@phdthesis{18972, author = {{Damerow, Valentina}}, isbn = {{3-939350-09-5}}, publisher = {{Verlagsschriftenreihe des Heinz Nixdorf Instituts, Paderborn}}, title = {{{Average and Smoothed Complexity of Geometric Structures}}}, volume = {{190}}, year = {{2006}}, } @inproceedings{18999, abstract = {{We present a web computing library (PUBWCL) in Java that allows to execute tightly coupled, massively parallel algorithms in the bulk-synchronous (BSP) style on PCs distributed over the internet whose owners are willing to donate their unused computation power. PUBWCL is realized as a peer-to-peer system and features migration and restoration of BSP processes executed on it. The use of Java guarantees a high level of security and makes PUBWCL platform- independent. In order to estimate the loss of efficiency inherent in such a Java-based system, we have compared it to our C-based PUB-Library. As the unused computation power of the participating PCs is unpredictable, we need novel strategies for load balancing that have no access to future changes of the computation power available for the application. We develop, analyze, and compare different load balancing strategies for PUBWCL. In order to handle the influence of the fluctuating available computation power, we classify the external work load. During our evaluation of the load balancing algorithms we simulated the external work load in order to have repeatable testing conditions. With the best performing load balancing strategy we could save 39% of the execution time on average and even up to 50% in particular cases, in our test environment. }}, author = {{Bonorden, Olaf and Meyer auf der Heide, Friedhelm and Gehweiler, Joachim}}, booktitle = {{Journal on Scalable Computing: Practice and Experience}}, pages = {{1--14}}, title = {{{A Web Computing Environment for Parallel Algorithms in Java}}}, year = {{2006}}, } @inproceedings{19001, abstract = {{We present a novel architecture for distributed computing in a peer-to-peer network. In particular, we realize the Paderborn University BSP-based Web Computing Library (PUBWCL), which formerly used a centralized client-server architecture for scheduling and load balancing, as a pure peer-to-peer system. Using distributed heterogeneous hash tables (DHHT), our architecture features scheduling and load balancing of tightly coupled, massively parallel algorithms in the bulk-synchronous (BSP) style with a minimal number of migrations. }}, author = {{Gehweiler, Joachim and Schomaker, Gunnar}}, booktitle = {{Proceeedings of 10th IEEE/ACM International Symposium on Distributed Simulation and Real Time Applications (DS-RT)}}, isbn = {{0769526977}}, pages = {{51--58}}, title = {{{Distributed Load Balancing in Heterogeneous Peer-to-Peer Networks for Web Computing Libraries}}}, doi = {{10.1109/ds-rt.2006.15}}, year = {{2006}}, } @article{23881, abstract = {{Computing a maximum weighted stable set in a bipartite graph is considered well-solved and usually approached with preflow-push, Ford–Fulkerson or network simplex algorithms. We present a combinatorial algorithm for the problem that is not based on flows. Numerical tests suggest that this algorithm performs quite well in practice and is competitive with flow based algorithms especially in the case of dense graphs.}}, author = {{Faigle, Ulrich and Frahling, Gereon}}, issn = {{0166-218X}}, journal = {{Discrete Applied Mathematics}}, pages = {{1380--1391}}, title = {{{A combinatorial algorithm for weighted stable sets in bipartite graphs}}}, doi = {{10.1016/j.dam.2005.05.037}}, year = {{2006}}, } @inproceedings{23882, abstract = {{In this paper we develop an efficient implementation for a k-means clustering algorithm. Our algorithm is a variant of KMHybrid [28, 20], i.e. it uses a combination of Lloyd-steps and random swaps, but as a novel feature it uses coresets to speed up the algorithm. A coreset is a small weighted set of points that approximates the original point set with respect to the considered problem. The main strength of the algorithm is that it can quickly determine clusterings of the same point set for many values of k. This is necessary in many applications, since, typically, one does not know a good value for k in advance. Once we have clusterings for many different values of k we can determine a good choice of k using a quality measure of clusterings that is independent of k, for example the average silhouette coefficient. The average silhouette coefficient can be approximated using coresets.To evaluate the performance of our algorithm we compare it with algorithm KMHybrid [28] on typical 3D data sets for an image compression application and on artificially created instances. Our data sets consist of 300,000 to 4.9 million points. We show that our algorithm significantly outperforms KMHybrid on most of these input instances. Additionally, the quality of the solutions computed by our algorithm deviates less than that of KMHybrid.We also computed clusterings and approximate average silhouette coefficient for k=1,…,100 for our input instances and discuss the performance of our algorithm in detail.}}, author = {{Frahling, Gereon and Sohler, Christian}}, booktitle = {{Proceedings of the twenty-second annual symposium on Computational geometry - SCG '06}}, title = {{{A fast k-means implementation using coresets}}}, doi = {{10.1145/1137856.1137879}}, year = {{2006}}, } @misc{20436, author = {{Hamann, Heiko}}, title = {{{Modeling and Investigation of Robot Swarms}}}, year = {{2006}}, } @article{17979, author = {{Schindelhauer, Christian and Volbert, Klaus and Ziegler, Martin}}, issn = {{0925-7721}}, journal = {{Computational Geometry}}, pages = {{197--214}}, title = {{{Geometric spanners with applications in wireless networks}}}, doi = {{10.1016/j.comgeo.2006.02.001}}, year = {{2006}}, } @article{17985, author = {{Ziegler, Martin}}, issn = {{0885-064X}}, journal = {{Journal of Complexity}}, pages = {{827--849}}, title = {{{Effectively open real functions}}}, doi = {{10.1016/j.jco.2006.05.002}}, year = {{2006}}, } @inbook{17987, author = {{Meer, Klaus and Ziegler, Martin}}, booktitle = {{Logical Approaches to Computational Barriers}}, isbn = {{9783540354666}}, issn = {{0302-9743}}, title = {{{Uncomputability Below the Real Halting Problem}}}, doi = {{10.1007/11780342_39}}, year = {{2006}}, } @inproceedings{18351, abstract = {{In this paper the ideas of a new research project are presented. The material flow simu- lator d3FACT insight shall manage multiple parallel and time synchronous simulations to grand the power of real-time visualization in combination with statistical analysis. This research is issued to overcome the conflict of simulation run repetition for a good statistical basis and real-time immersive visualization. A side effect will be the reduc- tion of time needed for simulation experiments. The planned simulation tool has the feature of triggered cloning, i.e., the user can decide during runtime to clone a set of simulations after changing parameters to preserve the original system. The simulations will be aggregated by visualization and statistics. The rendering is planned to overlay several simulations using effects like inking and transparency. Simulation data will be aggregated with statistical functions and diagrams.}}, author = {{Dangelmaier, Wilhelm and Huber, Daniel and Laroque, Christoph and Aufenanger, Mark and Fischer, Matthias and Krokowski, Jens and Kortenjan, Michael}}, booktitle = {{Simulation and Visualization 2006 (SimViS)}}, pages = {{79--88}}, publisher = {{SCS European Publishing House}}, title = {{{d³FACT insight goes parallel - Aggregation of multiple simulations}}}, year = {{2006}}, } @article{18672, author = {{Sohler, Christian and Czumaj, Artur}}, journal = {{EATCS Bulletin}}, number = {{89}}, pages = {{23----47}}, title = {{{Sublinear-time Algorithms}}}, year = {{2006}}, } @inproceedings{16462, author = {{Bonorden, Olaf and Gehweiler, Joachim and Meyer auf der Heide, Friedhelm and Rehberg, Bettina}}, booktitle = {{Proceedings of 6th International Heinz Nixdorf Symposium: New Trends in Parallel & Distributed Computing}}, pages = {{137--153}}, publisher = {{Verlagsschriftenreihe des Heinz Nixdorf Instituts, Paderborn}}, title = {{{Efficient Parallel Algorithms}}}, volume = {{181}}, year = {{2006}}, } @inbook{16472, author = {{Demaine, Erik D. and Meyer auf der Heide, Friedhelm and Pagh, Rasmus and Pǎtraşcu, Mihai}}, booktitle = {{LATIN 2006: Theoretical Informatics}}, isbn = {{9783540327554}}, issn = {{0302-9743}}, title = {{{De Dictionariis Dynamicis Pauco Spatio Utentibus ({lat.} On Dynamic Dictionaries Using Little Space)}}}, doi = {{10.1007/11682462_34}}, year = {{2006}}, } @inbook{16473, author = {{Dynia, M. and Kutyłowski, J. and Meyer auf der Heide, Friedhelm and Schindelhauer, Christian}}, booktitle = {{Lecture Notes in Computer Science}}, isbn = {{9783540377917}}, issn = {{0302-9743}}, title = {{{Smart Robot Teams Exploring Sparse Trees}}}, doi = {{10.1007/11821069_29}}, year = {{2006}}, } @inbook{16476, author = {{Dynia, Miroslaw and Kutyłowski, Jarosław and Lorek, Paweł and Meyer auf der Heide, Friedhelm}}, booktitle = {{IFIP International Federation for Information Processing}}, isbn = {{9780387346328}}, issn = {{1571-5736}}, title = {{{Maintaining Communication Between an Explorer and a Base Station}}}, doi = {{10.1007/978-0-387-34733-2_14}}, year = {{2006}}, } @techreport{17011, author = {{Dynia, Miroslaw and Kuhmlehn, Andreas and Kutylowski, Jaroslaw and Meyer auf der Heide, Friedhelm and Schindelhauer, Christian}}, title = {{{SmartS Simulator Design}}}, year = {{2006}}, } @phdthesis{19611, author = {{Volbert, Klaus}}, isbn = {{3-935433-77-8}}, publisher = {{Verlagsschriftenreihe des Heinz Nixdorf Instituts, Paderborn}}, title = {{{Geometric Spanners for Topology Control in Wireless Networks}}}, volume = {{168}}, year = {{2005}}, } @inproceedings{19827, abstract = {{We present k-Flipper, a graph transformation algorithm that transforms regular undirected graphs. Given a path of k+2 edges it interchanges the end vertices of the path. By definition this operation preserves regularity and connectivity. We show that every regular connected graph can be reached by a series of these operations for all k ¡Ý 1. We use a randomized version, called Random k-Flipper, in order to create random regular connected undirected graphs that may serve as a backbone for peer-to-peer networks. We prove for degree d¡Ê ¦¸(log n) that a series of O(dn) Random k-Flipper operations with k ∈ ¦¨(d2n2 log 1/¦Å) transforms any graph into an expander graph with high probability, i.e. 1-n-¦¨(1). The Random 1-Flipper is symmetric, i.e. the transformation probability from any labeled d-regular graph G to G' is equal to those from G' to G. From this and the reachability property we conclude that in the limit a series of Random 1-Flipper operations converges against an uniform probability distribution over all connected labeled d-regular graphs. For degree d ∈ ω(1) growing with the graph size this implies that iteratively applying Random 1-Flipper transforms any given graph into an expander asymptotically almost surely. We use these operations as a maintenance operation for a peer-to-peer network based on random regular connected graphs that provides high robustness and recovers from degenerate network structures by continuously applying these random graph transformations. For this, we describe how network operations for joining and leaving the network can be designed and how the concurrency of the graph transformations can be handled.}}, author = {{Mahlmann, Peter and Schindelhauer, Christian}}, booktitle = {{Proceedings of the 17th annual ACM symposium on Parallelism in algorithms and architectures - SPAA'05}}, isbn = {{1581139861}}, title = {{{Peer-to-peer networks based on random transformations of connected regular undirected graphs}}}, doi = {{10.1145/1073970.1073992}}, year = {{2005}}, } @inproceedings{19834, abstract = {{We present a strategy for organizing the communication in wireless ad hoc networks based on a cell structure. We use the unit disk graph model and assume positioning capabilities for all nodes. The cell structure is an abstract view on the network and represents regions where nodes reside (node cells), regions that can be used for the communication flow (link cells) and regions that cannot be bridged due to the restricted transmission range (barrier cells). Each node can establish a cell classification of its neighborhood based on the position data which is announced by all nodes.
The cell structure has two advantages for applying position-based routing: It helps to determine local minima for greedy forwarding and improves recovery from such minima, because for recovery all edges can be used in contrast to other topology-based rules that can be appliedonly on a planar subgraph.
For the analysis of position-based routing algorithms the measures time and traffic are based on the cell structure. The difficulty of exploring the network is expressed by the size of the barriers (i.e. the number of cells in the perimeters). Exploration can be done in parallel, but with increasing traffic. We propose a comparative measure to assess both time and traffic, the combined comparative ratio, which is the maximum of the ratio of routing time and optimal time and the ratio of the traffic and the minimum exploration costs.
While flooding and common single-path strategies have a linear ratio, we present a simple algorithm that has a sub-linear
combined comparative ratio of O(sqrt(h)), where h is the minimal hop distance between source and target.}}, author = {{Rührup, Stefan and Schindelhauer, Christian}}, booktitle = {{19th IEEE International Parallel and Distributed Processing Symposium}}, isbn = {{0769523129}}, pages = {{248}}, title = {{{Competitive Time and Traffic Analysis of Position-Based Routing using a Cell Structure}}}, doi = {{10.1109/ipdps.2005.147}}, year = {{2005}}, } @inproceedings{19835, abstract = {{The Hierarchical Layer Graph (HL graph) is a promising network topology for wireless networks with
variable transmission ranges. It was introduced and analyzed by Meyer auf der Heide et al. 2004.
In this paper we present a distributed, localized and resource-efficient algorithm for constructing this graph. The qualtiy of the HL graph depends on the domination radius and the publication radius, which affect the amount of interference in the network. These parameters also determine whether the HL graph is a c-spanner, which implies an energy-efficient topology. We investigate the performance on randomly distributed node sets and show that the restrictions on these parameters derived from a worst case analysis are not so tight using realistic settings.

Here, we present the results of our extensive experimental evaluation, measuring congestion, dilation and energy. Congestion includes the load that is induced by interfering edges. We distinguish between congestion and realistic congestion where we also take the signal-to-interference ratio into account.
Our experiments show that the HL graph contains energy-efficient paths as well as paths with a few number of hops while preserving a low congestion.}}, author = {{Rührup, Stefan and Schindelhauer, Christian and Volbert, Klaus}}, booktitle = {{Proc. of 4th International Conference on Ad-Hoc, Mobile & Wireless Networks (ADHOC-NOW 2005)}}, isbn = {{9783540291329}}, issn = {{0302-9743}}, pages = {{244--257}}, title = {{{Performance Analysis of the Hierarchical Layer Graph for Wireless Networks}}}, doi = {{10.1007/11561354_21}}, volume = {{3738}}, year = {{2005}}, }