JIGSAW-GEO (1.0): locally orthogonal staggered unstructured grid generation for general circulation modelling on the sphere

An algorithm for the generation of non-uniform, locally-orthogonal staggered unstructured spheroidal grids is described. This technique is designed to generate very high-quality staggered Voronoi/Delaunay meshes appropriate for general circulation modelling on the sphere, including applications to atmospheric simulation, ocean-modelling and numerical weather prediction. Using a recently developed Frontal-Delaunay refinement technique, a method for the construction of high-quality unstructured spheroidal Delaunay triangulations is introduced. A locally-orthogonal polygonal grid, derived from the associated Voronoi diagram, is computed as the staggered dual. It is shown that use of the Frontal-Delaunay refinement technique allows for the generation of very high-quality unstructured triangulations, satisfying a-priori bounds on element size and shape. Grid-quality is further improved through the application of hill-climbing type optimisation techniques. Overall, the algorithm is shown to produce grids with very high element quality and smooth grading characteristics, while imposing relatively low computational expense. A selection of uniform and non-uniform spheroidal grids appropriate for high-resolution, multi-scale general circulation modelling are presented. These grids are shown to satisfy the geometric constraints associated with contemporary unstructured C-grid type finite-volume models, including the Model for Prediction Across Scales (MPAS-O). The use of user-defined mesh-spacing functions to generate smoothly graded, non-uniform grids for multi-resolution type studies is discussed in detail.Comment: Final revisions, as per: Engwirda, D.: JIGSAW-GEO (1.0): locally orthogonal staggered unstructured grid generation for general circulation modelling on the sphere, Geosci. Model Dev., 10, 2117-2140, https://doi.org/10.5194/gmd-10-2117-2017, 201

Regular Datapaths on Field-Programmable Gate Arrays

Field-Programmable Gate Arrays (FPGAs) are a recent kind of programmable logic device. They allow the implementation of integrated digital electronic circuits without requiring the complex optical, chemical and mechanical processes used in a conventional chip fabrication. FPGAs can be embedded in traditional system designflows to perform prototyping and emulation tasks. In addition, they also enable novel applications such as configurable computers with hardware dynamically adaptable to a specific problem. The growing chip capacity now allows even the implementation of CPUs and DSPs on single FPGAs. However, current design automation tools trace their roots to times of very limited FPGA sizes, and are primarily optimized for the implementation of random glue logic. The wide datapaths common to CPUs and DSPs are only processed with reduced performance. This thesis presents Structured Design Implementation (SDI), a suite of specialized tools coordinated by a common strategy, which aims to efficiently map even larger regular datapaths to FPGAs. In all steps, regularity is preserved whenever possible, or restored after disruptive operations were required. The circuits are composed from parametrizable modules providing a variety of logical, arithmetical and storage functions. For each module, multiple target FPGA-specific implementation alternatives may be generated in both gatelevel netlist and layout views. A floorplanner based on a genetic algorithm is then used to simultaneously choose an actual implementation from the set of alternatives for each module, and to arrange the selected module implementations in a linear placement. The floorplanning operation optimizes for short routing delays, high routability, and fit into the target FPGA.Field-Programmable Gate-Arrays (FPGAs) sind eine noch junge Art von programmierbaren Logikbausteinen. Sie erlauben die Implementierung von integrierten Digitalschaltungen ohne die komplizierten optischen, chemischen und mechanischen Prozesse, die normalerweise für die Chipfertigung erforderlich sind. FPGAs können im Rahmen konventioneller Entwurfsmethoden zu Emulationszwecken und Prototyp-Aufbauten herangezogen werden. Sie erlauben aber auch völlig neue Anwendungen wie rekonfigurierbare Computer, deren Hardware dynamisch an ein spezielles Problem angepaßt werden kann. Die gewachsene Chip-Kapazität erlaubt nun sogar die Implementierung von CPUs und digitalen Signalprozessoren (DSPs) auf einem einzelnen FPGA. Die Leistungsfähigkeit der entstandenen Schaltungen wird jedoch durch die zur Zeit erhältlichen CAD-Werkzeuge limitiert, da diese noch auf stark beschränkte FPGA-Größen ausgerichtet sind und primär der platzsparenden Verarbeitung unregelmäßiger Logik dienen. Die breiten Datenpfade in Bit-Slice-Struktur, die den Kern vieler CPUs und DSPs darstellen, werden nur suboptimal behandelt. Diese Arbeit stellt Structured Design Implementation (SDI) vor, ein System von spezialisierten CAD-Werkzeugen, die auch größere reguläre Datenpfade effizient auf FPGAs abbilden. In allen Verarbeitungsschritten wird dabei die bestehende Regularität soweit wie möglich erhalten oder nach regularitätsvernichtenden Operationen wiederhergestellt. Zur Schaltungseingabe steht eine Bibliothek von allgemeinen Modulen aus den Bereichen Logik, Arithmetik und Speicherung bereit. Diese können durch Belegung verschiedener Parameter wie Bit-Breiten und Datentypen an aktuelle Anforderungen angepaßt werden

Unsupervised detection and localization of structural textures using projection profiles

Cataloged from PDF version of article.The main goal of existing approaches for structural texture analysis has been the identification of repeating texture primitives and their placement patterns in images containing a single type of texture. We describe a novel unsupervised method for simultaneous detection and localization of multiple structural texture areas along with estimates of their orientations and scales in real images. First, multi-scale isotropic filters are used to enhance the potential texton locations. Then, regularity of the textons is quantified in terms of the periodicity of projection profiles of filter responses within sliding windows at multiple orientations. Next, a regularity index is computed for each pixel as the maximum regularity score together with its orientation and scale. Finally, thresholding of this regularity index produces accurate localization of structural textures in images containing different kinds of textures as well as non-textured areas. Experiments using three different data sets show the effectiveness of the proposed method in complex scenes.(C)2010 Elsevier Ltd. All rights reserved