Fakultät Informatik und Mathematik
Refine
Year of publication
- 2007 (26) (remove)
Document Type
- Article (8)
- Part of a Book (5)
- conference proceeding (presentation, abstract) (5)
- conference proceeding (article) (4)
- Bachelor-/Diplom Thesis (1)
- Book (1)
- Part of Periodical (1)
- Report (1)
Has Fulltext
- no (26)
Is part of the Bibliography
- no (26)
Keywords
- Kernspintomografie (2)
- Lagerhaltung (2)
- Offshoring (2)
- Registrierung <Bildverarbeitung> (2)
- Simulation (2)
- 3D reconstruction (1)
- A1 adenosine receptor (1)
- Adenosinrezeptor (1)
- Algorithmus (1)
- Application Code (1)
Institute
- Fakultät Informatik und Mathematik (26)
- Regensburg Medical Image Computing (ReMIC) (5)
- Labor Parallele und Verteilte Systeme (4)
- Labor eHealth (eH) (3)
- Regensburg Strategic IT Management (ReSITM) (3)
- Labor für Digitalisierung (LFD) (2)
- Labor für Technikfolgenabschätzung und Angewandte Ethik (LaTe) (2)
- Fakultät Angewandte Sozial- und Gesundheitswissenschaften (1)
- Labor Empirische Sozialforschung (1)
Begutachtungsstatus
- peer-reviewed (2)
While high-level software components simplify the programming of grid applications and Web services increase their interoperability, developing such components and configuring the interconnecting services is a demanding task. In this paper, we consider the combination of Higher-Order Components (HOCs) with the Fractal component model and the ProActive library.
HOCs are parallel programming components, made accessible on the grid via Web services that use a special class loader enabling code mobility: executable code can be uploaded to a HOC, allowing one to customize the HOC. Fractal simplifies the composition of components and the ProActive library offers a generator for automatically creating Web services from components composed with Fractal, as long as all the parameters of these services have primitive types.
Taking all the advantages of HOCs, ProActive and Fractal together, the obvious conclusion is that composing HOCs using Fractal and automatically exposing them as Web services on the grid via ProActive minimizes the required efforts for building complex grid systems. In this context, we solved the problem of exchanging code-carrying parameters in automatically generated Web services by integrating the HOC class loading mechanism into the ProActive library.
In this paper we investigate the relations between spanners, weak spanners, and power spanners in for any dimension and apply our results to topology control in wireless networks. For , a c-spanner is a subgraph of the complete Euclidean graph satisfying the condition that between any two vertices there exists a path of length at most c-times their Euclidean distance. Based on this ability to approximate the complete Euclidean graph, sparse spanners have found many applications, e.g., in FPTAS, geometric searching, and radio networks. In a weak c-spanner, this path may be arbitrarily long, but must remain within a disk or sphere of radius c-times the Euclidean distance between the vertices. Finally in a c-power spanner, the total energy consumed on such a path, where the energy is given by the sum of the squares of the edge lengths on this path, must be at most c-times the square of the Euclidean distance of the direct edge or communication link.
While it is known that any c-spanner is also both a weak -spanner and a -power spanner for appropriate , depending only on c but not on the graph under consideration, we show that the converse is not true: there exists a family of -power spanners that are not weak C-spanners and also a family of weak -spanners that are not C-spanners for any fixed C. However a main result of this paper reveals that any weak c-spanner is also a C-power spanner for an appropriate constant C.
We further generalize the latter notion by considering -power spanners where the sum of the δth powers of the lengths has to be bounded; so ()-power spanners coincide with the usual power spanners and ()-power spanners are classical spanners. Interestingly, these ()-power spanners form a strict hierarchy where the above results still hold for any some even hold for while counter-examples exist for . We show that every self-similar curve of fractal dimension is not a -power spanner for any fixed C, in general.
Finally, we consider the sparsified Yao-graph (SparsY-graph or YY) that is a well-known sparse topology for wireless networks. We prove that all SparsY-graphs are weak c-spanners for a constant c and hence they allow us to approximate energy-optimal wireless networks by a constant factor.
We propose a quantum key distribution scheme which closely matches the performance of a perfect single photon source. It nearly attains the physical upper bound in terms of key generation rate and maximally achievable distance. Our scheme relies on a practical setup based on a parametric downconversion source and present day, nonideal photon-number detection. Arbitrary experimental imperfections which lead to bit errors are included. We select decoy states by classical postprocessing. This allows one to improve the effective signal statistics and achievable distance.
We discuss the spectral structure and decomposition of multi-photon states. Ordinarily 'multi-photon states' and 'Fock states' are regarded as synonymous. However, when the spectral degrees of freedom are included this is not the case, and the class of 'multi-photon' states is much broader than the class of 'Fock' states. We discuss the criteria for a state to be considered a Fock state. We then address the decomposition of general multi-photon states into bases of orthogonal eigenmodes, building on existing multi-mode theory, and introduce an occupation number representation that provides an elegant description of such states. This representation allows us to work in bases imposed by experimental constraints, simplifying calculations in many situations. Finally we apply this technique to several example situations, which are highly relevant for state of the art experiments. These include Hong–Ou–Mandel interference, spectral filtering, finite bandwidth photo-detection, homodyne detection and the conditional preparation of Schrödinger kitten and Fock states. Our techniques allow for very simple descriptions of each of these examples.
This paper deals with one of the fundamental properties of grid computing – transferring code between grid nodes and executing it remotely on heterogeneous hosts. Contemporary middleware relies for this purpose on Web Services, which makes application programs complicated and low-level and requires much additional expertise from programmers. We compare two mechanisms for grid application programming with regard to their handling of code transfer – the de-facto standard WS-GRAM in Globus and the higher-level approach based on HOCs (Higher-Order Components). We study the advantages and problems of each approach using a real-world application case study – the sequent alignment problem from bioinformatics. Our experiments show the trade-off between reduced development costs and software complexity when HOCs are used and the higher performance of the applications on the grid when using WS-GRAM.
This work integrates two distinct research areas of parallel and distributed computing, (1) automatic loop parallelization, and (2) component-based Grid programming. The latter includes technologies developed within CoreGRID for simplifying Grid programming: the Grid ComponentModel (GCM) and Higher- Order Components (HOCs). Components support developing applications on the Grid without taking all the technical details of the particular platform type into account (network communication, heterogeneity, etc.). The GCMenables a hierarchical composition of programpieces and HOCs enable the reuse of component code in the development of new applications by specifying application-specific operations in a program via code parameters. When a programmer is provided, e. g., with a compute farm HOC, only the independent worker tasks must be described. But, once an application exhibits data or control dependences, the trivial farm is no longer sufficient. Here, the power of loop parallelization tools, like LooPo, comes into play: by embedding LooPo into a HOC, we show that these two technologies in combination facilitate the automatic transformation of a sequential loop nest with complex dependences (supplied by the user as a HOC parameter) into an ordered task graph, which can be processed on the Grid in parallel. This technique can significantly simplify GCM-based systems which combine multiple HOCs and other components. We use an equation system solver based on the successive overrelaxation method (SOR) as our motivating application example and for performance experiments.
Computational grids combine computers in the Internet for distributed data processing and are an attractive platform for the data-intensive applications of bioinformatics. We present an extensible genome processing software for the grid and evaluate its performance. Our software was able to discover previously unknown circular permutations (CP) in the ProDom database containing more than 70MB of protein data. A specific feature of our software is its design as a component: the Alignment HOC, a Higher-Order Component that makes use of the latest Globus toolkit as grid middleware. Besides genome data, the Alignment HOC accepts plugin code for processing this data as its input, and contains all the required configuration to run the component on top of Globus, thus, freeing the non-grid-expert user from dealing with grid middleware. Instead of writing data distribution procedures and configuring the middleware appropriately for every new algorithm, Alignment HOC users reuse the existing component and only write application-specific plugins. To maintain plugins persistently in a reusable manner, we built a web-accessible plugin database with a comfortable administration GUI. The flexible component-based implementation makes it easy to study CPs in other databases (e.g. UniProt/Swiss-Prot) or to use an alignment algorithm different than the standard Needleman-Wunsch. For the efficient distribution of workload, we developed a library of group communication operations for HOCs.