Accelerated Convergence for Counterfactual Learning to Rank

Counterfactual Learning to Rank (LTR) algorithms learn a ranking model from logged user interactions, often collected using a production system. Employing such an offline learning approach has many benefits compared to an online one, but it is challenging as user feedback often contains high levels of bias. Unbiased LTR uses Inverse Propensity Scoring (IPS) to enable unbiased learning from logged user interactions. One of the major difficulties in applying Stochastic Gradient Descent (SGD) approaches to counterfactual learning problems is the large variance introduced by the propensity weights. In this paper we show that the convergence rate of SGD approaches with IPS-weighted gradients suffers from the large variance introduced by the IPS weights: convergence is slow, especially when there are large IPS weights. To overcome this limitation, we propose a novel learning algorithm, called CounterSample, that has provably better convergence than standard IPS-weighted gradient descent methods. We prove that CounterSample converges faster and complement our theoretical findings with empirical results by performing extensive experimentation in a number of biased LTR scenarios -- across optimizers, batch sizes, and different degrees of position bias.Comment: SIGIR 2020 full conference pape

Studies of multiple stellar systems - IV. The triple-lined spectroscopic system Gliese 644

We present a radial-velocity study of the triple-lined system Gliese 644 and derive spectroscopic elements for the inner and outer orbits with periods of 2.9655 and 627 days. We also utilize old visual data, as well as modern speckle and adaptive optics observations, to derive a new astrometric solution for the outer orbit. These two orbits together allow us to derive masses for each of the three components in the system: M_A = 0.410 +/- 0.028 (6.9%), M_Ba = 0.336 +/- 0.016 (4.7%), and $M_Bb = 0.304 +/- 0.014 (4.7%) M_solar. We suggest that the relative inclination of the two orbits is very small. Our individual masses and spectroscopic light ratios for the three M stars in the Gliese 644 system provide three points for the mass-luminosity relation near the bottom of the Main Sequence, where the relation is poorly determined. These three points agree well with theoretical models for solar metallicity and an age of 5 Gyr. Our radial velocities for Gliese 643 and vB 8, two common-proper-motion companions of Gliese 644, support the interpretation that all five M stars are moving together in a physically bound group. We discuss possible scenarios for the formation and evolution of this configuration, such as the formation of all five stars in a sequence of fragmentation events leading directly to the hierarchical configuration now observed, versus formation in a small N cluster with subsequent dynamical evolution into the present hierarchical configuration.Comment: 17 pages, 9 figures, Accepted for publication in MNRA

Retinal metric: a stimulus distance measure derived from population neural responses

The ability of the organism to distinguish between various stimuli is limited by the structure and noise in the population code of its sensory neurons. Here we infer a distance measure on the stimulus space directly from the recorded activity of 100 neurons in the salamander retina. In contrast to previously used measures of stimulus similarity, this "neural metric" tells us how distinguishable a pair of stimulus clips is to the retina, given the noise in the neural population response. We show that the retinal distance strongly deviates from Euclidean, or any static metric, yet has a simple structure: we identify the stimulus features that the neural population is jointly sensitive to, and show the SVM-like kernel function relating the stimulus and neural response spaces. We show that the non-Euclidean nature of the retinal distance has important consequences for neural decoding.Comment: 5 pages, 4 figures, to appear in Phys Rev Let

Relative quantum cohomology of the Chiang Lagrangian

We compute the open Gromov-Witten disk invariants and the relative quantum cohomology of the Chiang Lagrangian $L_\triangle \subset \mathbb{C}P^3$. Since $L_\triangle$ is not fixed by any anti-symplectic involution, the invariants may augment straightforward $J$-holomorphic disk counts with correction terms arising from the formalism of Fukaya $A_\infty$-algebras and bounding cochains. These correction terms are shown in fact to be non-trivial for many invariants. Moreover, examples of non-vanishing mixed disk and sphere invariants are obtained. We characterize a class of open Gromov-Witten invariants, called basic, which coincide with straightforward counts of $J$-holomorphic disks. Basic invariants for the Chiang Lagrangian are computed using the theory of axial disks developed by Evans-Lekili and Smith in the context of Floer cohomology. The open WDVV equations give recursive relations which determine all invariants from the basic ones. The denominators of all invariants are observed to be powers of $2$ indicating a non-trivial arithmetic structure of the open WDVV equations. The magnitude of invariants is not monotonically increasing with degree. Periodic behavior is observed with periods $8$ and $16.$Comment: 60 pages, 5 figures; corrected minor errors, added references and expanded introductio

Quadricuspid Aortic Valve Defined by Echocardiography and Cardiac Computed Tomography

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THE MANTECA YELLOW BEAN: A GENETIC RESOURCE OF FAST COOKING AND HIGH IRON BIOAVAILABILITY PHENOTYPES FOR THE NEXT GENERATION OF DRY BEANS (\u3ci\u3ePhaseolus vulgaris\u3c/i\u3e L.)

Dry beans (Phaseolus vulgaris L.) are a nutrient dense food produced globally as a major pulse crop for direct human consumption. Despite being rich in protein and micronutrients, long cooking times limit the use of dry beans worldwide, especially in regions relying on wood and charcoal as the primary sources of fuel for cooking, such as Sub-Sahara Africa and the Caribbean. Coincidently, these same regions also have high densities of women and children at risk for micronutrient deficiencies [1]. There is need for a fast cooking bean, which can positively impact consumers by reducing fuel cost and preparation time, while simultaneously complementing the nutritional quality of house-hold based meals [2]. To help accelerate a reliable increase in dry bean production for Sub-Saharan Africa, the Andean Bean Diversity Panel (ADP; http://arsftfbean.uprm.edu/bean/) was assembled as a genetic resource in the development of fast cooking, nutritional improved, biotic/abiotic resistant varieties. A germplasm screening for atmospheric cooking time (100oC) of over 200 bean accessions from the ADP identified only five fast cooking entries [3]. Two entries were white beans from Burundi (Blanco Fanesquero) and Ecuador (PI527521). Native to Chile, two of the six fast cooking entries were collected from Angola, and had a pale lemon ‘Manteca’ yellow seed color (Cebo, Mantega Blanca). Traditional knowledge from Chile suggests Manteca yellow beans are low flatulence and easy to digest [4]. Yellow beans of various shades are important in Eastern and Southern Africa. Their popularity has increased in recent years and they often fetch the highest prices at the marketplace. There is evidence to suggest that Manteca yellow beans have a unique nutritional profile when compared to other yellow seed types; with more soluble dietary fiber, less indigestible protein and starch, and are also free of condensed tannins. The hypothesis was tested that this unique composition would also have a positive influence on the bioavailability of iron in an in vitro digestion/Caco-2 cell culture bioassay