13 Zentrale Universitätseinrichtungen
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/14
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Item Open Access Security Tools 7: Paßwörter - ein ewiges Problem?(1997) Lehle, Bernd; Reutter, OliverUnsere bisherigen Artikel beschäftigten sich hauptsächlich mit Dingen, über die sich ein Systembetreuer Gedanken machen muß. Nun kommen wir zu einem Thema, das wirklich alle Benutzer angeht und bei dem jeder Benutzer durch leichtfertiges Verhalten Sicherheitslücken schaffen kann. Es ist daher nötig, daß diese Informationen an alle Benutzer weitergegeben werden.Item Open Access Demonstration of supercomputing activities(1996) Geiger, Alfred; Wierse, Andreas; Helf, Clemens; Schmidt, Thomas; Warendorf, Katina; Küster, Uwe; Loebich, Isabel; Lepper, JürgenDuring the inauguration of HLRS a broad variety of supercomputing-activities was demonstrated. As HLRS is involved in the development of Software for supercomputers as well as in their usage, the demos concentrated on the development of novel simulation-codes in the field of Computational Fluid Dynamics, the software-tools which are necessary for the developper and on the presentation of typical applications from engineering in the VR-lab.Item Open Access Process migration in a parallel environment(Stuttgart : Höchstleistungsrechenzentrum, Universität Stuttgart, 2016) Reber, Adrian; Resch, Michael (Prof. Dr.- Ing. Dr. h.c. Dr. h.c. Prof. E.h.)To satisfy the ever increasing demand for computational resources, high performance computing systems are becoming larger and larger. Unfortunately, the tools supporting system management tasks are only slowly adapting to the increase in components in computational clusters. Virtualization provides concepts which make system management tasks easier to implement by providing more flexibility for system administrators. With the help of virtual machine migration, the point in time for certain system management tasks like hardware or software upgrades no longer depends on the usage of the physical hardware. The flexibility to migrate a running virtual machine without significant interruption to the provided service makes it possible to perform system management tasks at the optimal point in time. In most high performance computing systems, however, virtualization is still not implemented. The reason for avoiding virtualization in high performance computing is that there is still an overhead accessing the CPU and I/O devices. This overhead continually decreases and there are different kind of virtualization techniques like para-virtualization and container-based virtualization which minimize this overhead further. With the CPU being one of the primary resources in high performance computing, this work proposes to migrate processes instead of virtual machines thus avoiding any overhead. Process migration can either be seen as an extension to pre-emptive multitasking over system boundaries or as a special form of checkpointing and restarting. In the scope of this work process migration is based on checkpointing and restarting as it is already an established technique in the field of fault tolerance. From the existing checkpointing and restarting implementations, the best suited implementation for process migration purposes was selected. One of the important requirements of the checkpointing and restarting implementation is transparency. Providing transparent process migration is important enable the migration of any process without prerequisites like re-compilation or running in a specially prepared environment. With process migration based on checkpointing and restarting, the next step towards providing process migration in a high performance computing environment is to support the migration of parallel processes. Using MPI is a common method of parallelizing applications and therefore process migration has to be integrated with an MPI implementation. The previously selected checkpointing and restarting implementation was integrated in an MPI implementation, and thus enabling the migration of parallel processes. With the help of different test cases the implemented process migration was analyzed, especially in regards to the time required to migrated a process and the advantages of optimizations to reduce the process’ downtime during migration.Item Open Access Technisch-Wissenschaftliches Rechnen mit modernen PCs(1996) Helf, Clemens; Küster, Uwe; Zürn, ManuelaIntel hat im vergangenen Jahr mit dem Pentium Pro den ersten PC-Prozessor auf den Markt gebracht, der hohe Leistung, PC-Funktionalität und -Kosten miteinander vereinigen soll. Er wird in Home Computern, Workstations, Servern und Supercomputern stecken. Seine nominelle Leistung ist so hoch wie die einer CRAY-1, das Memory wenigstens das Achtfache. In der Vergangenheit waren aufwendige numerische Berechnungen an Supercomputer gebunden, danach eine Domäne der Workstations. Wird der PC in Zukunft die Alternative im Technisch-Wissenschaftlichen Rechnen?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 Neu für Uni Stuttgart: Datensicherungsdienst(1998) Rentschler, GerhardDas RUS hat bisher den Benutzern aus der Universität angeboten, die Sicherung der Files für die PCs, Workstations und Server auf dem Fileserver ruscy abzulegen. Dort werden die Sicherungsfiles von der Datenmigration (DMF) automatisch auf Band ausgelagert. Dieses System ist in die Jahre gekommen und wird in absehbarer Zeit stillgelegt, insbesondere auch wegen der hohen Wartungskosten. Wir führen daher ein neues Datensicherungssystem ein. Wie die meisten anderen Universitäten in Baden-Württemberg haben wir uns für das Produkt ADSM von IBM entschieden. Dieses Produkt hat eine Server/Client-Architektur und ermöglicht den Backup für fast alle Typen von Workstations und PCs.Item Open Access Visualization techniques for parallel coordinates(2013) Heinrich, Julian; Weiskopf, Daniel (Prof. Dr.)Visualization plays a key role in knowledge discovery, visual data exploration, and visual analytics. Static images are an effective tool for visual communication, summarization, and pattern extraction in large and complex datasets. Only together with human-computer-interaction techniques, visual interfaces enable an analyst to explore large information spaces and to drive the whole analytical reasoning process. Scatterplots and parallel coordinates are well-recognized visualization techniques that are commonly employed for statistics (both explorative and descriptive) and data-mining, but are also gaining importance for scientific visualization. While scatterplots are restricted to the display of at most three dimensions due to the orthogonal layout of coordinate axes, a parallel arrangement allows for the visualization of multiple attributes of a dataset. Although both techniques rely on projections of higher-dimensional geometry and are related by a point–line duality, parallel coordinates enjoy great popularity for the visualization and analysis of multivariate data. Despite their popularity, parallel coordinates are subject to a number of limitations that remain to be solved. For large datasets, the potentially high amount of overlapping lines may hinder the observer from visually extracting meaningful patterns. Encoding observations with polylines make it difficult to follow lines over all dimensions, as they lose visual continuation across the axes. Clusters cannot be represented by the geometry of lines, and the order of axes has a high impact on the patterns exhibited by parallel coordinates. This thesis presents visualization techniques for parallel coordinates that address these limitations. As a foundation, an extensive review of the state of the art of parallel coordinates will be given. Based on the point–line duality, the existing model of continuous scatterplots is adapted to parallel coordinates for the visualization of data defined on continuous domains. To speed up computation and obtain interactive frame rates, a scalable and progressive rendering algorithm is introduced that further allows for arbitrary reconstruction and interpolation schemes. A curve-bundling model for parallel coordinates is evaluated with a user study showing that bundling is effective for cluster visualization based on geometric cues while being equally capable of revealing correlations between neighboring axes. To address the axis-order problem, a graph-based approach is presented that allows for the visualization of all pairwise relations in a matrix layout without redundancy. Finally, the use of parallel coordinates is demonstrated for real datasets from computational fluid dynamics, motion capturing, bioinformatics, and systems biology.Item Open Access Rechnerunterstützte Bestimmung der optimalen Form des Schmiedestücks für ein abgestuftes Teil(1977) Konjusevskaja, R. I.; Davydov, Jurij D.; Petrov, L. N.; Pertschi, Ottmar (Übersetzer)Durch Anwendung eines Rechners und mathematischer Rechenmethoden beim rechnerunterstützten Entwurf eines Schmiedestückes können nicht nur hochqualifizierte Fachleute von unproduktiver Arbeit befreit werden, es kann auch Werkstoff eingespart werden.Item Open Access 3D visualization of multivariate data(2012) Sanftmann, Harald; Weiskopf, Daniel (Prof. Dr.)Nowadays large amounts of data are organized in tables, especially in relational databases where the rows store the data items to which multiple attributes are stored in the columns. Information stored this way, having multiple (more than two or three) attributes, can be treated as multivariate data. Therefore, visualization methods for multivariate data have a large application area and high potential utility. This thesis focuses on the application of 3D scatter plots for the visualization of multivariate data. When dealing with 3D, spatial perception needs to be exploited, by effectively using depth cues to convey spatial information to the user. To improve the presentation of individual 3D scatter plots, a technique is presented that applies illumination to them, thus using the shape-from-shading depth cue. To enable the analysis not only of 3D but of multivariate data, a novel technique is introduced that allows the navigation between 3D scatter plots. Inspecting the large number of 3D scatter plots that can be projected from a multivariate data set is very time consuming. The analysis of multivariate data can benefit from automatic machine learning approaches. A presented method uses decision trees to increase the speed a user can gain an understanding of the multivariate data at no extra cost. Stereopsis can also support the display of 3D scatter plots. Here an improved anaglyph rendering technique is presented, significantly reducing ghosting artifacts. The technique is not only applicable for information visualization, but for general rendering or to present stereoscopic image data. Some information visualization algorithms require high computation time. Many of these algorithms can be parallelized to run interactively. A framework that supports the parallelization on shared and distributed memory systems is presented.