Energy Demand Prediction in a Charge Station: A Comparison of Statistical Learning Approaches

International audienceIn this article, we compare the performances of 5 learning techniques: artificial neural networks, support vector machines, ARIMA processes and regret based methods. They have been tested over real database which can be associated with the energy demand generated by electric vehicles wishing to reload, in a specific charge station. Using this generic database, our simulations highlight the fact that regret based methods clearly outperform the other learning approaches. This class of methods is all the more interesting as it enables the introduction of game theory to model the interdependences between the agents composing the ecosystem and provides economic guidelines

Energy Demand Prediction: A Partial Information Game Approach

International audienceThis article proposes an original approach to predict the electric vehicles (EVs)' energy demand in a charge station using a regret minimization learning approach. The problem is modelled as a two players game involving: on the one hand the EV drivers, whose demand is unknown and, on the other hand, the service provider who owns the charge station and wants to make the best predictions in order to minimize his regret. The information in the game is partial. Indeed, the service provider never observes the EV drivers' energy demand. The only information he has access to is contained in a feedback function which depends on his predictions accuracy and on the EV drivers' consumption level. The local/expanded accuracy and the ability for uncertainty handling of the regret minimization learning approach is evaluated by comparison with three well-known learning approaches: (i) Neural Network, (ii) Support Vector Machine, (iii) AutoRegressive Integrated Moving Average process, using as benchmarks two data bases: an artificial one generated using a bayesian network and real domestic household electricity consumption data in southern California. We observe that over real data, regret minimization algorithms clearly outperform the other learning approaches. The efficiency of these methods open the door to a wide class of game theory applications dealing with collaborative learning, information sharing and manipulation

Evolutionary approaches for the reverse-engineering of gene regulatory networks: A study on a biologically realistic dataset

<p>Abstract</p> <p>Background</p> <p>Inferring gene regulatory networks from data requires the development of algorithms devoted to structure extraction. When only static data are available, gene interactions may be modelled by a Bayesian Network (BN) that represents the presence of direct interactions from regulators to regulees by conditional probability distributions. We used enhanced evolutionary algorithms to stochastically evolve a set of candidate BN structures and found the model that best fits data without prior knowledge.</p> <p>Results</p> <p>We proposed various evolutionary strategies suitable for the task and tested our choices using simulated data drawn from a given bio-realistic network of 35 nodes, the so-called insulin network, which has been used in the literature for benchmarking. We assessed the inferred models against this reference to obtain statistical performance results. We then compared performances of evolutionary algorithms using two kinds of recombination operators that operate at different scales in the graphs. We introduced a niching strategy that reinforces diversity through the population and avoided trapping of the algorithm in one local minimum in the early steps of learning. We show the limited effect of the mutation operator when niching is applied. Finally, we compared our best evolutionary approach with various well known learning algorithms (MCMC, K2, greedy search, TPDA, MMHC) devoted to BN structure learning.</p> <p>Conclusion</p> <p>We studied the behaviour of an evolutionary approach enhanced by niching for the learning of gene regulatory networks with BN. We show that this approach outperforms classical structure learning methods in elucidating the original model. These results were obtained for the learning of a bio-realistic network and, more importantly, on various small datasets. This is a suitable approach for learning transcriptional regulatory networks from real datasets without prior knowledge.</p

Learning bayesian networks with evolutionary approaches for the reverse-engineering of gene regulatory networks

De nombreuses fonctions cellulaires sont réalisées grâce à l'interaction coordonnée de plusieurs gènes. Identifier le graphe de ces interactions, appelé réseau de régulation génétique, à partir de données d'expression de gènes est l'un des objectifs majeurs de la biologie des systèmes. Dans cette thèse, nous abordons ce problème en choisissant de modéliser les relations entre gènes par un réseau bayésien. Se pose alors la question de l'apprentissage de la structure de ce type de modèle à partir de données qui sont en général peu nombreuses. Pour résoudre ce problème, nous recherchons parmi tous les modèles possibles le modèle le plus simple, expliquant le mieux les données. Pour cela, nous introduisons et étudions différents types d'algorithmes génétiques permettant d'explorer l'espace des modèles. Nous nous intéressons plus particulièrement aux méthodes de spéciation. ces dernières, en favorisant la diversité des solutions candidates considérées, empêchent l'algorithme de converger trop rapidement vers des optima locaux. Ces algorithmes génétiques sont comparés avec différentes méthodes d'apprentissage de structure de réseaux bayésiens, classiquement utilisées dans la littérature. Nous mettons ainsi en avant la pertinence des approches evolutionnaires pour l'apprentissage de ces graphes d'interactions. Enfin, nous les comparons à une classe alternative d'algorithmes évolutionnaires qui s'avère particulièrement prometteuse : les algorithmes à estimation de distribution. Tous ces algorithmes sont testés et comparés sur un modèle du réseau de régulation de l'insuline de 35 noeuds dont nous tirons des jeux de données synthétiques de taille modeste.Inferring gene regulatory networks from data requires the development of algorithms devoted to structure extraction. When only static data are available, gene interactions may be modelled by a bayesian network that represents the presence of direct interactions from regulators to regulees by conditional probability distributions. In this work, we used enhanced evolutionary algorithms to stochastically evolve a set of candidate bayesian network structures and found the model that best fits data without prior knowledge. We proposed various evolutionary strategies suitable for the task and tested our choices using simulated data drawn from a given bio-realistic network of 35 nodes, the so-called insulin network, which has been used in the literature for benchmarking. We introduced a niching strategy that reinforces diversity through the population and avoided trapping of the algorithm in one local minimum in the early steps of learning. We compared our best evolutionary approach with various well known learning algorithms (mcmc, k2, greedy search, tpda, mmhc) devoted to bayesian network structure learning. Then, we compared our best genetic algorithm with another class of evolutionary algorithms : estimation of distribution algorithms. We show that an evolutionary approach enhanced by niching outperforms classical structure learning methods in elucidating the original model. Finally, it appears that estimation of distribution algorithms are a promising approach to extend this work. These results were obtained for the learning of a bio-realistic network and, more importantly, on various small datasets

Approches évolutionnaires pour la reconstruction de réseaux de régulation génétique par apprentissage de réseaux bayésiens.

Inferring gene regulatory networks from data requires the development of algorithms devoted to structure extraction. When only static data are available, gene interactions may be modelled by a bayesian network that represents the presence of direct interactions from regulators to regulees by conditional probability distributions. In this work, we used enhanced evolutionary algorithms to stochastically evolve a set of candidate bayesian network structures and found the model that best fits data without prior knowledge. We proposed various evolutionary strategies suitable for the task and tested our choices using simulated data drawn from a given bio-realistic network of 35 nodes, the so-called insulin network, which has been used in the literature for benchmarking. We introduced a niching strategy that reinforces diversity through the population and avoided trapping of the algorithm in one local minimum in the early steps of learning. We compared our best evolutionary approach with various well known learning algorithms (mcmc, k2, greedy search, tpda, mmhc) devoted to bayesian network structure learning. Then, we compared our best genetic algorithm with another class of evolutionary algorithms : estimation of distribution algorithms. We show that an evolutionary approach enhanced by niching outperforms classical structure learning methods in elucidating the original model. Finally, it appears that estimation of distribution algorithms are a promising approach to extend this work. These results were obtained for the learning of a bio-realistic network and, more importantly, on various small datasets.De nombreuses fonctions cellulaires sont réalisées grâce à l'interaction coordonnée de plusieurs gènes. Identifier le graphe de ces interactions, appelé réseau de régulation génétique, à partir de données d'expression de gènes est l'un des objectifs majeurs de la biologie des systèmes. Dans cette thèse, nous abordons ce problème en choisissant de modéliser les relations entre gènes par un réseau bayésien. Se pose alors la question de l'apprentissage de la structure de ce type de modèle à partir de données qui sont en général peu nombreuses. Pour résoudre ce problème, nous recherchons parmi tous les modèles possibles le modèle le plus simple, expliquant le mieux les données. Pour cela, nous introduisons et étudions différents types d'algorithmes génétiques permettant d'explorer l'espace des modèles. Nous nous intéressons plus particulièrement aux méthodes de spéciation. ces dernières, en favorisant la diversité des solutions candidates considérées, empêchent l'algorithme de converger trop rapidement vers des optima locaux. Ces algorithmes génétiques sont comparés avec différentes méthodes d'apprentissage de structure de réseaux bayésiens, classiquement utilisées dans la littérature. Nous mettons ainsi en avant la pertinence des approches evolutionnaires pour l'apprentissage de ces graphes d'interactions. Enfin, nous les comparons à une classe alternative d'algorithmes évolutionnaires qui s'avère particulièrement prometteuse : les algorithmes à estimation de distribution. Tous ces algorithmes sont testés et comparés sur un modèle du réseau de régulation de l'insuline de 35 noeuds dont nous tirons des jeux de données synthétiques de taille modeste

Approches évolutionnaires pour la reconstruction de réseaux de régulation génétique par apprentissage de réseaux bayésiens

De nombreuses fonctions cellulaires sont réalisées grâce à l'interaction coordonnée de plusieurs gènes. Identifier le graphe de ces interactions, appelé réseau de régulation génétique, à partir de données d'expression de gènes est l'un des objectifs majeurs de la biologie des systèmes. Dans cette thèse, nous abordons ce problème en choisissant de modéliser les relations entre gènes par un réseau bayésien. Se pose alors la question de l'apprentissage de la structure de ce type de modèle à partir de données qui sont en général peu nombreuses. Pour résoudre ce problème, nous recherchons parmi tous les modèles possibles le modèle le plus simple, expliquant le mieux les données. Pour cela, nous introduisons et étudions différents types d'algorithmes génétiques permettant d'explorer l'espace des modèles. Nous nous intéressons plus particulièrement aux méthodes de spéciation. ces dernières, en favorisant la diversité des solutions candidates considérées, empêchent l'algorithme de converger trop rapidement vers des optima locaux. Ces algorithmes génétiques sont comparés avec différentes méthodes d'apprentissage de structure de réseaux bayésiens, classiquement utilisées dans la littérature. Nous mettons ainsi en avant la pertinence des approches evolutionnaires pour l'apprentissage de ces graphes d'interactions. Enfin, nous les comparons à une classe alternative d'algorithmes évolutionnaires qui s'avère particulièrement prometteuse : les algorithmes à estimation de distribution. Tous ces algorithmes sont testés et comparés sur un modèle du réseau de régulation de l'insuline de 35 noeuds dont nous tirons des jeux de données synthétiques de taille modeste.Inferring gene regulatory networks from data requires the development of algorithms devoted to structure extraction. When only static data are available, gene interactions may be modelled by a bayesian network that represents the presence of direct interactions from regulators to regulees by conditional probability distributions. In this work, we used enhanced evolutionary algorithms to stochastically evolve a set of candidate bayesian network structures and found the model that best fits data without prior knowledge. We proposed various evolutionary strategies suitable for the task and tested our choices using simulated data drawn from a given bio-realistic network of 35 nodes, the so-called insulin network, which has been used in the literature for benchmarking. We introduced a niching strategy that reinforces diversity through the population and avoided trapping of the algorithm in one local minimum in the early steps of learning. We compared our best evolutionary approach with various well known learning algorithms (mcmc, k2, greedy search, tpda, mmhc) devoted to bayesian network structure learning. Then, we compared our best genetic algorithm with another class of evolutionary algorithms : estimation of distribution algorithms. We show that an evolutionary approach enhanced by niching outperforms classical structure learning methods in elucidating the original model. Finally, it appears that estimation of distribution algorithms are a promising approach to extend this work. These results were obtained for the learning of a bio-realistic network and, more importantly, on various small datasets.EVRY-Bib. électronique (912289901) / SudocSudocFranceF

Large scale EV charge scheduling under contractual power constraints: a priority rule-based semi-online algorithm

International audienceThe scope of this research work is to study the implementation of Electric Vehicles (EVs) based Virtual Power Plants (VPPs) through optimized charging process of a fleet of vehicles spread over multiple charging stations. In this context, this paper focuses on smart charge scheduling for an ensemble of EVs operated by a fleet manager. We consider a semi-online setting where precise information about EVs' arrival times, parking durations and energy needs isn't available before the EVs' connection to the charge spots ; only global statistics (computed at the fleet level) for these quantities are made available beforehand. In this context we propose, as a first step, to learn a priority function to be used in a second step to perform online scheduling for forthcoming EVs' requiring a charging service, according to a "highest priority, processing first" scheme. As we ignore most about the shape of the priority function, we propose to learn this function in an offline way as a function of charging information collected from the EV fleet and consolidated in a historical database.L'objectif des travaux présentés dans cet article est d'étudier la faisabilité d'une centrale électrique virtuelle basée sur l'optimisation des processus de (dé)charge d'une flotte de Véhicules Electriques (VE). Cet article porte plus précisément sur l'optimisation et la planification des processus de charge pour une flotte de VE. Nous nous plaçons dans un contexte semi temps réel, où les informations relatives à l'heure d'arrivée des VE, leurs temps de stationnement ou encore leurs besoin en énergie ne sont connues que lors de la connexion du VE à la borne de recharge. Avant cet instant, nous ne disposons que d'une statistique globale (calculée à l'échelle de la flotte) relative à ces quantités. Dans ce cadre, nous proposons d'abord d'apprendre une règle de priorité, et de l'utiliser ensuite pour la planification en temps réel des processus de charge des VE, en favorisant la charge des véhicules prioritaires. La règle de priorité, inconnue a priori, est modélisée en mode hors-ligne à partir de l'historique des données de charge de la flotte, agrégée par leur gestionnaire de flotte

Learning Transcriptional Regulatory Networks with Evolutionary Algorithms Enhanced with Niching

International audienceReverse engineering of gene regulatory networks is a key issue for functional genomic. Indeed, unraveling complex interactions among genes is a crucial step in order to understand their role in cellular processes. High-throughput technologies such as DNA microarrays or ChIP on chip have in principle opened the door to network inference from data. However the size of available data is still limited compared to their dimension. Machine learning methods have thus to be worked out in order to respond to this challenge. In this work we focused our attention on modeling gene regulatory networks with Bayesian networks. Bayesian networks offer a probabilistic framework for the reconstruction of biological interactions networks using data, but the structure learning problem is still a bottleneck. In this paper, we use evolutionary algorithms to stochastically evolve a set of candidate Bayesian networks structures and find the model that best explains the small number of available observational data. We propose different kinds of recombination strategies and an appropriate technique of niching that ensure diversity among candidate solutions. Tests are carried out on simulated data drawn from a biorealistic network. The effect of deterministic crowding, a niching method, is compared to mutation for different kinds of recombination strategies and is shown to improve significantly the performances. Enhanced by deterministic crowding, our evolutionary approach outperforms K2, Greedy-search and MCMC, for training sets whose size is small compared to the standard in machine learning