Open-ended Learning in Symmetric Zero-sum Games

Zero-sum games such as chess and poker are, abstractly, functions that evaluate pairs of agents, for example labeling them `winner' and `loser'. If the game is approximately transitive, then self-play generates sequences of agents of increasing strength. However, nontransitive games, such as rock-paper-scissors, can exhibit strategic cycles, and there is no longer a clear objective -- we want agents to increase in strength, but against whom is unclear. In this paper, we introduce a geometric framework for formulating agent objectives in zero-sum games, in order to construct adaptive sequences of objectives that yield open-ended learning. The framework allows us to reason about population performance in nontransitive games, and enables the development of a new algorithm (rectified Nash response, PSRO_rN) that uses game-theoretic niching to construct diverse populations of effective agents, producing a stronger set of agents than existing algorithms. We apply PSRO_rN to two highly nontransitive resource allocation games and find that PSRO_rN consistently outperforms the existing alternatives.Comment: ICML 2019, final versio

Geometry of Information Integration

Information geometry is used to quantify the amount of information integration within multiple terminals of a causal dynamical system. Integrated information quantifies how much information is lost when a system is split into parts and information transmission between the parts is removed. Multiple measures have been proposed as a measure of integrated information. Here, we analyze four of the previously proposed measures and elucidate their relations from a viewpoint of information geometry. Two of them use dually flat manifolds and the other two use curved manifolds to define a split model. We show that there are hierarchical structures among the measures. We provide explicit expressions of these measures

CFD analysis of the fuel-air mixture formation process in passive prechambers for use in a high-pressure direct injection (HPDI) Two-stroke engine

The research on two-stroke engines has been focused lately on the development of direct injection systems for reducing the emissions of hydrocarbons by minimizing the fuel shortcircuiting. Low temperature combustion (LTC) may be the next step to further improve emissions and fuel consumption; however, LTC requires unconventional ignition systems. Jet ignition, i.e., the use of prechambers to accelerate the combustion process, turned out to be an effective way to perform LTC. The present work aims at proving the feasibility of adopting passive prechambers in a high-pressure, direct injection, two-stroke engine through non-reactive computational fluid dynamics analyses. The goal of the analysis is the evaluation of the prechamber performance in terms of both scavenging efficiency of burnt gases and fuel/air mixture formation inside the prechamber volume itself, in order to guarantee the mixture ignitability. Two prechamber geometries, featuring different aspect ratios and orifice numbers, were investigated. The analyses were replicated for two different locations of the injection and for three operating conditions of the engine in terms of revolution speed and load. Upon examination of the results, the effectiveness of both prechambers was found to be strongly dependent on the injection setup

Retrospective Cohort Study on Acute Care in Obstetrics and Gynecology. Analogies and Differences When Compared to Emergency Medicine

Introduction: the demand for urgent obstetric and gynecology care has progressively increased: in the United States approximately 1.4 million gynecologic visits are made to the emergency department (ED) annually, while almost 75% of women make at least 1 unscheduled visit during pregnancy. Moreover, research has recently focused on setting standards in unscheduled care, and developing quality indicators to improve patients’ health. Therefore, we investigated the characteristics of women with acute gynecological or pregnancy complaints using quality indicators developed for emergency medicine, to better define the needs of this population and improve care. Methods: Retrospective cohort study on ED, and Obstetrics and Gynecology (ObGyn) triage visits, at a tertiary care hospital in Italy, during 2012. Data were analyzed with population-averaged logistic regression and Poisson regression. Results: When compared to the 33,557 ED visits, the 9245 ObGyntriage referrals were more frequently associated with pregnancy (≤12 weeks’ gestation, OR: 30.7, 95%CI; 24.5 - 38.4; >12 weeks’ gestation, OR 81.2, 95%CI; 64.8 - 101.4), vaginal bleeding (OR 156.6, 95%CI; 82.7 - 294.4), diurnal (night access OR 0.87, 95% CI; 0.78 - 0.96) and weekday access (holiday access OR 0.87, 95%CI; 0.78 - 0.95), frequent users (recurrent ED visits IRR 0.87, 95%CI; 0.83 - 0.9) and lower hospital admissions (ED admission OR 1.6, 95%CI; 1.4 - 1.8). Conclusion: ObGyn triage patients differed from ED users, and were at higher risk of “crowding”. Such diversities should be considered to improve female healthcare services and allocate resources more efficiently

On the influence of virtual camber effect on airfoil polars for use in simulations of Darrieus wind turbines

Darrieus vertical-axis wind turbines are experiencing renewed interest from researchers and manufacturers, though their efficiencies still lag those of horizontal-axis wind turbines. A better understanding of their aerodynamics is required to improve on designs, for example through the development of more accurate low-order (e.g. blade element momentum) models. Many of these models neglect the impact of the curved paths that are followed by blades on their performance. It has been theorized that the curved streamlines of the flow impart a virtual camber and incidence on them, giving a performance analogous to a cambered blade in a rectilinear flow. To test the extent of this effect, wind tunnel experiments have been conducted in a rectilinear flow to obtain lift and drag for three airfoils: a NACA 0018 and two conformal transforms of the profile. The transformed airfoils exhibit the virtual camber that the theory predicts is imparted to a NACA 0018 when used in a Darrieus turbine with blade chord-to-turbine radius ratios, c/R, of 0.114 and 0.25. A parallel computational fluid dynamics campaign has been conducted to study the aerodynamic behavior of the same blades in curvilinear flow in Darrieus-like motion with c/R = 0.114 and 0.25, at tip-speed ratios of 2.1 and 3.1, using novel techniques to obtain blade effective angles of attack. The analysis confirms that the theory holds, with the wind tunnel results for the NACA 0018 being analogous to numerical results for the relevant cambered airfoils. In addition, turbine performance is calculated using computational fluid dynamics and a blade element momentum code, for each of the blades in turn. The computational fluid dynamics results for the NACA 0018 agree closely to blade element momentum results for the equivalent cambered airfoil where c/R = 0.25, for both turbine power and blade tangential forces. Agreement between the two methods using geometrically identical blades is poor at both the blade and turbine level for c/R = 0.25. It is concluded that when modeling a Darrieus rotor using blade element momentum methods, applying experimental data for the profile used in the turbine will yield inaccurate results if the c/R ratio is high, in such cases it is necessary to select a profile based on the virtual shape of the blades

A phase II study of primary dose-dense sequential doxorubicin plus cyclophosphamide and docetaxel in cT4 breast cancer

Background: Dose-dense chemotherapy with anthracyclines and taxanes has improved either disease free survival or overall survival in high risk patients with early breast cancer. Patients and Methods: The activity and safety of a dose-dense schedule (q14 days) of adriamycin 60 mg/sqm and cyclophosphamide 600 mg/sqm (AC) x 4 cycles followed by docetaxel 75 mg/sqm for 4 cycles with hematopoietic support in patients with stage IIIB breast cancer was explored. Patients with ER >= 10% tumors received concomitant endocrine therapy with 3-month triptorelin and letrozole. Results: Fifteen patients with histologically proven cT4b (three patients) and cT4d (twelve patients) MO breast cancer were enrolled. Median age was 48 years (range 25-66). Eight clinical responses including one pathological complete remission (pCR), three stable disease (including minor responses) and four progression of disease, one during AC and three during taxotere, were observed. Four patients had grade 3-4 non hematological toxicities and all except one discontinued treatment. Conclusion: Due to the high rate of progressive disease, this schedule should not represent a standard option in cT4 breast cancer

Smooth markets: A basic mechanism for organizing gradient-based learners

With the success of modern machine learning, it is becoming increasingly important to understand and control how learning algorithms interact. Unfortunately, negative results from game theory show there is little hope of understanding or controlling general n-player games. We therefore introduce smooth markets (SM-games), a class of n-player games with pairwise zero sum interactions. SM-games codify a common design pattern in machine learning that includes (some) GANs, adversarial training, and other recent algorithms. We show that SM-games are amenable to analysis and optimization using first-order methods.Comment: 18 pages, 3 figure

Le contrôle de l’érosion dans les systèmes barrière-lagune: le champ dunaire de Capo Comino (Sardaigne nord-orientale, Italie) = The erosion of the barrier system of Capo Comino (North-East Sardinia, Italy)

The study of the delicate balances of the coasts has a crescent interest in the scientific and administrative communities because of the role of the coastal systems in the economic development. Indeed, during the 70s the littoral zone underwent to the strong urban development and tourist industry. Now the main need is to find an equilibrium between the necessities of the protection of the coastal environment and the human needs (ICZM Protocols), following the target of the preservation of the beaches and the coastal systems. The coast of Capo Comino, located in the north-eastern coast of Sardinia and partially included into a Zone of Community Interest ( SIC-ITB020012), is not influenced by human impact. The analysis of aerial photos allowed the study of the evolution of the coastline, the dune field and its vegetation between 1954 and the 2006. The field monitoring of the dunes (2003-2011) was also made by transects, in order to evaluate the morpho-sedimentological and vegetation dynamic of this sector. The data presented in this paper allow to understand that the erosion of the area is not strong and the regradation of the coastline is about 10-15 meters in the northern sector and 40 meters in the central one. The migration of the dunes, instead, is very important, with the mouvement of huge volumes of sand. The number and areas of the blowouts has increased too.L\u2019\ue9tude des \ue9quilibres d\ue9licats des syst\ue8mes littoraux connait un int\ue9r\ueat croissant dans les communaut\ue9s sci\ue9ntifiques et administratives pour l\u2019importance que les syst\ue8mes c\uf4tiers ont dans le d\ue9veloppement \ue9conomique des r\ue9gions littorales. En effet, la bande c\uf4ti\ue8re a \ue9t\ue9 tr\ue8s int\ue9ress\ue9e par le d\ue9veloppement urbanistique et l'industrie touristique qui doivent maintenant trouver un point d'\ue9quilibre (ICZM Protocols) avec les n\ue9cessit\ue9s de protection de ce milieu fragile, tant pour le patrimoine naturel que pour la conservation des plages face \ue0 l\u2019\ue9rosion. Le littoral de Capo Comino, situ\ue9 sur la c\uf4te nord-orientale de la Sardaigne et partiellement ins\ue9r\ue9 dans une Zone d'Int\ue9r\ueat Communautaire (SIC-ITB020012), est encore peu soumis aux pressions anthropiques. L\u2019analyse des photos a\ue9riennes a permis l'\ue9tude de l'\ue9volution de la ligne de rivage, des champs dunaires et de la v\ue9g\ue9tation entre 1954 et 2006. Le suivi du champ dunaire (2003-2011) a \ue9t\ue9 effectu\ue9 par des transects, de fa\ue7on \ue0 pouvoir analyser l'\ue9volution morpho-s\ue9dimentaire et v\ue9g\ue9tale du secteur. Les donn\ue9es pr\ue9sent\ue9es dans ce travail ont permis de relever que l\u2019\ue9rosion du littoral est tr\ue8s r\ue9duite : le recul de la ligne de rivage a atteint 10-15 m\ue8tres dans le secteur septentrional et environ 40 m\ue8tres dans une petite portion du secteur central. On a surtout relev\ue9 une augmentation des zones de d\ue9flation et des blowouts, avec une migration importante des volumes de sable le long de la direction principale de transport et la formation de nombreuses zones d\u2019\ue9rosion \ue9olienne