Analysis of pivot sampling in dual-pivot Quicksort: A holistic analysis of Yaroslavskiy's partitioning scheme

The final publication is available at Springer via http://dx.doi.org/10.1007/s00453-015-0041-7The new dual-pivot Quicksort by Vladimir Yaroslavskiy-used in Oracle's Java runtime library since version 7-features intriguing asymmetries. They make a basic variant of this algorithm use less comparisons than classic single-pivot Quicksort. In this paper, we extend the analysis to the case where the two pivots are chosen as fixed order statistics of a random sample. Surprisingly, dual-pivot Quicksort then needs more comparisons than a corresponding version of classic Quicksort, so it is clear that counting comparisons is not sufficient to explain the running time advantages observed for Yaroslavskiy's algorithm in practice. Consequently, we take a more holistic approach and give also the precise leading term of the average number of swaps, the number of executed Java Bytecode instructions and the number of scanned elements, a new simple cost measure that approximates I/O costs in the memory hierarchy. We determine optimal order statistics for each of the cost measures. It turns out that the asymmetries in Yaroslavskiy's algorithm render pivots with a systematic skew more efficient than the symmetric choice. Moreover, we finally have a convincing explanation for the success of Yaroslavskiy's algorithm in practice: compared with corresponding versions of classic single-pivot Quicksort, dual-pivot Quicksort needs significantly less I/Os, both with and without pivot sampling.Peer ReviewedPostprint (author's final draft

Contact fatigue limits of gears, railway wheels and rails determined by means of multiaxial fatigue criteria

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Educar e cuidar: a indissociabilidade em questão.

Trabalho de Conclusão do Curso de Especialização em Educação Infantil - primeira Edição – Polo Chapecó, para a obtenção do Grau de Especialista em Educação Infantil.Este artigo é resultado do projeto de intervenção realizado em creche municipal, turma de berçário I com nove crianças, faixa etária entre oito e vinte quatro meses, por exigência na conclusão do curso de especialização em Educação Infantil (lato sensu). Neste, buscou-se pesquisar os referenciais teóricos já produzidos sobre a indissociabilidade das ações de educar-cuidar, bem como, analisar a intervenção pedagógica desenvolvida no decorrer do ano em uma turma de berçário, por meio das respostas das crianças às atividades organizadas nessa perspectiva. Os registros aqui contidos materializam o que na prática pedagógica do berçário se constrói em constante processo de cuidados educativos que podem possibilitar a formação humana consciente, crítica e participativa

Analysis of Branch Misses in Quicksort

The analysis of algorithms mostly relies on counting classic elementary operations like additions, multiplications, comparisons, swaps etc. This approach is often sufficient to quantify an algorithm's efficiency. In some cases, however, features of modern processor architectures like pipelined execution and memory hierarchies have significant impact on running time and need to be taken into account to get a reliable picture. One such example is Quicksort: It has been demonstrated experimentally that under certain conditions on the hardware the classically optimal balanced choice of the pivot as median of a sample gets harmful. The reason lies in mispredicted branches whose rollback costs become dominating. In this paper, we give the first precise analytical investigation of the influence of pipelining and the resulting branch mispredictions on the efficiency of (classic) Quicksort and Yaroslavskiy's dual-pivot Quicksort as implemented in Oracle's Java 7 library. For the latter it is still not fully understood why experiments prove it 10% faster than a highly engineered implementation of a classic single-pivot version. For different branch prediction strategies, we give precise asymptotics for the expected number of branch misses caused by the aforementioned Quicksort variants when their pivots are chosen from a sample of the input. We conclude that the difference in branch misses is too small to explain the superiority of the dual-pivot algorithm.Comment: to be presented at ANALCO 201

MODELLING ELASTICITY OF INJECTION MOULDED SHORT FIBRE REINFORCED POLYMERS: COMPARISON BETWEEN EXPERIMENTAL AND ANALYTICAL APPROACHES

In this work we analysed a sample of short fibre reinforced polyamide extracted from an injection moulded plate. We derived local values of the elastic constants by two different numerical methods, one based on simulation and one based on the reconstruction of the sample's microstructure by micro - CT. Results were compared in terms of moduli of elasticity, assuming an orthotropic material model. Fibre orientation was first simulated by process simulation and results were checked against experimental data obtained by the optical section method. Then, fibre orientation data were used for micro-mechanical modelling of the elastic behaviour by means of mean field homogenisation tools. The experimentally based approach was based on micro computed tomography reconstructions of the inner structure of samples extracted from the injection moulded plate. Using numerical models based on the Cell Method, the elastic behaviour of the reconstructed volume was simulated and results were compared with analytical models based on process simulations and homogenization

Evocación de monseñor Juan Carlos Ruta

Monseñor Juan Carlos Ruta falleció el 14 de julio del corriente año 2007, en la misma casa de La Plata de calle 61 entre 4 y 5, donde había vivido desde su juventud y cerca de la cual había nacido el 30 de noviembre de 1918. Fue la suya una vida plena, plenamente vivida, consagrada al sacerdocio, el estudio, la difusión de la fe y el cultivo de la amistad. Una vida totalmente identificada con su ciudad de La Plata, en la cual, recién fundada, habían nacido sus padres. Una vida orgullosamente platense.Fundación Museo La Plat

Evocación de monseñor Juan Carlos Ruta

Monseñor Juan Carlos Ruta falleció el 14 de julio del corriente año 2007, en la misma casa de La Plata de calle 61 entre 4 y 5, donde había vivido desde su juventud y cerca de la cual había nacido el 30 de noviembre de 1918. Fue la suya una vida plena, plenamente vivida, consagrada al sacerdocio, el estudio, la difusión de la fe y el cultivo de la amistad. Una vida totalmente identificada con su ciudad de La Plata, en la cual, recién fundada, habían nacido sus padres. Una vida orgullosamente platense.Fundación Museo La Plat

Players Indifferent to Cooperate and Characterizations of the Shapley Value

n this paper we provide new axiomatizations of the Shapley value for TU-games using axioms that are based on relational aspects in the interactions among players. Some of these relational aspects, in particular the economic or social interest of each player in cooperating with each other, can be found embedded in the characteristic function. We define a particular relation among the players that it is based on mutual indifference. The first new axiom expresses that the payoffs of two players who are not indifferent to each other are affected in the same way if they become enemies and do not cooperate with each other anymore. The second new axiom expresses that the payoff of a player is not affected if players to whom it is indifferent leave the game. We show that the Shapley value is characterized by these two axioms together with the well-known efficiency axiom. Further, we show that another axiomatization of the Shapley value is obtained if we replace t he second axiom and efficiency by the axiom which applies the efficiency condition to every class of indifferent players. Finally, we extend the previous results to the case of weighted Shapley values