1,100 research outputs found
Lower bounds on systolic gossip
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)âO(loglog(n)) time steps, where λ is the unique solution between 0 and 1 of λ·pâs/2â(λ)·pâs/2â(λ)=1, with pi(λ)=1+λ2+âŻ+λ2iâ2 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 sââ 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
We consider a population of 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 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 -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
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 womenâs 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
https://digital.kenyon.edu/collegian/2472/thumbnail.jp
Information Infrastructures in Distributed Environments: Algorithms for Mobile Networks and Resource Allocation
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
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Knowledge underground : gossipy epistemology.
This dissertation is an attempt to loosen what I see as a chokehold by which two paramount assumptions constrict our epistemic endeavors. These Enlightenment assumptions--that we accept or refute ideas as true based on transparently clear and orderly methods and criteria, and that individuals accept or refute truth claims--are still central in epistemology, despite their many critics (for the first, Kant, Hegel, James, Quine, Bayes; for the second, postmodernism, Deleuze and Guattari, Gilbert). Thinking about gossip as an epistemologically productive concept provides us with the means to critique those assumptions, and further attempts to broaden our notion of an epistemological foundation. Gossip at first appears to be an unlikely candidate for such a resurrection, mainly because its treatment by academics has been dismissive; this dismissal is in part due to Enlightenment conceptions about truth and falsehood. Chapter One surveys the social science literature on gossip and rumor, revealing that social scientists begin with such restrictive definitions of what gossip is that their conclusions amount to little more than tautology. Chapter Two shows that humanists have a slightly different approach to gossip, but with roughly similar results. The handful of philosophers who deal directly with gossip or rumor almost as a unit accept uncritically a division between purposive conversation and idle chatter. To do so, I think, perpetuates a limiting epistemic foundation on a linguistic level. In contrast, I argue in Chapter Three that the very existence of something like gossip proves the inadequacy of the foundationalist myth (at least in its current form), and that to attempt to understand and use gossip with foundationalist tools is simply a wrong fit. My understanding of gossip is based on this central fact: we undertake the activity of gossip or rumor-spreading because we are trying to make sense out of something--we need to collect knowledge socially. Gossip originates from dissonance; it acts as a (necessary) counterweight to more official information, and can\u27t be considered apart from official knowledge. We use gossip and rumor, along with more orthodox sources of information, to formulate our understanding of ourselves and the world around us. The extent to which gossip and rumor are spread is the extent to which the analysis is shared, and not individualized. Gossip is both a genealogical tool and an speculative tool
More-than-humanizing the Anthropocene
The concept âhumanâ 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 âhumanâ is in no simple sense, âsteering this vessel.â Not even the pervasive and perpetual arrogance about our own powers is incontrovertibly âour own.â 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
The first book-length study of gossipâs place in the literature of the multilingual Caribbean reveals gossip to be a utilitarian and deeply political practiceâa means of staging the narrative tensions, and waging the narrative battles, that mark Caribbean politics and culture. Revising the overly gendered existing critical frame, RodrĂguez 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 nationsâ 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 gossipâs 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
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
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