderbilt University)
The presented framework is the The multirobot coalition formation problem seeks to intelligently first to leverage a conceptual clustering technique to partition partition a team of heterogeneous robots into any set of coalition formation algorithms in order to derive coalitions for a set of real-world tasks. Besides being N Pan optimal hierarchy classification tree, given any classification complete (Sandholm et al. 1999), the problem is also hard taxonomy. The results contribute to the state-ofthe-art to approximate (Service and Adams 2011a). Traditional approaches in multiagent systems by demonstrating the existence to solving the problem include a number of greedy of crucial patterns and intricate relationships among existing algorithms (Shehory and Kraus 1998; Vig and Adams coalition algorithms.
Predicting Bike Usage for New York City’s Bike Sharing System
Singhvi, Divya (Cornell University) | Singhvi, Somya (Cornell University) | Frazier, Peter I. (Cornell University) | Henderson, Shane G. (Cornell University) | Mahony, Eoin O' (Cornell University) | (Cornell University) | Shmoys, David B. (Cornell University) | Woodard, Dawn B.
Bike sharing systems consist of a fleet of bikes placed in a network of docking stations. These bikes can then be rented and returned to any of the docking stations after usage. Predicting unrealized bike demand at locations currently without bike stations is important for effectively designing and expanding bike sharing systems. We predict pairwise bike demand for New York City’s Citi Bike system. Since the system is driven by daily commuters we focus only on the morning rush hours between 7:00 AM to 11:00 AM during weekdays. We use taxi usage, weather and spatial variables as covariates to predict bike demand, and further analyze the influence of precipitation and day of week. We show that aggregating stations in neighborhoods can substantially improve predictions. The presented model can assist planners by predicting bike demand at a macroscopic level, between pairs of neighborhoods.
A Proposal for Behavior Prediction via Estimating Agents’ Evaluation Functions Using Prior Observations of Behavior
Loftin, Robert Tyler (North Carolina State University) | Roberts, David L. (North Carolina State University)
In this work we present a theoretical approach (not currently implemented), to the problem of predicting agent behavior. The ultimate goal of this work is to learn models that can be used to predict the future actions of intelligent agents, based on previously recorded data on those agents’ behavior. We believe that we can improve the predictive accuracy of our models by assuming that an agent reasons about the actions it takes, and trying to explicitly model that reasoning process. Here, we model an agent’s reasoning process as a form of Monte-Carlo search, and attempt to learn a state evaluation function that, when used with this planning algorithm, yields a similar distribution of actions given the current state of the world as we observe in the data. While it is simple to simulate Monte-Carlo search given an evaluation function, it is much more difficult to determine an evaluation function that will generate a certain behavior. Here we will use Expectation-Maximization to find a maximum likelihood estimate of the parameters of the evaluation function, treating the actual steps taken in planning each action as unobserved data.
Concept of a Data Thread Based Parking Space Occupancy Prediction in a Berlin Pilot Region
Tiedemann, Tim (German Research Center for Artificial Intelligence (DFKI)) | Voegele, Thomas (German Research Center for Artificial Intelligence (DFKI)) | Krell, Mario Michael (University of Bremen) | Metzen, Jan Hendrik (University of Bremen) | Kirchner, Frank (German Research Center for Artificial Intelligence (DFKI) and University of Bremen)
In the presented research project, a software and hardware infrastructure for parking space focussed inter-modal route planning in a public pilot region in Berlin is developed. One central topic is the development of a prediction system which gives an estimated occupancy for the parking spaces in the pilot region for a given date and time in the future. Occupancy data will be collected online by roadside parking sensors developed within the project. The occupancy prediction will be implemented using “Neural Gas” machine learning in combination with a proposed method which uses data threads to improve the prediction quality. In this paper, a short overview of the whole research project is given. Furthermore, the concept of the software framework and the learning methods are presented and first collected data is shown. The prediction method using data threads is explained in more detail.
AutoFolio: Algorithm Configuration for Algorithm Selection
Lindauer, Marius (University of Freiburg) | Hoos, Holger H. (University of British Columbia) | Hutter, Frank (University of Freiburg) | Schaub, Torsten (University of Potsdam)
Algorithm selection (AS) techniques — which involve choosing from a set of algorithms the one expected to solve a given problem instance most efficiently — have substantially improved the state-of-the-art in solving many prominent AI problems, such as SAT, CSP, ASP, MAXSAT, and QBF.Although several AS procedures have been introduced,not too surprisingly, none of them dominates all others across all AS scenarios.Furthermore, these procedures have parameters whose optimal values vary across AS scenarios.This holds specifically for the machine learning techniques that form the core of current AS proceduresand for their hyperparameters. Therefore, to successfully apply AS to new problems, algorithms and benchmark sets, two questions need to be answered:(i) how to select an AS approach and (ii) how to set its parameters effectively.We address both of these problems simultaneously by using automated algorithm configuration.Specifically, we demonstrate that we can use algorithm configurators to automatically configure clasp folio 2,which implements a large variety of different AS approaches and their respective parameters in a single highly parameterized algorithm framework.We demonstrate that this approach, dubbed auto folio, can significantly improve the performance of clasp folio 2 on 11 out of the 12 scenarios from the Algorithm Selection Library and leads to new state-of-the-art algorithm selectors for 8 of these scenarios.
Lower Dimensional Representations of City Neighbourhoods
Saeidi, Marzieh (University College London) | Riedel, Sebastian (University College London) | Capra, Licia (University College London)
We aim to profile characteristics of areas of variant units across a district, city or a country. Studying attributes of areas can be very useful in several situations. In the past, research has focused mainly on studying specific char- acteristics of areas using a few selected attributes. In this paper we propose an alternative view on neighbourhood profiles. Instead of characterising a neighbourhood through a set of attributes such as those collected by the census, we propose use of a low-dimensional fea- ture representation, or embedding, created from one or more input sources. The purpose of the embeddings is having a generic representation for entities that can do well across several downstream tasks such as regression for attributes prediction.
Pricing Procedure in Accordance with Characteristic of Parking Utilization - Analysis Example of Massive Parking Accounting Data
Enoki, Yuichi (Nagoya Institute of Technology) | Kanamori, Ryo (Nagoya Institute of Technology) | Ito, Takayuki (Nagoya Institute of Technology)
In most urban area, traffic issue related to parking (e.g. economic(time) and environmental loss in finding a parking space) has been significant, and parking management strategies to set optimal price are often necessary for the parking agencies. In order to revise parking fee appropriately without a reduction of parking demand, a pricing procedure in accordance with characteristic of parking utilization is expected. On the other hand, a large amount of parking data is accumulated automatically with introduction of online parking systems. In this study, we analyze massive parking accounting data, whose data size is22.5 million accounting data in the past year about 1,050 parking lots,and discuss the characteristics of parking utilization. Moreover parking duration model is developed from the accounting data for each cluster to estimate the parking demand (i.e., parking time) after changing price. As an example of appropriate price procedure, we evaluate the setting of an upper limitation of parking charge with parking demand patterns calculated from the accounting data and the parking duration model.
Sparse Approximation of a Kernel Mean
Kernel means are frequently used to represent probability distributions in machine learning problems. In particular, the well known kernel density estimator and the kernel mean embedding both have the form of a kernel mean. Unfortunately, kernel means are faced with scalability issues. A single point evaluation of the kernel density estimator, for example, requires a computation time linear in the training sample size. To address this challenge, we present a method to efficiently construct a sparse approximation of a kernel mean. We do so by first establishing an incoherence-based bound on the approximation error, and then noticing that, for the case of radial kernels, the bound can be minimized by solving the $k$-center problem. The outcome is a linear time construction of a sparse kernel mean, which also lends itself naturally to an automatic sparsity selection scheme. We show the computational gains of our method by looking at three problems involving kernel means: Euclidean embedding of distributions, class proportion estimation, and clustering using the mean-shift algorithm.