112 research outputs found
Two problems related to prescribed curvature measures
Existence of convex body with prescribed generalized curvature measures is
discussed, this result is obtained by making use of Guan-Li-Li's innovative
techniques. In surprise, that methods has also brought us to promote
Ivochkina's estimates for prescribed curvature equation in \cite{I1, I}.Comment: 12 pages, Corrected typo
Fuchsian convex bodies: basics of Brunn--Minkowski theory
The hyperbolic space \H^d can be defined as a pseudo-sphere in the
Minkowski space-time. In this paper, a Fuchsian group is a group of
linear isometries of the Minkowski space such that \H^d/\Gamma is a compact
manifold. We introduce Fuchsian convex bodies, which are closed convex sets in
Minkowski space, globally invariant for the action of a Fuchsian group. A
volume can be associated to each Fuchsian convex body, and, if the group is
fixed, Minkowski addition behaves well. Then Fuchsian convex bodies can be
studied in the same manner as convex bodies of Euclidean space in the classical
Brunn--Minkowski theory. For example, support functions can be defined, as
functions on a compact hyperbolic manifold instead of the sphere.
The main result is the convexity of the associated volume (it is log concave
in the classical setting). This implies analogs of Alexandrov--Fenchel and
Brunn--Minkowski inequalities. Here the inequalities are reversed
Applying the Roofline Performance Model to the Intel Xeon Phi Knights Landing Processor
The Roofline Performance Model is a visually intuitive method used to bound the sustained peak floating-point performance of any given arithmetic kernel on any given processor architecture. In the Roofline, performance is nominally measured in floating-point operations per second as a function of arithmetic intensity (operations per byte of data). In this study we determine the Roofline for the Intel Knights Landing (KNL) processor, determining the sustained peak memory bandwidth and floating-point performance for all levels of the memory hierarchy, in all the different KNL cluster modes.We then determine arithmetic intensity and performance for a suite of application kernels being targeted for the KNL based supercomputer Cori, and make comparisons to current Intel Xeon processors. Cori is the National Energy Research Scientific Computing Centerâs (NERSC) next generation supercomputer. Scheduled for deployment mid-2016, it will be one of the earliest and largest KNL deployments in the world
Starfire Optical Range 3.5-m telescope adaptive optical system
A 941 channel, 1500 Hertz frame rate adaptive optical (AO) system has been installed and tested in the coude path of the 3.5m telescope at the USAF Research Laboratory Starfire Optical Range. This paper describes the design and measured performance of the principal components comprising this system and present sample results from the first closed-loop test of the system on stars and an artificial source simulator
Researching workplace friendships: drawing insights from the sociology of friendship
Although organizational research on workplace friendships is well established, it has been criticized for its predominately postpositivistic outlook, which largely focuses on how workplace friendships can be linked to improving organizational outcomes such as efficiency and performance. As a consequence other aspects of the lived experiences of work and friendship are obscured, in particular how these friendships are important in their own right and how they function as social and personal relationships. Supplementing postpositivistic research on workplace friendships, this article shows how researchers can derive theoretical insights from a âsociology of friendshipâ. The main contribution of this article relates to the development of a sociology of workplace friendship that understands the porous and mutable nature of these relationships and considers the social and personal factors that influence their role, place and meaning in the workplace. As such, three sociological frames of analysis are elaborated that encourage researchers to examine friendships at work as a set of contextually contingent social practices and as historically patterned social and personal relationships. This article articulates an agenda of research to inspire and guide researchers using these frames, one potential outcome of which is generating much needed scholarship that explores how workplace friendships contribute to human flourishing
Starfire Optical Range 3.5-m telescope adaptive optical system
A 941 channel, 1500 Hertz frame rate adaptive optical (AO) system has been installed and tested in the coude path of the 3.5m telescope at the USAF Research Laboratory Starfire Optical Range. This paper describes the design and measured performance of the principal components comprising this system and present sample results from the first closed-loop test of the system on stars and an artificial source simulator
Writing Russia's future: paradigms, drivers, and scenarios
The development of prediction and forecasting in the social sciences over the past century and more is closely linked with developments in Russia. The Soviet collapse undermined confidence in predictive capabilities, and scenario planning emerged as the dominant future-oriented methodology in area studies, including the study of Russia. Scenarists anticipate multiple futures rather than predicting one. The approach is too rarely critiqued. Building on an account of Russia-related forecasting in the twentieth century, analysis of two decades of scenarios reveals uniform accounts which downplay the insights of experts and of social science theory alike
A whole-genome shotgun approach for assembling and anchoring the hexaploid bread wheat genome
Citation: Chapman, J. A., Mascher, M., Buluç, A., Barry, K., Georganas, E., Session, A., . . . Rokhsar, D. S. (2015). A whole-genome shotgun approach for assembling and anchoring the hexaploid bread wheat genome. Genome Biology, 16(1). doi:10.1186/s13059-015-0582-8Polyploid species have long been thought to be recalcitrant to whole-genome assembly. By combining high-throughput sequencing, recent developments in parallel computing, and genetic mapping, we derive, de novo, a sequence assembly representing 9.1 Gbp of the highly repetitive 16 Gbp genome of hexaploid wheat, Triticum aestivum, and assign 7.1 Gb of this assembly to chromosomal locations. The genome representation and accuracy of our assembly is comparable or even exceeds that of a chromosome-by-chromosome shotgun assembly. Our assembly and mapping strategy uses only short read sequencing technology and is applicable to any species where it is possible to construct a mapping population. © 2015 Chapman et al. licensee BioMed Central.Additional Authors: Muehlbauer, G. J.;Stein, N.;Rokhsar, D. S
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Extracting ultra-scale lattice boltzmann performance via hierarchical and distributed auto-tuning
We are witnessing a rapid evolution of HPC node architectures and on-chip parallelism as power and cooling constraints limit increases in microprocessor clock speeds. In this work, we demonstrate a hierarchical approach towards effectively extracting performance for a variety of emerging multicore-based supercomputing platforms. Our examined application is a structured grid-based Lattice Boltzmann computation that simulates homogeneous isotropic turbulence in magnetohydrodynamics. First, we examine sophisticated sequential auto-tuning techniques including loop transformations, virtual vectorization, and use of ISA-specific intrinsics. Next, we present a variety of parallel optimization approaches including programming model exploration (at MPI, MPI/OpenMP, and MPI/Pthreads), as well as data and thread decomposition strategies designed to mitigate communication bottlenecks. Finally, we evaluate the impact of our hierarchical tuning techniques using a variety of problem sizes via large-scale simulations on state-of-the-art Cray XT4, Cray XE6, and IBM BlueGene/P platforms. Results show that our unique tuning approach improves performance and energy requirements by up to 3.4Ă using 49,152 cores, while providing a portable optimization methodology for a variety of numerical methods on forthcoming HPC systems. Copyright 2011 ACM
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