Locality-Adaptive Parallel Hash Joins Using Hardware Transactional Memory

Previous work [1] has claimed that the best performing implementation of in-memory hash joins is based on (radix-)partitioning of the build-side input. Indeed, despite the overhead of partitioning, the benefits from increased cache-locality and synchronization free parallelism in the build-phase outweigh the costs when the input data is randomly ordered. However, many datasets already exhibit significant spatial locality (i.e., non-randomness) due to the way data items enter the database: through periodic ETL or trickle loaded in the form of transactions. In such cases, the first benefit of partitioning — increased locality — is largely irrelevant. In this paper, we demonstrate how hardware transactional memory (HTM) can render the other benefit, freedom from synchronization, irrelevant as well. Specifically, using careful analysis and engineering, we develop an adaptive hash join implementation that outperforms parallel radix-partitioned hash joins as well as sort-merge joins on data with high spatial locality. In addition, we show how, through lightweight (less than 1% overhead) runtime monitoring of the transaction abort rate, our implementation can detect inputs with low spatial locality and dynamically fall back to radix-partitioning of the build-side input. The result is a hash join implementation that is more than 3 times faster than the state-of-the-art on high-locality data and never more than 1% slower

Diametral strong diameter two property of Banach spaces is stable under direct sums with 1-norm

We prove that the diametral strong diameter 2 property of a Banach space (meaning that, in convex combinations of relatively weakly open subsets of its unit ball, every point has an "almost diametral" point) is stable under 1-sums, i.e., the direct sum of two spaces with the diametral strong diameter 2 property equipped with the 1-norm has again this property.Comment: 4 page

Depth Prediction Without the Sensors: Leveraging Structure for Unsupervised Learning from Monocular Videos

Learning to predict scene depth from RGB inputs is a challenging task both for indoor and outdoor robot navigation. In this work we address unsupervised learning of scene depth and robot ego-motion where supervision is provided by monocular videos, as cameras are the cheapest, least restrictive and most ubiquitous sensor for robotics. Previous work in unsupervised image-to-depth learning has established strong baselines in the domain. We propose a novel approach which produces higher quality results, is able to model moving objects and is shown to transfer across data domains, e.g. from outdoors to indoor scenes. The main idea is to introduce geometric structure in the learning process, by modeling the scene and the individual objects; camera ego-motion and object motions are learned from monocular videos as input. Furthermore an online refinement method is introduced to adapt learning on the fly to unknown domains. The proposed approach outperforms all state-of-the-art approaches, including those that handle motion e.g. through learned flow. Our results are comparable in quality to the ones which used stereo as supervision and significantly improve depth prediction on scenes and datasets which contain a lot of object motion. The approach is of practical relevance, as it allows transfer across environments, by transferring models trained on data collected for robot navigation in urban scenes to indoor navigation settings. The code associated with this paper can be found at https://sites.google.com/view/struct2depth.Comment: Thirty-Third AAAI Conference on Artificial Intelligence (AAAI'19

Uncertainty of technology use in redesigning a traditional upper secondary school course into an online format: an autoethnographic study

https://www.ester.ee/record=b5373403*es

Diametraalsed diameeter-2 omadused, Daugaveti- ja Δ-punktid Banachi ruumides

Banachi ruumidel vaadeldavate geomeetriliste omaduste seas on äärmuslik ja hästi uuritud Daugaveti omadus. Sellise omadusega Banachi ruumi veidruseks on, et ühikkera iga viilu diameeter on 2 ehk tal on diameeter-2 omadus. Näiteks c_0, l_∞, C[0,1] ja L_1 [0,1] on sellised, teiselt poolt aga refleksiivsete sh Hilberti ruumide või separaablite kaasruumide nagu l_1 ühikkeras leidub kui tahes väikese diameetriga viile. Klassikaliste diameeter-2 omaduste uuringud pakuvad välja omaduste teisendeid, mida väitekirjas põhjalikult käsitletakse. Töö üheks lähtekohaks on uurimus, kus vaadeldi Banachi ruume, mille iga normiga 1 element on Δ-punkt, st mille igal ühikkera viilu elemendil leidub selles viilus peaaegu diametraalne vastaspunkt. Veidi teistsuguse tuntud geomeetrilise kirjelduse kohaselt on Banachi ruumil Daugaveti omadus, kui vabalt fikseeritud normiga 1 element x on Daugaveti-punkt, st iga selle ruumi ühikkera element on selles ruumis ligikaudu lähendatav elemendi x peaaegu diametraalsete punktide kumerate kombinatsioonidega. Väitekirjas selgitatakse välja uute diametraalsete diameeter-2 omaduste omavaheline vahekord, käsitletakse nende stabiilsust summa- ja komponentruumide vahel ja alamruumi pärandumist. Lisaks esitletakse näiteid tuntud Banachi ruumidest, kus Daugaveti- ja Δ-punktid on samad. Põhjalik ülevaade nende punktide olemasolust absoluutse normiga summaruumides näitab muuhulgas, et mõisted Daugaveti-punkt ja Δ-punkt on erinevad. Märgime lõpetuseks, et töös esineva olulise hulga tähisena on sümboli Δ-valik vähemalt osaliselt tribuut Tartu Ülikooli uuele Delta keskusele.The Daugavet property is an extreme and well researched geometric property of Banach spaces. The peculiarity of Banach spaces with such property is that every slice of the unit ball is 2, i.e. that space has the diameter 2 property. Examples of such spaces are c_0, l_∞, C[0,1] ja L_1 [0,1]. Reflexive spaces, e.g. Hilbert spaces, or separable dual spaces, e.g. l_1, however, have slices of arbitrarily small diameter. The research on the classical diameter 2 properties suggests different versions of these properties and these are thoroughly studied in this thesis. One of the starting points of the thesis is a study, that considered Banach spaces in which every element of norm 1 is a Δ-point, that is, in which every element in a slice of the unit ball has an almost diametral point in that slice. According to a slightly different geometric characterisation a Banach space has the Daugavet property if every element x of norm 1 is a Daugavet-point, that is, every element of the unit ball can be approximated in that space with convex combinations of almost diametral points of x. In the current thesis, the relations between new diametral diameter 2 properties are explained, the stability and inheritance results of these properties are investigated. In addition, examples are presented of well-known Banach spaces where Daugavet- and Δ-points are the same. A thorough study of the existence of Daugavet- and Δ-points in absolute sums affirms, among other things, that the concepts Daugavet-point and Δ-point are different. Let it be remarked, that the choice of the symbol Δ to denote an important notion in the thesis is at least a partial tribute to the new Delta Centre of University of Tartu.https://www.ester.ee/record=b536058

¿Afectó la lluvia de cenizas del complejo volcánico Puyehue-Cordón Caulle la abundancia y riqueza de hormigas en la estepa patagónica?

Las perturbaciones naturales constituyen componentes fundamentales en la dinámica de los ecosistemas. Aquellas de gran escala, como las ocasionadas por huracanes y volcanes, han sido poco estudiadas debido a su baja frecuencia, la ausencia de información de base por su baja predictibilidad, la imposibilidad de replicación y la dificultad de realizar estudios a largo plazo que evalúen la recuperación de los ecosistemas. La reciente erupción del complejo volcánico Puyehue-Cordón Caulle (junio 2011) cuya lluvia de cenizas cubrió 24 millones de hectáreas de la Patagonia, brinda una oportunidad única para estudiar este tipo de perturbación con información de base. El verano previo a la erupción se caracterizaron las comunidades de hormigas en áreas de la estepa patagónica posteriormente cubiertas por 4 cm de cenizas finas. El objetivo de este estudio es establecer si la deposición de cenizas afectó la abundancia, riqueza y composición de hormigas. Durante los veranos 2012 y 2013 se repitió el muestreo y los datos fueron comparados entre años. La abundancia tendió a ser menor después de la erupción, pero la riqueza y composición de hormigas fueron similares antes y dos temporadas posteriores a la erupción. El escaso efecto se debe principalmente al momento de la erupción, a que las hormigas son insectos sociales y al espesor de la capa de cenizas. La erupción ocurrió a fines de otoño cuando la actividad de las hormigas es reducida por las bajas temperaturas. Aun habiendo existido mortalidad de obreras durante la deposición, éstas representarían un bajo porcentaje de la colonia, garantizando su supervivencia. Solo cuatro de 13 especies cambiaron su incidencia, tres de ellas recién en la segunda temporada. Este retardo en la respuesta podría estar mediado por cambios en los recursos y el ambiente. No se descartan posibles efectos a largo plazo en las otras especies.Natural disturbances are important components of ecosystem dynamics. Large scale disturbances produced by volcanoes, have been poorly studied because of their low frequency, the lack of baseline studies due to their unpredictability, the impossibility of replication, and the difficulty of conducting long-term studies to monitor ecosystem recovery. The recent eruption of the Puyehue-Cordón Caulle volcanic complex (June 2011), which produced an ash fall covering 24 million ha of Patagonia, provides a unique opportunity of studying this type of disturbance in areas with baseline data. The summer before the ash fall (2011) ant communities were characterized in areas of the Patagonian steppe which were later covered with 4 cm of fine ash. The aim of this study is to establish if ash deposition affected ant abundance, species richness and composition. In summers 2012 and 2013, sampling was repeated and data obtained were compared among years. Total ant abundance tended to be lower after the eruption, but species richness and composition were similar before and two seasons after the ash fall. The little effects on ant community is mainly a consequence of the timing of the eruption, ants' social nature, and ash thickness. The eruption occurred at the end of the autumn when ant activity was reduced due to low temperatures. Also, the potential mortality of outside workers during the acute deposition phase does not risk colony survival since they represent a small percentage of it. Ash thickness was probably not high enough to produce severe effects. Only four out of 13 species changed their incidence after the ash fall, three of them not until the second season, showing a delayed response. This was probably a consequence of indirect effects mediated by resource and environmental changes. Long-term effects on other species cannot be discarded.Fil: Pirk, Gabriela Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio de Ecotono; Argentin

Cache Conscious Data Layouting for In-Memory Databases

Many applications with manually implemented data management exhibit a data storage pattern in which semantically related data items are stored closer in memory than unrelated data items. The strong sematic relationship between these data items commonly induces contemporary accesses to them. This is called the principle of data locality and has been recognized by hardware vendors. It is commonly exploited to improve the performance of hardware. General Purpose Database Management Systems (DBMSs), whose main goal is to simplify optimal data storage and processing, generally fall short of this claim because the usage pattern of the stored data cannot be anticipated when designing the system. The current interest in column oriented databases indicates that one strategy does not fit all applications. A DBMS that automatically adapts it’s storage strategy to the workload of the database promises a significant performance increase by maximizing the benefit of hardware optimizations that are based on the principle of data locality. This thesis gives an overview of optimizations that are based on the principle of data locality and the effect they have on the data access performance of applications. Based on the findings, a model is introduced that allows an estimation of the costs of data accesses based on the arrangement of the data in the main memory. This model is evaluated through a series of experiments and incorporated into an automatic layouting component for a DBMS. This layouting component allows the calculation of an analytically optimal storage layout. The performance benefits brought by this component are evaluated in an application benchmark