@inproceedings{657, abstract = {{We present two distributed, constant factor approximation algorithms for the metric facility location problem. Both algorithms have been designed with a strong emphasis on applicability in the area of wireless sensor networks: in order to execute them, each sensor node only requires limited local knowledge and simple computations. Also, the algorithms can cope with measurement errors and take into account that communication costs between sensor nodes do not necessarily increase linearly with the distance, but can be represented by a polynomial. Since it cannot always be expected that sensor nodes execute algorithms in a synchronized way, our algorithms are executed in an asynchronous model (but they are still able to break symmetry that might occur when two neighboring nodes act at exactly the same time). Furthermore, they can deal with dynamic scenarios: if a node moves, the solution is updated and the update affects only nodes in the local neighborhood. Finally, the algorithms are robust in the sense that incorrect behavior of some nodes during some round will, in the end, still result in a good approximation. The first algorithm runs in expected O(log_{1+\epsilon} n) communication rounds and yields a \my^4(1+4\my^2(1+\epsilon)^{1/p})^p approximation, while the second has a running time of expected O(log^2_{1+\epsilon} n) communication rounds and an approximation factor of \my^4(1 + 2(1 + \epsilon)^{1/p})^p. Here, \epsilon > 0 is an arbitrarily small constant, p the exponent of the polynomial representing the communication costs, and \my the relative measurement error.}}, author = {{Abshoff, Sebastan and Cord-Landwehr, Andreas and Degener, Bastian and Kempkes, Barbara and Pietrzyk, Peter}}, booktitle = {{Proceedings of the 7th International Symposium on Algorithms for Sensor Systems, Wireless Ad Hoc Networks and Autonomous Mobile Entities (ALGOSENSORS)}}, pages = {{13--27}}, title = {{{Local Approximation Algorithms for the Uncapacitated Metric Facility Location Problem in Power-Aware Sensor Networks}}}, doi = {{10.1007/978-3-642-28209-6_3}}, year = {{2011}}, } @misc{663, author = {{Swierkot, Kamil}}, publisher = {{Universität Paderborn}}, title = {{{Complexity Classes for Local Computation}}}, year = {{2011}}, } @inproceedings{664, abstract = {{Web Computing is a variant of parallel computing where the idle times of PCs donated by worldwide distributed users are employed to execute parallel programs. The PUB-Web library developed by us supports this kind of usage of computing resources. A major problem for the efficient execution of such parallel programs is load balancing. In the Web Computing context, this problem becomes more difficult because of the dynamic behavior of the underlying "parallel computer": the set of available processors (donated PCs) as well as their availability (idle times) change over time in an unpredictable fashion.In this paper, we experimentally evaluate and compare load balancing algorithms in this scenario, namely a variant of the well-established Work Stealing algorithm and strategies based on a heterogeneous version of distributed hash-tables (DHHTs) introduced recently. In order to run a meaningful experimental evaluation, we employ, in addition to our Web Computing library PUB-Web, realistic data sets for the job input streams and for the dynamics of the availability of the resources.Our experimental evaluations suggest that Work Stealing is the better strategy if the number of processes ready to run matches the number of available processors. But a suitable variant of DHHTs outperforms Work Stealing if there are significantly more processes ready to run than available processors.}}, author = {{Gehweiler, Joachim and Kling, Peter and Meyer auf der Heide, Friedhelm}}, booktitle = {{Proceedings of the 9th International Conference on Parallel Processing and Applied Mathematics (PPAM)}}, pages = {{31----40}}, title = {{{An Experimental Comparison of Load Balancing Strategies in a Web Computing Environment}}}, doi = {{10.1007/978-3-642-31500-8_4}}, year = {{2011}}, } @proceedings{667, editor = {{Meyer auf der Heide, Friedhelm and Rajaraman, Rajmohan }}, title = {{{23rd Annual ACM Symposium on Parallelism in Algorithms and Architectures}}}, doi = {{10.1145/1989493}}, year = {{2011}}, } @inproceedings{16410, abstract = {{Gathering n mobile robots in one single point in the Euclidean plane is a widely studied problem from the area of robot formation problems. Classically, the robots are assumed to have no physical extent, and they are able to share a position with other robots. We drop these assumptions and investigate a similar problem for robots with (a spherical) extent: the goal is to gather the robots as close together as possible. More exactly, we want the robots to form a sphere with minimum radius around a predefined point. We propose an algorithm for this problem which synchronously moves the robots towards the center of the sphere unless they block each other. In this case, if possible, the robots spin around the center of the sphere. We analyze this algorithm experimentally in the plane. If R is the distance of the farthest robot to the center of the sphere, the simulations indicate a runtime which is linear in n and R. Additionally, we prove a theoretic upper bound for the runtime of O(nR) for a discrete version of the problem. Simulations also suggest a runtime of O(n + R) for the discrete version.}}, author = {{Cord-Landwehr, Andreas and Degener, Bastian and Fischer, Matthias and Hüllmann, Martina and Kempkes, Barbara and Klaas, Alexander and Kling, Peter and Kurras, Sven and Märtens, Marcus and Meyer auf der Heide, Friedhelm and Raupach, Christoph and Swierkot, Kamil and Warner, Daniel and Weddemann, Christoph and Wonisch, Daniel}}, booktitle = {{37th International Conference on Current Trends in Theory and Practice of Computer Science (SOFSEM 2011)}}, isbn = {{9783642183805}}, issn = {{0302-9743}}, number = {{6543}}, pages = {{178--189}}, publisher = {{Springer}}, title = {{{Collisionless Gathering of Robots with an Extent}}}, doi = {{10.1007/978-3-642-18381-2_15}}, year = {{2011}}, } @inbook{16412, author = {{Gehweiler, Joachim and Meyer auf der Heide, Friedhelm}}, booktitle = {{Algorithms Unplugged}}, isbn = {{9783642153273}}, pages = {{367--374}}, title = {{{Bin Packing - How Do I Get My Stuff into the Boxes}}}, doi = {{10.1007/978-3-642-15328-0_38}}, year = {{2011}}, } @inproceedings{16428, author = {{Rajaraman, Rajmohan and Meyer auf der Heide, Friedhelm}}, isbn = {{9781450307437}}, title = {{{Proceedings of the 23rd ACM symposium on Parallelism in algorithms and architectures - SPAA '11}}}, doi = {{10.1145/1989493}}, year = {{2011}}, } @article{16447, author = {{Degener, Bastian and Fekete, Sándor P. and Kempkes, Barbara and Meyer auf der Heide, Friedhelm}}, issn = {{1574-0137}}, journal = {{Computer Science Review}}, pages = {{57--68}}, title = {{{A survey on relay placement with runtime and approximation guarantees}}}, doi = {{10.1016/j.cosrev.2010.09.005}}, year = {{2011}}, } @inproceedings{16451, author = {{Brandes, Philipp and Degener, Bastian and Kempkes, Barbara and Meyer auf der Heide, Friedhelm}}, booktitle = {{SIROCCO '11: Proc. of the 18th International Colloquium on Structural Information and Communication Complexity}}, pages = {{138--149}}, title = {{{Energy-efficient strategies for building short chains of mobile robots locally}}}, doi = {{10.1016/j.tcs.2012.10.056}}, year = {{2011}}, } @inproceedings{16453, author = {{Degener, Bastian and Kempkes, Barbara and Langner, Tobias and Meyer auf der Heide, Friedhelm and Pietrzyk, Peter and Wattenhofer, Roger}}, booktitle = {{Proceedings of the 23rd ACM symposium on Parallelism in algorithms and architectures - SPAA '11}}, isbn = {{9781450307437}}, title = {{{A tight runtime bound for synchronous gathering of autonomous robots with limited visibility}}}, doi = {{10.1145/1989493.1989515}}, year = {{2011}}, } @inproceedings{16454, author = {{Kling, Peter and Meyer auf der Heide, Friedhelm}}, booktitle = {{Proceedings of the 23rd ACM symposium on Parallelism in algorithms and architectures - SPAA '11}}, isbn = {{9781450307437}}, title = {{{Convergence of local communication chain strategies via linear transformations}}}, doi = {{10.1145/1989493.1989517}}, year = {{2011}}, } @article{16455, author = {{Degener, Bastian and Kempkes, Barbara and Meyer auf der Heide, Friedhelm}}, issn = {{1877-0509}}, journal = {{Procedia Computer Science}}, pages = {{153--155}}, title = {{{Building Simple Formations in Large Societies of Tiny Mobile Robots}}}, doi = {{10.1016/j.procs.2011.09.049}}, year = {{2011}}, } @inbook{16456, author = {{Degener, Bastian and Kempkes, Barbara and Meyer auf der Heide, Friedhelm}}, booktitle = {{Organic Computing — A Paradigm Shift for Complex Systems}}, isbn = {{9783034801294}}, title = {{{Energy-Awareness in Self-organising Robotic Exploration Teams}}}, doi = {{10.1007/978-3-0348-0130-0_35}}, year = {{2011}}, } @inbook{16459, author = {{Brandes, Philipp and Degener, Bastian and Kempkes, Barbara and Meyer auf der Heide, Friedhelm}}, booktitle = {{Structural Information and Communication Complexity}}, isbn = {{9783642222115}}, issn = {{0302-9743}}, title = {{{Energy-Efficient Strategies for Building Short Chains of Mobile Robots Locally}}}, doi = {{10.1007/978-3-642-22212-2_13}}, year = {{2011}}, } @article{17009, author = {{Hsu, D. Frank and Magga, Bruce M. and Ho, Howard C. T. and Hromkovic, Juraj and Lau, Francis C. M. and Meyer auf der Heide, Friedhelm}}, issn = {{0219-2659}}, journal = {{Journal of Interconnection Networks}}, pages = {{vii--viii}}, title = {{{EDITORIAL}}}, doi = {{10.1142/s0219265911002885}}, year = {{2011}}, } @inbook{16409, abstract = {{Given a set of n mobile robots in the d-dimensional Euclidean space, the goal is to let them converge to a single not predefined point. The challenge is that the robots are limited in their capabilities. Robots can, upon activation, compute the positions of all other robots using an individual affine coordinate system. The robots are indistinguishable, oblivious and may have different affine coordinate systems. A very general discrete time model assumes that robots are activated in arbitrary order. Further, the computation of a new target point may happen much earlier than the movement, so that the movement is based on outdated information about other robot's positions. Time is measured as the number of rounds, where a round ends as soon as each robot has moved at least once. In [Cohen, Peleg: Convergence properties of gravitational algorithms in asynchronous robot systems], the Center of Gravity is considered as target function, convergence was proven, and the number of rounds needed for halving the diameter of the convex hull of the robot's positions was shown to be O(n^2) and Omega(n). We present an easy-to-check property of target functions that guarantee convergence and yields upper time bounds. This property intuitively says that when a robot computes a new target point, this point is significantly within the current axes aligned minimal box containing all robots. This property holds, e.g., for the above-mentioned target function, and improves the above O(n^2) to an asymptotically optimal O(n) upper bound. Our technique also yields a constant time bound for a target function that requires all robots having identical coordinate axes. }}, author = {{Cord-Landwehr, Andreas and Degener, Bastian and Fischer, Matthias and Hüllmann, Martina and Kempkes, Barbara and Klaas, Alexander and Kling, Peter and Kurras, Sven and Märtens, Marcus and Meyer auf der Heide, Friedhelm and Raupach, Christoph and Swierkot, Kamil and Warner, Daniel and Weddemann, Christoph and Wonisch, Daniel}}, booktitle = {{Automata, Languages and Programming}}, isbn = {{9783642220111}}, issn = {{0302-9743}}, title = {{{A New Approach for Analyzing Convergence Algorithms for Mobile Robots}}}, doi = {{10.1007/978-3-642-22012-8_52}}, year = {{2011}}, } @inproceedings{19678, author = {{Briest, Patrick and Röglin, Heiko}}, booktitle = {{Workshop on Approximation and Online Algorithms (WAOA)}}, publisher = {{Springer}}, title = {{{The Power of Uncertainty: Bundle-Pricing for Unit-Demand Customers}}}, doi = {{10.1007/978-3-642-18318-8_5}}, volume = {{6534}}, year = {{2010}}, } @inproceedings{19711, author = {{Degener, Bastian and Pietrzyk, Peter and Kempkes, Barbara}}, booktitle = {{International Parallel & Distributed Processing Symposium (IPDPS)}}, title = {{{A local, distributed constant-factor approximation algorithm for the dynamic facility location problem }}}, doi = {{10.1109/IPDPS.2010.5470349}}, year = {{2010}}, } @inproceedings{19796, abstract = {{We introduce the Read-Write-Coding-System (RWC) – a very flexible class of linear block codes that generate efficient and flexible erasure codes for storage networks. In particular, given a message x of k symbols and a codeword y of n symbols, an RW code defines additional parameters k \leq r,w \leq n that offer enhanced possibilities to adjust the fault-tolerance capability of the code. More precisely, an RWC provides linear $\left(n,k,d\right)$-codes that have (a) minimum distance d=n-r+1 for any two codewords, and (b) for each codeword there exists a codeword for each other message with distance of at most w. Furthermore, depending on the values r,w and the code alphabet, different block codes such as parity codes (e.g. RAID 4/5) or Reed-Solomon (RS) codes (if r=k and thus, w=n) can be generated. In storage networks in which I/O accesses are very costly and redundancy is crucial, this flexibility has considerable advantages as r and w can optimally be adapted to read or write intensive applications; only w symbols must be updated if the message x changes completely, what is different from other codes which always need to rewrite y completely as x changes. In this paper, we first state a tight lower bound and basic conditions for all RW codes. Furthermore, we introduce special RW codes in which all mentioned parameters are adjustable even online, that is, those RW codes are adaptive to changing demands. At last, we point out some useful properties regarding safety and security of the stored data.}}, author = {{Mense, Mario and Schindelhauer, Christian}}, booktitle = {{Proceedings of 11th International Symposium on Stabilization, Safety, and Security of Distributed Systems}}, isbn = {{9783642051173}}, issn = {{0302-9743}}, pages = {{624----639}}, title = {{{Read-Write-Codes: An Erasure Resilient Encoding System for Flexible Reading and Writing in Storage Networks}}}, doi = {{10.1007/978-3-642-05118-0_43}}, volume = {{5873}}, year = {{2010}}, } @inproceedings{19824, abstract = {{We present 3nuts, a self-stabilizing peer-to-peer (p2p) network supporting range queries and adapting the overlay structure to the underlying physical network. 3nuts combines concepts of structured and unstructured p2p networks to overcome their individual shortcomings while keeping their strengths. This is achieved by combining self maintaining random networks for robustness, a search tree to allow range queries, and DHTs for load balancing. Simple handshake operations with provable guarantees are used for maintenance and self-stabilization. Efficiency of load balancing, fast data access, and robustness are proven by rigorous analysis.}}, author = {{Janson, Thomas and Mahlmann, Peter and Schindelhauer, Christian}}, booktitle = {{Proceedings of the 16th International Conference on Parallel and Distributed Systems}}, isbn = {{9781424497270}}, title = {{{A Self-Stabilizing Locality-Aware Peer-to-Peer Network Combining Random Networks, Search Trees, and DHTs}}}, doi = {{10.1109/icpads.2010.42}}, year = {{2010}}, }