686 research outputs found
Fast Distributed Computation of Distances in Networks
This paper presents a distributed algorithm to simultaneously compute the
diameter, radius and node eccentricity in all nodes of a synchronous network.
Such topological information may be useful as input to configure other
algorithms. Previous approaches have been modular, progressing in sequential
phases using building blocks such as BFS tree construction, thus incurring
longer executions than strictly required. We present an algorithm that, by
timely propagation of available estimations, achieves a faster convergence to
the correct values. We show local criteria for detecting convergence in each
node. The algorithm avoids the creation of BFS trees and simply manipulates
sets of node ids and hop counts. For the worst scenario of variable start
times, each node i with eccentricity ecc(i) can compute: the node eccentricity
in diam(G)+ecc(i)+2 rounds; the diameter in 2*diam(G)+ecc(i)+2 rounds; and the
radius in diam(G)+ecc(i)+2*radius(G) rounds.Comment: 12 page
Dependability in Aggregation by Averaging
Aggregation is an important building block of modern distributed
applications, allowing the determination of meaningful properties (e.g. network
size, total storage capacity, average load, majorities, etc.) that are used to
direct the execution of the system. However, the majority of the existing
aggregation algorithms exhibit relevant dependability issues, when prospecting
their use in real application environments. In this paper, we reveal some
dependability issues of aggregation algorithms based on iterative averaging
techniques, giving some directions to solve them. This class of algorithms is
considered robust (when compared to common tree-based approaches), being
independent from the used routing topology and providing an aggregation result
at all nodes. However, their robustness is strongly challenged and their
correctness often compromised, when changing the assumptions of their working
environment to more realistic ones. The correctness of this class of algorithms
relies on the maintenance of a fundamental invariant, commonly designated as
"mass conservation". We will argue that this main invariant is often broken in
practical settings, and that additional mechanisms and modifications are
required to maintain it, incurring in some degradation of the algorithms
performance. In particular, we discuss the behavior of three representative
algorithms Push-Sum Protocol, Push-Pull Gossip protocol and Distributed Random
Grouping under asynchronous and faulty (with message loss and node crashes)
environments. More specifically, we propose and evaluate two new versions of
the Push-Pull Gossip protocol, which solve its message interleaving problem
(evidenced even in a synchronous operation mode).Comment: 14 pages. Presented in Inforum 200
La evolución del concepto de la Seguridad Humana: argumentos a favor y en contra acerca de las intervenciones humanitarias. Ilustración en el caso del campo de refugiados de Srebrenica en 1995
Esta disertación busca analizar y contrastar los argumentos sobre una posible intervención en el campo de refugiados de Srebrenica en 1995 bajo el concepto de Seguridad Humana.This dissertation seeks to analyze and contrast the arguments about a possible intervention in the refugee camp of Srebrenica in 1995. Human Security is the filter through which the analysis is done
Spectra: Robust Estimation of Distribution Functions in Networks
Distributed aggregation allows the derivation of a given global aggregate
property from many individual local values in nodes of an interconnected
network system. Simple aggregates such as minima/maxima, counts, sums and
averages have been thoroughly studied in the past and are important tools for
distributed algorithms and network coordination. Nonetheless, this kind of
aggregates may not be comprehensive enough to characterize biased data
distributions or when in presence of outliers, making the case for richer
estimates of the values on the network. This work presents Spectra, a
distributed algorithm for the estimation of distribution functions over large
scale networks. The estimate is available at all nodes and the technique
depicts important properties, namely: robust when exposed to high levels of
message loss, fast convergence speed and fine precision in the estimate. It can
also dynamically cope with changes of the sampled local property, not requiring
algorithm restarts, and is highly resilient to node churn. The proposed
approach is experimentally evaluated and contrasted to a competing state of the
art distribution aggregation technique.Comment: Full version of the paper published at 12th IFIP International
Conference on Distributed Applications and Interoperable Systems (DAIS),
Stockholm (Sweden), June 201
Why logical clocks are easy
Tracking causality should not be ignored. It is important in the design of many distributed algorithms. And not respecting causality can lead to strange behaviors for users. The most commonly used mechanisms for tracking causality, vector clocks and version vectors, are simply optimized representations of causal histories, which are easy to understand. By building on the notion of causal histories, users can begin to see the logic ehind these mechanisms, to identify how they differ, and even consider possible optimizations. When confronted with an unfamiliar causality tracking mechanism, or when trying to design a new system that requires it, readers should ask two simple questions, which events need tracking and how does the mechanism translate back to a simple causal history.We would like to thank Rodrigo Rodrigues, Marc Shapiro, Russell Brown, Sean Cribbs, and Justin Sheehy for their feedback. This work was partially supported by EU FP7 SyncFree project (609551) and FCT/MCT projects UID/CEC/04516/2013 and UID/EEA/50014/2013.info:eu-repo/semantics/publishedVersio
Matriz de seguimiento técnico aplicado al programa institucional de responsabilidad social “Yomasa”
Proyecto SocialEn este trabajo se realiza un análisis de información, y el diseño de una matriz de seguimiento técnico, de acciones del Programa Institucional de Responsabilidad Social Yomasa (en adelante PIRSY), que surge a partir de las necesidades del mismo, facilitando la consolidación de la información, para el seguimiento de metas y la toma de decisiones. Esta herramienta enriquece y aporta argumentos valiosos en pro de la mejora continua de la gestión del programa, mediante el seguimiento de los compromisos institucionales, facilitando el monitoreo de las metas y objetivos planteados.1. RESUMEN
2. ABSTRACT
3. MARCO TEÓRICO
4. METODOLOGÍA
5. DISCUSIÓN Y RESULTADOS
6. PROPUESTA
7. CONCLUSIONES
8. BIBLIOGRAFÍAPregradoEconomist
The dynamics of remembering and forgetting
[Excerpt] Human memory does not correspond to the objective recollection of events or the simple storage of a fixed past. It is a selective process of permanent interpretation and reconstruction as a function of a given context. The dynamics of remembering and forgetting are shaped by various personal, societal and cultural factors, and are subject to various ‘biases’. Our perception of people and events is shaped by an economy of attention in which certain aspects are noticed and others remain unnoticed, even when we strive to pay as much attention as possible
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