A Bayesian Clearing Mechanism for Combinatorial Auctions

We cast the problem of combinatorial auction design in a Bayesian framework in order to incorporate prior information into the auction process and minimize the number of rounds to convergence. We first develop a generative model of agent valuations and market prices such that clearing prices become maximum a posteriori estimates given observed agent valuations. This generative model then forms the basis of an auction process which alternates between refining estimates of agent valuations and computing candidate clearing prices. We provide an implementation of the auction using assumed density filtering to estimate valuations and expectation maximization to compute prices. An empirical evaluation over a range of valuation domains demonstrates that our Bayesian auction mechanism is highly competitive against the combinatorial clock auction in terms of rounds to convergence, even under the most favorable choices of price increment for this baseline.Comment: 9 pages, 4 figures, AAAI-1

Rate of Price Discovery in Iterative Combinatorial Auctions

We study a class of iterative combinatorial auctions which can be viewed as subgradient descent methods for the problem of pricing bundles to balance supply and demand. We provide concrete convergence rates for auctions in this class, bounding the number of auction rounds needed to reach clearing prices. Our analysis allows for a variety of pricing schemes, including item, bundle, and polynomial pricing, and the respective convergence rates confirm that more expressive pricing schemes come at the cost of slower convergence. We consider two models of bidder behavior. In the first model, bidders behave stochastically according to a random utility model, which includes standard best-response bidding as a special case. In the second model, bidders behave arbitrarily (even adversarially), and meaningful convergence relies on properly designed activity rules

Fast Iterative Combinatorial Auctions via Bayesian Learning

Iterative combinatorial auctions (CAs) are often used in multi-billion dollar domains like spectrum auctions, and speed of convergence is one of the crucial factors behind the choice of a specific design for practical applications. To achieve fast convergence, current CAs require careful tuning of the price update rule to balance convergence speed and allocative efficiency. Brero and Lahaie (2018) recently introduced a Bayesian iterative auction design for settings with single-minded bidders. The Bayesian approach allowed them to incorporate prior knowledge into the price update algorithm, reducing the number of rounds to convergence with minimal parameter tuning. In this paper, we generalize their work to settings with no restrictions on bidder valuations. We introduce a new Bayesian CA design for this general setting which uses Monte Carlo Expectation Maximization to update prices at each round of the auction. We evaluate our approach via simulations on CATS instances. Our results show that our Bayesian CA outperforms even a highly optimized benchmark in terms of clearing percentage and convergence speed.Comment: 9 pages, 2 figures, AAAI-1

Entre géographie et littérature : La question du lieu et de la mimèsis

Comment la littérature parvient-elle à exprimer l’expérience d’un lieu, à la créer ou à la reproduire, à représenter le lieu ou encore à le faire surgir des profondeurs de l’imaginaire ? Tout indique – et les géographes le reconnaissent – que la littérature dispose d’un arsenal de procédés détournés, de fausses allusions, de non-dits, de mentions et autres mensonges, tous susceptibles de créer un espace diégétique. Or, en dépit du fait qu’ils procéderaient d’une même volonté de saisie du réel, d’un comparable élan vers la représentation, peut-on confondre tous les langages artistiques ? Si narration et description se côtoient lorsqu’il s’agit de représenter le lieu dans une oeuvre littéraire, le point de vue adopté n’est pas non plus à négliger. À cet effet, peut-être faut-il revoir notre façon de concevoir la représentation, de manière à préciser davantage le rôle joué par le médium et le genre littéraire choisis dans l’appropriation et la restitution du lieu, et ce faisant, de mieux cerner l’apport du créateur dans la représentation de l’espace.How does literature create or recreate a sense of place? Indeed, how do imaginary worlds emerge from the mind? We all know – and geographers agree – that literature adopts all kinds of means to this end: veiled references, innuendo, falsehoods, use of place names (real or imagined), elliptical passages and so forth – in fact, anything that allows the narrator to create a diegetic environment. At the same time, is it not true that, as an instrument to express reality and give voice to the creative urge driving all those using the medium of literature, literary language changes according to the genre chosen to convey that reality? While the interplay of narration and description is fundamental to the evocation of place in literature, it does not obviate the importance of the point of view adopted. This would suggest that we should reconsider the role of the medium chosen – the literary genres employed – in its capacity to represent place. An approach of this kind could lead to a better understanding and recognition of the particular contribution of the writer to the complex issue of how a sense of place is created in literature

Blameworthiness and dangerousness: An analysis of violent female capital offenders in the United States and China

The United States and China represent two of the leading nations that retain the death penalty in both law and practice. Research suggests that judges’ sentencing decisions are based primarily on two factors, blameworthiness and dangerousness. Studies involving gender and sentencing in capital punishment cases tend to provide inconsistent findings. The current study uses case narratives to examine the direct and conjunctive effects of various factors on the sentencing decisions of violent female capital offenders in the United States and China. The findings suggest that the concepts of blameworthiness and dangerousness are distinctly defined in the United States and China. The study proposes that the differences observed in the capital offense sentencing practices of these two countries can be attributed to the distinct political, legal and social systems of the United States and China

Flexible Dieting and Metabolic Adaptation During Weight Loss: A Comprehensive Review

Flexible dieting is a ubiquitous method of eating among the fitness population. It is not a diet, but rather a nutritional concept that refutes any diet that promotes cutting out entire foods or food groups as a method to lose weight. It is a structured and science-based method of eating that involves tracking calories through monitoring the three main macronutrients: carbohydrates, fats, and proteins. These macronutrients are individualized and adjusted for muscle growth, fat loss, or weight maintenance in order to optimize intake to facilitate the manipulation of body composition. Flexible dieting is a disciplined method of eating that teaches individuals how to modify macronutrient intake in order to reach personalized physique, fitness, and health goals. The goal of incorporating flexible dieting is to empower individuals in their fitness journey to gain control over their goals through utilizing a knowledge base of nutrients and how the body responds to them. The purpose of this research is to create a comprehensive resource that targets a beginning, intermediate, or advanced fitness population who aim to learn about an evidence-based and sustainable method for achieving a healthier physique. A secondary purpose of this research project is to acquire knowledge on the metabolic adaptation that occurs during weight loss. Metabolic adaptation is a phrase often used among the fitness community as a way to describe the fluctuations in metabolism that occur during a caloric deficit. Metabolic changes that take place during weight loss favor decreased energy expenditure resulting in the down-regulation of metabolic rate. Metabolic rate is summarized by total daily energy expenditure, which has several components that collectively influence the amount of calories that an individual burns in a day. During a caloric deficit that is required for weight loss, a number of mechanisms are manipulated that function to reduce the effects of weight loss by promoting metabolic adaptation. The research included in this project is designed to learn about the mechanisms that characterize metabolic adaptation