Aspects of k-k-Routing in Meshes and OTIS Networks

Aspects of k-k Routing in Meshes and OTIS-Networks Abstract Efficient data transport in parallel computers build on sparse interconnection networks is crucial for their performance. A basic transport problem in such a computer is the k-k routing problem. In this thesis, aspects of the k-k routing problem on r-dimensional meshes and OTIS-G networks are discussed. The first oblivious routing algorithms for these networks are presented that solve the k-k routing problem in an asymptotically optimal running time and a constant buffer size. Furthermore, other aspects of the k-k routing problem for OTIS-G networks are analysed. In particular, lower bounds for the problem based on the diameter and bisection width of OTIS-G networks are given, and the k-k sorting problem on the OTIS-Mesh is considered. Based on OTIS-G networks, a new class of networks, called Extended OTIS-G networks, is introduced, which have smaller diameters than OTIS-G networks.Für die Leistungfähigkeit von Parallelrechnern, die über ein Verbindungsnetzwerk kommunizieren, ist ein effizienter Datentransport entscheidend. Ein grundlegendes Transportproblem in einem solchen Rechner ist das k-k Routing Problem. In dieser Arbeit werden Aspekte dieses Problems in r-dimensionalen Gittern und OTIS-G Netzwerken untersucht. Es wird der erste vergessliche (oblivious) Routing Algorithmus vorgestellt, der das k-k Routing Problem in diesen Netzwerken in einer asymptotisch optimalen Laufzeit bei konstanter Puffergröße löst. Für OTIS-G Netzwerke werden untere Laufzeitschranken für das untersuchte Problem angegeben, die auf dem Durchmesser und der Bisektionsweite der Netzwerke basieren. Weiterhin wird ein Algorithmus vorgestellt, der das k-k Sorting Problem mit einer Laufzeit löst, die nahe an der Bisektions- und Durchmesserschranke liegt. Basierend auf den OTIS-G Netzwerken, wird eine neue Klasse von Netzwerken eingeführt, die sogenannten Extended OTIS-G Netzwerke, die sich durch einen kleineren Durchmesser von OTIS-G Netzwerken unterscheiden

Polyvalent Parallelizations for Hierarchical Block Matching Motion Estimation

Block matching motion estimation algorithms are widely used in video coding schemes. In this paper,we design an efficient hierarchical block matching motion estimation (HBMME) algorithm on a hypercube multiprocessor. Unlike systolic array designs, this solution is not tied down to specific values of algorithm parameters and thus offers increased flexibility. Moreover, the hypercube network can efficiently handle the non regular data flow of the HBMME algorithm. Our techniques nearly eliminate the occurrence of “difficult” communication patterns, namely many-to-many personalized communication, by replacing them with simple shift operations. These operations have an efficient implementation on most of interconnection networks and thus our techniques can be adapted to other networks as well. With regard to the employed multiprocessor we make no specific assumption about the amount of local memory residing in each processor. Instead, we introduce a free parameter S and assume that each processor has O(S) local memory. By doing so, we handle all the cases of modern multiprocessors, that is fine-grained, medium-grained and coarse-grained multiprocessors and thus our design is quite general

Move-optimal partial gathering of mobile agents in asynchronous trees

In this paper, we consider the partial gathering problem of mobile agents in asynchronous tree networks. The partial gathering problem is a generalization of the classical gathering problem, which requires that all the agents meet at the same node. The partial gathering problem requires, for a given positive integer g, that each agent should move to a node and terminate so that at least g agents should meet at each of the nodes they terminate at. The requirement for the partial gathering problem is weaker than that for the (well-investigated) classical gathering problem, and thus, we clarify the difference on the move complexity between them. We consider two multiplicity detection models: weak multiplicity detection and strong multiplicity detection models. In the weak multiplicity detection model, each agent can detect whether another agent exists at the current node or not but cannot count the exact number of the agents. In the strong multiplicity detection model, each agent can count the number of agents at the current node. In addition, we consider two token models: non-token model and removable token model. In the non-token model, agents cannot mark the nodes or the edges in any way. In the removable-token model, each agent initially leaves a token on its initial node, and agents can remove the tokens. Our contribution is as follows. First, we show that for the non-token model agents require Ω(kn) total moves to solve the partial gathering problem, where n is the number of nodes and k is the number of agents. Second, we consider the weak multiplicity detection and non-token model. In this model, for asymmetric trees, by a previous result agents can achieve the partial gathering in O(kn) total moves, which is asymptotically optimal in terms of total moves. In addition, for symmetric trees we show that there exist no algorithms to solve the partial gathering problem. Third, we consider the strong multiplicity detection and non-token model. In this model, for any trees we propose an algorithm to achieve the partial gathering in O(kn) total moves, which is asymptotically optimal in terms of total moves. At last, we consider the weak multiplicity detection and removable-token model. In this model, we propose an algorithm to achieve the partial gathering in O(gn) total moves. Note that in this model, agents require Ω(gn) total moves to solve the partial gathering problem. Hence, the second proposed algorithm is also asymptotically optimal in terms of total moves

Epidemic spreading and information dissemination in technological and social systems

In dieser Arbeit betrachten wir Probleme aus dem Bereich der Nachrichten- und Krankheitsverbreitung in dynamischen als auch statischen Strukturen aus dem Gebiet der technologischen und der sozialen Netzwerke. Als erste Fragestellung untersuchen wir, ob ein verteiltes Protokoll zur Nachrichtenverbreitung in Netzwerken mit Power Law Knotengradverteilung existiert, so dass sich die Knotengradverteilung nicht negativ bemerkbar macht. Wir präsentieren ein Protokoll, welches mit hoher Wahrscheinlichkeit nur O(log n) viele Runden mit O(n loglog n) vielen Nachrichten benötigt um alle n Knoten zu informieren. Als nächstes untersuchen wir wie Strategien zur Eindämmung einer solchen Ausbreitung aussehen könnten. Sei V der für die Ausbreitung der schädlichen Nachricht verantwortliche Prozess. Wir lassen V sich von jedem infizierten Knoten über eine konstante Anzahl von Verbindungen verbreiten. Unsere Strategie zur Bekämpfung von V wird an jedem infizierten Knoten nach einer konstanten Anzahl von Schritten aktiviert. Ist der minimale Knotengrad loglog n, so zeigen wir, dass die Immunisierung der direkten Nachbarschaft ausreicht um die Infektion mit hoher Wahrscheinlichkeit zu eliminieren. Ist der minimale Knotengrad eine Konstante und immunisiert jeder infizierte Knoten v alle Knoten in seiner O(log(d(v)))-Nachbarschaft, wobei d(v) den Knotengrad von Knoten v bezeichnet, lassen sich ähnliche Abschätzungen zeigen. Zudem betrachten wir eine Epidemie in einer städtischen Umgebung mit mobilen Einwohnern. Werden keinerlei Gegenmaßnahmen getroffen, so bleibt dennoch mit hoher Wahrscheinlichkeit ein polynomieller Anteil der Population von der Epidemie unberührt. Werden jedoch Gegenmaßnahmen genutzt, so werden mit Wahrscheinlichkeit 1-o(1) nur polylogarithmisch viele Individuen infiziert.In this thesis we consider the problems of information dissemination and epidemic spreading in dynamic as well as static technological and social networks. We start by wondering if there might be a fast decentralized dissemination protocol, such that a power law degree distribution does not slow down the dissemination process in the network. We present a protocol that informs all n nodes within O(log n) many rounds using O(n loglog n) many transmissions with high probability. But how do we design a counteracting dissemination process to combat the malicious one denoted by V? Suppose V uses a constant number of randomly chosen connections of each infected node to infect others for one time only and suppose that the counteracting dissemination process is activated on each infected node after a constant delay. We show that it suffices to immunize the neighborhood of each infected node, provided the minimum degree of the network is loglog n. Otherwise, if the minimum degree of the network is constant, we propose to immunize every node within O(log(d(v))) many hops of each infected node v, where d(v) denotes the degree of node v. Executing these strategies we prove that V does not infect more than o(n) many nodes until it is eliminated with high probability. Finally, we take mobility into account and examine an epidemic outbreak in an urban environment inhabited by mobile individuals on a small and on a large scale. Amongst others, we show that at least a polynomial fraction of the individuals remains uninfected even if they do not respond to the epidemic outbreak in any way. However, if the epidemic outbreak does influence the individual's behavioral pattern and certain countermeasures are applied, then only a polylogarithmic amount of individuals is infected until the epidemic is embanked with probability 1-o(1).Tag der Verteidigung: 24.10.2014Paderborn, Univ., Diss., 201

Design and analysis of sequential and parallel single-source shortest-paths algorithms

We study the performance of algorithms for the Single-Source Shortest-Paths (SSSP) problem on graphs with n nodes and m edges with nonnegative random weights. All previously known SSSP algorithms for directed graphs required superlinear time. Wie give the first SSSP algorithms that provably achieve linear O(n-m)average-case execution time on arbitrary directed graphs with random edge weights. For independent edge weights, the linear-time bound holds with high probability, too. Additionally, our result implies improved average-case bounds for the All-Pairs Shortest-Paths (APSP) problem on sparse graphs, and it yields the first theoretical average-case analysis for the "Approximate Bucket Implementation" of Dijkstra\u27s SSSP algorithm (ABI-Dijkstra). Futhermore, we give constructive proofs for the existence of graph classes with random edge weights on which ABI-Dijkstra and several other well-known SSSP algorithms require superlinear average-case time. Besides the classical sequential (single processor) model of computation we also consider parallel computing: we give the currently fastest average-case linear-work parallel SSSP algorithms for large graph classes with random edge weights, e.g., sparse rondom graphs and graphs modeling the WWW, telephone calls or social networks.In dieser Arbeit untersuchen wir die Laufzeiten von Algorithmen für das Kürzeste-Wege Problem (Single-Source Shortest-Paths, SSSP) auf Graphen mit n Knoten, M Kanten und nichtnegativen zufälligen Kantengewichten. Alle bisherigen SSSP Algorithmen benötigen auf gerichteten Graphen superlineare Zeit. Wir stellen den ersten SSSP Algorithmus vor, der auf beliebigen gerichteten Graphen mit zufälligen Kantengewichten eine beweisbar lineare average-case-Komplexität O(n+m)aufweist. Sind die Kantengewichte unabhängig, so wird die lineare Zeitschranke auch mit hoher Wahrscheinlichkeit eingehalten. Außerdem impliziert unser Ergebnis verbesserte average-case-Schranken für das All-Pairs Shortest-Paths (APSP) Problem auf dünnen Graphen und liefert die erste theoretische average-case-Analyse für die "Approximate Bucket Implementierung" von Dijkstras SSSP Algorithmus (ABI-Dijkstra). Weiterhin führen wir konstruktive Existenzbeweise für Graphklassen mit zufälligen Kantengewichten, auf denen ABI-Dijkstra und mehrere andere bekannte SSSP Algorithmen durchschnittlich superlineare Zeit benötigen. Neben dem klassischen seriellen (Ein-Prozessor) Berechnungsmodell betrachten wir auch Parallelverarbeitung; für umfangreiche Graphklassen mit zufälligen Kantengewichten wie z.B. dünne Zufallsgraphen oder Modelle für das WWW, Telefonanrufe oder soziale Netzwerke stellen wir die derzeit schnellsten parallelen SSSP Algorithmen mit durchschnittlich linearer Arbeit vor

The Glass Jaw. The Presence of Incivility, Conflict, and Bullying in Disempowering Workplaces: A Study of Middle-Level Managers in HEIs

Middle-level managers at HEIs experience stress-related conflicts that include incivility and bullying. There is a gap in the literature regarding middle-level managers’ contributions to improving interpersonal relationships in the workplace and the type of conflict-management training most suited to middle-level managers in HEIs when incivility, conflict, and bullying are present. This qualitative design study sought to understand conflict management from the perspective of HEI middle-level managers within the manager-to-subordinate relationship. The study examined the lived experiences of 10 HEI middle-level managers with coded data revealing four overall themes: structural challenges, sources of conflict, conflict training, and managing conflict. The results of this study showed that middle-level managers did not utilize knowledge obtained in conflict-management training, instead preferring to create their conflictmanagement tactics and strategies. The study’s results may help increase knowledge of conflict management for middle-level managers in HEIs and a greater understanding of the tools needed to work through incivility and bullying

Tourist Trap: On Being Raised In Award-winning Sand

The literary essays in this collection explore the relationships between mind, body, and environment as the narrator explores Orlando, her beachfront hometown of Sarasota, and other tourist traps. The traditional and experimental essays here question how residents make popular vacation destinations their own and how much trust one can put in strangers, neighbors, city planners, theme-park designers, and lovers. Dance floors, hybrid bikes, flying elephants, swing sets, and swimming pools fill these pages. Worries spiral like disco lights on dance floors, and cultural forces press down with the constant pressure of pedal strokes. With the embodiment of place comes connection between environment and activity; music, buildings, landscape, and physical activity heighten the relationship between personal identity and place. Everything moves, but the appeal of tourist traps remains constant