Alex Rogers

Putting the 'smarts' into the smart grid: a grand challenge for artificial intelligence

A research agenda for making the smart grid a reality.

Theoretical Aspects of Evolutionary Computing

I: Tutorials.- to Evolutionary Computing in Design Search and Optimisation.- Evolutionary Algorithms and Constraint Satisfaction: Definitions, Survey, Methodology, and Research Directions.- The Dynamical Systems Model of the Simple Genetic Algorithm.- Modelling Genetic Algorithm Dynamics.- Statistical Mechanics Theory of Genetic Algorithms.- Theory of Evolution Strategies - A Tutorial.- Evolutionary Algorithms: From Recombination to Search Distributions.- Properties of Fitness Functions and Search Landscapes.- II: Technical Papers.- A Solvable Model of a Hard Optimisation Problem.- Bimodal Performance Profile of Evolutionary Search and the Effects of Crossover.- Evolution Strategies in Noisy Environments - A Survey of Existing Work.- Cyclic Attractors and Quasispecies Adaptability.- Genetic Algorithms in Time-Dependent Environments.- Statistical Machine Learning and Combinatorial Optimization.- Multi-Parent Scanning Crossover and Genetic Drift.- Harmonic Recombination for Evolutionary Computation.- How to Detect all Maxima of a Function.- On Classifications of Fitness Functions.- Genetic Search on Highly Symmetric Solution Spaces: Preliminary Results.- Structure Optimization and Isomorphisms.- Detecting Spin-Flip Symmetry in Optimization Problems.- Asymptotic Results for Genetic Algorithms with Applications to Nonlinear Estimation.

NILMTK: an open source toolkit for non-intrusive load monitoring

Non-intrusive load monitoring, or energy disaggregation, aims to separate household energy consumption data collected from a single point of measurement into appliance-level consumption data. In recent years, the field has rapidly expanded due to increased interest as national deployments of smart meters have begun in many countries. However, empirically comparing disaggregation algorithms is currently virtually impossible. This is due to the different data sets used, the lack of reference implementations of these algorithms and the variety of accuracy metrics employed. To address this challenge, we present the Non-intrusive Load Monitoring Toolkit (NILMTK); an open source toolkit designed specifically to enable the comparison of energy disaggregation algorithms in a reproducible manner. This work is the first research to compare multiple disaggregation approaches across multiple publicly available data sets. Our toolkit includes parsers for a range of existing data sets, a collection of preprocessing algorithms, a set of statistics for describing data sets, two reference benchmark disaggregation algorithms and a suite of accuracy metrics. We demonstrate the range of reproducible analyses which are made possible by our toolkit, including the analysis of six publicly available data sets and the evaluation of both benchmark disaggregation algorithms across such data sets.

Towards Real-Time Information Processing of Sensor Network Data Using Computationally Efficient Multi-output Gaussian Processes

In this paper, we describe a novel, computationally efficient algorithm that facilitates the autonomous acquisition of readings from sensor networks (deciding when and which sensor to acquire readings from at any time), and which can, with minimal domain knowledge, perform a range of information processing tasks including modelling the accuracy of the sensor readings, predicting the value of missing sensor readings, and predicting how the monitored environmental variables will evolve into the future. Our motivating scenario is the need to provide situational awareness support to first responders at the scene of a large scale incident, and to this end, we describe a novel iterative formulation of a multi-output Gaussian process that can build and exploit a probabilistic model of the environmental variables being measured (including the correlations and delays that exist between them). We validate our approach using data collected from a network of weather sensors located on the south coast of England.

Genetic drift in genetic algorithm selection schemes

A method for calculating genetic drift in terms of changing population fitness variance is presented. The method allows for an easy comparison of different selection schemes and exact analytical results are derived for traditional generational selection, steady-state selection with varying generation gap, a simple model of Eshelmans CHC algorithm (1991), and (/spl mu/+/spl lambda/) evolution strategies. The effects of changing genetic drift on the convergence of a GA are demonstrated empirically.

Self-organized routing for wireless microsensor networks

In this paper, we develop an energy-aware self-organized routing algorithm for the networking of simple battery-powered wireless microsensors (as found, for example, in security or environmental monitoring applications). In these networks, the battery life of individual sensors is typically limited by the power required to transmit their data to a receiver or sink. Thus, effective network-routing algorithms allow us to reduce this power and extend both the lifetime and the coverage of the sensor network as a whole. However, implementing such routing algorithms with a centralized controller is undesirable due to the physical distribution of the sensors, their limited localization ability, and the dynamic nature of such networks (given that sensors may fail, move, or be added at any time and the communication links between sensors are subject to noise and interference). Against this background, we present a distributed mechanism that enables individual sensors to follow locally selfish strategies, which, in turn, result in the self-organization of a routing network with desirable global properties. We show that our mechanism performs close to the optimal solution (as computed by a centralized optimizer), it deals adaptively with changing sensor numbers and topology, and it extends the useful life of the network by a factor of three over the traditional approach.

Designing a successful trading agent for supply chain management

This paper describes the design and evaluation of Southampton-SCM, the runner-up in the 2005 International Trading Agent Supply Chain Management Competition (TAC SCM). In particular, we focus on the way in which our agent purchases components using a mixed procurement strategy (combining long and short term planning) and how it sets its prices according to the prevailing market situation and its own inventory level (because this adaptivity and flexibility are key to its success). We analyse our buying and selling strategies in the actual competition and in controlled experiments. Through this evaluation, we show that SouthamptonSCM performs well across a broad range of environments.

An efficient and versatile approach to trust and reputation using hierarchical Bayesian modelling

In many dynamic open systems, autonomous agents must interact with one another to achieve their goals. Such agents may be self-interested and, when trusted to perform an action, may betray that trust by not performing the action as required. Due to the scale and dynamism of these systems, agents will often need to interact with other agents with which they have little or no past experience. Each agent must therefore be capable of assessing and identifying reliable interaction partners, even if it has no personal experience with them. To this end, we present HABIT, a Hierarchical And Bayesian Inferred Trust model for assessing how much an agent should trust its peers based on direct and third party information. This model is robust in environments in which third party information is malicious, noisy, or otherwise inaccurate. Although existing approaches claim to achieve this, most rely on heuristics with little theoretical foundation. In contrast, HABIT is based exclusively on principled statistical techniques: it can cope with multiple discrete or continuous aspects of trustee behaviour; it does not restrict agents to using a single shared representation of behaviour; it can improve assessment by using any observed correlation between the behaviour of similar trustees or information sources; and it provides a pragmatic solution to the whitewasher problem (in which unreliable agents assume a new identity to avoid bad reputation). In this paper, we describe the theoretical aspects of HABIT, and present experimental results that demonstrate its ability to predict agent behaviour in both a simulated environment, and one based on data from a real-world webserver domain. In particular, these experiments show that HABIT can predict trustee performance based on multiple representations of behaviour, and is up to twice as accurate as BLADE, an existing state-of-the-art trust model that is both statistically principled and has been previously shown to outperform a number of other probabilistic trust models.

Decentralized control of adaptive sampling in wireless sensor networks

The efficient allocation of the limited energy resources of a wireless sensor network in a way that maximizes the information value of the data collected is a significant research challenge. Within this context, this article concentrates on adaptive sampling as a means of focusing a sensors energy consumption on obtaining the most important data. Specifically, we develop a principled information metric based upon Fisher information and Gaussian process regression that allows the information content of a sensors observations to be expressed. We then use this metric to derive three novel decentralized control algorithms for information-based adaptive sampling which represent a trade-off in computational cost and optimality. These algorithms are evaluated in the context of a deployed sensor network in the domain of flood monitoring. The most computationally efficient of the three is shown to increase the value of information gathered by approximately 83%, 27%, and 8% per day compared to benchmarks that sample in a naïve nonadaptive manner, in a uniform nonadaptive manner, and using a state-of-the-art adaptive sampling heuristic (USAC) correspondingly. Moreover, our algorithm collects information whose total value is approximately 75% of the optimal solution (which requires an exponential, and thus impractical, amount of time to compute).

Human-agent collectives

HACs offer a new science for exploring the computational and human aspects of society.