Parallel Unsmoothed Aggregation Algebraic Multigrid Algorithms on GPUs

We design and implement a parallel algebraic multigrid method for isotropic graph Laplacian problems on multicore Graphical Processing Units (GPUs). The proposed AMG method is based on the aggregation framework. The setup phase of the algorithm uses a parallel maximal independent set algorithm in forming aggregates and the resulting coarse level hierarchy is then used in a K-cycle iteration solve phase with a $\ell^1$-Jacobi smoother. Numerical tests of a parallel implementation of the method for graphics processors are presented to demonstrate its effectiveness.Comment: 18 pages, 3 figure

Mastermind Mutations Generate a Unique Constellation of Midline Cells within the Drosophila CNS

Background: The Notch pathway functions repeatedly during the development of the central nervous system in metazoan organisms to control cell fate and regulate cell proliferation and asymmetric cell divisions. Within the Drosophila midline cell lineage, which bisects the two symmetrical halves of the central nervous system, Notch is required for initial cell specification and subsequent differentiation of many midline lineages. Methodology/Principal Findings: Here, we provide the first description of the role of the Notch co-factor, mastermind, in the central nervous system midline of Drosophila. Overall, zygotic mastermind mutations cause an increase in midline cell number and decrease in midline cell diversity. Compared to mutations in other components of the Notch signaling pathway, such as Notch itself and Delta, zygotic mutations in mastermind cause the production of a unique constellation of midline cell types. The major difference is that midline glia form normally in zygotic mastermind mutants, but not in Notch and Delta mutants. Moreover, during late embryogenesis, extra anterior midline glia survive in zygotic mastermind mutants compared to wild type embryos. Conclusions/Significance: This is an example of a mutation in a signaling pathway cofactor producing a distinct centra

A Review of Regular Decompositions of Vector Fields: Continuous, Discrete, and Structure-Preserving

We elaborate so-called regular decompositions of vector fields on a three-dimensional Lipschitz domain where the field and its rotation/divergence belong to L2 and where the tangential/normal component of the field vanishes on a sufficiently smooth “Dirichlet” part of the boundary. We impose no restrictions on the topology of the domain, its boundary, or the Dirichlet boundary parts. The field is split into a regular vector field, whose Cartesian components lie in H1 and vanish on the Dirichlet boundary, and a remainder contained in the kernel of the rotation/divergence operator. The decomposition is proved to be stable not only in the natural norms, but also with respect to the L2 norm. Besides, for special cases of mixed boundary conditions, we show the existence of H1-regular potentials that characterize the range of the rotation and divergence operator. We conclude with results on discrete counterparts of regular decompositions for spaces of low-order discrete differential forms on simplicial meshes. Essentially, all results for function spaces carry over, though local correction terms may be necessary. These discrete regular decompositions have become an important tool in finite element exterior calculus (FEEC) and for the construction of preconditioners.ISSN:1439-735

A smoother based on nonoverlapping domain decomposition methods for H(div) problems: A numerical study

The purpose of this paper is to introduce a V-cycle multigrid method for vector field problems discretized by the lowest order Raviart-Thomas hexahedral element. Our method is connected with a smoother based on a nonoverlapping domain decomposition method. We present numerical experiments to show the effectiveness of our method

Measurements of hadron production in π++C and π++Be interactions at 60 GeV/c

Precise knowledge of hadron production rates in the generation of neutrino beams is necessary for accelerator-based neutrino experiments to achieve their physics goals. NA61/SHINE, a large-acceptance hadron spectrometer, has recorded hadron+nucleus interactions relevant to ongoing and future long-baseline neutrino experiments at Fermi National Accelerator Laboratory. This paper presents three analyses of interactions of 60  GeV/c π+ with thin, fixed carbon and beryllium targets. Integrated production and inelastic cross sections were measured for both of these reactions. In an analysis of strange, neutral hadron production, differential production multiplicities of K0S, Λ and ¯Λ were measured. Lastly, in an analysis of charged hadron production, differential production multiplicities of π+, π−, K+, K− and protons were measured. These measurements will enable long-baseline neutrino experiments to better constrain predictions of their neutrino flux in order to achieve better precision on their neutrino cross section and oscillation measurements

Measurements of π± , K± and proton double differential yields from the surface of the T2K replica target for incoming 31 GeV/c protons with the NA61/SHINE spectrometer at the CERN SPS

Measurements of the π±, K±, and proton double differential yields emitted from the surface of the 90-cm-long carbon target (T2K replica) were performed for the incoming 31 GeV/c protons with the NA61/SHINE spectrometer at the CERN SPS using data collected during 2010 run. The double differential π± yields were measured with increased precision compared to the previously published NA61/SHINE results, while the K± and proton yields were obtained for the first time. A strategy for dealing with the dependence of the results on the incoming proton beam profile is proposed. The purpose of these measurements is to reduce significantly the (anti)neutrino flux uncertainty in the T2K long-baseline neutrino experiment by constraining the production of (anti)neutrino ancestors coming from the T2K target