Any software made available via DB TECH REPORTS is provided “as is ” and without any express or implied warranties, including, without limitation, the implied warranty of merchantability and fitness for a particular purpose. The DB TECH REPORTS icon is made from two letters in an early version of the Rune alphabet, which was used by the Vikings, among others. Runes have angular shapes and lack horizontal lines because the primary storage medium was wood, although they may also be found on jewelry, tools, and weapons. Runes were perceived as having magic, hidden powers. The first letter in the logo is “Dagaz, ” the rune for day or daylight and the phonetic equivalent of “d. ” Its meanings include happiness, activity, and satisfaction. The second letter is “Berkano, ” which is associated with the birch tree. Its divinatory meanings include health, new beginnings, growth, plenty, and clearance. It is associated with Idun, goddess of Spring, and New application areas, such as location-based services, rely on the efficient management of large collections of mobile objects. Maintaining accurate, up-to-date positions of these objects results in massive update loads that must be supported by spatial indexing structures and main-memory indexes are usually necessary to provide high update performance. Traditionally, the R-tree and its variants were

In this work a realistic machine model, the CMP-model, is investigated. This model captures the cache hierarchies on mainstream CMPs as well as the ways that these caches interacts. A parallel programming library for benchmarking is presented. The presented library introduces policy based scheduling allowing fair evaluation of scheduling algorithms. The parallel-depth-first scheduler theoretically perform better than the widely used work-stealing scheduler, in the CMP-cache model. Both schedulers are implemented in the benchmarking library. Efficient parallelizations of the well-known sequential sorting algorithms quicksort and multi-way mergesort are analysed based on the CMP-cache model. The parallel quicksort algorithm is based on a parallelization of the in-place sequential partitioning algorithm. The parallel multi-way mergesort is based on a f-way partitioning algorithm. The presented library is used to evaluate the two analysed parallel sorting algorithms using both the implemented schedulers. We find that efficient parallel

From residual and Jacobian assembly to the linear solve, the components of a high-order, Discontinuous Galerkin Finite Element Method (DGFEM) for the Navier-Stokes equations in 3D are presented. Emphasis is given to residual and Jacobian assembly, since these are rarely discussed in the literature; in particular, this thesis focuses on code optimization. Performance properties of DG methods are identified, including key memory bottlenecks. A detailed overview of the memory hierarchy on modern CPUs is given along with discussion on optimization suggestions for utilizing the hierarchy efficiently. Other programming suggestions are also given, including the process for rewriting residual and Jacobian assembly using matrix-matrix products. Finally, a validation of the performance of the 3D, viscous DG solver is presented through a series of canonical test cases.

Abstract. The memory subsystems of contemporary computer architectures are increasingly complex – in fact, so much so that it becomes difficult to estimate the performance impact of many coding constructs, and some long known coding patterns are even discovered to be principally wrong. In contrast, many researchers still reason about algorithmic complexity in simple terms, where memory operations are sequential and of equal cost. The goal of this talk is to give an overview of some memory subsystem features that violate this assumption significantly, with the ambition to motivate development of algorithms tailored to contemporary computer architectures. 1

Haar-like features are ubiquitous in computer vision, e.g. for Viola and Jones face detection or local descriptors such as Speeded-Up-Robust-Features. They are classically computed in one pass over integral image by reading the values at the feature corners. Here we present a new, general parsing formalism for convolving them more efficiently. Our method is fully automatic and applicable to an arbitrary set of Haar-like features. The parser reduces the number of memory accesses which are the main computational bottleneck during convolution on modern computer architectures. It first splits the features into simpler kernels. Then it aligns and reuses them where applicable forming an ensemble of recursive convolution trees, which can be computed faster. This is illustrated with experiments, which show a significant speed-up over the classic approach. 1.