13 Zentrale Universitätseinrichtungen
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/14
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Item Open Access Mapping molecular surfaces of arbitrary genus to a sphere(2015) Frieß, FlorianMolecular surfaces are one of the most widely used visual representations for the analysis of molecules. They allow different properties of the molecule to be shown and allow additional information to be added, such as chemical properties of the atoms, using colour. With the usual representation of molecular surfaces being three dimensional there are common problems, such as occlusion and view-dependency. To solve these problems a two dimensional representation of the molecular surface can be created. For molecules with a surface of genus zero there are different methods of creating the sphere that is used as an intermediate object to create the map. For molecules with a higher genus this process becomes more difficult. Tunnels can only be mapped to the sphere if they are closed at some point inside the tunnel. Introducing arbitrary cuts can lead to small areas on the map. The deeper inside the tunnel the cut is placed the smaller the area. To avoid these small areas the cuts have to be placed close to the entrance of the tunnel. Therefore a mesh segmentation is performed to identify the tunnel and to create a genus zero surface for the molecule. Based on this identification further information can be displayed, such as geodesic lines showing how the tunnels are connected.Item Open Access Code execution reports: visually augmented summaries of executed source code fragments(2016) Siddiqui, Hafiz AmmarUnderstanding a fragment of code is important for developers as it enables them to optimize, debug and extend it. Developers adopt different procedures for understanding a piece of code, which involves going through the source code, documentation, and profilers results. Various code comprehension techniques have suggested code summarization approaches, which generates the intended behavior of code in natural language text. In this thesis, we present an approach to summarize the actual behavior of a method during its execution. For this purpose, we create a framework that facilitates the generation of interactive and web-based natural language reports with small embedded word-size visualizations. Then, we develop a tool that profiles a method for runtime behavior, and then it processes the information. The tool uses our framework to generate a visually augmented natural language summary report that explains the behavior of the code. In the end, we conduct a small user study to evaluate the quality of our code execution reports.Item Open Access Visual analytics of big data from distributed systems(2017) Kutzleb, AndréDistributed Systems are challenging to debug because the temporal order of events and distributed states are hard to track. The high complexity of distributed systems make fully automatic reasoning difficult to apply. Domain experts are often required to reason about the behavior of a system based on log files from various sources. This situation presents a good opportunity for visual analytics. Data from multiple sources can be preprocessed and visualized, and then domain experts can conduct exploratory analysis to accelerate the identification of issues. The goal of this master thesis was to create such a visual analytics tool to help domain experts explore data collected from distributed systems more efficiently and assist in identifying bugs and anomalies. The system was used by domain experts and helped to identify issues in a distributed system, showing that visual analytics can be a useful tool to assist domain experts in their daily work.Item Open Access Visualizing Optimization Trajectories(2019) Hägele, DavidNonlinear constraint optimization has many applications in technical, scientific as well as economic fields. Understanding solver behavior can help to improve solvers, choose appropriate hyperparameters, and formulate better performing nonlinear programs. This thesis proposes a visual analytics tool for analyzing constraint optimization problems. The optimization process is depicted by a set of two-dimensional trajectories, representing the trace of intermediate solutions during the optimization process. This allows us to obtain an overview of the evolution of the optimization process. To support detailed analysis, supplemental views are added to show the constraints violations and areas of feasible solution. Furthermore, different interaction techniques are implemented to facilitate the exploration process. To showcase the usefulness of the approach, findings from an exemplary analysis based on optimization logs of robot motion planning are presented.Item Open Access Online visualization of German power plants and their production(2017) Ullah, Kazi RiazMaps are used for centuries to visualize geographical or topological information and nowadays, with modern technology, we can create interactive maps that allow us to display and access additional information. Some of them have even become part of our daily life, such as, almost real-time traffic information. Furthermore, maps are often used to display data of population densities, temperatures and spatial distribution of geographical phenomenon. Fraunhofer Institute of Solar Energy ISE decided to build an interactive map that shows the locations of all power plants listed on the European Energy Exchange (EEX). Since July 2014, the Fraunhofer ISE has been providing interactive charts on electricity production and other related information about electricity and power generation in Germany. These charts became very popular and widely used by people from different professions, namely scientists, politicians, journalists as well as online/printed media. Due to the high popularity of these interactive energy charts, an interactive map has been added to the Energy Charts data visualization portal to make the framework more informative and interesting for users. The map has several search options and levels of detail for searching different power plant locations, technical data, and connectivity to the high voltage transmission lines. Furthermore, this new visualization framework is interconnected with the existing energy charts. The dynamic linking, brushing and filtering technique in both map and energy charts have enhanced the framework by an additional layer providing more visibility and information on the selected power plants.Item Open Access Hybrid parallel computing beyond MPI & OpenMP - introducing PGAS & StarSs(2011) Sethi, Muhammad WahajHigh-performance architectures are becoming more and more complex with the passage of time. These large scale, heterogeneous architectures and multi-core system are difficult to program. New programming models are required to make expression of parallelism easier, while keeping productivity of the developer higher. Partition Global Address-space (PGAS) languages such as UPC appeared to augment developer’s productivity for distributed memory systems. UPC provides a simpler, shared memory-like model with a user control over data layout. But it is developer’s responsibility to take care of the data locality, by using appropriate data layouts. SMPSs/StarSs programming model tries to simplify the parallel programming on multicore architectures. It offers task level parallelism, where dependencies among the tasks are determined at the run time. In addition, runtime take cares of the data locality, while scheduling tasks. Hence, providing two-folds improvement in productivity; first, saving developer’s time by using automatic dependency detection, instead of hard coding them. Second, save cache optimization time, as runtime take cares of data locality. The purpose of this thesis is to use the PGAS programming model e.g. UPC for different nodes with the shared memory task based parallelization model i.e. StarSs to take the advantage of the multi core systems and contrast this approach to the legacy MPI and OpenMP combination. Performance as well as programmability is considered in the evaluation. The combination UPC + SMPSs, results in approximately the same execution time as MPI and OpenMP. The current lack of features such as multi-dimensional data distribution or virtual topologies in UPC, make the hybrid UPC + SMPSs/StarSs programming model less programmable than MPI + OpenMP for the application studied in this thesis.Item Open Access Visual Parameter Space Analysis for Classification Models(2019) Heyen, FrankWe present a batch training and visualization system that enables users to visually compare different classifiers and parameter configurations in their performance and behavior. Our approach is plugin-based and classifier-agnostic and allows users to add their own datasets and classifier implementations. It provides multiple visualizations, including a multivariate ranking, a similarity map, a scatterplot that shows correlations between parameters and scores, as well as a training history chart. We enable users to interactively filter, highlight, colorize, sort, and group the displayed data. Using an iterative process, we developed our approach over the course of six months in cooperation with domain experts who apply machine learning for natural language processing. Our evaluation consists of two pair analytics studies and a survey with students. It demonstrates the effectiveness and usability of the implementation and shows desire to use it from domain experts, teachers and students.Item Open Access Ein volumetrischer Imposter zur Level-of-Detail-Darstellung von Partikeldatensätzen(2017) Rau, BenjaminComputersimulationen, welche auf Grundlage von Partikeldaten arbeiten, finden nicht nur immer häufiger Anwendung als wissenschaftliche Hilfsmittel, sondern nehmen auch stetig an Komplexität zu. Die daraus resultierenden Daten werden zur Analyse oftmals visualisiert. Dabei stellen die großen Datenmengen die Visualisierung vor mehrere Herausforderungen. Einerseits benötigen die Daten enorm viel Speicherplatz, was eine direkte Visualisierung oftmals unmöglich macht. Weiterhin kommt es bei der direkten Darstellung der Partikel zu Problemen des Undersamplings und damit verbundenem Bildrauschen. Diese Arbeit untersucht einen möglichen Ansatz, diese beiden Probleme zu umgehen. Dabei werden Partikeldaten in Volumen aggregiert, welche die Normalenverteilungsfunktion dieser Partikel approximiert. Dies erlaubt es zum einen, Speicherplatz einzusparen, indem die aggregierten Partikel nicht mehr im Speicher gehalten werden müssen. Zum anderen ermöglicht es diese Technik, die Daten Offline, mit einer sehr hohen Auflösung, abzutasten und diese hochaufgelöste Abtastung beim interaktiven Rendering zu verwenden, um Bildrauschen zu minimieren.Item Open Access Investigation of volume rendering performance through active learning and visual analysis(2017) Roth, StephanVolume visualization has many real world applications such as medical imaging and scientific research. Rendering volumes can be done directly by shooting rays from the camera through the volume data, or indirectly by extracting features such as iso-surfaces. Knowing the runtime performance of visualization techniques enables for optimized infrastructure planning, trained models could also be reused for interactive quality adaption. Prediction models can make use of information about renderer and datasets to determine execution times before rendering. In this thesis, we present a model based on neural networks to predict rendering times, by using volume properties and rendering configuration. Moreover, our model actively intervenes the sampling process to improve learning while decreasing the amount of necessary measurements. For this, it estimates how likely a drawn sample will improve future predictions. Our model consists of multiple submodels, using their disagreement about certain samples as criteria for possible improvement. We evaluate our model, using different sampling strategies, loss functions and volume rendering techniques. This includes predictions based on measurement data of a volume raycaster, as well as a continuous setup with interleaved execution and prediction of an indirect volume renderer. Our indirect renderer utilizes marching cubes to extract iso-surfaces as triangle mesh from a density field and organizes them in an octree. This way, highly parallel sorting on the graphics card is enabled that is necessary for rendering transparent surfaces in correct order.Item Open Access Evaluation of 2D combination of eye-tracking metrics for task distinction(2019) Metin, Caglar MehmetEye-tracking techniques enable researchers to observe human behaviors by using eye tracking metrics. Machine learning is one of the techniques used in task inference. However, in our research in order to decrease the effort to analyze the task inference, we consider two combinations of different metrics on a two-dimensional scatter plot. Also, we analyze the data with K-Means clustering and correlation analysis to determine the task inference. Two-dimensional scatter plot let the analyst interact with the data in a better manner. In this thesis, we reduced the metrics dimensions, for example, calculating the mean value of the fixation durations that gave us a single value. We examined a few metrics such as crossings of saccades, first fixation duration after the onset of a stimulus, fixation duration mean, and fixation duration median. Furthermore, we created some custom metrics specifically for this research to analyze the tasks for the participants better. Next, we developed a simple game. In the game, there were three game modes for building distinctive gaze behavior. Those game modes include changes in the color tint information, size changes of the stimulus, and as a control mode, a text-only representation which does not contain any color or size differences. Finally, we made a study with six participants. They played our game to give us a dataset which we can work in the analysis with K-means clustering. Nevertheless, the results were promising and helpful in distinguishing human behavior on different tasks. However, this research is not enough for task inference, and there are further improvements which could achieve a better result than the current state.