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Cattania C.,German Research Center for Geosciences | Khalid F.,Hasso Plattner Institute for Software Systems Engineering
Computers and Geosciences | Year: 2016

The estimation of space and time-dependent earthquake probabilities, including aftershock sequences, has received increased attention in recent years, and Operational Earthquake Forecasting systems are currently being implemented in various countries. Physics based earthquake forecasting models compute time dependent earthquake rates based on Coulomb stress changes, coupled with seismicity evolution laws derived from rate-state friction. While early implementations of such models typically performed poorly compared to statistical models, recent studies indicate that significant performance improvements can be achieved by considering the spatial heterogeneity of the stress field and secondary sources of stress. However, the major drawback of these methods is a rapid increase in computational costs. Here we present a code to calculate seismicity induced by time dependent stress changes. An important feature of the code is the possibility to include aleatoric uncertainties due to the existence of multiple receiver faults and to the finite grid size, as well as epistemic uncertainties due to the choice of input slip model. To compensate for the growth in computational requirements, we have parallelized the code for shared memory systems (using OpenMP) and distributed memory systems (using MPI). Performance tests indicate that these parallelization strategies lead to a significant speedup for problems with different degrees of complexity, ranging from those which can be solved on standard multicore desktop computers, to those requiring a small cluster, to a large simulation that can be run using up to 1500 cores. © 2016 Elsevier Ltd. Source

Heinze T.,Hasso Plattner Institute for Software Systems Engineering
Proceedings of the IASTED International Conference on Signal and Image Processing, SIP 2011 | Year: 2011

This paper introduces a robust super-resolution algorithm for joint color multi-frame demosaicing. We show that our algorithm, although fast and simple, exhibits convincing results not only within the modeling assumptions, but also for real raw data series. The ultimate goal is its application to telemedical patient monitoring through mobile devices with limited computing power and low quality imaging devices. Source

Panchenko O.,Hasso Plattner Institute for Software Systems Engineering
Proceedings - Working Conference on Reverse Engineering, WCRE | Year: 2011

Software engineers are coerced to deal with a large amount of information about source code. Appropriate tools could assist to handle it, but existing tools are not capable of processing and presenting such a large amount of information sufficiently. With the advent of in-memory column-oriented databases the performance of some data-intensive applications could be significantly improved. This has resulted in a completely new user experience of those applications and enabled new use-cases. This PhD thesis investigates the applicability of in-memory column-oriented databases for supporting daily software engineering activities. The major research question addressed in this thesis is as follows: does in-memory column-oriented database technology provide the necessary performance advantages for working interactively with large amounts of fine-grained structural information about source code? To investigate this research question two scenarios have been selected that particularly suffer from low performance. The first selected scenario is source code search. Existing source code repositories contain a large amount of structural data. Interface definitions, abstract syntax trees, and call graphs are examples of such structural data. Existing tools have solved the performance problems either by reducing the amount of data because of using a coarse-grained representation, or by preparing answers to developers' questions in advance, or by reducing the scope of search. All currently existing alternatives result in the loss of developers' productivity. The second scenario is source code analytics. To complete reverse engineering tasks software engineers often are required to analyze a number of atomic facts that have been extracted from source code. Examples of such atomic facts are occurrences of certain syntactic patterns in code, software product metrics or violations of development guidelines. Each fact typically has several characteristics, such as the type of the fact, the location in code where found, and some attributes. Particularly, analysis of large software systems requires the ability to process a large amount of such facts efficiently. During industrial experiments conducted for this thesis it was evidenced that in-memory technology provides performance gains that improve developers' productivity and enable scenarios previously not possible. This thesis overlaps both software engineering and database technology. From the viewpoint of software engineering, it seeks to find a way to support developers in dealing with a large amount of structural data. From the viewpoint of database technology, source code search and analytics are domains for studying fundamental issues of storing and querying structural data. © 2011 IEEE. Source

Krause C.,Hasso Plattner Institute for Software Systems Engineering | Giese H.,Hasso Plattner Institute for Software Systems Engineering | de Vink E.,TU Eindhoven
Journal of Visual Languages and Computing | Year: 2013

It is generally accepted that building software out of loosely coupled components, such as in service-oriented systems or mobile networks, yields applications that are more robust against changes and failure of single components than monolithic systems. In order to accommodate for changes in the environment or in the requirements, and anticipate to a component failure, applications are often dynamically adapted by means of a reconfiguration. In this paper, we target the visual channel-based coordination language Reo and introduce a combined structural and behavioral model for graph-based component connectors in Reo. Exploiting concepts from category theory, we model reconfigurations of connectors as transformations of the underlying connector graphs. We show that our connector model has a compositional semantics and lift structural reconfigurations to the semantical level. As a concrete application of our framework, we introduce a notion of behavior-preserving reconfiguration for Reo and provide a sufficient condition to ensure behavior-preservation statically. © 2012 Elsevier Ltd. Source

Ludwig N.,Hasso Plattner Institute for Software Systems Engineering | Sack H.,Hasso Plattner Institute for Software Systems Engineering
Proceedings - International Workshop on Database and Expert Systems Applications, DEXA | Year: 2011

Content Based Multimedia Retrieval on nontextual documents is often constrained by available metadata. User-generated tags constitute an important source of information about a resource. To enable search scenarios exceeding traditional text-based search, such as exploratory and semantic search, this textual information must be complemented with semantic entities. Due to tag ambiguities and creative neologisms automatic semantic annotation based on user tags represents a major challenge. In this work, we show how to adopt context information and ontological knowledge to automatically assign semantic entities to user-generated tags for video data. Thus, a sophisticated semantic search on semantic entities is enabled. The algorithm combines co-occurence and link graph analysis using Linked Data. Also, a definition of context reliability in audio-visual content is described. © 2011 IEEE. Source

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