1,100 research outputs found

    Lower bounds on systolic gossip

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    AbstractGossiping is an extensively investigated information dissemination process in which each processor has a distinct item of information and has to collect all the items possessed by the other processors. In this paper we provide an innovative and general lower bound technique relying on the novel notion of delay digraph of a gossiping protocol and on the use of matrix norm methods. Such a technique is very powerful and allows the determination of new and significantly improved lower bounds in many cases. In fact, we derive the first general lower bound on the gossiping time of systolic protocols, i.e., constituted by a periodic repetition of simple communication steps. In particular, given any network of n processors and any systolic period s, in the directed and the undirected half-duplex cases every s-systolic gossip protocol takes at least log(n)/log(1/λ)−O(loglog(n)) time steps, where λ is the unique solution between 0 and 1 of λ·p⌊s/2⌋(λ)·p⌈s/2⌉(λ)=1, with pi(λ)=1+λ2+⋯+λ2i−2 for any integer i>0. We then provide improved lower bounds in the directed and half-duplex cases for many well-known network topologies, such as Butterfly, de Bruijn, and Kautz graphs. All the results are extended also to the full-duplex case. Our technique is very general, as for s→∞ it allows the determination of improved results even for non-systolic protocols. In fact, for general networks, as a simple corollary it yields a lower bound only an O(loglog(n)) additive factor far from the general one independently proved in [Proc. 1st ACM Symposium on Parallel Algorithms and Architectures (SPAA), 1989, p. 318; Topics in Combinatorics and Graph Theory (1990) 451; SIAM Journal on Computing 21(1) (1992) 111; Discrete Applied Mathematics 42 (1993) 75] for all graphs and any (non-systolic) gossip protocol. Moreover, for specific networks, it significantly improves with respect to the previously known results, even in the full-duplex case. Correspondingly, better lower bounds on the gossiping time of non-systolic protocols are determined in the directed, half-duplex and full-duplex cases for Butterfly, de Bruijn, and Kautz graphs. Even if in this paper we give only a limited number of examples, our technique has wide applicability and gives a general framework that often allows to get improved lower bounds on the gossiping time of systolic and non-systolic protocols in the directed, half-duplex and full-duplex cases

    Universal Protocols for Information Dissemination Using Emergent Signals

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    We consider a population of nn agents which communicate with each other in a decentralized manner, through random pairwise interactions. One or more agents in the population may act as authoritative sources of information, and the objective of the remaining agents is to obtain information from or about these source agents. We study two basic tasks: broadcasting, in which the agents are to learn the bit-state of an authoritative source which is present in the population, and source detection, in which the agents are required to decide if at least one source agent is present in the population or not.We focus on designing protocols which meet two natural conditions: (1) universality, i.e., independence of population size, and (2) rapid convergence to a correct global state after a reconfiguration, such as a change in the state of a source agent. Our main positive result is to show that both of these constraints can be met. For both the broadcasting problem and the source detection problem, we obtain solutions with a convergence time of O(log⁥2n)O(\log^2 n) rounds, w.h.p., from any starting configuration. The solution to broadcasting is exact, which means that all agents reach the state broadcast by the source, while the solution to source detection admits one-sided error on a Δ\varepsilon-fraction of the population (which is unavoidable for this problem). Both protocols are easy to implement in practice and have a compact formulation.Our protocols exploit the properties of self-organizing oscillatory dynamics. On the hardness side, our main structural insight is to prove that any protocol which meets the constraints of universality and of rapid convergence after reconfiguration must display a form of non-stationary behavior (of which oscillatory dynamics are an example). We also observe that the periodicity of the oscillatory behavior of the protocol, when present, must necessarily depend on the number ^\\# X of source agents present in the population. For instance, our protocols inherently rely on the emergence of a signal passing through the population, whose period is \Theta(\log \frac{n}{^\\# X}) rounds for most starting configurations. The design of clocks with tunable frequency may be of independent interest, notably in modeling biological networks

    Contesting Victorian Beliefs: The Unintended Effects of Victorian Novels

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    Victorian society reproduced polarized gender roles known as the ideology of the separate spheres in order to confine the authority of women. However, as the Victorian Era progressed social norms were gradually contested, and the consequences of the assertion of female authority led to reform. In reinterpreting the Victorian women’s movement, I will interpret the effects of the writers of the late nineteenth century who argued explicitly against proposed changes in the traditional position of middle-class women. I will most closely examine how the late Victorian novels, A Marriage Below Zero by Alan Dale and The Revolt of Man by Walter Besant end up subverting their own anti-feminist agendas and actually contributing to the political project of late-Victorian feminism by inadvertently demonstrating that the separate spheres of Victorian society were imbalanced and limiting

    Kenyon Collegian - October 30, 1909

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    https://digital.kenyon.edu/collegian/2472/thumbnail.jp

    Information Infrastructures in Distributed Environments: Algorithms for Mobile Networks and Resource Allocation

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    A distributed system is a collection of computing entities that communicate with each other to solve some problem. Distributed systems impact almost every aspect of daily life (e.g., cellular networks and the Internet); however, it is hard to develop services on top of distributed systems due to the unreliable nature of computing entities and communication. As handheld devices with wireless communication capabilities become increasingly popular, the task of providing services becomes even more challenging since dynamics, such as mobility, may cause the network topology to change frequently. One way to ease this task is to develop collections of information infrastructures which can serve as building blocks to design more complicated services and can be analyzed independently. The first part of the dissertation considers the dining philosophers problem (a generalization of the mutual exclusion problem) in static networks. A solution to the dining philosophers problem can be utilized when there is a need to prevent multiple nodes from accessing some shared resource simultaneously. We present two algorithms that solve the dining philosophers problem. The first algorithm considers an asynchronous message-passing model while the second one considers an asynchronous shared-memory model. Both algorithms are crash fault-tolerant in the sense that a node crash only affects its local neighborhood in the network. We utilize failure detectors (system services that provide some information about crash failures in the system) to achieve such crash fault-tolerance. In addition to crash fault-tolerance, the first algorithm provides fairness in accessing shared resources and the second algorithm tolerates transient failures (unexpected corruptions to the system state). Considering the message-passing model, we also provide a reduction such that given a crash fault-tolerant solution to our dining philosophers problem, we implement the failure detector that we have utilized to solve our dining philosophers problem. This reduction serves as the first step towards identifying the minimum information regarding crash failures that is required to solve the dining philosophers problem at hand. In the second part of this dissertation, we present information infrastructures for mobile ad hoc networks. In particular, we present solutions to the following problems in mobile ad hoc environments: (1) maintaining neighbor knowledge, (2) neighbor detection, and (3) leader election. The solutions to (1) and (3) consider a system with perfectly synchronized clocks while the solution to (2) considers a system with bounded clock drift. Services such as neighbor detection and maintaining neighbor knowledge can serve as a building block for applications that require point-to-point communication. A solution to the leader election problem can be used whenever there is a need for a unique coordinator in the system to perform a special task

    More-than-humanizing the Anthropocene

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    The concept ‘human’ has to be more-than-humanized, a project Abram initiated but left incomplete in his study of language. Doing so is a powerful antidote to some of the more anthropocentric consequences of Anthropocenic thinking. Crucial to this project is uncovering the ways in which human agency is permeated by and circulates within vast causal relationships. Shifting from ecologically destructive patterns suggests completing this phenomenological project by uncovering the sense that the ‘human’ is in no simple sense, ‘steering this vessel.’ Not even the pervasive and perpetual arrogance about our own powers is incontrovertibly ‘our own.’ Humility and awe before these wild and undomesticatable processes cycling through us and carrying us in their currents can correct hubristic assumptions about our power for good or evil, and thereby also perhaps these destructive patterns

    Idle Talk, Deadly Talk

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    The first book-length study of gossip’s place in the literature of the multilingual Caribbean reveals gossip to be a utilitarian and deeply political practice—a means of staging the narrative tensions, and waging the narrative battles, that mark Caribbean politics and culture. Revising the overly gendered existing critical frame, Rodríguez Navas argues that gossip is a fundamentally adversarial practice that at once surveils identities and empowers writers to skirt sanitized, monolithic historical accounts by weaving alternative versions of their nations’ histories from this self-governing discursive material. Reading recent fiction from the Hispanic, Anglophone, and Francophone Caribbean and their diasporas, alongside poetry, song lyrics, journalism, memoirs, and political essays, Idle Talk, Deadly Talk maps gossip’s place in the Caribbean and reveals its rich possibilities as both literary theme and narrative device

    Idle Talk, Deadly Talk: The Uses of Gossip in Caribbean Literature

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    Chaucer called it spiritual manslaughter ; Barthes and Benjamin deemed it dangerous linguistic nihilism. But gossip-long derided and dismissed by writers and intellectuals-is far from frivolous. In Idle Talk, Deadly Talk, Ana RodrĂ­guez Navas reveals gossip to be an urgent, utilitarian, and deeply political practice-a means of staging the narrative tensions, and waging the narrative battles, that mark Caribbean politics and culture.From the calypso singer\u27s superficially innocent rhymes to the vicious slanders published in Trujillo-era gossip columns, words have been weapons, elevating one person or group at the expense of another. Revising the overly gendered existing critical frame, RodrĂ­guez Navas argues that gossip is a fundamentally adversarial practice. Just as whispers and hearsay corrosively define and surveil identities, they also empower writers to skirt sanitized, monolithic historical accounts by weaving alternative versions of their nations\u27 histories from this self-governing discursive material. Reading recent fiction from the Hispanic, Anglophone, and Francophone Caribbean and their diasporas, alongside poetry, song lyrics, journalism, memoirs, and political essays, Idle Talk, Deadly Talk maps gossip\u27s place in the Caribbean and reveals its rich possibilities as both literary theme and narrative device. As a means for mediating contested narratives, both public and private, gossip emerges as a vital resource for scholars and writers grappling with the region\u27s troubled history

    The Trail, 2013-11-22

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    https://soundideas.pugetsound.edu/thetrail_all/2993/thumbnail.jp
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